PERMFILE61992 - Laserfiche WebLink

Home Browse Search

- I ~ ~ 1 _ Brighton Water Storage Project ' - Slope StahiliTy Calculations Adams County, Colorado ' GROUND completed a subsurface explorafion program to-provide preliminary geotechnical information regarding for design and construction of the proposed 124`s Estates, residential ' development ai the site. Our findings and conclusions were summarized in GROUND'S report, Subsurface Exploration Program, Findings and Conclusions, Subsurface Exploration Program,. • 124"' Estates, Brighton; Colorado, Job No. 01-0022, prepared for Dacoa, Inc., dated April 2, ' ,2001, Reference is made to our April 2, .2001,, report for a description, of the site surface conditions and subsurface conditions below the southwestern and central portions of the quarry ,floor. - _ ~ , '-- The proposed site was occupied at the time of our work largely by an abandoned, rhomb-shaped, ' aggregate quarry partially filled with water. The site is depicted on Figure 1, attached. The quarry excavation apparently has been partially tiackfilled with soils from several sources. The mass of fill material extended into the quarry from the southwest corner. Approximately 50 percent of the quarry bottom area was covered with water forming a U-shaped lake. Based on an undated A.L.T.A./,AGSM Land Title'Plan provided by Jehn & Associates, Inc., the existing quarry slopes descended about 15 to 20 feet from the adjacent teaain to the water level ' and then an unl~lown depth below the water. Existing slope angles ranged from about 2%:1 to 3'/za (horizontal :vertical) We understand that present plans call for additional aggregate to be ' excavated from the quarry walls and floor to enlarge the potential reservoir. Claystone material to be excavated from beneath the aggregate will be placed as a clay liner on the reservoir walls. ' The final slope configuration will be-achieved by placement of available, `miscellaneous fill' materials. Based on a undated plan prepared as_an exhibit by Jehn & Associates, Inc., and a ' preliminary cross section sketch prepared by Leonard Rice Engineers, Inc., the permanent slopes descending into the proposed reservoir .will be constructed at an angle of 2%a:l (horizontal ' vertical) and be approximately 44 feet in height. Prior to placement of the `miscellaneous fill' at ' ,. the permanent slope angle, the excavation backcut exposing the alluvia] sand and grave] and the - underlying,' predominantly claystone bedrock will be lined with excavated claystone material. ' We understand that the proposed liner will be approximately 15 feet in horizontal thickness, extending from the top-of--slope io the reservoir floor. Data from GROUND'S subsurface ' exploration program for this study (see below) and as presented irf our April 2, 2001, report, the reservoir floor at the proposed depths of excavation will expose the local bedrock consisting primarily claystones. ,' Job No. 02-0065 _ Ground Engineering Coosul[ants, Inc. Page 2