HYDRO24557

• Permit No: M2001046
• IBM Index Class Name: Hydrology
• Doc Date: 5/13/2002
• Doc Name: Proposed Wetland Monitoring Plan
• From: Wright Water Engineers Inc.
• To: DMG
• Permit Index Doc Type: Other Ground Water
• Media Type: D
• Archive: No

NViNE
MEMORANDUM
,'
To: Tug Martin
Banks and Gesso, LLC
From: Wright Water Engineers, Inc.
Dave Mehan and Gary Witt
Date: May 13, 2002
Re: Proposed Wetland Monitoring Plan for Nix Sand and Gravel Operation
This memorandum provides a recommended plan to monitor groundwater levels for the proposed
Nix Sand and Gravel Operation (Nix Pit), and discusses a recommended approach to define a
"trigger" for mitigation for the wetland on the Sage Hill Farm. These issues were discussed with
Division of Minerals and Geology (DMG) staff during a meeting on April 24, 2002 and expressed
by them in a follow-up letter.
Wright Water Engineers, Ina {WWE) evaluated potential effects on groundwater levels and the
hydrology of the wetland, as described in our report of April 2002. This report concluded that
water levels in the wetland vary considerably and aze affected by irrigation water use in the vicinity.
The report recommended that Owens Bros. Concrete provide water to the wetland from "Pond 1"
or water right shazes it owns in the Last Chance Ditch if monitoring shows reductions in water
Levels in the wetland from its operations.
Proposed Groundwater Monitoring Plan
The purpose of the monitoring plan is to: 1) characterize pre-mining groundwater levels beneath the
wetland on the Sage Hill Farm and proposed mining azea, and 2) assist in identifying hydrologic
impacts from the proposed operation. Data collected to date shows significant variation in
groundwater levels beneath the wetland, and a steady decline in groundwater levels from last fall.
This decline corresponds to a period of relatively low precipitation and the non-imgation season,
and may be indicative of the natural groundwater regime. However, it also occurred following
mining and dewatering at the Varna Aggregate Pit north of the proposed Nix Pit. It is thought that
groundwater will rise in the spring and summer with increased precipitation and the start of the
irrigation season.
It is recommended that groundwater levels continue to be monitored in the 19 piezometers and
wells listed in Table 3 of our April 2002 report. In addition, it is recommended that six new
piezometers (MW-20 through MW-25) be installed at the locations shown on the attached figure.
Groundwater needs to be monitored to determine, to the extent possible, pre-mining conditions.
Observations at MW-20 through MW-23 will help to better establish the pre-mining water table
conditions, including potential existing impacts from the Varna operation north of the proposed Nix
Wright Water Engineers, inc., 2490 W. 26"' Avenue, Ste. 100A, Denver, CO 8027 i
Tel. [phone]; Fax. 303/480-'1020, e-mai::[e-mail]