SECTION 31 23 19
DEWATERING AND WASTEWATER HANDLING
PART 1
1.01
GENERAL
SUMMARY
A. This Section includes construction dewatering and wastewater handling as it relates to
performing subsurface construction work, such as excavation, grading, and underground
utilities. This includes waters generated, including chemically contaminated water, contractor
decontamination rinse and wash waters, and accumulated groundwater. The Contractor shall
remove all accumulated waters (includes ground water, stormwater, and other ponded water)
from the work area to accommodate excavation and backfilling, or other construction related
work.
B. Contractor shall provide, operate, and maintain all necessary containment, pumping, storage,
treatment, transfer, and disposal to maintain the site in a workable condition. After treatment
described below Contractor may discharge treated water to the existing sanitary sewer
system.
C. This specification does not include the routine handling, conveyance, and discharge of storm
water that would otherwise be included in and handled by Section 31 25 00 - Erosion and
Sedimentation Control.
1.02
RELATED SECTIONS
A. Section 31 23 00 – Earthwork
B. Section 31 23 02 – Refuse Handling
C. Section 31 23 15 – Sheeting, Shoring, and Bracing
D. Section 31 25 00 – Erosion and Sedimentation Control
E. Section 33 41 00 – Surface Water Drainage
F. Section 35 43 20 – Log Structures
1.03
PERFORMANCE REQUIREMENTS
A. GENERAL
1. Excavations, trenches, and pits shall be kept free of standing water. The Contractor shall
control surface runoff and groundwater so as to prevent collection of water in excavations
and to maintain the workable condition of the site.
2. Contractor shall minimize loss of fines from the soil, prevent damage to adjacent facilities,
utilities, and structures (from dewatering induced settlement), and minimize quantity of
handled water to achieve construction objectives. Dewatering and wastewater handling
and disposal activities that are deemed unnecessary or excessive in order to accomplish
the Work is not permitted and at the Contractor’s sole expense.
1.04
SUBMITTALS
A. Discharge Authorizations and Fees: Submit all Contractor obtained authorizations or permits
associated with construction wastewater handling and discharge. The Contractor shall
record and provide to the Construction Manager any water quality data, invoices from the
City, and payment records.
B. Handling and Discharge Records: The Contractor will measure and maintain dewatering and
discharge records for all pumping and discharge of CSW into the sanitary sewer system.
These records will be presented weekly to the Construction Manager to reconcile CSW
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Port Angeles Landfill Cell Stabilization Project
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§31 23 19
Dewatering and Wastewater Handling
discharge associated with the Monthly Pay Request. These reconciled records will form the
basis for the Monthly Pay Request quantity.
C. Dewatering Plan: The construction methods proposed for construction dewatering and
wastewater handling and discharge shall be submitted to the Construction Manager a
minimum of 30 days prior to commencing dewatering activities. If well points are required for
dewatering, the plan shall be produced by a licensed engineer or hydrogeologist who is
experienced with construction dewatering, and is subject to review and approval by the City
and the Construction Manager. The following shall be included in the Plan:
1. Submit drawings and data showing the method to be employed in dewatering excavated
areas.
2. Material shall include: locations; depth and size of well points and headers; sumps;
ditches; size, length, and location of discharge lines; capacities of pumps and standby
units; and detailed description of dewatering methods to be employed to convey the
water from site to adequate disposal.
3. Include a written report outlining sequencing and methods proposed for dewatering, and
control procedures to be adopted if dewatering problem arises.
4. Detailed description of dewatering procedure and maintenance method.
5. Discharge piping alignment for CSW leading to BioSolids Basin and Sanitary Sewer
discharge.
6. Plans for handling contaminated dewatering fluids
7. Design of settling facilities, oil/water separation facilities, and filters if dewatering water
interferes with CSW.
8. Contingency plans for discharge noncompliance and accidental spills
1.05
QUALITY ASSURANCE
A. The contractor shall attend a pre-construction meeting with the City and/or Construction
Manager to discuss the Dewatering Plan and related activities.
1.06
PROJECT CONDITIONS
A. Existing Utilities: The Contractor shall locate, identify, and protect all existing utilities during
the construction and operation of the construction dewatering system.
B. The Contractor shall be aware that contaminated groundwater could be pumped from any
location on the site.
