GSI Design Requirements and Guidelines Packet
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GREEN STORMWATER INFRASTRUCTURE DESIGN REQUIREMENTS AND GUIDELINES PACKET Last Updated: May 15, 2015 GSI Design Requirements and Guidelines Document Format This document contains design requirements and guidelines derived from both existing PWD policies and past experience. They are presented in the following categories: I. Introduction ........................................................................................................................................ 6 II. System Sizing ..................................................................................................................................... 10 III. Infiltration & Detention/Slow‐Release .............................................................................................. 11 IV. SMP Selection .................................................................................................................................... 13 V. System Location ................................................................................................................................ 14 VI. Inlet Capacity ..................................................................................................................................... 15 VII. Inlet Selection and Replacement ...................................................................................................... 15 VIII. Maintenance & Monitoring .............................................................................................................. 16 IX. Trees and Plants ................................................................................................................................ 17 X. Design Report .................................................................................................................................... 18 Attachments The following attachments are included at the end of this document. They are resources that are used during the design process: Attachment A: Submission Completeness Requirements .......................................................................... 20 Attachment B: Final Design Package Checklist ........................................................................................... 22 Attachment C: Green Stormwater Infrastructure Review Contacts ........................................................... 24 Attachment D: Partner Project Review Guidelines ..................................................................................... 29 Attachment E: Survey Guidelines ............................................................................................................... 30 Attachment F: Geotechnical Testing Guidelines ......................................................................................... 37 Attachment G: Final Design Metrics Report ............................................................................................... 49 Attachment H: City of Philadelphia – Street Tree Guidelines ..................................................................... 62 Attachment I: Philadelphia Parks & Recreation Street Tree Review .......................................................... 64 2 GSI Design Requirements and Guidelines Revision History This document is continuously evolving, so users should consistently make sure they are using the latest version by checking with the assigned PWD project engineer. Revisions to this document are recorded here: Effective Date Description of Revision 3/26/13 General clarifying language Added language stating that PWD project manager can provide guidance on applicable reference materials and whether inlet replacement requires a new sewer connection. Reformatted section II (System Sizing). Added guideline III.B.1: “Infiltration is a priority. Wherever possible, systems should be designed for infiltration.” Added the following guidance for utility offsets to IV.4: “A minimum of 6‐18 inches vertical distance from existing utility lines, depending on the utility type, age, and condition.” Modified guideline IV.6 to state: “Minimum cover over storm sewer pipes in ROW or vehicular path should be 2 feet, unless other design is approved by PWD project manager.” Made major modifications and additions to section VII and changed its name from Maintenance to Maintenance/Monitoring. Deleted the Miscellaneous section heading and moved its content to other sections. Added language to VIII.B.8 on how to denote an inlet reconnection Added requirements 5, 10, and 13‐15 to section VIII.B, concerning labeling and naming of SMP components. Added guideline VIII.B.13: “Inlets that include water quality inserts should be labeled as such in plan view.” In section IX, removed requirement for larger caliper trees around schools. Added guideline IX.B.4: “Container plants are preferred over plugs in most instances.” Added language stating that the GSI Plant list should be followed dominantly for all landscape plans, and exclusively for projects on PP&R property. Added interpretation of geotechnical testing results to 30% design submission and the option for an intermediate review for complex projects before 70% to Attachment A. Added “drainage area maps in PDF and CAD format” to 100% submission in attachments A and B. Made updates to Attachment C to match updates to the design process. Added the following to Attachment D: PWD Construction Unit, Streets Department’s City Plans Unit, contact information for PP&R for park projects, PennDOT submission requirements, and a note stating that turning analyses should be submitted to street department if curbline changes are proposed. General clarifications and removal of superfluous language Added a note to Section I on requirements for GSI in separate sewered areas. Modified II.1 to state: “All systems should provide static storage for a target of 1.5” of runoff from the contributing impervious drainage area. Systems must, at minimum, provide static storage for 1” of runoff and should typically not exceed a volume equivalent to 2” of runoff, unless otherwise approved by PWD.” 10/22/13 Added requirements II.7, 8, and 9, concerning safe conveyance of large storms, drain down time, and erosion control. Added geotechnical testing guidelines (III.A) Added requirement for detention/slow‐release projects that runoff must go through pollutant reducing SMP, III.D.3. Added the following sentence to III.C.5: “PWD project manager must acknowledge that infiltration is inadvisable before a project proceeds with design of a lined slow‐release system.” SMP Selection section, with guidance on maximizing triple bottom line benefits through selection of GSI systems, added as section IV. Numbering changed accordingly for all subsequent sections. Removed V.3.a concerning eight‐foot distance from buildings. Changed the minimum vertical distance from existing utility lines from 6 inches to 12 inches in V.4.b. V.8 divided into two separate guidelines. Added the following to V.9: “Where shoring appears to 3 GSI Design Requirements and Guidelines 5/15/15 be necessary, the PWD Project Manager should be consulted to determine if design of this SMP is worth the potential added cost and complexity.” Replaced VI.1 and 2, updating requirements for inlet capacity and safe conveyance of large storms. Added VIII.12.a: “The flushing point should preferably be a green inlet.” Removed Drawing Requirements section. This information is being transferred to the GSI Drawing Requirements Packet. Modified IX.3 to specify 2.5 to 3 inch caliper trees. Added IX.4 and 5, concerning maximization of space for tree plantings. Added IX.8, prohibiting the use of seed mixes in SMP footprint. Significant additions made to section X (Design Report) to reflect details concerning the new GreenIT Data Entry Application, required calculations, and drainage area map requirements. Renamed all submission intervals to be more representative of what the submission is: 30% ‐>Baseplan/Concept Check 70% ‐> Substantially Complete Design 90% ‐>Plans, Specs, and Estimate (PS&E) 100% ‐> Final Modified attachments A (Submission Completeness Requirements) and B (Final Design Package checklist) to reflect changes to submission requirements. PS&E milestone moved forward a month to when first submission is made to PWD after utility submission. Change reflected in the Typical GSI Design Timeline (Attachment C). Review contacts table in Attachment D updated with details on which utilities/agencies require approval in order to move forward with design. PWD Construction Unit removed as a reviewing agency because this review will be handled internally by PWD. Geotechnical Testing Guidelines in Attachment E revised significantly. GSI plants list updated and details on plant selection added to Attachment G. General clarifications and formatting updates throughout Added Relationships with Other Resources and References to the Introduction I.A Increased target storm size managed to 2 inches, II.1 Clarified that contributing drainage area is directly connected, II.1 Added guideline to include sand layer and tree pit soil in storage volume calculations, II.4. Increased allowable depth of soil storage from 24 inches to 3 feet, II.4 Added requirement that geotechnical reports be stamped and signed by Pennsylvania State Licensed Professional Engineer, III.A Updated underdrain guideline to include exceptions where inclusion of an underdrain or an underdrain connection may not be necessary, III.B.1 Revised loading ratio guideline to differentiate between subsurface, surface, and total drainage area loading ratios, III.C.4 Added exception that impermeable liners may not be required around infiltrating systems in the zone of influence of concrete sewers in good condition, III.C.6 Added guideline to use a sand layer below stone instead of geotextile and to tuck geotextile between stone and sand, III.C.8 Changed orifice minimum diameter to a guideline, III.D.4 Added requirement to use 0.62 as the discharge coefficient in slow‐release orifice calculations, III.D.6 Updated SMP preferences to focus on system function and maximize surface flow into vegetated features, IV.B Updated System Location V to include requirements for off‐street projects Updated system location guidelines to include exceptions where systems may not be located near existing inlets or drainage structures, V.1 Relaxed guidelines about offsets to existing utilities, poles, and other infrastructure to evaluation of potential costs and GA benefit of impacts, V Updated inlet capacity calculations to use a 0.25 clogging factor of safety for curb cut inlets and a 0.5 clogging factor of safety for grated inlets, VI.3 Inlet capacity guidelines should comply with Federal Highway Administration requirements, VI.4 Updated inlet guidelines to recommend curb cuts into vegetated features and to include PennDOT inlets in the list of preferable inlet types, VII.A Removed requirement to slope distribution pipes from VIII Removed guideline that distribution pipes should run the length of any subsurface system and added guideline to minimize piping where possible from VIII 4 GSI Design Requirements and Guidelines Added requirement to include additional observation wells for systems longer than 100 LF in any direction, VIII.5 Added recommendation for area protection, fencing for sites with foot traffic or pedestrian movement, VIII.18 Added recommendation to include traffic delineators on stormwater bumpouts, VIII.19 Added guideline to consider outfall protection/screening for pipes with large openings, VIII.20 Removed GSI Plant Species list (former Attachment) and replaced with reference to GSI Design Landscape Design Guidebook, IX Removed guideline that prohibited seed mixes within SMP footprints, IX Added requirement to include PDFs of all PA One Call plans received during survey to Attachment A Baseplan Submission Requirements Removed Typical GSI Design Timeline previous Attachment to eliminate redundancies with the GSI Design Process Workflow Packet Updated review contacts and added additional review contacts including ADA ramp review, Stormwater Plan Review (private regulations), and PADEP NPDES review contacts, Attachment C Differentiated Streets Department review requirements depending on whether a project includes curb‐line changes or not, Attachment C Revised PWD Collectors Systems and GSIMN review requirements so that they are coordinated internally by PWD, Attachment C Added Partner Project Review Guidelines Attachment, a simple flow‐chart to determine if the technical and review requirements for partner projects that might trigger the Philadelphia stormwater regulations for private redevelopment, Attachment D Added Survey Requirements Attachment specifying on‐street, off‐street, and drainage area survey requirements for all projects, Attachment E Revised geotechnical testing requirements to include three different methods of borehole testing methods, Attachment F Added new SMP types and infiltration test types to the metrics reporting, Attachment G Revised new pervious and vegetated area fields to be total pervious and total vegetated area in final metrics report, Attachment G Added Credited Green Acre field and Credited Storm Size Managed field to final metrics report, Attachment G Consolidated Street Tree review guidelines and example plan into one Attachment, Attachment I 5 GSI Design Requirements and Guidelines I. Introduction As part of the Green City, Clean Waters Program for Combined Sewer Overflow Control, the City of Philadelphia relies on Green Stormwater Infrastructure (GSI) systems – comprised of one or more decentralized stormwater management practices (SMPs) such as rain gardens, stormwater tree trenches, and green roofs – to reduce stormwater volume and pollutants delivered to the City’s combined sewer system. GSI manages stormwater using the source control processes of infiltration, evaporation, transpiration, decentralized storage, alternative stormwater routing, and reuse, among others. Systems are generally composed of some combination of vegetation, surface storage, and subsurface storage. This packet provides requirements and guidelines to be used in the design of all GSI projects funded and/or maintained by the Philadelphia Water Department (PWD). The following information is to be used throughout the design process by PWD staff, providers of professional engineering services hired by PWD, and other agencies/partner organizations that are working with PWD. The design requirements and guidelines are derived from existing PWD policies and past experience. This packet contains “requirements”, which must be followed, and “guidelines”, which are generally followed but contain exceptions. Requirements are indicated by the words “must” and “will”, while guidelines use words such as “can” and “should”. Guidelines will still generally be followed and can be enforced strictly by PWD. There may be additional limitations beyond those mentioned below. Some constraints may be modified in certain circumstances, at the direction of the PWD project manager. Note on Professional Judgment: This packet is not intended as a substitute for the judgment of engineering and design professionals, nor should it be used as such. Professional judgment should be used in addition to this packet. It remains the sole responsibility of engineering and design professionals to develop plans which are consistent with all laws and regulations and which are based on sound engineering judgment. Any time professional judgment differs from the guidance/requirements outlined in this packet, the concern should be discussed with PWD. Compliance with the guidelines contained in this packet does not assure design acceptance by PWD. Note on Separate Sewered Areas: The guidelines presented herein are intended for projects within areas of Philadelphia served by combined sewer systems. GSI projects within separate sewered areas must generally comply with all requirements of this packet and, in addition, must meet the volume reducing requirements outlined in the Philadelphia Stormwater Management Guidance Manual: The water quality volume must be routed through a SMP that provides volume reduction, flow attenuation, and water quality treatment. See Table 4.3 from Philadelphia Stormwater Management Guidance Manual for Acceptable Volume Reducing Stormwater Management Practices. More specific requirements, or deviations from these requirements, will be provided by the PWD project manager at the time of project initiation. 6 GSI Design Requirements and Guidelines A. Relationships with Other Resources and References The publication of the PWD GSI Design Requirements & Guidelines Packet follows a number of related resources. These related resources should be used by the designer for reference and additional contextual information. Always refer to the most current resources. Note on Other “Packets”: The PWD GSI Design Requirements & Guidelines Packet is one of three main “Packets” that describe the requirements for GSI projects funded and/or maintained by PWD: the GSI Design Process Workflow Packet, the GSI Design Requirements & Guidelines Packet, and the GSI Drawing Requirements Packet. 1. Philadelphia Water Department. 2015. Green Stormwater Infrastructure Design Process Workflow Packet. This document provides summary workflows, detailed workflows, and expanded process descriptions that describe the process for GSI projects funded and/or maintained by PWD. The workflows are to be referenced by PWD staff, providers of professional engineering services hired by PWD, and other agencies and partner organizations. http://phillywatersheds.org/doc/GSI/GSI_Design_Process_Workflow_Packet_5‐ 15‐2015.pdf 2. Philadelphia Water Department. 2013. Green Stormwater Infrastructure Drawing Requirements Packet and the OOW GSI CAD Standards. This packet provides requirements to be used in the drawing of GSI projects funded and/or maintained by PWD. The Office of Watersheds (OOW) has also developed a GSI CAD Standard that includes all necessary files for drawing to these PWD GSI standards. http://phillywatersheds.org/doc/GSI/GSI_Drawing_Requirements_10‐21‐ 2013.pdf http://phillywatersheds.org/doc/GSI/GSI_CAD_Standards_10‐7‐13.zip 3. Philadelphia Water Department. 