LDS Task Descriptions
General Location Drainage Map
Description:
This task involves the preparation of the General Location Drainage Map to show the
project with respect to the overall drainage features. The base map for the General
Location Drainage Map is a color copy of the USGS Hydrologic Atlas (HA). If the HA
is not available use the USGS Quadrangle map. The scale of the base map should be
maintained. Draw or sketch any missing pertinent highways on the HA Atlas. Refer to
Section 2-201 of the IDOT Drainage Manual for additional information.
Specific Tasks:
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Show the project limits and label the project route and crossroads. The drainage
divides shown on the HA map and the contours should be legible. Additional subdrainage divides will be shown on the Existing Drainage Plan, if available, otherwise
show on the General Location Drainage Map for each Major Culvert Crossing. All
significant offsite areas tributary to the highway should be shown.
Show the location of the identified drainage problems (non-maintenance type), label
the receiving streams, and major drainage features (include sizes) on the General
Location Drainage Map. A key should be used to distinguish locations of identified
drainage problem areas and should reference those listed in Section 1-01 of the
Location Drainage Study.
Add north arrow, title, and scale.
Deliverable:
1.
Exhibit 1-00a, General Location Drainage Map.
ACEC-Illinois / IDOT Drainage Seminar 2014
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LDS Task Descriptions
Existing Drainage Plan
Description:
This task describes the requirements of a detailed Existing Drainage Plan (EDP). Section
2-202 of the IDOT Drainage Manual provides additional detail on requirements for the
EDP. The purpose of the EDP is to illustrate the current drainage features to the extent
necessary to define:
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External areas which drain to the proposed highway right of way;
Sheet and concentrated flow entering the highway drainage system;
Drainage summits along and adjacent to the highway, including the centerline of the
roadway. Drainage divides as indicated by the Hydrologic Atlases (HA's) must be
shown; interpreted sub-divides (summits) as determined by the Drainage Engineer
should also be shown;
Existing closed drainage systems, which include local drainage facilities located
within the proposed highway right of way (local facilities are to be appropriately
labeled);
Low flow and flood flow (overflow);
Highway outlets with interpreted tributary areas;
Floodplain and floodway boundaries.
Contour mapping and aerial imagery is available to the Department from all counties in
District/Region One. IDOT will provide 1-ft or 2-ft contour mapping and aerial imagery
in digital format. Both aerial imagery and contour mapping should be used as the EDP
base map, along with existing CADD topography. Screening, gray-scaling, and/or
weight adjustments may be needed to ensure clarity of all critical information. The EDP
should be prepared in digital format.
Specific Tasks:
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Verify that the project limits, project route, crossroads, and streams have been
identified. The existing right of way and centerline must also be shown on the base
map. Coordinate any missing geometric information or mapping deficiencies with
the Project and Environmental Studies Section before the EDP is prepared. All
deficiencies must be documented by the Drainage Engineer.
Obtain and review available contour mapping, highway plans/microfilm highway
plans, and drainage plans from adjacent municipalities, townships, and county
agencies. Identify those drainage features (i.e. storm sewers, culverts etc.) which may
not be shown on the existing CADD topography. Coordinate the need for
supplemental survey with the Project and Environmental Studies Section (i.e. sewer
location, inverts, sizes, etc.) and review survey data as it is obtained.
Use the attached drainage legend for preparing the EDP's. This legend is consistent
with IDOT CADD standards. Refer to and use the drainage survey notes to develop
the EDP.
ACEC-Illinois / IDOT Drainage Seminar 2014
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LDS Task Descriptions
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Use the HA as a guide to interpret the location of the drainage divides on the EDP.
Review all available information (contour mapping, cross sections, HA maps,
municipal sewer maps and field review) to interpret sub-divides and delineate the
tributary drainage areas per outlet. Number all outlets (low flow outlets may not be at
the same location as the flood flow outlets) for reference in Location Drainage Study
Section 2-02. In cases where the HA or USGS Quadrangle map must be used to
complete the tributary drainage area, a separate exhibit showing this drainage area
shall be included in the calculations.
Use the appropriate FIS FIRM maps and transfer the floodplain and floodway
boundaries to the EDP. The floodplain boundaries should be based on the profile
data supplied by FEMA. Transfer of the floodway can be accomplished by scaling.
The limits of the floodplain and floodway boundaries must be shown within the
proposed right of way.
Identify all sewers (types), label sizes, and show direction of flow. Identify all
culverts and label types and sizes. Inverts for crossroad culverts and sewer outfalls
should also be shown. The major drainage features should be numbered for reference
in Location Drainage Study Section 1-03.
Add north arrow, title, and scale to all plan sheets. The drainage legend should
appear on the first plan sheet at a minimum.
Show the location of all field tile within the proposed right of way. Follow
procedures provided in Section 2-202.01 in the Drainage Manual.
Conduct "plan in hand" field review to verify interpreted drainage divides per outlet
and resolve identified inconsistencies per review of EDP’s by other agencies.
