The cistern shall be designed to be trouble-free, and shall carry a transferable manufacturer’s or reseller’s warranty, for a life expectancy of at least 25 years, or such longer terms as may be available and commercially reasonable.
The cistern shall be rated for highway loading as required by AASHTO Standards.
All piping shall be International steel pipe or schedule 40 PVC in accordance with ASTM Standards. All external piping shall be treated with rust inhibitor and painted red.
All connections shall be clean, airtight and use appropriate sealing material according to the manufacturer’s specifications.
All connections shall be anchored to the cistern to resist movement. Steel piping shall be threaded together at all joints. Schedule 40 PVC piping shall be glued at all joints.
The cistern shall be designed and installed so it will not float when empty.
6.2Tanks, Hydrants and Vehicle Pad.
Cisterns shall be constructed of either single-wall fiberglass or precast concrete and designed (a) based on NFPA Standard #1231, Appendix B, Section B-4, and (b) specifically for the site and soil conditions where they will be installed.
The rated capacity of each cistern shall be at least 30,000 gallons unless the Fire Chief determines otherwise.
The Dry Hydrant shall have a minimum delivery capacity of 1,000 gallons per minute (GPM) for 75% of the cistern’s capacity.
The Dry Hydrant suction connection shall be located three feet beyond the backfill grade so as to use a single 10-foot length of suction hose to connect to the fire pump when the apparatus is parked on the Vehicle Pad. The suction connection shall be no more than 15 feet above the bottom of the cistern.
The size and configuration of each Vehicle Pad shall be designed in consultation with the Fire Chief before an application is submitted.
Vehicle Pads should be at least 14 feet wide and 40 feet in length and tapered to meet the roadway with the connection at the center of the pad length. Each Vehicle Pad shall meet both New Hampshire Department of Transportation and Town of Wilton road design and other applicable requirements, and the pitch of the Vehicle Pad and shoulder from the edge of the pavement to the suction connection shall be between one and six percent downgrade.
The Vehicle Pad shall be so located as to allow fire apparatus to connect to the Dry Hydrant without blocking a travel lane of the roadway.
6.3Suction Connections.
The suction connection shall be six-inch diameter steel, threaded female connection, with National Standard Thread and a suitable cap.
The suction piping system shall be six-inch diameter and capable of delivering 1,000 GPM for 75% of the cistern’s capacity.
Suction piping shall be supported on the top of the tank and the bottom, six inches above the floor of the tank. All horizontal suction piping shall slope slightly uphill toward the suction connection to effect draining back to the water source.
The suction pipe connection shall be between 24 and 30 inches above the level of the grade where the vehicle's wheels are located when the cistern is in use. The distance from the bottom of the suction pipe to the suction connection shall not exceed 14 vertical feet.
The suction pipe shall be supplied with an anti-vortex plate measuring a minimum of sixteen inches square (16” X 16”). The anti-vortex plate shall be attached to the bottom of the tank at least six inches off the floor.
6.4Filler Connection.
The filler pipe shall have a four-inch diameter.
The filler connection shall have one four-inch Storz connector with an acceptable cover attached to a 45-degree downward sweep elbow that shall be supported vertically by the cistern. The filler pipe connection shall be 36 inches above the final grade.
6.5Vent Pipe.
The vent pipe shall be six-inch diameter and shall terminate not less than 36 inches above the final grade, with the opening to the pipe facing downward.
Vent piping shall have screen covers to prevent access by wildlife or insects, etc.
6.6Backfilling.
The cistern shall be completely piped and inspected by the Fire Chief before backfilling begins.
All backfill shall be screened gravel with no stone larger than 1.50 inches and shall be compacted to 95% of ASTM Standard 1557.
Cistern bedding shall consist of a minimum of 12 inches of crushed stone from .75 inches to 1.50 inches in size, compacted over a permeable geotextile membrane that prevents the stone from merging with the underlying material. No fill shall be used under the stone.
There shall be either (a) at least four feet of fill over the cistern, or (b) vermin-resistant foam insulation applied to the top and upper 2 feet of the sides of the cistern and at least two feet of fill over the cistern In each case, backfill shall extend 10 feet beyond the edge of the cistern and have a maximum 3:1 slope, loamed and seeded with a perennial seed mixture.
After backfilling, the cistern and all exposed piping shall be protected from vehicular damage by guardrails, large boulders, or concrete-filled steel pipe bollards no less than eight inches in diameter, painted red, and set in the ground below the frost line. The protection closest to each side of the connection shall have a 4-foot opening to the connection being centered.
Cisterns shall be equipped with a 32-inch watertight manhole with a locking device as specified by the Fire Chief. Access shall be provided to all sections of the tank.
The Responsible Party or Parties shall supply and install identification signs as directed by the Fire Chief and acceptable to the Wilton Highway Department, including, without limitation, “No Parking” signs.
