The Tooele County Board of Health made a key decision last month that hopefully will result in continued heightened stewardship of Tooele Valley groundwater and the prudent use of conventional septic tank systems in unincorporated areas of the county.
As reported in last Tuesday’s edition, the health board postponed a decision last month on whether or not to allow the use of conventional septic systems in minor subdivisions that consist of four 1-acre lots. It was proposed to allow a conventional septic system in each 1-acre lot, but only if the subdivision doesn’t exceed four acres.
However, the health board is up against a policy it adopted last March: Only one conventional septic system allowed per 5-acre lots in unincorporated areas of Tooele County.
A conventional septic system typically consists of an underground septic tank that takes wastewater from the home. It separates solids and digests organic matter, while remaining wastewater is discharged into the surrounding soil by a series of buried perforated pipes.
What prompted the health board to create the 5-acre policy was a 2016 groundwater study in response to concerns of elevated nitrate levels in Tooele Valley. That study, done by an independent engineering firm, tested 55 different private and public wells. Nitrate levels were found to range from 0.7 milligrams per liter in Lake Point to 4.8 milligrams per liter in Erda.
The U.S. Environmental Protection Agency has set a threshold for nitrates in safe drinking water at 10 milligrams per liter. However, the engineering firm recommended a lower risk level of 6 milligrams per liter. To minimize the risk of contamination of groundwater, the engineering firm also recommended a septic tank density of no more than one septic tank per five acres for East Erda, Erda/Lincoln, and West Erda areas.
According to the EPA, nitrate is an inorganic compound that occurs both naturally and synthetically in the environment. In groundwater, it originates primarily from fertilizers, septic systems, and manure storage or spreading operations. Short-term exposure to elevated levels in drinking water pose potential health risks primarily for infants, who may contract methemoglobinemia — or blue baby syndrome.
The engineering firm’s recommendations don’t stand-alone. A 1998 study by the Utah Geological Survey reportedly advised that Tooele Valley should not exceed 3,000 septic systems. At the time of study, the valley had approximately 800 septic tanks, according to county officials. By 2016, that number had grown to 2,300.
The health board’s decision on Jan. 23 includes a request for the engineering firm to make a recommendation on possible affects to groundwater if conventional septic systems are allowed in minor subdivisions that consist of four 1-acre lots.
But given the board’s 5-acre policy, growing concern over nitrate contamination of Erda’s groundwater, and continued residential growth in Tooele Valley, such an allowance may lead to greater problems in the future. If good stewardship of Tooele Valley’s groundwater is the goal, the board has a critical decision to make. And that decision should be made on fact and science.