Deliverables:
1.
Exhibit 1-00b, Existing Drainage Plan to be folded and provided within pockets
inside the Location Drainage Study.
ACEC-Illinois / IDOT Drainage Seminar 2014
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LDS Task Descriptions
Identified Drainage Problems
Description:
This task involves the documentation of identified drainage problems throughout the
project limits. Identified drainage problems are generally categorized as routine
maintenance or highway related. Highway related problems occur on or off the highway
right of way. The Drainage Engineer should also determine if IDOT, or other entities, are
responsible for corrective measures. Refer to Section 2-203 of the IDOT Drainage
Manual for additional information.
Specific Tasks:
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IDOT personnel will research IDOT records and provide, if available, the Drainage
Engineer with the location and description of any identified drainage problem.
The Drainage Engineer will also be responsible to document those drainage problems
not identified by IDOT personnel, but discovered through site investigations, local
coordination, and/or local testimony.
Screen out all identified drainage problems that are due to maintenance issues and
inform IDOT, Hydraulics. Hydraulics will provide written notification to IDOT,
Bureau of Maintenance.
Review the documentation for the identified drainage problems not related to
maintenance issues and request any additional information, if available, that may be
needed to define the problem, identify the cause, and develop a solution. This
information may include additional IDOT records, topographic mapping, survey data,
local testimony or records.
Define the factors leading to the drainage problem and determine who is responsible
for corrective measures.
Depending on the complexity of the identified drainage problem, it may be necessary
to evaluate alternatives and determine the most cost-effective solution. This
evaluation would be completed as part of the Drainage Alternatives and documented
in Section 2-05 of the Location Drainage Study. Any recommended solution would
be documented in Section 2-07 of the Location Drainage Study, and on the Proposed
Drainage Plan, Exhibit 2-00a.
Deliverables:
1.
2.
Location Drainage Study text, Section 1-01.
A specific, recommendation/solution noted in Section 2-07 and/or Section 2-05.
ACEC-Illinois / IDOT Drainage Seminar 2014
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LDS Task Descriptions
Identified Base Floodplains
Description:
This task involves the identification and documentation of existing floodplains and
floodways within the project limits. An exhibit will be prepared to show the project with
respect to the existing floodplains and floodways. The base map for the exhibit will be
copies of the National Flood Insurance Rate Map (FIRM).
Specific Tasks:
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Use the Flood Insurance Rate Map (FIRM) for each county and community crossed
by the project limits. The FIRM is available from the Federal Emergency
Management Agency’s (FEMA) Map Service Center website.
A separate exhibit should be developed for each community and county crossed by
the project limits. The base map for each exhibit should be the FIRM. The exhibits
should show the project limits, with the project route and crossroads labeled. The
north arrow, scale, map key and map cover page should all be included on the exhibit.
The map cover page will include the community and panel numbers and the effective
date.
Deliverables:
1. Exhibit 1-02a Flood Boundary and Floodway Map or Flood Insurance Rate Map.
2. Location Drainage Study text, Section 1-02.
ACEC-Illinois / IDOT Drainage Seminar 2014
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LDS Task Descriptions
Major Drainage Features
Description:
This task involves the compilation of data to enable the Hydraulic Analysis to be
developed for the existing and proposed conditions for the following Major Drainage
Features:
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Bridges
Major Culvert Crossings
Pump Stations
Reservoirs/Detention Facilities
Depressed Roadways (Subways)
Channels and/or Zone A Floodplains
The results of the Hydraulic Analysis for existing conditions will be included in Section
1-03 of the Location Drainage Study.
The results of the Hydraulic Analysis proposed conditions will be included in Section 207.2 of the Location Drainage Study.
The level of Hydraulic Analysis will depend on the scope of work and project specific
conditions of the Major Drainage Feature.
Refer to Sections 2-204 and 2-309 of the IDOT Drainage Manual for additional
information.
Bridges
Specific Tasks:
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If required, a separate Hydraulic Report (HR) will be prepared in accordance with
“Content of Hydraulic Report”.
From the HR, include the Waterway Information Table (WIT) in the Location
Drainage Study.
If no HR and other data available such as FIS, prepare WIT.
Provide input regarding clearance, freeboard, roadway and bridge deck profile
requirements, overtopping (if any), high water elevations, and flooding under existing
conditions.
Identify and define constraints that substantiate the hydraulic design variations to be
evaluated.
Deliverables:
1. Exhibit 1-03.1a WIT
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LDS Task Descriptions
2. Section 1-03 Narrative summary of the hydraulic performance (limited to one or two
paragraphs) under existing conditions. Discuss waterway opening, overtopping,
freeboard, clearance, flooding, scour, etc.
3. Section 2-07.2.1 Narrative summary of the hydraulic performance (limited to one or
two paragraphs) for proposed conditions. Discuss waterway opening, overtopping,
freeboard, clearance, flooding, scour, etc.
