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Engineer’s scenarios show trade-offs: lower up-front cost for STEP but higher long-term burden for some owners
Summary
Wallace Group figures presented to the board show private upfront connection costs of about $16,400 (gravity) versus $39,200 (STEP), while 30-year ownership cost per residence is roughly $88,000 for gravity and $97,000 for STEP; staff stressed trade-offs between up-front private expense and long-term tax-funded capital.
District staff walked the board and public through Wallace Group’s 30% design scenarios, emphasizing technical trade-offs and lifecycle costs. Guy Savage summarized the firm’s baseline numbers: a private residential upfront connection cost of approximately $16,400 under the gravity-collection baseline versus about $39,200 under a STEP approach. Over a 30-year lifecycle Wallace Group’s baseline projections put per-residence cost of ownership near $88,000 for gravity and about $97,000 for STEP.
Staff and the Wallace consultant highlighted secondary technical issues that materially affect cost and feasibility: equalization tanks (storage to manage flow to the receiving city), dewatering depth and costs for deeper gravity pipelines, bridge-hang versus creek-bore construction methods and easement acquisition. Carrie Wagner of Wallace Group was present to answer technical questions and confirmed that the firm’s costing included baseline contingency and a range (low–high) not fully shown in the summary numbers. Board members requested additional work to quantify easement and litigation risk assumptions (Wallace used $5,000 per parcel as a placeholder in its STEP easement estimate) before the board finalizes a preferred system.
