33 40 00 - Temporary Flow Diversion and Bypass Pumping (1).pdf

OCWRC FKE EFSD Outlet Siphon 33 39 14 - 1

SECTION 33 40 00

TEMPORARY FLOW DIVERSION AND BYPASS PUMPING

PART 1 - GENERAL

1.1 SUMMARY

1.1.1 This section includes specifications for flow control through temporary flow diversion and bypass pumping to support the Work being performed as part of the Oakland County Water Resources Commissioner Evergreen Farmington Sanitary Drain (EFSD) Walnut Lake #1 Pump Station C.A.P. Modification Phase #2. This Work consists of the following items:

1. The existing inverted siphons at the EFSD outlet are proposed to be replaced with a typical gravity sewer alignment.

2. A local City of Southfield sewer that currently connects to Manhole SOT140002 is proposed to be connected via a new structure on the 96-inch GLWA Outlet Sewer.

1.1.2 List of entity acronyms

1. EFSD – Evergreen Farmington Sanitary Drain

2. WRC – Oakland County Water Resources Commissioner

3. GLWA – Great Lakes Water Authority

4. DWSD – Detroit Water and Sewerage Department

5. EGLE – Michigan Department of Environment, Great Lakes, and Energy

1.1.3 The Work is in active sanitary sewers with continuous flows. Conveyance of flow in the EFSD must not be interrupted by the Work. Therefore, if execution of the work cannot be performed in the depths and velocities of typical dry weather flow, then flow diversion or bypass pumping is required to reduce or eliminate the flow in the pipe segment being worked on.

1. For the replacement of the existing inverted siphons at the EFSD outlet with a typical gravity sewer alignment.

a. Flow Diversion at EFSD Outlet – EFSD Outlet Sewer normally discharges into the GLWA First-Hamilton Sewer, however an alternate connection to the DWSD Southfield Road Sewer is available through the operation of gates and is the route flows historically took prior to the construction of the GLWA First-Hamilton Sewer. Opening the gate to the DWSD Southfield Sewer, and closure of the existing Melrose isolation gate and the isolation gate at MH SOT140002 is required to stop flow to the EFSD Outlet and redirect

33 39 14 - 2 this flow to the DWSD Southfield Road Sewer. Figure 1 presents an overview map of the EFSD Outlet and the two discharge routes. For construction activities that require no flow through the existing EFSD outlet siphon, redirection of flows through the alternate connection to the DWSD Southfield Road Sewer is the primary and recommended flow control method. This flow diversion is subject to certain conditions and will not be available for wet weather conditions as defined in the monitoring plan (see Spec. Section 1.2.1.6), see Spec.

Section 3.2.4 for information to aid in planning with this constraint.

b. Flow Through Modified Existing Pipe at EFSD Outlet – Once the existing pipe is modified, it is available to carry flows through the worksite during the construction activities for the new pipe. This modified existing pipe can carry dry weather and wet weather flows.

The modification will reduce the flow rate capacity and coordination with WRC operations staff will be necessary to minimize upstream impacts during wet weather conditions as defined in the monitoring plan (see Spec. Section 1.2.1.6).

c. Bypass Pumping at EFSD Outlet – As an alternative to the “Flow

Diversion” (see Spec. Section 1.1.3.1.a) or “Flow Through Modified Existing Pipe” (see Spec. Section 1.1.3.1.b) flow control methods, flows may also be bypass pumped around the work extent, if contractor elects this alternative flow control method. The bypass pumping plan would need to address the total peak flow rate for a 25-year, 24-hour design storm event, which is 227 cubic feet per second.

d. Flow Diversion at EFSD Outlet for Project Activities that Require No

Flow in Both Existing and New Pipes – The project activities include abandonment of the existing sewer through flowable fill and manhole channel finishing. Special flow control as follows is needed for these activities.

For Short Durations (up to 8 hours): Flow rates in the EFSD vary daily, seasonally, and with rainfall/snowmelt patterns, which may result in this time increasing or decreasing from the estimated 8 hours for a specific day, current durations for each use of this Short Duration flow control are to be estimated by the Flow Control Manager based on recorded data from the one week period prior to the use of the Short Duration flow control and forecasts of performance during the planned use of the Short Duration flow control. Short Duration flow control at this location is achieved by the following: Coordinate with EFSD Operations staff for flow storage at Middlebelt Transport and Storage Tunnel (MTST), flow storage upstream of 8 Mile Pump Station, flow storage upstream of the new

33 39 14 - 3 gate in the 8 Mile SSO Chamber, closure of the Melrose isolation gate, opening the gate to the DWSD Southfield Sewer for any flow contributed downstream of the 8 Mile SSO Chamber, and EFSD-wide coordination for avoidance of inadvertent elevated depths through operations of other facilities.