Major Culvert Crossings
Definition of Major Culver Crossing
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Single or multi barrel culverts with a combined end area opening greater than 7.5
square feet (0.7 square meters), or,
Single or multi barrel culverts regardless of the combined end area opening when the
Major Culvert crossing drains 20 acres or more (8.1 hectares or more) in an urban
area and 200 acres or more (81 hectares or more) in a rural area when the scope of the
roadway work is new construction, or,
Single or multi barrel culverts regardless of combined end are opening located within
an identified base floodplain or flood of record as shown on the General Location
Drainage Map.
Any culvert associated with an identified drainage problem.
Specific Tasks:
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Determine tributary area, land type and cover, time of concentration, etc. on an
exhibit and include supporting calculations.
Determine discharges based upon Drainage Manual Procedures.
Prepare WIT for existing conditions.
Review results of analysis for consistency with pertinent data (i.e. Flood Insurance
Study data, known flood elevations, etc.)
Hydraulic Analysis for proposed conditions.
Provide a plan and profile exhibit showing existing and proposed conditions for the
major culvert crossing.
Provide input to Project and Environmental Studies Section for evaluation of the
geometrics meeting freeboard criteria, if it applies and if overtopping condition exists.
Complete WIT for proposed conditions
Deliverables:
1. Exhibit 1-03.1a WIT
2. Section 1-03 Narrative summary of the hydraulic performance (limited to one or two
paragraphs) under existing conditions. Discuss waterway opening, overtopping,
freeboard, clearance, flooding, scour, etc.
3. Section 2-07.2.2 Narrative summary of the hydraulic performance (limited to one or
two paragraphs) for proposed conditions. Discuss waterway opening, overtopping,
freeboard, clearance, flooding, scour, etc.
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LDS Task Descriptions
4. Major culvert crossing Hydraulic Package which includes a narrative, location exhibit
showing drainage area, exhibit showing Major Culvert Crossing on plan and profile,
hard copy of hydrology and hydraulics backup calculations, electronic copies (on CD)
of hydrology and hydraulics backup calculations, and WIT.
Pump Stations
Specific Tasks:
If required, a separate Pump Station Hydraulic Report (PSHR) will be prepared in
accordance with Chapter 13-Pumping Stations contained in the Drainage Manual.
Deliverables:
1. Section 1-03 Narrative summary of the hydraulic performance under existing
conditions.
2. Section 2.07.2.3 Narrative summary of the hydraulic performance for proposed
conditions.
Reservoirs/Detention Facilities
Description: Reservoirs/Detention Facilities basically refer to existing, man-made, open
detention basins which may be impacted by the proposed actions of the highway
improvement. Refer to Storm Water Detention Task for the specific work tasks for those
cases where a detention facility is proposed when there is no existing one.
Specific Tasks:
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Consider alternatives to avoid or minimize any impacts to the existing facility and
provide the recommended alternative.
Review all available hydraulic information regarding the design of the existing
facility, such as size, volume of storage, normal and high water surface elevations,
release rates and flood flow (overflow) route.
If there is no information available regarding the design of the facility, determine
(under existing conditions) the storage volume, water surface elevation, and release
rate in accordance with the methods described in the Drainage Manual for the 2, 10,
50, and 100 year events. Determine the flood flow (overflow route).
Determine the storage volume, water surface elevation and release rate in accordance
with the methods described in the Drainage Manual for the 2, 10, 50, and 100 year
events when the proposed highway improvement impacts the existing facility. Verify
if the flood flow (overflow) route is maintained.
Determine significant impacts, if any, to the upstream and/or downstream properties
regarding increased flood flows and/or increased flood stages (water surface
elevations) if the proposed highway improvement impacts the facility. Coordinate
with the Project and Environmental Studies Section, the significant impacts, for the
purpose of reconsidering the proposed scope of work to the highway.
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LDS Task Descriptions
Deliverables:
1. Section 1-03 Narrative summary of the hydraulic performance under existing
conditions.
2. Section 2.07.2.4 Narrative summary of the hydraulic performance for proposed
conditions.
3. Calculations
Depressed Roadways (Subways)
Description: A subway condition is defined for depressed roadways and depressed
underpasses where ponded water can be removed only through the use of a storm sewer
gravity flow system or a pump station. The storm sewer system is evaluated and/or
designed for a 50 year storm frequency and checked for a 100 year storm frequency. If
the storm sewer system draining the subway leads to a Pump Station, refer to Major
Drainage Features – Pump Stations for the appropriate drainage tasks.
Specific Tasks:
Depending on the history of flooding (if any) and/or scope of roadway work at the
subway, an evaluation may be necessary to determine the following:
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Review all available pavement flooding information such as the number of
occurrences and depth of flooding.
Determine the drainage area to the subway. Evaluate limiting the area draining to the
subway through the use of berms or other structural measures.
Determine the hydraulic grade line (HGL) for the outlet storm sewer system draining
the subway for existing conditions and for proposed conditions.
Evaluate the roadway profile with respect to the HGL. 2’ freeboard for 50-yr storm
should be provided.
