Amendment 0006 - Revised Spec Section 31 23 20.pdf

Morgan Francis Remediation, Raymark Superfund Site, Stratford, CT

SECTION TABLE OF CONTENTS

DIVISION 31 - EARTHWORK

SECTION 31 23 20

TEMPORARY RIVER DIVERSION

PART 1 GENERAL

1.1 SUMMARY

1.2 SUBMITTALS

PART 2 PRODUCTS

2.1 GENERAL

2.2 CREEK DIVERSION SYSTEM

2.3 ENERGY DISSIPATION STRUCTURES

PART 3 EXECUTION

3.1 CREEK DIVERSION

3.2 ENERGY DISSIPATION STRUCTURE

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SECTION 31 23 20 Page 1

SECTION 31 23 20

TEMPORARY RIVER DIVERSION

PART 1 GENERAL

1.1 SUMMARY

This specification addresses the need to divert creek water, which is not impacted by the site, around the Work.

Both the Upper Upper Ferry Creek (UUFC) and the Tanner Creek Tributary channels are relatively narrow and pumping around excavation is preferred.

It is assumed that the Contractor can excavate and restore within base flow conditions and not open more than what can be restored prior to any rain event.

The Contractor can propose alternative diversion techniques but will have to adhere to the protection requirements stated within this specification.

As part of the Work, the A/E modeled various flow events within Ferry Creek and Tanner Creek Tributary and the results are the following:

Tanner Creek Tributary

UUFC @ Box Culvert

Base Flow: 6 cfs

1-YR (2.8" rainfall depth within 24-hours event): 84 cfs 215 cfs

2-YR (3.4" rainfall depth within 24-hours event): 147 cfs 396 cfs

5-YR (4.2" rainfall depth within 24-hours event): 245 cfs 668 cfs

The Contractor shall protect the Work from damage for up to a 5-YR storm event and shall have a Contingency Plan for storms greater. If the Contractor elects to utilize a diversion technique with less protection thana 5-YR storm event, an additional contingency plan will need to be developed to protect against damage to Work for any storm equal to or less than the 5-YR storm event.

For the Upper Upper Ferry Creek, the Contractor shall construct an Energy Dissipation Structure in accordance with the design Drawings. The design for the Energy Dissipation Structure is limited to pipe discharge velocities of 15 feet per second (ft/s). The Contractor is responsible for selection of equipment and piping which does not exceed this discharge velocity.

1.2 SUBMITTALS

As part of the Contractor's Plan, Contractor shall provide a Creek Diversion Plan to describe the methods, equipment, and operation to divert creek flows and to collect, store, and discharge water from disturbed areas.

USACE approval is required for submittals with a "G" designation;

SECTION 31 23 20 Page 2 submittals not having a "G" designation are for information only. When used, a designation following the "G" designation identifies the office that will review the submittal for the USACE. Submit the following in accordance with Section 01 33 00 SUBMITTAL PROCEDURES:

SD-01 Preconstruction Submittals

Creek Diversion System ; G, RO

Contingency Plan ; G, RO

PART 2 PRODUCTS

2.1 GENERAL

The Contractor is responsible for selection of specific equipment to be used to implement creek diversion activities. All equipment must be detailed in the CP to be approved by the AE.

2.2 CREEK DIVERSION SYSTEM

The Contractor shall provide, install, and operate the Creek Diversion System.

The Creek Diversion System shall include diversion berms, pumping stations, diversion pumps and piping, instrumentation and controls, temporary diversion devices, auxiliary pumps, and an energy dissipation structure.

Diversion Berms - The Contractor shall provide all equipment and materials to install and maintain the Upstream Diversion Berm and Downstream Diversion Berm as shown on the Drawings and in accordance with the CP, including any temporary facilities needed to facilitate construction of all berms.

Pumping Stations - The Contractor shall install pumping stations as required with a stable base for the diversion pumps, containment areas, pump intake structures, if required, and electrical hookups, as necessary above the Upstream and Downstream Diversion Berms.

