25.0403.1 Minimum Design Criteria.

Cite as [A.S.A.C. § 25.0403.1]

(1) A public water system shall be designed using good engineering practices. A public water system which is designed in a manner consistent with the criteria contained in the Ten State Standards or other industry-accepted standards shall be considered to be designed using good engineering practices.

(2) A potable water distribution system shall be designed to maintain and shall maintain a pressure of at least 20 pounds per square inch at ground level at all points in the distribution system under all conditions of flow.

(3) Water and sewer mains shall be separated in order to protect public water systems from possible contamination. All distances are measured perpendicularly from the outside of the sewer main to the outside of the water main. Separation requirements are as follows:

(a) A water main shall not be placed:

1. Within 6 feet, horizontal distance, and less than 2 feet, vertical distance, above the top of a sewer main unless extra protection is provided. Extra protection shall consist of constructing the sewer main with mechanical joint ductile iron pipe or with slip-joint ductile iron pipe if joint restraint is provided. Alternate extra protection shall consist of encasing both the water and sewer mains in at least 6 inches of concrete for at least 10 feet beyond the area specified by this subsection (3)(a)1.

2. Beneath a sewer line.

(b) No water pipe shall pass through or come into contact with any part of a sewer manhole. The minimum horizontal separation between water mains and manholes shall be 6 feet, measured from the center of the manhole.

(c) The separation between force mains or pressure sewers and water mains shall be not less than 2 feet vertically and not less than 6 feet horizontally under all conditions. Where a sewer force main crosses less than 6 feet below a water line, the sewer and water mains shall be encased in at least 6 inches of concrete or constructed using mechanical joint ductile iron pipe for not less than 10 feet on either side of the water main. No sewer force main shall cross above a water main.

(d) Sewer mains (gravity, pressure, and force) shall be kept a minimum of 50 feet from wells unless the following conditions are met:

1. Water main pipe, pressure tested in place to 50 psi without excessive leakage, is used for gravity sewers at distances greater than 20 feet but less than 50 feet from any well; or

2. Water main pipe, pressure tested in place to 150 psi without excessive leakage, is used for pressure sewers and force mains at distances greater than 20 feet but less than 50 feet from any well. “Excessive leakage” means any amount of leakage which is greater than that permitted under the AWWA Installation Standard applicable to the particular pipe material, joint, or valve type.

3. Under no condition shall a sewer conveyance, including lines, manholes and lift stations, be constructed within 20 feet of any well.

(4) A public water system shall not construct or add to its system a well which is located:

(a) Within 50 feet of existing sewers unless the sewer main has been constructed in accordance with subsection (3)(d)1 or 2 of this Section;

(b) Within 100 feet of any existing septic tank or subsurface disposal system;

(c) Within 100 feet of a discharge or activity that is a potential source of contamination; or

(d) Within 100 feet of an underground storage tank containing petroleum products or other potential contaminant.

History: Rule 1-08, eff 1 Jun 08.