Determine the most cost effective solution such as maintain the existing subway
system, provide revisions for new outlet storm sewer design, provisions for storm
water detention, and/or roadway profile modifications to achieve a higher level of
design frequency protection for the subway.
Deliverables:
1. Section 1-03 Narrative summary of the hydraulic performance (limited to one or two
paragraphs) under existing conditions.
2. Section 2.07.2.5 Narrative summary of the hydraulic performance (limited to one or
two paragraphs) for proposed conditions.
3. Calculations
ACEC-Illinois / IDOT Drainage Seminar 2014
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LDS Task Descriptions
Channels and/or Zone A Floodplains
Definition:
Natural or manmade (such as a chute, flume, spillway, etc.) channels apply to any
conveyance in which flowing water has a free surface subjected only to atmospheric
pressure. The flow in a channel is produced under the influence of gravity. The energy
available is due to the elevation difference from one section to another section of the
channel. Channels may be either lined or unlined. When the highway parallels or
crosses the channel the waters carried by the channel mush be conveyed in a manner
which will minimize the effects of any highway encroachments or highway restriction.
Specific Tasks
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Show the location of the existing channel on the EDP. On the EDP, plot the existing
channel bottom slope, and provide cross sections at appropriate locations to describe
the existing channels size and type.
Show the proposed scope of drainage work the existing channel on the PDP. On the
PDP, plot the proposed channel bottom slope and provide cross sections at
appropriate locations to describe the proposed channel, size, type, lining, etc.
Based on the hydrologic and hydraulic methods described in the Drainage Manual,
provide calculations showing velocity, discharge, and water surface profiles for the 2,
10, 50 and 100 year events for existing and proposed conditions.
If the average channel velocity and/or downstream discharge rate for the 10, 50 and
up to the 100 year event is increased by ten (10) percent or more, revise the proposed
channel improvements to meet these described criteria.
Zone A Floodplains are unstudied and require similar techniques to define 10, 50,
100, and 500 or over-topping events.
Deliverables:
1. Section 1-03 Narrative summary of the hydraulic performance under existing
conditions.
2. Section 2-07.2.6 Narrative summary of the hydraulic performance for proposed
conditions.
3. Calculations.
ACEC-Illinois / IDOT Drainage Seminar 2014
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LDS Task Descriptions
Design Criteria
Description:
This task involves documentation that the highway system meets certain design criteria as
specified in Section 2-01 of the Location Drainage Study and providing justification for
those cases in which it does not. Refer to Section 2-301 of the IDOT Drainage Manual
for additional information.
Specific Tasks:
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Review design criteria and complete Section 2-01 of the Location Drainage Study.
For those cases where design criteria is not met, the Drainage Engineer should
coordinate those cases with the Project and Environmental Studies Section. The
Project and Environmental Studies Section should provide written documentation for
non-compliance of the design criteria to IDOT/Hydraulics Section for concurrence
The Drainage Engineer shall present non-compliance of freeboard and clearance
design criteria at the FHWA meeting. Provide meeting minutes.
IDOT/Hydraulics Section will process design exemptions as required.
Deliverables:
1. Section 2-01 Design Criteria with justification for non-compliance of design criteria
for those cases not meeting design criteria.
2. FHWA meeting minutes included in Appendix C.
ACEC-Illinois / IDOT Drainage Seminar 2014
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LDS Task Descriptions
Outlet Evaluation
Description:
This task involves the evaluation of existing outlets to determine their suitability for
continued use and sensitivity to increases in rate and volume of runoff. The outlets to be
evaluated are identified in Existing Drainage System, Section 1-00 of the Location
Drainage Study. Outlets are typically defined as locations where runoff exits the right of
way as concentrated flow (i.e., sewers, ditches, streams, etc.). Some cases involving
reinstatement of sheet flow, especially in urbanizing areas, may also require an outlet
evaluation to determine the potential impact to downstream properties. Refer to Section
2-302 of the IDOT Drainage Manual for additional information.
Sensitivity of an existing outlet involves determining if the outlet can accept increases in
rate, volume of runoff and changes in water quality, without impacts to downstream
properties. Generally, all storm sewers, combined sewers and field tiles are considered
sensitive.
Specific Tasks:
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Use data obtained during the development and coordination of the Existing Drainage
Plans and Identified Drainage Problems to qualitatively evaluate whether each outlet
is suitable for continued use, sensitive, or unsuitable. This data may include written or
verbal input on the design capacity of the outlet, type of outlet, downstream
sensitivity, drainage or flooding problems, field observations, and the location of
wetlands or other environmentally sensitive areas. Other data to be reviewed includes
local ordinances, survey data, highway plans or sewer atlases. Suitable and nonsensitive outlets require no further evaluation.
Document the location and source of unsuitable and sensitive outlets in Section 2-04
of the Location Drainage Study. The source can be derived from review of the
available data.
