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<br />United States Department of the Interior <br />NATIONAL BIOLOGICAL SURVEY ~~ <br />Nauonal Ecology Research Center <br />4512 McMurry Avenue <br />Fort Collins, CO 80525-3400 <br />April 12, 1994 <br />In Reply Refer To: File: 516.08A <br />R8/NBS/NERC <br />Robert Baldwin, President <br />West Arapahoe Soil Conservation District <br />730 Si~ams Street, Suite 416 <br />Golden, CO 80401 <br />In Reference To: Mining Peaiinst No. M/88/044 <br />Dear Mr. Baldwin: <br />This batter serves as a record of expenditures and progress <br />report of our work at the Coal Creek site through the first <br />quarter ending March 31,1994. <br />.Promo r~e:as Re ort: As usual we have continued monitoring the <br />ground wa er wells once mont{~ly throughout the winter months. We <br />will soon resume monitoring twice monthly during the growing <br />season.. <br />We have: worked up the longitudinal survey data that was completed <br />last fall. In a distance of 5351 meters along the channel, the <br />elevation decreases by 31 meters; a slope of 0.006. It is <br />evident: in the pprofile where the sand mining has occurred (Figure <br />1). Before we be an the longitudinal surveye the miners had <br />begun regrading the channel at the lower mining area. Therefore, <br />the depression is less evident and more smooth than the upper <br />mining area. The zero elevation is benchmark 1 on the upland <br />near Transect 4 (Figure 2). Figure 3 is a cross section of the <br />channe]. at Transect 2 before and after mining. <br />To reiterate our observations, we have included some graphs <br />depicting Change over time. Figure 4 describes the change in <br />ground water elevation from June 1991 to June 1993. The water <br />table ttas dropped five feet at Transect 2 as a result of the sand <br />mining. The mining in this location began in the middle of June <br />1992. As a result of the decline in the water table, 63 percent <br />of the trees in Transect 2 have died (Figure 5). Furthermore, no <br />increase in basal area was recorded at the same location (Figure <br />6) . <br />Plans: We will be presenting our observations in a poster <br />drp ay at the Society of Wetland Scientists (SWS) meeting in <br />Portland, Oregon during the first week in June. With an <br />additional year of monitoring completed, it should be more in <br />depth than our presentation in Denver last year. <br />h~ <br />To correctly tie the transects together, we need to survey two <br />existing points on each transect from certain benchmarks on the <br />longitudinal survey; This will allow all the transects and <br />ground water elevations to be related to a single elevation. <br />