Attachment-C-Dewatering-Specification.pdf

30TH TO K OVERHEAD CONTACT SYSTEMS (OCS) AND STRUCTURES

REPLACEMENT PROJECT

Phase 1A 02 31 09 - 1 Dewatering January 2025

SECTION 02 31 09

DEWATERING

PART 1 GENERAL

1. DESCRIPTION

A. Requirements for furnishing all labor, materials, tools and equipment, and performing all operations necessary by the Contractor for controlling, handling, treating, and disposing of groundwater generated during installation of OCS foundations.

B. Refer to groundwater data provided in SEPTA -Zoo to West, Materials Management Plan dated December 2024. Groundwater analytical results were compared to Pennsylvania Department of Environmental Protection (PADEP) medium specific concentrations (MSCs) for organic regulated substances in groundwater (Nonuse Aquifers, non-residential use), PADEP Water Quality Criteria for Toxic Substances Fish & Aquatic Life, PADEP Water Quality Criteria for Toxic Substances Human Health (TSHH) and Philadelphia Water Department (PWD) Specific Pollutant Limitations Daily Maximum.

C. Chlorinated volatile organic compounds (VOCs) were detected in groundwater at concentrations exceeding PADEP water quality criteria and is therefore considered contaminated. The VOCs identified in groundwater are also regulated under PWD’s Specific Pollutant Limitations. Therefore, dewatering effluent cannot be discharged to the ground surface or the storm sewer system without proper authorization.

D. The Contractor shall determine the appropriate method for groundwater treatment and discharge for this work. Groundwater may be discharged to surface water under a National Pollutant Discharge Elimination System (NPDES) permit or discharged via the City storm sewer system under a Groundwater Discharge Permit issued by PWD. The Contractor shall dispose of treated water according to regulations, potentially by directing it to a permitted discharge point. Alternatively, the Contractor may elect off-site transportation and disposal of the contained groundwater.

E. The Contractor shall submit site-specific dewatering means and methods, permit applications (if applicable) for dewatering, or disposal facility acceptance to SEPTA and Amtrak for review and approval. The Contractor is responsible for obtaining necessary approval(s) and permit(s).

F. Discharge to Surface Water: In the Commonwealth of Pennsylvania, discharging contaminated groundwater from construction dewatering operations to surface water requires a NPDES permit from PADEP and is the responsibility of the Contractor. The permit must be managed through approved Best Management Practices (BMPs), typically under the “PAG-02” general permit for construction stormwater discharges, as groundwater considered contaminated cannot be directly discharged to surface waters without treatment. Groundwater generated during construction shall be treated to PADEP’s water quality standards or as noted in the Permit. As per PADEP

Phase 1A 02 31 09 - 2 Dewatering requirements, if groundwater is contaminated, it shall be treated using appropriate BMPs like filtration systems, sedimentation ponds, or other approved BMPs to remove contaminants before discharge to surface waters. Upon completion of the work, the Contractor shall notify PADEP of completion of work to close out the permit.

G. Discharge via Storm Sewer System: Groundwater may be discharged via the City storm sewer system under a Groundwater Discharge Permit from PWD and is the responsibility of the Contractor. A permit will be issued by PWD outlining the requirements for discharging groundwater. Once a permit is issued, groundwater can be discharged at the specified location and is subject to the permit’s discharge conditions, discharge limits, monitoring, and reporting requirements. Groundwater generated during construction shall be treated to PWD’s Specific Pollutant Limitations or as noted in the Permit. Upon completion of the work, the Contractor shall submit a Groundwater Permit Closure Form to PWD.

H. Off Site Transportation and Disposal: Alternatively, the Contractor may elect to temporarily contain the groundwater in frac tanks or similar equipment during construction, if site conditions allow it and if permissible by SEPTA and Amtrak. The Contractor shall be responsible for waste characterization and receiving waste disposal facility acceptance. The groundwater can then be hauled off-site for disposal at a licensed waste disposal facility.

I. The dewatering treatment systems shall meet the expected dewatering flow rates for dewatering operations required for construction activities of this Contract.

