DATE: February 24, 2020
TO: Board of Mayor and Aldermen
FROM: Eric Stuckey, City Administrator
Paul Holzen, City Engineer/Director of Engineering
SUBJECT:
title
Discussion Concerning Morningside Detention Pond. (CIC 2/27/20)
body
Purpose
The purpose of this memo is to provide information to the Franklin Board of Mayor and Aldermen (BOMA) concerning an existing detention pond located in the Morningside Development.
Background
This item was added to the agenda at the request of Aldermen McLendon. Below is a summary of the background and history.
• February 3, 2003 - City staff approved the Brentwood Pointe Phase II - Lot 8 Grading and Drainage Plan. This plan included a detention pond and outlet structure located on the proposed Morningside Development. A note on the grading plan states the following: “Both Morningside and Brentwood Pointe are under legal control of Haury & Smith. Final Public Drainage Easement will be recorded at the time of recording Morningside. Maintenance of the Facility shall be the joint responsibility of the two entities referenced above.”
• March 5, 2004 - City staff approved Morningside Section 8, Lot 19 Grading and Drainage Plan. This plan showed the approved Brentwood Pointe Phase II - Lot 8 Drainage Pond.
• March 17, 2004 - Haury & Smith Contractors, Inc. signed and recorded an inspection and maintenance Agreement of Private Stormwater Management Facilities for Morningside, Section 8, Lot19 and had the document recorded at the Williamson County Registers Office.
• May 20, 2004 - Franklin Municipal Planning Commission approved the Final Plat of Morningside PUD Subdivision.
• March 24, 2005 - Franklin Municipal Planning Commission approved the Section Eight - Final Plat of Brentwood Point III PUD Villages of Morningside - Lot 19.
The stormwater maintenance within both developments are designated as “private” on both plats. On December 2, 2019, City staff completed an inspection of the facility and noted that wetland vegetation was present at the bottom of the pond and there was erosion, which requires correction, at the existing headwal. The approved Morningside, Section 8, Lot 19 plans, show the outlet structure as a headwall and the Brentwood Pointe, Phase II - Lot 8 plans show same outlet structure designed with a low flow orifice and overflow elevation. This was more than likely missed by the development team at the time and the existing headwall should have been removed and replaced with an outlet structure to reduce downstream impacts. Installing the outlet structure would allow for additional detention of offsite stormwater and reduce downstream impacts but would not correct the wetland vegetation and erosion issues associated with the pond.
Following the 2/27/2020 CIC meeting, Street Department staff visited the site and determined that the existing pond has groundwater issues. To fix the pond we would need to make some grading repairs, install an outlet structure and French Drains. The estimated cost to complete this work in-house is estimated to be around $40,000.
Financial Impact
No financial impact at this time.
Recommendation
rec
Historically, City staff has not made repairs to privately maintained ponds. We generally only work on regional ponds, similar to the Dry Branch pond located at Franklin Road and Moore’s Lane. Staff does not recommend using city resources to correct these maintenance issues. If the Board directs staff to make these repairs, we should require a long-term maintenance agreement between the City and HOA. This agreement should require future maintenance to be completed by the HOA and be recorded against the property. Staff is seeking direction from the Baord.