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• Above the excavation to bedrock the effects of weathering left 2 to 5 feet of clayey, soft <br />material in the location of the underdrain. To eliminate the chance of this softer material <br />pumping up into the underdrain when loaded with additional fill, a key cut to bedrock was cut <br />from the toe area excavation to the head of the underdrain. The key cut also provided a physical <br />barrier to control construction operations and ensure the controlled portion of the underdrain <br />would remain intact. The construction of the key cut can be seen in photograph 15. The <br />completed key cut tieing into the toe area excavation can be seen above and in front of the <br />pickup truck in photograph 16. <br />The topsoil preparation and foundation preparation for the controlled underdrain was <br />completed the last week of September 1992. <br />Professional Engineer's Certification for 1) removal of topsoil and organic material and <br />2) verification of bedrock follows. <br />C~ <br />• Section 1 -page 2 <br />