HomeMy WebLinkAbout20131872.tiffVarra Companies, Inc.
OFFICE OF SPECIAL PROJECTS
8120 Gage Street Frederick, CO 80516 Telephone (303) 666-6657 Fax (303) 666-6743
Subject: Technical Revision #2 — Varra Companies, Inc.
Western Sugar Reclamation Land Development Project - OMLR Permit #:
M-2010-049
This Technical Revision (TR) is intended to satisfy the option of lining approved basins.
The basins identified in the original Office of Mined Land Reclamation (OMLR) permit
are presently approved and bonded for in an unlined state. The permit provides for the
option that the basins be lined in order to liberate the waters presently securing the
exposed groundwater in the unlined condition. The option to line the basins requires a
technical revision to the approved permit to assure the OMLR that lined basins will
comply with state law.
To satisfy the concerns of the OMLR, included with this revision is a report on the
potential for shadowing and mounding by AWES, LLC of 27 June 2013. The report
concludes:
'...that lining mined gravel pits has almost unmeasurable influences to the
surrounding groundwater hydrology and does not change hydraulic gradients
beyond the variations that would normally be expected in the geologic settings
associated with the operation.'
We anticipate the OMLR will concur with this analysis. Once operations near completion
of any lined basin, the Colorado Department of Water Resources Office of the State
Engineer (OSE) will be contacted and the lined basins will be approved prior to use.
The OSE approval letter will be provided to the OMLR as a condition of the permit and
satisfaction that the lined basin has met the specifications necessary to pass a liner test
as part of the OSE approval process.
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RECEIVED
ED
JUL 19 2013
CWELD COUNTY
MM/SS!ONER c.
2013-1872
Varra Companies, Inc. Western Sugar Land Development Project
OMLR Permit #: M-2010-049
Technical Revision #2 19 July 2013
June 27, 2013
,AWES LAC
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Varra Companies
8120 Gage Street
Frederick, Colorado 80516
Attn: Mr. Garrett Varra
RE: Shadow/Mounding Analysis
AWES No. 1-3-1320
Dear Mr. Varra:
You have requested that I provide an opinion on possible effects that lining excavated gravel mines
can have on local groundwater hydrology — specifically shadow and mounding effects created by the
presence of a low permeability barrier. My opinion is that lining active or inactive gravel mines will
deflect groundwater around the barrier, but hydraulic gradients changes at any distance away from
the barrier will be insignificant. My rational for this opinion is provided below.
Varra Companies, Inc., (Varra) has two lined pits used for water storage that were lined in 2003 (Pit
112) and 2010 (Pit 110). The method of lining was compacting several feet of clay and shale bedrock
on the side walls of the pits, thus creating a low permeability liner. Varra installed 13 monitoring
wells at each of these locations and obtained water levels on a periodic basis. Pit 110 consists of two
lined pits and Pit 112 is a single pit. The locations of these pits are depicted on Figure 1. The
monitoring well locations are depicted on Plates 1 through 4, which are included in Attachments A
and B.
In order to evaluate the effects of low permeability liners on the local groundwater hydrology, 1 used
the geo-statistical model Surfer° to evaluate groundwater flow direction and gradients in the
vicinity of the pits. I input water level data obtained from the monitoring wells for the months of
January and July 2012, at each location. I chose these months to evaluate possible changes that
might occur from irrigation returns in the vicinity of the pits. After the model runs were competed, I
used a vector analysis to depict variation in gradient and flow direction. Model runs for Pits 112 and
110 are presented in Attachments A and B, respectively.
A review of both Attachments show that groundwater is being deflected around the pits, but the
changes in gradients are so minor the model also predicts that groundwater will flow through the
pits as well — this indicates the liners are competent and that there is little to no hydraulic
connection between the aquifer and pond. For graphical purposes, I superimposed red lines that
represent the primary groundwater flow patterns in the vicinity of the pits. The vector analysis
shows very minor changes in hydraulic gradients up and down stream of the pits indicating shadow
and mounding are not occurring.
