Wallace Group presents 30% design for Los Olivos sewer collection; gravity and STEP options compared

Carrie Wagner, principal and chief operating officer of Wallace Group, told a Los Olivos community workshop that the firm produced a 30% design and a 30‑year life‑cycle analysis to let the district and residents compare a gravity sewer and a STEP (septic tank effluent pump) system. "This is really going to help support a transparent, educated decision for the community and for the board," Wagner said during her presentation.

Wagner said the gravity alternative would route private sewer laterals to a district-owned main (minimum 8 inches) that conveys flow to an east/west collection system and lift stations that pump to the City of Solvang. The STEP alternative places a pressurized tank and pump on each property and conveys only liquids to Solvang. "The construction costs, for the gravity collection system has estimated at $51,200,000," Wagner said; she reported the STEP capital estimate at about $38.6 million and warned that construction estimates at this stage can vary by +/-30%.

Wallace Group included a 30‑year net present value in its comparison. The firm presented an NPV for the gravity system of roughly $52.9 million and for the STEP alternative of about $39.6 million. Wagner emphasized the STEP option shifts more of the upfront construction cost onto property owners (tanks, periodic solids pumping and easements) while a gravity system concentrates capital on deeper mains and larger pipes under the public right of way. She listed next steps as additional surveys, potholing, geotechnical work and negotiation with Solvang, the county and the Regional Water Quality Control Board before an engineer's report and rate study are completed.