Section 02999 TEMPORARY HANDLING OF SEWAGE FLOWS

Section 02999

TEMPORARY HANDLING OF SEWAGE FLOWS

PART 1 - GENERAL

1.1 WORK DESCRIPTION

A. The CONTRACTOR is responsible for the temporary handling of sewage throughout the construction of the Project. This includes the construction, modifications, and the relocations of OCSD sewers and facilities.

B. The CONTRACTOR shall comply with the Regional Water Quality Control Board, Health Department, and OCSD standards, Air Quality Management District permits, and regulations. The CONTRACTOR shall cooperate with OCSD staff and other regulators and environmental agencies.

C. This section covers all bypass conditions for the Project however; it is detailing only the main bypass conditions that might last for a significant period of time. The other bypass conditions shall follow the same rules and shall be subject to the same penalties.

1.2 CONTRACTOR LIABILITY

A. The CONTRACTOR shall be responsible for continuity of sanitary sewer service to each facility connected to the trunks sewers during the execution of the work to be performed under this Contract. In the event that sewage backup occurs and enters dwellings or other structures due to in any part to a failure of the bypass piping system or to non-compliance with the Contract Documents, the CONTRACTOR shall be responsible for cleanup, repair, property damage costs, fines imposed by jurisdictional authorities, and all claims arising there from. All spills shall be contained and returned to the sewer system.

B. In the event the Regional Water Quality Control Board levies a fine on OCSD because of a sewage spill caused by the CONTRACTOR (directly or indirectly) due to its lack of attention to procedures or other negligence, the CONTRACTOR shall be held responsible and liable for reimbursing OCSD for the entire amount of any fine imposed. OCSD may assess the amount of the fine against payments due the CONTRACTOR. The California Water Code gives the Regional Water Quality Control Board authority to fine up to $10 per gallon and $10,000 per day for an illicit discharge.

1.3 CONTRACTOR SUBMITTALS

A. Unless otherwise indicated, the following shall be submitted, for each bypass installation, to the ENGINEER 15 days after the effective date of the Notice to Proceed, in compliance with the General Requirements, and as specified herein.

B. Plans showing any proposed changes from the Contract Documents for the temporary handling of sewage flow, routing and protection of bypass lines, containment areas, equipment location, schematic of pump set-up and discharge, and proposed sequencing.

C. Shop drawings for sewer bypass pipe material and fittings, pipe repair kits and procedures, spill recovery mats and video camera inspections.

D. Bypass pump characteristic curves, electrical, controls, and instrumentation.

E. Proposed alternatives to the spill prevention, control, and countermeasure plan as described in Part 3 of this Specification.

F. Proposed odor control and monitoring plan, implementation scheme and monitoring reports.

1.4 PAYMENT

A. Unless otherwise provided in these Specifications, full compensation for temporary handling of sewage, implementation of the spill prevention, control and countermeasure plan, and the odor assessment and odor control plan shall be included in the Contract Unit Price for which such work is appurtenant thereto, and no additional allowance shall be made therefore. Said various Contract Unit Prices shall include all labor, materials, tools, and equipment necessary or incidental to the temporary sewer service operations.

PART 2 - PRODUCTS

2.1 PUMPING EQUIPMENT

A. The indentified bypass pumping for the Project is required for the Dissolved Air Floatation Thickeners Underflow (DAFTU) new valve vault and pipeline and for the modifications required on the INTR 66 inch pipe to run through the new tunnel 32.

B. For the Dissolved Air Floatation Thickeners Underflow (DAFTU) by pass condition; the pumps shall be non-clog submersible sewage pumps sized and designed for the following conditions:

1. DAFTU bypasses from existing manhole upstream of the new DAFTU valve vault to the existing 20-inch CI (D) pipe downstream of the new DAFTU valve vault.

2. DAFTU flow range is 0.5 mgd – 2.0 mgd.

3. No restrictions on the length of time they can bypass, however this should be confirmed with OCSD.

4. In the event the CONTRACTOR elects to use engines to drive pumps, the engines shall be muffled in such a manner that the maximum noise level will not exceed 60 dBA at a distance of five feet from the engine. Lower noise levels may be specified in the permit by governing agencies. Regardless of the noise level, soundproofing shields not less than eight feet high shall be provided around each engine by the CONTRACTOR to absorb noise.

