M 41-10 Page 8-153 Temporary Stream Diversion 8-318-31 Temporary Stream Diversion
8-31.1 Description
This work shall include planning, designing, installing, operating, maintaining, removing, and disposing of the temporary stream diversion, environmental compliance and other Work as detailed in these Specifications.
8-31.2 Materials
All materials shall be as detailed in the Contractor’s temporary stream diversion (TSD) Plan.
8-31.3 Construction Requirements
8-31.3(1) General
8-31.3(1)A General TSD Requirements
The Work shall include compliance with Washington State Water Quality Standards in WAC 173-201A, project permits, environmental commitments, and these Provisions. The temporary stream diversion may be either a gravity or a pumped system. Pump screens must comply with the requirements in Section 8-31.3(4) . Once a pumped diversion begins, the pump must run continuously until it is no longer necessary to bypass flows. At all times of operation, the Contractor’s temporary stream diversion(s) shall not restrict flows to less than the minimum flow rate(s) specified in the contract documents. The Contractor shall have back-up pumps on site and shall provide twenty- four-hour monitoring of the pumping operation. Monitoring can be achieved by providing monitoring personnel on site or by agreement with regulatory agencies through remote sensing and instrumentation to verify operation of the bypass. If the Contractor elects to monitor by remote sensing and instrumentation, a Type 2 Working Drawing shall be submitted outlining how system operation will be monitored, how alerts will be made and how personnel will respond to a diversion system failure. The temporary stream diversion, including water that is retained by the temporary stream diversion and the dewatering system, shall be located within the permitted impact areas as shown in the Plans. The upstream diversion dam shall be constructed to a height sufficient to prevent stream flow from entering the work area. Scour protection shall be provided at the outfall of the temporary stream diversion systems and dewatering system to prevent flow re-entering the stream channel from mobilizing streambed and embankment sediments. When a temporary stream diversion is located in or near an intertidal zone the temporary stream diversion design shall take tidal influence into consideration. When required by the Contract, the Contractor shall have a contingency plan for each temporary stream diversion to be used in the event of a storm producing streamflow in excess of the design flow requirement, equipment failure, vandalism, or other incident. A complete set of equipment and materials for the contingency system shall be available for each temporary stream diversion. The Contractor shall immediately implement the contingency system when required or specified by the Engineer. The contingency system shall be designed to be fully operational within 2 hours.
8-31.3(1)B TSD Plan Implementation Meeting
For each temporary stream diversion, the Contractor shall arrange a TSD Plan Implementation Meeting with the Engineer prior to implementation of the TSD Plan. At this meeting, the Contractor shall explain to the Engineer the Work to be completed for the temporary stream diversion. The meeting shall be held a minimum of 7 calendar days prior to start of the fish block net installation associated with the temporary stream diversion Work. The Contractor shall notify the Engineer 14 calendar days prior to the meeting taking place. Page 8-154 M 41-10
8-31 Temporary Stream DiversionThose attending shall include:
1.Representing the Contractor: The superintendent, on site supervisor, foreman, the Environmental Compliance Lead and other personnel that will have on-site responsibility for implementing the Temporary Stream Diversion.
2.Representing the Contracting Agency: The Engineer, WSDOT Headquarters Hydraulics, key inspection personnel, and other appropriate WSDOT staff.
3.Representatives from interested permitting agencies and affected Tribes will be invited by the Contracting Agency. The Project Engineer will arrange for these interested parties to attend the TSD Plan Implementation Meeting. The TSD shall be operational prior to performing Work below the ordinary high-water line as required to achieve permit compliance.
8-31.3(2) Temporary Stream Diversion Plan
8-31.3(2)A General Plan Requirements
The Contractor shall submit a temporary stream diversion plan in accordance with the requirements of a Type 2E Working Drawing and these Specifications. A separate TSD Plan shall be prepared and submitted for each temporary stream diversion. The Contractor shall fully implement the TSD Plan throughout the duration of the associated Work. The Contractor shall update the TSD Plan throughout project construction to reflect actual site conditions and the Contractor’s Work. Changes to plan shall comply with WAC 196-23-020. At the request of the Engineer, an updated TSD Plan shall be submitted as a Type 2E Working Drawing. A copy of the TSD Plan shall be on the project site at all times. The TSD Plan shall describe measures that will be taken to comply with Washington State Water Quality Standards in WAC 173-201A , applicable permits, environmental commitments, and the Specifications and Contract Provisions. The Contractor shall incorporate Section 8-31.3(2)B , item number 2 into their Progress Schedule.
8-31.3(2)B Plan Requirements
At a minimum, the TSD Plan shall provide the following information in the following order:
1.Description and Location of the temporary stream diversion
a.Identify the name of the water body where the temporary stream diversion will be placed. Provide a description of the temporary stream diversion.
b.Provide drawings showing each of the locations of the temporary stream diversion components, including proposed access routes and equipment to be used to construct the diversion.