2014. Water & Sewer Design Manual. This manual promotes uniformity in the presentation of water and sewer plans by establishing a general format and outlining detailed information required for the preparation of complete water and sewer contract drawings. The PWD Water & Sewer Design Manual includes detailed information about standards for water and sewer design in Philadelphia. http://www.phillywaterdesign.org/ 7 GSI Design Requirements and Guidelines 4. Philadelphia Water Department. 2014. Green Stormwater Infrastructure Landscape Design Guidebook. This resource provides guidance and plant selection lists for design professionals to complete successful landscape designs for GSI projects. It is a synthesis of knowledge from PWD’s experience implementing GSI, partner preferences, current research, and municipal guides for other communities. This guide must be used when developing landscaping plans. http://phillywatersheds.org/doc/Landscape_Manual_2014.pdf 5. Philadelphia Water Department. 2014. Green Stormwater Infrastructure Maintenance Manual. This manual details PWD’s standard operating procedures for executing specific maintenance tasks such as vegetation removal, sediment removal, and trash removal. Maintenance requirements are outlined for the various SMP types in use by PWD. Protocols for surface and subsurface activities include details on required training, materials, health and safety, and task execution for each maintenance activity. http://phillywatersheds.org/doc/GSIMaintenanceManual‐ 1stEdwpreamble_LRes.pdf 6. Philadelphia Water Department. 2014. Green City, Clean Waters Comprehensive Monitoring Plan. This plan outlines the strategy for ongoing monitoring of PWD’s GSI systems. Monitoring data and modeling are used to verify the functions and conditions of PWD’s GSI controls, the sewer system, and the receiving waters and provide information for inclusion in hydrologic, hydraulic, and water quality models used to determine combined sewer overflow volume reduction effectiveness and improvements in area water quality conditions from the Green City, Clean Waters program. http://www.phillywatersheds.org/doc/Revised_CMP_1_10_2014_Finalv2.pdf 7. Philadelphia Water Department, Philadelphia Streets Department, and Mayor’s Office of Transportation and Utilities. 2014. City of Philadelphia Green Streets Design Manual. This manual, known as the GSDM, provides guidance for public and private entities, specifically design professionals, interested in incorporating GSI within a given right‐of‐way. The GSDM provides applicable users (those designing right‐of‐way GSI projects not initiated by PWD) with design standards, guidance on siting, information on elemental flexibility within SMPs, and an implementation process to guide users through the planning, design and construction of a green street. The GSDM follows and complements the Complete Streets Design Handbook. http://www.phillywatersheds.org/gsdm 8 GSI Design Requirements and Guidelines 8. Mayor’s Office of Transportation and Utilities. 2012. The Philadelphia Complete Streets Design Handbook. This handbook was developed to support Mayor Michael Nutter’s 2009 Executive Order that the City’s streets accommodate “all users of the transportation system – be they pedestrians, bicyclist, public transit users, or motor vehicle drivers.” The GSDM follows and complements the Complete Streets Design Handbook. http://www.philadelphiastreets.com/complete‐streets‐handbook 9. Philadelphia Water Department. 2011. Stormwater Management Guidance Manual. This manual was created to assist developers in meeting the requirements of the Philadelphia Stormwater Regulations. The manual provides guidance for the entire site design process, beginning with initial site design considerations, through the post‐construction stormwater management plan submittal elements, and ultimately the acquisition of stormwater plan approval. http://www.pwdplanreview.org/StormwaterManual.aspx Note on Partner Projects: The guidelines provided within this packet differ in many ways from the requirements in the Philadelphia Stormwater Management Guidance Manual. When certain information is not covered in the Design Requirements & Guidelines Packet, the design guidance in the Stormwater Management Guidance Manual may be helpful. However, it should be noted that the Stormwater Management Guidance Manual strictly contains requirements for private development, not public implementation of GSI, and any use of the manual should be brought to the attention of the PWD project manager. Attachment D: Partner Project Review Guidelines provides a simplified flowchart for determining whether partner projects will need to meet both public and private requirements. The PWD project manager can provide further guidance on what reference materials apply to a particular project. 10. Pennsylvania Department of Environmental Protection (PADEP). 2005. Pennsylvania Stormwater Best Management Practices Manual. This manual provides general guidance from the PADEP on stormwater management for land development processes. The manual is intended to be a tool to achieve a regulatory standard to protect, maintain and improve the Commonwealth’s water resources through comprehensive site planning and design guidance. http://www.elibrary.dep.state.pa.us/dsweb/View/Collection‐8305 9 GSI Design Requirements and Guidelines II. System Sizing The primary reporting metric of PWD GSI is the Greened Acre. A Greened Acre (GA) is an expression of the volume of stormwater, in acre‐inches, managed by GSI. It is calculated using the following equation: GA = IC * Wd Where: IC (acres) is the impervious cover (formerly tributary to the combined sewer system) utilizing green stormwater infrastructure. This quantity can include the area of the stormwater management feature itself, as well as the area that drains to it. Wd (inches) is the depth of water over the IC that can be physically managed in the facility. Systems must be properly sized to manage the specified Greened Acre volume. The following information must be used when sizing a GSI system: 1. All systems should provide static storage for a target of two (2.0) inches of runoff from the existing directly connected, contributing impervious drainage area. Systems must, at minimum, provide static storage for one (1) inch of runoff and should typically not exceed a volume equivalent to two (2) inches of runoff, unless otherwise approved by PWD. 2. Under current policy, only drainage areas in the right‐of‐way or on public lands should be counted for sizing considerations. 3. Within the right‐of‐way, grass strips or other highly compacted areas should be considered impervious unless modified with soil improvements as part of the proposed work. 4. When calculating storage, the following void percentages should be used: a. A void space of 40% for open graded aggregate (frequently referred to as “stone”). b. A void space of 20% for soil storage. i. Soil storage up to a depth of three (3) feet can be counted in surface systems, such as bump‐outs and planters. ii. Soil within a tree pit may be considered storage. c. A void space of 30% for sand. d. Pipes embedded in systems provide 92% void space. Assumes outer diameter of pipe. e. Modular storage products should use the product‐specific void space. 5. Storage provided above the elevation of the overflow cannot be included. Storage below the orifice cannot be counted for detention/slow‐release systems. However, this volume below the orifice or invert of the underdrain will be tracked for all systems (detention/slow‐release and infiltration). 6. Where a series of systems are used, larger downstream systems that capture overflow/bypass from undersized upstream systems can be used to meet full storage requirements, assuming inlet capacity is sufficient. However, oversized upstream systems cannot be used to offset undersized downstream systems. The cumulative capabilities of the system must manage the minimum one (1) inch storm for the directly connected, contributing impervious drainage areas. 7. All systems must safely convey runoff from the 10‐year design storm. 8. Systems must be designed to drain down within 72 hours. For surface features, it is recommended that ponding areas drain down in less than 24 hours. 9. Systems must be designed to not create any erosive conditions, either internal to the system or at any outfall location. 10. Separate storage calculations should be completed for each individual system as per design report requirements. Refer to Section X of this document for the design report requirements. 10 GSI Design Requirements and Guidelines III. Infiltration & Detention/Slow-Release While infiltration systems are preferred, some systems are designed as detention/slow‐release based on the results of geotechnical testing or other factors. The following information guides the decision of whether to design for infiltration or detention/slow‐release and lists requirements for these scenarios. A. Geotechnical Testing 1. Soil and infiltration testing must be completed for all proposed GSI systems. See Attachment F: Geotechnical Testing Guidelines for details on geotechnical tests and methods. 2. A minimum of one (1) infiltration test and one (1) deep boring must be taken within the footprint of each proposed SMP. 3. For larger GSI systems, additional infiltration tests are required so that any part of the SMP footprint is within a 50 foot radius of at least one test location. 4. The preferred method for infiltration testing is the double ring infiltrometer test. It is anticipated that these tests would primarily be used for unpaved and open excavation areas, where surface disturbance would not be problematic. However, double ring infiltrometer testing should be evaluated for all sites. 5. In paved areas or other areas where surface disturbance during testing should be minimized, infiltration testing in boreholes, in accordance with Attachment F, is acceptable. 6. A detailed layout of proposed boring locations and infiltration testing sites must be submitted to PWD and approved prior to any field activities. 7. Results from geotechnical investigations are to be documented in a geotechnical report, stamped and signed by a PA State Licensed Professional Engineer, and submitted to PWD. B. Underdrains 1. Regardless of whether a system is designed for infiltration or for detention/slow‐release, underdrains should typically be installed in all systems. This allows for conversion to a detention/slow‐release system if the system fails to infiltrate due to clogging. a. Exception: For system locations with adequate infiltration rates where convenient underdrain connections are not available, an underdrain may not be required at the approval of the PWD project manager. 2. Underdrains should extend inside the system for a minimum length of 20 feet where possible, unless modeling shows a shorter length to be adequate. 3. Underdrain pipe should be eight (8) inches in diameter and perforated. 4. Underdrains should connect to the adjacent existing inlet or a sewer connected control structure. The underdrain should terminate either in a solid cap or orifice depending on whether the system is designed for infiltration or detention/slow‐release. a. If it is not possible or advisable to connect the underdrain to an adjacent existing inlet, then the underdrain must extend for a minimum of five (5) feet outside of the system and be capped. This will allow for future access to the underdrain without disruption of the system should the system need to be converted to detention/slow‐release. 5. For off‐street projects, the condition and capacity of the existing drainage structures (inlets and pipes) must be evaluated when considering whether to reuse as overflow structures. C. Infiltration Systems 1. Infiltration is preferable to other hydrologic operations. Wherever possible, systems should be designed to infiltrate stormwater. 11 GSI Design Requirements and Guidelines 2. If measured infiltration rates are found to be greater than or equal to 0.25 inches per hour and the system is able to completely drain in 72 hours, then the system should be designed for infiltration. a. Where measured infiltration rates are less than 0.25 inches per hour, but auger borings show layers of greater permeability beneath the impermeable layer, infiltration column SMPs should be included to promote infiltration. 3. Soils with infiltration rates in excess of 10 inches per hour require soil amendments. 4. Infiltration loading ratios (drainage area to infiltration area) should be minimized as feasible. a. For subsurface systems, a maximum loading ratio for connected impervious area of 10:1 should be targeted. b. For surface systems, a maximum loading ratio for connected impervious area of 25:1 should be targeted. c. Loading ratios for the total contributing drainage area, which includes pervious and impervious contributing areas, should generally stay under 25:1 with site specific conditions considered. d. These loading ratio maximums are guidance for stabilized drainage areas; designs should consider if the ground cover in the drainage area is unstable. e. Higher loading ratios may be evaluated on a case by case basis in consideration of the geotechnical conditions found and at the approval of the PWD project manager. 5. Typically at least 10 feet of separation should be maintained between infiltrating systems and buildings or structures. If a system is located closer than 10 feet to a building, the bottom and sides of the system should be lined with an impermeable liner to a minimum distance of 10 feet from the building. 6. Infiltration systems should not infiltrate within the zone of influence of any nearby sewers or sewer laterals. a. If the system is within the area defined by a 1:1 slope line extending from the bottom of the sewer cradle to the top of the provided storage, then the part of the system storage in that area should be wrapped with an impermeable liner. b. Exception: Impermeable liners may not be necessary for proximity to concrete sewers in good condition. The PWD project manager can provide this guidance. 7. The bottom elevation of an infiltrating system must be a minimum of two (2) feet above any infiltration‐limiting layer, such as bedrock or seasonal high groundwater. See PA BMP Manual Appendix C, Protocol 2.1 for more information. 8. A six (6) inch sand layer is generally preferred as media separation between the bottom of stone storage and the subgrade, except for pervious paving designs. Geotextile should be used along the sides and top of the system and tucked six (6) inches under the bottom of the sand layer. D. Detention/Slow Release Systems 1. If design infiltration rates are found to be less than 0.25 inches per hour, or if the system is not able to completely drain in 72 hours, the system should be designed for detention/slow‐release. a. Systems should be lined and designed for detention/slow‐release if geotechnical or contamination issues make infiltration inadvisable. Geotechnical issues include, but are not limited to, environmental contamination and/or the presence of limiting zones within the stratigraphic profile. PWD project manager must approve design of a lined detention/slow‐release system. 2. Detention/slow‐release systems must be designed to release at a maximum rate of 0.05 cfs per acre of contributing impervious drainage area. 12 GSI Design Requirements and Guidelines 3. Detention/slow‐release systems must route ground‐level runoff through a PWD‐approved pollutant reducing SMP. Pollutant reducing SMPs include basins, planters, rain gardens, bumpouts, green gutters, stormwater trees or other SMPs that route runoff through a soil profile or other equivalent porous media. 4. Orifice diameters should not be less than 0.5 inches. 5. For constructability, orifices must be sized for common drill bits (must be a multiple of 1/8 inch). 6. An orifice equation discharge coefficient of 0.62 must be assumed. IV. SMP Selection In line with the goals of the Green City, Clean Waters program, SMP selection should maximize triple bottom line benefits and the water quality benefits of filtering stormwater runoff through soil profiles. A. General Principles 1. Surface features are preferred to sub‐surface features. 2. Vegetated features are preferred to non‐vegetated features. 3. Tree planting and vegetated surface area should be maximized to the greatest extent feasible. In the Green City, Clean Waters Program Long Term Control Plan Update, the triple bottom line benefits associated with GSI are outlined as: Economic Benefits GSI jobs reduce the social cost of poverty. Social Benefits GSI enhances recreation. GSI improves community quality of life. GSI reduces effects of excessive heat. Environmental Benefits GSI improves air quality. GSI saves energy and offsets climate change. GSI restores ecosystems. B. SMP Preference Designers should maximize the triple bottom line benefits by careful selection of SMP types. The following shows the preferred SMP functions in descending order. The hierarchy presented is a generalized list and doesn’t take into consideration site specific constraints that might otherwise preclude certain SMP types. 1 Surface Inflow into Vegetated Systems with Woody Vegetation (Maximizes surface features & vegetation) 2 Surface Inflow into Vegetated Systems with Herbaceous Vegetation (Smaller surface features and vegetation footprint) 3 Subsurface Inflow with Pretreatment and Vegetation (No surface feature or vegetation footprint, but maximizes tree planting) 4 Systems with No Vegetation (No surface feature or vegetation footprint, additional tree planting recommended) 13 GSI Design Requirements and Guidelines V. System Location 1. Systems should generally be located directly upstream from existing inlets whenever possible in order to maximize drainage areas and allow for a convenient underdrain connection to an existing inlet. a. Exception: Some locations may be acceptable for systems where convenient underdrain connections are not available. b. Exception: Steep street approaches may require tiered systems located further upstream from the existing inlet. 