5. Standby pumping equipment shall be at the site continuously during pumping to provide 100 percent standby pumping capacity. The CONTRACTOR shall provide manpower to continuously monitor the pumping equipment on a 24-hour basis while in operation and to activate standby equipment, if necessary.

6. Provide level control equipment with the pump system to start and stop pumping based on liquid level in the manhole complete with alarms for high and low levels. Monitoring equipment shall enable automatic switchover of pumps in pump failure conditions and communicate alarms to plant operation via telemetry measures for unmanned durations.

C. For the INTR 66-inch pipe modifications at tunnel 32 area a bypass condition shall be accomplished by closing gates in the existing primary effluent diversion box (PEDB) which will divert the flow to the existing 84-inch pipeline. However, the gates in the PEDB are 20 years old and may leak. The CONTRACTOR shall provide a pumping system to pump the leaked flow through the gate to the other chamber in the box. Consider the following assumptions for this activity which can be adjusted in the field to suite the conditions after obtaining the ENGINEERs acceptance:

1. Use non-clog submersible sewage pumps sized and designed for the conditions.

2. Flow rate can be 0.1 to 1 MGD and can vary throughout the day.

3. The PEDB floor might require some slopes to accommodate the pump installation.

4. Provide controls to start and stop the pump based on water levels and provide failure alarms.

5. Provide telemetry measures to communicate the alarms to operation if the facility would not be manned 24/7.

2.2 BYPASS PIPING

A. The pipe material for the highline shall be HDPE with welded joints or PVC or DI with restrained joints. The pipe size will be determined based on pump size to provide velocity range of 3 to 6 feet per second at all times and operating conditions. The CONTRACTOR shall provide design calculations in the shop drawings to justify the pump sizing and selection.

2.3 TEMPORARY PLUGGING OF SEWER

A. Plugs shall be appropriate for the application. Unless otherwise indicated, plugs shall be a heavy-duty inflatable type with a steel rod through plug centerline, a retaining plate and an eye-lift on both ends. Plugs shall be new, made of natural rubber and shall show no cracks or signs of damage. The plugs shall have a flexible sealing design to compensate for any irregular interior surface of the pipe. The plug length shall be suitable for the specific application. Plugs shall be equipped with continuous pressure monitoring and an audible alarm when the pressure drops below the minimum pressure recommended by the manufacturer. The installed pressure shall be as recommended by the manufacturer for the application. The eye-lifts shall be secured to a 5/8-inch diameter stainless steel pulling cable accessible for removal without entry. Inflatable plugs should be installed immediately upstream from the dry manhole to aid emergency removal of the plug. A double block and bleed may be required to protect workers per Cal OSHA regulations and requirements.

PART 3 - EXECUTION

3.1 TEMPORARY HANDLING OF SEWAGE

A. The CONTRACTOR shall construct, operate, maintain, and remove, without damage to existing structures, all temporary sewage handling facilities. OCSD forces will not assist the CONTRACTOR with flow handling during the Work. The CONTRACTOR shall submit details of proposed equipment for temporary handling of sewage flow as specified in Article 1.2. Requirements for operating the bypass system shall be as indicated herein and as shown on the plans. The system shall operate as specified to insure that neither the upstream nor downstream systems are threatened with sewage overload or spill.

B. Under no circumstances shall sewage or solids be deposited onto the ground surface, streets, or into ditches, catch basins or storm drains or natural drainage ways. Sewage shall be handled in a manner so as not to create a public nuisance or health hazard.

C. As soon as the bypass system is proved to be operating as specified, the CONTRACTOR shall stop the pump(s) and install and operate all backup pumps to prove their capability and establish a switchover time.

3.2 SPILL PREVENTION, CONTROL AND COUNTERMEASURE PLAN

The CONTRACTOR shall implement the Spill Prevention, Control and Countermeasure Plan as specified in this section and shown on the Plans. The CONTRACTOR may submit equivalent materials and methods for consideration.

