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Mvt'1 - Bi,).... -- T~ . ~i-v/JW--' -~ 20A,_ 'if .... .. F'ff. Aurora Dina Bunn, Aurora Reporter - 892-2562 Dam inadequate i,n worst case, engineers say Corps to begin study for improvements at Cherry Creek reservoir 8I))ina Bull~_______ Rocky Mountain News Staff Wn'ter AURORA - Cherry Creek Dam would be inadequate in a worst- case flood, but don't break out the sandbags just yet. "We consider this a problem, but it does not mean there is an immediate danger to people," s~id Bill Miller, a project manager WIth the Army Corps of Engineers at -~the.regional office in Omaha~ . The corps expects this fall to begin a three-year study of options for imorovinlI the dam. after hav- ing revised its estimates of the dam's capacity to withstand a worst -case flood. Among the options are raising the crest of the dam 3 to 19 feet, widening the spillway and adding a side-channel spillway at the south- western abutment to the dam. The 3-mile~long dam was built in 1950 for $15 million to control the flow of Cherry Creek and keep the creek within its channel. Currently, the dam's spillway is capable of handling 63% of water from a catastrophic flood, accord- ing to a 1993 hydrological report. Engineers derived that percent- age from updatedinforJl1<!tion frQm the National Weather Service as Rocky Mountain News Tues., June 25,1996 Flood figures based on rain estimat~s DAM from 20A The corps ,:!ses that informat~n to factor the Impact on a dam and its ability to let excess water pass through, Curran said. A possible worst-cas~ rain- storm or maximum probable pre- cipitation, could be 10 inch_es of rain in six hours, said LaB Tun- nell a hydrologist with the weath- er service in Denver. But such an event would have a 1% chance of happening in any given year. "Federal regulations require that dams, their spillways, have to be able to accommodate what they call a 100-year flood," Tunnell said. "Our chances of rain to pro- duce a flood in Cherry Creek is higher than it used to be." . The first year of the study could cost up to $325,000 and would begin after September. well as newer design standards for dams. "Over time we get more data. And if we designed a dam today, we would use current criteria. That's how we analyze a project for dam safety," said Tom Curran, a corps engineer in Omaha. The corps figures the maximum probable flood from the w~ather service's figures for the maxImum .~ probable precipitation. The figures are determined by estimating the greatest depth of precipitation for a given duration over a particular location at a cer- tain time of the year, said Louis Schreiner, a hydrometeorologist in Denver.-=-=-' The 3-mile-long Cherry Creek Dam was built in 1950 for $15 million to keep the waterway within its See DAM on 21A h-:>nl.-c i:=vnortc nnlA' c::>" tho rl::>1'Yl 'c cnilllA'::>" "",.Irl h::>nrllo "nh, ~~ot. "f tho I^,,,,tor in '" "",t",ctr"nhi" fl""r/ Steve GroerlRocky Mountain News