J. Definitions

1. Dewatering: Pumping of water to facilitate installation of OCS foundation below groundwater table.

2. Initial Dewatering: Dewatering to reduce groundwater level to facilitate construction.

3. Maintenance Dewatering: Dewatering to maintain a lowered groundwater level.

4. Monitoring Well: A well primarily used for sampling groundwater quality that may also be used to monitor groundwater levels.

5. Piezometer: A well used for sampling groundwater quality and to monitor groundwater level inside or outside of the excavation area. Locations of piezometers in the area of planned construction are shown on Contract Drawings.

6. Dewatering Well Point or Dewatering Sump: Temporary well points or sumps where dewatering will occur. The locations and design of these temporary well points and sumps and temporary piping to the treatment system are the responsibility of Contractor and are thus not included in the reference design or on the Contract Drawings.

7. Effluent Standards: PWD’s Specific Pollutant Limitations if discharge via storm sewer system.

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2. REFERENCED SECTIONS

A. Section 01 06 00 – REGULATORY REQUIREMENTS &SAFETY

B. Section 01 50 00 – TEMPORARY FACILITIES AND CONTROLS

C. Section 02 19 06 – TESTING REMOVAL AND DISPOSAL OF SOLIDS

D. Section 02 27 00 – EROSION AND SEDIMENT CONTROL

3. CITED STANDARDS

A. ASTM International (ASTM)

4. D4607 – Determination of Iodine Number of Activated Carbon

B. American Water Works Association (AWWA)

1. B100 – Filtering Material

2. B400 – Coagulation

3. B604 – Granular Activated Carbon Standards

4. C704 – Flow Meters

4. NOTED RESTRICTIONS

A. Dewatering effluent cannot be discharged to the ground surface or the storm sewer system without proper authorization.

B. The Contractor is responsible for identifying means and methods to contain, manage, and handle groundwater generated during this work. The Contractor may select on site groundwater treatment or off-site transportation and disposal at a licensed waste disposal facility. The Contractor shall identify final discharge method, obtain necessary approvals and permits, and obtain SEPTA and Amtrak approval prior to performing dewatering. choose to discharge treated groundwater on site and comply with discharge limits on the applicable permit or contain and transport contaminated groundwater for off site disposal.

C. If off-site disposal is selected by the Contractor, groundwater shall be collected using appropriately sized containers, tanker trucks, frac tanks, or other containment vessels.

If this dewatering management approach is not feasible, the groundwater should be contained, treated and discharged on-site either to surface water under a NPDES permit or via the storm sewer system under a Groundwater Discharge Permit.

D. The dewatering treatment system shall be installed and functional before commencement of any dewatering.

5. QUALITY CONTROL

A. Regulatory Requirements:

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1. PADEP

2. NPDES

3. PWD

4. United States Environmental Protection Agency (USEPA)

Resource Conservation and Recovery Act (RCRA)

40 CFR Part 261 – Identification and Listing of Hazardous Waste

29 CFR 1910.120 – Occupational Safety and Health Administration

(OSHA)

B. Dewatering treatment system shall meet discharge permit requirements for water flow rate and water quality.

C. Verify compliance with referenced standards and regulations.

D. Obtain approval from all regulatory agencies having jurisdiction before construction.

6. SUBMITTALS

A. Submit all items listed herein no later than 30 days following Contract Notice to Proceed.

B. Submit dewatering treatment system schematic diagram and design calculations for all system components, processes, and removals, including the collection systems used from each of the dewatering locations leading to the dewatering treatment system.

C. Submit dewatering treatment system Shop Drawings and catalog cut sheets including all suppliers for any filtration media (e.g., activated carbon, ion-exchange resins, and bag filters). Carbon shall conform to AWWA B604 using test method ASTM D4607.

D. Submit permit applications for review and approval prior to submission to regulatory agencies.

E. Submit analytical results of dewatering treatment effluent in comparison to PWD’s Specific Pollutant Limitations or as specified by regulatory agency.