A The CONTRACTOR shall submit for acceptance, all duty and emergency equipment for bypassing flow, containment, cleanup, and repair of any damage. Specifics for each bypass installation shall include as applicable, but are not limited to:

1. Pipe repair kits.

2. Sand bags.

3. Rubber matting.

4. Bypass pipes, spare pipe sections, pumps, and other relevant equipment.

5. Standby pumps.

6. Secondary containment in trench or other surrounding land relief.

C. The CONTRACTOR shall maintain standby and emergency equipment on site.

D. The CONTRACTOR shall provide the names, phone numbers, and hourly working schedules of at least three (3) people who can be contacted 24 hours per day by phone and that may be brought on-site at any time to address on-site emergencies. The CONTRACTOR shall provide notification of any substitution in writing at least two days in advance. When bypassing flows, CONTRACTOR shall have at least two people on site

24 hours per day to monitor and maintain the bypass and implement the emergency procedures in case of an emergency.

E. The CONTRACTOR shall protect storm drains during construction and its shop drawings shall show on the plans where the storm drains are located with relief features that could assist in containing the spill. The plans also shall indicate how storm drains will be blocked in the event of a spill: what material and how long will it take. The CONTRACTOR shall verify the time specified for each activity.

1. The CONTRACTOR shall identify those responsible for each activity, present a training plan for acceptance, and perform the accepted training.

2. The CONTRACTOR shall coordinate the plan with the construction storm water management requirements (see Section 02270, Storm water Pollution Prevention Plan) to protect water quality and respond to spills of sewage, groundwater, or fuels, ensuring there are no conflicts with implementing each of the respective programs. The CONTRACTOR shall implement all indicated spill prevention measures (e.g. monitoring of upstream manholes, monitoring in the trench).

F. The following spill procedures shall be followed by the CONTRACTOR and shall be included in the emergency and spill prevention plans.

1. If a spill is detected or a catastrophic pipe failure occurs, the immediate priority of the CONTRACTOR shall be to prevent any sewage from reaching storm drains and ultimately surface waters. A storm drain may be used for containment of a large spill if adequate preparations are made as indicated in the plans. The CONTRACTOR shall protect vulnerable drains using rubber mats or sand bags continuously during bypass or immediately (have all materials at hand) upon spillage.

2. The CONTRACTOR shall anticipate the following bypass system failure modes in the plan and be prepared to act accordingly.

a. If the bypass pump fails, begin using standby equipment as soon as possible.

b. In the event the bypass pipe is ruptured in a traffic accident or otherwise, the CONTRACTOR shall immediately stop the bypass pump, install containment as indicated in the plan, and notify the Control Center. Inform the Control Center what emergency diversion, if any, is indicated in the plan. Make repairs to the bypass pipe and restart the system. Begin cleanup. Notify the Control Center when the system is back in service.

3. The CONTRACTOR shall anticipate the following in-trench failure mode in its plan and be prepared to act accordingly.

a. As the CONTRACTOR is excavating for a new trench and comes across moderate leaks in the existing pipe, the CONTRACTOR shall make coupling/clamp repairs as soon as possible to minimize sewage flow into the trench.

b. If the leak is too large to make fast coupling repair, the CONTRACTOR shall start bypassing (see bypassing sequence below), then make repair.

4. In case of catastrophic in-trench leak, the CONTRACTOR shall immediately start the bypassing sequence:

a. Plug downstream side of the manhole upstream from the leak.

b. Insert Bypass Pump: The pump shall be sized to handle peak flow of existing sewer. Full capacity standby pumps shall be available for immediate installation at all times a bypass system is operating.

c. Connect Hose or Pipe from Pump to Discharge Point: NOTE: Hose or pipe shall already be in place and connected to a downstream discharge point at all times when working near or with live sewers. Hose shall only be allowed for emergency bypass systems.