2. Projects should evaluate the potential costs and greened acre benefit when determining whether to impact existing utilities, poles, and lights. If a project is designed with the intention to not impact this infrastructure, the following guidance is suggested: a. A three (3) foot horizontal distance from existing utility lines should be maintained. b. A minimum of 12‐18 inches vertical distance from existing utility lines should be maintained, depending on the utility type, age, and condition. c. A five (5) foot distance from telephone poles or other comparable existing infrastructure should be maintained, unless deemed otherwise feasible. Such poles must be called out to be supported and protected during construction. d. A three (3) foot distance from traffic lights must be maintained. 3. Designs should consider minimum and maximum depths of excavation due to surface elevation changes over the length of systems. Projects should evaluate the potential costs and greened acre benefit when determining whether to design systems that would require sheathing and shoring. A tiered approach may also be considered to reduce excavation. 4. Existing trees in good condition are to be preserved wherever possible, particularly mature trees of desirable species located on off‐street properties. Designs should consider the relative benefits of new GSI in comparison to existing tree preservation. When minimizing impact to existing trees, designs should take into account the most up‐to‐date guidance on excavation around and within tree driplines. The PWD project manager can provide this guidance. 5. Anti‐seep collars must be included at any point where a pipe penetrates into GSI storage media. This includes penetrations for utility crossings, distribution pipes, and underdrain pipes. 6. Minimum cover over pipes in the right‐of‐way or in vehicular paths should be two (2) feet, unless alternative design is approved by the PWD project manager. 7. In order to protect right‐of‐way (Green Street) systems from future construction on adjacent parcels, a minimum of a three (3) foot buffer must be maintained from the right‐of‐way line. a. Exception: Closer offsets are permitted from the right‐of‐way line if the adjacent parcel is a City‐owned property. 8. In order to protect off‐street (Green Park, Green Schools, etc.) systems from future construction on adjacent parcels, a minimum of a five (5) foot buffer must be maintained from the adjacent property lines, though 10 feet is preferred. 9. Off‐street projects should consider the diversion of flows from one sewershed to another. 10. If a surface SMP is located within a school yard, recreation space, or on a slope, then area protection, such as a shrub border or protective fencing, should be included around the perimeter or accessible side of the SMP. 11. Gradual side slopes of 5:1 for graded surface SMPs are preferred where feasible. A maximum side slope of 2:1 must not be exceeded. 12. For projects in high‐trafficked areas, such as streets locations, on School District of Philadelphia or on Philadelphia Parks & Recreation property, ponding depths for surface SMPs should generally not exceed six (6) inches. 14 GSI Design Requirements and Guidelines VI. Inlet Capacity Drainage area, defined as the measure of surface area upon which runoff converges to a single low point, must be determined for each inlet and system. Separate capacity calculations should be completed for each individual routing component. 1. Required inlet capacity must be designed using the Rational Method, which utilizes the following equation: Q=CiA Where: Q= Peak runoff rate (cfs) C= Runoff Coefficient I= Average rainfall intensity (in/hr) A= Drainage Area (acres) 2. The average peak 15 minute intensity from the 24 rain gage network in Philadelphia is 2.5 inches per hour. 3. Inlets must consider a clogging factor of safety to determine interception capacity and ensure capturing the design intensity. a. Grated inlets must utilize a clogging factor of safety of 0.5 (assuming only half of the opening is available for conveyance of stormwater to the GSI practice). b. Curb opening inlets must utilize a clogging factor of safety of 0.25. c. The factors must be applied to the unclogged interception capacity of the inlet and the resulting clogged interception capacity compared to the design intensity flow rate. 4. Curb cuts should be designed following the methods described in the Federal Highway Administration Urban Drainage Design Manual. 5. See requirement II.7 (All systems must safely convey runoff from the 10‐year design storm). This conveyance can include bypass as long as the runoff can be safely treated downstream. VII. Inlet Selection and Replacement The following guidelines must be used to determine inlet selection and replacement: A. Inlet Selection 1. Curb cuts to surface features are preferred to maximize the water quality benefits of filtering runoff through a soil profile. 2. PWD or PennDOT standard 4‐foot highway grate inlets are preferred where inlet boxes are required. If utility conflicts are present, PWD or PennDOT Standard 4‐foot city inlets should be used. 3. All non‐green inlets (inlets that connect directly to the sewer system) for right‐of‐way (Green Streets) systems should be PWD Standard 4‐foot open mouth grate inlets, unless there are conflicts with utilities or ADA ramp design. If utility conflicts are present, PWD Standard 4‐foot city inlets should be used. At corner apexes, if it is found that an open mouth grate prohibits the design and construction of ADA compliant handicap ramps, then a highway grate inlet may be used. See the PWD Water & Sewer Design Manual. 4. For non‐street applications or surface systems, other inlet selection may be considered at the advisement of the PWD project manager. 15 GSI Design Requirements and Guidelines B. Inlet Replacement Special Requirements for Green Streets Projects 1. If, in the Green Stormwater Infrastructure work, underdrain connections are not being made to the existing inlet and the surrounding footway/paving is not being replaced, inlets may not need to be replaced. 2. Appropriate offsets should be maintained from the existing inlet if inlet will not be replaced; five (5) feet is recommended. 3. If underdrain connections to the existing inlet are being made, or work is being conducted in the vicinity of an existing inlet, the considerations below must be used to determine if the existing inlet should be replaced. a. Any city or grate inlets with old‐style cast‐iron grates or tops must be replaced. These older inlets are denoted by #1, #2, #3, or #4 City or “Grate”. Details can be found in the Standard Details for Sewers (1907), which is enclosed in the latest version of the Water & Sewer Design Manual. b. Any inlet that has a brick inlet box must be replaced, regardless of inlet top (that is, if a new inlet top has been grafted onto an old inlet box). Type of inlet box is determined during design by visual inspection. c. Any inlet that is damaged or otherwise unsatisfactory must be replaced. d. Any inlet that is non‐standard, (PennDOT style, modified PWD designs, 6‐footers, etc.), should be considered for replacement. e. Any inlet that has a history of problems as found in the inlet history report should be considered for replacement. PWD project manager can provide inlet history report. f. Any city inlet installed on the radius of a corner should be considered for replacement regardless of age or condition. g. Any inlet that is of the three 'new' PWD standard types (concrete slab city, 4‐foot highway grate, 4‐foot open mouth grate with precast top) with a concrete inlet box, in good condition, and appropriately located in the right‐of‐way should not need to be replaced. 4. If inlet replacement is required, the PWD project manager can provide guidance on whether designs should propose new sewer connections or reconnections to existing lateral. VIII. Maintenance & Monitoring 1. Maintenance access should be considered early on in the design process and must be reviewed and approved by PWD. a. New prototypes, irregular systems, materials, or devices proposed will require additional review during the conceptual design phases. 2. The number of individual systems should be minimized in order to reduce future maintenance requirements. 3. Vehicular access for trucks and entry permissions (easements) must be provided for off‐street sites. PWD project manager will coordinate the acquisition of appropriate easements. 4. Cleanouts, observation wells, and/or groundwater wells should not be located in driveways. If possible, avoid placing cleanouts and observation wells in the cartway as well. 5. For larger GSI systems, additional observation wells are required so that any part of the system footprint is within a 100 foot radius of at least one observation well. 6. Observation wells should be placed in the center of the SMP. Cases with multiple wells should have well locations with equal spacing throughout the SMP. 7. PWD standard materials are preferred. 16 GSI Design Requirements and Guidelines 8. Distribution, underdrain, and conveyance pipes associated with SMPs must not be less than eight (8) inches in diameter. 9. Designs should minimize piping where possible. 10. Clean‐outs must be included, at minimum, every 75 feet and at the end of all pipes. Additionally, cleanouts should be located upstream of complicated bends and evenly spaced during straight pipe runs. 11. Every straight run of pipe should be accessible from at least two (2) points, such as a cleanout and an inlet connection. 12. 90 degree pipe bends are not permitted. At maximum, pipe bends should be at 45 degree angles, though 22 ½ degree bends are preferred. 13. Pipe bends should be avoided whenever possible. Straight pipes with fewer cleanouts are easier and less time consuming to maintain than pipes with bends and more cleanouts. 14. All intermediate (mid‐run) cleanouts and domed riser connections must be oriented upstream to allow for cleaning equipment to flush in the direction of the inlet. See PWD standard detail for cleanouts. 15. All pipes should have a structure to which they can be flushed. Typically, flushing can occur back to the green inlet. However, if pipes do not connect to a green inlet (i.e. pipe wye’s into another pipe), then a sump or other point where debris can be flushed to and removed should be provided. a. The flushing point should preferably be a green inlet or a catch basin. At a minimum, catch basins should be two (2) feet by two (2) feet concrete structures. If PVC catch basins are used, pipe inverts must be within two (2) to three (3) feet of the surface. b. If trash and debris will be removed through a domed riser, then the domed riser should be sumped with a minimum diameter of 12 inches; 15 inches in diameter is preferred. 16. All green inlets should have an inlet insert included for pretreatment. 17. Green inlets, where appropriate, may be connected in series. This facilitates flushing of the distribution pipe from inlet to inlet. The connecting pipe between inlets should generally slope towards the inlet most adjacent to the GSI system. 18. For vegetated systems, pedestrian movement across a site should be considered during design. If there is a potential for impact or trampling, site protection features such as fencing or a shrub border should be considered. 19. Reflective traffic delineator posts should be installed at all stormwater bump‐outs. 20. Inlet and outlet pipes with large openings should be protected from entry with removable, hydraulically‐efficient grates bars or grates if they present a safety hazard. Outlet protection should be included when the pipe diameter is 15 inches or greater and when the pipe length or configuration does allow daylight to be seen from end to end. IX. Trees and Plants 1. The Green Stormwater Infrastructure Landscape Guidebook contains details on plant and tree selection, as well as species lists. This guide must be used when developing landscaping plans. 2. City of Philadelphia guidelines for street tree placement must be followed. These guidelines are included in Attachment H and published in the Philadelphia Complete Streets Design Handbook. 3. Selected plant species must be able to withstand a wide range of conditions, which may include periods of inundation as well as periods of drought. 4. Selected plant species should be tolerant of salt, heat, and other urban conditions. 17 GSI Design Requirements and Guidelines 5. Selected species should not require regular pruning, grooming, watering, or other care, and should be resistant to pests and diseases. 6. Native species are preferred. 7. The soil in tree pits should provide adequate depths for root balls. Generally, a minimum adequate depth is three (3) feet from the surface elevation. It is preferred but not required that tree pits extend to the subgrade without stone storage below. 8. Two (2) to two and a half (2 ½) inch caliper trees should be specified for all proposed tree plantings. 9. Maximize tree pit openings and soil box volumes as much as possible. 10. Consider planting trees in adjacent park space where possible to maximize available soil volumes for tree. 11. Substitutions for plants may also be recommended during the design phase. If included, substitutions should be shown for each plant type as either a substitution for each plant species or as a maximum of species that can be selected by landscape contractor from a larger group. a. Example: For herbaceous plants, 3 species can be selected from a group of 5 species. 12. Container plants are preferred over plugs in most instances. X. Design Report The PWD GSI Design Report includes four (4) components. All components must be compiled and submitted as a single .PDF. In addition, supporting files in the formats specified below must be provided as separate attachments. See Attachment A: Submission Completeness Requirements for details on when each of the following reporting requirements will be provided to PWD. A. Written Report For all projects, a supporting written report must be submitted. This report will be sufficiently detailed and thorough to document the design approach and any assumptions associated with the project. The supporting files will be submitted separately as part of the final submission in .DOC or .DOCX formats. B. GreenIT Data Entry Application Metrics Report The final design metrics report will be prepared using the GreenIT Data Entry Application, which is installed locally on users’ computers. The application can be provided electronically by the PWD project manager upon request. The design metrics report (.PDF) is an output of the application. The supporting files will be submitted separately as part of the final submission in .CSV and .GREENIT formats. Examples of the report forms and information needed for filling out the data entry application are provided in Attachment G: Final Design Metrics Report. C. Supporting Calculations and Modeling For all projects, supporting calculations and models must be submitted. Design calculations must be sufficient to confirm designs. The supporting files will be submitted separately as part of the final submission in .XLS or .XLSX formats. Modeling exports may require other file formats to be submitted if PWD supports the modeling software used. The following calculations, at minimum, will be provided: 1. Contributing drainage area (impervious and pervious) 2. Storage volume 3. Loading ratio 4. Calculations of release rates for detention/slow‐release systems 5. Storm size managed 18 GSI Design Requirements and Guidelines D. Drainage Area Maps Maps of drainage area delineations for all systems are required. The supporting files will be submitted separately as part of the final submission in .DWG or .DGN formats. 1. Distinct polygons must be drawn to each inlet structure or entrance point into the system. 2. Each polygon must be labeled with the contributing area in units of square feet. 3. Each polygon must be labeled as either pervious or impervious, based on the existing condition. 4. The total drainage area for each system must be summed. 