2002-09-27_REVISION - M1977436 - Laserfiche WebLink

Home Browse Search

p~fea~e - ~~®~~, inc. July l 8, 2002 Mr. Besharah Najjaz Floodplain Administrator Adams County 4955 East 7ih Avenue Commerce City, Colorado 80022-1551 RE: ,Aggregate Industries' Brighton Mine Floodplain Use Permit, Outstanding Issues from the Urban Drainage & Flood Control District, June 2002 Dear Beshazah: May 22, 2002 you and I met with several others at the Brighton Mine Site to discuss outstanding issues regarding the Floodplain Use Permit for this property. In attendance were Bryan Koh]enberg and Steve Materkowski from the Urban Drainage & Flood Control District (Urban Drainage), and Bill Brown and Tom Mau] from Aggregate Industries. The discussion centered specifically around four offsite flow areas that discharge onto the Brighton Property. In previous submittals, grouted boulder rundown channels were designed to carry these offsite tributary flows into the mined cells. In addition, Urban Drainage has requested that these flows _ be controlled from a point where they cross onto the Aggregate Industries property to the edge of the mining cell and rundown channel. The concern is preventing erosion and/or head cutting that could damage the Brantner Ditch and/or Riverdale Road to the west. Discussion during the site visit led to the following consensus. Direct Flow Area (DFA) 4 crosses under Brantner Ditch through a large dual box culvert. The channel iS well defined for several hundred feet downstream. This channel will be directed into the south mining cell on the west side, and a grouted boulder rundown channel into the pit will be provided. DFA 5 currently crosses Riverdale Road in three locations and empties into Brantner Ditch. For purposes of design, it is assumed that the ditch is flowing full when these offsite flows enter, and they will overtop directly onto the property to the east. Since it is unclear how or if these flows will concentrate before reaching the mine site, the lateral berm protection between the south and central mining cells will be extended around to the north to provide protection from sheet flow into the pit. 1499 West t20'"Avenue, Suite 2W _ - ~ -- Sla ; 3oeiny Dnv::, :r. u:;:~ ~ ~Ft% Denver, Coloradc 89234-2728 vrNw.appieyaleyroup corn LavelunJ. •.~atornrn~ 9o!;:A E'i ,b (303i 452-66 i . • Fa: (363) 452-2759 (97C; 461-9894 • Faz (97rq n i:i-'. is ;