C. The Contractor may be dewatering refuse contained within the East 304 Cell and Valley Cell.
This is a WAC 173-304 and 173-351 Landfill. Waste is anticipated to include municipal solid
waste, industrial waste, ash, soil, and other wastes consistent with these designations. Some
unqualified waste may be present. If these wastes are uncovered, the Contractor is to notify
the Construction Manager immediately.
D. Project investigation documents have been generated by the City and are available to the
Contractor at their request.
PART 2
2.01
PRODUCTS
MATERIALS
A. The Contractor shall provide pumps, temporary pipes, hoses, containment tanks, plugs, and
all other materials and site controls necessary to bypass existing surface water runoff and
keep clean storm water separate from contaminated water and dewatering water.
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§31 23 19
Dewatering and Wastewater Handling
B. Delete this article if Contractor selects temporary excavation support and protection. Revise
materials if prescribing excavation support and protection system requirements.
C. Materials shall be subject to the review and approval of the Construction Manager within the
Dewatering Plan.
PART 3
3.01
EXECUTION
GENERAL
A. The Contractor shall furnish, install, and operate all necessary equipment to maintain the site
in a workable condition. The control of groundwater shall maintain slope stability and prevent
softening of the bottom of excavations, or formations of “quick” or heaving conditions, or
“boils”. Dewatering systems shall be designed and operated so as to prevent any removal or
flowing of native soils. In the event the native subgrade is compromised as a result of the
Contractor’s dewatering methods, the Contractor shall be fully responsible for restoring the
integrity of the subgrade to stable condition.
B. Disposal of the water shall not cause injury to public or private property, or nuisance to the
public. Sufficient pumping and power equipment in good working condition shall be available
at all times for all emergencies, including power outage, and competent personnel shall be
available at all times for the operation of the dewatering system. Water discharge locations
shall comply with required permits from the City, other local jurisdictions, State and Federal
agencies as appropriate.
C. The dewatering system shall be designed to prevent loss of foundation support to refuse still
in place, adjacent structures, roads, facilities, utilities, underground installations,
improvement, or the sides and slopes of an excavation.
D. The release of groundwater to its static level shall be performed in such a manner as to
maintain the undisturbed state of the natural foundation soils and supported fill soils or
refuse, prevent disturbance of compacted bedding and backfill, and prevent flotation or
movement of structures, pipelines, sewers, and storm Drains.
E. The Contractor shall control and prevent clean storm water run-off from entering
contaminated water collection areas by using surface water controls such as berms, straw
bale, temporary covers, or other means as described in the temporary erosion and
sedimentation control plans and specifications. The Contractor shall use all means and
methods to reduce the total quantity of collected and handled waters and wastewater that
requires handling, treatment and disposal. This includes, but is not limited to: minimizing
exposed depressions and excavation areas; expediting excavation and backfill activities,
particularly in contaminated soil or refuse areas; timing soil and refuse disturbing activities
during dry periods; and covering exposed refuse and contaminated soil (stockpiles) during
wet periods.
F. Water draining from stockpiles of contaminated soils excavated from this site shall be
collected by the Contractor and conveyed to the water treatment system.
G. The Contractor shall dewater soil and refuse to be placed in the 351-Compliant Landfill Cell
such that soil and refuse is not free-draining at the time of transport to placement in the 351Compliant Landfill Cell.
H. Prior to any excavation below the ground water table, place system into operation to lower
water table as required and operate it continuously until excavation zone is dewatered and a
steady state exists to assure the work area is dewatered.
3.02
REMOVAL OF COLLECTED (WASTE) WATERS
A. As approved or directed by the Construction Manager, the Contractor shall remove water
from depressions, excavations, or other areas holding collected contaminated water,
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§31 23 19
Dewatering and Wastewater Handling
including groundwater and stormwater, or other (waste) water under any of the following
conditions:
1. Water removal is required to perform excavation activities, particularly for removal of
refuse and uncontrolled fills;
2. Water removal is required to minimize the moisture content of excavated soils or refuse;
3. Water removal and control is necessary to prevent damage to adjoining structures and
facilities;
4. Water removal is required to perform site restoration or installation of utilities,
foundations, including backfill and compaction, grading and paving;
5. Water removal is necessary to avoid costly project delays or change to work activities
and schedule; and
6. Water removal is required to prevent a discharge of turbid water and/or violation of the
construction (NPDES) permit.