F. Submit emergency power supply and switching plan in the event of a power outage.

G. Submit Operation and Maintenance (O&M) Plan to include provisions for removal and disposal of settled solids (cake) from filter press, replacement of bag filters (e.g., pressure differential greater than 15-pounds per square inch [PSI]), carbon servicing (at breakthrough from first unit or pressure differential greater than 15 PSI), etc. Plan shall maximize system performance, minimize friction losses, and assure effluent concentrations below Discharge Limits. The plan shall also include contingencies for changes in influent concentrations or pH, changes in influent flow rate, system component malfunction, overflow alarm sequences, and other foreseeable potential occurrences. The O&M Plan shall include spill prevention, containment, and countermeasure plans for fueling of construction equipment.

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H. Submit Safe Work Plan (SWP) pursuant to OSHA 29 CFR 1910.120 and SEPTA’s requirements specific to the operation and maintenance of the dewatering treatment system, including provisions for: handling and cleaning bag filters; handling potentially hazardous materials (e.g., spent carbon, ion-exchange resin, filter press cake, bag filters, etc.); and confined space entry (cleaning of sedimentation tanks). The plan shall include provisions for spill containment and control measures. The plan shall also describe air monitoring methods and frequency for within the dewatering treatment system building and excavation.

I. Submit Dewatering Treatment System Monitoring Plan to include methods for sample collection and analysis from the end-point of individual dewatering treatment system components (e.g., at the effluent of each individual chemical removal component) to assess treatment component removal efficiency as referenced herein.

J. Submit qualifications of designer of the dewatering treatment system. Designer shall have a minimum of five years of experience with designing dewatering treatment system.

K. Submit qualifications and applicable up-to-date licenses and safety certificates for all dewatering treatment system operators, waste handling contractors, and waste receiving facilities.

L. Submit copies of all state and city permits required to conduct dewatering, dewatering treatment, and discharge to City storm sewer, if applicable.

M. Provide local permits, as required, for storage of reagents for pH adjustment systems and provide copies to the Construction Manager.

7. DELIVERABLES

A. Provide hazardous waste manifests for removal and disposal of any filtration media and any other potentially hazardous materials. Such wastes shall include recovered waste oil, settled solids, and used absorbent materials.

B. Provide bills of lading for disposal of settled solids (filter press cake).

C. Provide O&M manuals for all system components.

D. Submit Dewatering Treatment System As-Built Drawings.

E. Submit Periodic Monitoring Reports.

F. Submit Dewatering Treatment System Log Book.

PART 2 PRODUCTS

1. GENERAL

A. The dewatering treatment systems shall consist of a primary clarifier (e.g., gravity sedimentation tanks), coagulation and flocculation components, multi-media filtration (i.e., carbon absorption, ion-exchange resins, and bag filters) or other industry

Phase 1A 02 31 09 - 6 Dewatering accepted dewatering treatment system components necessary to meet applicable Effluent Standards. The following products are part of a suggested dewatering treatment system, which has been designed based on the anticipated dewatering flow rates and groundwater conditions. Contractor shall take into account existing groundwater contamination at the Site, as well as groundwater contamination that may be incurred during construction activities. Contractor must provide, operate, and maintain a dewatering treatment system that provides sufficient treatment and flow rate to meet the required discharge limits within all applicable federal, state, and local regulations and standards, including air discharge limitations. The system is part of a construction dewatering project; as such, the system must be 100-percent functional at all times. Delays due to component repair or replacement are not permitted. The system shall be fully redundant to allow for replacement of components during continual operation.

B. Provide reinforced concrete slab to support dewatering treatment system equipment (if required).

C. Covered and Insulated Treatment Building: For dewatering treatment systems, a building (dewatering treatment system enclosure) shall be constructed to facilitate filtration media replacement, removal of filter press cake, removal of potential oil, and replacement of system components in the event of component failure.

D. Power and Back-Up Emergency Power Plan: Provide power and back-up emergency power that will switch over automatically upon loss of primary power.

E. Heating and ventilation system, lighting, water supply, security, communications, and all other necessary amenities to treatment building: Provide water, electricity, and ventilation as required for system operation and servicing.

F. Piping, fittings, and all other accessories and appurtenances from the Work Site to the dewatering treatment system, from the dewatering treatment system to the discharge location, and to transfer excess storm water from primary clarifiers to storm drainage system, as required. All external piping shall be heat traced and insulated to protect from freezing.