Perform further quantitative evaluation of unsuitable and sensitive outlets, if
necessary. The evaluation may include but is not limited to:
1. Determination if there is a measurable increase in runoff as a result of the
proposed improvement.
2. Analysis of the existing outlet with proposed flow rate to determine potential
impacts.
3. Analysis of the capacity of the existing drainage system.
4. Analysis of depressional storage areas, ponds or wetlands to determine potential
increases in water surface elevations or impacts of increased volume of runoff.
ACEC-Illinois / IDOT Drainage Seminar 2014
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LDS Task Descriptions
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Based on results of the evaluation, develop feasible, cost effective recommendations
in accordance with IDOT policies, practices and procedures. The recommendations
should consider cost, cost participation (if any), right of way requirements, and
consistency with scope of the improvement. The recommendations may include but
are not limited to:
1. Maintaining the existing outlet
2. Providing storm water detention. Detailed analysis is included in Storm Water
Detention, Section 2-03 and Proposed Drainage Plans, Section 2-07 of the
Location Drainage Study.
3. Developing concept plans for an outlet improvement or utilization of an alternate
outlet which may entail rerouting or diversions. Detailed analysis is included in
Proposed Drainage Plans, Section 2-07 of the Location Drainage Study.
Document the evaluation and preferred recommendation for the unsuitable or
sensitive outlets in Section 2-02 of the Location Drainage Study.
Deliverables:
1. Supporting calculations for the evaluation of outlet capacities and improvements (if
necessary). These calculations shall be included in Appendix D of the Location
Drainage Study.
2. Section 2-02 of the Location Drainage Study.
ACEC-Illinois / IDOT Drainage Seminar 2014
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LDS Task Descriptions
Storm Water Detention Analysis
Description:
This task involves the evaluation of detention requirements in accordance with Section 1304.03 of the Drainage Manual Storm Water Storage. Justification should be included to
support the findings of either providing detention or omitting it. Refer to Section 2-303
of the IDOT Drainage Manual for additional information.
Specific Tasks:
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Determine storage volume required based on IDOT policy for those outlets for which
storm water detention is recommended in Outlet Evaluation task. This is performed
on an outlet-by-outlet basis.
Consider local ordinance requirements for storm water detention.
Develop a concept plan for providing the required storage volumes for those reaches
draining to outlets as determined in the Outlet Evaluation task. Consider the potential
storage volume incidental to proposed drainage structures, new laterals and
extensions. Also determine if a “closed” or “open” storage facility is required. If
detention cannot be provided cost effectively within the highway right-of-way, then
off-site detention should be considered
Refine concept plan and develop concept size and location drawings for storage
facilities. Storage pipes and oversized sewers should be shown on both plan and
profile views of the Proposed Drainage Plan. Plot the HGL for the design storm
frequency (usually the 10 or 50 year event). Check the 100 year event by plotting the
HGL for the 100 year event.
Where open detention is proposed, templated cross sections should be revised to
show locations of oversized ditches or storm water detention basins. These cross
sections shall be included in Appendix D. Oversized ditches for detention should be
shown on the PDP with the size, limits, design high water and design release rate.
Check the 100 year event.
Control structure schematics should be developed and the design data included in
Appendix D. The control structure schematics should be shown on the Proposed
Drainage Plan or on a separate exhibit if necessary. Low and overflow elevations are
to be shown as is proposed freeboard if applicable.
Deliverables:
1.
2.
3
4.
Section 2-03 Storm Water Detention Analysis.
Detailed calculations for the storage required and storage provided should be
included in the Location Drainage Study Appendix D.
Site concept plan and control structure schematics (shown on PDP).
Plot of HGL (shown on PDP).
ACEC-Illinois / IDOT Drainage Seminar 2014
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LDS Task Descriptions
Right of Way Analysis
Description:
This task involves a determination of the drainage right of way and easement
requirements. The proposed drainage improvements should be evaluated to see if
additional right of way or drainage easements are needed. Refer to Section 2-304 of the
IDOT Drainage Manual for additional information.
Specific Tasks:
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Review the proposed roadway plan and templated cross sections and how they relate
to the existing right of way. Review the right of way and easement needs for outlet
pipes, pump stations, ditch drainage, culvert extensions, and detention ponds, and
floodplain compensatory storage.
Tabulate the right of way and easement requirements including stations and offsets.
Coordinate the right of way and easement requirements with the Project and
Environmental Studies Section.
Deliverables:
1. Section 2-04 of the Location Drainage Study.
ACEC-Illinois / IDOT Drainage Seminar 2014
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LDS Task Descriptions
Drainage Alternatives
Description:
This task involves the qualitative analysis of feasible alternative drainage concepts and
recommendation of a preferred drainage alternative. The drainage alternatives are
identified during the development of the proposed drainage plans. The level of
evaluation required is dependent on the scope and complexity of the project. Refer to
Section 2-305 of the IDOT Drainage Manual for additional information.
Specific Tasks:
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Develop drainage alternatives (if any) and determine the level of evaluation required.
