Laserfiche WebLink
h <br /> <br />' liability for damage that may occur at Cedar Heights Drive. <br />The 54" culvert was installed as per the Drainage Master Plan. The __ <br />1 reason for installation of a 30" outlet is completely unknown. Given the <br />possibility of larger boulders to clog the culvert, this is not a very safe <br />system and is likely the source of some of the flooding the Cedar Heil;hts <br />entrance has experienced. The 24" cross culvert near the 54" was ll)cely <br />' installed as a matter of necessity by Cedar Heights when the CE~dar <br />Heights entrance feature was constructed. Prior to that construction <br />runoff continued on the North side of the access road through the <br />' intersection and Into the major drainage. The Master Plan appare~ltly <br />considered this a minor culvert and it was not shown. <br />Regarding the impact of installation of a 24" culvert at HR-6 on the <br />' 54" system downstream, we would offer the following comments. There <br />has been a criteria upgrade (October 1987) since the original system de,~ign <br />and installation. 1`he CAP has included hydrologic analysts using the new <br />' criteria which, as a matter oP practicality, has resulted in a 30% to 40% <br />upsizing of all drainage facilities. The 54" system (or 30" below) h;is a <br />mayor hydrologic problem further compounded by an apparent lacy of <br />' maintenance. The new criteria would only further quantify this problem. <br />Any analysis would be difficult and theoretical at best. The key Issue is <br />that installation of a 24" culvert at HR-6 will significantly reduce flows <br />currently reaching the 54" system. SL is the Operator's opinion that any <br />' further analysis upgrade of the 54" system and/or the 24" system in Cedar <br />Heights Drive East is totally the responsibility of others. <br />' ITEM NO. 12 RESPONSE: The inundation area has had a continually <br />smaller volume of water over the past 3 to 4 months that has been closely <br />monitored by the Operator. This is due to low precipitation, normal <br />evaporation, and a small amount of seepage all of which mill result iir an <br />' even smaller amount of water when work begins in late December. <br />The area contains a number of dead trees and shrubs all of which <br />' would make application of the recommended granular filter layer extremely <br />difficult. Consultation with the Geotechnical Engineer resulted in his <br />recommendation of not installing a granular layer because it would ha~/e a <br />' long term tendency to trap water causing possible instability. The <br />Operator proposes to Pill the area of inundation by dozing the existing <br />material at the toe of Area No. 1 Into the ponding area in a manner and <br />at a rate at which little or no water !s released. <br />' An alternative to pumping the water or installing a filter layer w~ruld <br />be the backfilling of the pond in mid-winter when most of the pond is <br />' frozen. Using this technique, when the ice melts next summer the water <br />would be released slowly and would contain little if any sediment. Plf~ase <br />note that this commonly occurs in natural situations in talus slopes at~ove <br />timberline. This Is the best explanation Por why many high mountain talus <br />' - slopes release large amounts of clean water throughout the summer. <br />5 <br />