OCR Text |
Show PAGE 10 THE ZEPHYR AUGUST 1995 Life of Waters the Protecting s water Keeping growth from affecting the quality of Spanish Valle By Lance Christie If you follow the local news closely, you've seen articles about: Grand County requiring new subdivisions to be hooked up to sewer in a "Valley Aquifer Impact Zone" in Spanish Valley before they can be approved. A groundwater study in Spanish Valley being funded by a grant from the Environmental Protection Agency under Section 319 of the Clean Water Act, with matches from state and local government The United States Geologic Survey (USGS) will be doing the research. - Spanish Valley Water and Sewer Conservancy District obtaining a major loan and grant funding package to expand the sewer system in Spanish Valley. - The Spanish Valley Water and Sewer Conservancy District participating in the cost of expanding the Moab Sewer Plant. All these governmental initiatives are related. They all serve to protect the blessing which creates our oasis in the high desert - dean, culinary-qualit- y groundwater. Here's the underlying story: Public and private drinking water in Moab comes entirely from two underground aquifers: The "Gass 1A Pristine Ground Water" Acquifer The larger and better aquifer has its recharge zone in the La Sal Mountains between Geyser Pass and Miners Basin. Mountain snow and rain percolates down into the Gen Canyon Croup of sandstones, which are tilted downwards in a northwesterly direction towards Spanish Valley. Just past Mill Creek, the flow of water encounters a complex of faults on the east side of Spanish Valley, which block the flow of water. The water rises to the surface all along what older geologic maps call the "Eastern Moab Fault." The largest springs at the south end - Somerville 1, 2, and 3 - are used for the Moab City water supply, supplemented by six wells. Five of the six wells and Somerville 2 and 3 are located at the Moab Golf Course. The huge Skakel Spring behind the Grand Old Ranch House also feeds into the Moab City water system, and McConkie and Birch Springs in Old City Park have in the past. Moab City's total water rights on all the wells and springs totals 5,086.25 gallons per minute. Southwest of the Moab Golf Course, Spanish Valley Water and Sewer Conservancy District uses two wells belonging to George White to produce the water it distributes south of Moab City. The water rights for these wells arc 1,800 gallons per minute. Spanish Valley W&SCD swaps Ken's Lake irrigation water with Mr. White. Thus 946,080,000 gallons of Ken's Lake water are converted to culinary use each year. There arc other springs in this same trend which are used for private domestic water systems. Matrimony Spring on the river road opposite Lion's Park is the northernmost spring in this trend. A few private water wells on East Bench Road and Acres subdivision access this aquifer. in The State of Utah Ground Water Quality Protection regulations classify water with dissolved solids below 500 mg1, and no pollutants, as "Class 1A" or "Pristine Groundwater." This is the highest classification, and there arc stringent requirements that such pristine waters be protected from degradation by pollutants. The various wells and springs in this aquifer show from 184 to 287 mg1 dissolved solids, and most did not show any pollutants such as nitrates, bacteria, or petrochemicals, when last tested. Alas, some did! One of the objectives of the USGS groundwater study is to assess what is going on and what measures need to be undertaken to prevent and rectify problems. an The "Class II Drinking Water Quality Ground Water" Acquifer The second aquifer we use for drinking water lies in the bottom of Spanish Valley, which is a "salt collapse" valley. The Utah Geologic Survey recently completed survey maps of the valley show the various work on the Moab area. Their and then geologic strata curving upwards, particularly under Behind Blue Hill South the from on Arches to runs on disappearing. Spanish Valley (which the north on geologic maps) has a bottom filled with day, sand, gravel and rock washed down from glacial action in the La Sal Mountains. Below this alluvium, between 150 and 350 feet depending on where you are, you hit the Paradox (salt) formation - the remains of a sea which was cut off from the ocean and evaporated during the Pennsylvanian Period, between 280 and 325 million years ago. Normally around 5,000 feet thick, the Paradox is believed to be up to 14,000 feet thick under Spanish Valley! As soluble salt was dissolved out of the top of the Paradox by those glacial streams in the ancient Spanish Valley, the sand and minerals suspended in the salt consolidated into a soft, highly mineralized sandstone which is between 100 and 300 feet thick to the extent drilling has discovered - on top of the crystalline salts. Thus, if you drill between 350 and 700 feet deep in the valley floor, you hit salt. The Class II acquifer can be visualized as a pool of water sitting in a fractured bathtub filled with sand and gravel, which is sitting on top of a mountain of salt. The salt acts like a very thick fluid, rather than a solid - it moves around, bulging up here and sinking down there. This bulging and sinking causes swarms of microquakes in cross-secti- on -t- he-Rocks, From the La Sal Mountains comes Moab's culinary water of the future, the overlying rock, which range up to Richter 4.0 in magnitude. The largest concentration of these quakes occurs in the Lockhart Basin, downstream on the Colorado River from the Atlas Uranium Mill. Water comes into the Gass II acquifer from three sources: (1) rainfall on the surface, which doesn't amount to much; (2) overflow from the Class 1 A acquifer along the east side, as it pours over the of the fault dam and sinks down into the top alluvium; (3) underground recharge from Pack Creek - and from Ken's Lake when it leaks. The range of dissolved solids in the Gass II acquifer runs almost precisely three times that in the Class 1A. One of the City of Moab drinking water wells is in the ss acquifer: the Corbin Well," which the City doesn't routinely use because of the mineral deposits this water learn in pots and on windshields. Most of the private wells in Spanish Valley draw water from the Class II acquifer. The U.S.G.S. reports at out of 20 samples drawn by C.T. Sumsion in 1968 and 1969 from private wells in the Class II acquifer, 5 had nitrate levels ten times the normal level found earlier. The s und rom mtr:?.te mjnurc leaching. We didn't have fccdlots upgradient 1 wc W.C s now; did havc septic tanks f . upgradient. The septic tank that lh,C nitralCS from loach ficlds localized to j supposed stay upwards and evaporates. So what's happening? of the soils, sands and gravels deposited "TV0 m lhc 8l0l0sy in Snankv ribbons of glacial streams. As A8 s' you go from north to f the varnhiT1015 alluvial fill cons'stlncy upper gets coarser and . more 5tate wil not allow a cra8c; septic tank permit if you have percolation 5 minul PCF in il Out along thbSan Juan County c nkhCinCr Cy' ,comc UP with percolation rates up to 34 inches per minute n ,jncK's P1 minute found at ten foot interval;, going cither horiyontaH1 vertically Septic leachate sticks around and percolate, upward " m amy SOiU- U drops likc a rock ndsand VwhjJ ,hrou8h gravels. and that wp'v got as wc go south in Spanish Valley. because the water - |