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c~~oaa ~a~~~ _ III IIIIIIIIIIIIIIII ~ ~__ ~ ~. <br />1254 Bear Mountain Court <br />Bould Co nr 80303 <br />ecember 9, 1982 <br />Ms. Connie Albrecht <br />Friends of the Earth <br />530 Main Street <br />Grand Junction, Colorado 81501 <br />Dear Connie, <br />I have completed my review of the Exxon Colony Interim Site Plan as <br />you requested and have prepared the following comments. <br />" 1) The philosophy expressed by Exxon to attempt to control erosion <br />and sedimentation at the source as opposed to treating the problem after it <br />has occurred, is a sound one. Temporary use of sediment ponds as Exxon has <br />proposed, is a reasonable approach to unavoidable sedimentation problems <br />that occur when such a large area is disturbed for construction activity. <br />~2) The discussion regarding the development of the appropriate curve <br />numbers to determine runoff rates from the site is reasonably sound. The <br />curve number method is commonly used in cases similar to this, and there are <br />no apparent flaws in application of the method in this case. Amore <br />authoritative review could be made by considering the cited studies by <br />Metcalf and Eddy (Dec. 1975) and PRC Engineering Consultants, but such an <br />analysis would not likely result in a significantly different result anyway. <br />/ 3) The professional judgment exercised in the calculation of sedi- <br />ment yield estimates is also reasonable. Although these estimates play an <br />important role in the design of the sediment ponds, as a practical matter, <br />~ the maintenance they receive is just as important or more important with <br />respect to their effectiveness. Since they are only designed for a ten year, <br />24 hour storm, any storm larger than this can be expected to exceed their <br />capacity and result in damage to the ponds and downstream. Proper main- <br />tenance is essential if adequate resource protection is to be assured. <br />Efforts made so far would indicate that Exxon is ex sting a goo aith <br />effort to properly maintain the ponds. It should be noted that these ponds <br />are considered temporary and do not constitute the permanent reclamation <br />solution for .the areas. <br />4)) The <br />must <br />be made ezpeditiousl Construction is already underway on the low flc <br />rversion system designed to protect the roadway bench alpng the Gulch. <br />.`\// <br />