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1_1 Zone 1 <br /> Zone 1 consists of the material pile built from slide material that is located south of the main <br /> drainage in this area. Its location can be seen on the attached Map F-2. No changes have been <br /> made to this zone's construction or maintenance plans. Ground Engineering's revised report <br /> reflects the same recommendations as the original 2019 report. <br /> 1_2 Zone 2 <br /> Zone 2 is the southernmost area along the western facing slope of the quarry. It can be seen on <br /> Map F-2. This zone consists mostly of long revegetated fill material and has not seen any slope <br /> stability issues at any point in its existence. Additional fill that has occurred along the toe of the <br /> slope since Ground Engineering's 2019 report has led to an increase in the stability of that slope <br /> from 1.25 to 1.3. <br /> 1_3 Zone 3 <br /> Zone 3 consists of the 2018 slide and surrounding ground. This area was evaluated in detail by <br /> Ground Engineering to determine the most effective and efficient way to accomplish slope <br /> stability without construction safety risk or unnecessary ground disturbance. Cross sections were <br /> developed perpendicular to the slope and different designs were evaluated along these cross <br /> sections in an iterative process to determine the appropriate repair design. Ground Engineering's <br /> attached report shows the slope stability that is achieved with these designs. Map F-2 shows the <br /> existing and final slope cross sections. <br /> Portions of this zone will require only regrading to reach stable slopes. The areas around the <br /> 2018 slide will have buttresses and subsurface drainage installed to achieve stable slopes, in <br /> accordance with the existing approved plan. The net effect of additional test pits and slope <br /> evaluation has been to better define the extent to which buttresses and subsurface drains will be <br /> needed to achieve stable slopes in the area <br /> Zone 3A will not require the installation of subsurface drains, as regrading of this section of <br /> slope will be sufficient to achieve a safety factor of 1.3. Two cross sections through this area <br /> were analyzed and can be seen on Map F-2. <br /> Zone 3B will see the installation of buttresses and subsurface drainage as previously approved in <br /> order to meet the safety factor of 1.3. <br /> 1_4 Zone 4 <br /> Zone 4 consists of areas north of the 2018 slide that contain a previous, smaller slide area. This <br /> area was evaluated in detail by Ground Engineering to determine the most effective and efficient <br /> way to accomplish slope stability without construction safety risk or unnecessary ground <br /> disturbance. Cross sections (X 1-X 1' and X2-X2' on Map F-2) were developed perpendicular to <br /> the slope and different designs were evaluated along these cross sections in an iterative process <br /> to determine the appropriate repair design. Ground Engineering's attached report shows the slope <br /> stability that is achieved with these designs is 1.4 and 1.2. Map F-2 shows the existing and final <br /> slope cross sections. <br /> Subsurface drainage systems will be installed in this zone. There arrangement can be seen on <br /> Map F-2. <br /> Ralston Quarry Slide Repair <br /> l.n•K!A•hcI,and 1s`a 1,-NI <br /> January 2020 2 <br />