Minutes 11-14-2025-Work Session - Laserfiche WebLink

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5 Vice-Chair Hamilton asked what science/evidence is behind what horizontal separation does, and if there is a certain distance required. Tony Whitaker explained that these regulatory requirements are a simplified proxy for a complicated process. He described how wastewater trickles downward from dispersal lines, gets treated, and then mingles with groundwater flow patterns. For wells, the casing is driven down below the bedrock level so shallow groundwater cannot enter, and horizontal distance helps ensure the plume of water from the drain field doesn't reach the well directly. Vice-Chair Hamilton said it would be interesting to know when that science was developed and if it actually tracks, especially if there is a big system with lots of homes or different wells. Tony Whitaker said many large systems have monitoring wells that are drilled to test along the perimeter in the expected direction of groundwater flow on the downslope side of the wastewater system. He explained that this is where samples are taken to determine if groundwater is within normal standards. As the system is operated, it can be compared to early control samples. He said a lot of communities don't use monitoring wells, but if there is a concern about groundwater impacts, they can be required. Cy Stober said the next presenter can speak to community well monitoring, which is also a requirement of community wells. Vice-Chair Hamilton asked what happens to solids during treatment. Tony Whitaker said the septic tank provides primary treatment, which includes straining out the solids. He said things that float will do so and remain captured, things that sink, sink to the bottom, and all the septic tank outlets have a filter that strains things bigger than 1/16—floating stuff does not leave, settled things don't leave, and what remains begins a biological breakdown in the tank and is converted to liquid and other gases. He said tanks still need pumping every 4- 5 years. John Roberts arrived at 8:35 am. Vice-Chair Hamilton asked if this is a natural process. Tony Whitaker said yes, biological activity is important to the breakdown of material. Commissioner Fowler asked about the expense of a community system vs. more individual systems. Tony Whitaker said he has a slide coming up on that. Cy Stober said that if there are safety measures the Board would like to include, they can put these regulations in place in the LIDO, like monitoring systems. Commissioner McKee said if that is discussed, the Board also needs to discuss the costs involved.