HomeMy WebLinkAboutApplication Files_82693_pg0392 ' Transportation
Land Development RECEIVED
Environmental
' Services AUG�+ i )
8 Z O 11 101 Walnut Street
f P.O.Box 9151
SOUTH WINDSOR PLANNING DEPT. atertown,MA 02471-9151
617 924 1770
FAX 617 924 2286
' Memorandum To: File Date: March 8,2010
Project No.: 72189.00
' From: Marla Keene,EIT Re: Technical Memorandum
Mounding Analysis-
Connecticut Studios,
South Windsor,Connecticut
' Introduction
This memorandum has been prepared to describe the performance of the infiltration system
proposed as part of the stormwater management system at the above referenced site to determine
potential impacts to groundwater both on and off the site. The infiltration system was evaluated
through a groundwater mounding analysis.Details of the design approach for the infiltration
' systems as well as the modeling analysis,including assumptions and findings of the analysis,are
provided herein.
' The overall stormwater management system for the project site is designed to infiltrate 100% of
the stormwater runoff from the 100-year recurrence interval 24-hour rainfall event as described in
USDA's Technical Report 55 (June 1986). The stormwater management system has been designed
to meet the following goals:
■ Maintain existing hydrologic conditions and flow patterns at the Site boundary;
' E Match or reduce the peak rate of runoff to existing levels.
A summary of the overall stormwater management system for the site is provided in the
' following section.
Project Overall Stormwater Management Summary
' As shown on Figure 1 (Grading and Drainage Plan),the drainage system consists of:
• Two small collection basins located at the Northern site perimeter to collect flows from
' off site areas and direct them to the closed drainage system,
• Four small biofiltration/infiltration areas located to collect runoff from driveways at the
' Southern site perimeter,
• Double catch basins throughout the project Site,
• One large existing infiltration area located on the Southern end of the Site,
• One large infiltration pond located on the Southern end of the Site and
• _-One_large_subsurface infiltration system located on the Western-boundary-of-the-Site -- - - ---
receiving flow from the majority of impervious surfaces on the site.