ROAD COMMISSION FOR OAKLAND COUNTY
SPECIAL PROVISION
FOR
DEWATERING WELL POINTS
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a. Description.
This work includes all labor, materials, and equipment necessary for designing, constructing,
operating, maintaining and removal of a dewatering system as required to create and maintain
stable excavations to allow for the construction of the box culvert bridge. Dewatering includes
the local lowering of the groundwater table, intercepting seepage, and the disposal of collected
water. The intent of dewatering is to prevent failure or heaving of the bottom of excavation and
to provide for a more suitable stable condition for the box culvert bridge and the box culvert
bedding.
The Contractor is responsible for the design, installation and removal of dewatering system and
shall obtain and comply with all required permits for dewatering.
Note: Contractor is cautioned against overpumping the site due to the potential damage to the
historic barn structure.
b. Materials.
This work shall require the use of the following equipment and system description:
•
Electric Dewatering Pumps. Electric hook up to DTE Energy shall be the Contractor’s
responsibility. Diesel or gasoline dewatering pumps shall not be permitted.
•
Positive Displacement Pumps.
•
Providing at least one spare positive displacement pump onsite at all times during
dewatering operations.
•
Approximately 150 lineal feet of a “horse-shoe” style well point dewatering system.
•
Furnishing, installation, and removal of three (3) observation wells.
Reference to sections shall be in accordance with the numbered section of the “2012 Standard
Specifications for Construction” issued by the Michigan Department of Transportation.
b.
Contractor Qualifications
Dewatering System Designer: Registered professional engineer in the State of Michigan with a
minimum of 10 years of experience in the design of dewatering systems for excavations with
shoring support.
Dewatering System Installer: Experience record including minimum of 10 years of experience
and 5 projects with dewatering systems for shored excavations in similar conditions including
clay overlying pervious soil. Experienced in the installation and operation of similar dewatering
systems as employed by the dewatering plan, including instrumentation and emergency power
systems.
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c.
Submittals
1.
Statement of Qualifications for Dewatering Specialist:
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a.
Provide summary of project experience and references for designer of dewatering
systems.
1)
Include detailed information regarding the name and location of each project, owner of
the project, general contractor, depth of excavations, types of material excavated, depth to
water, means of dewatering, instrumentation methods, and data from instrumentation.
2)
Provide a minimum of three references from Owner or Owner’s Engineer with knowledge
of projects included in the project experience summary, and include current valid contact
information.
2.
Water Control Plan: Submit for review by the Engineer prior to start of any field work. At
a minimum, the Water Control Plan shall include the following:
a.
Names of equipment suppliers and installation subcontractors.
b.
Descriptions of proposed groundwater and surface water control facilities including, but
not limited to, equipment; methods; standby equipment and power supply, means of measuring
inflow to excavations, pollution control facilities, discharge locations to be utilized, and
provisions for immediate temporary water supply as required by this section.
c.
Drawings showing locations, dimensions, and relationships of elements of each system,
including emergency power systems, and specific measures to increase dewatering capacity.
d.
Design calculations demonstrating adequacy of proposed dewatering systems and
components. Calculations shall include the following:
1)
Specific descriptions of well screen design, estimated permeability, well yield, drawdown
and radius of influence, etc., used for design of well systems.
2)
Calculations to demonstrate stability of the excavation against uplift or heave.
e.
Surface water control and drainage installations.
f.
Locations and types of monitoring systems. Include specific summary of the anticipated
pore pressures and groundwater levels for each monitoring device so that monitoring results
can be compared to conditions anticipated in the development of the Water Control Plan.
g.
Proposed methods and locations for disposing of removed water.
h.
Any treatment system in place to meet discharge quality criteria if applicable.
i.
If system is modified during installation or operation, revise or amend and resubmit
Water Control Plan.
j.
For Schedule A, submit for review within 15 days of Notice to Proceed.
1)
Engineer will act upon Contractor’s submittal and transmit response to Contractor no
later than 45 days after receipt. Engineer will forward to Owner and US Army Corps of
Engineers (USACE) for review on the Contractor’s behalf. Engineer’s review shall be
conducted and response provided in accordance with 01 33 00 1.03.D and shall reflect the
feedback provided by Owner and USACE.