Perform a qualitative evaluation of the drainage alternatives consistent with IDOT
policies, practices and procedures. Items to consider include reinstatement of existing
drainage patterns, right of way requirements, best management practices (bmp),
consistency with scope of improvement, and cost. For all diversions proposed it is
mandatory to discuss alternatives to reinstate the existing drainage patterns.
Document the evaluation of drainage alternatives and the preferred recommendation
in Section 2-05 of the Location Drainage Study.
Deliverables:
1.
Section 2-05 of the Location Drainage Study.
ACEC-Illinois / IDOT Drainage Seminar 2014
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LDS Task Descriptions
Local and other Agency Coordination
Description:
The purpose of this task is to encourage involvement by the local and other agency(ies) to
document comments, drainage concerns, and concurrence with the EDP and PDP. Refer
to Sections 2-205 and 2-307 of the IDOT Drainage Manual for additional information.
Specific Tasks:
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IDOT makes initial contact with local and other agency(ies) regarding available
drainage data, ordinances, and any identified drainage problems. Follow-up letter
will be sent out by IDOT. Any follow-up phone calls can be made by the Drainage
Engineer at his/her discretion.
IDOT will send out the EDP and PDP to the agency(ies) for review and comments.
The Drainage Engineer will make arrangements for a coordination meeting with the
agency(ies). A meeting agenda should be prepared and distributed prior to the
meeting.
At the coordination meeting, the Drainage Engineer will present the EDP, the PDP (if
not completed, a conceptual plan is required), preliminary drainage alternatives (if
any), and drainage issues (if any) for discussion.
The Drainage Engineer shall prepare a meeting summary and document all relevant
comments, concerns and drainage issues in a concise manner. Documentation of
concurrence with the EDP and PDP is desired.
The Drainage Engineer should prepare a follow-up disposition to the comments,
and/or update the EDP and/or PDP as required in a timely manner. Notify participants
of action taken.
If additional meetings are required, repeat the process.
Deliverables:
1.
2.
Location Drainage Study text, Section 2-06.
Copy of all pertinent correspondence such as telephone logs, letters and meeting
minutes inserted in Location Drainage Study Appendix C.
ACEC-Illinois / IDOT Drainage Seminar 2014
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LDS Task Descriptions
Proposed Drainage Plan
Description:
This task involves the preparation of a Proposed Drainage Plan (PDP), with drainage
symbols and notes on exhibit(s), and appropriate wording in the Location Drainage Study
text, which fully describes the proposed drainage concept. Both aerial imagery and
contour mapping should be used as the PDP base map, along with existing CADD
topography and proposed geometric plan superimposed. The PDP should be prepared in
a digital format. Refer to Section 2-308 of the IDOT Drainage Manual for additional
information. The purpose of the PDP is to illustrate the proposed drainage features and
overall concept to the extent necessary to identify:
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Reinstatement of the existing drainage patterns;
Sub areas to each outlet;
Low and overflow (flood) flows;
Diversions (shown as cross hatched);
Potential utility conflicts;
Maintain, replace or construct storm sewers, crossroad and appurtenant culverts, and
special drainage structures;
Maintain, re-grade, or construct ditches and/or swales;
Location for proposed storm water detention.
Specific Tasks:
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The Drainage Engineer should use the EDP, proposed geometric plan, existing and
proposed roadway profiles, templated roadway cross sections, and any available
contour mapping to develop the PDP Exhibit 2-00a. The PDP should be developed
utilizing the drainage symbols attached with the EDP tasks. These drainage symbols
are consistent with the EDP Tasks.
Verify that the project limits, project route, crossroads, and streams have been
identified. The existing right of way and centerline along with the anticipated
proposed right of way or drainage easements must also be shown on the base map.
Coordinate any missing geometric information or mapping deficiencies with the
Project and Environmental Studies Section before the PDP is prepared. All
deficiencies must be documented by the Drainage Engineer.
The Drainage Engineer should utilize the EDP and the templated cross sections to
define the proposed tributary areas (sub divides) to each outlet, and to identify
diversions. All outlets, including new outlets, if any, (low flow outlets may not be at
the same location as the flood flow outlets) should be identified and numbered for
reference in Location Drainage Study Section 2-02.
Identify regraded ditch locations. For regraded ditches, provide beginning and ending
stations. Identify proposed ditch and proposed swale locations. For proposed
ditches, identify beginning and ending stations and proposed ditch slope. Proposed
ditches should be standard ditches, especially when additional right of way is
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LDS Task Descriptions
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requested for drainage purposes. Ditches required for storm water detention are
described in Storm Water Detention Analysis. All technical data utilized in the
design of the ditches/swales shall be included in the Location Drainage Study,
Appendix D.
Identify all locations where sheet flow is to be reinstated or proposed.
