DATE: January 2, 2019
TO: Board of Mayor and Aldermen
FROM: Eric Stuckey, City Administrator
Paul Holzen, Director of Engineering
Jonathan Marston, Assistant Director of Engineering
Jeff Willoughby, Stormwater Coordinator
SUBJECT:
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Consideration of Resolution 2019-01, “A Resolution Directing Staff to Proceed with the Flood Insurance Rate Mapping Associated with Ralston Branch”. (Referred to 2/12/19 WS from 1/24/19 CIC 4-0; 2/12/19 WS, 05/19/19 WS)
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Purpose
The purpose of this memo is to provide information to the Franklin Board of Mayor and Aldermen (BOMA) concerning the Ralston Branch Feasibility Study and obtain direction from the Board on how to proceed with the project.
Background
Ralston Creek originates between Huffines Ridge Drive and I-65 near Centennial High School and flows in a southwesterly direction before entering into the Liberty Hills Subdivision Retention Pond. It also receives flow from an eastern channel along Liberty Pike which is listed as the headwater area for Ralston Creek. After leaving the retention pond, the stream flows through the Royal Oaks Subdivision, were staff has received several complaints from residents regarding flooding due to stormwater from Ralston Creek overtopping the stream banks. In addition, this section of stream has experienced some bank failures, which the City has attempted to temporarily address until a permanent solution could be determined and installed.
On November 19, 2015, the Board of Mayor and Aldermen approved a professional services agreement with CEC to work with Staff to prepare a feasibility study to determine potential ways to address flooding in the Royal Oaks Subdivision along Ralston Branch and to mitigate the eroding stream channel. As part of the scope of services, CEC evaluate two flood risk management options to include modifications to the existing retention pond and the installation of a dry dam in lieu of the existing retention pond. Unfortunately, none of the options showed no major impact to help mitigate flooding and stream bank erosion downstream. On September 12, 2017, the Board of Mayor and Aldermen approved an amendment with CEC to finalize the flood study along Ralston Creek in accordance to FEMA guidance and to prepare construction plans and specifications to mitigate the eroding stream channel downstream of the Liberty Hills Pond. On November 8, 2018, staff held a public meeting to go over the results of the flood study and preliminary construction plans. This meetings were well attended by the residents and our main goal was to share the results of the study and obtain input on the final design of the project.
FEMA’s study of Ralston Creek ends 240 LF northeast of the Victoria Court cul-de-sac, which is also the end of the current Flood Insurance Rate Map (FIRM). Our consultant has continued the flood study from the end of FEMA’s study upstream through Liberty Hills pond to determine the extent of the 100-year flood plain. At this point, the Board of Mayor and Aldermen have authorized City staff to finalize the design of the bank stabilization project and staff is now seeking direction from the Board on how to proceed with the formal mapping of the floodplain along Ralston Creek.
The Engineering Department is recommending that we proceed with mapping the remainder of Ralston Branch for the following reasons:
1) The City of Franklin, TN currently participates in the National Flood Insurance Program’s Community Rating System. This is a voluntary incentive program that recognizes and encourages community floodplain management activities that exceed the minimum NFIP requirements. As a result, flood insurance premium rates are discounted across the City to reflect the reduced flood risk resulting from the communities’ actions meeting the goals of the Community Rating System. There are 10 CRS classes: Class 1 requires the most credit points and gives the greatest premium discounts and Class 10 identifies a community that does not apply for the CRS or does not obtain a minimum number of credit points and receives no discount. The City of Franklin currently has a class 8 ranking. One of the requirements of this program is to continue mapping areas not shown on the current approved FIRMs.
2) The City of Franklin Zoning Ordinance currently requires the Flood Plain Administrator to regulate based on data available to include the study completed by CEC.
As part of this process the City would be required to notify all property owners impacted by the proposed FIRM changes. This was done as part of the public meeting held on November 8, 2018 and would need to be done again with formal letters being sent to all impacted property owners. It should also be noted that the CEC study shows numerous properties would be impacted by the revised mapping, but all structures included in the study currently have a finished floor elevation higher that the proposed base flood elevation. This information should allow the property owners to work with FEMA to obtain an elevation certificate to have their building removed from the special flood hazard area.
Financial Impact
Staff would need to negotiate a price with CEC to help assist with the proposed FIRM amendments. The estimated cost of this is around $35,000 to be paid out of the approved Stormwater Budget within the Engineering Department.
Recommendation
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Staff recommends approval of Resolution 2019-01.