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~II II~II~II~"~~ I~~ • United States Department of the Interior FISH AND WILDLIFE SERVICE N ATIONAL ECOLOGY RESEARCH CENTER 4512 McMurry Avenue Fort Collins, CO 80525-3400 In Reply Refer To: FWS/Region 8/NERC June 30, 1992 Robert. Baldwin, President West Arapahoe Soil Conservation District 730 Simms Street, Suite 416 Golden, CO 80401 Dear Nlr. Baldwin: In Reference To: Mining Permit No rn~~ PRIDEN~ .~ ~ ^ RWEP: 516.08a M/88/044 This letter serves as a record of expenditures and progress report of our work at the Coal Creek site through the second quarter ending June 30, 1992. Progress~Re~ort~: As usual, we have continued measuring our ground water wells twice monthly during the spring and summer months. In addition, we have continued to take photos from our permanent photo points. We were able to record additional discharge data during a flow event June 1st. The discharge was slightly less than the first event we recorded (see attachment provided in the March 18, 1992 report). An interesting point to note is there was much less flow at transect 4. Transect 4 is the "control" transect located upstream of the sand mining activity. This suggested to us that we might be seeing the first effects of the mining operation (i.e. exposing the sub-surface water, resulting in increased surface flow downstream). A recent trip to the site (June 25) revealed a large increase in mining activity. Mining operations have begun at Transect 2. At this location, the channel is rather wide and the operators have dug two deep trenches along each edge of the channel. These trenches are below the water table, therefore the ground water is being drained from this area. We have seen a relatively large drop in the ground water table at Transect 2. In three ~deeks, well no. 5 has dropped 0.51 feet, well no. 6 has dropped 0.98 feet, and well No. 7 has dropped 3.04 feet (see attachment No. 1). Up to this point, the largest drops we have seen in these wells have been 0.38, 0.42, and 0.41 f~aet, respectively. We surveyed several points across the channel along the centerline to document the changes in channel morphology. In addition, we resurveyed some missing points. During this past quarter, we performed some photo interpretation of the channel configuration from aerial photographs for the years of 1937, 1950, 1957, .1963, 1969, and 1986 (see attachment No. 2). All in all, it appears the channel has migrated very little. However, it has expanded with flood events, and then contracts between floods within several years. We can correlate the channe'I widening to documented flood events that have occurred in the past. Since Goal Creek does not have a flow gage, we assume that flood events along Cherry Creek (with a gaging station near Franktown, Colorado} coincided with floods at Coal Creek. We assume this because both drainages originate along the Palmer Divide, and in fact, the flood years at Cherry Creek do correlate with our photo interpretations of Coal Creek. We have flow data for the years