Laserfiche WebLink
COLORADO LEGACY LAND <br /> TECHNI $U Y TABLE <br /> COMMENT NO. COMMENT RESPONSE TO COMMENT <br /> Drawing Sheet 2. A)The depth of bedrock is not known. Table 2 of Sheet 2 specifies <br /> The HP Storm Trench Installation Detail(combined with 1 to 4 feet of cover for the pipeline. Depth to bedrock will be <br /> information from the other drawings)suggests the invert of the assessed during excavation. If shallow bedrock is encountered <br /> installation trench could be more than seven feet below the excavated alluvial soils can be used as fil to meet cover thickness <br /> existing grade(6"bedding,30'pipe ID plus—2"wall thickness, requirements. <br /> and 48"final backfill;or approximately 88"or 7.33 feet). This <br /> poses several questions related to constructability and B)No blasting will occur. The design basis has been modified and <br /> maintaining the isolation of the waste rock protected by the the intent is to keep 4 feet of cover over the pipe to allow for Heavy <br /> vegetated cover: Construction loading(Table 2 of Sheet 2)over the pipe. <br /> 4 <br /> a) What is the depth to bedrock along the proposed C)There will be excavation into the waste rock but only under the <br /> alignment? access road. <br /> b) If it is less than 7.33 feet,will blasting be required? <br /> c) Will the excavation extend into waste rock? D) During construction,the trench will only be open long enough <br /> d) d.How will the trench be maintained during and after to install one section of pipe and then be backfilled. After <br /> construction to prevent water seepage from entering the construction,the NWRP access road will be returned to its existing <br /> waste rock? condition. Runoff reaching the access road will drain along road <br /> toward Ralston Creek. The access road will be graded to keep flow <br /> on the north side of the road;against the native slope. <br /> Sheets 3 and 4. All horizontal bends have been removed from the design using an <br /> There are several horizontal and vertical bends in the proposed additional manhole and relocating the previous two manhole <br /> alignment. Experience suggests significant horizontal bends are locations. The trash rack at the headwall will prevent the majority <br /> ideal locations for tree branches to become lodged in the pipe. of tree branches and debris from entering the system. Any debris <br /> Negative changes in pipe gradients(e.g.,—STA 1+90,Sheet 4 that passes the trash rack is likely to become lodged in a manhole, <br /> from 24.2%to 5.0%)are ideal locations for sediment to drop out where they can easily be removed. <br /> and lead to plugging. Sharp horizontal bends can also lead to <br /> 5 sediment deposition and potential plugging. Given these All the vertical bends have been removed except for the final <br /> conditions,30-inch diameter pipe and only two manholes, vertical bend at the bottom of the access road. <br /> roughly 500 feet apart;how will the pipe be inspected and <br /> maintained before and after closure? The additional manhole makes the longest pipe run 301 feet. <br /> Inspection will require visually checking the trash rack for debris <br /> and each manhole. The bottom manhole will be the first location <br /> sediment would ever collect due to the lower slopes of the pipe. A <br /> CCTV (Closed Circuit Television) inspection could easily inspect <br /> the entire system. <br /> PAGE 3 OF 7 <br />