G. Control panels, as needed, for the dewatering treatment system and all associated pumps.

H. All valves, sampling ports, meters, gauges, and controls to maintain adequate flow rates and treatment efficiency and allow for isolation and replacement of malfunctioning equipment. Flow meters shall conform to AWWA C704. All meters, sampling ports, and gauges shall be located at sufficient distance from piping bends, tees, and valves as recommended by the manufacturer for accurate measurements.

I. All equipment shall be designed for its intended use in a potentially wet and hazardous environment and for potential contact with hazardous substances. Consider need for intrinsically safe or explosion proof heating, ventilation and lighting components as the interior of the building may be a potentially hazardous environment due to the presence of activated and spent carbon and potential contaminant vapors, some of which may be flammable. Make every effort to control these conditions, such as sealing and venting the primary clarifiers to the outside (or locating the tanks outside the building).

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J. All equipment shall be redundant; a second flow path shall be immediately operational at all times with identical equipment to assure continued operation during equipment maintenance or malfunction. Similarly, replacement parts such as bag filters, meters, gauges, and connections shall be stocked in adequate supply in the treatment system building for emergency purposes.

2. DEWATERING TREATMENT SYSTEM COMPONENTS

A. Primary clarifiers are suggested with a capacity sufficient to serve as a 5-hour retention tank. Connections to the tanks are specified herein below. A duplicate (standby) tank shall be added to the system design for use during removal of sediment from the active tanks, to contain excess dewatering or storm water, or in the event of fouling of the tank (e.g. oil spill).

B. Transfer pumps to transfer liquids from primary clarifiers to the remaining components of the dewatering treatment system and to discharge to city storm sewer system are suggested. The low level switch in each of the components upstream of the pumps shall be set such that pump priming is not required and net positive suction head (NPSH) requirements for the pumps are met.

C. Rapid mixing tanks are suggested for the addition and incorporation of a coagulation additive to help facilitate the formation of larger colloidal particles to aid with settling.

Chosen coagulant shall conform to AWWA B400. A minimum detention time of 40 seconds, a minimum velocity gradient of 790 feet per second (fps) per foot to obtain a turbulent flow regime, and a minimum tank depth of 1.25 times its diameter is suggested for design of the rapid mixing tanks.

D. Tapered flocculation basins with three compartments are suggested to further the settling of suspended particles in the influent. A residence time of at least 45 minutes is also suggested. The depth of a flocculation basin should be equal to its width. Due to the potential variability of the influent flow rate, baffle mixing is not recommended.

E. Ion-exchange resin filters are suggested to remove excess metals potentially in the influent. Ion-exchange resins shall conform to AWWA B100. Frequency of resin replacement shall also be considered in choosing the size of the units.

F. Filter presses are suggested to facilitate the consolidation and removal of settled solids from the sedimentation tanks. Filtrate should be piped back to the start of the dewatering treatment system for incorporation into treatment influent. Filter press cake shall be disposed of in accordance with federal, state, and local regulations.

PART 3 EXECUTION

1. PREPARATION

A. Submit to the permitting authority(ies) the information required as identified in each permit. Dewatering and discharging activities may only commence upon the approval by the permitting authority(ies) under the permit requirements and any additional Project-specific conditions.

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B. Contractor’s design shall consider initial dewatering, maintenance dewatering, and flows associated with excavations. The design shall consider overall system flow rate and individual component capacities. Initial dewatering shall be piped directly to primary clarifiers. Open settling ponds shall not be used to avoid to potential volatilization of contaminants. In addition, localized dewatering well points are suggested to minimize the migration of contaminants through the subsurface (both horizontally and vertically) and to minimize the potential volatilization of contaminants.

The locations and design of these temporary well points and temporary piping to the treatment system are the responsibility of Contractor and are thus not included in the reference design or on the Contract Drawings.

C. Verify installation of treatment system components complies with manufacturer’s instructions, standards, and recommendations.

D. Design, install, operate, and maintain a dewatering treatment system to reduce identified contaminant concentrations to required levels stipulated in applicable discharge permit(s) from the PADEP, and/or PWD. The dewatering treatment system must be installed and functional before commencement of any dewatering.

