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HomeMy WebLinkAbout1999-01-07-MEMORANDUM ° © THE CITY OF 13OZEMAN , T 20 E. OLIVE • P.O. BOX 640 W BOZEMAN, MONTANA 59771.0640 Co. 0��� ENGINEERING DEPARTMENT PHONE: (406) 582-2360 • FAX: (406) 582.2363 MEMORANDUM January 7, 1999 To: Phillip J. Forbes, DPS Mike Certalic, SWS Dean Elliott, WTPS From.: Craig E, Brawner, CE Re: Lyman Creek Water Supp 'y - Surface Water Influenced Assessment I spoke with Dan Fraser regarding what he would recommend for an evaluation to determine if the Lyman Ck. supply is a surface water influenced (SWI). Much to my surprise, 'Dart did not seem overly concerned nor recall any major suspicions on, his (DEQ's)part that Lyman Ck. supply was SWI. Iie did recalled that one of DEQ's filter evaluations did pickup what was thought to potentially be a Guardia cyst, but feltthat based on the state of the art techniques available and employed at the time,it was just as likely to not be a cyst. Dan did not take the bait and propose that we jump into any study(i.e.,hire them or someone else). He did suggested the following, which appears to me to be a reasonable and prudent means to put the supply to the test and assure the public health needs of the community are met: Conduct routine annual Microscopic Particulate Analysis (MPAs) on the supply. Additionally,this first round we could conduct more rigorous testing by doing 2 or 3 MPAs during the spring runoff(highest risk)period. Do a site evaluation at the spring collection gallery,to assure that surface water influence at that Iocation is precluded. Install a continuously recorded turbidimeter on the supply (I could not recall if we had already added turbidimeters to the Lyman system). He indicated, given his recollection about the water quality of Lyman Ck. from back when we collected at the creek diversion, that he'd expect turbidity to be.I NTUs or less,and that we shouldn't expect that to increase significantly - say more than .I or .2 NTU's or so - unless we experience some inorganics flushing through when the spring high flows transition. I tend to think Dan is on target. The proof is in the pudding (hard data). If we collect the data and develop a track record,we and DEQ will have the answers,and presuming the data supports Lyman is not a "SWI" supply, we'll have some pretty good insurance against DEQ making any future determination that it is. I'd propose that we embark on this approach, and begin the data collection/documentation. In the meantime, I'll still pursue the cost-effective issue on the cover. cc: Rick Hixson HOME OF MONTANA STATE UNIVERSITY GATEWAY TO YELLOWSTONE PARK