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~t~ City of <br />1l~ Thornton <br />Infrastructure Maintenance Center lnfrastrurture Department <br />12450 Washington Street 720-977-6200 <br />Thornton; CO 80241-2405 SAX 720-977-6,202 <br />~vww.citydithornton. net <br />CERTIFIED MAIL -RETURN RECEIPT REQUESTED <br />(Article No. 7005 1160 0004 8489 5606) <br />February 25, 2008 <br />Mr. David A. Bird <br />Environmental Protection Specialist <br />Division of Mining Reclamation and Safety <br />1313 Sherman St., Room 215 <br />-Denver, CO 80203 - <br />~~ <br />FED <br />Oivisia 2 ~ZOQB <br />Mi~in9 ~~~ ~ef~p Pl~ry <br />~ ' <br />RE: Albert Frei and Sons, Inc., Priola Pit, File No. M-2007-087 Application for <br />Reclamation Permit <br />Dear Mr. Bird: <br />The purpose of this letter is to present a summary of items that concern the City of <br />Thornton (City) related to the proposed mining and reclamation operation at Priola Pit <br />(Pit) located in the northeast quarter of the northwest quarter of Section 31, <br />Township 2 south, Range 67 west. <br />The City has a major raw water reservoir immediately adjacent to the proposed Priola <br />Pit. This municipal water supply reservoir provides water to a major part of the City. <br />This reservoir includes the following elements that could be impacted by the proposed <br />project: <br />• Raw water storage reservoir <br />• Perimeter embankment dam <br />• Soil-bentonite cutoff wall below the dam <br />• Concrete surface water diversion ditch <br />• Groundwater drain (horizontal drain permit No. 63647-F) <br />Following is a summary of the potential adverse impacts of the Pit to the City's <br />infrastructure and water supply: <br />• According to Rule 5.10.1.2 of Rules and Regulations for Dam Safety and Dam <br />Construction, of the Colorado Division of Water Resources "Borrow area shall <br />be located at least 200 feet from the toe of the dam." The excavation for the Pit <br />is within 200 feet of the toe of the dam and could impact the stability and/or <br />foundation seepage. <br />• It is unclear in the permit application if the Pit will be dewatered during mining. <br />If the Pit is dewatered during mining, the dewatering will have severe impacts <br />S:\ID1En8ineering\Engineera\morenolprojeda\Priola Plt\022208 Priola mining rademation permit -COT commenta.doc <br />