Memorandum

City of Lawrence

Engineering

TO:	David Cronin, P.E., City Engineer
FROM:	Matt Bond, P.E., City Stormwater Engineer
Date:	July 1, 2013
RE:	Ridge Court Stormwater Improvements

The Stormwater Engineering Division recently finished improvements to the existing storm sewer system in the 2800 block of Ridge Court. The 1996 Stormwater Management Master Plan identifies this area as "Project Number 7". In 2005 the property at 2814 Ridge Court was acquired to address area flooding with the construction of a detention basin. The recently completed stormwater project utilized this detention basin in its design.

Two 18" diameter high density polyethylene (HDPE) pipes were installed side by side along the east property line of the properties along the east side of the street (refer to attached map).  These two pipes were connected to an existing curb inlet on the east side of Ridge Court and terminated in the existing detention basin.  The existing right of way already contained a 36" reinforced concrete storm sewer pipe, a 6" cast iron water line and an 8" inch sanitary sewer line. The location of these existing lines necessitated the new storm sewer be located in the back yards.  Topography dictated that smaller diameter dual lines be utilized instead of a single larger diameter pipe. The acquisition of additional easement adjacent to an existing utility easement enabled the installation of the new pipes.  It should also be noted that the installation of a new line within the right away along the west side of the street was explored.  However this option was eliminated when it was discovered that the existing flow line elevation of the ditch to the south was too high.

Complete project materials and labor costs totaling $22,168.13 were paid for with a Community Development Block Grant. An additional $9,700 was spent on the appraisal and acquisition of the necessary easements to complete the project. The completion of this project enables the current storm sewer system to adequately convey the 10-year design storm event.  It also helps to alleviate potential stormwater concerns with future redevelopment activities for the northeast corner of 27th and Iowa.

Recently installed 18" diameter HDPE storm sewer pipe.

Detention basin with the new outfall of the 18" diameter HDPE storm sewer pipe