By Michael Howell
After gauging the level of interest in a Montana Ground Water Pollution Control System permit for the Grantsdale Addition, one of Ravalli County’s largest subdivisions, approved in March 2011, the Department of Environmental Quality (DEQ) has decided to re-open public comment on the permit renewal request. The original public comment period on the proposed permit renewal closed on Friday, November 29, but apparently enough interest was shown that the agency has now decided to re-open the comment period and hold a public hearing on the matter in Ravalli County.
The Grantsdale Addition is a 181-lot development proposed on 68 acres at the corner of Grantsdale Cut-off Road and Skalkaho Highway, south of Hamilton.
Build out is proposed in six phases over twenty years. The developer has until December 31, 2016 to file the plat on the first phase.
This is a renewal of an existing permit for the proposed Grantsdale Addition subdivision. The proposed facility will serve up to 181 homes and two commercial/industrial connections, with a combined average daily flow estimated at 40,000 gallons per day (gpd) and a maximum daily flow of 60,000 gpd. The commercial/industrial connections to the system are estimated to have an average daily flow of 600 gpd and a maximum daily flow of 800 gpd. The proposed design of the facility consists of individual septic tanks on each lot (provided by each individual lot owner), individual grease traps (provided by each individual commercial/industrial connection), gravity sewer lines with a possible force main, recirculating tank(s), recirculating filter(s), dosing tank(s), distribution lines, and two 30,000 gallon capacity pressure-dosed drainfields.
Raw sewage enters the septic tanks where primary treatment (settling) occurs. Effluent from the septic tanks on each of the individual lots will be conveyed via a 4-inch gravity sewer main into a recirculating tank(s) with a 45,000 gallon capacity. Effluent is then pumped from the recirculating tank into the recirculating filters for treatment. The permittee has indicated that either a recirculating trickling filter or a recirculating sand filter will be the treatment method used by the facility.
After treatment, the effluent is either returned to the recirculation tank for additional treatment or directed into a dose tank for discharge into ground water via two pressure-dosed subsurface drainfields. Each drainfield will receive up to 30,000 gpd and discharge into Class I ground water. The drainfields are in close proximity to each other and receive the same treated wastewater from the same collection system. As such, the two drainfields are designated as a single outfall.
One concern expressed by some of the respondents during the initial public comment period was that the developer was not in compliance with his previous permit and was found to be in violation, in part, by failing to install ground water monitoring down gradient from the system. The draft permit now under consideration appears to address this shortcoming by no longer requiring it. Respondents express concern about potential pollution of the ground water and subsequently the Bitterroot River and question the rationale for dropping the requirement.
Several of the respondents also apparently asked for a public hearing on the matter and the agency has decided to accommodate that request. No date has yet been set for re-opening the comment period nor has a date or venue been set for the public hearing on the matter. But Paul Skubinna, Section Supervisor for the Water Quality Discharge Permitting Section of DEQ, said that the agency is looking for a venue in Ravalli County for the public hearing.