A factor of safety of two has been applied to the soil's permeability rate. The majority of the site has soils with permeability which exceeds 20 in/hr. Therefore, it is not possible to site the proposed stormwater measures in areas with tested permeability of between 1-20 in/hr. Per the CMP, infiltration measure(s) may be sited in soils verified by testing to have permeability rates in excess of 20 inches per hour, provided that stormwater is routed through a bioretention system prior to infiltration. The majority of the site runoff to the basins will be pretreated using bioretention basins prior to infiltration. The bioretention basins have been designed in accordance with the New Jersey Stormwater Best Management Practices Manual. In areas where it is not practical to route through bioretention, and instead is routed through porous pavement, it is proposed to replace 36" of soil below the basin with K4 soils with a permeability rate of up to 20 in/hr (for Subsurface Infiltration Basin 3), in accordance with guidance received from the Commission. The replacement soil will extend up the sides of the basin to the elevation of the lowest outlet.

For all major development, as defined at N.J.A.C. 7:50-2.11, groundwater mounding analysis shall be required for purposes of assessing the hydraulic impacts of mounding of the water table resulting from infiltration of stormwater runoff from the maximum storm designed for infiltration. The mounding analysis shall provide details and supporting documentation on the methodology used. Groundwater mounds shall not cause stormwater or groundwater to breakout to the land surface or cause adverse impacts to adjacent water bodies, wetlands, or subsurface structures, including, but not limited to basements and septic systems. Where the mounding analysis identifies adverse impacts, the stormwater management measure shall be redesigned or relocated, as appropriate;

Groundwater mounding analysis has been conducted for all proposed infiltration basins on site using the USGS Hantush spreadsheet in accordance with NJDEP BMP Manual Chapter 13.