Statement of Work.pdf

Colorado River blw Davis Dam, AZ

Cableway Removal Statement of Work

Welhouse, Kanon B

U.S. Geological Survey

1/23/2020

Statement of Work Glossary:

Right bank - as observer is looking downstream

Left bank - as observer is looking downstream

Cableway - catenary spanning river used for streamflow discharge measurements

A-frame - steel H-beam structure to elevate and support a cable

Mass anchor - a large block of concrete used to hold a cable in place under tension

A-frame footer - concrete footing used to support steel A-frame towers

Messenger cable - wire rope used as support for aircraft warning markers or other special purposes

Main cable - in the context of a USGS streamgaging cableway, refers to the system’s main support wire rope for cable-car operation

Backstay - a wire rope guy used to support an A-frame, or other support structure, leading from the top of the support to an anchorage

Project Location: Lat 35°11'3.52", long 114°34'11.34" referenced WGS 84, 0.8 miles downstream of Davis Dam, 0.84 miles upstream of Laughlin Hwy 163 Colorado River bridge.

Introduction: Up for contract is the demolition and removal of a U.S. Geological Survey (USGS) streamflow gaging cableway. The cableway spans the Colorado River at approximately 820 ft bank to bank.

Special safety considerations must be made in the removal process to protect life and property, as the cableway is in direct proximity to recreation areas on both banks of the river as well as the river itself.

The USGS is the primary contact for the project but other governmental agencies have a stake in the removal of the cableway including the U.S. Bureau of Reclamation (USBR), Mohave County Davis Camp park, and the Colorado River Heritage Greenway Park.

Purpose: During a routine annual cableway safety inspection in 2014, the cableway at USGS streamflow gaging station 09423000, Colorado River below Davis Dam, was condemned. Many structural components have reached the end of their service life as the result of corrosion.

Currently, the cableway poses an unnecessary risk to the public and the aircraft warning markers are not serviceable from the main cable.

In accordance with Water Mission Area Memorandum NO.13.03, the actual necessity of the cableway was reviewed, and the outcome of the review was to dismantle the cableway.

This statement of work (SOW) describes the requirements for contractor support to the USGS for the removal of the cableway. The main objective of the project is to remove the main cable, messenger cable, cable support towers, concrete footings, and fence enclosures.

Scope of Work:

Situated on each bank of the river are fenced enclosures containing cable attachment points and support structures. The right bank enclosure is located in the Colorado River Heritage Greenway Park and the left bank enclosure is located in Mohave County Davis Camp Park.

The components of the terminations at each bank include cable support towers and mass anchors. The cable supports are anchored to the concrete footing with anchor bolts. The cable supports include steel saddle blocks for support of the main cable, backstay cables to support the towers, and messenger cable support terminations. The cable support at the right bank includes a platform for access to the cablecar, situated on the main cable, used for ferrying personnel across the river.

All steel components are to be dismantled and removed from the site, while the cable support tower footers are to be demoed below the existing land surface and covered with topsoil. The mass anchors are to remain in place with topsoil added to fill immediate surroundings to existing land surface elevation.

Pre-Task Communication and Reporting:

The contractor will obtain any required permitting and authorizations and provide copies of any such documents to the project manager.

Coordination Requirements: All demolition tasks must be coordinated with the USGS, USBR, land holders, and businesses providing recreational services on the river including jet ski rentals, river boat tours, kayak rentals, etc.

Coordination with all agencies involved is crucial to the safe removal of the cableway. Public access is available to all areas of the cableway continually throughout the year. Coordination to isolate the areas under demolition must be scheduled and the dates of the isolation will be provided to the community in a public service announcement no less than one week in advance.

All correspondence with Federal and State agencies other than the USGS must be documented and saved, with copies supplied to the project manager. The documentation shall contain the following information: name of agency, name of person(s), date, and nature of conversation.

The contractor will update the project manager daily, at the end of the day, on the status of the project.

