Stormwater Management Report
South Hope Chapel Rd. Subdivision
Project #23184
The results of the analysis are summarized below:
| 2-Year - Current Adjusted (CFS) | 10-Year - Current Adjusted (CFS) |
| POA | Existing | Proposed | Existing | Proposed |
|---|
| 1 | 0.77 | 0.42 | 1.56 | 0.62 |
| 2 | 0.12 | 0.10 | 0.31 | 0.15 |
| 3 | 0.0 | 0.14 | 0.0 | 0.19 |
FAILURE ANALYSIS
Downstream stability can be satisfied by reducing the post development peak flow rates to 50% of the predevelopment peak for a 2-year storm and 75% of the predevelopment peak for a 10-year storm. The designed stormwater management system will reduce the peak flows by the required amount as summarized below:
| DOWNSTREAM STABILITY ANALYSIS |
| 2-Year - Current Adjusted (CFS) | 10-Year - Current Adjusted (CFS) |
| POA | Existing | Proposed | Existing | Proposed |
|---|
| 1 | 0.77 | 0.0 | 1.56 | 0.0 |
| 2 | 0.12 | 0.0 | 0.31 | 0.0 |
| 3 | 0.0 | 0.0 | 0.0 | 0.0 |
The proposed stormwater management has been designed in accordance with the Pinelands Comprehensive Management Plan as outlined below:
7:50-6.84(a)6 Surface water runoff, in accordance with N.J.A.C. 7:8-4.6, 5 and 6, as amended, except as modified and supplemented, as follows:
Runoff Rates and Volumes, runoff quality, and groundwater recharge methodologies:
Stormwater runoff rate and volumes shall be calculated in accordance with N.J.A.C. 7:8-5.7, except that the Rational Method for peak flow and the Modified Rational Method for hydrograph computations shall not be used; and
The stormwater runoff rate and volumes have been calculated in accordance with N.J.A.C. 7:8-5.7. The NRCS methodology using a Type D storm distribution and the Delmarva unit hydrograph has been utilized in computing stormwater runoff. All significant land features and structures, such as an on-site depression have been accounted for. The pervious and impervious surfaces have been calculated separately to compute the rates and volume of runoff from the site. County specific data has been utilized to determine the precipitation depths. The current and future precipitation depths have been calculated and utilized.
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