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I I I I I I I I I I I I I I I I I I I I From: wade.thornburg@Wgint.com [mailto:wade.thornburq@Wqint.com] Sent: Tuesday, September 25, 2001 1:53 PM To: Carroll, Charlie Subject: Shell Comments on the Maul Reservoir Proposal 5. The proposed reservoir footprint would include more acreage than currently mapped by the 100-year floodplain. Thercfore, land use would be limited on a greater area. 6. Designers should note that the channel below the current dam has been plugged so that outlet flows are div'erted into the original channel. Shell has plans to fill the entire length of straightened channel if the current diverted flows prove to be beneficial to groundwater treatment and habitat Shell comments on the Maul Reservoir proposal: 7. Much of the area east of Peoria Street to be effected by the proposed reservoir is currently dominated by weedy vegetation. Construction of the reservoir would provide the opportunity to improve the appearance and habitat of the area. 1. Two monitoring wells in MfA's long-term groundwater monitoring program (wells 37074 and 37083) are located within or near the downstream toe of the proposed dam. They will need to be protected or replaced by the UDFCD. If the existing wells cannot be retained, they must be closed properly according to Colorado water well construction and abandonment regulations (2 CCR 402-2). Call if you have questions (303-853-3975). Thanks. 2. Five monitoring wells in RJ\1A's long-term groundwater monitoring program (37081, 37318, 37323, 37369, and 37389) are located within the arca of the '1 OO-year water surface. Their top of casing (TOC) elevations are lower than the maximum water surface elevation of 5138 ft.. The TOC elevations range from 5124.9 to 5129.6 ft. Consequently, it would not be practical to cxtcnd them above 5138 ft One of the wells (37369) would be inundated by the estimated water surface elevation associated with a lO-year storm event Water tight well seals should be provided by the UDFCD to prevcnt surface water from entcring the wells during storm events retained by the proposcd darn. RMA pcrsonnel will be responsible for installing the seals. All 5 wells have 4-inch diameter (ID) PVC casings. 3. Between 6 and 10 private water wells are located within the area of the I OO-year water surface. At least some of these wells still are uscd. Any remaining water wells should be located and their status evaluated. The wells should be scaled or closcd to prevent surface water from entering the wells during storm events. Of the six wells where infomlation is available, four are completed in the Arapahoe Formation, one is completed in the Denver Formation, and one is an alluvial well. Completion depths range from about 30 feet for the alluvial well to 575 feet for an ArapalJOc well. 4. The access lane off Peoria Street and a barn on the Shell property would be effected. Both would need to be relocated or demolished.