5. Drainage areas must be delineated as closed polygons on a separate drainage area layer in CAD. 19 GSI Design Requirements and Guidelines Attachment A: Submission Completeness Requirements This attachment outlines the requirements for each submission to PWD. All fields will be checked by the PWD project manager prior to design review. If a project is found to be incomplete, it will be returned to the provider and one week will be allotted for revision. A project will not progress to the next submission phase (percentage completion) until accepted per the requirements of the current phase, regardless of the number of intermediate revisions. Drawings must be prepared in accordance with the GSI Drawing Requirements Packet. Baseplan Submission (PWD 30%) Baseplan showing all requested information in the correct format may be combined with the concept check (see below). Provide the following: Baseplan information for all requested areas PDFs of all PA One Call plans received in the survey Correct sheet layout Geotechnical report, including interpretation of testing results Concept Check (If Needed) The concept check is requested when confirmation of the system features is desired prior to development of detailed plans. Concept check is frequently combined with baseplan submission. Provide the following: Preliminary layout of stormwater features in plan view Design calculations Drainage area maps Conceptual construction cost estimate, if requested Substantially Complete Design Submission (PWD 70%) Further develop designs for review by PWD with iterations as needed to provide an approved substantially complete design submission (if design is complex, an intermediate review may be added to the process). Until approved, label plans “Preliminary Design”. Upon approval, label plans “Substantially Complete Design” and submit to all required external reviews (Philadelphia Parks & Recreation, Streets, utilities, etc. See Attachment C, GSI Review Contacts). Provide the following: Materially complete plan set o All design features included and identified o Layout complete with all necessary call‐outs o Profile complete with all necessary call‐outs o Section, as needed, complete with all necessary call‐outs o All needed inverts and dimensions specified o All needed details included Design calculations sufficient to confirm designs (Excel spreadsheet format). The following calculations, at minimum, should be provided: o Contributing drainage area (impervious and pervious) o Storage volume o Loading ratio o Calculations of release rates for detention/slow‐release systems o Storm size managed Drainage area maps Complete construction cost estimate, if requested Attachment A 20 GSI Design Requirements and Guidelines Plans, Specs, and Estimate (PS&E) Submission (PWD 90%) The PS&E submission should incorporate all comments from the internal and external utility/agency reviews. There should be no design changes at this point. Provide the following: Update on external reviews. Provide evidence that all internal and external comments on the substantially complete design submission have been adequately addressed. Materially complete plan set o All design features included and identified o Layout complete with all necessary call‐outs o Profile complete with all necessary call‐outs o Section, as needed, complete with all necessary call‐outs o All needed inverts and dimensions specified o All needed details included Draft PWD GSI Design Report (single .PDF) o Written Report (.PDF only) GreenIT Data Entry Application Metrics Report (.PDF only) o Supporting design calculations and modeling (include .XLS or .XLSX as attachments) o Drainage area maps (.PDF only) Final construction cost estimate Draft specifications (with tracked changes) and bid tab Draft GPIS offsets (if work impacts right‐of‐way and PWD is bidding) Final Submission The final submission should include all deliverables necessary to submit a project to PWD Projects Control. Provide the following: Hard Copies: o Memo or email from PWD project manager approving final plans & specs o 1 set of mylar drawings (signed & stamped) o 2 sets of prints (complete with drainage area maps) o 1 copy of specification o 1 copy of Philadelphia Streets Department paving letter (if work impacts right‐of‐ way) o 1 copy of PGW response letter Electronic Submittals on CD or DVD: o Half size design drawings in .PDF format o Full size design drawings in .PDF format o Design drawings in .DWG or .DGN format o Specifications in .DOC or .DOCX format o Engineer’s estimate of construction cost in .XLS or .XLSX format o PWD Final Design Report , one .PDF with supporting attachments in specified file types Written Report (supporting attachment: .DOC or .DOCX format) GreenIT Data Entry Application Metrics Report (supporting attachments: .CSV, and .GREENIT formats) Supporting design calculations and modeling (supporting attachments: .XLS or .XLSX format, .PDF of modeling output) Drainage area maps (supporting attachments: .DWG or .DGN format) o 1 copy of each utility/agency response letter in .PDF format o GPIS spreadsheet in .XLS format (if work impacts right‐of‐way and PWD is bidding) Attachment A 21 GSI Design Requirements and Guidelines Attachment B: Final Design Package Checklist The following checklist identifies what must be submitted as part of the final design package. The completed checklist must be submitted as well. Attachment B 22 GSI Design Requirements and Guidelines PHILADELPHIA WATER DEPARTMENT Final Design Package Checklist Note: This form must accompany final design package. PWD Work Number and Project Description: Information required for final submittal Date: Provided Yes Memo or e-mail from PWD project manager approving final plans & specs 1 set of mylar drawings (signed & stamped) 2 sets of prints 1 copy of specification 1 copy of PGW response letter 1 copy of Philadelphia Streets Department paving letter No Electronic Submittals on CD or DVD: Full size Design Drawings in .PDF format Half size Design Drawings in .PDF format Design Drawings in .DWG or .DGN format Specifications in .DOC or .DOCX format Engineer’s Estimate of Construction Cost in .XLS or .XLSX format PWD Final Design Report, single .PDF with supporting attachments as per PWD requirements o Written Report in .DOC or .DOCX format o GreenIT Data Entry Application Metrics Report in .CSV and .GREENIT formats o Supporting design calculations and modeling in .XLS or .XLSX format o Drainage area maps in .PDF and .DWG or .DGN format 1 copy of each utility/agency response letter in .PDF format GPIS Spreadsheet in .XLS format (if work impacts right-of-way) Attachment B 23 GSI Design Requirements and Guidelines Attachment C: Green Stormwater Infrastructure Review Contacts All Green Stormwater Infrastructure designs, once approved by PWD, must be submitted to the following agencies and groups for review. The PWD project manager must be copied on all review submittals. Water and sewer projects must also be reviewed by the agencies listed in PWD’s Water & Sewer Design Manual. Depending on the project, review may be required by other agencies that are not listed. Unique partner projects and pilot projects in particular may have additional review requirements. If there are any new prototypes, irregular systems, materials, or devices proposed, the PWD project manager will discuss with relevant parties (Collector Systems Unit, partners, etc.) during conceptual review. All conflicts arising from reviews should be resolved by the design consultant prior to final design. Note on Access Permits: For projects Philadelphia Parks & Recreation or School District of Philadelphia property, right‐of‐entry authorization and permits are required for on‐site access. The PWD project manager can provide this form and instructions at the time of project kick‐off. Reviewer Utilities PWD Collector Systems Unit PWD GSI Maintenance Applies to Time of Submission All projects PWD Approves Submission Substantially requirements will Complete vary by utility Design All projects All projects Submission Requirements PWD Approves One full size hard Substantially copy of plan set and Complete one electronic copy Design PWD Approves One electronic copy Substantially Complete of plan set Design Contact Notes The Committee of Highway Supervisors contact list can be used for utility contacts. The PWD project manager can provide the most up‐to date list upon request. Any and all utilities that are affected must review and approve plans. Attn: Mark Waas CC: Nicholas Maliha Collectors Systems Support Philadelphia Water Department 1101 Market St., 4th Floor Email: Mark.Waas@phila.gov Nicholas.Maliha@phila.gov Attn: Barbara Cushing CC: Gerald Bright, Supervisor GSI Maintenance Group Office of Watersheds Philadelphia Water Department 1101 Market St., 4th Floor Email: Barbara.Cushing@phila.gov Gerald.Bright@phila.gov Review is coordinated internally by PWD, see GSI Design Workflows. Review of future maintenance and performance. A 45‐calendar day turnaround should be expected. Review is coordinated internally by PWD, see GSI Design Workflows. Review of future maintenance and performance and landscape selections. A 30‐calendar day turnaround should be expected. Attachment C 24 GSI Design Requirements and Guidelines Reviewer Applies to Philadelphia Streets Department Transportation Planning & Analysis Section (TP&A) Projects that impact public right‐of‐way and do not include City Plan Action (curb‐line changes) Projects that impact public Philadelphia right‐of‐way Streets and include Department Right City Plan of Way Unit Action (curb‐ line changes) Philadelphia Streets Department City Plans Unit Projects that result in changes to the City Plan (curb‐line changes) Time of Submission Submission Requirements PWD Approves Substantially One electronic copy Complete of plan set Design Three full size hard copies of plan set PWD Approves and one CD copy Substantially along with Plan Complete Review Application Design and Review Checklists Project is given final approval See application form and requirements at: www.philadelphiast reets.com/images/u ploads/resource_lib rary/City_Plan_Acti on_Request_Applica tion.pdf Contact Notes Attn: Steve Mottershead Philadelphia Streets Department Transportation Planning & Analysis Section 1401 J.F.K. Boulevard, Room 830 MSB Philadelphia, PA 19102 Tel. 215‐686‐5512 Email: Steve.Mottershead@phila.gov Review will examine pavement, curb, and ramp restoration. Approval is required to proceed with design. Attn: Harry P. Wilson Philadelphia Streets Department Highway Division, Right of Way Unit 1401 J.F.K. Boulevard, Room 830 MSB Philadelphia, PA 19102 Tel. 215‐686‐5578 | Fax 215‐686‐5182 Email: Harry.Wilson@phila.gov Review will examine compliance with Philadelphia Complete Streets Manual, curb‐line changes, and other right‐of‐way features. Approval is required to proceed with design. Submission checklists available at: http://www.philadelphiastreet s.com/customer‐ service/downloads‐and‐links Attn: Frank Morelli, Tom Marro Philadelphia Streets Department 1401 J.F.K. Boulevard Philadelphia, PA 19102 Email: Frank.Morelli@phila.gov Tom.Marro@phila.gov This is not a review, but a request to update Philadelphia City Plan to include any designed stormwater bumpouts or other curb line changes. Attachment C 25 GSI Design Requirements and Guidelines Reviewer Philadelphia Streets Department ADA Ramps Pennsylvania Department of Transportation (PennDOT) Engineering Division 6‐0 Applies to Time of Submission Submission Requirements See requirements at: www.philadelphiast reets.com/images/u ploads/resource_lib rary/Ref8and15‐ City‐of‐Philadelphia‐ ADA‐Ramp‐ submission_‐ equirements.pdf Contact Attn: Elias Issac Engineer and ADA Coordinator Streets Philadelphia Streets Department Projects that Department Transportation Planning & Analysis Section provides include new or retrofit Paving Letter 940 Municipal Services Building ADA ramp with required 1401 J.F.K. Boulevard ramp designs Philadelphia, PA 19102 replacements Tel. 215‐686‐5522 Email: Elias.Issac@phila.gov Attn: Francis J. Hanney Traffic Services Manager PA Department of Transportation One full size hard Engineering District 6‐0 copy or electronic 7000 Geerdes Blvd. copy of plan set King of Prussia, PA 19406‐1525 marked as Phone: 610‐205‐6560 “Preliminary” and with proposed work Email: fhanney@state.pa.us highlighted to both _________________________________ contacts. If Attn: Anthony Antonelli PWD Approves overflows are Projects with proposed to tie into Philadelphia County Permits Manager Substantially work on state sewers or otherwise PA Department of Transportation Complete routes 1901 Ruffner Street Design discharge to state Philadelphia, PA 19140 routes, submission Phone: 215‐225‐1415 must include Email: anatonelli@pa.gov complete calculations to CC: Matthew Miele Francis J. Hanney. Districts Permits Manager Request an 7000 Geerdes Blvd. inspector estimate King of Prussia, PA 19406 with submission. Phone: 610‐205‐6795 Email: mmiele@pa.gov Notes Review will examine ADA ramps designs for compliance with ADA Ramp Code. Requirements differ for local roads and State Routes. Additional design guidance available at: www.dot.state.pa.us/penndot/ districts/district6.nsf/services? OpenForm Approval is required to proceed with design. HOP applications through the ePermitting System (EPS) will be submitted by PWD for applicable projects at the time of construction advertisement. Attachment C 26 GSI Design Requirements and Guidelines Reviewer Philadelphia Parks and Recreation (Street Tree Management Division) Applies to Time of Submission Projects with proposed street trees Submission Requirements Contact Notes One full size and one half size hard PWD Approves copy of plan set. Substantially Memo with date of Complete submittal, PWD Design project number, title of project and street names. Attn: Frances Piller Park District Manager Street Tree Management Division Philadelphia Parks & Recreation 1515 Arch St., 10th Floor Philadelphia, PA 19102 Phone: 215‐685‐4363 Fax: 215‐685‐4364 Email: frances.piller@phila.gov Review of proposed tree locations and species selection. A date for requested review completion should be specified in the submission. Approval is required to proceed with design. Attn: Stephanie Craighead Cc: Curtis Helm Cc: Gerald Mcfeely Philadelphia Parks and Recreation One Parkway, 10th Floor 1515 Arch St Philadelphia, PA 19102 Email: Stephanie.Craighead@phila.gov Curtis.Helm@phila.gov Gerald.McFeely@phila.gov More extensive review than street tree review. Approval is required to proceed with design. Attn: Tom Schweiker Department of Capital Programs Philadelphia School District 440 N. Broad St., Room 371‐374 Plans are submitted to School District for their reference (no review/approval required). Projects on School property have special review requirements that will be included in project specific scope. Philadelphia Parks and Recreation (For Park Projects) Projects with work on PP&R property PWD Approves Substantially One full size hard copy of plan set. Complete Design Philadelphia School District Projects around schools (both public and private schools) After landscape plans have been finalized (reviewed and approved by PP&R) One full size hard copy of final landscape or tree planting plans Attachment C 27 GSI Design Requirements and Guidelines Reviewer Pennsylvania Department of Environmental Protection PWD Stormwater Plan Review Guaranteed Pavement Information System (GPIS) Submission Requirements See requirements at: www.elibrary.dep.st PWD Approves ate.pa.us/dsweb/Ho For projects Substantially mePage that disturb Complete Start with email to over 1 acre Design PADEP to requesting determination about applicability. PWD Approves Concept For partner projects that Submission (ERSA trigger See Requirements Application) Philadelphia at: and Stormwater www.pwdplanrevie Substantially Regulations w.org Complete (propose Design more than 5,000 sf earth (PCSMP disturbance) Technical Review) Project is Final GPIS offsets to Projects that given final be provided by impact public approval (in‐ design consultant in right‐of‐way house process format required by is different) PWD. Applies to Time of Submission Contact Notes Attn: Christopher Smith Civil Engineer Manager Construction Permits Section PA Department of Environmental Protection 2 East Main Street Norristown, PA 19401 Phone: 484‐250‐5152 Fax: 484‐250‐5971 Email: christopsm@pa.gov PADEP may determine that PWD GSI projects are exempt from NPDES. Determination made on case‐by‐case basis by PADEP. Attn: Victoria Lenoci, Manager CC: Sara Anderson Stormwater Plan Review Philadelphia Water Department 1101 Market St., 4th Floor Phone: 215‐685‐6387 Email: PWD.PlanReview@phila.gov Victoria.Lenoci@phila.gov Sara.Anderson@phila.gov See Partner Project Review Guidelines, Attachment D This submittal is managed by PWD. In‐house design projects submit to GPIS when PWD approves Substantially Complete Design. Attachment C 28 GSI Design Requirements and Guidelines Attachment D: Partner Project Review Guidelines Partner projects that trigger the Philadelphia Stormwater Regulations are required to meet the GSI guidelines for public projects public outlined in this packet as well as the private requirements defined in the Philadelphia Stormwater Management Guidance Manual. The simplified flowchart presented below can be used to determine whether partner projects will need to meet both requirements. The PWD project manager can provide further guidance on what reference materials apply to a particular project. Attachment D 29 GSI Design Requirements and Guidelines Attachment E: Survey Guidelines I. On Street Survey Requirements A. Extents 1. The following are the extents of the survey for a given length along a right‐of‐way (ROW), except for where otherwise directed in the below requirements: a. Extend the survey a minimum of 50 feet up any intersecting streets or alleys. b. Extend the survey a minimum of 50 feet up both sides of the intersecting, terminating street in either direction. c. Extend the survey a minimum of 50 feet past the terminating intersection along both sides of the street requested for survey. 2. Show labeled spot elevations for the top of curb and bottom of curb for both sides of the street taken at 50 foot intervals. a. Where there is an obvious localized sump, provide, at a minimum, labeled spot elevations for the centerline, building line, top of curb, and bottom of curb for both sides of the street to adequately define the sumped area. 3. Provide labeled elevations for the PC, PI, and PT at both the bottom and top of curb at intersections. 