Identifying solutions to the drainage problems highlighted over the weekend when rain squalls flooded intersections and basements could take the city of Tacoma several weeks or months.
City officials are zeroing in on two problem spots: the swamped intersection of Pacific Avenue and South Tacoma Way, and Stadium Way, where rainwater forced 100-pound manhole covers off their seats and closed the road for several hours Saturday and Sunday.
The city was braced for the storm, briefing crews late last week about the weather forecast and scheduling 12-hour shifts through the deluge, said Mike Slevin, head of Tacoma’s Environmental Services Department.
South Tacoma fared well due to the city’s prep work, Slevin said. Crews drained part of the gravel pit near 84th Street and Interstate 5 that collects South Tacoma’s stormwater to make room for the coming rainfall, Slevin said.
The city also rented pumps to help move water out of Flett Creek. A $3 million upgrade to the city-owned pump station on Flett is in the works but not scheduled to be in operation until Oct. 8.
“Given the intensity of the storm, it could’ve been much worse,” Slevin said. “I don’t know if we even had any minor flooding in South Tacoma because the crews were working so hard.”
The city also controlled flows on Leach Creek to avoid flooding homes, he said. That water was pumped to a small holding pond in Fircrest.
But near Pacific Avenue, there was nowhere for the water to go but onto city streets. The squall struck the area at high tide Saturday, and the city’s stormwater system was not designed for such a high amount of water, Slevin said.
The rainwater, which normally would have flowed through culverts into the Foss Waterway, quickly filled the intersection of Pacific Avenue and South Tacoma Way with 10 feet of water.
Some of that water flowed east across a parking lot and into a gully near Interstate 705 and then into what used to be a creek bed. The water then roared downhill and into the basement of The Storage Box. More than 60 units were flooded with about 9 feet of water Saturday.
The Pacific Avenue and South Tacoma Way intersection has flooded a couple of times in the past three months because of heavy rainfall, said Rae Bailey, division manager of street operations for Tacoma Public Works.
Slevin said the city is discussing ways to prevent such flooding from happening again during these types of storms.
“It could take months to figure out what to do,” Slevin said. “It was these very high-intensity, short-duration storms that come in waves that really tested our system and identified some pinch points.”
On Stadium Way, Slevin said, the city is in the early stages of retrofitting the stormwater system to increase the amount of water it can handle. Such a retrofit could cost around $600,000, he said.