N.J. Admin. Code § 7:9A-5.10

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

Section 7:9A-5.10 - Disturbed ground

(a) When placement of a disposal field is proposed in an area of disturbed ground, the type and depth of soil limiting zones as well as a variety of additional factors must be considered in determination of soil suitability, depending on the nature of the soil disturbance, as outlined in (b) below. Types of soil disturbance which shall be addressed within the soil evaluation and engineering design include but are not limited to filled areas, excavated areas, re-graded areas, artificially drained areas and pre-existing wastewater disposal areas.

(b) A site shall be considered disturbed ground when any of the following conditions are present:

1. Displaced or man-made objects such as tree stumps, branches, plant stems, leaves, building debris or trash of man-made origin, are observed below the ground surface in profile pits or soil borings;

2. Soil profile pits or borings reveal A-horizons or O-horizons which are buried by layers of soil or other material;

3. Soil horizons are absent or mixed in a manner which cannot be explained as a result of natural processes;

4. Mounded areas or depressions in the land surface are observed which do not conform with surrounding topography and which show signs of recent disturbance such as lack of vegetation, weedy vegetation, severe erosion, wheel ruts, etc.;

5. Remnants of building foundations, pavement or other man-made structures are observed at the surface or uncovered in profile pits or soil borings;

6. Subsurface drains or their remnants are observed in profile pits or borings or the outlets of drains are observed at the surface; or

7. Components of an existing wastewater disposal system, or remnants of an abandoned sewage disposal system are present below the site of a proposed new system.

(c) When evidence is found that the surface of the ground may have been modified by a disturbance such as addition of fill material, removal of soil horizons or regrading, the existing ground surface shall be identified based upon the following criteria:

1. When a buried A- or O-horizon is present, the existing ground surface shall be taken as the top of the A-horizon or the bottom of the O-horizon.

2. When a buried A- or O-horizon is not present, the level of the existing ground surface shall be determined by extrapolation from adjacent areas beyond the limit of soil disturbance. When this method is relied upon, the nature of the pre-existing topography as well as the nature of the ground disturbance shall be described, using topographic contour maps and profiles where appropriate, to the satisfaction of the administrative authority.

(d) In cases where disturbed soil or other fill material are present at the site, the suitability of this material shall be evaluated based upon its composition and its physical stability as follows:

1. Fill materials containing more than trace amounts of the following types of materials, or any other materials which are subject to disintegration or change in volume, shall be considered unsuitable:

i. Tree stumps, plant stems, leaves, food or animal remains or wastes, wood chips, saw dust, or any organic materials which may be subject to decay;

ii. Trash, discarded furniture, building or demolition debris or any bulky objects containing large voids or subject to collapse or re-orientation; or

iii. Cans, bottles, drums or any containers which are empty or filled with liquids.

2. Layers of fill material which do not contain materials as described in (d)1 above but which do contain course fragments in excess of 50 percent by volume shall be considered excessively coarse horizons or substrata. In the case of disturbed ground, coarse fragments may include man-made or artificial materials as well as rock fragments which are larger than two millimeters in diameter, provided that the man-made materials are limited only to physically and chemically inert materials without large voids, such as brick, concrete or glass fragments.

3. When construction of a wastewater disposal field is proposed within disturbed ground, an acceptable state of compaction of the soil or fill material shall be verified by laboratory tests of samples taken from within the area of the proposed disposal field. Based upon the results of these tests, the design engineer shall certify to the administrative authority that the in-place dry density of the soil or fill material above which the proposed system will be located is a minimum of 90 percent of the Standard Procter Density determined by laboratory analysis.

4. When a disposal field is to be constructed on sloping ground which has been regraded, the design engineer shall certify to the administrative authority that the regraded area within and surrounding the individual subsurface sewage disposal system is stable and can structurally support the individual subsurface sewage disposal system.

(e) In cases where the surface of the ground has been raised by the addition of fill material or lowered by the removal of pre-existing soil horizons, soil suitability shall be determined based upon the depth to limiting zones measured from the existing ground surface determined as prescribed in (c) above, or the ground surface, whichever is lowest.

(f) Ground containing subsurface drainage systems or remnants of abandoned subsurface drainage systems shall be considered unsuitable for the installation of a disposal field unless the drains will be removed or the outlets of the drainage system permanently sealed. Any subsurface drain which has a surface outlet shall be considered as a watercourse and is subject to minimum horizontal setback distances from waste disposal system components as set forth in 7:9A-4.3.

(g) Ground containing existing wastewater disposal systems or remnants of abandoned systems shall be considered unsuitable for the installation of a disposal field unless the pre-existing system will be removed prior to installation of the proposed new system.

N.J. Admin. Code § 7:9A-5.10

Amended by R.1999 d.314, effective 9/20/1999.
See: 31 N.J.R. 1416(a), 31 N.J.R. 2741(a).
Inserted (d)4.
Amended by R.2012 d.066, effective 4/2/2012.
See: 43 N.J.R. 478(a), 44 N.J.R. 1047(a).
In the introductory paragraph of (c) and in (c)1, (c)2, and (e), substituted "existing" for "pre-existing natural"; and in (e), deleted "existing" preceding "ground".