Laserfiche WebLink
33 -Z <br /> <br />20 march 1975 <br />• III 11111991 uu ~:~ <br />RE::C~[1iI'p <br />APR 18 1975 <br />GDIO. u,vs~uN nF MINES <br />i~:r. Dale Rc'a~'i <br />Cooley Gravel Company <br />P,O, Pox 5435 T4 <br />Denver, Colorado u0217 <br />Dear '=1'r, Rea?:: <br />T!le purpose of ti:is letter is to repcrt the findings and <br />submit. an anal~rsis of seismometer mor:itorin~ of blasting by <br />the Cooley Gravel Company. This analysis sho~.vs that _~rowid <br />motion due to blasting at Llorrison Quarry eras yell below the <br />recommended specifications made by the "Colorado School of <br />Mines Ad Hoc Com:~ittee on Ground i,iotion due to Blasti,z~ ," <br />In addition, sound level measurements were made on the <br />eiihteenth and twentieth of i'ebruary and the sixth and <br />eighteenth of 1~;arch 1975 in regard to possible noise <br />pollution effects due to the operation of i,:crrison @uarry. <br />The Geophysics Department of the Colorado School of I•i:ines <br />has been n?onitoring quarry blasts, from Cooley Gravel <br />Ccmpany's ;1orr.ison ~auarry, by several seismometer stations <br />since 1:;arch 1973, and at least two stations since the <br />quarrying be};an, Six of these stations coirpr.ise the <br />Chatfield seismor~:eter network which is centered around the <br />Chatfield Dam. The main objective of the Chatfield Dar:. <br />project is to monitor reservoir induced seismicit!r, i-however, <br />through the cooperation of the Cooler Gravel Company the <br />quarry blasts are accurately and routi?xely monitored. Ti?etie <br />stations operate with gal??s varying between four-hundred- <br />thousand a?xd three million, and are designated as follows <br />(see figure 1): HDa-Headqua.r+.ers, ;•~TIQ-i8aterton, i:d•1V..i.:artin- <br />Idarietta Vault, TLD-Yule Lake Drive, HLP.-Highlands Rench, <br />and GCB-Green Center Building, <br />In addition to the Chatfield Stations the Colorado School of <br />Mines Geophysics Department also monitors quarry blasts <br />through operation of the Cecil }i, Green Geophysical <br />Observatory (designated GOL) at Bergen Park, Colorado, This <br />observatory is Hart of -che '~'7orld ?fide Net.vorY, of Standard <br />Seismographs and has been operatir:~ since 1962, The <br />observatory contains three-component lone ar!d short period <br />seismometers and two-component '~~ood-hnderscn seismometers, <br />The GOL data was pr1.:!arily used for the ground motion <br />analysis since GOL is a standard observatory vrith accurately <br />calibrated instruments, Blasta are yell recorded on the <br />GOL short period seisracs.eters ~•rit!i wins of either t~:o- <br />hundred-thousand cr four--hundred-thousand depending t:pon tl:e <br />