TO: Mayor and Members of City Council
THRU: Adam Lindsay, Assistant City Manager
FROM: Sheila Thomas-Ambat, PE, Public Services Director
DATE: September 25, 2023
RE:
Title
Watershed Master Plan Solutions for Blounts Creek
end
COUNCIL DISTRICT(S):
Council District(s)
All
b
Relationship To Strategic Plan:
Supports Goal 3. City Investment in Today and Tomorrow, through the Strategic Objective 3.1 Enhance City street connectivity, traffic flow, and stormwater systems
Executive Summary:
Staff seeks concurrence from the City Council on the approval of the 100 proposed solutions from the Blounts Watershed Study to enable staff to program them into the annual CIP prioritization process and pursue grants as applicable. The full suite of proposed solutions was presented in detail to City Council at the September 5, 2023 Work Session under agenda item 4.02 and approved to move forward on consent at a City Council Regular Meeting.
Background:
Priority 1 areas in the Blounts Creek Watershed have been studied as part of the first set of watersheds in the Watershed Master Plan program. Because of the size of the Blounts Creek watershed and the number of sub-basins identified as Priority 1, this watershed study was broken into four separate packages, with Packages 1 through 3 covering sub-basins in the upper part of the watershed and Package 4 covering the lower part to include the downtown area. While flooding impacts identified in Packages 1 through 3 were mostly related to secondary system deficiencies, much like the first four watersheds brought to Council in December, flooding impacts in Package 4 were shown to be mainly caused by ponding due to restrictions to the primary system.
The total number of Concern Areas identified in the Blounts Creek Watershed is 136, with 23 in Package 1, 16 in Package 2, 19 in Package 3, and 45 in Package 4. A total of 100 proposed solutions have been developed, for a total cost of $314,882,500. The majority of the proposed solutions are capacity expansion. Proposed solutions were prioritized based on a combination of non-biased, data-driven factors including concern area score, efficacy of the solution, equitability across the watershed, and other strategic considerations.
The Package 4 area is the highest priority area in this watershed and solutions have been developed for both the secondary and primary systems. Of the solutions developed for Package 4, the Russell and Person Streets Proposed Solution offered the highest return on investment. This solution requires upgrading the Person Street bridge from 50’ to 70’; upgrading the 100’ Russell Street to a 120’ 3-span structure, and upgrading the railroad bridge between traffic lanes to 120’ as well; and, stabilizing, restoring, and providing additional floodplain storage from downstream of Person St to S. Cool Spring St. The cost of this proposed solution is $20.5 million. The solution is currently moving forward with the design. A $200,000 Golden Leaf grant has been awarded for the stream enhancement portion of the project. A BRIC application has been made and the project was ranked number 5 out of 36 in the state. This project is estimated to provide a $24.7 million dollar benefit over 10 years in flood risk reduction and property damage from the primary system solution. Stream enhancements will provide an environmental and public benefit contributing to a resilient watershed.
Prioritized dams within the watershed from the Citywide Stormwater Storage Screening Report by FNI (May 2021) were evaluated for their capacity to serve as dry or wet detention depending on the status of the dam. The analysis found some dams had only a moderate benefit and others had none. The City will look to further quantify the ones with moderate benefit as funding allows.
Nine of the top 10 proposed secondary solutions are in the downtown area and are estimated to cost $29 million dollars.
Issues/Analysis:
Based on modeling results, flooding impacts are substantial across the watershed and especially in the downtown area, with 46.5 miles of lane length of roads impacted. Likewise, the number of impacted structures is substantial with 155 during the 10-year, 138 during the 25-year, and 112 during the 50-year event. A prime concern for the City is the number of disconnected dwelling units and other structures, and in this watershed modeling results for the watershed indicate 366 such impacted structures. The City is also concerned about the road crossings impacted during flooding events, of which there are 13 in this watershed.
The Blounts Creek Watershed Proposed Solutions resolve 33.8 miles of impacted lane length, 1 traverse road crossings, and 216 disconnected structures. This solution also resolves flooding for 91 impacted structures during the 10-year event, 46 impacted structures during the 25-year event, and 65 impacted structures during the 50-year event.
Council has previously approved advancing the Russell Person St Bridge Replacement and Stream Enhancements project to design. Since 9 of the top ten proposed solutions are in the downtown area, that project will need to be constructed first. Currently, funding is unavailable for additional projects in this watershed and the capacity of staff to manage additional projects is limited.
.
Budget Impact:
No budget impact
Options:
1. Approve the 100 proposed solutions to enable staff to program them into the annual CIP prioritization process and pursue grants as applicable.
2. Do not approve the 100 proposed solutions and remand back to staff with additional guidance.
Recommended Action:
Approve the 100 proposed solutions to enable staff to program them into the annual CIP prioritization process and pursue grants as applicable.
Attachments:
Watershed Masterplan Solutions for Blounts Creek 2023_REVISED9.pdf