2. DESIGN

A. The products specified herein above have been designed based on Contract-specific data and are intended to provide Contractor with an industry accepted treatment scheme to address Work Site-specific contaminated water dewatering. This information does not relieve Contractor of its Contractual obligations for dewatering treatment system design. Contractor is required to prepare schematic diagrams and design calculations to demonstrate adequacy of the proposed dewatering treatment system.

B. Design the dewatering treatment system to meet discharge criteria as stipulated in the applicable PADEP, and/or PWD (and/or effluent standards) permits and supplemental requirements as may be stipulated in these permit(s).

C. Design the dewatering treatment system to operate continuously, without interruption and provide adequate removal efficiency to meet the permit and/or effluent requirements. The system must not, in any way, cause any delay in dewatering and must at all times be capable of handling all dewatering generated during initial and maintenance dewatering for the Project; as such, the system shall be designed for redundancy to provide backup for key system components that may require periodic isolation for maintenance and/or repair. The system design shall also consider the effects of potential variability in flow rate and contaminant and metals concentrations in influent, especially during the initial dewatering phase. The use of duplicate or multiple smaller treatment units (mini-systems of similar components as specified herein) running in parallel may be considered on the basis of meeting the required initial temporary flow rates and in avoiding overall system failure.

D. The design shall also consider the presence of various metals, including iron, manganese, sodium, calcium, and chromium in the influent. The presence of these metals in water passing through the dewatering treatment system may cause precipitates and scaling requiring dewatering treatment system maintenance. The installation or use of metals filtering or sequestering systems shall be conducted in

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E. At a minimum, the design shall incorporate meters, gauges, and sampling ports for the measurement of flow rate, total flow, operating pressures, and influent and effluent concentrations.

F. Controls (i.e., high level switches in each tank, etc.) and alarms shall be furnished and operated to prevent overflow, spills, or other discharge other than in accordance with permit requirements.

G. Design shall also incorporate bypass of dewatering treatment system finishing components (i.e. carbon absorbers, etc.) for direct discharge in the event system monitoring indicates the finishing components are not required for the effluent to meet discharge limits.

3. INSTALLATION

A. The dewatering treatment system and associated components shall be located, operated, and maintained such that all utilities within the area shall be protected from damage.

B. Protect all benchmarks, survey control points, boring locations, monitoring wells, and piezometers from damage or displacement during dewatering storage and groundwater treatment activities at the project site.

C. Protect any on-site drainage basins, outfalls, and connections thereto from damage, accumulation of silts, sediments, or other solids from groundwater conveyed within or discharged from the project.

D. Signs shall be posted inside and outside the treatment system building or enclosure with emergency contact information in the event of system failure or malfunction. Signs shall also be posted regarding potential hazard information.

E. Erosion and sedimentation controls shall be installed and maintained around deep sump pits to limit sediment infiltration of the sumps. Similar controls are required during the initial dewatering phase around all temporary sumps.

F. The design shall incorporate adequate ventilation systems in the dewatering treatment system building for potentially hazardous environments. The design shall consider potential volatilization of contaminants from the waste stream during system servicing, repair, and leakage/spillage. Primary clarifiers shall be vented to the atmosphere.

G. The design shall include provisions for washdown of dewatering treatment system building interior and equipment within as well as removal and proper disposal of any cleaning materials and any spilled materials or water.

H. Contractor is responsible for ensuring that any materials used inside the building do not adversely affect the operation of the system.

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I. Inlet and outlet piping to the sedimentation tank shall be installed to contain any oil within the tank and maximize the flow pathway (i.e. residence time) within the tank for settling of solids. The inlet pipe shall connect at the tank influent which shall be near the top of the tank. The tank outlet shall be placed on the opposite end of the tank below the low water level (set pump control switch approximately one foot above top of tank outlet). The outlet pipe shall also be fitted with a strainer and placed above the bottom of the tank to allow for settled solids containment. Flow rate through the tanks shall provide for a residence time of at least 4.7 hours or the time required for settlement of solids which results in clear effluent water from the tank.

J. Storm water overflow piping from the primary clarifiers shall be installed. The overflow piping shall be connected at the very top of the outlet end of the sedimentation tanks.