4. Survey locations for existing features as described below. B. City Plan Information 1. Include the following information relevant to City Plan: a. Extents of Right‐of‐Way distance and angles b. Block distances c. All street grades, shown along the gutter d. Cartway and footway width dimensions in both plan and sections e. Street names, including i. State Route numbers (SR#’s) ii. If the street is not legally open, this will be reflected in the street callout. f. City Plan elevations at all corners and mid‐block change in grades i. Assume the survey elevations are to City Plan if the existing elevations are within 6 inches of the City Plan data. ii. If the survey elevations are different than City Plan data by more than 6 inches, then show the existing street elevation and City Plan elevations. This difference will be reflected in a note after the street name to represent where City Plan is compared to the actual curb elevation. iii. Place arrow heads on the curb pointing in the direction of stormwater flow. g. List the survey bench mark in the upper left hand corner obtained from the Streets Department Survey District. h. Show the curb in plan view. Where it differs from City Plan or does not exist, show the City Plan curb line as a dashed line. Attachment E 30 GSI Design Requirements and Guidelines C. Plan View Information 1. Right‐of‐Way Information a. Place the name of the main street along the top of the sheet without using abbreviations. b. Abbreviate the words – street, road, avenue, etc. – on intersecting streets. c. Show the direction of traffic along with parking information on all streets including intersecting streets, shown per WSDM Appendix IIa. d. Use District Standard Measurement for all distances. e. Show all overhead bridges and the elevation of the underside of the bridge on the base plan. 2. Surface Information a. Paving Information i. Identify the materials for the roadway, footway, and curb. ii. Indicate deteriorated footways and curbing. iii. Ensure that any special patterns for the footway are carefully identified. iv. Label any obvious areas with drainage problems due to paving. b. Existing Features i. Identify all steps, cellar doors, fire hydrants, parking meters, manhole covers, traffic signs and signals, utility poles, and all street furniture (phone booths, mailboxes, benches, etc.) as shown in WSDM Appendix IIa. ii. Identify any landscaping in the ROW and, if easily available, the owner (i.e. community garden sign). iii. Show all existing curb stops, sewer vent boxes, and gas valves as shown in WSDM Appendix IIa. c. Adjacent Property Information i. Indicate all properties with street addresses and property lines. ii. Provide a general outline for all structures interior of properties adjacent to the ROW. iii. Provide general building information including use and construction (i.e. 3‐story, brick, school). iv. Indicate where the interior of the property differs in elevation from the adjacent ROW by listing the change in elevation as a positive or negative. v. Provide a general use and ground cover for properties without buildings (i.e. grass, park, garden, etc.). Where there is no use property should be listed as vacant. vi. Show all gates, driveways, access points, etc. for properties. d. Trees i. Label all existing trees inside of the ROW and with canopies that reach over the ROW with diameter. ii. Denote canopies that reach over the ROW using aerials. 3. Utility Information a. General i. Identify all existing utilities with owner, size, and cover. ii. List size by diameter or width x height, other than sewers. iii. Dimension all utilities off of the curb line to the center line of the utility. Offset from the curb is to vary consistently between dimensions. Attachment E 31 GSI Design Requirements and Guidelines iv. Show utilities, other than existing water and sewer, as double line when their width is 42 inches or greater. v. Label abandoned utilities as abandoned, when shown. b. PECO i. Label and box in high voltage electrical conduits with voltage. c. Sewer i. For sewers, list pipe size as height x width and as follows: a. Brick sewers…Feet and inches (e.g. 2'‐6" x 1'‐8"). b. Reinforced concrete pipe…Inches (e.g. 36" RCP). c. Box sewers (any material)…Feet and inches. ii. Collect inlet information as follows: a. Old brick inlets…Type and top elevation. b. New precast inlets…Type, top elevation, and invert elevation. c. Invert elevation is to be extrapolated from a survey shot using the PWD Inlet Trap detail since invert is not visible with trap door closed. d. If inlet is owned by an entity other than PWD, callout the owner. iii. Show existing sewers as follows: a. Sewers with a width of over 21 inches…Double line with a center dimension line. b. Brick sewers… Double line with a center dimension line. c. Stormwater sewers in a separate system… Double line with a center dimension line. d. Sewers with a width of less than 21 inches…single line. iv. Callout all existing sewer manholes including the first manhole on each connecting sewer with a field invert, rim elevation, and owner if not PWD. v. Show existing laterals over 6 inches in diameter with the lateral size and material, where information is available. d. Water i. Show all water mains 24 inches or greater in diameter as a double line. e. SEPTA i. Show SEPTA and railroad tracks as accurately as possible, but not dimensioned. List their status (active, inactive, or paved over). 4. Cross Section a. A cross section is needed 5 feet upstream of all existing inlets. b. Show all utilities in the entire cartway and both footways to the house lines. Label abandoned utilities (when shown) as “abandoned”. c. Show adjacent slopes or walls in the cross section. d. Where there is a railroad bridge shown on the base plan, show a cross section of the railroad bridge with underside elevations on the base plan. (This is in addition to the standard cross section for the base plan). e. City Plan information, where it deviates from existing, should be shown with a dashed line. 5. Field Observations a. The final design and specifications are very dependent on the field investigation and the information obtained from the field visit. The engineers and/or designers who visit the field location should pay special attention to the visible details of the block, which may be useful in making design decisions later. Examples of such items are: Attachment E 32 GSI Design Requirements and Guidelines i. Condition of paving, signs of paving disruptions due to Water Department infrastructure failures, etc. This information will assist in establishing appropriate paving limits. ii. Potential construction interferences such as low bridges, tree interference, overhead wires or structures, etc. iii. Condition of homes, are any vacant or collapsing, etc. iv. Neighborhood gardens II. Off Street Survey Requirements Note on Use of Ground Penetrating Radar (GPR): If record drawings are not available from the property owner, then field testing and ground penetrating radar (GPR) must be utilized to locate on‐ site underground private utilities. A. Extents 1. Within the given limits of Detailed Survey: a. Provide spot elevations on a 25 foot grid, or as necessary to provide ½ foot contours, extending 50 feet outside the provided Detailed Survey area on the attached schematic. b. Provide surveyed locations for existing features as described below. 2. Within the given limits of General Survey: a. Provide spot elevations on a 50 foot grid, or as necessary to provide 1 foot contours, extending 50 feet outside the provided General Survey area on the attached schematic. b. Provide surveyed locations for existing features as described below. 3. Within the given limits of the Project Site: a. Provide general topography at 2 foot intervals obtained from a source such as aerials with elevation data. b. Provide general outlines for major existing features such as: i. Buildings ii. Sports fields iii. Roads iv. Dense trees 4. Ensure that the survey is tied into an adjacent intersection between two cartways or a cartway and a facility entrance. B. Location Information 1. Include the following information relevant to City Plan at the required plan tie in: a. Extents of Right‐of‐Way distance and angle b. Block distances c. Street names, including State Route numbers d. List the survey bench mark in the upper left hand corner C. Plan View Information 1. Right‐of‐Way Information a. Place the name of the main street along the top of the sheet without using abbreviations. b. Abbreviate the words street, road, avenue, etc., on intersecting streets. Attachment E 33 GSI Design Requirements and Guidelines c. Show the direction of traffic along with parking information on all streets including intersecting streets, shown per Water & Sewer Design Manual Appendix IIa. d. Use District Standard Measurement for all distances. e. Show all overhead bridges and the elevation of the underside of the bridge on the base plan. 2. Surface Information a. Paving Information i. Identify the materials for the given surfaces within the Detailed Survey area including: a. Patterns b. Colors c. Deterioration ii. Label any obvious areas with drainage problems. b. Existing Features i. Identify all steps, cellar doors, fire hydrants, manhole covers, traffic signs and signals, utility poles, play equipment, benches, picnic tables and any other existing features (parking meters, stumps, fences) as shown in Water & Sewer Design Manual Appendix IIa and as appropriate. ii. Identify any landscaped areas. c. Property Information i. Indicate all properties with street addresses and property lines. ii. Provide a general outline for all structures interior of property. iii. Provide general building information including use and construction (i.e. 3‐story, brick, school). iv. Show all gates, driveways, access points, etc. for properties. d. Trees i. Label all existing trees inside of the Detailed Survey area and with canopies that reach over that area with diameter. ii. Denote canopies that are over the Detailed Survey area using aerials. iii. Denote large, dense tree areas with an edge of canopy line. 3. Utility Information a. General i. Identify all existing utilities with owner, size, and cover. ii. List size by width x height, other than sewers. iii. Show utilities, other than existing water and sewer, as double line when their width is 42 inches or greater. iv. Label abandoned utilities as abandoned, when shown. b. PECO i. Label and box in high voltage electrical conduits with voltage. c. Sewer i. For sewers, list pipe size as height x width and as follows: a. Brick sewers…Feet and inches (e.g. 2'‐6" x 1'‐8") b. Reinforced concrete pipe…Inches (e.g. 36" RCP) c. Box sewers (any material)…Feet and inches ii. Collect inlet information as follows: a. Old brick inlets…Type and top elevation. b. New precast inlets…Type, top elevation, and invert elevation. Attachment E 34 GSI Design Requirements and Guidelines c. Invert elevation is to be extrapolated from a survey shot using the PWD Inlet Trap detail since invert is not visible with trap door closed. d. If inlet is owned by an entity other than PWD, callout the owner. iii. Show existing sewers as follows: a. Sewers with a width of over 21 inches…Double line with a center dimension line b. Brick sewers… Double line with a center dimension line c. Stormwater sewers in a separate system… Double line with a center dimension line d. Sewers with a width of less than 21 inches…single line iv. Callout all existing sewer manholes including the first manhole on each connecting sewer with a field invert, rim elevation, and owner if not PWD. v. Show existing laterals over 6 inches in diameter with the lateral size and material, where information is available. d. Water i. Show all water mains 24 inches or greater in diameter as a double line. e. SEPTA i. Show SEPTA and railroad tracks as accurately as possible, but not dimensioned. List their status (active, inactive, or paved over). 4. Field Observations a. The final design and specifications are very dependent on the field investigation and the information obtained from the field visit. The engineers and/or designers who visit the field location should pay special attention to the visible details of the block, which may be useful in making design decisions later. Examples of such items are: i. Condition of paving, signs of paving disruptions due to Water Department infrastructure failures, etc. This information will assist in establishing appropriate paving limits. ii. Potential construction interferences such as low bridges, tree interference, overhead wires or structures, etc. iii. Condition of buildings, are any vacant or collapsing, etc. III. Drainage Area Information Survey Requirements A. Extents 1. The following are the extents of the survey for a given length along a ROW, except for where otherwise directed in the below requirements: a. Extend the survey until a drainage area ending point is reached. b. If ended at a mid‐block high point or inlet continues past this point 50 feet. c. If ended at the end of a block ensure that the survey extends at least 50 feet in all directions of the intersection and includes the terminating high point or inlet. d. Provide City Plan information to define the drainage area as described below. e. Provide surveyed locations for existing features as described below. B. City Plan Information 1. Include the following information relevant to City Plan: Attachment E 35 GSI Design Requirements and Guidelines a. b. c. d. e. f. All street grades, shown along the gutter. Cartway and footway width dimensions. Street names, including State Route numbers. City Plan elevations at all corners and mid‐block change in grades. Place arrow heads on the curb pointing in the direction of stormwater flow. List the survey bench mark in the upper left hand corner obtained from the Streets Department Survey District. g. Show the curb in plan view. Where it differs from City Plan or does not exist, show the City Plan curb line as a dashed line. C. Surface Information 1. Existing Features a. Identify a midblock high point with labeled elevations for both the top of curb and gutter for both sides of the cartway. i. At a 25 foot offset to other side of this high point, provide labeled elevations for both the top of curb and gutter elevations for both sides of the cartway. ii. Callout the mid‐block high point as “END OF DRAINAGE AREA: MID BLOCK HIGH POINT”. b. Identify a drainage area ending inlet with an inlet type and labeled elevations for both the top of curb and gutter at the inlet. i. If at the end of a block ensure that both the inlet and the entire intersection is shown as described above. ii. Callout the inlet as “END OF DRAINAGE AREA: INLET”. 2. Field Observations a. The final design and specifications are very dependent on the field investigation and the information obtained from the field visit. The engineers and/or designers who visit the field location should pay special attention to the visible details of the block which may be useful in making design decisions later. Examples of such items are: i. Signs of significant ponding due to paving or curbing deterioration. ii. Large contributing drainage areas such as parking lots. Attachment E 36 GSI Design Requirements and Guidelines Attachment F: Geotechnical Testing Guidelines I. General Guidelines The objective of geotechnical testing is to determine infiltration rates at proposed SMP locations and to evaluate the lithology at depths sufficient to identify any hydraulically limiting layers that would inhibit vertical infiltration and potentially cause lateral flow. The testing includes drilling borings followed by infiltration testing within the footprint of each GSI system. In general, the geotechnical investigation should consist of drilling a 20 foot deep borehole within the footprint of each proposed GSI system in order to understand the subsurface lithology. Lithological and blow count data must be collected before conducting the infiltration testing. These data can be used to refine the design of the infiltration tests and target testing of layers with greater permeability, within depths consistent with the conceptual design for the SMP. For example, a borehole may show a thin hydraulically restrictive layer immediately below the bottom of a proposed SMP. If more permeable material is observed below that restrictive layer, then designs could call for removal of the restrictive layer through over‐excavation and backfill; therefore allowing the proposed SMP to connect to the more permeable layers found during testing. Alternatively, designs could incorporate infiltration column SMPs to promote infiltration into the more permeable sub‐grades. Qualified field personnel (Professional Engineer, Professional Geologist or their representative) should be present to evaluate the lithological and blow count data. Should a limiting layer be detected and a higher permeability layer is also detected, the field personnel can notify the corresponding project manager to determine if a change in the original infiltration testing depth is warranted. Additional mobilizations should be avoided. Geotechnical investigative testing should be conducted within the footprint of each GSI system. Due to the variability in subsurface lithology, particularly in an urban environment, more than one infiltration test should be conducted for larger systems. Additional infiltration tests are required for larger systems and should be conducted every 50 feet the proposed GSI extends in any direction. A detailed layout of proposed boring locations and infiltration testing sites must be submitted to PWD and approved prior to any field activities. Borings and infiltration test locations should not be within 10 feet of each other for most GSI and the borings must be backfilled prior to infiltration testing. The specified locations may be shifted up to 10 feet in the field to avoid any unforeseen utility or other buried obstructions. Any adjustments greater than 10 feet require the approval from PWD and shall remain within the limits of the utility mark‐outs. For drainage wells, borings and infiltration test locations shall not be within 5 feet of each other. Geotechnical Report Requirements Results from geotechnical investigations are to be documented in a geotechnical report, stamped and signed by a Pennsylvania State Licensed Professional Engineer, and submitted to PWD. The geotechnical report should include, but is not necessarily limited to, the following (modified from DEP, 2013): 1. Project and site description; a. Topographic and hydrogeological setting b. Relevant site information (water bodies, nearby structures, etc.) 2. Method of Investigation Attachment F 37 GSI Design Requirements and Guidelines 3. 4. 5. 