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depression, the accumulated runoff is allowed to infiltrate or is pumped to Outfall 006 within 72 <br /> hours. <br /> Drainage area 04 is the localized depression within the eastern portion of the south quarry. <br /> Runoff from this area collects within the depression and is allowed to infiltrate or is pumped to <br /> Outfall 006 within 72 hours. <br /> Drainage area 05 is Strain Gulch upstream of Site and is discussed in Section 2.1. <br /> Drainage area 06 consists of the north quarry and Reservoir Site 11. The north quarry has been <br /> partially reclaimed and revegetated, and runoff from drainage area 06 reports to Reservoir Site <br /> 11. As part of final reclamation activities, drainage channels will be installed to collect and convey <br /> surface runoff from the benches and highwalls to detention basins on Site, prior to discharge <br /> through an outfall. The analysis and design for the north quarry sediment basin will be <br /> completed at a later date. <br /> Drainage area 07 consists of the processing area, the upper portion of the main quarry haul <br /> road, and an undisturbed hillside to the south of the processing area. The runoff from this <br /> drainage area flows east through the existing sediment basin to Outfall 005. Outfall 005 <br /> discharges to an unnamed tributary of Turkey Creek. A recent stormwater evaluation was <br /> completed by Apex Companies, LLC (Apex) to assess detention pond sizing. It was determined <br /> that the sediment basin for Outfall 005 was undersized and did not meet Mile High Flood District <br /> (MHFD) Water Quality Control Volume (WQCV) criteria for storage volume or operation. Due to <br /> this shortcoming, Holcim recently installed an additional sediment basin in-line and upstream of <br /> the existing basin to meet MHFD criteria (Apex 2020). <br /> Drainage area 08 consists of the main quarry haul road below the sediment basin for Outfall 005 <br /> and undisturbed upslope areas along the main quarry haul road. Flow from the drainage area is <br /> routed to the sediment basin located at the base of the main quarry haul road near CO-8. The <br /> sediment basin discharges to Outfall 001 and flows into the roadside drainage channel along <br /> CO-8, which ultimately flows into an unnamed tributary of Turkey Creek. The sediment basin is <br /> of adequate size to meet MHFD WQCV (Apex 2020). <br /> Drainage area 09 is a small area at the base of the main quarry haul road, downstream of the <br /> sediment basin. Runoff from this small area reports to Outfall 004 and flows into the drainage <br /> channel along CO-8 that ultimately flows into Strain Gulch. <br /> The existing and proposed land uses for the drainage areas will primarily remain the same, as <br /> will off-site flow patterns and paths since the area to the west and upslope of the Site is in the <br /> Mount Falcon Open Space Park and is not expected to be developed. Drainage patterns will be <br /> modified by additional development within the south quarry, development of the west quarry, <br /> and the construction of additional drainage structures in the north quarry area as part of final <br /> reclamation, but the land uses will primarily remain the same. Development of the west quarry <br /> will disturb a portion of land that is currently undisturbed, but runoff from this area will be <br /> detained within the south quarry and will be pumped out to a permitted outfall, if not fully <br /> infiltrated within 72 hours. No irrigation facilities will influence or be impacted by the Site <br /> drainage. <br /> 1670 Broadway,Suite 3400,Denver,CO 80202-4824 hdrinc.com <br /> (303)764-1520 <br />