2.Schedule and Sequence
a.Provide a schedule showing the following activities that illustrate how the Work will be completed within the in-water work window in the Special Provisions:
i.TSD Plan Implementation Meeting. ii. Fish Block Net Installation and Fish exclusion (performed by the Contracting Agency). iii. TSD installation. iv. Dewatering of the isolated work area.
v.Restoration and stabilization of the temporary stream diversion work area to prevent erosion. M 41-10 Page 8-155 Temporary Stream Diversion 8-31vi. Relocations of the temporary stream diversion to accommodate the work sequence (if needed). vii. Channel rewatering. viii. Removal of the TSD. ix. Fish block net removal (performed by Contracting Agency).
b.Include other Work that needs to be coordinated with the TSD (e.g., temporary erosion control).
3.Calculations and Materials
a.Detail all elements of the temporary stream diversion; including but not limited to pipes, pumps, screen intake elements, and other equipment and materials.
b.Calculations shall demonstrate the diversion system conveys the minimum peak flow specified by the Contracting Agency and include tidal influence where applicable.
c.Temporary stream diversion shall include a water conveyance system to be used for dewatering and rewatering that is capable of conveying the flow required for the temporary stream diversion.
d.Methods for anchoring temporary stream diversion pipe and associated hardware; include calculations to demonstrate the device's ability to anchor the pipe and associated hardware.
e.Specifications for all materials and equipment to be used as part of the diversion including pump or diversion capacities and hose sizes. For example, provide the type, profile, and size of pipe.
f.Provide the size of fish screens (mesh size and surface area) to be used, in accordance with Section 8-31.3(4) .
g.Detail where bags will be used for temporary stream diversion. Bags shall comply with the requirements of the HPA and be filled using clean pea gravel. Clean pea gravel is pea gravel that does not cause an exceedance of the allowable turbidity in the stream or waterbody.
4.Stream Flow Blocking and Dewatering
a.Provide the method(s), including locations and details (narrative and drawings) for blocking both the upstream and downstream ends of the diversion. Describe how minor leakage from upstream and downstream will be addressed.
b.Include provisions for scour protection at the temporary stream diversion outfalls.
c.Identify the means and methods for dewatering and disposal of the water.
5.Contingency Plan (when required)
a.The Contractor shall include the details of the system in the TSD Plan sections that are applicable.
b.Describe the Work that will be implemented to prevent the work area from becoming inundated.
c.Provide the type and size of materials that will be used in the event of the work area becoming inundated, including fish exclusion coordination with Contracting Agency if the block nets are compromised.
d.Describe how the contingency equipment and materials will be stored, inspected and maintained so they are ready for use if required.
e.Describe how the contingency system will deployed and operational within 2 hours. Page 8-156 M 41-10
8-31 Temporary Stream Diversion6. Inspection and Maintenance
a.Provide the schedule and frequency for inspection of the temporary stream diversion including the emergency contact information for the individuals inspecting and/or repairing, include weekends and holidays.
b.Describe how maintenance and Contracting Agency notification will be conducted when inspections identify deficiencies in the temporary stream diversion. These include but are not limited to removal and disposal of trapped sediment or debris and repairing leaks.
c.The Contractor shall keep a record of all inspections and maintenance of the temporary stream diversion and shall provide the records to the Engineer when requested.
d.The Contractor shall notify the Engineer within 12 hours of an emergency repair.
7.Rewatering the Stream Channel
a.Detail how the stream channel will be rewatered to comply with water quality requirements.
b.Identify measures that will prevent the stranding of fish during rewatering (i.e. describe methods, rates, and durations of the rewatering process knowing that flows downstream of the fish block must be maintained to protect fish).
8.Removal of the temporary stream diversion
a.Describe the sequence that will be used for removing the temporary stream diversion and methods to prevent exceeding allowable water quality standards.
b.Describe how disturbed soil will be permanently stabilized.
c.Describe temporary pipes, if, to remain (requires approval of the Engineer): their type, pipe class, size, location, and plugging procedure.
9.Other Work required for the Contractor’s temporary stream diversion
8-31.3(3) Fish Block Net Installation and Fish and Aquatic Species Exclusion
The Contractor shall notify the Engineer in writing a minimum of 14 calendar days before fish block net installation and fish and aquatic species exclusion is scheduled and before performing in water work. The Contractor shall allow the Contracting Agency 7 calendar days for the following:
1.To install fish block nets upstream and downstream of the in-water work area; and
2.Safely capture and relocate all fish and other aquatic organisms that become trapped between the block nets. No Work within the limits of the Ordinary High-Water Line will be allowed prior to installation of fish block nets and completion of fish exclusion activities.
8-31.3(3)A Fish Exclusion Assistance
As directed by the Engineer, the Contractor shall assist the Contracting Agency with fish and aquatic species exclusion.