For Long Durations (greater than 8 hours): All measures described for setting a plug in the incoming 78-inch sewer (southern pipe), then the Melrose isolation gate is closed and the gate to DWSD Southfield Sewer to remain open and all other facilities can return to normal operations.

Both Short and Long Duration flow control for Manhole SOT140002 are unavailable on any day determined to be a wet day as defined in the monitoring plan (see Spec. Section 1.2.1.6), see Spec. Section

3.2.4 for information to aid in planning with this constraint.

1. For the construction of a new manhole on the local City of Southfield sewer and the new connection to the 96-inch GLWA Outlet Sewer from the new structure along the local City of Southfield sewer:

a. Bypass Pumping for the local City of Southfield Sewer – This is the recommended flow control method for this local City of Southfield sewer. A suitable suction manhole exists upstream of the planned point of connection to the 96-inch sewer and a suitable discharge manhole exists downstream of the proposed planned point of connection to the 96-inch sewer. See Spec. Section 3.2.10.1 for flow rate and manhole information.

b. Flow Through Existing Pipe for the local City of Southfield Sewer – As an alternative to “Bypass Pumping” (see Spec. Section 1.1.3.2.c), contractor may elect to support the existing pipe through the excavation and continue flow through the existing pipe until the connection via the new structure can be made. Maintaining flow through the existing pipe is not recommended since the existing pipe and support system will be a significant obstacle to completing the construction of the new structure.

1.1.4 Existing area velocity flow meters are installed on each of the incoming and/or outgoing interceptor pipes at the Work extent. These flow meters will be used to review current system conditions prior to commencing flow diversion and bypass pumping activities.

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Figure 1. Overview Map of EFSD Outlet Sewer

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1.1.5 Wet weather conditions in the EFSD are characterized by flow depths that surcharge the interceptor pipes. This surcharging is due to a combination of the magnitude of flows, pipe capacities, and downstream backwater conditions

1.2 SUBMITTALS.

1.2.1 The design, installation, and operation of the temporary flow diversions and bypass pumping system shall be the Contractor's responsibility. The bypass system shall meet the requirements of all codes and regulatory agencies having jurisdiction. Prior to beginning any work, the Contractor is required to prepare and submit a Flow Diversion and Bypass Pumping Plan for each set-up that includes:

1. A plan view layout showing the suction and discharge manholes, suction and discharge piping routes, access paths, and staging areas for pumps, generators, and other equipment.

2. Locations and details of temporary modifications to the existing sewer such as sewer plugs and diversion dams, if any.

3. Locations and details of temporary pipe supports and anti-meandering provisions such as thrust blocks, joint restraints, and wall anchoring, if any.

4. A schedule for the installation, expected duration, and frequency of flow diversion and/or by-pass pumping operations.

5. A maintenance plan for ensuring general pump and equipment upkeep and working order of the bypass system. This plan must include maintenance frequency and measures for how potential ragging or clogging issues will be addressed and disposal of debris cleaned during the bypass period.

6. A monitoring plan for measuring and recording upstream and downstream levels and flow rates through the flow diversion or bypass pumping system. Development of the monitoring plan is to be completed by Contractor’s Flow Control Manager, which is to be Applied Science, Inc.

Include a list of personnel responsible for monitoring bypass pumping operations. The monitoring plan shall provide for no flow diversion to the DWSD Southfield Sewer on any day determined to be a wet weather day.

The monitoring plan shall provide for resumption of flow diversion to the DWSD Southfield Sewer will occur if a day is determined to be 1) a non-wet weather day by the Flow Control Manager and their contacts at GLWA, DWSD, Oakland County WRC and the Contractor and 2) a contract working day when the activities require the diversion. The

33 39 14 - 6 monitoring plan shall require the Flow Control Manager to consult a team at GLWA, DWSD, Oakland County WRC and the contractor to determine wet days based on:

a. Forecasted rainfall for the following day (to pre-designate a wet weather day),

b. Flow rates at the EFSD outlet (measured by either Meter 3001, Meter 3003 or the sum of Meters 3000, 3010 and 3030), in the Hubbell- Southfield Sewer (Meter DT-S-3) and/or in the Northwest Interceptor (Meter DT-S-1),

c. Depth in the Hubbell-Southfield Sewer (Level Sensor L-199), and

d. Operator override of metric-based wet day determinations (such as for a known shutdown or an emerging situation).

