N.J. Admin. Code § 7:9A-6.1 - General provisions for permeability testing

Current through Register Vol. 54, No. 7, April 4, 2022

(a) The design permeability is the basis for determining the minimum required area of the disposal field. Tests shall be required at the site of each proposed disposal field in native soil or rock material to demonstrate an adequate zone of disposal as required at 7:9A-10.1(e). Tests shall be required in those areas demonstrating an adequate zone of disposal for determination of the design permeability. Design permeability tests shall be conducted as follows:
1. Design permeability tests for conventional disposal fields shall be conducted at the level of infiltration at a depth one to three feet below the ground surface within the soil horizon where the bottom of the disposal field will be placed;
2. Design permeability for all mounded disposal fields or soil replacement disposal fields where native soil will remain above the identified zone of disposal shall be determined from the remaining least permeable native soil material above the identified zone of disposal;
3. Design permeability for all soil replacement disposal fields, including mounded soil replacement systems, using fill material that meets the requirements of 7:9A-10.1(f) from the top of the zone of treatment to the top of zone of disposal shall be between six and 20 inches per hour; and
4. The permeability of all fill material shall be confirmed after installation to be greater than six inches per hour at the level of infiltration. A percolation test shall be conducted within the fill material after it has been emplaced and compacted, or a tube permeameter test shall be conducted using samples of the fill material which have been compacted to a bulk density equivalent to that achieved in the construction of the disposal field. An additional test shall be required at the top of each separate type of fill, should the fill material in the zone of treatment differ from the fill material being used in the zone of disposal, to confirm each type of fill material has been installed with a permeability rate greater than six inches per hour.
(b) The administrative authority may require additional types of tests, or additional tests at additional locations or alternate depths other than the depth of infiltration, when doubt exists regarding the presence or the type of a limiting zone or the soil conditions present.
(c) The type of tests which may be used shall be determined based upon the purpose of the test and the soil conditions at the depth of the test as shown in Table 6.1 below.

Table 6.1 Type of Test
Test Options: 1--Tube Permeameter Test
2--Soil Permeability Class Rating Test
3--Percolation Test
4--Basin Flooding Test
5--Pit-bailing Test
6--Piezometer Test

Purpose of Test and Soil Conditions Acceptable Test Options
at Depth of Test
I. Determination of Design Permeability at Level of
Infiltration, Identification of Hydraulically
Restrictive or Excessively Coarse Horizons or
Substrata Above the Water Table
A. Sands and loamy sands with single grain 1, 2 or 3
structure
B. Other soil textures
1. Undisturbed sample can be taken 1, 2 or 3
2. Undisturbed sample cannot be taken 2 or 3
II. Identification of Massive Rock Substrata Above 4
the Water Table
III. Identification of Hydraulically Restrictive 5 or 6
Horizons or Substrata and Massive Rock Substrata
Below the Water Table
IV. Design of Seepage Pits 3

This test shall not be used in soil horizons or substrata containing coarse fragments in excess of 50 percent by volume or 75 percent by weight.

(d) The number and location of permeability tests required shall be as follows:
1. When the tube permeameter test or the soil permeability class rating test are used to determine the design permeability at the level of infiltration, a minimum of one test shall be conducted within each disposal field and each test shall consist of a minimum of two test replicates. The administrative authority shall require additional tests or more than two replicates per test where the variability of test results exceeds the limits allowed in 7:9A-6.2(i)2, or where the results of soil profile pits or borings, made as prescribed in 7:9A-5.2, indicate the presence of more than one soil type within the area of the disposal field. When soil tests taken in different parts of the disposal field yield different results, the system shall be designed based upon the most restrictive conditions found within the area of the disposal field.
2. When the basin flooding test, the pit-bailing test or the piezometer test are required for identification of limiting zones, a minimum of one test shall be required within or no further than 15 feet beyond the boundaries of each disposal field. The administrative authority may require more than one test where conditions vary from one part of the disposal field to another.
3. In cases where a pit-bailing or basin flooding test pit or part of a test pit has been excavated within the boundaries of the proposed disposal trench or bed, the pit shall be backfilled after use in a manner that will not result in a major discontinuity with respect to soil horizonation, density, or permeability in the soil below the disposal bed or trench.
(e) When the percolation test is used the following requirements shall be met:
1. When the percolation test is used to determine the design permeability at the level of infiltration, the administrative authority shall require a minimum number of percolation tests based upon the size of the proposed disposal field, as follows:

