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X-3 19. Infiltration test~ performed during Phase A Indicated an average in- filtration rate for existing conditions of Orle inch per hour; however, for design purposes under future development" an Infiltration rate of 0.75 Inches per hour was used. 20. The peak '"ate of runoff was determIned to var"y from 250 cfs to 14,000 cfs for the 100-year return frequency under full urbanization. 21. During Phase A, Mr. Ronald H. Strahle was retained to provide a legal opinion as to the I Iabll itles of each of the alternates considered. Alternates I and 2 have the least 1 iabil ity In that governmental en- tities are not required to construct facil itles to alleviate storm drainage problems, Alternate 3 has greater 1 iabll ity than Alternates I and 2 in that once facilities are constructed, the governmental entitles lIre then charged with responsibll ity to have designed them properly llnd to maintain them In proper working condition. Alternates 4 and 6 carry the greatest liability and the responsibility to maintain the existing channel Is not allevi,sted due to the construction of either of the alternates. Alternate 5 can be considered an Integral part of any of the preceding alternates. The 'liabilities associated with Alter- nate 5 are, governed by the same general prlndples as the previous alternates. 22. Design criteria were established for Big Dry Creek and reflect good des i gn prclct I ces for prev I ous I y accepte,d standards and new requ i re- ments due to the unique nature of "preventIve" storm draInage planning and aesthe,tlc water-related opportunities. Ilost important of the cri- ter I a is that re I ated to natura I channe 1 s as the des i gn app roach was one of flood plain zoning. Grass-lined artIficial channeis will be used where, channel modifications are necessar"y near brIdges, Trickle channels for 250 cfs will be provided In the artificial channels and they ~"ll be riprapped to provide channel stabll izatlon. 23. The report, at the concurrence of Adams County and WestmInster, does not cover spec If ic deta lIs on the use of the flood p I a in as parks and open space. 24. Provisions have been made for pedestrian pas!'age \~Ithout crossing over major streets from the County Line Road throughout the iength of Big Dry Creek up to Standley Lake. 25. The clear water releases from Standley Lake 1ll1d Gr"eat Western Reser- voir provide a unique opportunity roo h,sve a "I ive" meandering stream throughout much of the year In an area that Is rapidly urbanizing. 26. Gablon length of Big or concrete low flow erosion controls are shown throughout the of Big Dry Creek to prevent, present dCl\~nward-cutt i ng trends Dry Creek. (Sheets 7 and 2:q.