Marion County staff and consultants propose 3.5 MGD expansion of Southwest Regional Water Reclamation Facility; commissioners ask for odor monitoring and a firm

Marion County utilities staff and Ardura consultants on Tuesday urged the Board of County Commissioners to advance plans to expand the Southwest Regional Water Reclamation Facility to about 3.5 million gallons per day (MGD) to meet roughly 30 years of expected growth and to address biosolids capacity and neighborhood odor concerns.

Tony Cunningham, Marion County utilities director, said the project team’s studies — including a 2024 supplemental conceptual design and three technical memos this year — point to a practical need for additional capacity. “Realistically, you’ve got about 3 years left of capacity in your treatment plant,” Cunningham said, noting current flows of roughly 1.1 million gallons per day against a permitted capacity of 1.6 MGD.

Why it matters: consultants told commissioners that keeping the plant at its present footprint without adding a third process tank and dedicated sludge processing will expose the system to operational strain, regulatory risk and increasingly limited sludge storage. David Rasmussen of Ardura said the recommended third process tank and associated plant upgrades would provide operational redundancy and the volume needed to re‑rate older tanks.

Cost and scope: consultants offered preliminary cost estimates for the process work and associated site improvements. Rasmussen recited an earlier 2024 estimate of about $19 million for the process components; staff and consultants estimated relocating or replacing the biosolids/digester components at roughly $8–10 million, yielding a combined planning figure near $30 million for the elements discussed. County staff also described a broader conceptual planning range of $30–60 million, using $45 million as a midpoint for initial budgeting until design work refines costs.

Odor and neighborhood mitigation: commissioners pressed staff for quantified, verifiable odor data before and after construction. County staff described a multi‑pronged approach already underway in the Oak Run neighborhood: acoustical rapid assessments of gravity mains (which flagged about 4% of lines for cleaning), targeted lift‑station maintenance and SCADA reviews, installation of carbon canisters on air‑release points, upgraded lift‑station vents and vendor‑adjusted odor‑control media. Cunningham said a chemical dosing program in three of six hotspot areas produced a roughly 90% measured reduction in odor at those locations. On site, staff proposed curtains around the open biosolids building, replacement of aging open‑air blowers (24‑week lead time), a screening/berm/opaque fence and landscape buffer (including bamboo), and moving the biosolids/digester further from residences to improve access and reduce impacts.

Monitoring: the county already deploys hydrogen sulfide smart covers and other sensors in the collection system; commissioners requested a formal pre‑ and post‑construction odor monitoring plan that would provide measurable results the county can share with residents. “We could put together … a plan to measure kind of the pre odors now,” Cunningham said, adding staff could measure post‑construction performance and report reductions.

Effluent disposal and long‑term planning: consultants flagged effluent disposal as an equally important constraint. Candidate disposal options include irrigation to golf courses, wetland recharge and use of county‑owned parcels (including a 40‑acre site) or airport land; no disposal site has been selected and consultants recommended more detailed site evaluation.

Funding and next steps: staff said about $10 million is currently set aside in the capital improvement program and $5 million per year is scheduled for the next five years. Consultants said the contract work to date has cost about $400,000 and that a proposed change order to extend design scope to include relocated biosolids work would be approximately $700,000–$750,000. The board directed staff to return with a revised scope and schedule no later than the second meeting in January; staff agreed to do so.

No formal vote was taken. The workshop closed with the chair’s instruction that staff bring back the revised scope and a firm timeline for the project. The board adjourned without taking additional action at the meeting’s close.