Ala. Admin. Code r. 420-3-1-.58

Current through Register Vol. 43, No. 02, November 27, 2024

Section 420-3-1-.58 - Gravel Field Standard Construction Specifications

(1)General Requirements. Distribution piping shall be installed at the same elevation, unless an approved system provides for a design ensuring equal flow through each of the perforations and the effluent is uniformly applied to the soil infiltrative surface.

(a) The minimum acceptable material for non-perforated rigid pipe and fittings shall conform to the applicable section of the International Private Sewage Disposal Code excluding cellular core pipe. All pipe connections shall conform to the appropriate ASTM standard or manufacturer's requirement.

(b) The EDF may be supplied by a level header, serial distribution, or a distribution box. Other methods may be permitted provided that those methods are engineer certified.

(2)Level Header. The level header is used on relatively flat terrain where topography will allow EDF bottoms to be on the same elevation, within tolerance. The header shall be joined to the effluent line by a vent tee laid horizontally and at the same elevation as the EDF pipe. A sanitary tee shall not be used for this connection.

(a) The invert of the header shall be a minimum of 4 inches below the invert of the septic tank outlet.

(b) The minimum diameter of the effluent line shall be 4 inches unless otherwise specified by an engineer and shall continue to the header line.

(c) A non-perforated header line shall not be counted as part of the required EDF.

(3)Serial Distribution. When a level header system cannot be installed, a system of serial distribution following land contours may be used.

(a) Effluent shall enter the uppermost EDF pipe through a watertight effluent line discharging into the trench through a vent tee laid horizontally. A sanitary tee shall not be used for this connection.

(b) EDF pipes shall be connected by means of a non-perforated line and constructed so that each trench is filled with effluent to the full design depth before effluent flows through the crossover line to the next lower EDF pipe. Distribution of effluent to EDF trenches shall be designed to ensure that lines are equally dosed when receiving effluent from preceding trenches.

(c) The invert of the uppermost EDF pipe shall be a minimum of 8 inches lower than the invert of the septic tank outlet. The invert of a crossover line shall be a minim.um of 4 inches lower than the invert of the septic tank outlet. The inverts of all crossovers from an EDF trench shall be set at equal elevation.

(d) At the point where a crossover line leaves an EDF pipe in a Conventional O8S1 the trench for the crossover line shall be dug no deeper than the top of the aggregate or top of the EDF product in the preceding trench so that an undisturbed block of earth will remain in place for the full depth of the aggregate or EDF product. Crossover lines shall be laid on undisturbed earth. Crossovers for an ADPH permitted equivalent EDF pipe shall be constructed within the requirements of the product manufacturer.

(e) The maximum length of a serial EDF pipe is 100 feet in each direction when measured from crossover.

1. For EDF pipes less than or equal to 100 feet1 one crossover is required.

2. When EDF pipes exceed 100 feet in length, at least two crossovers are required.

3. Crossovers on successive lines shall be distributed in the system to minimize short-circuiting of effluent.

(f) If serial distribution is utilized in a Controlled Fill System, Schedule 40 PVC crossovers shall be used in standard trenches with compatible 4-inch EDF pipe or an ADPH permitted equivalent. Cellular core pipe is not acceptable.

(4)Distribution Box. A distribution box may be used as follows:

(a) In lieu of a header line, to connect the effluent line to EDF pipes on the same elevation.

(b) In lieu of serial distribution1 to connect EDF pipes on different elevations.

(c) To evenly distribute effluent to separate EDFsections of an OSS

(d) The distribution boxshall be set on level grade. Watertight, non-perforated, rigid, 4-inch, Schedule 40 PVC, or equivalent pipe (see paragraph (1)(a) of this rule) shall extend from the distribution box to the EDF. The first 5 feet of this pipe shall be on level grade.

(5)EDF Trench Construction Requirements. The EDF trenches shall comply with the following requirements:

(a) The width of the trench shall not be less than 18inches nor more than 36 inches. See 420-3-1-.59 Pad and Bed Construction Specifications for alternative widths.

(b) The minimum distance between EDF sidewalls shall be 5 feet measured horizontally. Where trenches are on slopes with a grade greater than 25 percent, the minimum. distance between trenches shall comply with requirements set forth in Table 8.

(c) All trench bottom elevations in any 100-foot run of trench shall be within plus or minus 1 inch of all other elevations in that run.

(d) The minimum gravel field standard EDFtrench depth shall be 12 inches.

(e) The maximum EDF trench depth shall be 60 inches. Trench depth shall comply with the MVS in 420-3-1-.42 Soil Restriction Depth and Vertical Separation.

(f) There shall be a minimum cover of 12 inches over the EDF.

(g) The maximum length of an EDF trench in an EDF shall be 100 feet, except as provided in the serial distribution systems section of this rule.

(6)EDF Pipe Requirements. The EDF pipe in an EDF using aggregate shall comply with the following requirements:

(a) Appropriate pipe and fittings that conform to applicable ASTM standards shall be used.

(b) All pipe elevations in any 100-foot run of trench shall be within plus or minus 1 inch of all other pipe elevations in that run.

(c) The inside diameter of EDF pipe shall be a minimum of 4 inches.

(d) EDF pipe shall be rigid or semi-rigid perforated plastic pipe with a minimum exfiltration area of 2.2 square inches per foot of pipe. The exfiltration area shall consist of openings located uniformly on one-half the circumference of the pipe. The openings shall be of such size, shape, and uniformity as to preclude sealing by solids or entrance of gravel or other approved substance surrounding the pipe. Pipe with slits, such as agricultural drainpipe, are not approved for use as EDF pipe.

(e) Perforated pipe in the EDF trenches shall be installed with the perforations turned down.

(f) The EDF pipe shall be installed in ADPH approved aggregate.

(g) The trench bottom of an EDF line shall be placed entirely in the native soil or in the fill, if required, but not in both. If the EDF line is in a Controlled Fill System, the depth of the line shall comply with 420-3-1-.61(9)(a) Controlled Fill Mound System.

(7)Aggregate and Cover Material. Aggregate and cover material shall comply with the following requirements:

(a) When the aggregate is coarse gravel or stone, it shall be washed and clean, free from fines, dust, sand, or clay, and ranging in size from one-fourth to 2.5 inches. The gravel or stone shall extend at least 8 inches below the lowest point of the EDF pipe and at least level with the topof the EDF pipe. ADPH may consider other aggregate under a Product Permit.

(b) The aggregate surrounding the EDF pipe shall be gravel as specified by these rules or approved for such use by the product manufacturer and shall be covered with untreated building paper, heavy Kraft paper, or geotechnical fabric and then back-filled with at least 12 inches of earth cover.

(c) Material which is impervious to air and water, such as plastic sheeting, polyethylene, or similar materials, shall not be used as a cover material over the aggregate in the EDF trench.

Ala. Admin. Code r. 420-3-1-.58

New Rule: Filed October 20, 2005; effective November 24, 2005; operative March 19, 2006.

Adopted by Alabama Administrative Monthly Volume XXXV, Issue No. 04, January 31, 2017, eff. 3/5/2017.

Adopted by Alabama Administrative Monthly Volume XLI, Issue No. 03, December 30, 2022, eff. 2/13/2023.

Previous Rule .83 was renumbered .58 per certification published December 30, 2022; effective February 13, 2023.

Authors: Thad Pittman, Matthew Conner. Ken Stephens, Bob Bright

Statutory Authority:Code of Ala. 1975, §§ 22-2-2(4); 22-2-2(6); 22-10-1, et seq.; 22-26-1et seq.