Task Descriptions

• Task 1 - Removal of messenger cable and aircraft warning markers

The messenger cable is located 3’ above the main cable and carries the load of three 24”-36” aircraft warning markers. The wire rope is ¼” IWRC weighing approximately 11- 12 lbs/100 ft. The wire rope spans the catenary of 820 ft and terminates at the top of each tower by direct connections using thimbles and cable clips to 3/8” eye bolts.

• Task 2 - Removal of cablecar

The aluminum cablecar is located at the right bank and is secured to the walkway platform with a padlock. The cablecar is to be delivered in its current condition to the project manager.

• Task 3 - Removal of main cable

The main cable is 1 ¼” structural strand weighing approximately 3.28 lbs/ft and spans the catenary of 820 ft. The cable terminations are closed bridge sockets which were used for cable tension adjustment. The structural strand lays in a steel saddle block on top of the cable support towers.

• Task 4 - Removal of platform and staircase on the right bank of river

The cablecar landing platform is located on the right bank of the river. The platform dimensions are approximately 6’ x 4’ and 4’ above land surface. The platform and handrails are constructed of various sizes of angle iron and flat strap with expanded metal decking. Access to the platform is provided by steel steps of similar construction.

• Task 5 - Removal of cable support towers

Both A-frames are fabricated from 6” H-beam with angle iron cross support and ¼” steel plates welded on the bottom legs as well as the top. The A-frame on the right bank is 6’ x 12’ and the A-frame on the left bank is 6.5’ x 14’. Both are attached to the concrete footer with two ¾” anchor bolts.

• Task 6 - Demolition of support tower footers

The concrete A-frame support tower footers on both banks shall be demolished 1’ below land surface and covered with topsoil. The footer on the right bank is 1.5’ wide x 6.5’ long and the footer on the left bank is 3’ wide x 8’ long. The depth of the footers is likely not greater than 4’. Each footer is approximately 1’ above land surface.

• Task 7 - Removal of fence enclosures

Each cable support tower is enclosed by a 6’ chain-link fence with three strands of razor wire on top. All components of the fence enclosures are to be removed including the concrete post supports. Each fence enclosure is approximately 20’ x 20’.

• Task 8 - Remediation of concrete mass anchors

The concrete mass anchors shall be handled as follows:

o The left bank mass anchor is at grade level and topsoil is to be added to the area in front of the anchor covering the 1 ½” steel anchor bar and bringing the area up to grade.

o The right bank anchor is to be covered with topsoil to existing grade. If any part of the concrete mass anchor is above the surrounding grade it shall be demolished 1’ below grade and covered with topsoil.

• Task 9 - Disposal of debris

The contractor is to properly dispose of all debris including steel, hardware, wire rope, concrete, aircraft warning markers, and chain-link.

Requirements:

• All equipment and work shall conform to the requirements of the Occupational Safety and Health Act.

• The successful bidder shall handle the work in a manner that will cause the least inconvenience and annoyance to the public and to the property owners.

Length of contract

The USGS requires the cableway to be removed within thirty (30) days from the first day of the project execution.

Closure: Once the project is completed, the contractor shall notify the project manager and schedule a final inspection to verify all tasks included in the contract have been completed.

mailto:kwelhou@usgs.gov

Colorado River blw Davis Dam Cableway Location of USGS streamgaging cableway is marked in Red.

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Messenger Cable

Ramada Main Cable

On right bank looking across to left bank.

Viewing messenger cable, main cable, and note recreation ramadas nr the edge of water.

Messenger Cable support

Cablecar Walkway

Right bank – Cable car, a-frame, walkway platform, fence enclosure.

Cable termination at the right bank showing the closed bridge socket, a-frame backstay cable, and the mass anchor.

Cable termination at the light bank showing the closed bridge socket, a-frame backstay cable, and the mass anchor.

Messenger cable support

Backstay Cable

Left bank a-frame assembly.

Concrete Footer

Left bank a-frame base and footer.

Concrete Footer

Right bank a-frame and fence enclosure

Park visitors

The picture is intended to display the type of environment this cableway is located in. The boat is associated with the Riverside Casino River Boat Tours and recreational visitors are present in county park.

Legend