Note: The dewatering target elevation is El. 900.00. Excess water within the braced excavation
can be accomplished by a local dewatering/pumping system.
d.
Environmental Requirements
1.
Comply with requirements of agencies having jurisdiction.
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2.
Comply with Michigan Department of Health and Human Services for registration,
development, drilling, and abandonment of wells used in dewatering systems.
3.
Comply with permit from MDEQ under the National Pollutant Discharge Elimination
System (NPDES), for construction dewatering discharges from construction sites.
4.
Obtain all necessary permits from agencies with control over the use of groundwater and
matters affecting well installation, water discharge, and use of existing storm drains and natural
water sources.
5.
Maintain compliance with all applicable effluent limitations and other requirements
imposed by the MDEQ or the City regarding the discharge of the waters. All reports required by
MDEQ or other regulatory agencies.
e.
Equipment and Materials
1.
Equipment and materials are at the option of Contractor as necessary to achieve desired
results for dewatering.
2.
Eductors, well points, or deep wells, where used, must be furnished, installed and
operated by an experienced contractor regularly engaged in groundwater control system design,
installation, and operation.
3.
All equipment must be in good repair and operating order.
4.
Standby equipment and materials shall be kept available and in operating condition to
ensure continuous operation.
5.
Electric pump motors, rather than diesel, are required.
f.
Soils Investigation
The results from the soils investigations have been included within the project specifications for
the Contractor’s use in determining the requirements for the dewatering system. Drilling records
from nearby wells have also been included within project specifications for the Contractor’s use.
c. Construction.
1.
Dewatering Systems
a.
Design, install, and operate dewatering systems to bring groundwater to depth of 3 ft. or
greater below lowest point of excavation, prior to beginning excavation and at all times during
excavation, and as necessary to accomplish the following:
1)
To prevent loss of ground as water is removed.
2)
To avoid inducing settlement or damage to existing facilities, completed Work, or
adjacent property.
3)
To establish adequate factor of safety against uplift or instability of excavation bottom.
4)
Install instrumentation prior to beginning excavation, as necessary to demonstrate the
above requirements are met. Provide detailed summary of findings from instrumentation, and
comparison to the expectations of the Water Control Plan, prior to beginning excavation.
5)
Continuously control water during course of construction, including weekends and
holidays and during periods of work stoppages, and provide adequate backup systems to
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maintain control of water until Backfill has been placed, the structure is capable of resisting
hydrostatic force and has been properly leak tested.
6)
Perform dewatering operations in a manner that will protect existing roads, structures,
and utilities. The Contractor shall be solely responsible for preventing damage to roads,
buildings or structures, sewers and other utility installations, pavements, sidewalks, and other
property that may result from Contractor’s dewatering operations.
7)
Immediately repair any structure damaged as a result of the dewatering operations at no
additional costs to the Owner.
8)
Provide sufficient redundancy in each system to keep excavation free of water in event
of component failure.
9)
Provide 100 percent emergency power backup with automatic startup and switchover in
event of electrical power failure.
10)
Provide supplemental ditches and sumps only as necessary to collect water from local
seeps. Do not use ditches and sumps as primary means of dewatering.
11)
The Engineer shall be advised of any changes made to accommodate field conditions.
Upon completion of the dewatering system installation, revise and resubmit information
drawings as necessary to show the installed configuration including grade elevation at the time
wells were installed, well depth, screen lengths, slot size, filter pack grain size analysis, and
depth of pump intake.
12)
Remove system upon completion of construction or when dewatering and control of
surface or ground water is no longer required.
2.
Observation Wells (3) Required
a.
Groundwater Levels: Install and observe observation wells at locations selected by
Engineer. Measure water levels observed in each observation well at least weekly and
whenever the system or component failures are discovered and whenever any event, including
but not limited to flood, storms, changes in water surface elevation of nearby water bodies, may
have caused a change in the groundwater elevation. Observation wells shall be installed in
accordance with the manufacturer’s recommendations.
b.
After groundwater level observation wells are no longer needed for groundwater levels,
abandon observation wells, as required by regulations.
3.
Settlement
a.
