1993 Specifications CSJ SPECIAL SPECIFICATION ITEM 4417 DEWATERING IN CONTAMINATED GROUNDWATER

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1 1993 Specifications CSJ SPECIAL SPECIFICATION TO ITEM 4417 DEWATERING IN CONTAMINATED GROUNDWATER 1. DESCRIPTION. This item shall govern all work required to remove groundwater encountered during construction in or near areas of contaminated groundwater as described in the General Notes. The Contractor shall be responsible for dewatering operations and for disposal of the water removed. This item shall provide for furnishing all labor, materials, equipment, power and incidentals and for performing all operations necessary to dewater, drain, maintain excavations and foundations in or near areas of contaminated groundwater as described in the General Notes and as described herein; and as necessary for installation of storm sewer and appurtenances. Included are construction and maintenance of cofferdams; installing, maintaining, operating, and removing well point systems and other approved devices or methods for lowering the water table within an excavation. This item shall govern all provisions for treatment and proper disposal of contaminated groundwater generated by construction dewatering in or near areas of contaminated groundwater as described in the General Notes and as described herein; and as necessary for contaminated groundwater collection, containment, monitoring, sampling, treatment and disposal. Included are installation, maintenance, operation, and removal of contaminated groundwater treatment equipment and appurtenances; and other approved devices, equipment or methods for monitoring, permitting, treating contaminated groundwater generated by construction dewatering. Effective dewatering will be critical to provide safe trench conditions and to the support of manholes, inlets, pipe, and junction boxes. Placement of pipe in areas where the water table is not at or below the two (2) feet limit will be grounds for rejecting the pipe installation. The Contractor shall limit the disturbance of contaminated groundwater in the areas described in the General Notes, or as directed by the Engineer. The Contractor may conduct his own investigations, as he deems necessary, to ascertain the depths to groundwater and groundwater quality at the time of construction prior to submission of the dewatering plan.

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3 The Contractor may be asked at any time during the project to locate the water table at any arbitrary location in an open trench along the construction route by excavating to a depth not to exceed two (2) feet below the invert of the pipe to determine if he is complying with the two (2) foot requirement. If the water table is found to exist within the two (2) foot depth below the pipe invert no more pipe shall be placed until the water table is lowered to the two (2) foot limit. 2. CONSTRUCTION METHODS. A. General. All work shall be performed under this item shall be in compliance with all laws and regulations of the Federal, State and local governments in whose jurisdiction the service~s is performed and the following publications (or latest revision) as a minimum. Texas Administrative Code (TAC) Texas Natural Resource Conservation Commission Chapter 30 TAC Chapter 335 "Industrial Solid Waste" 30 TAC Chapter 308 "Criteria for NPDES" Code of Federal Regulations (CFR) United States Department of Labor 29 CFR 1910 "Occupational Safety and Health Standards" 29 CFR 1926 "Safety and Health Regulations for Construction" United States Environmental Protection Agency 40 CFR 261 "Identification and Listing of Hazardous waste" B. Safety Precautions. The Contractor shall be responsible for directing the use of personal protective clothing and equipment to minimize employee exposure to harmful vapors that may be associated with contaminated groundwater or other regulated materials encountered during construction dewatering. Construction worker exposure shall be monitored for compliance with OSHA standards. The Contractor shall be responsible for implementing a site air monitoring plan that shall be described in the Contractor~s health and safety plan, and developed in accordance with OSHA standards. The Contractor shall at all times maintain safe and continuous access to the work site for the State's designated representative, Federal, State, and local authorities. The Contractor shall provide all necessary safety measures including, but not limited, to fencing, barricades, warning signs, flags, and steel plates over trenches, to ensure the safety of the Contractor, subcontractors, and all vehicular and pedestrian traffic in the project area. Required barricades and warning signs shall be placed around the work zone prior to initiation of work and kept in place until all work has been completed. The Contractor shall eliminate all potential sources of ignition from the work area including smoking materials, and explosion-proof electrical and internal combustion equipment.

