Rule Updates:
The New Jersey Department of Environmental Protection issued a January 2019
Draft Groundwater Table Assessment Guide for Infiltration BMPs
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Stormwater management (SWM) rules at N.J.A.C. 7:8-5.2(h) require that “Whenever the stormwater management design includes one or more BMPs that will infiltrate stormwater into subsoil, the design engineer shall assess the hydraulic impact on the groundwater table and design the site, so as to avoid adverse hydraulic impact. Potential adverse hydraulic impacts include, but are not limited to, exacerbating a naturally or seasonally high water table, so as to cause surficial ponding, flooding of basements, or interference with the proper operation of subsurface sewage disposal systems or other subsurface structures within the zone of influence of the groundwater mound, or interference with the proper functioning of the stormwater management measure itself." The public comment period for these draft guidelines closed on March 1, 2019.
Groundwater Mounding Analyses Changes:
NJDEP guidance documents related to potential impacts from on-site SWM infiltration systems initially proposed groundwater mounding analyses using an empirical evaluation with methods suggested by a cooperative effort with the United States Geological Survey. This empirical methodology continues under the NJDEP guidance changes, however, the currently proposed changes provide strict direction that will, in many cases, adversely impact the estimated groundwater mound height and associated impacts at many New Jersey development sites.