5. In event of any spill, the CONTRACTOR shall immediately and in parallel with above activities, notify OCSD’s Control Center (714-593-7025) and request OCSD’s collections staff to be dispatched. The CONTRACTOR should attempt to give the best indication to the Control Center staff of the approximate size of the spill (<1,000 gallons is small; 1,000 gallons to 10,000 gallons is medium; and >10,000 gallons is large) along with the approximate amount, if any, of sewage discharged to a storm drain or channel so the appropriate response can be dispatched.

6. OCSD staff will respond to monitor the CONTRACTOR’s clean-up-related activities to ensure the spill is cleaned in accordance with this Plan. It is the CONTRACTOR’s responsibility to provide the primary means for pipe repair and spill recovery and clean-up including mobilizing any necessary equipment to be onsite within an hour of a spill. Clean up may require a sweeper truck, Vactor truck, water truck, and/or other equipment. All OCSD time and material and special equipment for spill cleaning will be deducted from the CONTRACTOR’s progress payment.

7. The CONTRACTOR shall attempt to pond the water in an area away from storm drains that can be easily and fully recovered for discharge to OCSD’s collection system. This ponding activity should not impact any environmentally sensitive areas.

8. The CONTRACTOR and ENGINEER with the assistance of OCSD’s collections staff shall coordinate the most efficient and appropriate response, repair, and cleanup of a spill as soon as possible. The CONTRACTOR will cooperate with OCSD staff to the fullest extent possible in order to minimize the impacts and volume of the spill in the most efficient manner possible.

9. Disinfection of a spill is not allowed (especially if the water is reaching State waters). All wash water and sewage-contaminated wash water must be contained and recovered in the same manner as the sewage.

10. The CONTACTOR shall have cameras on hand and shall document the spill, its cause, and the response activities as these occur with a video camera and photographs. The CONTRACTOR is required to attend a debriefing at the jobsite immediately after the spill is contained and cleaned up.

3.3 ODOR MITIGATION

The CONTRACTOR shall comply with the Odor Monitoring requirements as specified below:

A. The CONTRACTOR shall prepare a listing of all potential construction activities that might produce odors. For each of these construction activities, the CONTRACTOR shall include the scheduled construction date(s), expected construction duration(s), a listing of the potential receptors, and the distance to these receptors. Potential nuisance odor areas shall include open manholes, and open sewers where sewage gases can be present or can be released. Potential nuisance odor areas do not include covered manholes that are sealed or plugged (closed) sewer pipes.

B. All potential construction activities that might produce odors shall be identified on the Baseline Construction Schedule as required in the General Requirements. If multiple construction activities of this type are required simultaneously due to schedule constraints, multiple sets of gas analyzers shall be obtained and provided for monitoring by the CONTRACTOR.

C. For each site where potential odors may be produced, the CONTRACTOR shall prepare a plan for monitoring with the use of four gas analyzers. The high range gas (0-

200 ppmv) analyzers shall be located in the manhole and the three low range gas (0-2 ppmv) analyzers shall be located at the nearest receptors and at a height between 3 and

6 feet above the ground as accepted by the ENGINEER. The CONTRACTOR shall utilize the Air Quality Monitoring Logistic Report form or approved similar form to report and document construction and monitoring activities. The CONTRACTOR shall submit each monitoring plan in the form of a Shop Drawing Submittal for review and acceptance prior to conducting monitoring.

D. The CONTRACTOR shall obtain fully functioning and calibrated hydrogen sulfide gas analyzers to measure hydrogen sulfide emission concentrations from potential odor areas during construction. The CONTRACTOR shall obtain three low range hydrogen sulfide gas analyzers, and one high range hydrogen sulfide gas analyzer. The hydrogen sulfide gas analyzers shall be Odalog as manufactured by App-Tek International Pty Ltd, Model

3000RS manufactured by AMI, Or Equal. The low range hydrogen sulfide gas analyzers shall be capable of measuring and logging hydrogen sulfide gas concentrations between

0.01 and 2 ppmv. The high range hydrogen sulfide gas analyzer shall be capable of

measuring and logging hydrogen sulfide gas concentrations between 0 to 200 ppmv. The CONTRACTOR shall also obtain one software kit for downloading data from the gas analyzer, and one calibration kit for calibrating the gas analyzer per the manufacturer requirements. All gas analyzers and accessories that are purchased by the CONTRACTOR shall become the property of OCSD at the end of the Project. The analyzers shall be in good working order when turned over to OCSD. The software and calibration kits shall also be provided at the same time.

