The city of Kent will build a $4.8 million stormwater pump station northwest of the West James Street and 64th Avenue South intersection to help reduce Valley flooding.
The City Council awarded the project Nov. 5 to Tapani, Inc., of Battle Ground, which submitted the low bid. Construction is expected to start and finish in 2020.
“It will pump water directly into the Green River during high flow events and help keep the Valley dry,” City Public Works Director Tim LaPorte said to the council.
Eight companies submitted bids that ranged from $4.8 million to $6.4 million. Five of the bids were under $5.2 million. The city’s hired engineer estimate was $4.1 million.
“We are very pleased with the bids, there is very little difference between (most of) them,” LaPorte said.
Money from the city’s stormwater drainage utility fund will pay for the project. Single-family residents pay a storm drainage fee of $12.81 per month. Multifamily and commercial properties pay higher rates based on impervious surfaces, concrete driveways, parking lots and other factors.
The pump station will divert peak stormwater surface water flows from areas south of James Street directly west to the Green River, according to the Public Works Department. This will allow the Green River Natural Resources Area, owned and managed by the city Public Works Department, additional capacity to provide treatment to surface water flows north of James Street and east of 64th Avenue. All diverted flow to the Green River lower than the six-month return period storm event will continue to the Green River Natural Resources Area for water quality treatment.
The pump station will include two pumps and related hardware to connect to an existing 30-inch diameter high-density polyethylene resin force main constructed during the past summer.
Other features of the pump station will include a back-up power generator, shelters for the pump station and control systems. A maintenance garage building also will be built at the pump station site. LaPorte said additional storage space is needed for vehicles and equipment because the city’s operations facility just down James Street was built in the 1960s and doesn’t have additional space.
The project includes installing a concrete diversion structure along the 64th Avenue drainage channel and a concrete culvert to route stormwater to the pump station. The project also includes installing another concrete bypass structure and a 30-inch diameter gravity sewer piping near Hogan Park to improve drainage in that area.
This will mark’s the city’s second major pump station along James Street. The city spent $2.3 million in 2016 to replace the James Street stormwater pump station near the bottom of the James Street hill, just east of Central Avenue North. That project helps control the seasonal flooding from Mill Creek that in the past closed a primary commute route between the Valley and the East Hill.