ELMO_Scope_of_Work.pdf

El Morro National Monument

123 E. Roosevelt Ave

Grants, NM 87020

SCOPE OF WORK

Project: 248504 – Conduct Cyclic Maintenance on Water Tank and Deficiencies outlined in PMIS 337131

Install Fall protection on Water Tank System

Description:

The water tank at El Morro National Monument is a 58,000-gallon bolted metal structure set on a concrete foundation. It is 17 feet in diameter, and 24 feet high. Access into the tank is provided via a ladder and a 17” x 24” roof hatch. This project will bring in a diving contractor to inspect the tank and its features, photograph the tank and its features, and clean sediment from the bottom of the tank. Also, include repairing or replacing defective components or correcting any identified deficiencies.

Deliverables:

Once the work is concluded, the contractor will provide a detailed written report including relevant photographs and recommendations in print and as a digital copy for the park’s records. The report shall include a diagram of the water tank, showing the approximate locations of all of the tank features and any deficiencies noted during the inspection. The contractor shall also provide a copy of the high-resolution color video inspection to the park on a thumb/jump drive for the park’s records.

Inspection:

The inspection will include examining and photographing the following tank features:

• Exterior coatings, joints, seams

• Exterior ladders, rails

• Exterior hatch

• Roof and roof vents

• Interior coatings

• Interior walls and floors

• Interior ladder (if equipped)

• Inlet and outlet pipes

• Internal plumbing

• Joints and seams

• Overflow pipe

• Level gauge

• Sediment depth

The contractor will clean the accumulated sediment at the bottom of the tank using underwater vacuuming equipment.

Report:

The water tank inspection report shall contain the following information:

• Name of Tank

• Contractor’s Name & Contact Information

• Tank Capacity, Height, and Diameter

• Type of Foundation and Condition of Foundation

• Tank Style (i.e. ground tank, elevated tank)

• Type of Water Tank (i.e. welded steel, bolted steel, bolted glass-fused-to-steel, etc.)

• Date tank was constructed (if available)

• Type and condition of cathodic protection system (if equipped)

• Do the tank ladders and hatches meet current OSHA safety requirements?

• Was there any evidence of animals or insects entering the tank?

• Security: was the tank access hatch locked?

• Recommendations

Potable Water Operations:

Divers and associated in-tank equipment shall be fully disinfected in compliance with ANSI/AWWA standard C652-11. All gear and equipment entering the potable water tank shall be cleaned and disinfected and the dressed diver shall be sanitized with a 200 parts per million (ppm) concentration, NSF-60 approved sodium hypochlorite (“bleach”) solution immediately prior to entering the water tank.

For safety purposes, the inspector/diver shall utilize a helmet, dry suit, and shall be in direct voice communication with outside personnel at all times during diving operations. The contractor shall have full time live high resolution color video at all times during the inspection to allow for constant viewing and recording of the diver’s work and observations. All system entries will be conducted in accordance with applicable OSHA regulations pertaining to diving and confined spaces (OSHA 1910.401-1910.441).

Photograph of Water Tank:

Access Road to Water Tank:

The access road to the water tank is typically only passable via a 4 wheel drive vehicle.

Deficiency #1:

Deficiency #1 is to install a passive galvanic cathodic protection system.

The cathodic protection system shall consist of installing a passive cathodic protection system in the existing 58,000-gallon glass-fused-to-steel water tank. The passive cathodic protection system shall consist of 2 EA magnesium anodes placed on the bottom of the water tank. Each magnesium anode shall be 48 inches long by 2 inches square, 12 pounds in weight, and shall have a 3/8-inch diameter steel threaded rod core. Magnesium anodes shall be equal to a Model MA-12T as manufactured by M&M Industries, Inc. or as recommended by the tank manufacturer. The magnesium anodes shall be installed on opposite ends of the tank, approximately 180 degrees apart. The anodes shall be installed in accordance with the water tank manufacturer’s recommended details below:

Water Tank

Visitor Center

The recommended magnesium anode, or equal, is shown below:

Photograph of magnesium anode installed on the floor of another NPS water tank:

Deficiency#2:

Deficiency #2 includes the installation of fall protection hand railings from the top of the exterior ladder up to and around the tank vent. The hand railing shall be constructed of galvanized steel and shall be attached to the water tank using the existing bolts; no new tank penetrations shall be made to attach the hand railing system to the water tank. An example of the proposed hand railing system from another NPS location can be seen in the photograph below:

Deficiency #3:

Deficiency #3 includes digging out the area underneath the overflow pipe, installing a splash pad and rap, and installing 24-mesh stainless steel screen (at the flange where the flap valve is attached) and a flap valve on the end of the overflow pipe (see detail below).

Deficiency #4:

Clean the 24-mesh stainless steel screen on the vent.

Deficiency #5:

Install Park provided gasket on the roof hatch. The roof hatch gasket shall be Trim-Lok trim seal with top bulb – PVC plastic trim with EPDM rubber bulb seal that fits a 1/16” edge and has a 5/8” bulb seal diameter.

Deficiency #6:

Cut the 4” diameter PVC tank fill line down to ½ the height of the water tank to prevent it from freezing.

Reinstall the 90-degree bend on the tank fill line and point it away from the outlet pipe.

Deficiency #7:

Replace the badly corroded lower section of the 4” tank fill line with 4” Schedule 80 PVC pipe. Install non-corrosive (aluminum or stainless steel) bracing if needed; attach to existing bolts.