Sewer capacity shortfall: BOMA weighs on‑site treatment, I&I work and a temporary pump‑and‑haul for builders

Spring Hill staff warned the Board of Mayor and Aldermen on Oct. 20 that the city’s water reclamation facility currently reports a rolling 12‑month average flow of 4,230,000 gallons per day (4.23 MGD). With the Tennessee Department of Environment and Conservation reporting threshold at 5,000,000 gpd, staff said the city has roughly 800,000 gpd of remaining capacity but recommended maintaining an internal buffer and not allocating fully to the 5.0‑MGD cap.

Staff presentation and six buckets

City staff described six categories of vested commitments and estimated gallons per day associated with each: building permits already issued (approx. 357,000 gpd), grading permits (approx. 165,500 gpd), project sewer reservations tied to approved ordinances (Legacy Point, Spring Hill Commerce Center — combined estimates nearly 294,000 gpd after adjusting for units already vertical), critical infrastructure (hospital, public works — about 63,000 gpd), projects with engineering approval but no grading permit (approx. 172,000 gpd), and requested construction approvals (nearly 500,000 gpd). When combined with current flows, staff estimated commitments substantially exceed available capacity and said they would prepare policy recommendations for the board to prioritize or reduce commitments to roughly 700,000 gpd remaining for allocation.

Operational context and risks

Staff emphasized that monthly spikes above 5.0 MGD have occurred in the historical record, typically during wet weather, and said the 4.23‑MGD figure is the number reported to the state and serves as the working floor for allocation decisions. The water leadership team signaled they would not recommend allocating to the full 5.0‑MGD cap; staff suggested planning in the 4.2–4.9 MGD range to maintain contingency and allow for unknowns such as tenant build‑outs.

Alternative on‑site treatment and I&I

Staff said they are pursuing standards and specifications for alternative on‑site treatment systems (staff identified a Bioclear‑type system used in other jurisdictions) and plan to bring a formal recommendation in November–December. City staff and outside consultant OHM will also advance an inflow‑and‑infiltration (I&I) program update that overlays rainfall and I&I repairs; previous packages produced meaningful but incremental flow reductions. Staff warned that alternative systems depend heavily on site soils, reserve soils and proper loading‑rate design; some projects may be unable to use on‑site systems because of geologic constraints.

Pump‑and‑haul request from D.R. Horton

D.R. Horton (represented by Patrick Pitts, land‑acquisition manager) asked the city to explore a temporary pump‑and‑haul arrangement for roughly 55 lots at Harvest Point while the on‑site system is completed (company said target online date for the on‑site system is next summer). Staff described regulatory requirements, including state operating permits, receiving‑facility commitments to accept hauled flow, frequent documentation/inspection and renewals (typically 12‑month permits), and operational safeguards (prefer hauling from the reclamation plant wet well rather than small lift stations to preserve surge storage). Board members asked for details on hauling frequency, bonding/financial assurance, contingency for vendor failure, and precedent that would bind future applicants. Several members authorized staff to pursue regulatory conversations and prepare standards so the board can consider narrowly tailored, short‑term agreements rather than open-ended permission.

Next steps

Staff will produce a detailed project‑by‑project list and release it to developers for verification. Staff intends to return with a prioritized policy recommendation, draft standards for alternative systems, and the regulatory pathway for any pump‑and‑haul permits in November–December. The board repeatedly emphasized the need for transparent, data‑rich materials and consistent standards so decisions are defensible and reproducible.

Quoted from the meeting

"If anybody asks going forward, what's the number? 4.2. That's the number. Not anything... So everything that we talked about after this is based off of saying, okay. If we're at 4.2, what do we do between 4.2 and 5?" — Dan Allen (staff)

"There is not enough remaining capacity at the water reclamation plant to serve all of the vested projects." — Dan Allen (staff)

"We may have to look at on‑site systems and strict standards, but some smaller sites or poor soils may not be viable candidates." — Mr. Napier (city administrator)