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5 <br /> 1 Vice-Chair Hamilton asked what science/evidence is behind what horizontal separation <br /> 2 does, and if there is a certain distance required. <br /> 3 Tony Whitaker explained that these regulatory requirements are a simplified proxy for a <br /> 4 complicated process. He described how wastewater trickles downward from dispersal lines, <br /> 5 gets treated, and then mingles with groundwater flow patterns. For wells, the casing is driven <br /> 6 down below the bedrock level so shallow groundwater cannot enter, and horizontal distance <br /> 7 helps ensure the plume of water from the drain field doesn't reach the well directly. <br /> 8 Vice-Chair Hamilton said it would be interesting to know when that science was <br /> 9 developed and if it actually tracks, especially if there is a big system with lots of homes or <br /> 10 different wells. <br /> 11 Tony Whitaker said many large systems have monitoring wells that are drilled to test <br /> 12 along the perimeter in the expected direction of groundwater flow on the downslope side of the <br /> 13 wastewater system. He explained that this is where samples are taken to determine if <br /> 14 groundwater is within normal standards. As the system is operated, it can be compared to early <br /> 15 control samples. He said a lot of communities don't use monitoring wells, but if there is a <br /> 16 concern about groundwater impacts, they can be required. <br /> 17 Cy Stober said the next presenter can speak to community well monitoring, which is also <br /> 18 a requirement of community wells. <br /> 19 Vice-Chair Hamilton asked what happens to solids during treatment. <br /> 20 Tony Whitaker said the septic tank provides primary treatment, which includes straining <br /> 21 out the solids. He said things that float will do so and remain captured, things that sink, sink to <br /> 22 the bottom, and all the septic tank outlets have a filter that strains things bigger than 1/16- <br /> 23 floating stuff does not leave, settled things don't leave, and what remains begins a biological <br /> 24 breakdown in the tank and is converted to liquid and other gases. He said tanks still need <br /> 25 pumping every 4-5 years. <br /> 26 <br /> 27 John Roberts arrived at 8:35 am. <br /> 28 <br /> 29 Vice-Chair Hamilton asked if this is a natural process. <br /> 30 Tony Whitaker said yes, biological activity is important to the breakdown of material. <br /> 31 Commissioner Fowler asked about the expense of a community system vs. more <br /> 32 individual systems. <br /> 33 Tony Whitaker said he has a slide coming up on that. <br /> 34 Cy Stober said that if there are safety measures the Board would like to include, they <br /> 35 can put these regulations in place in the UDO, like monitoring systems. <br /> 36 Commissioner McKee said if that is discussed, the Board also needs to discuss the <br /> 37 costs involved. <br /> 38 <br /> 39 <br />