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5 C. Regulated Substances. The Contractor shall be responsible for proper handling, transportation, treatment, and disposal of any regulated substances, including contaminated groundwater removed from or associated with any excavation or drill shaft work conducted in or near suspected areas of contaminated groundwater, as indicated in the General Notes. The work shall be conducted in a safe and environmentally sound manner. The work shall be conducted in accordance with all applicable regulations. The Contractor shall employ and pay for the services of an independent Environmental Testing Contractor to perform contaminated groundwater sampling and related activities, including inspection and monitoring of the dewatering systems and any on-site contaminated groundwater treatment system, as required to ensure that these activities are performed by personnel qualified to provide professional environmental services, and are registered as a corrective action specialist with the Texas Natural Resource Conservation Commission (TNRCC) and have Corrective Action Project Manager on staff, if applicable. D. Control of Groundwater. The Contractor shall limit the disturbance of contaminated groundwater in the areas described in the General Notes, or as directed by the Engineer. The Contractor shall have full discretion to select the method of dewatering and groundwater control, including counter-pumping wells, thin wall slurry cutoff, jet grouting, sheet pile walls, and slurry walls, or any combination, or other means of limiting the generation of water and drawdown, subject to the review and approval of the Engineer. E. Dewatering Plan. The Contractor shall submit to the Engineer a dewatering plan indicating the proposed locations of dewatering wells, well points, pumping facilities, dewatering conveyance system, routing, discharge pipes, and discharge points. The dewatering plan shall include dewatering methods that will limit the extent of the water table drawdown beyond the construction, including counter-pumping wells, thin wall slurry cutoff, jet grouting, sheet pile walls, and slurry walls, or any combination, or other means of limiting the generation of water and drawdown, subject to the review and approval of the Engineer. The plan shall include provisions for the installation and monitoring of sufficient piezometers to show that all trench excavation is predrained prior to excavation. F. Water-Level Monitoring. The Contractor shall control pumping rates to prevent excessive drawdown of the water table during construction dewatering. The Contractor shall monitor the extent of the water table drawdown caused by dewatering as the construction approaches contaminated groundwater. The Contractor shall ensure dewatering efficiency by controlling groundwater pumping rates based on water level measurements made using continual monitoring instrumentation, including water level transducers and data loggers during predrainage and construction dewatering.

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7 G. Contaminated Groundwater Treatment. Groundwater generated by construction dewatering in or near areas of contaminated groundwater may require treatment, using mobile, on-site contaminated-groundwater treatment systems, prior to surface discharge, as described in the General Notes. The Contractor shall employ services as necessary to rent, deliver, mobilize, install, and operate equipment and facilities as necessary for the temporary treatment of contaminated groundwater that may be generated by construction dewatering. The temporary, on-site groundwater treatment system will be capable of adequate contaminant removal to comply with the discharge permit requirements. H. Contaminated Groundwater Discharge Permit. The Engineer shall be responsible for obtaining all applicable permits for direct surface discharge of treated groundwater. The Contractor shall comply with all applicable permitting and discharge requirements associated with the dewatering system operation, including registration of air or vapor emissions resulting from groundwater treatment, if necessary. I. Dewatering Plan. The Contractor shall submit to the Engineer a dewatering plan indicating proposed groundwater treatment methods; locations of dewatering wells, piping, treatment equipment; groundwater and treated discharge sampling, and discharge points; and applicable discharge permit and regulatory requirements. Upon completion, dewatering well casings shall be removed from the well and the entire well filled with cement from the bottom up to the land surface, or the well may be filled with bentonite mud followed by a cement plug extending from land surface to a depth of at least 10 feet. The Contractor may conduct his own investigations, as he deems necessary, to ascertain the depths to groundwater and groundwater quality at the time of construction prior to submission of the dewatering plan. J. Off-site Disposal of Contaminated Groundwater. The Contractor shall notify the Engineer of any contaminated groundwater seepage into an excavation or open trench. The Contractor may propose to collect, contain, and transport contaminated groundwater to an offsite, permitted treatment and disposal facility. The Contractor shall ensure that contaminated groundwater is properly collected and contained. Contractor shall ensure proper waste classification of contaminated water, and disposal of contaminated water in compliance with the waste acceptance procedures of the waste disposal facility and the TNRCC.

