2019-08-27_HYDROLOGY - M1977436

• Permit No: M1977436
• IBM Index Class Name: Hydrology
• Doc Date: 8/27/2019
• Doc Name: Substitute Water Supply Plan
• From: DWR
• To: DRMS
• Email Name: JLE
• Media Type: D
• Archive: No

Amended Aggregate Industries South Platte Combined SWSP August 27, 2019
Plan I Ds 3614, 47731 3624, 47721 4616, 3437, 3376, 3650, 3668, and 5475 Page 3 of 21
Active Dewatering: No
Hazeltine Pit Status: Mining operations at the Hazeltine Pit have been completed and
(South Platte reclamation is in progress. The Hazeltine Pit was lined with a soil
Mainstem) bentonite slurry wall, and was approved as having been lined to the
design standard referenced in the August 1999 State Engineer Guidelines
for Lining Criteria for Gravel Pits in a letter dated May 25, 2016. The
construction of the slurry wall resulted in groundwater mounding and
flooding of adjacent property. The operator has installed a gravity drain
to dewater the site on a continuous basis. A 45-day leak test was
performed after installation of the permanent drain to verify that the
liner was not impacted. The liner was re-approved in a letter dated
March 22, 2018. Depletions covered by this SWSP are limited to lagged
depletions from past operations at the site, including past dewatering.
Exposed Groundwater Surface: 0
Active Dewatering: No
Brighton Pit Status: Mining operations at the Brighton Pit are complete and
(South Platte reclamation is in progress. Depletions covered by this SWSP include
Mainstem) water lost due to evaporation and post-pumping dewatering depletions.
The south and central reservoirs are lined with a slurry wall (WDIDs
0203031 and 0203385) and have obtained SEO liner approval.
Reclamation work includes backfi lli ng the remaining exposed areas, of
which 1 acre was backfi lied in 2013.
Exposed Groundwater Surface: 5.0 acres
Active Dewatering: No
Tucson South Pit Status: Mining Aggregate intends to begin actively mining the Tucson
(South Platte South Pit during 2019. Depletions covered by this SWSP include water
Mainstem) lost due to evaporation, aggregate production, dust control, and
dewatering. Under this amendment, up to an additional 8.0 acres of
groundwater will be exposed at the site as a result of mining and test pits
within the permit boundary. The site is not proposed to be dewatered
during 2019.
Exposed Groundwater Surface: 10.0 acres (including 2.0 acres
transferred from the Tucson Pit)
Active Dewatering: No
Wattenberg Pit Status: Aggregate intends to continue actively mining the Wattenberg Pit
(South Platte during 2019. Depletions covered by this SWSP include water lost due to
Mainstem) evaporation, aggregate production, dust control, and dewatering. Prior
to 2018, the north pit was dewatered with water delivered to the nearby
Broda Pond. The north cell has since been lined, and dewatering
operations have shifted to the south cell with water to be discharged to
multiple locations. A portion of the water will be pumped to the
Stillwater Ski Lake located south of the pit to mitigate lower levels in the
pond due to the suppressed water table resulting from dewatering. A
portion of the water may be pumped to a new recharge pond on the west
side of the site in order to mitigate low water table levels in domestic
wells in the area. The remainder of the dewatering discharge will be
pumped across the South Platte River to the Broda Pond located within