Existing storm sewers to be maintained must be identified with beginning and ending
stations. Existing storm sewers to be abandoned must be identified with beginning
and ending stations. Proposed storm sewers are to be designed (sized) based on the
IDOT Drainage Manual methods. The size, inverts, and slopes of the proposed storm
sewer systems are to be provided on the PDP exhibit(s). Plan and profile of the
proposed storm sewer runs (not lateral extensions) are required. The Hydraulic Grade
Line (HGL) for the design storm frequency must be plotted on the storm sewer
profile. Storm sewers required for detention are described in Storm Water Detention
Analysis. A detailed sketch of any special drainage structure must be provided on the
PDP or on a separate exhibit. All technical data utilized in the design of the storm
sewers shall be included in the Location Drainage Study, Appendix D.
The Drainage Engineer is to indicate the proposed concept (i.e. maintain, replace,
extend, etc.) for cross road and appurtenant culverts that do not qualify as Major
Culvert Crossings. The proposed sizing (if any) of Non-Major Culvert Crossing are
performed in Phase II. The Drainage Engineer shall ensure the proposed culvert
concept is compatible with the existing and/or proposed right of way
Add north arrow, title, and scale to all plan sheets. The drainage legend should
appear on the first sheet at a minimum. The roadway scope of work (construction,
reconstruction, and/or rehabilitation) must be shown on the plan sheets.
Prepare Location Drainage Study Text, Section 2-07.1 which fully describes the
proposed drainage plan.
Deliverables:
1.
2.
3.
Location Drainage Study text Section 2-07.
Calculations and technical data used in the design/sizing of the proposed drainage
system to be included in Appendix D of Location Drainage Study.
Proposed Drainage Plan, Exhibit 2-00a, to be folded and provided within pockets
inside the Location Drainage Study.
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LDS Task Descriptions
Water Quality Best Management Practices (BMPs) Permanent Measures
Description:
This task involves documentation that the designer has considered options for water
quality Best Management Practices (BMPs) and incorporated these practices into the
Proposed Drainage Plans as specified in Section 2-08 of the Location Drainage Study.
The section also provides opportunity to provide justification for those cases in which the
incorporation of BMPs is limited.
Specific Tasks:
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Identify regulatory BMP requirements.
Coordinate with regulatory agencies and other involved agencies. Coordinate with
IDOT departments as needed.
Identify opportunities for green infrastructure BMPs in the project area, including
improving existing facilities and establishing new BMP measures.
Identify opportunities for grey infrastructure BMPs where green infrastructure is not
an option. This can also include improving existing facilities and establishing new
BMP measures.
Identify the need for additional Right-of-Way (ROW) or permanent easements to
allow for implementation of the selected BMPs.
Identify the locations of the proposed BMPs on the Proposed Drainage Plans.
Identify the locations of the necessary additional ROW and permanent easements on
the Proposed Drainage Plans.
Provide adequate guidelines for the Phase II designer to comply with USACE and
NPDES requirements and incorporate the proposed BMPs into the Phase II plans.
Complete Section 2-08 of the Location Drainage Study.
Deliverables:
1. Section 2-08 Water Quality Best Management Practices (BMP) Permanent Measures.
2. Inclusion of proposed BMPs on Proposed Drainage Plans.
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LDS Task Descriptions
Floodplain Encroachment Evaluation
Description:
This task involves the evaluation of encroachments on Regulatory Floodways and
unstudied Zone A floodplains. Regulatory Floodplains are those 100 year frequency
floodplains which are mapped by the Illinois Department of Natural Resources – Office
of Water Resources (IDNR-OWR) and/or the Federal Emergency Management Agency
(FEMA).
Additional guidelines for conducting this evaluation and assessment are contained in
Chapter 3 of the Drainage Manual and in Section 26-7 of the Bureau of Design and
Environment Manual (BDE). Refer to Section 2-306 of the IDOT Drainage Manual for
additional information.
Specific Tasks:
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Obtain and review data. This data includes the roadway plan and profile, cross
sections, and the Flood Insurance Study data, if available.
Determine the appropriateness of the proposed action or work and provide
recommendations for plan revisions or alternatives to avoid a significant
encroachment. IDOT policy is to avoid longitudinal encroachments when practical
and minimize the extent of encroachment if it is unavoidable.
Review and consider IDNR-OWR permit requirements and local ordinances.
Perform a qualitative evaluation of the extent and degree of encroachment in
accordance with Executive Order 2006-05. If the proposed work does not cause
significant impacts, then complete the evaluation by documenting the location in
Section 3-00 of the Location Drainage Study.
If there are potentially significant impacts, proceed with the additional tasks described
below:
 Perform hydraulic analysis for the proposed conditions to determine the
magnitude of changes in water surface elevations for the 10 year and 100 year
flood frequencies.
 Inspect the floodplain and determine if there are any buildings or structures
located in the floodplain subjected to the proposed action or work.
 Inspect the floodplain to determine if increases in flood heights could result in
significant damage not expected under current conditions.
 Prepare a horizontal plan of the floodplain encroachment. Show the floodplain
boundaries (on contour mapping if available), adjacent to and including the
roadway within the limits of the floodplain encroachment.