6. a. Boring method and diameter b. Standard penetration test method c. Permeability testing (borehole, double‐ring infiltrometer, well) d. Samples collected for laboratory testing Results Conclusions Summary Attachments a. Final location map showing boring and infiltration testing locations b. Boring logs (including blow counts, lithology, depth to groundwater and bedrock) c. Drainage well construction diagram (4‐inch PVC), complete with all relevant dimensions (for drainage well and infiltration column tests only) d. Laboratory results ‐ Grain size analyses and calculation of hydraulic conductivity (for sandy sediments where d10 is between 0.1 and 3.0 mm) K = C x (d10)2 where: C = Hazens Empirical Coefficient (1.0 to 1.5) d10 = effective grain size, or the diameter of the 10 percentile grain size of the material e. Infiltration test results, including all time and volume measurements, time‐discharge curve and coefficient of permeability calculations f. Photographic logs, including photographs of split spoon samples and lithological profiles from test pits (if applicable) II. Auger Boring Guidelines Prior to conducting any geotechnical borings, all boring locations must be cleared for subsurface utilities by the contractor. In addition, all applicable permits and approvals must be obtained. For each SMP, a boring is advanced to a depth of up to 20 feet or until bedrock is reached. If the proposed bottom of the infiltrating practice is deeper than 10 feet from the surface, the boring depth should extend to 10 feet below the bottom of the basin. The purpose of the boring is to define the subsurface lithology, especially the presence of shallow clay units, determine the depth to the water table and/or the depth to bedrock (if either is within 20 feet of the surface). Some projects may require that the water table and/or bedrock be reached and therefore borings may extend beyond 20 feet. Lithological samples will be collected continuously to depth. A standard penetration test (SPT) will be conducted and each split spoon sample collected following ASTM Method D1586‐11: “Standard Test Method for Penetration Test and Split‐Barrel Sampling of Soils”. For drainage wells and infiltration columns, split spoon samples should be taken continuously throughout the depth of the borehole, or until bedrock is reached. Borings will be collected at least 5 feet beyond the water table depth or until bedrock is reached. It is possible that the borings exceed 20 feet for these projects. Qualified field personnel (Professional Engineer, Professional Geologist or their representative) will be present to evaluate the lithological and blow count data. General testing procedures are highlighted below. All specified ASTM standards should be referenced for additional detail. Attachment F 38 GSI Design Requirements and Guidelines Testing Procedure 1. Perform test borings using the Hollow Stem Auger method (ASTM D6151‐08) and as follows: a. Use a machine‐driven, continuous flight, helical, hollow‐stem auger, with an inside diameter not less than 3 ¼ inches. Use truck‐mounted equipment unless otherwise directed by the Engineer. 2. Take split spoon samples in accordance with ASTM D1586‐11 and the following: a. Use a split spoon sampler with inside diameter not less than 1 3/8 inches. b. Drive sampler into undisturbed material below bottom of auger to secure sample. c. Drive sampler with 140 pound hammer dropping 30 inches and record the number of blows required to drive the sampler in 6 inch increments. d. Take samples continuously throughout the borehole depth, or until bedrock is encountered. e. Lithological descriptions will be in accordance with ASTM D2488‐09a and will include, but are not necessarily limited to, the following: Primary sediment type (sand, silt, clay, sandy silt, etc.) Texture and thickness (include indication of any fill materials such as brick, etc.) Composition of larger‐grained sediments Color (including mottles, etc.) Structure (if possible) Degree of consolidation and cementation Moisture content Evidence of bioturbation Description of contacts f. Samples collected within the split spoon immediately below the infiltration test depth should be sent to a geotechnical laboratory for grain size analysis. The testing should be conducted using a full set sieve analysis (down to No. 200 sieve) following ASTM D422‐ 63 (2007). The number of tests will be a function of the lithology within the 2 foot split spoon, but at least one test should be conducted. Additional tests will be based on a clear change in lithology within the profile (coarse sand to fine sand or silt, for example). 3. Record the depth at which groundwater is first encountered, if encountered within the first 20 feet (or beyond, if it is a project requirement). Also, measure and record the depth to groundwater at the completion of boring. 4. Upon completion of the borehole and all relevant logs, the borehole should be backfilled with the cuttings and plugged to the surface with a concrete or asphalt patch for paved surfaces. In unpaved areas covered with grass, hay and grass seed should be applied. Borings must be backfilled prior to infiltration testing. 5. For drainage well and infiltration column projects, a second hole will be drilled 5‐10 feet from the initial borehole to the proposed depth of the drainage well for infiltration testing. General logging should be conducted, but grain size analyses are not required. Attachment F 39 GSI Design Requirements and Guidelines III. Infiltration Testing Infiltration testing will be conducted during the design phase as well as during construction. Five types of infiltration testing are outlined: 1. 2. 3. 4. 5. Double Ring Infiltrometer Modified Borehole Percolation Test Borehole Infiltration Test (Bentonite Casing) Borehole Infiltration Test (Direct Push Casing) Infiltration Column Permeability Test Double‐ring infiltrometer testing is the preferred testing method for most GSI and should be conducted (where feasible) for systems in open spaces, non‐paved areas, where the surface functions to infiltrate (i.e. basins, rain gardens), and/or other areas where conditions permit. In populated areas where surface disturbance should be minimized during pre‐construction activities, double ring infiltrometer testing may not be feasible. In those instances, borehole infiltration testing should be conducted. Double‐ring infiltrometer testing may also be utilized during the construction phase (following excavation) and results compared with those obtained during pre‐construction. As mentioned above, more than one infiltration test should be conducted for larger systems. Infiltration testing for drainage wells and infiltration columns is also described. For those projects, a slotted PVC casing (well screen) is utilized and infiltration is therefore lateral through the well screen. A. Double-Ring Infiltrometer Testing Guidelines A double‐ring infiltrometer consists of two concentric metal rings. The outer ring serves to mitigate divergent flow while the water level drop in the inner ring is used to calculate the infiltration rate. This test requires excavating an area large enough to accommodate the double‐ring apparatus (test pit), to the depth of the proposed SMP bottom. Test pits should also be constructed so that they are benched for access and should not be accessed if soil conditions are unstable. All relevant OSHA regulations must be adhered to and utility mark‐outs must be conducted prior to any excavation. As indicated within the Pennsylvania Stormwater Manual, since test pits extend several feet in the horizontal and vertical directions, they allow for a more representative analysis of shallow subsurface lithology than a geotechnical boring. The lithology within the test pit should be logged in a similar fashion as the borings. Lithological descriptions will be in accordance with ASTM D2488‐09a and should include, but is not necessarily limited to, the following: Primary sediment type (sand, silt, clay, sandy silt, etc.) Texture and thickness of strata (include indication of any fill materials such as brick, etc.) Composition of larger‐grained sediments Color (including mottles, etc.) Structure Degree of consolidation and cementation Moisture content Evidence of bioturbation Description of contacts An approximate strike and dip of hydraulically limiting layers should be obtained if possible. Provide photographic documentation of the lithological section (include scale) and include with the geotechnical report. Following the infiltration test, at least one sediment sample will be collected immediately below Attachment F 40 GSI Design Requirements and Guidelines the test pit (using a hand auger, for example) and sent to a geotechnical laboratory for grain size analysis. The testing should be conducted using a full set sieve analysis (down to No. 200 sieve) following ASTM D422‐63 (2007). The number of tests will be a function of the lithology, but at least one test should be conducted. Additional tests will be based on a clear change in lithology (coarse sand to fine sand or silt, for example). For pre‐design investigations, upon completion of the test (and sediment sample collection), the pit shall be over‐excavated to the fullest extent possible to evaluate sediment lithology at depth. Testing Procedure The double‐ring infiltrometer test will be conducted in accordance with ASTM D3385‐09. A general summary of the testing procedure is below. The ASTM standard should be referenced for complete details. A general summary is as follows: 1. All technical precautions should be applied where appropriate to minimize interference of the test from the public or potential vandals. Precautions to account for evaporation, direct sunlight and significant temperature variations should also be conducted. 2. The diameter of the inner ring should be approximately 50% of the diameter of the outer ring, with a minimum inner ring diameter of 12 inches. After preparing a level testing area, the outer ring of the infiltrometer is to be placed and driven into the soil using a flat board across the top of the ring to a depth of 4 to 6 inches. The inner ring is then placed in the center of the outer ring and driven into the ground in the same manner to a depth of 2 to 4 inches. 3. A constant head within both rings needs to be maintained. Once the rings are installed, connect all appropriate valves and tubing to the rings. The use of float valves to maintain constant head is recommended (optional in ASTM standard). If manually controlling the flow of water to maintain a constant head, depth gages will be required. Head should be between 1 and 6 inches. Two constant head tanks and another water source will be required. Appropriate measures should be taken to avoid scouring and/or siltation of the native sediment (install thin (1‐inch) layer of coarse sand or fine gravel, use splash guards). 4. Record the volume of liquid required to maintain a constant head within the inner ring and the annular space at appropriate time intervals for 6 hours, or until a constant rate is achieved. It is recommended that intervals of no larger than 15 minutes be used for the first hour and 30 minute intervals be used throughout the remainder of the test. The test should run for at least 2 hours. 5. Calculate the infiltration rate as per ASTM D3385‐09. 6. Upon conclusion of the test, remove the equipment from the test pit and over‐excavate the test pit to a maximum depth that can be reached by the excavating equipment. Note the depth of the final pit and any observed stratigraphic contacts at depth. Depending on the dimensions of the original pit, the over‐excavation may make entry to the pit unsafe so observations will likely need to be made from the surface. 7. Once all testing and inspection is completed, back‐fill the excavation. Hay and grass seed should be placed on open areas. If paving was disturbed, new pavement may be required, depending on the project site. Attachment F 41 GSI Design Requirements and Guidelines B. Borehole Infiltration Testing Guidelines In paved areas or other areas where surface disturbance during testing should be minimized, double‐ ring infiltrometer testing may not be feasible and borehole infiltration testing will be required. There are a number of methods which can be utilized to collect borehole infiltration data, three of which are highlighted here: 1. Modified Borehole Percolation Test – Pennsylvania Stormwater BMP Manual) 2. Borehole Infiltration Test (Bentonite Casing Method) – Standard Test Method for Field Measurement of Hydraulic Conductivity Using Borehole Infiltration (ASTM D6391‐11), referenced below as the “ASTM Method” 3. Borehole Infiltration Test (Direct Push Casing Approach) – Maryland Stormwater Manual (2009) The appropriate method will be determined based on project requirements. For projects in relatively open areas that are not adjacent to buildings and vertical infiltration data are not critical, the modified percolation test is allowed. The modified percolation test measures direct infiltration through the sides and bottom of a borehole and the resulting percolation rate is adjusted by a reduction factor. In areas where buildings or sensitive infrastructure are within 10 feet of the GSI, a liner may be required and vertical infiltration data are critical. In those cases, either ASTM 6391‐11 or the direct push casing method will be utilized. ASTM Standard D6391‐11 notes that a borehole must be drilled and the annulus between the casing and the borehole sealed with bentonite. However, the bentonite requires time for hydration before the infiltration test can begin. If hydration time is an issue and if the borehole data indicate limited obstructions in the fill layer (if present), the direct push casing method can be applied as described below. 1. Modified Borehole Percolation Test (PA Stormwater BMP Manual) The percolation test method is presented in detail in the Pennsylvania Stormwater BMP Manual and should be referenced for greater detail. Conduct percolation testing at the depth specified by PWD project manager. Testing Procedure: The following procedure is derived from ASTM Standard 6391‐11 and the Pennsylvania Department of Environmental Protection (PADEP) criteria for on‐site sewage investigation of soils as specified in Chapter 73 of the Pennsylvania Code: 1. Boreholes for percolation testing should be 6‐10 inches in diameter. The bottom and sides of each hole should be scarified to remove any smeared surfaces and two inches of fine gravel should be placed in the bottom of the hole to prevent scour. 2. Test holes should be presoaked immediately prior to testing with the intent of simulating saturated conditions and minimizing unsaturated flow. Water should be placed in the hole to a depth of 6 to12 inches and readjusted every 30 minutes for an hour. 3. After the final presoaking period, the water level should again be adjusted to a depth of 6‐12 inches and readjusted as necessary after each reading. All additions of water shall be recorded. Measurement of water level in the percolation holes shall be made from a fixed reference point and shall continue at 30 minute intervals until a minimum of 8 readings are completed (4 hours) or until the rate of water level drop has stabilized, whichever occurs first. If the water level Attachment F 42 GSI Design Requirements and Guidelines drops below the 6 inches minimum depth during the test interval, the interval between measurements should be decreased. The duration of the test should only be shortened in the absence of any movement of water in the borehole for 4 consecutive readings (at 30 minute intervals, or 2 hours). The minimum duration of the test should be 2 hours. 4. The drop that occurs in the percolation hole during the final testing interval, expressed in inches per hour, shall represent the percolation rate for that test location. The percolation rate must be reduced according to the formula provided in the Pennsylvania Best Management Practices Manual Appendix C–Site Evaluation and Soil Testing, Protocol 1. This Appendix is also included in Appendix B of the Philadelphia Stormwater Management Guidance Manual. A minimum factor of safety of 2 must be applied to the tested infiltration rate to determine the “design” infiltration rate if the soil is coarser than a loam. Otherwise, for soils that have finer soils (silt loam, clay loam, silty clay loam, sandy clay loam and clay), a minimum factor of safety of 3 is recommended (see PA Stormwater BMP Manual). 2. Borehole Infiltration Test (Bentonite Casing Method) The following procedure is modified from ASTM Standard D6391‐11. This description serves as a summary only and the ASTM Standard should be reviewed for further detail and clarification. It’s important to note that the calculated vertical hydraulic conductivity using ASTM D6391‐11 is approximate. Natural and re‐compacted soils are usually anisotropic with respect to hydraulic conductivity. For anisotropic materials, the maximum vertical hydraulic conductivity and the minimum horizontal hydraulic conductivity are measured by this method. As per the ASTM Standard, this method is most applicable to soils with hydraulic conductivities up to 1 x 10‐3 cm/s (1.4 in/hr). As mentioned in the standard, for soils having hydraulic conductivities greater than 1 x 10‐3 cm/s, hydraulic conductivities may be determined using the standard borehole tests as outlined in the U.S. Bureau of Reclamation 7310 but it is noted that that value represents an apparent conductivity. Testing Procedure: 1. Advance a borehole to the depth of the proposed SMP bottom using hollow stem auger methods. Drilling mud should not be utilized. Boreholes for percolation testing should have a diameter at least 2‐inches larger than the OD of the casing. 2. The lithology sequence of the borehole shall be logged by continuously collecting split spoon samples (as described above). 3. Casing will be a 4‐inch Schedule 40 PVC. The bottom of the casing must be smooth and square. 