A§US
4809 Four Star Court, Fort Collins, CO 80524 970-590-3807
Shadow/Mounding Analysis
Varra Gravel Operations
Longmont, Colorado
Page 2
In July of 2010, I provided Varra with the results of a groundwater model simulation of an
impermeable barrier in a uniform flow field. The model results closely approximate actual field
conditions as documented from water level data obtained by Varra. That analysis is presented in
Attachment C.
This analysis indicates that lining mined gravel pits has almost unmeasurable influences to the
surrounding groundwater hydrology and does not change hydraulic gradients beyond the variations
that would normally be expected in the geologic settings associated with your operations. It is my
understanding the Division of Reclamation and Mine Safety has requested technical revisions to
your mine permits for the placement of liners at active operations such as Great Western Sugar.
Until the pits are completely lined and dewatering is no longer occurring a static analysis cannot be
performed, however, the analysis presented should be valid for mines in similar geologic settings.
If you have any questions regarding this letter or attachment, please contact me at 970-590-3807.
Sincerely,
AWES, LLC
Joby L. Adams, P.G.
Principal Hydrogeologist
LS
4809 Four Star Court, Fort Collins, CO 80524 970-590-3807
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ATTACHMENT A
PIT 112 VECTOR ANALYSIS
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ATTACHMENT B
PIT 110 VECTOR ANALYSIS
Plate 3 - Pit 110 Vector Analysis
3000 -
2500 -
2000 -
1500 -
1000-
500 -
P f0 -f2
lfl.
TOP PIPf►48f
Pf10-10
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TOP PIPE -4812.6
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Note - Contour Interval = 1 foot
Jan 2012 Water Level Data
3000
0.02201
0.02101
0.02001
0.01901
0.01801
0.01701
0.01601
0.01501
0.01401
0.01301
0.01201
0.01101
0.01001
0.00901
0.00801
0.00701
0.00601
0.00501
0.00401
0.00301
0.00201
0.00101
Gradient - ft/ft
Plate 4 - Pit 110 Vector Analysis
3000
2500
2000
1500
1000
500
P110-12
%P0UiO-a 11.
TOP PIPP-48
500
1000
1500
2000
2500
P110-0
6P0t*t-.820.4
TOP PIPE -1823.
0
Note - Contour Interval = 0.75 foot
Jly 2012 Water Level Data
3000
1
0.023
0.022
0.021
0.02
0.019
0.018
0.017
0.016
0.015
0.014
0.013
0.012
0.011
0.01
0.009
0.008
0.007
0.006
0.005
0.004
0.003
0.002
0.001
Gradient - ft/ft
ATTACHMENT C
Groundwater Model Analysis
CGRSI�
July 1,2010
Mr. Garrett Varra
Varra Companies, Inc.
8120 Gage Street
Frederick, Colorado 80203
Re: Water Impoundment Hydrology
CGRS No. 1-135-10807ab
Dear Garrett:
ENVIRONMENTAL
This letter and attachments address comments presented by Colorado Division
of Reclamation, Mining and Safety regarding mounding and shadowing related to
water impoundments.
Any impoundment or pond that holds water at an elevation above the
surrounding water table will have the potential of increasing the water table
elevation (mounding) at some distance from the pond, which is determined by
the total groundwater -pond head difference. For ponds that are large in areal
extent the distance to no influence on the upstream side is usually less than the
downstream side as the head difference will be less based on the water table's
hydraulic gradient. The influence imposed by the pond can be estimated by one
dimensional unconfined flow solutions presented by McWhorter and Sunada,
1977. Numerical models can be used but we have found model results generally
agree well with analytical solutions. An example calculation using a one
dimensional unconfined flow equation is presented as Attachment A.
In most unconfined flow regimes we consider the distance to no influence (or
measurable influence) generally to be on the order of 600 feet. For your
operations it appears the pond and groundwater head difference is on the order
of five feet. Given this scenario at 100 and 300 feet from the pond the resulting
mounding would be four and two feet, respectively. We advise that great care be
given when constructing water impoundments (lined or unlined) within 100 feet
of any subsurface structures.
