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_ _ _ ___ _ _ _ TR9PPCR F~IPII~~ IBC. <br />d- <br />i'~ <br />I, James M. Mat[ern, a Registered Professional Engineer in the State of <br />Colorado, in accordance with~2CCR407-2, Section 4.05.6(7), do certify [hat <br />Johnson Gulch dams 7A, 9, and 10 were constructed under my direct supervision. <br />Dams 7A and 9 were constructed in early 1985 (February-April) and enlarged <br />during pond cleaning operations in July. Dam 10 was constructed during the <br />summer of 1985 (August-September). Dams 7A and 9 were surveyed for capacity <br />determination in January, 1986. Dam 10 was surveyed in September, 1985. <br />Stage storage relationships, spillway elevations and hydrographs for a <br />10-year, 24-hour event and a 25-year, 24-hour event are shown in the attached <br />SEDIMOT II output. <br />During construction the dams were visually inspected daily to insure compli- <br />ance with prudent state-of-the-art construction methods. Compaction was <br />accomplished by laying fill in thin horizontal layers and compacting with a <br />vibratory roller compactor and dozers and/or scrapers. Standard Proctor den- <br />sities were determined in our lab using methods outlined in AASHO T99-61. <br />Percent compaction was monitored using a nuclear density probe until densities <br />were sufficiently high to insure stability. <br />~~,5 M:. MATT. <br />1Q~~~~GtStERFp ,per <br />~r <br />' e a 20537 w' ~ <br />~~O Wi <br />2, <br />F ~ • O <br />.. OF ~ C O~~ <br />J2~L"f/ jb <br />]/23/86 <br />P.O. Box 187 <br />a~ - <br />Ja s M. Mattern, 0 PE 205 <br />/~73~8~ <br />Date <br />Craig, Colorado 87626 <br />REVISED FFf~ 1 3 '87 <br />(303) 624.4401 <br />