Flood Mitigation Projects
The City has constructed a variety of projects over the years to help reduce flooding in neighborhoods and on streets. Additionally, the City does a number of annual, biannual and by each rain event preventative maintenance cleanings to keep stormwater sewers and waterways clear so the infrastructure moves water through the system effectively. Below, find a number of ways the City works to maintain stormwater infrastructure and see some of the recent projects that have been constructed.
Ongoing Storm Sewer Maintenance
- Annual maintenance
- Willow Creek Basin Cleaning
- City Engineering has a basin on University Avenue that collects rainwater. In Spring of 2018, Engineering crews removed 305 cubic yards of debris
- Biannual Catch Basin Cleaning
- In April and October of every year, City crews clean catch basins in the City. During this clean, on average, crews clean approximately 1,200 structures and clear, on average, 480 tons of debris, per season since 2016.
- Priority Grate Cleaning
- After and prior to rain events, City crews clear 763 structures of debris which allows stormwater to flow through them more effectively. Priority Grates would include anything from inlets to dead ends and big grates on large storm sewer.
- Willow Creek Basin Cleaning
- ~10 miles of storm sewer built/replaced annually
- Streets Division maintenance by the numbers for 2021:
- Total miles swept (when sweeping the City multiple times): 58,684
- Total tonnage of debris collected: 6,473
- Greenway mowing/debris removal – all the stuff we do to maintain our system in an attempt to keep the conveyance system clean.
- Hawk’s Landing Flood Mitigation
- Lower Badger Mill Creek Pond
- Mendota-Grassman Greenway Flood Mitigation and Restoration
- Sauk Creek Greenway Restoration
- University Avenue Relief Pipe Phase II
McKenna Boulevard Flood Mitigation Project
Project Location & Purpose
The City of Madison's West Badger Mill Creek - Elver Park Greenway is a channel that carries stormwater from as far north as the Beltline, through Greentree Pond, and under McKenna Blvd. to the pond in Elver Park. Many homes and businesses are located directly adjacent to this greenway, including homes located on cul-de-sacs along Park Edge Dr., multifamily homes in the vicinity of Schroeder Rd., and residential and commercial area along Struck St. Since 2016, Park Edge Dr. residents have experienced several rain storms where water from the greenway flooded the neighborhood and entered their homes. This impact was most severe in August 2018. Additionally, McKenna Blvd., which is a main thoroughfare through the neighborhood and houses police and fire stations for the west side of the city, has overtopped and become impassible several times. During flooding in August 2018, several properties along Struck St. also experienced inundation and a senior apartment and assisted living facility needed to be evacuated.
In response, City Engineering designed and constructed a public works improvement project to mitigate the recurring flooding in this neighborhood, on McKenna Blvd., and along Struck St.
Phase 1 Scope Summary
Construction of Phase 1 was completed between July 2019 and May 2020 and included the following improvements:
- Three existing pipes under McKenna Boulevard were removed and replaced with two 5’ tall by 10’ wide box culverts and two 5’ tall by 12’ wide box culverts, which greatly increased flow capacity under the road. This work included constructing new inlet and outlet wing walls.
- Existing concrete channel was removed and replaced with a new concrete channel 1.5 feet lower than its previous level.
- A retaining wall was constructed along the west edge of the greenway to provide significantly improved flow capacity in the channel that runs adjacent to Greentree Landfill.
- Existing metal pipes at the outlet of Greentree Pond were removed and replaced with two 4’ tall by 8’ wide box culverts. The pond outlet and channel were also realigned to point southwest, rather than west, to prevent flows from going directly towards the back side of homes on Falmouth Ct.
Phase 2 Scope Summary
Construction of Phase 2 was completed between June 2020 and August 2020 and included the following improvements:
- Existing metal pipes at the inlet of Greentree Pond were removed and replaced with four 42” concrete pipes. The new pipes have invert elevations 1.5’ lower than the old pipes.
- The natural channel between Greentree Pond and Schroeder Road was excavated to be 1.5 feet lower than the old channel.
- Three existing pipes under Schroeder Road were removed and replaced with two 4’ tall by 8’ wide box culverts, which have capacity to carry the 1% chance storm without overtopping onto Schroeder Road. These culverts were realigned to discharge south-southwest, away from the mixed use path, and the new culverts were set 1.5 feet lower than the old pipes.
- The Schroeder Road profile near Struck Street was reshaped to create a low point that better facilitates street drainage.
- Existing concrete channel was removed and replaced with a natural channel that is lower than the old channel and has a 2’ deep pool of standing water.
Southwest Bike Path/Waite Circle Culvert Reconstruction
In 2017, the original stone arch culvert under the Southwest Bike Path at Waite Circle began to fail. In 2017, as a result of the impending failure, the arch was slip lined with a 60-inch culvert during an emergency repair.
The devastating flooding that occurred in June and August of 2018 made it clear that the emergency repair’s size was not adequate to convey the stormwater under the bike path. In late 2019 the culvert was reconstructed with an oversized box culvert. A restrictor plate was installed on the upstream size of the oversized box culvert. This plate restricts the flow to be about the same as what the original arch culvert could convey. In addition to the culvert reconstruction, the Madison Metropolitan Sewerage District Intercept beneath the culvert was reconstructed and relocated adjacent to the proposed box culvert.
University Ave Relief Storm Sewer
The University Avenue Relief Storm sewer consists of 96-inch pipe and 10 foot by 6 foot box culvert that extends from Grand Avenue to Willow Creek. The pipe was installed in four phases, which occurred in 2003, 2004, 2011 and 2013. The purpose of this sewer is to divert water from a 12 foot by 6 foot storm sewer box, located beneath University Avenue and installed in 1925. The 1925 box was known to be undersized, even for the time, but costs prohibited construction of the full design, which proposed two 12 foot by 6 foot storm boxes. In the years following the original construction, the street corridor filled with other utilities and eliminated the possibility of fitting additional storm capacity beneath University Avenue. Therefore, the relief pipe was installed along the southern embankment of Campus Drive. Diverting water from the 1925 box creates additional capacity in the system, allowing University Avenue to drain more rapidly.
Park Edge Dr Flood Mitigation
The Park Edge Drive Flood Mitigation was designed to address stormwater sewer overflows within an easement where the public stormwater sewer was constructed through a condominium association property. The capacity of the stormwater sewer would run full during large rain events and significantly reduce parking lot surface drainage which caused flooding issues within the private property.
City Engineering worked with the property owner to create an easement and move the stormwater sewer main to the driveway and route toward the Greentree South Section Greenway. City Engineering increased the pipe sizes and capacity of the new stormwater sewer routed through the new easement and converted the old public main for private parking lot drainage use.
Bram Street Pond
Stormwater runoff from Alliant Energy Center’s parking lot drains to the west to Lykberg Park and the Bram Street area. Residents on Bram Street experience flooding at times of high lake levels and major rain events.
To help control the runoff from the Alliant Energy Center parking area, Dane County dedicated a storm and drainage easement over a portion of Lyckberg Park which allowed the City of Madison to design and construct a pond for detention and storm water quality purposes.
Due to the limited easement area, the pond was designed to provide detention in the ten-year design storm event. Storm sewer and vain drains were extended into the Alliant Energy Center parking lot to divert storm water to the pond, cutting off a portion of the parking lot from draining directly to Bram Street.
Impact Fees for Drainage and Stormwater
- Valley View
- West side drainage
- Mineral Pont Rd drainage