Spring City hears geotech findings on sewer lagoons; consultants give $2.3M earthwork estimate

Consultants presenting a December geotechnical report briefed the Spring City Council on options to remediate three sewer lagoons and described soil conditions that favor reconditioning the lagoon bottoms in some areas but may require imported clay or a larger rebuild in others.

The report showed that test pits in cells 1 and 2 encountered a silty-clay cover over a stiff clay that laboratory permeability tests rated substantially tighter than the minimum regulatory threshold; a separate test pit at the south end found silty sand and gravels that are not suitable for lagoon lining. Consultants said a full earthwork rebuild of the lagoons was previously estimated at about $2.3 million.

Why it matters: the lagoons are close to overflowing during wet periods, staff said, and the chosen repair approach determines whether the Utah Division of Water Quality (DWQ) must conduct plan review and on-site permeability testing. That involvement would add steps to design and a DWQ review period that consultants estimated at four to six weeks.

Report findings and options Consultants said the site has three cells: cells 1 and 2 are “very full of water,” and cell 3 is currently dry. Test pits 1–3 had a top 6 inches of silty clay and underlying stiff clay; test pit 4 (south end) showed silty sand and gravels. A lab permeability test on samples from pits 1–3 produced about 1×10^-8 cm/sec, roughly three times slower (tighter) than the maximum standard of 1×10^-6 cm/sec mentioned during the briefing.

Consultants outlined three broad options discussed with council and staff: - Do nothing (risk continued near‑overflow and potential regulatory attention). - Treat the project as maintenance: strip and recondition the lagoon bottom in the areas where clay is present; DWQ is less likely to require formal permitting if the work is clearly maintenance rather than new construction. - Full reconstruction: strip, import/clay‑blend material where needed, place a compacted liner and run DWQ plan review and on‑site permeability testing during construction.

Regulatory and testing steps Consultants recommended an early pre‑application meeting with the Division of Water Quality to confirm whether the planned approach would be treated as maintenance or require a full plan review and permitting. If DWQ required permitting, the process would include plan review and then an on‑site permeability (double-ring or equivalent) test of the compacted liner during construction.

Costs, quantities and schedule discussed Consultants gave a high‑level earthwork cost estimate of about $2,300,000 for a full rebuild based on comparisons to similar projects. They also described a quick material takeoff that yielded approximately 9,612 cubic yards for a 1‑foot removal across the site; the working scenario discussed during the meeting — removing 6 inches from roughly two‑thirds of the area and 1 foot from the remaining third — produced an internal estimate of roughly 6,400 cubic yards total and about 3,200 cubic yards to be moved on the north end in the “move‑north‑to‑south” approach.

Consultants said preparing a bid package (survey, design/bid documents and specifications) would be the immediate next step and estimated a design base fee of about $12,000 for that work. Typical procurement and construction timing discussed: 4–6 weeks advertising for bids, 4–6 weeks DWQ review if required, and an anticipated contractor completion window on the order of 60 contract days (consultants used 60 days as a planning figure), with actual construction targeted for the drier summer months to avoid muddy conditions.

Funding and administrative issues Councilmembers and staff discussed funding options. The staff reported the city has internal PTIF (public works/infrastructure) balances and other departmental funds that could be used, but the accounting lines do not align neatly; state law and internal rules require inter‑department loans or formal budget adjustments if funds move across department accounts. Several speakers said they preferred self‑funding (using internal loans or inter‑department arrangements) rather than pursuing state or federal grants for this immediate work to avoid longer timelines and additional conditions.

Short‑term measures and implementation risk Staff proposed an immediate, low‑effort mitigation if the lagoons begin to spill: dig a small diversion ditch to keep flow in the third cell or direct it to the south end to avoid saturating additional cells while the council finalizes a design. Consultants flagged implementation risks: unknowns about the lateral extent of clay across the lagoon bottom, the condition of existing dikes/rock armoring at the pond edges, evidence of burrowing rodents that can undermine compacted liners, and the potential need to strip rock from dike faces if DWQ requires full reconstruction of side slopes.

Next steps Staff and consultants said the near‑term work is to: (1) prepare survey and bid documents (design base estimate $12,000), (2) meet with DWQ for early feedback on whether the work will be treated as maintenance or new construction, and (3) advertise the project if the council authorizes procurement. Councilmembers indicated the item will appear on the next meeting agenda for an authorization step.

Ending: The council directed staff to move the bid‑document and permitting work forward and to bring funding options (including inter‑department loan mechanics) and a recommended procurement schedule back to the council at the next meeting.