Laserfiche WebLink
<br /> <br />ADDENDUM to the DRAINAGE REPORT <br />RAILHEAD GRAVEL PIT <br />This Addendum is being prepared in response to Review Comments made to the <br />Petitioner, United Companies of Mesa County, during the review process of this submittal. <br />It is being furnished to answer comments made by the State of Colorado Department of <br />Natural Resources and by Mesa County Engineering Department. Comments made during <br />this review centered on concerns on how drainage would be handled during and after the <br />mining operation. To help illustrate drainage plans, two attachments, A & B, have been <br />prepared to identify proposed details. <br />Existing drainage structures at the site currently consist of five feet wide concrete V-pans <br />on each side of a 41 foot wide asphalt roadway, which is Railhead Avenue. The street <br />drains to a low point and all runoff then discharges on the surface into the 44 foot wide <br />Drainage Easement as shown on the Final Plat. Improvements within this easement consist <br />entirely of a asphalt Swale, that being 44 feet wide. Discharge in this easement travels in <br />a general direction north to south towards the river to undeveloped areas of the <br />subdivision. <br />It is our understanding that for approximately 70% of the mining operation these existing <br />drainage structures will be left intact and will be utilized in their current form. The only <br />change will be the removal of the existing railroad spur, and bridge structure, which <br />currently crosses over the easement, however, this will have no effect on how the drainage <br />will work. I^ discussions with United Companies, the existing asphalt Swale will be <br />removed only when the mining operation reaches this general location. It will then be <br />replaced with a earthen Swale that will function in the same manner as the asphalt Swale <br />currently does, discharging in the same location. Once the mining operation reaches this <br />location completely, the earthen Swale will be removed along with the surrounding <br />overburden, and at that point all runoff will then discharge into the gravel pit. No storm <br />runoff will then be directly discharged from the site. Any discharge from the pit from this <br />point on will fall under the regulations of the Discharge Permit also being applied for <br />United Companies. This drainage plan for the operation of the gravel pit is shown on <br />Attachment A. <br />As stated in the Drainage Report and shown on the Reclamation Plan, submitted by <br />United Companies, most of this site will ultimately become a lake that will have several <br />uses. One of these uses is that it will become a retention pond for the on-site drainage. <br />Information supplied to Banner shows that the normal water table is situated approximately <br />12 feet below existing grade. Therefore, after the mining operation and reclamation work <br />is complete, it is anticipated that the lake level will be approximately 12 feet below finish <br />grade. Attachment B shows details of proposed drainage improvements to be constructed <br />for use once the mining operation is completed. La essence what is being proposed is to <br />replace the surface discharge from Railhead Avenue with a storm inlet located at the <br />existing low point in the roadway and then pipe it the short distance to the new lake. This <br />will serve to help divide and disassociate the street from the lake, for safety purposes. <br />