Algae is every lake’s nightmare. It chokes off the oxygen that fish need to live and raises the costs to make the water drinkable. As the algae problem in Washington’s Lake Whatcom grew worse, City of Bellingham leaders decided to make waves with a major addition.
The City chose the most sustainable solution to manage raw water treatment: a state-of-the-art dissolved air flotation (DAF) pretreatment system. The new system, housed next to the existing water treatment plant (WTP), will pre-treat water from the lake before it enters the current filtering process. The plant will also produce its own hypochlorite, a chemical that eliminates the need for chlorine gas.
Harris was hired to manage the $15 million system’s construction process and provide professional consultation, including a constructability review study at the 95% design phase. Among the many challenges facing the Harris team: The existing plant must stay fully functional—providing drinking water to 80,000 people—with minimum disruption during the 19-month construction.
Since the new building will be on a cut slope, it required measures for slope stability, probable dewatering and monitoring the adjacent building for settlement. The preparation required Harris to manage a significant cut of 55 feet of the adjacent hillside along with the removal of hundreds of trees and 7,000 cubic yards of soils prior to excavating for the DAF foundation. The area was also riddled with existing utility lines, known and unknown, added since the WTP opened in the late 1960s. Harris handled the maze of wires smoothly, removing or relocating all utilities to prepare for a well-managed pipeline installation.
Because the lowest level of the new 90’ x 90’ DAF building is 12’ below ground at the nearby roadway, the existing WTP first floor and future DAF second floor will be at nearly the same grade. Shoring for the DAF excavation includes an approved engineered fabric wall shoring system, chosen for its cost, the ability to excavate through it later and because it can be left in place.
Beyond the Blueprints
From the start, the Harris team energetically enhanced the client relationship through ongoing communication. The City’s liaisons were kept in the loop via Newforma project management software and weekly videoconference construction meetings.
Harris mounted a cellular camera on site, enabling 24/7 review of the work, with all photos saved to an unlimited cloud server. The City uses these photos for monthly reports to their funding partner, the Washington Department of Health’s Drinking Water State Revolving Fund group. For further site examination, Harris brought in sub-consultant Geo Test to perform drone photography.