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<br />0021li9 <br /> <br />" <br /> <br />2,2,5 Levee Protecting East Alamosa <br /> <br />Concern: <br /> <br />On June 20, one week after the passage of the flood <br />peak, seepage of groundwater through the levees had reached a <br />depth of 2 1/2 feet in some areas of unincorporated East <br />Alamosa. Several residential structures and one business were <br />inundated. County crews stockpiled sand while residents and <br />volunteers sandbagged the flooded structures and the streets. <br />State and local officials were requested to evaluate the <br />situation and pumping was reconwended as a means to reduce the <br />water level. Pumping continued for a 24-hour period and over 2 <br />million gallons of water were returned to the river. The water <br />,level in an old slough was reduced by more than one foot. <br />Although the flood fight is over, groudwater seepage and the <br />structural integrity of the levee is a concern. <br /> <br />i.1 <br /> <br />Findings: <br /> <br />Examination of the north bank levee revealed a weak spot <br />at the point where it connects to the railroad embankment. The <br />weakness extends approximately 70 feet upstream of the railroad <br />right of way line in the area where the pumping operations took <br />place. A culvert was reported to have at one ti,me extended <br />under the levee but it is not known,' if it is still there. A <br />hole in the top of levee was visible during the inspection, <br />Root growth from three trees and dense vegetation on the <br />riverside of the levee may contribute to the problem. <br /> <br />Approximately 1533 cubic yards of material would have <br />to be excavated and replaced in 6-inch lifts with compacted <br />material to repair the levee. The trees and vegetation should <br />be removed and about 265 cubic yards of riprap placed on the <br />levee to prevent erosion, <br /> <br />Pumping of the slough behind the levee appears to be the <br />most cost effective solution to the flooding and high <br />groundwater problems in East Alamosa. A permanent wet well, <br />intended to be used by the city or county during flood fight <br />operations, could be constructed behind the levee. The pump <br />could be rented as needed. Approximately 178 cubic yards of <br />compacted fill, a manhole, and 550 feet of perforated pipe laid <br />in a gravel bed would be required to constructe the wet well. <br /> <br />81 <br /> <br />t <br />t <br />i <br />I <br />I <br />I <br />I <br />