4. Casing will be lowered into the borehole and firmly set into the bottom of the borehole. The borehole bottom should be scarified to remove any smeared surfaces. Measure the depth from the top of casing to the bottom of the hole to the nearest 0.01 ft. 5. Two inches of fine gravel will be placed in the bottom of the hole to prevent scour during filling of the casing. Gravel should be uniformly placed so that is of equal thickness throughout the hole. Re‐measure the depth from the top of casing to the gravel surface to the nearest 0.01 ft. 6. The annular space between the casing and borehole shall be sealed with sodium bentonite, in layers. The bottom layer will consist of a bentonite paste, having a thickness of 1‐2 inches. This will be tamped in place using a wooden dowel or equivalent. The remainder of the annulus will Attachment F 43 GSI Design Requirements and Guidelines be filled with powdered or granular sodium bentonite in layers no more than 2 inches thick. Bentonite chips or pellets may also be used. Each layer shall be moistened with water and tamped with a wooden dowel. If granules are used, the granular diameter will be less than 1/5 the annular spacing. Bentonite can be either poured from grade or installed using a tremie pipe. Do not add water such that the bentonite becomes a thin slurry. Only add enough water for hydration. 7. Allow the bentonite to hydrate for a period of at least 2 hours. Install a cap or cover over the top of the casing and borehole to prevent desiccation and rainfall from entering the hole. Block off the area as appropriate. The seal should be checked prior to testing to ensure that it has set. 8. Test holes should be presoaked immediately prior to testing with the intent of simulating saturated conditions and minimizing unsaturated flow. Fill the casing with water at a very low rate so as not to disturb the bottom sediments. Water should be placed in the hole to a depth of at least 6 to12 inches above the bottom and readjusted every 30 minutes for an hour. Depth may be greater and/or more water may be required for higher infiltration rates. Alternatively, a constant head can be applied in which water level is maintained at the top of the casing. 9. After the final presoaking period, the water level will be measured over time as a falling head test. Initial water level will be at least 12 inches above the bottom of the borehole and readjusted as necessary. If initial measurements indicate a high infiltration rate, then the casing can be filled so that the water is higher than 12 inches from the bottom of the hole, as appropriate. All additions of water (volume) shall be recorded. 10. Measurement of water level in the casing shall be made from the top of the casing and shall continue at regular time intervals, not exceeding 30 minutes. Similar to the double ring testing procedure, it is recommended that time intervals not exceed 15 minutes for the first hour. The overall duration of the test will last until the rate of change in water level is constant but should last at least 2 hours. The test can be stopped in the absence of any movement of water in the borehole for 2 hours, or for after 4 consecutive 30‐minute readings. 11. Upon completion of the test, remove the casing and backfill the borehole with cuttings. For paved areas, plug the hole with a bentonite plug and seal the surface with concrete or asphalt. For open areas, lay grass seed onto the surface. 12. Calculate the infiltration rate as described in ASTM Standard D6391‐11. Assuming that temperature effects are insignificant, the infiltration rate simplifies to: 1 1 2 1 : 1 11 Attachment F 44 GSI Design Requirements and Guidelines K1 = maximum vertical field saturated hydraulic conductivity (inches/hour) D = the internal diameter of the casing (inches) h1 = the height of the water above the bottom of the casing at t1 (inches) h2 = the height of the water above the bottom of the casing at t2 (inches) t1 = time at the beginning of increment t2 = time at the end of increment 3. Borehole Infiltration Test (Direct Push Cased Approach) An alternative approach to utilizing the ASTM standard is a method involving hydraulically driving casing through an augered borehole. The method is similar to the approach outlined in the Maryland Stormwater Manual (2009). Testing Procedure: 1. Advance an 8‐inch borehole to 12 inches above the planned SMP bottom using hollow stem auger methods. 2. Lower a 4‐inch casing through the borehole and push the casing 12 inches through the bottom of the borehole. 3. Clear out the sediments within the casing. 4. Once the sediment within the casing has been removed, measure the depth to the bottom of the hole from the top of the casing. The depth should correspond with the planned depth of the SMP. 5. Two inches of fine gravel should be placed in the bottom of the hole to prevent scour during filling of the casing with water. Gravel should be uniformly placed so that is of equal thickness throughout the hole. Re‐measure the depth from the top of casing to the gravel surface to the nearest 0.01 ft. 6. Test holes should be presoaked immediately prior to testing with the intent of simulating saturated conditions and minimizing unsaturated flow. Fill the casing with water at a very low rate so as not to disturb the bottom sediments. Water should be placed in the hole to a depth of at least 6 to12 inches from the bottom of the hole and readjusted every 30 minutes for an hour. Depth may be greater for higher infiltration rates. 7. After the final presoaking period, the water level will be measured over time as a falling head test. Initial water level will be at least 12 inches above the bottom of the borehole and readjusted as necessary. If initial measurements indicate a high infiltration rate, then the casing can be filled so that the water is higher than 12 inches from the bottom of the hole, as appropriate. All additions of water (volume) shall be recorded. 8. Measurement of water level in the casing shall be made from the top of casing and shall continue at regular time intervals, not exceeding 30 minutes long. It is recommended that the intervals not exceed 15 minutes during the first hour of the test. The overall duration of the test will last until the rate of change in water level is constant, but should last for a period of at least 2 hours. The test can be stopped in the absence of any movement of water in the borehole for 2 Attachment F 45 GSI Design Requirements and Guidelines hours, or for after 4 consecutive 30‐minute readings. 9. Upon completion of the test, remove the casing and backfill the borehole with cuttings. For paved areas, plug the hole with a bentonite plug and seal the surface with concrete or asphalt. For open areas, lay grass seed onto the surface. 10. Calculate the infiltration rate as described in ASTM Standard D6391‐11. Assuming that temperature effects are insignificant, the infiltration rate simplifies to: 1 1 2 1 : 1 11 K1 = maximum vertical field saturated hydraulic conductivity (inches/hour) D = the internal diameter of the casing (inches) h1 = the height of the water above the bottom of the casing at t1 (inches) h2 = the height of the water above the bottom of the casing at t2 (inches) t1 = time at t1 (beginning of increment) t2 = time at t2 (end of increment) C. Infiltration Column Permeability Testing Guidelines For projects that include drainage well or infiltration column SMPs, deeper investigations of the depth of the water table and/or bedrock are required. Drainage well projects require geotechnical investigation to be developed during the pre‐construction design and during construction (proof testing) using full scale testing. In addition, a 4‐inch PVC slotted well screen should be installed to the same depth as the proposed drainage well and an infiltration test conducted. A full set of data (borings, infiltration rates) should be collected for each drainage well location. Ideally, the geotechnical borings will provide information on the water table depth and the depth to bedrock. If the water table is within the bedrock, completing the boring to the surface of the bedrock is permitted. As drainage wells will be located in the street, all necessary safety precautions should be taken and all relevant permits must be obtained. Pre‐Construction Infiltration Testing The test involves installing a PVC well screen and performing a percolation test. The testing procedure is modified from the United States Bureau of Reclamation (USBR) Procedure 7300, Performing Field Permeability Testing by the Well Permeameter Method. Testing Procedure: 1. Drill a 6‐8 inch borehole to the depth of the proposed drainage well using the hollow stem auger method (ASTM D6151‐08). Install a PVC well cap on one end of a 4‐inch I.D. Schedule 40 PVC well screen and lower into the borehole. The cap should be securely attached, making a positive seal. Sections of well screen should be added corresponding to the proposed length of perforated pipe of the planned drainage well. A 3 foot section of solid PVC casing should be connected to the slotted well screen section and extended to the surface, depending on the proposed design. If fill containing coal slag, ash and/or extensive debris (brick, concrete, glass, etc.) is encountered, the solid casing should extend through that layer to a depth of at least 3 feet below. Infiltration in these deposits is prohibited. Attachment F 46 GSI Design Requirements and Guidelines 2. PVC well screen shall be new and flush threaded as per ASTM standards (ASTM D6724). The slot size of the well screen should be 0.060 inches (60 slot). The annulus between the well screen and the borehole should be filled with gravel pack, U.S. Silica FilPro #4 or equivalent. 3. Infiltration testing shall be conducted by measuring the flow rate that is needed to maintain a constant head in the well. Use of a reservoir and float valves as described in USBR 7300 is suitable, but not required. Variations to the reservoir set up and the maintenance of the constant head are permitted as long as measurement of flow can be accurately made. Constant head should be maintained at least 1 foot above the slotted screen interval, but at least 1 foot below fill containing slag, ash or debris. Once the water level has stabilized, record the volume loss from the constant head reservoir over time. Specific increments are not given in the USBR 7300 procedure, but regular increments should be used, at least every 15 minutes. As per USBR 7300, the test should be continued for at least 4 hours without letting the reservoir completely empty. 4. Upon completion of the infiltration test and all relevant logs, the well screen should be removed (if possible) and the hole backfilled with the cuttings. The surface restored using a concrete or asphalt patch. If the PVC materials cannot be retrieved, the casing extension should be removed or should be cut to at least 6 inches below the surface. The screen is then backfilled with cuttings and the surface is restored. 5. The permeability coefficient should be computed as follows: a. If the depth to the water table or impervious layer is greater than 3 times the depth of the water in the test well: 1 2 20 1 2 2 2 1 b. If the depth to the groundwater table or impermeable unit is less than 3 times the depth of water in the well, 2 where: k20 = coefficient of permeability at 20 deg C h = height of water in the well r = radius of the well q = discharge rate of water from the well for steady‐state constant head condition (determined from the straight line of a graph of total volume vs. time (see Figure 7 in USBR 7300). V = , , Tu = unsaturated distance between the water surface in the well and the water table Attachment F 47 GSI Design Requirements and Guidelines 6. In addition to the permeability coefficient, an alternative infiltration rate should be calculated using the discharge rate of water from the well for steady‐state constant head condition divided by the open area of the well screen. This rate should be converted to inches per hour and reported along with the coefficient of permeability calculated using the USBR Procedure 7300 method. Post‐Construction Infiltration Testing Infiltration is to be conducted post‐construction of the drainage well(s) and prior to construction of the sedimentation manhole. As per the Portland Stormwater Management Manual (2014), infiltration testing should indicate that the drainage well(s) are adequately sized to handle the calculated runoff flow rate. Runoff is to be calculated using the Rational Method and the appropriate rainfall intensity: Q = CfCIA where: Q = flow in cubic feet per second Cf = Runoff coefficient adjustment factor (assume 1) C = runoff coefficient (typically 0.85 to 1.0 for impervious cover) I = rainfall intensity (inches per hour) The drainage wells should be maximized to full potential, ideally able to capture the peak storm intensity for a typical year which is equivalent to 2.5 inches per hour (0.625 inches per 15 minute interval). So, for a site draining 10,000 square feet, the design flow rate is calculated as: Q = (0.9) x (2.5) x (10000/43560) = 0.52 cfs, or 232 gallons per minute So, the drainage well in this example should have the capability of accepting 232 gallons per minute. IV. References ASTM International. 1963. ASTM D422‐63 (Reapproved 2007), Standard Test Method for Particle Size Analysis of Soils. ASTM International. 2008. ASTM D6151‐08, Standard Practice for Using Hollow‐Stem Augers for Geotechnical Exploration and Soil Sampling. ASTM International. 2009. ASTM D2488‐09a, Standard Practice for Description and Identification of Soils (Visual‐Manual Procedure). ASTM International. 2009. ASTM D3385‐09, Standard Test Method for Infiltration Rate of Soils in Field Using Double‐Ring Infiltrometer. ASTM International. 2011. ASTM D1586‐11, Standard Test Method for Standard Penetration Test (SPT) and Split‐Barrel Sampling of Soils. ASTM International. 2011. ASTM D6391‐11, Standard Test Method for Field Measurement of Hydraulic Conductivity Using Borehole Infiltration. City of Portland 2014 Stormwater Management Manual; City of Portland, Bureau of Environmental Services; January 2, 2014 Maryland Stormwater Design Manual, Volumes I and II. October 2000, Revised May 2009. Accessed online at: http://www.mde.state.md.us/programs/Water/StormwaterManagementProgram/MarylandStormwaterDesignMan ual/Pages/Programs/WaterPrograms/SedimentandStormwater/stormwater_design/index.aspx New York City Department of Environmental Protection Office of Green Infrastructure. 2013. Procedures Governing Limited Geotechnical Investigations for Right of Way Bioswales, Stormwater Green Streets and Other Stormwater Management Practices, January 2013. Accessed online, September 11, 2013: http://www.nycedc.com/sites/default/files/files/rfp/qa‐documents/DEP‐OGI%20Geotech%20Procedure.PDF U.S Department of the Interior, Bureau of Reclamation, Earth Manual, Part 2, Third Edition, 1990. Attachment F 48 GSI Design Requirements and Guidelines Attachment G: Final Design Metrics Report The final design metrics report must be prepared using the GreenIT Data Entry Application, which is installed locally on users’ computers. The application can be provided electronically by the PWD project manager upon request. The report shown on the following pages is generated by the GreenIT Data Entry Application and is included for demonstration of the fields that are being tracked. Definitions and rules to be referenced when preparing the design metrics report are also included in this attachment. Attachment G 49 GSI Design Requirements and Guidelines Attachment G 50 GSI Design Requirements and Guidelines Attachment G 51 GSI Design Requirements and Guidelines Attachment G 52 GSI Design Requirements and Guidelines Design Report Definitions Some fields are not required or are made inactive based on the system function or the SMP type. Users can reference the GreenIT Data Entry Application User Guide for a complete list of business rules. Field Name Units Definition Additional Information INFILTRATION TEST DATA METRICS Deep Boring feet Depth of deepest test at system Depth location. If deep boring test conducted, this should be the depth of the deep boring. Depth to feet The depth to the bedrock measured Bedrock from the surface. If no bedrock was detected during the deep borings or infiltration testing, this should be given as not encountered. Depth to feet The depth to the groundwater table Groundwater measured from the surface. Infiltration Rate inches per hour Test Date date Test Type category value Infiltration rate calculated from infiltration testing. Includes reduction factor. Date of infiltration testing. Type of infiltration test conducted. Category values include: Double Ring Infiltrometer, Modified Borehole Percolation, Borehole Infiltration (Bentonite Casing), Borehole Infiltration (Direct Push Casing), Infiltration Column Permeability SYSTEM LEVEL METRICS A System is a combination of SMPs that are hydraulically connected and function as a unit to manage a given drainage area. Contributing square Existing impervious surface, which has Impervious feet a direct connection to the stormwater Area management system. Contributing square The drainage area to the stormwater Pervious Area feet management system from additional existing pervious surfaces. This is mostly applicable for off‐street work. Disconnected square Impervious surfaces that drain to Impervious feet pervious surfaces, such as depaved Area areas, and that do not connect to the sewer drainage system. Infiltration feet The depth of water from the bottom Depth/Head of the infiltration storage capacity to the top of the storage, inclusive of all storage media, (gravels, soil, sand, and free surface water depths, etc.) This does not include depth above overflow weirs, or other storage capacity limiting discharge points. Attachment G 53 GSI Design Requirements and Guidelines Field Name Units Definition SYSTEM LEVEL METRICS (continued) Infiltration Footprint square feet Orifice Diameter inches Sewer System Type category value Slow Release Hydraulic Head feet Storage Footprint System Name, System Number square feet text Storage Volume cubic feet System Function category value Tree Pit Volume in Storage Volume Underdrain cubic feet The volume of the tree pits below the