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a III IIIIIIIIIIIIIIII ~ ~°f -: ~ ~~il'~ United States Department ~f the Interior V~~~A F[SH ,iND WILDLIFE SERVICE \\ ~~"-~ Y,~TIONAL ECOLOGI' RESEARCH CENTER \~'~''~'~.°' 4512 McMurry Avenue Fort Collins, CO 80525-3400 In Reply Refer To: FWS/F;egion 8/NERC ' Robert Baldwin, President October 13, 1992 F- West Arapahoe Soil Conservation District 730 Simms Street, Suite 416 Golden, CO 80401 In Reference To: Mining Permit No. M/88/044 Dear Mr. Baldwin: RWEP ra~~ Ptn~cep,/M~~~~ ~~iINW i 516.OSa This letter serves as a record of expenditures and progress report of our work at the Coal Creek site through the third quarter ending September 30, 1992. PROGRESS REPORT: As we noted in the last quarterly report we were seeing initial evidence of adverse effects as a result of sand mining activities which. were draining ground water from some areas through a system of ditches. The citches also resulted in increased surface flow downstream. We have now seen some dramatic changes in the tree vigor as a result of the decline of the water table in an area that includes our Transect R2. The annual fluctuation of the ground water elevation has remained quite consistent since the beginning of our monitoring in August 1990. However, when the heavy mining activity at Transect 2 began in the middle of June 1992, the water table at this location dropped very rapidly (See Figure 1). In fact, the ground water at well No. 5 at the end of August 1992 was almost 1.2 feet lower than at the end of August 1991. Furthermore, well No. 6 and well No. 7 were almost 2.5 feet and 2.2 feet lower than last year, respectively (See the inset of Figure 2). Well No. 5 is furthest away from the channel and well No. 7 is adjacent to the channel. Compare these data with ground water data at Transect 4, our upstream control cross section (see Figure 3 and the inset of Figure 4). Note that at the end of August 1992, the net change in the water table at Transect 4 was only about 0.4 feet lower than at the end of August of last year. Currently, the decline of the ground water at Transect 2 has stabilized and appears to be dropping at about the same rate as the ground water at the control transect. We recently completed the 1992 crown vigor assessment for the four transects (760 trees in all). This process took wee k_<. The vigor assessment was based on a percentage of crown for each individual tree. We allowed a ten percent possible error in our assessment. We consider a 15 to 20 vigor to be significant and indicative of an actual declii all of the trees in a little over two a 100 percent full change in vigor as percent change in ie in vigor.