The hydrology for the site was calculated using the NRCS Runoff Equation and Dimensionless Unit Hydrograph as noted in Part 630, Hydrology National Engineering Handbook. The following particular references were used:
Curve Numbers were established via Chapter 9 – Hydrological Soil-Cover Complexes
Time of Concentration were calculated in accordance with Chapter 15
Rainfall Distributions are based on NOAA Type D rainfall distribution
The Delmarva Unit Hydrograph was utilized
The rainfall depths are based on Ocean County NOAA Atlas 14 Data as noted below:
Return PeriodNOAA Atlas 14 Rainfall Depth (inches)
2 Year Storm - Current3.42
2 Year Storm - Projected4.04
10 Year Storm - Current5.38
10 Year Storm - Projected6.34
100 Year Storm - Current9.48
100 Year Storm - Projected11.41
Based upon the Ocean County Soil Survey, the soil types native to the site include:
Soil TypeSoil Type NameHydrologic Soil Group
DofgBDowner gravelly sand loam, gravelly substratum, 2 to 5 percent slopesA
Based on the methodology and data noted above a hydrologic evaluation of the NJDEP Water Quality, 2-, 10-, and 100-year storm event was prepared.
This report will address compliance with the following standards:
Groundwater Recharge Standards (NJAC 7:50-56.84(a)6.iv(1))
Stormwater Runoff Quality Standards (NJAC 7:8-5.5 and NJAC 7:50-56.84(a)6.iv(6))
Stormwater Runoff Quantity Standards (NJAC 7:8-5.6 and NJAC 7:50-56.84(a)6))
Calculation of Stormwater Runoff (NJAC 7:8-5.7 and NJAC 7:50-56.84(a)6)
Green Infrastructure Standards (NJAC 7:8-5.3 and NJAC 7:50-56.84(a)6)
1980 Swarthmore LLC DEC #3342-99-007
August 2023 Last Revised February 2026