7. Size, length, quantity, and material of all piping and valves.

8. Product specification sheets for pumps, valves, piping, generators, and other equipment utilized for each set up.

9. Total dynamic head (TDH) requirements of the pumping system including static lift, friction losses, minor losses, and flow velocities. Pump curves shall be included in the TDH analysis to show expected operating range.

10. Method of protecting discharge manholes or structures from erosion or damage.

11. Standby power generation size, location, and determination.

12. Modifications needed to manholes, if any, and subsequent restoration plan.

13. Traffic, noise, and odor control measures.

14. A Bypass Pumping Notifications and Emergency Contact Plan that includes:

a. Notification of Owner and Engineer 24 hours prior to initiating any flow diversion or bypass pumping.

b. 24 Hour Emergency Contacts to include Prime Contractor, All Sub-

Contractors, Fuel Delivery, and Replacement Equipment.

15. Emergency plan for adverse weather, flooding, accidents, or equipment

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PART 2 – PRODUCTS

Not Used

PART 3 – EXECUTION

3.1 FIELD INVESTIGATIONS AND TESTING

3.1.1 Prior to beginning any work, the Contractor shall conduct the necessary field investigations to locate existing manholes, determine clear space within the manhole structure, and measure wastewater depths. No allowances shall be made for conditions found during the progress of the work due to the Contractor’s failure to verify such conditions.

3.1.2 The temporary bypass pumping discharge piping shall be leak and pressure tested prior to conveyance of any sanitary sewage. The pressure and leakage test shall be conducted at one-and-a-half times the maximum pressure the system will experience based on the approved Bypass Pumping Plan for a period of two hours.

3.1.3 The Contractor shall test and verify that the temporary bypass pumping set-ups will maintain wastewater depths to acceptable depths. Reporting of the test runs is required prior to the commencement of the rehabilitation work.

3.1.4 The Contractor shall obtain access rights from private property owners when access across private property is necessary to reach manholes.

3.2 FIELD INVESTIGATIONS AND TESTING

3.2.1 No construction shall begin until the Flow Diversion and Bypass Pumping Plan has been reviewed and approved by the Engineer.

3.2.2 The Contractor is to furnish all materials, labor, equipment, power, and maintenance to implement a temporary pumping and monitoring system for the purpose of diverting the existing flow around the work area for the duration of the project. Adequate stand-alone power is required regardless of the availability of a dedicated electrical service.

3.2.3 Flow diversion and/or temporary bypass pumping to perform rehabilitation work will only be undertaken during dry weather conditions when the tributary flow rates are within the discharge capacity of the flow diversion or bypass pumping set-up.

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3.2.4 Flow rates in the EFSD vary daily, seasonally, and with rainfall/snowmelt patterns; these factors will impact the determination of wet weather days.

Through implementing the monitoring plan, the Flow Control Manager shall identify wet weather days. When wet weather conditions occur, the Contractor shall cease flow diversions at the EFSD Outlet. During these conditions, gravity flow shall be restored through the existing EFSD Outlet and/or the constructed portions of the new outlet sewers being built under this project through the operation of gates and the removal of any sewer plugs, materials, and equipment from the EFSD outlet gravity flow route within at least two hours from the start of a wet weather event.

3.2.5 The Contractor shall assume that, on average, two of every seven calendar days will be wet weather days, meaning that flows will not be able to diverted to the DWSD Southfield Sewer. The Contractor shall also assume one workday per month, on average, will be considered an Owner maintenance day where work will be precluded in all or part of the EFSD.

3.2.6 Flow rates in the 21-inch local City of Southfield sewer vary daily, seasonally, and with rainfall/snowmelt patterns. For the connection of the 21-inch local City of Southfield Sewer to the new manhole, it is anticipated that there will be points of time in the project when flow cannot be restored to the existing pipe, therefore, the bypass pumping system must be capable of passing wet weather flow rates (see Drawing FC-1 for recent five-year history). Through review of metered flow rates on 21-inch local City of Southfield Sewer, up to 11.7 cfs has been recorded during wet weather in the recent fifteen-year period.

