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Greg Lewicki And Associates, PLLC <br /> 3375 NY. Powers Circle Phone: (720)842-5321 Fax(303)346-6934 <br /> Littleton,CO 80123 E-mail: info+u le"icki.biz <br /> January 28, 2020 <br /> Eric Scott <br /> Colorado Division of Reclamation, Mining, and Safety <br /> 1313 Sherman St, Rm 215 <br /> Denver, CO 80203 <br /> Asphalt Paving Co., Ralston Quarry M-1974-086 <br /> Technical Revision —Modifications to Slide Repair Designs and Plans <br /> Mr. Scott: <br /> Asphalt Paving Co.,the permittee of the Ralston Quarry, is submitting this technical revision to <br /> incorporate a modified plan to repair the slide area west of the quarry. Following geologic <br /> investigation of the slide area, it was determined that the extent of excavation required to <br /> implement the approved repair plan would create undesirable conditions. <br /> Mainly, the depth of excavation necessary would make the slope susceptible to sliding. <br /> Construction safety was brought into question. There were concerns that the excavated slope for <br /> some buttress areas could slide down onto equipment during construction. The second <br /> undesirable condition was that the deeper the excavation went for buttress construction, the <br /> larger the horizontal disturbance needed. APC determined that it was better to re-evaluate the <br /> buttress designs and seek an effective, but less disturbance intensive, solution than to continue <br /> with the designs as they were. <br /> This technical revision contains those new designs and revised slope stability analysis that <br /> demonstrates their effectiveness. <br /> 1. New Slide Repair Designs <br /> The slide area at the Ralston Quarry has been divided into five zones in terms of repair designs. <br /> Each zone was evaluated to determine if a revised slope stability plan was needed following the <br /> geologic investigations in 2019. Ground Engineering evaluated each of the zones and their slope <br /> stability needs in a report that is attached. This report reiterates the previous Ground Engineering <br /> report from January 2019 as well as adding new information from additional data gathering and <br /> analysis. <br /> The primary effect of the analysis conducted by Ground Engineering was to improve the slope <br /> stability designs in the southern half of Zone 3, shown on the maps and reports as Zone 3A and <br /> to better define the position of subsurface pipes and the extent of earthwork needed in Zone 4. <br /> Ralston Quarry Slide Repair <br /> (:n�1 enir4 and 1z,uonlr.,1'I I <br /> January 2020 1 <br />