Laserfiche WebLink
<br />. <br /> <br />REMOVAL OF KELLY ROAD DAM <br /> <br />Removal of the dam would obviously eliminate the concern over <br /> <br />its safety and it would eliminate catastrophic effects that would <br /> <br /> <br />result from failure of the dam. However, removal of the dam <br /> <br /> <br />would increase the frequency of flooding downstream. Kelly Road <br /> <br /> <br />Dam provides about $l.7 million in average annual flood control <br /> <br /> <br />benefits. Removal of the dam is not considered an acceptable <br /> <br /> <br />course of action and should be considered as a last resort. <br /> <br />PROTECTION OF KELLY ROAD DAM EMBANKMENT <br /> <br /> <br />Blanketing the existing embankment with grouted riprap or <br /> <br /> <br />other means was considered. It was not, however, considered a <br /> <br /> <br />sound engineering plan because of lhe possibility of frost action <br /> <br />breaking the grouted protection. Also, it would not reduce the <br /> <br /> <br />potential for overtopping. Overtopping on an average of once in <br /> <br /> <br />25 years is unacceptable because of the high potential for damage <br /> <br /> <br />and loss of life in the densely populated area downstream from <br /> <br /> <br />the dam. <br /> <br />MODIFICATION OF KELLY ROAD DAM <br /> <br /> <br />Construction of a larger spillway and raising the existing <br /> <br /> <br />Kelly Road Dam embankment were evaluated. These modifications <br /> <br /> <br />would allow storage of floods up to the 50-year flood and for the <br /> <br /> <br />safe passage of all larger floods without danger of overtopping <br /> <br /> <br />and failure. Total costs would be about $6.2 million. Total <br /> <br /> <br />average annual benefits would be about $l.3 million and the <br /> <br />benefit-cost ratio would be 2.9. Average annual net benefits <br /> <br />would be $826,000. The flood plain downstream from the dam is <br /> <br /> <br />extensively developed for residential use. A spillway operating <br /> <br />frequency of once in 50 years is unacceptable because of the high <br /> <br />19 <br /> <br />. <br />