2019-01-29_HYDROLOGY - M1983090

• Permit No: M1983090
• IBM Index Class Name: HYDROLOGY
• Doc Date: 1/29/2019
• Doc Name: Substitute Water Supply Plan
• From: DWR
• To: Civil Resources, LLC
• Email Name: ECS
• Media Type: D
• Archive: No

Poudre Pits SWSP January 29, 2019
Plan IDs 3218 Et 4585 Page 2 of 8
The La Poudre site consists of three separate cells designated as the West Lake, Middle Lake,
and East Lake. An additional parcel in the northwest corner of Section 19, known as the Lee Parcel,
has been amended into the mining permit boundary and begin being mined in February or March of
2018. The area is proposed to continue to be wet mined throughout 2019 and will have
approximately 2 acres of groundwater exposed in dewatering trenching, which is included in the La
Poudre site depletions for the West Site. Dewatering water will be delivered to recharge in the West
Lake/Wildlife Lake located in the western portion of the La Poudre site. It is assumed that 50% of
the water pumped into the lake will recharge into the West Lake and 50% will be discharged from the
lake directly to the river. No mining is proposed to occur at the La Poudre North site during this plan
period.
Depletions
Evaporation and Operational Losses
During this SWSP period, depletions will consist of evaporation losses and production
depletions at the La Poudre and North La Poudre Pits. The depletions for each site are shown in the
following table:
Table B - 2019 Site Depletions (acre-feet)*
Water Water Total
Evaporation Lost in Consumed Dust Total
Site Name Losses Mined in Concrete Control Depletions Lagged
Depletions
Product Batching
West 38.30 12.50 13.08 2.20 66.08 60.2
La Poudre Middle 3.66 0 0 0 3.66 3.66
East 34.29 0 0 0 34.29 34.29
North La Poudre 28.14 0 0 0 28.14 26.64
Total 104.39 12.50 13.08 3.16 132.17 124.78
'Depletions shown do not include those from past or projected dewatering operations at the sites.
For the purposes of this SWSP, depletions are assumed to impact the Cache la Poudre River
perpendicular to the point of depletions, which is considered to be the centroid of the exposed
surface area at each site. Evaporative depletions for each site were calculated using a gross annual
evaporation of 38.5 inches, with a credit of 9.78 inches for effective precipitation (based on an
average annual precipitation of 13.97 inches for the Windsor weather station). The West Site
includes a 14-acre Wildlife Pond and 2 acres of dewatering trenches, the Middle Lake contains a
1.53-acre pond, and the East Lake contains of a 14.33-acre pond. The La Poudre North site contains
a 4.89-acre pond and a 6.87-acre pond. The attached Figure 1 shows the location of each of these
exposed groundwater features.
Operational losses at the La Poudre and North La Poudre sites will consist of 2.20 acre-feet of
water for dust control, 12.50 acre-feet of water lost with 425,000 tons of mined aggregate, and
13.08 acre-feet of water for the production of 105,000 cubic yards of concrete (assumes 40 gallons of
water per cubic yard of concrete). The aggregate is mined below the water table and is washed;
therefore the water retained in the mined product is considered to be 4.0% of the mined material by