While the sprayground in Redmond’s Centennial Park closed earlier than normal this year, it could be up and running by its usual May opening date.
Crews in early September discovered the pavement settling near the fountain. Excavation revealed broken pipes and soil settling inside the 600-square-foot vault that holds the plumbing and electrical systems for the fountain, which sprays water from a variety of openings embedded inside a concrete pad.
“We brought in a geo-technical engineering firm to look at it, and they said it looks like the compacted soil used to backfill the vault was not solid enough,” said City Engineer Mike Caccavano.
Soil shifting and settlement provided too much leeway for the pipes to move; three breaks were found during the inspection.
“It can be really difficult to compact soil when there’s so much (infrastructure) under there,” he said. “You can’t use a heavy roller in those situations.”
The sprayground was built in 2010 by Kirby Nagelhout Construction Co. and was no longer under warranty; a fact that has not stopped the company from assisting with the repairs, said Caccavano.
“Kirby’s really stepped up and is standing behind their work,” he said. The city is providing crews and some equipment, while Nagelhout is doing the rest without cost to Redmond.
To avoid a similar problem down the line, the city opted for another approach to refilling the equipment vault now that plumbing repairs are complete. Instead of compacted native soil again, or a weak cement/soil combination sometimes used in such applications, the city will refill the area with pea gravel.
“None of solutions are foolproof, but with the gravel we use a plate compactor that vibrates the gravel, so it settles into every niche,” said Caccavano. And while tedious, removing small bits of gravel to access areas needing repair in the future is simpler than tearing up chunks of concrete.
In another departure from the initial installation, the city added a vertical pipe in the vault that will act as a drain if any water builds up in the future. With membrane fabric-covered slots along the pipe to allow water to flow into the pipe, an automatic sump pump will take out any excess water.
Nagelhout will repair the concrete slab that covers the vault, said Caccavano, and the entire project is expected to be wrapped up before Thanksgiving.