Activate high-high switch to turn off dewatering pumps and activate alarm sequence when water level reaches a minimum of one foot below top of primary clarifiers.

K. All system components, piping, and connections shall be water and vapor tight.

Potential venting of the primary clarifiers shall be controlled and vented to the atmosphere solely for pressure stabilization within the tank due to water level fluctuation.

4. START-UP AND TESTING

A. Start the dewatering treatment system in accordance with manufacturer’s operating procedures, design considerations, and applicable permit requirements. The dewatering treatment system manufacturer’s representative(s) shall be present for system start-up and provide requisite training for Contractor’s operating personnel.

B. Conduct initial dewatering treatment system testing to verify compliance with effluent standards and in accordance with PADEP and/or PWD application requirements.

Analysis of the dewatering treatment effluent must be provided before full system activation.

C. The air within the dewatering treatment system building, and excavation as needed, shall be monitored for oxygen levels and potential contaminant concentrations to assure adequate ventilation system operation.

5. OPERATION

A. Operate the dewatering treatment system in accordance with manufacturer’s operating procedures, design considerations, and applicable permit requirements.

B. Keep a Dewatering Treatment System Log Book to record all measurements of system performance such as operating pressures, temperatures, influent, mid-fluent, and effluent concentrations, flow rates, and volumes.

C. Provide the requisite personnel with appropriate training and certification to operate the dewatering treatment system as required in the discharge permit(s).

D. In the event concentrations at the influent of the finishing component (e.g., activated carbon filters, ion-exchange) concentrations meet the discharge limits; bypass of these system components shall be conducted subject to review by the Construction Manager.

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Demonstrate compliance with discharge limits to the satisfaction of the regulatory authorities having jurisdiction. Obtain in writing approval from the governing authority to alter the dewatering treatment system.

E. Maintain the dewatering treatment system and its various components in accordance with the manufacturers’ recommended maintenance routines and procedures.

F. Inspect system components daily for the presence of oil, ice, settled solids accumulation, flow rates, pressures, and effluent color and appearance. Clean and replace system components and re-inspect as needed.

G. Settled solids shall be handled in accordance with Sections 02196 and any local, State or Federal (RCRA, 40 CFR Part 261) regulations that may apply. Removal of settled solids is also recommended prior to any foreseeable significant storm events. Similarly, the erosion controls around the deep sump pits shall be maintained to limit sediment infiltration of the sumps and any sediment in the sumps shall be removed as needed.

H. Remove oil from the sedimentation tank as needed. An oil absorbent boom shall be maintained and replaced, as necessary in the influent side of the sedimentation tank.

Any accumulated oil shall be removed either by absorbent media (pads or booms) and placed in 55-gallon DOT drums or by vacuum truck. Oil shall be handled according to all Contract Specifications and applicable federal, state, and local regulations for waste oil disposal.

I. Clean and replace bag filters as needed and at a minimum pressure differential of 15

PSI.

J. Replace filtration media (e.g., activated carbon and ion-exchange resin) upon breakthrough at mid-fluent. The upstream (spent) filtration media shall be removed for off-Site recycling; the down-stream filtration media shall be transferred to the upstream unit; and new filtration media shall be installed in the down-stream unit.

K. Back-flush the filtration units in the event of bed fouling indicated by a pressure differential of 15 PSI.

L. Additional treatment components shall be installed and operated as necessary to maintain the flow rates necessary for dewatering and to assure compliance with the Discharge Limits. Such components may include, but are not limited to: additional sedimentation tanks, metals removal or sequestering systems, additional carbon units, pH adjustment systems, flocculation basins with rapid mixing, filter presses, or complete additional treatment lines for increased flows.

M. Provide adequate ventilation of dewatering treatment system building/enclosure, especially during system maintenance. Repair any liquid or vapor leaks in equipment and piping. Keep all openings to off-line components closed. The interior air of the building, and within the excavation, shall be monitored for oxygen levels and contaminant concentrations to assure adequate ventilation during system operation.

Monitoring shall occur every day for the first week of operation. Monitoring frequency may be reduced to sampling events and system servicing thereafter following approval by the Engineer.

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END OF SECTION