36 Hampden Street stormwater excerpt.pdf
9-14-2020
Northampton, MA
32 Perkins Ave
Pioneer Development, LLC
Prepeared For:
Northampton, MA
36 Hampden Ave
Location:
Stormwater Report
Notice Of Intent
413-626-8167
Chesterfield, MA 01012
PO Box 262
The Engineer Group, LLC
The Engineer Group LLC
413-626-8167
36 Hampden St
Northampton, MA
MA Notice Of Intent
Storm Water Report
Massachusetts Department of Environmental
Protection (DEP) - Stormwater Management
Standards
As demonstrated below, the proposed Project complies with the DEP
Stormwater Management Standards.
Standard 1: No New Untreated Discharges or Erosion to
Wetlands
The Project has been designed to fully comply with Standard 1. The Best
Management Practices (BMPs) included in the proposed stormwater
management system have been designed in accordance with the
Massachusetts Stormwater Handbook. Supporting information and
computations demonstrating that no new untreated discharges will result from
the Project are presented through compliance with Standards 4 through 6.
Standard 2: Peak Rate Attenuation
The project is a redevelopment, and it has been designed to comply with
Standard 2 to account for the proposed increase in impervious area on the site.
The rainfall-runoff response of the Site under existing and proposed conditions
was evaluated for storm events with recurrence intervals of 2, 10, 25 and 100-
years. Drainage areas used in the analyses are shown on page 4 of the
drawings. The HydroCAD model is based on the NRCS Technical Release 20
(TR-20) Model for Project Formulation Hydrology. Printouts of the HydroCAD
analyses are included in the Appendix. A table on Drawing 4 presents a
summary of the existing and proposed conditions peak discharge rates. The
results of the analysis indicate that there is no increase in peak discharge rates
between the pre- and post-development for the 2yr, and 10 yr storms.
Standard 3: Stormwater Recharge
The project is a redevelopment, and has not been designed to comply with
9-14-2020 Page 8 of 10
The Engineer Group LLC
413-626-8167
36 Hampden St
Northampton, MA
MA Notice Of Intent
Storm Water Report
APPENDIX A
Standard 2 Peak Rate Calculations HydroCAD
5-30-2020