SECTION_01_51_38_-_Diversion_and_Care_of_Water_R2_0004.pdf

BUREAU OF INDIAN AFFAIRS OGLALA DAM SPILLWAY AND OUTLET WORKS

OGLALA DAM SPILLWAY AND OUTLET WORKS SECTION 01 51 38

JUNE 2023 DIVERSION AND CARE OF WATER

FOR BID REV 2 PAGE 1 OF 8

SECTION 01 51 38

DIVERSION AND CARE OF WATER

PART 1 GENERAL

1.01 SCOPE OF WORK

A. This Section specifies the requirements for the following general items of Work:

1. Design two Water Diversion Systems (one for Construction Phases 1 and 2, and one for Construction Phases 3 and 4) to pass a minimum 25-year storm event at the site during temporary construction of the Work.

2. Installation, operation, and maintenance of a Water Diversion System during Construction Phases 1 and 2 which shall divert water through the existing outlet works and discharge downstream of the Work during service spillway construction. This includes installation of temporary diversion piping connecting the existing outlet works conduit to the channel downstream of the Work and installation of a temporary downstream cofferdam.

3. Removal of Phase 1 and 2 Water Diversion System.

4. Installation, operation, and maintenance of a Water Diversion System for Construction Phases 3 and 4 which shall divert water through the new outlet works during embankment construction. This includes installation of a temporary upstream cofferdam, and installation of diversion piping from the new outlet works to a discharge area downstream of the temporary downstream cofferdam.

5. Removal of Construction Phase 3 and 4 Water Diversion System which includes installation of a blind flange on the diversion piping at the inlet tower and removal of the temporary downstream cofferdams; the upstream cofferdam will be abandoned in place. The Phase 3 and 4 diversion piping will remain in place for future drawdown use if needed.

6. Maintain construction access during precipitation events.

7. The CONTRACTOR shall pass a minimum of 10 cfs or the inflows from White Clay Creek during the duration of the Work, with the following exception:

a. When necessary, outflows may be ceased for a period not to exceed 24 hours in a one week period.

1.02 PERFORMANCE

A. The Water Diversion Systems and temporary cofferdams will be capable of conveying the daily flow of the Oglala Reservoir plus sufficient volume to protect the Work up to a minimum of the 25-year flood inflow event.

B. Provide and implement the appropriate measures to protect the Water Diversion Systems from freezing temperatures.

BUREAU OF INDIAN AFFAIRS SECTION 01 51 38

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C. Provide and implement the appropriate measures to protect the Water Diversion Systems from clogging or damage by debris and sediment.

D. Perform operations, monitoring, and maintenance of the Water Diversion Systems to prevent delays.

1.03 SUBMITTALS

A. Shop Drawings

1. Submit a Diversion and Care of Water Plan for review and approval by the BIA Representative at least 15 days prior to mobilization. The plan should include:

a. Descriptions of the proposed methods for installation, operation, surveillance, control, and maintenance of the two Water Diversion Systems during all construction activities (mass excavation, demolition, construction of new outlet works and spillway). Address maintenance and supervision requirements during non-working hours (i.e., nights, holidays, and weekends).

b. Descriptions of the measures to be taken to meet the Project permits, applicable water right laws, and environmental controls requirements per Section 01 57 01

– Project Permits and Environmental Controls.

c. Details of each Water Diversion System element, materials to be used, sequencing for construction, design calculations for hydraulic capacity, and other related elements of the design. Materials shall include, but are not limited to, the cofferdam fill, diversion piping, valving, flanges, etc.

d. Water Diversion Systems designed by a Professional Engineer.

e. Cofferdam fill material test data.

f. Proposed method of lowering of water along with siltation control measures for any water that is discharged into the channel.

g. Shop drawings and sketches of the diversion systems including temporary cofferdams.

h. Schedule for removal of diversion elements.

i. Describe the proposed method for controlling and removing water, including groundwater, which enters the site and excavations.

2. Flood Contingency Plan for prevention or control of potential flooding of the Work area during storm events. The Flood Contingency Plan should address, but not be limited to maximum River level under which the temporary cofferdams may be used, emergency signaling procedures, health and safety plan, emergency breaching and controlled flooding procedures, leakage/seepage/sand boil control measures, and placement of temporary “Super Sack” and sandbag barrier for emergency situations.

B. Administrative

1. Submit qualifications for CONTRACTOR’s diversion system supervisor.

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PART 2 PRODUCTS

2.01 TEMPORARY COFFERDAMS

A. The temporary cofferdams can be an engineered berm constructed with Embankment Fill.

Refer to Section 31 23 23 – Fill and Backfill for Embankment Fill material specifications.

