Council approves $101,900 amendment for additional borings and monitoring at Skagit Highlands ponds
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Summary
The council approved amendment No. 2 to a consulting contract with Associated Earth Sciences to add five borings, two groundwater monitoring wells and a slope stability analysis at the Skagit Highlands ponds for $101,900, bringing the contract total to $206,900.
Mount Vernon City Council on Aug. 13 authorized amendment No. 2 with Associated Earth Sciences Inc. to expand geotechnical investigations at the Skagit Highlands ponds. The amendment adds five borings, two 40‑foot groundwater monitoring wells and continued monitoring work for a total amendment cost of $101,900; the contract total with the amendment will be $206,900.
Public works engineer Blaine Chesterfield said the firm has monitored the Highland ponds since September 2022 and previously installed two inclinometers and two groundwater monitoring wells. The additional subsurface exploration is intended to clarify the water‑bearing layers, evaluate potential dewatering options and support a slope stability analysis to identify mitigation measures.
"Approval of the proposed professional services agreement amendment No. 2 with Associated Earth Sciences will give the city additional information to determine what mitigation options are available to ensure the stability of the slope," Chesterfield said.
Council approved the amendment by motion. Staff said the extra borings and monitoring will inform whether dewatering or other mitigation steps can reduce slope movement and will be summarized in a written report and slope stability analysis for council review.
Why it matters: the additional geotechnical data will help the city evaluate mitigation options for slope movement around the Highland ponds and reduce uncertainty about potential risk to nearby infrastructure and properties.