2019-02-15_PERMIT FILE - M2018060

• Permit No: M2018060
• IBM Index Class Name: PERMIT FILE
• Doc Date: 2/15/2019
• Doc Name: Adequacy Review Response
• From: Applegate Group
• To: DRMS
• Email Name: ECS
• Media Type: D
• Archive: No

Eric Scott
RE:Response to Preliminary Review of a 112 Construction Materials Reclamation Permit Application Package,
Tollgate Pit,File No.M-2018-060
February 15, 2019
Page 2 of 7
Table I below describes the suggested native grass seed mix from the USDA-NRCS to be used on the site.'
The soil in the area is predominately loamy, which was a driver for the seed selection. Note this seeding
guide is for a Native Grass Drill;if seed is planted via broadcast methods,then all pounds of live seed rates
should be doubled. The full recommendation, which includes alternatives, is on file if needed. The
Rangeland Management Specialist with the USDA-NRCS did not recommend mulch or other soil
amendments, yet a cover crop for the first year is recommended in order to protect and enhance the soil.
The cover crop shall be planted in the spring and allowed to grow and frost die off.The following fall,the
native seed mix shall be planted.
TABLE 1 USDA-NRCS RECOMMENDED SEED MIX.
Native Grass Seed Mix
Weld County(Greeley NRCS Field Office)
Mix based on Critical Area Planting(342)specifications
for soil textures other than Sand or Loamy Sand
PLSlACRE Q %of Mixture PLS RATE PER
VARIETY SPECIES 100% ACRE
El Reno Sideoats Grama ' 9.0 30 2.70
Arriba Western Wheat grass' 160 25 4.00
Lodorm Green Needlegrass ' 100 20 2.00
Hachita Blue Grama' 3.0 15 0.45
Blackwell Switch grass 4.0 10 0.40
Total 100 9.55
Seeding Dates. November i to May 15 required grasses in mu
—Mix must be seeded with a Native Grass Drill
Since post-mining land use consists of a lined reservoir whose east half is in the flood plain(Zone A),the
need for armored inlet and outlet structures was evaluated using guidelines from the Urban Drainage Flood
Control District(UDFCD).z Based on the guidance, it was determined that a single armored side channel
spillway would be sufficient to meet the inlet and outlet structure requirements. As shown in Figure 1
below, FEMA's National Flood Hazard Layer indicates that the potential for flooding in the area is due to
backwater filling and then overtopping the nearby Storms Lake Drainage.This overtopping is likely to first
occur at the southwest portion of the site where ground elevations are lowest. Once Storms Lake Drainage
overtops,a side channel spillway will direct the water to a controlled and armored section which will allow
flood flows into the pit while protecting the pit slopes and slurry wall.
' Gerald Gregory(USDA-NRCS),e-mail to Katy Bilisoly(Applegate Group),2/5/19.
2 Technical Review Guidelines for Gravel Mining&Water Storage Activities Within or Adjacent to 100-Year
Floodplains,UDFCD,January 2013.
www.applegategroup.com Denver a Glenwood Springs a Hotchkiss (303)452-661 1