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<br />November 12, 1981
<br />
<br />Further analysis was done at Ford StN'et to eX1I'line the extent of floodhlq
<br />for the 50-year event (O=8,OOOcfs). lJtilizing the s1l'lemethodology, a flciw
<br />split of 1,750 cfs "",ir flo~' and 6,250 cfs bridge flow was cal cul ated. We
<br />est imate that approximately 1,250 cfs Wlul d return to the cllannel in th~
<br />area do~stre(lfJ1 of Ford Street and 500 cfs Io{)uld travel to the south of the
<br />-Coors we 11 ness Center and through the brewery p~rki ng lot at a dp.pth of 1 P...
<br />thanO.Sfoot.
<br />
<br />"... Don ~ ld !\bore
<br />P1 ~nning Oepartment
<br />City of Golden
<br />1911lOth5treet
<br />Go lden, Color ~do 80401
<br />
<br />Washington Aven~e Area
<br />Using the 100-year water surface of 5,657.8 olc~lated at Ford Street, a
<br />backwater roo was performed to determine the water s~rface elevat 10n
<br />immediately downstre(l(rl of the >I~shington Avenue bridge. This 1'1 evation of
<br />5,661.4 was then used as the tail ~'ater elevation for h~nd calc~l aUons at
<br />Wash i ngton A~ enue. Rat i ng cur~es for we i r fl ow over the roadway and flow
<br />thrOugh the bridge were developed. A flow sp11t of 7,870cfs through the
<br />bridge and 4,550 cfs weir flow at elevation 5,665.07 resulted, which
<br />c~pares favorably with the FHAD report elevation of 5,665.05.
<br />
<br />De~r W. i'tlore:
<br />
<br />The existing bridge structures at Ford Street and Washington Aye nuelackthe
<br />capacity to convey major flood flo",s s~ch as the 50-yeu and 100.year
<br />floods. Consequently, d~ring a major flood event, large flo",s wi 11 overtop
<br />the ex ist ing roadways and spre~d out into a wide fl oodpl ain area. For
<br />eX<'I"lple, at Washington Avenue the 100-year flood will overtop the roa::fata
<br />depth of 2 feet, IJpstre/lll of Washington Avenue, the IOO-year floodplain
<br />spreads out to an average width of 600 feet, ca~s1ng d<'l"lages in excess of Sl
<br />million.
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<br />We are current 1 y e~ pl ori ng altern at iv es ..;, i ch >OJ ul d great ly reduce the flood
<br />d(l'1lage potential in the Clty of Golden. Tnese include improv~ents at the
<br />Ford Street and "ashington Aven~e bridges, and increasing the conveyance
<br />capacity of the Cl ear Creek channel. Since the are~s ~pstre(lfJ1 of "ashington
<br />Avenue along the north side of Clear Creekha',e been de',eloped, the only
<br />areas a~ ail ab 1 e for econom1ca I flood re1 jef alternat i ves are those wh i c h
<br />abut the south side, and the Evans tract is the largest of these areas. We
<br />stronglyrecornmend that the CHygain control of the Evans tract and other
<br />1 and wrli ch ~buts C1 ear Cr eek to pro~ ide the wori:1 ng space to enhance the
<br />flood conveyance capacity through Golden. The potential benefit deriv!'d
<br />from such action is not only flood d.JTIage rel ief, but al so l'lult1.p\lrlX'l~" IJ""
<br />of t~e floodpl ain area as a pedestrian and bicyc Ie transportation 1 ink and a
<br />pass ive recreat ion ~rea.
<br />
<br />VerytrulYYJurs,
<br />
<br />I-IRIGHT~i'\;:lAUGH~IN ENr,I~EERS
<br />
<br />JMP/jo
<br />
<br />(8l2~037 . CICIO)
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<br />If yo~ need further informat ion please caTl.
<br />
<br />VerytrulYYO\lrs.
<br />
<br />WRIGHT -"tLAUG~LlN ENGINEERS
<br />
<br />By 1I1/f,--t11##Lt-
<br />0/\ la1l C T,fsf.:art
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<br />W:T:cr
<br />812-037.0GA
<br />NOVIA
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