Prior to purchase, the CONTRACTOR shall submit a shop submittal for review and acceptance. The CONTRACTOR shall ensure that the gas analyzers are calibrated by the manufacturer.

E. After acceptance of the monitoring plan for the specific construction site where odors are anticipated, the CONTRACTOR shall notify the ENGINEER at least forty-eight (48) hours in advance of the proposed Work.

F. The CONTRACTOR shall, prior to the commencement of any Work, install all gas analyzers as described on the reviewed shop submittal.

G. The CONTRACTOR shall determine the means of achieving less than 10 ppbv at the receptors, as required in the General Requirements, prior to the commencement of all Work. Where odor mitigation measures are planned, they shall be in place during the construction period.

H. The CONTRACTOR shall download and record the readings of the hydrogen sulfide gas concentrations daily and present these results in a tabular format to the ENGINEER. Readings shall be logged at an interval to be determined by the ENGINEER. Readings shall be organized in a way that specifies which gas analyzer was used and the location of the analyzer. The CONTRACTOR shall utilize the Air Quality Monitoring Logistic Report form or approved similar form to report and document construction and monitoring activities. The CONTRACTOR shall provide these organized readings to the INSPECTOR at a frequency to be determined by the ENGINEER (which may be daily or less frequently).

I. OCSD may choose to download the data directly from the hydrogen sulfide gas analyzers that the CONTRACTOR has set up on-site. OCSD may also set up independent hydrogen sulfide gas analyzers at the construction site for additional monitoring. If the CONTRACTOR’s hydrogen sulfide gas analyzer readings do not reasonably correlate with OCSD’s hydrogen sulfide gas analyzer readings, the ENGINEER may require calibration of all gas analyzers, and reevaluation of the monitoring set up.

J. The CONTRACTOR shall record the wind speed and prevailing wind direction where the high range gas monitor has been installed. Depending on wind speed and direction, the CONTRACTOR may be required by the ENGINEER during the course of construction to adjust the locations of the three low range gas analyzers so that at least one of the three low range gas analyzers remains directly downwind of the high range gas monitor and the remaining two monitors also relocated as appropriate.

K. If hydrogen sulfide concentrations exceed 10 ppbv at any of the low range gas monitors (OCSD or CONTRACTOR) during the course of construction Work activities, the CONTRACTOR shall invoke the Odor Assessment and Odor Control Plan (OAOCP) for mitigation, and notify the ENGINEER immediately. If the CONTRACTOR fails to mitigate ambient hydrogen sulfide concentrations below 10 ppbv at the receptors using OAOCP, the CONTRACTOR shall stop Work immediately and coordinate with the ENGINEER on further odor mitigation and control prior to commencement of Work at the site where odors are released.

L. The CONTRACTOR shall abide by the following Odor Assessment and Odor Control Plan (OAOCP), at a minimum, to prevent emissions of nuisance odors when hydrogen sulfide concentrations exceed 10 ppbv during the course of construction Work:

a. Cover manholes and openings where bypass pumps are used with plywood or other approved material, including sealing cracks and edges with sealing putty or caulking. Ensure that all covers are secure, safe from vandalism and safe from potential life and safety hazards (i.e. falling or tripping hazards).

b. Seal open sewer pipes during tie-ins.

c. Keep the duration of open manholes to a minimum. d. Plug sewers as necessary to reduce odor emissions.

e. Provide in-line bypasses in closed conduits when working in manholes.

f. Reasonably prevent sewer gases from escaping the construction work area.

M. If OCSD staff determines that odor control is required during construction, the CONTRACTOR shall coordinate with OCSD staff for odor control and mitigation requirements. All chemical, liquid or vapor treatment measures will be provided by OCSD. Other forms of treatment by the CONTRACTOR will be considered on a case by case basis.