O30 Princeton Hydro Report Dated 9 3 25

West Essex Highlands Review West Orange, NJ Permit No. 722-04-0001.1 LUP230001 April 2025 provides guidelines for determining the upper limit of the zone of saturation which is known as the SHWT. The chapter states there are two methods for determining the SHWT: 1. Where mottling showing redoximorphic features is observed at any season of the year, the SHWT shall be taken at the highest level at which mottling is observed except when the water table is observed at a higher elevation. ' 2. When mottling showing redoximorphic features is not observed the SHWT shall be determined by water level elevation observed in the soil pit or boring when the testing took place from January through April. Although the identification of redoximorphic features should be a key element of any soil investigation focused on the identification of a SHWT, an understanding of the soils or soil series mapped by the United States Department of Agriculture is an important initial step as it describes the various soil characteristics that may be encountered during an investigation. Copies of the USDA Official Soil Series Descriptions for the Boonton, Haledon and Hasbrouck Soils series are provided as an attachment to this letter. There are two soil series that are mapped over the mdjority of the Site, Boonton and Haledon. The Boonton soil Series is described as being “very deep moderately well and well drained soils formed in till on uplands.? One of the distinctive features of this soil series is the presence of a fragipan at an average depth of approximately thirty inches. The fragipan is a restrictive horizon that is a firm soil layer that has low to very low hydraulic conductivity. The Soil Profile Description for this soil describes the presence of “a perched water table at a depth of 46-91 centimeters (18-36 inches) from November to May of most years.” The Boonton Soils are classified as a Hydrologic Soils Group (HSG) C due to the presence of the fragipan which serves to impede the downward movement of water. The other common soil series on the Site is the Haledon series. The Haledon series “consists of very deep, somewhat poorly drained soils in low positions on undulating uplands.” This soil series also possesses a fragipan in which the hydraulic conductivity is very slow or slow. The Official soil series description indicates that there is “a perched water table within

plands.” This soil series also possesses a fragipan in which the hydraulic conductivity is very slow or slow. The Official soil series description indicates that there is “a perched water table within 30 centimeters (12 inches) of the soils surface from late winter to early spring of most years and following periods of extended rainfall."3 Redoximorphic features are present in the B horizon which begins at approximately eight inches below the ground surface. In addition, the only hydric soil identified on the Site is the Hasbrouck series. This soil “consists of deep, poorly drained soils in depressions on uplands.” These soils also have a fragipan that occurs from 40-76 centimeters (approximately 16 to 30 inches). The depth to the water table is indicated to be 0-6 inches.* Although all three soils described above possess fragipans and both the Haledon and Hasbrouck series possess redoximorphic features within the upper eight inches of the ground surface it is important to note that none of the multiple subsurface investigations identified either a fragipan or any redoximorphic features in any single soil profile across the entire site. That is not only very ' New Jersey Stormwater Best Management Practices Manual Chapter 12: Soil Testing Criteria. March 2024. Page 12 https://dep.nj.gov/wp-content/uploads/stormwater/bmp/nj_swmp_|2.pdf 2 USDA Official Soil Series Description: Boonton Series. 3 USDA Official Series Description- Haledon Series. “USDA Official Series Description- Hasbrouck Series Princeton Hydro, LLC Page | 4