B. Water collection and conveyance from excavations will be initiated from a low point of
collection area. If necessary to reduce turbidity, water removed from excavated areas shall
be discharged such that it shall pass through a sediment control device prior to discharge into
the sanitary sewer. Sediment control devices include sediment traps, tanks, sumps, and the
Abandoned Biosolids Basin.
3.03
CSW TREATMENT
A. All collected waters may require sedimentation to meet the City of Port Angeles Discharge
Authorization criteria. The operation of the sedimentation and compliance with the
requirements and restrictions of the discharge authorization are solely the Contractor’s
responsibility.
B. Removal of free product: Prior to discharging CSW, including dewatering water, to the
sanitary sewer the Contractor shall remove visible free-floating product, sheen, or emulsion
using absorbent pads, booms, vacuum, or other approved devices. Maintenance and
replacement of absorbent materials is the responsibility and expense of the Contractor.
C. The Contractor shall utilize pumping and conveyance equipment, swales and berms, and
other equipment and materials necessary to prevent loss or discharge of wastewaters. Loss
or discharge of wastewater includes intermingling with stormwater. The Contractor shall
provide and maintain sufficient equipment and materials to ensure effective and efficient
operation of construction dewatering and wastewater handling.
3.04
CSW AND DEWATERING WATER DISCHARGE AND DISPOSAL
A. CSW and dewatering water may be discharged to the existing sanitary sewer system in
accordance with the City of Port Angeles sewer permit. The Contractor shall be responsible
for coordinating with the City to direct discharge to the sewer system.
B. The Contractor may use the Biosolids Pond and Leachate Pond as temporary CSW and
dewatering water storage. These ponds require re-lining as described in the drawings.
C. The Contractor shall pump collected contaminated groundwater and surface water from both
the 351 and 304 Cells to the Abandoned Biosolids Basin for sedimentation and storage.
CSW and contaminated dewatering water shall then be pumped into the Sanitary Sewer at a
location provided by the City.
D. The Contractor may choose to provide all labor, tools, and equipment, payment of fees, and
coordination for recovery or transfer into a mobile tanker truck or holding tank and off-site
transport, treatment, and disposal by a licensed treatment facility, as required by the specific
nature of the contamination.
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§31 23 19
Dewatering and Wastewater Handling
E. Discharged water shall be metered by the gallon at the point of discharge to the sanitary
sewer. Metering shall be completed using a non-resettable, totalizing flow meter certified
accurate to one gallon. The Contractor shall provide daily flow totals to the Construction
Manager, and shall provide the Construction Manager with independent, certified flow meter
calibration records. The rate of pumping into the Sanitary Sewer shall not exceed 75,000
gallons per day average over any given month. The SWPPP describes the sanitary discharge
permit requirements, rainfall, conceptual water management system layout, and performance
requirements.
F. Discharge of contaminated storm water or dewatering water to the open storm drain system
is not allowed.
3.05
WASTEWATER QUANTITIES AND CHEMICAL PROFILING
A. The Contractor shall be responsible for all wastewater profiling, testing, monitoring,
measurement, and record keeping related to storage and discharge of water and wastewater.
B. The Contractor shall provide complete standby equipment, installed and available for
immediate operation, as may be required to adequately maintain dewatering on a continuous
basis and in the event that all or any part of the system may become inadequate or fail.
C. If dewatering requirements are not satisfied due to inadequacy or failure of the dewatering
system (loosening of the foundation strata, or instability of slopes, or damage to foundations
or structures), the Contractor shall perform Work necessary for reinstatement of foundation
soil and damaged structure or damages to work in place resulting from such inadequacy or
failure by Contractor, at no additional cost to Owner.
D. The Contractor shall immediately repair damages to adjacent facilities caused by dewatering
operations.
E. When dewatering systems are terminated, the Abandoned Biosolids Basin shall be drained,
sediment removed and disposed of in the 351 Landfill, rinsed, and drained again to the
sanitary sewer so the contaminated pond residues are removed and the pond has no
standing water when the Work is complete.
F. Prior to removal, the Contractor shall insure compliance with all conditions of regulating
permits and provide such information to the Construction Manager. Obtain written approval
from the Construction Manager before discontinuing operation of dewatering systems.
END OF SECTION 31 23 19
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Port Angeles Landfill Cell Stabilization Project
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Dewatering and Wastewater Handling