Page 58 - Kevin-Thistle Downs Subdivision

MI MI MO On MN INS MIN NW MIN OMM MO SIMI MI NM =II IIIII OM 2011

THISTLE DOWNS

STORMWATER MANAGEMENT

ON-SITE MANAGEMENT: The closed depressions along Asbury Road contain 14.4 acre-feet of volume within
the planned stormwater management areas. For a fully developed condition, using an ISR of 0.41 for the entire
Planned Unit Development, 5.56 acre-feet of detention volume will be needed to maintain pre-development runoff
conditions.

The Planned stormwater management areas will be sufficient for proposed development. Pre-developed and

developed condition hydrographs are included in this appendix.

OFF-SITE MANAGEMENT: Two existing culverts under Asbury Road discharge to the Interstate 24 right-of-
way. The eastern culvert discharges to a partially closed cave opening on the east side of I-24. This opening also
drains a portion of the Interstate median and east right-of-way.

The western culvert under Asbury Road discharges to the inlet of a 42" diameter culvert under Interstate 24. This
culvert is sloped southwest, and discharges to a large, shallow closed depression northwest of Heatherwood
Subdivision, in Rutherford County.

This situation was discussed with Rutherford County engineering staff. There were no existing complaints or
issues with current drainage conditions in this area. Additional development within Heatherwood will encompass
this depression, and will be reviewed and permitted under County jurisdiction.

Runoff to this area from the Thistle Downs PUD will be attenuated and managed within the planned stormwater
management areas.