Specifications include, but are not limited to: Concrete Thrust blocks shall be allowed to cure for 48 hours prior to activating the water main. ; In muck, peat, or similar weak soils, thrust loads shall be resisted by using joint restraining devices or by removal of the soil and replacement with a material of sufficient stability ; All Valves 12 inches and larger and pipe joints within their corresponding “L” lengths shall be restrained, b. All High Pressure Valves (working pressures greater than 110 psi) and pipe joints within their corresponding “L” lengths shall be restrained ; Insulation board shall be placed on a smooth and level cushion, minimum of 2 inches, of fine concrete aggregate (sand) and shall be covered with a minimum of 2 inches of the same material .