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II 11-2 channel bottom, and It Is to be used wh'~re the pre:sence of the raised con- crete erosion control would cause an in<:rease In tile flooded area during the des ign 100-year return frequency. liowever, eros ion wi I I cont inue for some time untIl the channel slope Is stabilized. The actual design of each type of check will probably vary with location and some variation will probably be desirable In order to determine the optImum design. There wi 11 also be some areas when, access fCII' ma Intenance wi I I be desirable. In addition, there will be more bridgE' crossings of Big Dry Creek between the arterials and collectors presently e"lstlng and shown on the drawings. As the area urbanizes and the demand for streets and for maintenance access increases, it was anticipated in thE' preparation of this report that both requirements wil I be compatible and that the mainten- ance access will be deve loped as the neE,d for it occurs. . There are several places throughout the study area where either embank- ment protection Is desIgnated or where an ellsernent for potential erosion should be acquired. The former most corrunon'ly OCC~I'S at streets such as U.S. 36 where concentrated portions of mad overflow could cause consider- able damage to the embankment and loss of the road" The embankment protec- tion could either be dumped rock rlprap of a good l,esthetic nature or broken concrete riprap which could be plantE,d over" The second require- ment for an erosion easement JOOst commonly occurs In the upper reaches of the basin where the flood plain narrows and both the continued low flow releases and Increased occurrences of high runoff due to Increased urbani- zation could cause a shift in the channel alignment, and therefore a shift in the flood plain. It would seem reasonable to wc'rk e,ut the easement acquisition with the prospective land developer, or' have the developer supply the appropriate embankment protect Ion whIch would alleviate the necessity for the easement. This reasoning Is compatible with the current regulations and the current practIces of the City ll,f \~estmlnster. .DRAW I NGS In Phase A It was reconvnended and accepted th,!lt the Union PacIfic Railroad embankment and culvert illl11edlately west of Colorado Boulevard be left In their present state, even though the embankment would be overtopped under full urbanizatIon for the 100-year design fr,equency storm. The hydro- logic effects of the pondlng behInd this embllnkmenl: are very profound to the property owners and public entities downstrellm of County Une Road In Weld County, In that the flood discharge Is reduced from 14.000 cfs to 2460 cfs. Sheets 2 through 5 show the recommended improvements in order that the flood hazard from embankment washout be minimized ,lnd the ful I benefit of the pondlng be realized. By retaining the emban~~nt, the County Line Road bridge need not be expanded In size for hydraulic ;-easons. It Is ant icl- pated that the bridge will be replaced with an Identical span when road re- quirements demand. As Is the case with o)ther brldges In the basin, some