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<br />SUBURBAN <br /> <br />~~ I ~~ 303-421-0720 <br />Mail: 5400 Fenton St., Arvada, Colo. 80002 <br />Plants: 5400 Fenton St. - 11755 Brighton Rd. <br />~ S '~ 5A9NU AND GRAVEL CO. <br />coP~ w si~.p~ <br />May 13, 1998 ( oZ /x~~ <br />I ' Mr. Thomas A. Schreiner I ~ iECEIVED <br />,' Division of Minerals and Geology <br />. Minerals Section - North SAY I8 19~ <br />1313 Sherman Street, Suite 215 <br />Denver, Co 80203-2273 Division of Minerals&Geology <br />Dear Mr. Schreiner: <br />RE: Suburban Sand and Gravel Co. <br />Technical Revision for Road Runners Rest II <br />M-79-195, Adams County <br />Thank you for your letter of May 11, 1998 advising us to <br />submit a Technical Revision before dewatering our mining operation <br />in Adams County. This letter is intended to serve as a Technical <br />Revision to change the. method of mining from a "wet mining <br />operation" to a "dry mining operation" with "dewatering". This will <br />allow us to optimize gravel extraction from the site and increase <br />the life of the mine. <br />This has come about as a result of many outside influences <br />that include dewatering at adjoining mining operations, investiga- <br />tion of additional gravel lying under a layer of mud in the lake <br />bottom and the reduced static water level as a result of adjoining <br />lake dewatering by Albert Frei and Sons, Inc., and Western Mobile, <br />Inc. er.:^inirg opera*_ions to the south of o~=r site. When Western <br />Mobile, Inc., began to dewater we saw the lake level stabilized <br />some 6 feet lower that originally planned, when Albert Frei and <br />Sons, Inc. began dewatering early this year the lake dropped <br />another 5 feet leaving approximately 14 feet of water in our <br />southern lake. This will increase the amount of vegetation area on <br />the site until their mining ends and the ground water stabilizes. <br />At which time the lake should return nearly to it's original level <br />as substrata gravel becomes saturated when offsite dewatering ends. <br />We have done a test dewatering along a section of the north <br />area to monitor the affects a dry mining operation would have on <br />the surrounding ground water table. According to our data we only <br />had to pump 4 feet from the excavation because of the elevation <br />change on the property and the dewatering activities up gradient <br />from our site. We also needed to determine if there was a lens of <br />gravel under a mud lens like what Western Mobile, Inc., found in <br />their pit. Our findings are inconclusive at this time but we feel <br />