B. If the Embankment Fill berm method is selected, include slope protection of the cofferdam fill on the side of the cofferdam that will be subject to headwater or tailwater loading and flow.

2.02 DIVERSION PIPING AND APPURTENANCES

A. Diversion pipe shall be high-density polyethylene (HDPE), welded steel, ductile iron, or cast-iron at CONTRACTOR’s option, unless specified on the drawings. Corrugated metal pipe (new or existing) shall not be allowed.

2.03 PUMPS, HOSES, SIPHONS

A. Pumps, hoses, or siphons used at the site shall be sized appropriately and shall be maintained in good working order by CONTRACTOR.

B. Pumps shall be sized appropriately by CONTRACTOR and shall operate in a manner which does not create a nuisance to abutters (i.e., quietly and without significant exhaust).

C. Secondary containment shall be provided as stipulated in permits for gasoline or diesel-powered pumping equipment. Fueling procedures shall be as per permit conditions.

D. All piping, conveyance, equipment and materials necessary for the operation and maintenance of flow management system(s) shall be selected and provided by CONTRACTOR to complete the Work. All proposed equipment and materials shall be provided in the Water Management Plan as described above.

PART 3 EXECUTION

3.01 GENERAL

A. Maintain a safe, clean and accessible Work site at all times. CONTRACTOR shall have full responsibility for the complete and proper diversion of water from the Work site at all stages of the Project. CONTRACTOR shall, at no additional cost to the AGENCY, repair any damage to any equipment, material or Work caused by seepage, flood, overtopping, or other failure of the temporary cofferdam system.

B. CONTRACTOR shall take all reasonable and prudent precautions during each stage of construction to provide and maintain the Water Diversion System.

C. Work shall be protected from flooding caused by inflows into the reservoir drainage basin during all phases of construction. The Water Diversion Systems shall each be designed for

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the hydraulic loading of a 25-year storm event or greater. Refer to the table below for the flood frequency information assuming the reservoir is empty.

Return Period Peak Inflow

(cfs) Elevation

(feet) Inflow Volume

(acre-feet) 10-year 860 2977.89 485

25-year 2,310 2983.10 1,479

50-year 3,350 2987.87 2,889

100-year 4,420 2993.90 5,491

D. In the event storms and/or flooding are anticipated, remove construction equipment and materials from areas vulnerable to damage from flooding and otherwise take precautions to secure and protect the Work area against damage during passage of the flood. Items or materials that could adversely impact water quality from areas liable to be inundated or otherwise impacted by flooding shall be removed or protected. Secure the site and make all efforts to protect completed and incomplete Work. CONTRACTOR shall be solely responsible for protection of and repairs to equipment and materials impacted.

E. Any damage to the foundations, structures, or any other part of the Work caused by floodwaters due to failure of any part of the diversion or protective works will be considered within the control of CONTRACTOR and shall be repaired by CONTRACTOR.

CONTRACTOR will not be entitled to changes in Contract amounts or schedule as a result of failure of any part of the diversion or protective works.

F. Install and construct Water Diversion Systems according to the approved Diversion and Care of Water Plan.

G. Unused temporary piping shall be removed from the site and is the property of

CONTRACTOR.

H. Permanent diversion piping shall be buried or otherwise restrained to resist flotation and prevent damage.

3.02 SEQUENCING

A. Construction Phase 1

1. Reservoir and flood flow during Construction Phases 1 and 2 shall be diverted through the existing outlet works and Phase 1 and 2 temporary diversion piping. The flows shall outlet in the creek channel downstream of the Work areas and temporary downstream cofferdam.

2. Install the diversion piping and the connection to the existing outlet works conduit.

3. Construct a temporary downstream cofferdam.

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B. Construction Phase 2

1. Continue to divert flows through the existing outlet works and Phase 1 and 2 temporary diversion piping during construction of the service spillway, new outlet works, intake structure, and permanent diversion piping.

C. Construction Phase 3

1. Reservoir and flood flow during Construction Phase 3 shall be routed around the upstream cofferdam, diverted through the new outlet works and Phase 3 temporary diversion piping, and outlet in the creek channel downstream of the temporary downstream cofferdam during construction of the embankments.

2. Install Phase 3 temporary diversion piping from the new outlet works at the spillway to downstream of the temporary downstream cofferdam.

3. Demolish the existing outlet works after the new outlet works is constructed and operational.

4. Remove the Phase 1 and 2 temporary diversion piping once the outlet works and Phase 3 temporary diversion piping are constructed and operational.

