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City of Blackfoot 2018 Storm Drain Improvements Holly Powell City of Blackfoot Treasurer ---PAGE BREAK--- City of Blackfoot Flooding in Blackfoot The City of Blackfoot often experiences flooding in the streets at multiple locations throughout town even during relatively moderate rainfall events. ---PAGE BREAK--- City of Blackfoot The Catalyst • August 6, 2014 – The City of Blackfoot experienced nearly 2 inches of rainfall in less than an hour. • The storm water system became overloaded and City streets, parking lots, and basements flooded. • The City’s sanitary system started filling due to inflow through the manholes, which caused the sewer to back up in to residential basements. • This also caused excessive flows at the Wastewater Treatment Plant (WWTP), resulting in an EPA violation. ---PAGE BREAK--- City of Blackfoot ---PAGE BREAK--- City of Blackfoot ---PAGE BREAK--- City of Blackfoot The Study • The City hired J-U-B Engineers to do a Storm Water System Assessment • Due to budget constraints, it was decided to focus on the northern portion of the system that discharges into the Snake River. • The study was completed in January 2016. ---PAGE BREAK--- City of Blackfoot Findings of the Study • Using the City’s GIS information, a hydraulic computer model of the storm sewer was created. • The model identified bottlenecks in the system and JUB recommended 10 major improvements that were needed to add capacity. • A Phase 1 project was developed to: • Upsize key trunk lines in the lower part of the system where the worst flooding often occurs • Leverage available funding • It was recognized that future phases of work will be needed. ---PAGE BREAK--- ---PAGE BREAK--- City of Blackfoot The Phase 1 Project • Upsized approximately 1,800 feet of storm drainage trunk line in Jensen Grove Drive from 12- and 18-inch pipe to 48-inch pipe. • Upsized approximately 1,700 feet of storm drainage trunk line in Parkway Drive from 8- and 12-inch pipe to 36-inch pipe. • To fit within existing grades and retain gravity flow, we included a small pump station to pump out, drain, and empty a section of storm sewer that remains full after storm events. ---PAGE BREAK--- City of Blackfoot The Grant Award • On August 22, 2017, the City of Blackfoot was awarded a $2,620,000 Hazard Mitigation Grant • The match of $982,005 came from City funds. • Knife River was selected as the contractor. ---PAGE BREAK--- City of Blackfoot Storm Pond Grading – October 2018 ---PAGE BREAK--- City of Blackfoot Pipe work on Jensen Grove Drive – April 2019 ---PAGE BREAK--- City of Blackfoot Setting manholes – April 2019 ---PAGE BREAK--- City of Blackfoot Paving on Jensen Grove Drive and Parkway Drive – June 2019 ---PAGE BREAK--- City of Blackfoot Partnerships IOEM Informal Visits and Training Sessions City of Blackfoot Put the City on the Application Path ---PAGE BREAK--- City of Blackfoot Partnerships Bingham County City of Blackfoot Grant Application Requirement Fulfilled ---PAGE BREAK--- City of Blackfoot Partnerships – Letters of Support Created a strong grant application and built support for the project, both before and during. ---PAGE BREAK--- City of Blackfoot Partnerships – BCA • The Benefit Cost Analysis was a challenge. • After the application had been reviewed, Blackfoot did not meet the “over 1” threshold. • Partnered with Tetra Tech • We were able to gather data and create statistical models of flooding events • Final BCR was 1.81 ---PAGE BREAK--- City of Blackfoot Successes – Knife River’s Proactive approach Storm drain line being installed near the pond – Fall 2018, resulted in no dewatering issues. ---PAGE BREAK--- City of Blackfoot New manhole and drop inlets were installed as crews encountered them along the pipe route. New sections of concrete curb and gutters were also replaced. Successes ---PAGE BREAK--- City of Blackfoot New sections of sewer service piping was installed as Knife River crews passed them during the storm drain line installation. New lines were checked for slope and fit as they were being installed. Successes ---PAGE BREAK--- City of Blackfoot The City, JUB, and Knife River worked together to repair the break and resume construction. Success? ---PAGE BREAK--- City of Blackfoot Project Outcomes • Project benefited commercial and residential entities, city streets, and parking lots • There were only 5 change orders. • In spite of challenges with aged infrastructure, high traffic, unknown underground utilities, etc., change orders that were not owner-initiated were less than 2% of the project cost. • Performance period was 8/23/2017 to 11/30/2019. Project was started on October 4, 2018 and ended on September 4, 2019. • The project is estimated to protect 960 people, 214 properties, and 2.2 miles of roadway and storm drain lines. • The project has not fixed all of the City’s flooding issues and future phases will be needed, but we have started down a path. ---PAGE BREAK--- City of Blackfoot The Takeaways… ---PAGE BREAK--- City of Blackfoot Wastewater Improvements Phase II: $14M ---PAGE BREAK--- City of Blackfoot West Bridge Street Bridge Replacement: $12M