Size of Disposal Field Minimum
(Square feet) Number of Tests
Less than 1500 2
1500-3000 3
3000-4000 4
4000-6000 5
2. When the accuracy of a percolation test is questioned, one or more replicate tests may be performed at the same location within the disposal field as a means of better defining the true soil conditions at that particular location. The average of the results obtained from replicate tests at a given location within the disposal field shall be used for design purposes or for determination of soil suitability at that location.
3. The results of percolation tests taken at different locations within the disposal field shall not be averaged.
4. When a percolation test is abandoned due to lack of measurable percolation, this test may be disregarded provided that a minimum of three replicate tests taken at that same location yield acceptable results and provided that all subsequent test replicates taken at that location yield measurable percolation rates.
5. All percolation tests shall be located within the boundaries of the proposed disposal field and only the most restrictive percolation rate obtained within the disposal field shall be utilized for design purposes.
6. Percolation tests shall be uniformly spaced within the area of the disposal field. Acceptable patterns of percolation test placement are shown in Appendix C.
7. When a seepage pit is proposed, as allowed in 7:9A-7.6, a minimum of one percolation test shall be performed within each soil horizon or substratum between the invert of the inlet and the bottom of the seepage pit. The administrative authority may require additional tests below the bottom of the seepage pit where the presence of a limiting zone is in question.
(f) The administrative authority or its authorized agent shall witness permeability tests in accordance with the requirements of 7:9A-3.6.
(g) When the results of a permeability test or a percolation test are questionable, the administrative authority or its authorized agent may require that the test be repeated. When the tube permeameter test or the soil permeability class rating method is used, the administrative authority may collect and test replicate samples for verification of soil permeability. In cases where the results obtained by the applicant differ from those obtained by the administrative authority, the results obtained by the administrative authority shall be used for design or determination of soil suitability.
(h) Except as provided in 7:9A-6.3, only unadulterated water to which no foreign substances or chemical additives have been added shall be used to conduct permeability or percolation tests. The addition of foreign substances or chemical additives to water used for permeability testing shall be considered as a falsification of data subject to penalties as outlined in 7:9A-1.7.
(i) The results of all permeability tests or percolation tests, complete or incomplete, including all test replicates, taken within the disposal field or less than 150 feet beyond the boundaries of the proposed disposal field shall be reported to the administrative authority using data submission forms as provided in Appendix B. Results shall be reported regardless of whether or not they are acceptable and regardless of whether or not they are used as a basis for the disposal field design. Failure to report test results shall be considered a falsification of data and may subject the violator to penalties as outlined in 7:9A-1.7.
(j) The administrative authority may allow the use of test methods other than the standard test options outlined in 7:9A-6.1(c), subject to review and approval of the test method by the Department.
(k) A septic system designer shall carry out or directly supervise and certify all soil testing procedures and results relied upon as a basis for the design of an individual subsurface sewage disposal system and determine the permeability of fill material on site as determined by the tests required in (a) above.
(l) Where test sampling indicates inadequate permeability in a specific soil horizon to comply with this chapter, the test location(s) established both horizontally and vertically and an area 15 feet around the test location(s) in that same soil horizon shall not be utilized as disposal area unless three additional replicate tests are performed within that area and horizon, each of which demonstrate acceptable permeability.

Notes

N.J. Admin. Code § 7:9A-6.1
Amended by R.1993 d.294, effective 6/21/1993.
See: 24 N.J.R. 1987(a), 25 N.J.R. 2704(b).
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 (a); added (a)1 through (a)4; in (b), inserted "types of", ", or additional tests", "additional locations or alternate", a comma following "infiltration", and "or the soil conditions present"; rewrote (k); and added ( l).

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