3.2.7 For some items of work, extended periods of dry weather are required. No additional compensation shall be given to the Contractor for the suspension of Work due to wet weather conditions.

3.2.8 Following wet weather, the Contractor shall clean work areas and repair work damaged by wet weather, if any, at no additional cost to the Owner.

3.2.9 Bypass pumping equipment shall be capable of handling typical sanitary sewer solids, trash, rags, and debris. The Contractor shall maintain equipment in good working order at all times. At a minimum, the pumps must be capable of passing a 3-inch solid.

3.2.10 Each bypass pumping setup shall have a capacity of at least twice the maximum dry weather flow rate of the bypassed sewer.

1. Meter 3030 is located along the City of Southfield sewer and will be relocated by others. Based on this meter’s data, the maximum dry weather flow rate of this sewer is about 1.7 cfs (see Drawing FC-1 for a summary of recorded flow rate data). For the connection of the 21-inch local City of Southfield Sewer to the new manhole, it is anticipated that there will be

33 39 14 - 9 points of time in the project when flow cannot be restored to the existing pipe, therefore, the bypass pumping system must be capable of passing wet weather flow rates. Note that in the period of January 2020 through December 2024 a peak flow rate of 8.1 cfs was recorded; in a fifteen-year period, a peak flow rate of 11.7 cfs was recorded. The bypass pumping plan must address peak flow rates similar to these values, should they occur while bypass pumping as active.

3.2.11 During bypass pumping operations, the Contractor shall have an extra redundant pump of equivalent capacity available on site.

3.2.12 All sanitary customers of the sewer system shall be provided uninterrupted service.

3.2.13 The Contractor shall provide a dedicated operator on-site for each bypass pumping system whenever the bypass pumping system is in operation to monitor conditions and performance, ensure proper operation, and facilitate removal of any sewer plugs and restoration of gravity flow as conditions dictate. Operators shall be properly trained, experienced, and mechanically qualified such that they can quickly and effectively address any potential emergency and non-emergency situations associated with the pumps and bypass pumping system.

3.2.14 The Contractor is responsible for cleaning of debris that collects on equipment and properly disposing of such debris material.

3.2.15 The Contractor is solely responsible for the safety of personnel, vehicles, equipment, material, and tools used by the Contractor to perform the bypass pumping work.

3.2.16 The Contractor shall remove any manhole frames, covers, cones, and steps as required to provide clear access to perform the flow diversion and bypass pumping work.

3.2.17 The Contractor shall provide any necessary traffic control.

3.2.18 The Contractor shall provide site security measures.

3.2.19 The Contractor shall clean any sediment, sludge, bricks, rubble, and debris from the pump intake area prior to the installation of the bypass pumps.

3.2.20 The Contractor shall not leave any vehicles, equipment, tools, or materials in the sewer when gravity flows are restored.

3.2.21 The Contractor shall be solely responsible for any basement back-ups, flooding, and damage caused by failure of the Contractor’s or Sub-contractor’s equipment, or from any vehicles, equipment, materials, and tools that are left in the sewer.

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3.2.22 The Contractor shall not allow the sewage depths in the EFSD or community connections to increase to levels that create the risk of basement back-ups or spilling of wastewater to the environment.

3.2.23 The Contractor shall restore the manholes, lawns, plantings, and pavement to conditions equivalent to the pre-existing conditions.

3.2.24 The Contractor shall be required to repair, at no additional cost to the Owner, any damage to public or private property caused by their operations.

3.2.25 Should damage of any kind occur to the existing sewers, the Contractor shall, at no additional cost to the Owner, make repairs to the satisfaction of the Engineer and the governing agency having jurisdiction of the existing sewer.

3.2.26 The Contractor shall not be permitted discharge sanitary sewage to the environment.

3.2.27 Upon the cessation of bypass operations, the Contractor shall restore normal gravity sewage flow in a gradual and controlled manner such that the release does not cause surcharging or other disturbances downstream.

3.2.28 The Contractor shall immediately notify the Owner if a sanitary sewer overflow

(SSO) occurs and take the necessary action to clean up and disinfect the spillage to the satisfaction of the Owner and EGLE. If sewage is spilled onto public or private property, the Contractor shall wash down, clean up, and disinfect the spillage to the satisfaction of the property owner and/or other governmental agency.

3.2.29 When bypass operations are complete, all bypass piping shall be flushed with fresh water and drained into the wastewater system prior to disassembly and removal.

End of Section