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9 The Contractor shall seek to obtain a one-time waste profile that may be applied to contaminated water generated during the construction project that is not otherwise treated and discharged on-site. Contaminated water generated at an excavation work area or during equipment decontamination shall be collected by vacuum truck and transported offsite for disposal under a one-time waste profile, or pumped into single walled 55-gallon drums and transported to an interim storage area pending waste classification, or treated and discharged on-site. K. Certification. The Contractor shall submit to the Engineer written certification of the following: Certification that on-site contaminated groundwater treatment was performed in compliance with applicable state and local regulations. Certification from the waste transporter, if applicable, that the waste liquids were transported to the selected treatment and/or disposal facility in compliance with all safety rules and applicable industrial waste regulations and that the transported is properly permitted in compliance with Federal, State and local waste transportation requirements. Certification from the waste disposal facility, if applicable, that the waste liquids were disposed, including off-site treatment if applicable, in a permitted industrial waste disposal facility in compliance with applicable regulations. The Contractor shall provide the Engineer with copies of completed waste disposal manifest forms for each waste shipment. 3. Measurement. "Wellpoint Dewatering" will be measured by the linear foot of open trench excavation requiring dewatering in or near areas of contaminated groundwater. For bidding purposes, the Contractors well point dewatering system shall include, at a minimum, two (2) lines of wellpoints, spaced at 10 feet apart and set at a depth of 20 feet below grade, pumping at 20 gpm each, to achieve the required drawdown (a maximum of 10 feet below grade). It is assumed that the dewatered section for open trenching will be 100 feet with an average total flow of 480 gpm for the well point system. The well point lines would run parallel to the trench, with one line located on each side of the trench. Each well point shall be installed with a filter pack. The Contractor may install wellpoints and/or pumps in bench-type excavations where space is available in working areas to increase wellpoint efficiency. The Contractor shall conduct its own dewatering system evaluation and design. The minimum wellpoint arrangement is effective for dewatering an open trench excavation. Clay layers complicate drawdown predictions. It is likely that the medium dense clay layer thickness will vary through the project, and in some places the wellpoints may encounter higher hydraulic conductivity. The Contractor shall be prepared to increase pumping rates or wellpoints as needed to achieve adequate drawdown.

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11 For bidding purposes, at a minimum, two (2) existing groundwater monitoring wells (MW-7 at Station and MW-5 at Station 41+00) shall be used by the Contractor to monitor depression of the water table in the contaminated groundwater plumes caused by construction dewatering in this section of the project. The Contractor shall design the dewatering system such that the maximum allowable decrease in the water table in a contaminated groundwater plume caused by construction dewatering will be 0.5 feet. "Groundwater Treatment System" will be measured by the linear foot of open trench excavation requiring dewatering of contaminated groundwater which is treated prior to discharge. For bidding purposes, at a minimum, the Contractor shall include in the dewatering system provisions for diverting contaminated groundwater to a mobile groundwater treatment system as specified herein. The treatment system shall be capable of removing dissolved petroleum and chlorinated hydrocarbons from contaminated groundwater at the flow rate required to maintain adequate dewatering. The Contractor shall monitor groundwater for the presence of contaminants in or near known areas of contaminated groundwater. The Contractor shall have mobile treatment units on standby at the site when dewatering in or near areas of contaminated groundwater. The dewatering system shall be configured so that contaminated groundwater may be diverted to the treatment units as needed. The Contractor will not be permitted to discharge any groundwater into existing sanitary sewer lines. For bidding purposes, the Contractor shall collect one (1) sample of treated groundwater on each day that dewatering is conducted in this section for analysis of TPH (EPA Method 418.1), BTEX (EPA Method 8020), Volatile Organic Compounds (EPA Method 8260) analysis, and total dissolved solids (TDS). Analysis for conductivity, total lead and ph will be performed on a weekly basis. The actual sampling and analysis requirements will comply with the discharge permit. 4. Payment. The work performed and materials furnished in accordance with this Item and measured as provided under "Measurement" will be paid for at the unit prices bid for "Wellpoint Dewatering~ and ~Groundwater Treatment System" Unit prices in the Bid include all costs to fully complete the work in accordance with this Item, including provisions all labor, materials, tools, equipment, services, supplies, incidentals, and all necessary operations. No costs in connection with the work required under this Item for proper and successful completion of the Contract will be paid outside of or in addition to prices submitted in the Bid.

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13 The quantities listed in the proposal bid schedule will be considered as approximate and will be used for the comparison of bids. Payment will be made to the Contractor only for the actual quantities of work performed or materials furnished in accordance with this Item. The quantity of work to be done may be increased or decreased as conditions allow and with the approval of the Engineer. This price shall be full compensation for dewatering operations and disposal of water removed; for worker safety; for OSHA and environmental regulatory compliance; for monitoring water table drawdown and water quality; for operation and dismantling of water treatment and dewatering systems, including pumps, conveyance piping, and related equipment; and for all labor tools and equipment and incidentals to complete the work. The Contractor shall be responsible for the stability of all temporary and permanent slopes, grades, foundations, materials and structures during the course of the Contract. Repair and replace all slopes, grades, foundations, materials and structures damaged by water, both surface and sub-surface, to the lines, grades and conditions existing prior to the damage at no additional cost.

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