New Jersey Stormwater Best Management Practices Manual March 2024
Chapter 12: Soil Testing Criteria Page 14
Soil profile pits, separated by equal distances, must be conducted along the boundary of the footprint.
The number of soil profile pits conducted must be sufficient to determine the extent of the
hydraulically restrictive horizon in all directions.
A hydraulic head test, as defined at N.J.A.C. 7:9A-5.9, shall be conducted in the soil that immediately
underlies a perched water table to determine whether an artesian condition exists. An artesian
condition is defined at N.J.A.C. 7:9A-5.8 (f).
If the hydraulically restrictive horizon extends beyond the footprint, the infiltration BMP must be
relocated to another location that is not affected by the perched water table or the highest elevation
of the perched water table shall be assumed to be the SHWT for all aspects of design and soil testing.
If the hydraulically restrictive horizon does not extend beyond the footprint, the hydraulically
restrictive horizon may be excavated and replaced with sand.
Under no circumstances may an infiltration BMP be located in soils that exhibit artesian
groundwater conditions. If artesian conditions exist, the hydraulically restrictive layer may not be
excavated and replaced. The proposed infiltration BMP must be relocated to avoid the artesian
aquifer.
Section 2: Soil Tests for Stormwater Management BMPs
For the purpose of determining the soil testing requirements of this chapter, stormwater BMPs may be
broken into two categories: infiltration BMPs and non-infiltration BMPs. Stormwater infiltration BMPs
are those BMPs which rely on infiltration for groundwater recharge, stormwater runoff quality and/or
stormwater runoff quantity control. Infiltration BMPs include, but are not limited to, a bioretention
system without an underdrain, a dry well, an infiltration basin, a sand filter without an underdrain, a
pervious paving system without an underdrain or a GI MTD that infiltrates the runoff into subsoil. Non-
infiltration stormwater BMPs are BMPs which do not utilize infiltration to meet any of the design and
performance standards for stormwater management measures.
Saturated soil hydraulic conductivity and depth to SHWT are of high importance for the design of
stormwater BMPs. Infiltration BMPs are required to test the saturated soil hydraulic conductivity and
identify the depth to SHWT at the proposed BMP location. Certain non-infiltration BMPs may require
knowledge of the SHWT but not the saturated soil hydraulic conductivity, such as an underdrained
bioretention basin, an underdrained sand filter, an underdrained pervious paving system, an extended
detention basin, subsurface gravel wetlands or a grass swale. Non-infiltration BMPs that require a
minimum separation from the SHWT are required to identify the depth to SHWT at the proposed BMP
location. Manufactured Treatment Devices that are not required to maintain a minimum separation to
SHWT, green roofs, blue roofs, above-grade cisterns and above-grade small-scale bioretention BMPs
situated on impervious structures, such as downspout planter boxes and vegetative filter strips are not
required to test the depth to the SHWT. Tables 5-1, 5-2 and 5-3 in the Stormwater Management rules
and Chapters 9, 10 and 11 of the BMP Manual list the minimum separation from the SHWT for stormwater
BMPs.
Take note: There are non-infiltration BMPs which do not require information on the SHWT, but these
may still require information on the saturated soil hydraulic conductivity to determine if the soil