ATTACHMENT 3

MEMORANDUM

TO:                  Cal Horton, Town Manager

FROM:            George Small, Engineering Director

SUBJECT:       Burning Tree Drive Culvert Replacement

DATE:             November 11, 2002

During and after certain rainfall events, stormwater runoff exceeds the conveyance capacity of existing drainage culverts under Burning Tree Drive and sometimes floods an adjacent residence. Town Engineering staff evaluated the problem, and we believe that the periodic flooding could be mitigated under most circumstances by replacing the existing culverts under Burning Tree Drive with larger, more efficient culverts in addition to improving the channel into which the culvert discharges.

This issue was brought to Council’s attention on June 10, 2002 as part of the Manager’s recommendations for allocation of remaining 1996 Drainage Bond Funds. At that time we estimated that the project cost could range between $40,000 and $65,000.  Since then we have completed more refined design work and we now have a more realistic cost estimate.

The proposed Burning Tree Drive drainage improvements would involve replacing the existing culverts and associated structures with concrete box culverts.  The improvements would also re-shape and improve the channel downstream of the culverts to accommodate the increased discharge.  We have determined that the channel section proposed for improvement is within an existing 30’ wide drainage easement.

 This project would be coordinated with all affected downstream and upstream property owners, including the Chapel Hill Country Club. We have been in discussions with representatives of the North Carolina Wetlands Restoration Program (NCWRP), and we think it is likely that they would include our proposed channel improvements in a larger stream restoration project they are considering in this area.  If so, NCWRP would provide funding for the channel improvements associated with the culvert replacement project.

We now estimate that the proposed Burning Tree Drive drainage improvement project would cost approximately $100,000.   We recommend using $60,000 in unexpended 1996 Street Bonds funds and an additional $40,000 in CIP funds.  If the Council concurs, we could begin work on the project before the end of the year.  If the NCWRP agrees to fund some of the project improvements, the Town’s level of funding could be reduced accordingly.

The culvert replacement will likely occur prior to the stream restoration project, so design and construction of the stream and channel improvements would need to be coordinated between Town staff, affected property owners, and NCWRP staff.