D. Construction Phase 4

1. Install a blind flange on the permanent diversion pipe at the inlet tower to block water flow through the piping.

2. Remove the downstream cofferdam and Phase 3 temporary diversion piping.

3. Remove or abandon the upstream cofferdam.

E. Construction Phase 5

1. Continue use of the new outlet works to route reservoir and flood flows during Construction Phase 5.

3.03 TEMPORARY DIVERSION PIPING

A. Install diversion piping, inlets and outlets at the approximate alignment and grades shown on the Drawings. The actual alignment of the pipe shall be determined by CONTRACTOR to facilitate construction of the new structures. Pipe to be restrained or weighted with a minimum of 670 pounds per lineal foot.

B. Any control valves shall be open under normal operation to pass normal stream flows so that reservoir level will remain near empty during construction. Control valves can be closed temporarily for as short a duration as possible to allow CONTRACTOR to disconnect the diversion pipe or to switch diversion to the new outlet works in between construction stages.

Operation of control valves is CONTRACTOR’s responsibility.

C. Diversion pipe discharge shall be routed downstream of the mass excavation, as shown on the Drawings. Do not allow discharge into the excavation and Work areas.

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3.04 TEMPORARY COFFERDAMS

A. Design, construct, operate, and maintain temporary cofferdams and associated protective works necessary for diversion and care of the reservoir, the downstream creek, and wetlands.

B. Design Requirements:

1. The cofferdams shall be designed by a Professional Engineer and sized for the hydraulic loading of a minimum 25-year storm event.

2. Geotechnical data is available in the Geotechnical Data Report by GEI Consultants, dated December 2021, and the Project Design Report, which are available upon request.

3. The temporary downstream cofferdam shall fully prevent water under normal tailwater conditions from entering the Work side of the cofferdam but will not fully encompass the Work area.

4. If the embankment fill option is chosen, the cofferdam shall meet the required factors of safety in USBR Design Standards 13: Embankment Dams, Chapter 4: Static Stability Analysis. If another method is chosen, the CONTRACTOR shall design for adequate factors of safety in accordance with general industry guidance.

5. If the cofferdam designs do not consider ice loading on the cofferdam, CONTRACTOR shall prevent debris and ice from impacting the sides of the cofferdam.

6. Evaluate the site conditions, particularly the reservoir bottom and contours along the length of the cofferdams. Other temporary cofferdam structures (working platform) may be presented by CONTRACTOR for review and approval of the COR and BIA Representative.

C. Construct temporary cofferdams per the following requirements:

1. Strip muck within Work area for the cofferdam.

2. Refer to Section 31 23 23 – Fill and Backfill for Embankment Fill placement and compaction specifications. Compact the cofferdam fill with two coverages of an approved heavy equipment. There are no minimum density and in-place moisture requirements.

3. Maintain cofferdam to the design grades as designed by CONTRACTOR during the course of construction. Repair any damages caused by erosion or CONTRACTOR activities.

4. Provide additional protection, as needed to prevent damage to Work areas and permanent Work, as deemed necessary by CONTRACTOR.

D. The temporary cofferdams shall be maintained and supervised by CONTRACTOR’s qualified personnel.

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E. The temporary cofferdams shall remain in-service until Construction Phase 4 is complete.

Written approval from the BIA Representative and COR shall be required prior to CONTRACTOR decommissioning and removal of the temporary cofferdams.

F. Excess cofferdam fill not used as Embankment Fill shall be disposed in the on-site disposal area approved by the COR or removed from site.

G. The impacted area from cofferdam removal shall be reshaped to match the surrounding landscape so as not to interfere in any way with the operation or usefulness of the reservoir, creek, or adjacent wetlands.

3.05 INITIAL TESTING AND OPERATION

A. Any defective parts or equipment shall be replaced, and system leaks inspected and documented by CONTRACTOR prior to operation of the system(s).

B. Perform system startup, monitoring and operation, as appropriate, to ensure the effectiveness of the system(s) throughout its use.

3.06 LOCAL WATER CONTROL

A. Refer to Section 31 23 19 – Dewatering.

B. Maintain excavations and site Work areas free of puddling water and running water. Provide local dewatering, water barriers and erosion protection as required to protect the Work.

3.07 EMERGENCY CONDITIONS

A. Protect the Work in the event of an actual or potential emergency situation, including but not limited to an actual or potential failure of the temporary cofferdams and submit an emergency plan for approval as a part of the Flood Contingency Plan.

B. Maintain the required materials onsite to construct the approved emergency measures throughout the entire phase that the temporary cofferdams are in place. This Work shall be considered incidental to the temporary water control Work item and will not be paid for as part of the temporary cofferdam

END OF SECTION

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