2007-03-16_REVISION - M1986079 - Laserfiche WebLink

Home Browse Search

LAFARGE NORTH AMERICA AGGREGATES, CONCRETE & ASPHALT Deb Gonima, Division of Reclamation, Mining and Safety, 1313 Sherman Street, Room 215, Denver, Colorado 80203 ~~ ~~ J Pif ~ ~ 6 ~~ Di~d::io,~o~ ._, d~ fviinin R ' '~=tion. S and Sm[sy March 13, 2007 Re: Adequacy Review of Permit Amendment (AMl) M&G Piil M-1986-079) Response `/ Dear Ms. Gonima, Chris Rowe requested clazification of several items in his Adequacy Review letter dated 1/22/07. I understand that Mr. Rowe is no longer with the DRMS, but that you are now the contact for this case. If this is incorrect, I would appreciate it if you would forward this letter to the correct person and have them contact me. The following are Lafazge responses to Mr. Rowe's questions: I . The post reclamation stormwater detention pond has been designed for and is intended to detain the runoff from the Pollyanna Mann Marital Trust property and from the Dunes Subdivision. The detention pond will ultimately discharge to the South Platte from an existing outlet in the northwest corner of the property. A stormwater discharge permit has been applied for and a copy of the application is enclosed for your files. 2. The stormwater detention pond is shown on the proposed reclamation plan graphic. It slopes as a channel from the southwest along the west side of the property to the broader detention pond at the north. The low point of the detention pond will be at approximately 5020.65 in elevation. The dischazge pipe is an existing 24x36" elliptical storm sewer pipe in a 2' deep box culvert installed by the Colorado Department of Transportation as part of improvements to 120`h Avenue. 3. There is no data available from the M&G Pit with which to establish the historic groundwater level. There is, however, an existing Denver Water Boazd French drain system across Old Brighton Road immediately to the west of and pazallel to the M&G Pit. This drain system as a low point elevation of 5016.8. Extrapolating from this for the M&G Pit, 100' to the east, the low point of the M&G Pit detention pond will be approximately 4' above the low point of the French drain system, the presumed maximum historic groundwater level for this area. (This is presumed to be the maximum historic groundwater level because the drain system would have been designed with a low point at or above groundwater level, otherwise the groundwater would flood the system and render it nonfunctional). LAFARGE WEST, INC. 10170 Church Ranch Way, Westminster, CO 80021 Office: (303) 657-4000 Fax: (303) 657-4037