N.J. Admin. Code § 7:9A-10.5

Current through Register Vol. 56, No. 21, November 4, 2024

Section 7:9A-10.5 - Specific requirements for mounded disposal field installations

(a) A mounded disposal field installation shall be made by installing the disposal field as prescribed below, within suitable fill which has been placed above the existing ground surface.

(b) Requirements and restrictions relating to site regrading shall be the same as those prescribed for conventional installations in 7:9A-10.3(b).

(c) On sloping sites, the disposal field shall be elongated in shape with the long axis parallel to the topographic contour.

(d) Prior to placement of fill material, the ground surface shall be prepared as follows:

1. Excessive vegetation shall be cut and removed. Large trees including the stumps shall be removed. If large holes are left as a result of stump removal these shall be filled with fill material meeting the requirements of 7:9A-10.1(f)4.

2. The delivery pipe from the dosing tank shall be installed and the excavation backfilled and compacted prior to preparation of the ground surface for fill placement.

3. The area within the perimeter of the mound shall be plowed or disked to produce a thoroughly roughened surface. Plowing shall be done using a two bottom or larger moldboard plow or chisel plow and shall be parallel to the topographic contour in such a direction that each plow furrow will be thrown upslope. The soil should be broken-up to a depth of six to eight inches. Alternatively, a roto-tiller may be used provided that the surface soil is of sand or loamy sand texture.

(e) A mound shall be constructed by placing a layer of fill material over the ground within and adjacent to the area of the disposal field. The method of emplacement and lateral extent of the fill material shall be as follows:

1. The area of the fill layer shall include the area of the disposal field plus a lateral extension of fill material surrounding the disposal field on all sides.

2. The minimum required width of the lateral fill extension shall be 20 feet where gravity distribution is to be used and five feet where pressure distribution is to be used.

3. Within the area of the lateral fill extension, the top surface of the fill material shall be kept level with or higher than the invert of the distribution laterals.

4. On sloping sites, the width of the lateral fill extension may be reduced on the upslope side of the disposal field provided that the top surface of the fill material is kept level with or higher than the invert of the distribution laterals up until the point where the top surface of the fill material intersects with the existing slope.

5. At the outside edge of the lateral fill extension, the mound shall be terminated by sloping the top surface of the fill layer downward, or by providing a berm of soil material meeting the requirements of 7:9A-10.3(f)2 and 3, at a slope of three to one or less. Alternatively, lateral support for the fill layer may be provided by a retaining wall meeting the following requirements:

i. The retaining wall shall be designed and constructed in a manner that:

(1) Prevents lateral movement or seepage of water through the retaining wall;

(2) Ensures wall stability by including an adequate footing that accounts for the hydraulic forces of effluent and stormwater on the retaining wall and footing; and

(3) Withstands hydrostatic pressure without the use of subsurface drainage mechanisms;

ii. The elevation of the top of the retaining wall shall be no lower than the elevation of the top of the filter material in the disposal area;

iii. The distance from any retaining wall to any property line must be at least the total height of the retaining wall;

iv. The retaining wall shall be designed by a New Jersey licensed professional engineer who shall certify, in accordance with N.J.A.C. 13:40-7 of the State Board of Professional Engineers and Land Surveyors rules, that the requirements of (e)5i through iii above are met by the proposed design;

v. Construction of the retaining wall shall be supervised by the New Jersey licensed professional engineer; and

vi. The administrative authority shall not issue a certificate of compliance until an as-built plan has been prepared and certified by the New Jersey licensed professional engineer confirming that the retaining wall has been constructed in accordance with the approved design plan.

6. Fill material below the disposal field and within the area of the lateral fill extensions shall be suitable fill material meeting the requirements of 7:9A-10.1(f)4.

7. Compaction of fill shall be carried out as prescribed in 7:9A-10.4(f).

(f) Construction and installation of the disposal field and distribution network shall be as prescribed for conventional installations in 7:9A-10.3(d).

(g) Filter material shall be as prescribed for conventional installations in 7:9A-10.3(e).

(h) Backfill and final grading over the mound shall be completed as follows:

1. Immediately above the disposal field filter material which has been covered with a suitable barrier material, as prescribed in 7:9A-10.3(e)3, a layer of topsoil, suitable for establishment of a good vegetative cover, 12 to 18 inches in thickness at the center of the mound and six to 12 inches in thickness at the edges, shall be placed over the entire mound, covering the top and side slopes. The topsoil shall be build up thicker along the long axis of the mound so that a convex profile is produced parallel to the direction of the slope. The topsoil shall be lightly compacted by tamping or rolling to prevent settlement.

2. Immediately after completion of final grading, the mound surface shall be mulched and seeded, or sodded, to establish a good vegetative cover and to prevent erosion.

N.J. Admin. Code § 7:9A-10.5

Amended by R.2012 d.066, effective 4/2/2012.
See: 43 N.J.R. 478(a), 44 N.J.R. 1047(a).
Rewrote the introductory paragraph of (e)5; and added (e)5i through (e)5vi.