8-31.3(3)B Contracting Agency Provided Materials
The Contracting Agency will provide and install the fish exclusion materials as listed in the Special Provisions or Plans. M 41-10 Page 8-157 Temporary Stream Diversion 8-318-31.3(4) Dewatering Work Areas Dewatering the isolated in-water work area (between the upstream and downstream diversion dams) shall occur at a rate slow enough to allow the Contracting Agency to safely capture and relocate all fish species and other aquatic organisms to avoid stranding, as determined by the Engineer. All pumps used for dewatering shall have an intake covered with a fish screen, operated, and maintained in accordance with RCW 77.57.010 and RCW 77.57.070 . Appropriate fish screens are as follows:
1.Perforated plate: 0.094 inch (maximum opening diameter);
2.Profile bar: 0.069 inch (maximum width opening); or
3.Woven wire: 0.094 inch (maximum opening measured on the diagonal). The minimum open area for all types of fish screens is 27 percent. The screened intake facility must have enough surface area to ensure that the velocity through the screen complies with the velocity provided within the Hydraulic Project Approval (HPA). If no velocity is provided within the HPA, the maximum approach velocity shall not exceed 0.33 feet per second. The fish screen must remain in place whenever water is withdrawn until the Contracting Agency Biologists confirm all fish have been removed. At that point, the Contractor may remove the fish screen to finish dewatering the work area.
8-31.3(5) Inspection and Maintenance
At a minimum, the Contractor shall perform the following activities once per day (including weekends and holidays):
1.Check for and correct leaks;
2.Ensure the fish block nets remain sealed to the channel substrate; and
3.Check inlet for proper function. The fish block nets shall be kept clear of debris that could jeopardize the integrity of the nets. The Contractor shall perform the following activities a minimum of three times per day or when requested by the Engineer. On working days, these activities shall be performed at the start, middle, and at the end of the working day. On non-working days, these activities shall be performed between 6:00 am and 8:00 am, between 11:00 am and 1:00 pm, and between 4:00 pm and 6:00 pm:
1.Inspect the upstream and downstream fish block nets and remove debris;
2.Inspect the upstream fish block net and all screens and similar facilities for impinged fish; and
a.The Contractor shall immediately notify the Contracting Agency when impinged fish are discovered.
b.Removal of impinged fish will be performed by the Contracting Agency. The Contractor shall maintain a written record of all inspection and maintenance activities; record to be available at the request of the Engineer. The Contractor shall assist the Contracting Agency with block net maintenance, as specified.
8-31.3(6) Channel Rewatering and Removal of TSD Components (Except Nets)
The Contractor shall notify the Engineer a minimum of 7 calendar days in advance of rewatering the stream channel. This notification shall include a schedule of activities from the start of rewatering the channel to the final removal of all stream diversion components. The Contractor shall introduce water to the new stream channel section and trap sediments until the stream section meets the requirements of these Provisions. Page 8-158 M 41-10
8-31 Temporary Stream DiversionRewatering shall occur at a rate to avoid loss of surface water downstream while the new
channel section is rewatered. Once the water in the new stream channel meets the applicable turbidity standards the Contractor may begin removal of the temporary stream diversion and the stream channel opened to flows. The Contractor shall immediately take all corrective actions necessary to prevent the water from exceeding the turbidity standards should the stream turbidity increase. All Work within the channel, except for removal of the temporary erosion control items, shall be completed before the temporary stream diversion is removed. The Contractor must finish all construction activities within the limits of the Ordinary High-Water Line, including but not limited to culvert installation and creek bed channel restoration, before the Contracting Agency will remove the fish block nets.
8-31.3(7) Removal of Fish Block Nets
The Contractor shall allow 7 calendar days for Contracting Agency removal of the fish block nets.
8-31.3(7)A Contractor Provided Labor
The Contracting Agency will remove the fish block nets.
8-31.3(7)B Contracting Agency-Provided Materials
All materials used for the diversion shall become the property of the Contractor and removed from the project limits, except for the materials supplied by the Contracting Agency.
8-31.4 Vacant
8-31.5 Payment
Payment will be made for the following Bid item when it is included in the Proposal: “Temporary Stream Diversion____”, lump sum. The lump sum Contract price for “Temporary Stream Diversion____” shall be full payment to perform the Work as specified. Progress payments for the lump sum item “Temporary Stream Diversion” will be made as follows:
1.Twenty-five percent of the bid amount will be paid following completion of the TSD Plan including resolution of all Contracting Agency review comments.
2.The remaining seventy-five percent of the bid amount shall be paid in accordance with Section 1-09.9 . “Fish Exclusion Assistance”, by force account as provided in Section 1-09.6 . To provide a common Proposal for all Bidders, the Contracting Agency has entered an amount in the Proposal to become a part of the Contractor’s total Bid. “Fish Block Net Maintenance”, by force account as provided in Section 1-09.6 shall be full payment for removal of debris from the fish block nets or other assistance required by the Engineer. When the block nets are staffed and the person staffing the nets are in standby mode, no payment will be made. Time spent actively removing debris or making adjustment to the blocks nets are eligible for payment under this item, all other costs associated with the maintenance of the temporary stream diversion system is included in the lump sum item “Temporary Stream Diversion.” Fish block nets damaged due to the Contractor’s operation shall be repaired or replaced by the Contractor at no expense to the Contracting Agency. To provide a common Proposal for all Bidders, the Contracting Agency has entered an amount in the Proposal to become a part of the Contractor’s total Bid.
Source: Washington Standard Specifications for Road, Bridge, and Municipal Construction, 2024 Edition. Pages 903–908 of 1,151.