Project · Northlake, Seattle
Site utilities, and a storm main the project did not need
The job
A new building near the north shore of Lake Union, on a site underlain by old undocumented fill. The foundation design called for the fill to be cut out, compacted and rebuilt before any footing was poured.
What we found before the bid
The street improvement plan called for a 217-foot storm main with three manholes and two curb inlet catch basins, 1,000 square feet of soil cells under the sidewalk along the frontage, and the right-of-way restoration to go with them.
While pricing that work we noticed that the survey did not add up, and said so in the bid. Then we went to the site. We located the existing pipes with a camera, ran a dye test, and confirmed that the survey was wrong: the property already had an approved point of discharge for its stormwater.
The street improvements had been designed around a problem the site did not have. Once the design was corrected, the storm main and the soil cells came out of the project, and the street work that remained was a fraction of the original. By our estimate that saved the project roughly half a million dollars.
What we did
- Excavation: cut to footing elevation and exported 60 truckloads of soil.
- Subgrade: compacted the existing fill, laid geogrid, then imported and compacted 32 truckloads of crushed rock.
- Pier footings: augered 45 holes for round column forms, some three and a half feet deep.
- Stormwater: an infiltration trench with drain rock, perforated pipe and fabric, and two catch basins.
- Sewer: 110 feet of side sewer in a shored trench.
- Water: a new service across a public trail, with the trail detoured, saw-cut and restored.
- Paving: roughly 1,500 square feet of road, sidewalk and parking lot.
- Finishing: footing backfill, compost and mulch soil amendment.
Working with the design
We priced the drawings as they stood, and listed where they disagreed with each other, such as a pipe size shown one way on the plan and another way in the detail. Those questions went to the team before construction started.
