REV101480

• Permit No: M1974015
• IBM Index Class Name: Revision
• Doc Name: EXHIBIT G WATER INFORMATION
• Type & Sequence: AM6
• Media Type: D
• Archive: No

ROCKY MOUNTAIN CONSULTANTS. INC.
~i
Inc
January 28, 1997
Mr. Scott Gudahl
Western Mobile, Inc.
P.O. Box 18570
Boulder, Colorado 80308
Premiere Builtling
825 Delaware Ave.. Suite 500
Longmont. CO BO501
[phone]
Metro [phone]
FAX [phone]
E-mail rmclong~rmli.com
Re: Preliminary Evaluation of Groundwater Impacts Due to Aggregate Mining and
Reclamation, Western Mobile Aggregate Mine near Lyons, Colorado; RMC Job
No. 80-1448.029.00
Dear Mr. Gudahl:
This letter report presents our preliminary evaluation of groundwater impacts due to aggregate
mining and reclamation at the Western Mobile aggregate mine located east of Lyons in Boulder
County, Colorado. The purpose of this report is to consider potential impacts to groundwater due
to site mining acrtivities based on hydrogeologic data collected at the site and our experience at
similar sites. Based on the potential impacts identified, the mitigating measures currently in-place
and proposed in the reclamation plan were evaluated.
INTRODUCTION
Western Mobile currently mines aggregate resources from the St. Vrain Creek alluvium
approximately 1.5 to 2.0 miles east-southeast of Lyons, Colorado in Boulder County, Colorado
(Figure 1). Mining will extend from U.S. Highway 36 east-southeast about two miles to 61st Street.
The typical north-south dimension of the area to be mined is about 2,000 to 2,500 feet. Mining
will extend north to within about 200 to 300 feet of the St. Vrain Creek, and to the south to near the
bedrock escarpment along the southern limit of the alluvium.
Current land use at and near the site includes irrigated agricultural and low density residential.
Irrigation is by ditches diverting from St. Vrain Creek. Several ditches are present in the area to be
mined and in areas adjacent to the mine. Principal ditches in the area include the Boulder Supply
Canal, Swede Ditch, Smead Ditch, South Branch, Foothills Reservoir inlet, and Foothills Reservoir
outlet (Plate 1). Several ditches wholly or partially owned by Western Mobile are also in the
vicinity, including Baker and Weese, Weese Private, Goss No. 1, Goss No. 2, Clough and True,
and Clough Private. Foothills Reservoir is located at the southeast limit of the proposed area to be
mined. Groundwater is the primary source of domestic and/or stock water for many neighbors of
the mine.
The proposed mine plan utilizes a combination of upland and riparian terrain valleys and "gravel
lakes" for mine reclamation. Features of the plan include reclaiming the bulk of the area as a
valley. Surface and groundwater features north of the valley will be protected by a slurry wall
CIVIL AND ENVIRONMENTAL ENGINEERING • PLANNING