overflow elevation within the storage volume. Yes/No The perforated pipe placed within a system for the purpose of slow‐ releasing or draining stormwater back to the sewer. The volume in the stone voids below the elevation of the orifice for slow‐ release systems or below the elevation of the center of the underdrain for infiltration systems. Volume below the Orifice of Center of Underdrain cubic feet Additional Information The area where infiltration will occur. This does not include any part of the storage that is lined with an impermeable liner. The diameter of the orifice used to regulate the flow back to the sewer system. This is not applicable if the system is designed for infiltration. The sewer system infrastructure from which runoff is diverted to be managed in the green stormwater infrastructure system. The depth of water from the bottom of the orifice to the overflow weir or discharge point, inclusive of all potential storage media, (gravel, soil, sand, and free surface water depths, etc.) This does not include depths of water below the orifice for either infiltration or pipe bedding. The area occupied by the physical storage volume of the SMP. Unique identifier for system. Composed of the project ID and system ID. System Number and System Name should be the same. The volume of runoff storage created by the system. For infiltration systems, the entire depth of the system is counted. In detention/slow‐ release systems, only the depth above the orifice elevation is counted. The system function refers to the way stormwater is managed by the system. Category values include: Combined, Non‐Contributing, Separate, Storm Water Only Category values include: Infiltration, Detention/Slow Release, Separation, Disconnection Defaults to Yes Attachment G 54 GSI Design Requirements and Guidelines Field Name Units Definition CALCULATED SYSTEM LEVEL METRICS Credited Green Acres acre‐ inches Expression of the volume of stormwater managed by the GSI practice up to, but not exceeding 2 inches of runoff managed. Primary metric to track GSI projects. A conversion of the system storage volume into acre‐inches. Credited Storm Size Managed inches The depth of runoff managed by the system up to, but not exceeding 2 inches. Greened Acres (GA) acre‐ inches Expression of the volume of stormwater managed by the GSI practice. A conversion of the system storage volume into acre‐inches. Loading Ratio for Connected Impervious Area Loading Ratio for Total Contributing Drainage Area ratio Ratio of the connected impervious area to the infiltration footprint. ratio Ratio of the total contributing drainage area to the infiltration footprint. Additional Information Uses the formula: If storm size managed <= 2 in, Credited Greened Acres = Total Greened Acres (acre‐in) If storm size managed > 2 in, Credited Greened Acres = Total Contributing Impervious Drainage Area (sf) * 2 in * (1 acre / 43560 sf) If Total Contributing Impervious Drainage Area is Null, Credited Greened Acres = Total Greened Acres (acre‐in) (For Single Stormwater Tree Systems) If Total Contributing Impervious Drainage Area = 0, Credited Greened Acres = 0 If System Function = Disconnection, Credited Greened Acres = (Disconnected Impervious Area (sf) + Total Pervious Area (sf) (from summed SMP data)) * 1 in * (1 acre/ 43560 sf) Uses the formula: If storm size managed <= 2 in, then Credited Storm Size Managed = Storm Size Managed (in) If storm size managed > 2 in, then Credited Storm Size Managed = 2 in If System Function = Disconnection or Total Contributing Impervious Drainage Area is Null, Credited Storm Size Managed = 1 in If Total Contributing Impervious Drainage Area = 0, Credited Storm Size Managed = 0 Uses the formula: Greened Acre = Storage Volume * (12 in / 1 ft) * (1 acre / 43560 sf) If Total Contributing Impervious Drainage Area = 0, Greened Acres = 0 If System Function = Disconnection, Greened Acres = (Disconnected Impervious Area (sf) + Total Pervious Area (sf) (from summed SMP data)) * 1 in * (1 acre/ 43560 sf) Uses the formula: Loading Ratio for Connected Impervious Drainage Area = Connected Impervious Drainage Area (sf) / Infiltration Footprint (sf) Uses the formula: Loading Ratio for Total Contributing Drainage Area = Total Contributing Drainage Area (sf) / Infiltration Footprint (sf) Attachment G 55 GSI Design Requirements and Guidelines Field Name Units Definition CALCULATED SYSTEM LEVEL METRICS (continued) Additional Information Peak Release Rate cubic feet per second The maximum flow rate through the orifice when the system is full. Storm Size Managed inches The depth of runoff managed by the system. Uses the formula: Total Contributing Drainage Area square feet The impervious and pervious drainage areas flowing into the system. Uses the formula: Uses the formula: Q = CA √(2gh) where Q = Peak Release Rate; C = 0.62; A=Area of orifice (in) = π*(diameter/12)2/4; G = gravity (ft/s2) = 32; H = Slow Release Hydraulic Head (ft) Storm Size Managed = Storage Volume (cf) * (12 in / 1 ft)/ Connected Impervious Area (sf) If Total Contributing Impervious Drainage Area = 0, Storm Size Managed = 0 Total Contributing Drainage Area = Contributing Pervious Area (sf) + Contributing Impervious area (sf) SMP LEVEL METRICS SMPs, or Stormwater Management Practice, are the individual assets that compose a GSI System. Number of SMP Trees count Ponding Depth inches Pretreatment category value Primary Storage Type category value Primary Storage Type Depth SMP Footprint feet The depth of the primary media in which water is stored. square feet text The flat, horizontal area of the SMP bounded by the lowest contour. Unique identifier for SMP. Composed of the project ID, system ID, and SMP ID. SMP Number and SMP Name should be the same. The type of stormwater management practice. The categories are defined based on the unique maintenance requirements. See following page for definitions of each SMP type. SMP Name, SMP Number SMP Type Category value The number of new trees planted within or immediately adjacent to the SMP. The maximum depth of free surface water in surface systems, taken as the finished soil grade to the overflow or discharge point. The type of method used to screen particles before entering the green infrastructure. Multiple categories can be selected. The primary media in which water is stored. Multiple categories can be selected. Category values include: Sump, Forebay, Inlet Insert, Upstream SMP, Trapped Inlet, Filter Strip, and/or Screen Category values include: Soil, Stone, Modular, Ponding, and/or Pipe Category values include: Basin, Blue Roof, Bump‐out, Cistern/Rain Barrel, Depaving, Drainage Well, Green Gutter, Green Roof, Infiltration Column, Infiltration/Storage Trench, Pervious Paving, Planter, Rain Garden, Stormwater Tree, Swale, Tree Trench, Wetland, and Other. Attachment G 56 GSI Design Requirements and Guidelines Field Name Units Definition SMP LEVEL METRICS (continued) Total Pervious square The total area of the pervious surface Area feet of the SMP installed, inclusive of tree pits inside of systems and depaving. Total square The total area planted with Vegetated Area feet vegetation, exclusive of tree pits. Tree Pit cubic Volume in feet Storage Volume PROJECT LEVEL METRICS Number of Non count System Trees Additional Information The volume of the tree pits below the overflow elevation within the storage volume. Number of additional tree plantings not planted within or immediately adjacent to any SMPs. Attachment G 57 GSI Design Requirements and Guidelines SMP Type Definitions SMP Type Name Definition/Purpose Basin A stormwater basin is a basin or depression that is vegetated with mowed grass. It is designed to detain and release stormwater runoff and/or infiltrate where feasible. Blue Roof A blue roof is a storage system designed into a roof surface such that the roof retains stormwater. Blue roofs are designed to reduce the rate of stormwater runoff. Bump‐out A stormwater bump‐out is a vegetated curb extension that intercepts gutter flow. It is designed to detain and release stormwater runoff and/or infiltrate where feasible. Cistern/Rain Barrel Depaving Drainage Well Green Gutter Green Roof Infiltration Column Infiltration/Storage Trench A cistern/rain barrel is a tank or storage receptacle that captures and stores runoff and can thereby reduce runoff volume. The stored water may be used to serve a variety of non‐potable water needs (e.g., irrigation). Depaving projects remove existing impervious pavement and restore the surface with grass, other types of vegetation, or loose materials (stone, mulch, etc.) such that the area can thereafter be considered pervious area. Depaving projects remove contributing impervious area from the sewer system. A stormwater drainage well is manhole structure designed to manage stormwater runoff by receiving stormwater from upstream collection and pretreatment systems and then discharging the stormwater into the surrounding soils through perforations in the manhole. It is designed to infiltrate stormwater. A green gutter is a narrow and shallow landscaped strip along a street’s curb line. It is designed to manage stormwater runoff by placing the top of the planting media in the green gutter lower that the street’s gutter elevation allowing stormwater runoff from both the street and sidewalk to flow directly into the green gutter. It is designed to slow and infiltrate stormwater. A green roof is a vegetated surface installed over a roof surface. Green roofs are effective in reducing the volume and rates of stormwater runoff. An infiltration column is a stone column that extends below the bottom of the surrounding GSI system in order to promote infiltration in more permeable sub‐grades that exist at greater depths. An infiltration/storage trench is a subsurface structure designed to detain and release stormwater runoff and/or infiltrate where feasible. Attachment G 58 GSI Design Requirements and Guidelines SMP Type Definitions SMP Type Name Pervious Paving Planter Rain Garden Stormwater Tree Tree Trench Wetland Definition/Purpose Pervious paving is a hard permeable surface commonly composed of concrete, asphalt or pavers. It is designed to detain and release stormwater runoff and/or infiltrate where feasible. A stormwater planter is a structure filled with soil media and planted with vegetation or trees. It is designed to detain and release stormwater runoff and/or infiltrate where feasible. Planters often contain curb edging or fencing as barrier protection around the planter. A rain garden is a shallow vegetated area designed to detain and release stormwater runoff and/or infiltrate where feasible. Rain gardens may also be referred to as bio‐infiltration basins and bio‐retention basins. They are typically integrated into landscape features (e.g. median strips) and are non‐mowed areas. A stormwater tree is planted in a specialized tree pit that has stormwater runoff directed to its pit. It is designed to manage stormwater by placing the top of the planting media in tree pit lower than the street’s gutter elevation and connecting the tree pit to an inlet which directs runoff from the street into the tree pit. It is designed to detain and release stormwater runoff and/or infiltrate where feasible. A stormwater tree trench is a subsurface infiltration/storage trench that is planted with trees. They are typically linear features that are constructed between the curb and the sidewalk. It is designed to detain and release stormwater runoff and/or infiltrate where feasible. A stormwater wetland is a vegetated basin designed principally for pollutant removal. It typically holds runoff for periods longer than 72 hours and may include a permanent pool. Wetlands can also detain and release stormwater runoff. Attachment G 59 GSI Design Requirements and Guidelines SMP Rules and Examples The following describes when a new SMP form should be completed. Note on Distinction between SMPs and Systems: SMPs, or Stormwater Management Practices, are the individual assets that compose a GSI System. Examples include a planter inside of an infiltration bed; the two function together as one system, but are distinct SMPs with unique maintenance requirements. Rule Example Number of SMPs Any tree trench or infiltration/storage trench that is hydraulically connected is considered one SMP. New SMPs should not be created due to breaks in the actual trench work or for sections of trench that are located on a different block. One (1) SMP 1 Tree Trench If part of a system’s trench work is on a different block and does not include trees, whereas the other trench work did include trees, the SMP is still coded as one SMP (type = tree trench). A new infiltration/storage trench SMP should not be created. One (1) SMP 1 Tree Trench A bump‐out that wraps the corner is counted as one SMP (type = bump‐out), not as two. Two (2) SMPs 1 Tree Trench and 1 Bump‐ Out Stone storage included below pervious pavement should not be counted as a separate SMP (type = infiltration/storage trench) when runoff can only enter through the pavement surface. In this case, the entire system is coded as one SMP (type = pervious pavement). One (1) SMP 1 Pervious Pavement Attachment G 60 GSI Design Requirements and Guidelines Rule Example Number of SMPs Stone storage included below pervious pavement should be counted as a separate SMP (type = infiltration/storage trench) only when runoff enters through an inlet structure and is sent directly into the stone bed. Two (2) SMPs 1 Pervious Pavement and 1 Infiltration / Storage Trench Stone storage below a rain garden should be counted as a separate SMP (type = infiltration/storage trench). Stone bedding provided solely for pipe bedding below a rain garden should not be counted as a separate SMP. Two (2) SMPs 1 Rain Garden and 1 Infiltration / Storage Trench Each distinct planter box should be counted as separate SMPs. Two (2) SMPs 1 Tree Trench and 1 Planter Each distinct planter box should be counted as separate SMPs. Five (5) SMPs 1 Infiltration / Storage Trench and 4 Planters Attachment G 61 GSI Design Requirements and Guidelines Attachment H: City of Philadelphia – Street Tree Guidelines The following guidelines are taken from the Philadelphia Complete Streets Design Handbook, which can be located at http://philadelphiastreets.com/handbook.aspx. See next page for a diagram illustrating this information. Location 1. Intersections a. Trees should be planted a minimum of 55 ft from any intersection approaching a traffic signal or STOP sign where there is no parking on the right. b. Trees should be planted a minimum of 45 ft from any intersection approaching a STOP sign or traffic signal where there is parking on the right. c. Trees should be planted a minimum of 35 ft from any intersection. 2. Street Lighting a. Trees should be planted a minimum 15 ft from any pedestrian scale street light pole. b. Trees should be planted a minimum 20 ft from any other street light pole. 3. Driveways a. Trees should be planted a minimum 10 ft from a driveway. b. Trees should be planted a minimum of 15 ft from a commercial driveway which serves a parking lot of 5 or more spaces. 4. Curb Line/Sidewalk a. Trees should be planted 3 feet from curb face (2 feet minimum). b. Trees should not be placed in front of steps, doorways, or alleyways c. 5 ft of unobstructed sidewalk width should be maintained (4 feet minimum). d. Certain City districts may require larger amounts of sidewalk. Please refer to the Philadelphia Pedestrian and Bicycle Plan for more information. 5. Utilities a. Trees should be planted a minimum of 5 feet between the center of the root ball/trunk and any residential utility line b. Trees should be planted a minimum of 5 ft from manholes, storm inlets/drains, and utility mains/ducts. 6. Sign poles a. Trees should be placed a minimum of 5 feet away from any sign pole b. Sign relocation may be possible. Contact the Streets Department. Species Consideration 1. Species must be selected from Parks & Recreation’s approved list 2. Use trees with narrow canopies (columnar types) within 100 ft of any intersection 3. Use trees with low canopies where overhead wires exist. Attachment H 62 GSI Design Requirements and Guidelines Street Tree Placement Guidelines Attachment H 63 GSI Design Requirements and Guidelines Attachment I: Philadelphia Parks & Recreation Street Tree Review All proposed street tree location designs should be submitted according to the following requirements. A. Consultant Submittal 1. Memo with date of submittal, engineer name, PWD project number, title of project and street names. 2. Full scale and half scale drawing indicating where the stormwater system will be located and which sidewalk areas are to be planted with trees. B. Drawing Details 1. Full sheet size: 30” x 42” 2. Scale: 1 inch = 20 feet or 1 inch = 30 feet (best fit on sheet) C. Drawing Sheet to include 1. Engineer Name, date and project title 2. Block Plan of the project area at 1:20 or 1:30 3. North arrow 4. Legend of existing and proposed features 5. Scale bar 6. Key Map showing the area with north at the top of the sheet D. Block Plan to include 1. Utilities 2. Street ROW 3. Street Names 4. Curb Lines 5. Property Lines 6. Ownership 7. Buildings with Property Addresses 8. Stairs, Gates, Doors, other structures within or along the ROW 9. Existing Trees 10. Park Facilities 11. Murals & Monuments 12. Stormwater System location (heavy line with light hatching) 13. Call out for stormwater system location 14. Proposed tree plantings numbered T1 through T(x), dimensioned from fixed reference points E. PP&R Street Tree Division Response 1. Approval memo 2. If necessary or requested, notated drawing sheet with tree locations and numbers – to be returned to PP&R Street Tree Division 3. Spreadsheet linking tree numbers to species selection – botanical and common name Attachment I 64 GSI Design Requirements and Guidelines Example Tree Planting Plan The following is an example of a plan submitted by a consultant to Philadelphia Parks & Recreation for street tree review. Attachment I 65