 Prepare cross sections of the floodplain. Using the roadway cross sections show
the layout of the floodplain boundaries adjacent to and including the roadway
within the limits of the floodplain encroachment. These cross sections should
include: normal water surface elevation, 10 year flood elevation, 100 year flood
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LDS Task Descriptions
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elevation, floodplain and floodway boundaries, and areas of fill/cut within the
floodplain and floodway.
 Compute encroachment volumes between the normal and 10 year flood elevation,
and between the 10 year and 100 year flood elevations within both the floodway
and floodplain. Note that it is IDOT policy to provide compensatory storage for
fill anywhere in the floodplain associated with a longitudinal encroachment and
fill in any floodway outside the City of Chicago.
 Determine a suitable means to provide compensatory storage. This includes the
evaluation of alternate sites, the development of a plan schematic and site cross
sections, and determination of compensatory storage volume provided.
If the qualitative evaluation shows that there are minimal or insignificant changes in
the flood heights or flood limits, complete the evaluation by documenting the location
in Section 3-00 of the Location Drainage Study. For most cases the evaluation does
not extend beyond this step. However, if the evaluation shows that there is still a
potentially significant impact proceed below:
 Coordinate with IDNR-OWR and local agencies to determine degree of
significance of the potential impact on the floodplain.
 Perform a Risk Assessment in accordance with Section 3-004.02 of the IDOT
Drainage Manual. This may lead to the reiteration of the activities described
above for design alternates. If the results of the evaluation show that the
impact is significant, proceed below, otherwise, document the location in
Section 3-00 of the Location Drainage Study and complete the Permit
Summary Form and Attachment A, if required.
 If a significant impact remains and the proposed action is the only practicable
alternative, a Risk Analysis must be performed in accordance with Section 3004.03 of the Drainage Manual. Present the findings at the FHWA monthly
coordination and obtain concurrence of the proposal.
 Document the location is Section 3-00 of the Location Drainage Study and
complete the Permit Summary Form and Attachment A, if required.
Provide support to the Project and Environmental Studies Section to document the
floodplain encroachments in the Environmental Assessment Report or EIS if one is
being prepared for the project.
Deliverables:
1.
2.
3.
Section 3-00 of the Location Drainage Study.
Supporting calculations for the hydraulic analysis, evaluation of encroachment
and determination of compensatory storage volumes. These calculations should
be included in Appendix D of the Location Drainage Study.
Permit Summary Form and Attachment A (included in the Hydraulic Report, if it
is required).
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LDS Task Descriptions
Illinois Department of Natural Resources
Office of Water Resources (IDNR-OWR) Permit
Description:
This task identifies any permit requirements of the IDNR-0WR for construction activity
within designated floodways, floodplains, and Public Bodies of Waters of rivers, streams
and lakes within the State of Illinois. Refer to Section 1-404 of the Drainage Manual for
additional information.
Specific Tasks:
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If the affected river, stream or lake is a Public Body of Water, then an Individual
Permit from IDNR-OWR is required.
If the affected river, stream or lake is not a designated floodway and is a regulatory
floodplain that has a drainage area greater than one square mile, identify the
appropriate Individual or Statewide Permit required.
If the affected river, stream or lake is a designated floodway that has a drainage area
greater than one square mile, identify the appropriate Floodway Permit required. A
completed Permit Summary Form (and its Attachment “A”) is required for each
location involving a floodway. This form and attachment are prepared under the
Floodplain Encroachment Evaluation task or Hydraulic Report task and they must be
included in Appendix C.
Document any coordination with IDNR-OWR regarding permits and include in
Appendix C of the Location Drainage Study.
Deliverables:
1. Location Drainage Study text, Section 4-00.
2. Correspondence with IDNR-OWR, included in Appendix C of the Location Drainage
Study.
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LDS Task Descriptions
Study Assembly
Description:
This task involves the organization, preparation and assembly of the completed Location
Drainage Study. This task follows completion of all previous tasks. Location Drainage
Study revisions should be anticipated and the time required to implement those revisions
are included in the individual tasks. Only the organizational time for those revisions is
included in this task.
Specific Tasks:
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A report cover should be prepared. A draft date on the cover to facilitates
identification of initial and subsequent revisions.
The table of contents should be prepared, with page numbers included.
The necessary appendices should be compiled and separator pages prepared. The use
of contrasting color page for the appendices eases rapid location and identification of
those appendices. Only drainage related documents should be included in Appendix
C and Appendix D. Supporting calculations are included in Appendix D and should
be bound separately if appropriate. Every supporting calculation page must contain
“calculated by” and “checked by” initials.
A draft and Pre-final copy of the Location Drainage Study should be presented to
IDOT.
IDOT will advise on the number of final copies of the Location Drainage Study.
Copy, collate and bind the appropriate number of documents.
Deliverables:
1. Draft, Pre-final, and Final copies of the Location Drainage Study.
2. A CD with PDF prints and live electronic files of the Location Drainage Study
and all supporting calculations, documents, exhibits, etc.
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