Diversion Pumps and Piping:

1. The Contractor shall provide, install, operate, and maintain diversion pumps and piping to divert creek flow from above the Upstream and Downstream Diversion Berms to the Energy Dissipation Structure.

2. Each pump shall be set in an enclosure to contain leaks of fuel, oils, or other substances. The enclosure shall be capable of containing total fuel capacity of pump. Enclosures and pumps shall be carefully placed so as to avoid damaging the enclosure. Enclosures shall be monitored and maintained for duration of Project.

3. The average 'dry weather' flow is expected to be 5-15 cubic feet per second (cfs).

4. Diversion pumps and piping shall have a combined capacity of 50 cfs.

SECTION 31 23 20 Page 3

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Text Box Pumps and associated equipment shall be in critically silenced enclosures to mitigate noise for nearby residents.

5. The upstream Creek Diversion System Station shall include at least one standby pump to be used when system pumps require repair or maintenance. For example: two pumps each capable of 50 cfs; or three pumps each capable of 16.7 cfs are acceptable arrangements for creek diversion pumping.

6. The Contractor shall provide pumps necessary to collect water upstream of the Downstream Diversion Berm (rate 400 gpm with backup).

Discharge from this pump shall be piped into diversion piping as shown in the Drawings. This station shall also include a standby pump.

7. The Contractor shall excavate any sumps as necessary in the creek to facilitate pumping creek water.

Instrumentation and Controls:

1. The Contractor shall provide instrumentation and controls as required to operate the Creek Diversion System as specified in this Section. Pump failure must provide an audible alarm and must provide an autodial alarm unless 24 hour supervision is provided.

Temporary Diversion Devices:

1. The Contractor shall provide sand bags or other effective temporary diversion devices required to divert clean creek water which flows under or around the Upstream Diversion Berm away from excavation areas and to locations where auxiliary pumps are installed.

2. The Contractor shall provide sufficient temporary diversion devices to place 1-foot-high temporary berms across the creek 50 feet downstream from the Upstream Diversion Berm and a similar berm upstream of the Downstream Diversion Berm.

Auxiliary Pumps and Piping or Hoses:

1. The Contractor shall provide, install, maintain, and operate auxiliary pumps and piping or hoses to pump clean creek water which flows under or around the Upstream and Downstream Diversion Berms back to the creek, either upstream or downstream of the berms.

2. The Contractor shall ensure that clean water does not come into contact with Impacted Materials.

2.3 ENERGY DISSIPATION STRUCTURES

The Contractor shall provide materials necessary for the Energy Dissipation Structure from pump outlet pipes as shown on the Drawings.

PART 3 EXECUTION

3.1 CREEK DIVERSION

Creek Diversion - Mobilization and Set-up - The Contractor shall furnish and install the components of the Creek Diversion System as described in this Section.

Creek Diversion - Operation:

1. The Contractor shall operate and maintain the Creek Diversion

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System at its design capacity during the period when creek diversion is required.

2. The system shall operate 24 hours per day except as approved by the USACE.

3. The Contractor shall operate the system effectively in order to provide a dry, or wet as approved by USACE, excavation area following procedures specified in the approved CP, submitted as specified in Specifications Section 01 33 00 SUBMITTAL PROCEDURES.

4. The Contractor shall make reasonable efforts, in consultation with the USACE, to modify operation procedures based on field conditions, if necessary to meet performance requirements of the system.

5. The Contractor shall use auxiliary pumps and temporary diversion devices to pump water that flows under or around the Upstream and Downstream Diversion Berms back to the creek upstream of the berm.

6. During periods of potential heavy precipitation or flooding, the Contractor shall implement the provisions of the Contingency Plan included as part of the CP submitted as specified in Specifications Section 01 33 00 SUBMITTAL PROCEDURES.

3.2 ENERGY DISSIPATION STRUCTURE

The energy dissipation structure is to be installed in accordance with the Drawings.

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