Missoula Area 



Aquifers in the Missoula area were discussed briefly in 

 Chapter 1. The most productive of these, the Missoula 

 Aquifer, is the major source of qround water in the Missoula 

 Valley and the sole source of drinking water for area 

 residents. 



Recent chemical data for the Missoula Valley Aquifer are 

 available from the Mountain Water Company and the Missoula 

 Aquifer Study, which is being conducted in cooperation with 

 the Missoula City-County Health Department (MCCHD) and the 

 University of Montana. Data from 1984 to 1986 indicated no 

 violations of State of Montana primary drinking water 

 standards, with many of the trace metals below detection 

 limits. The Missoula Valley Aquifer Study did show some 

 coliform bacteria contamination, although Mountain Water 

 Company monthly samples showed no such contamination. Small 

 community water supplies are sampled once every five years 

 for chemical parameters, and data from 3 3 such supplies 

 indicate no exceedence of Montana primary or secondary 

 standards (Missoula City-County Health Department 1987) . 



Maintaining the high quality of the Missoula Aquifer is 

 of the utmost importance, as it supplies individual wells, 

 two municipal water systems, over 30 small community systems, 

 and several large industrial users (including Stone Container 

 Corporation) . The MCCHD submitted a petition to EPA in 

 December 1987 for a sole source aquifer designation for the 

 Missoula Aquifer to ensure a reliable high quality source of 

 water for current and future users. The EPA granted the 

 petition in June 1988. 



Much of the Missoula Aquifer is overlain by thin, coarse 

 soils, and depth to ground water is generally shallow. 

 Natural attenuation of contaminants by adsorption, neutral- 

 ization, ion exchange, biodegradation, and other processes is 

 limited; therefore, the aquifer is quite susceptible to 

 contamination. Potential sources of direct contamination 

 identified by the MCCHD are listed below. 



Yellowstone Pipeline (high-pressure gasoline pipeline) 

 Milltown Reservoir sediments 



Pesticides from the Missoula County Weed Control Program 

 Browning-Ferris municipal waste landfill and historic 



landfills 

 Burlington Northern Railroad diesel refueling site 

 Sewage disposal seepage pits 

 Underground fuel and chemical storage tanks 

 Urban storm water 

 Septic systems 

 Industrial waste ponds 



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