Dewatering-Induced Settlement: Establish monuments for monitoring settlement at
locations selected by Engineer. Monitor vertical movement of each settlement monument,
relative to remote benchmark selected by Engineer, at least weekly in accordance with Section
31 80 00, Geotechnical Instrumentation.
4.
Monitoring Flows
a.
Monitor volume of water pumped per calendar day from excavations, as Work
progresses.
Also monitor volume of water introduced each day into excavations for
performance of Work. Monitor flows using measuring devices acceptable to Engineer.
5.
Disposal of Water
a.
Comply with requirements stated in Article 1.4 of this Specification.
b.
Obtain discharge permit for water disposal from MDEQ.
c.
Treat water collected by dewatering operations, to meet effluent limitations and other
requirements as required by MDEQ prior to discharge. It is anticipated that treatment to meet
acceptable levels of Total Suspended Solids (TSS) will be necessary. Levels of other
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contaminants encountered within the groundwater are not expected to exceed permitted
discharge levels.
d.
Discharge water as required by discharge permit and in manner that will not cause
erosion or flooding, or otherwise damage existing facilities, completed Work, or adjacent
property.
Dewatering flows shall be discharged directly through piping and
dewatering/treatment facilities to a receiving stream or storm sewer at a location acceptable to
the City.
e.
Remove solids from dewatering flow treatment facilities and perform other maintenance
of dewatering flow treatment facilities (best management practices) as necessary to maintain
their efficiency.
6.
Protection of Property
a.
Make assessment of potential for dewatering induced settlement. Provide and operate
devices or systems, including but not limited to reinjection wells, infiltration trenches and cutoff
walls, necessary to prevent damage to existing facilities, completed Work, and adjacent
property.
b.
Securely support existing facilities, completed work, and adjacent property vulnerable to
settlement due to dewatering operations. Support shall include, but not be limited to, bracing,
underpinning, or compaction grouting.
c.
Limit lowering of groundwater table outside of excavation to no lower than 5 feet below
the lowest recorded stabilized ground water table, unless lower levels have been agreed to by
Engineer prior to dewatering.
7.
Remediation of Groundwater Depletion
a.
If dewatering reduces quantity or quality of water produced by existing wells, temporarily
supply water to affected well owners from other sources. Furnish water of a quality and quantity
equal to or exceeding the quality and quantity available to well owner prior to beginning the
Work or as satisfactory to each well owner.
d. Measurement and Payment.
The completed work as measured for DEWATERING will be paid for at the contract unit prices
for the following pay items:
Pay Item
Pay Unit
Dewatering Well Points, Mobilization……………………………………………………….Lump Sum
Dewatering Well Points, Furn, Install, Maintain, Remove………………………………..Lump Sum
Dewatering Well Points, Weekly, Maintain…………………………………………………….Weekly
Dewatering Well Points, Mobilization will be measured on an individual lump sum and shall
be based on Plan quantities. Payment of this item shall be payment in full for all costs
associated with furnishing and installing “Dewatering Well Points, Mobilization.”
The following items will not be measured and paid for separately and will include the furnishing
of all labor, materials, and equipment necessary to complete this work, and are included in the
bid item “Dewatering Well Points, Mobilization”:
•
Consist of all preparatory work and operations for the movement of personnel,
equipment, supplies, and incidentals to the project site.
•
Pre-construction costs, exclusive of bidding costs.
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Dewatering Well Points, Furn, Install, Maintain, Remove will be measured on an individual
lump sum and shall be based on plan quantities. Payment of this item shall be payment in full
for all costs associated with furnishing, installation, maintaining and removal of the necessary
well points, monitoring wells, dewatering system, and discharge system.
Dewatering Well Points, Weekly, Maintain will be measured on a weekly basis based on plan
quantities. Payment of this work shall be payment in full for all costs associate with the
maintaining of the dewatering system beyond three weeks of operation.
The following items will not be measured and paid for separately and will include the furnishing
of all labor, materials, and equipment necessary to complete this work, and are included in the
bid item “Dewatering Well Points, Weekly, Maintain”:
•
Furnishing of all labor, materials, and equipment necessary to operate the installed
dewatering system on a weekly (every seven days) basis.