We have evaluated the affects of impermeable barriers on groundwater
hydrology by using the analytical model TWODAN. We simulated a uniform flow
field using aquifer properties typically associated with sand and gravel deposits.
We then simulated an impermeable barrier within the flow field. The results
indicate that the groundwater hydrology is modified but only severely in very
close proximity to the barrier. Upstream of the barrier the hydraulic gradient will
increase and will decrease downstream of the barrier. Hydraulic gradient
changes of between one and two feet are observed within 15 feet of the barrier
wall but are negligible at any significant distance from the hydraulic structure. A
P O Box 1489
Fort Collins, CO 80522 1 800-288-2657
F 970-493 7986 www cgrs.com
Mr. Garrett Varra
July 1, 2010
Page 2 of 2
graphical output depicting the barrier wall simulation is provided in Attachment
B. We also ran simulation in ModFlow, which yielded similar results.
If you have any questions regarding this letter, please contact me at 970-493-
7780.
Sincerely,
CGRS, Inc.
Joby L. Adams. P.G.
Principal/Hydrogeologist
REFERENCES
McWhorter, D. and Sunada, D. K., 1977. Groundwater Hydrology and Hydraulics.
Water Resource Publications, Littleton, Colorado, pp 146-148.
ATTACHMENT A
UNCONFINED FLOW ANALYSIS
Spreadsheet Calculates One Dimensional Head Distribution (Unconfined)
h = Nihi2 + X/L (H2 - hi2)
H Head at no influence (ft)
h Head at point of interest (calculated)
hi Head at retention pond
X Distance from pond to point of interest (ft)
L Distanct to no influence (ft)
4808
MEM
4813
300
600
ATTACHMENT B
BARRIER WALL MODEL RESULTS
86
88
90
92
94
96
98
100
- — - Approximate Gradient Line in Uniform Flow
X span: 0 to 800 Y span: 0 to 800
Impermeable Barrier Solution
Varra Companies
-1(
Varra Companies, Inc.
Office of Special Projects
1431 East 16`'' Street Greeley, Colorado 80631 Telephone (970) 353-8310 Fax (970) 353-4047
Friday 19 July 2013
Weld County Clerk to the Board
1150 `O' Street
Greeley, Colorado 80631
Subject: Technical Revision #2 — Varra Companies, Inc.
Western Sugar Reclamation Land Development Project - OMLR Permit #: M-2010-049
Materials submitted to the Colorado Division of Reclamation Mining and Safety (CRMS) - Office
of Mined Land Reclamation (OMLR):
• Correspondence and Technical Revision of 19 July 2013 and attending attachments.
•
ATTACH EM ENTS :
• Proof of Placement — Weld County Clerk to the Board
• AWES, LLC Shadow & Mounding Analysis Report of 27 June 2013
Your signature below acknowledges receipt of the above referenced material, as attached. The
material shouldbe added to the above referenced Application, as originally submitted to the Weld
County Clerk to the Board, and made accessible for public review.
Received On
By:
Office of the Weld County Clerk to the Board of County Commissioners
, 2013
RECEIVED
JUL 192013
COMMISSIONERS
COUNTY
Varra Companies, Inc. Western Sugar Land Development Project
OMLR Permit #: M-2010-049 Technical Revision #2 19 July 2013
Varra Companies, Inc.
❑FFICE OF SPECIAL PROJECTS
8120 Gage Street Frederick, CO 80516 Telephone (303) 666-6657 Fax (303) 666-6743
Friday 19 July 2013
Colorado Office of Mined Land Reclamation
Division of Reclamation Mining and Safety
1313 Sherman Street, Room 215
Denver, Colorado 80203
Subject: Technical Revision #2 — Varra Companies, Inc.
Western Sugar Reclamation Land Development Project - OMLR Permit #:
M-2010-049
Enclosed, find two (2) copies of a Technical Revision (TR) to revise the above referenced
original permit providing for the lining of all previously approved basins.
If you need clarification or assistance, please do not hesitate to contact me directly.
Sincerely,
Varra Com anies, Inc.
Bradford Janes, Forester
Liaison, Office of Special Projects
bljforester(11 msn.com
(970)-353-8310
cc. Garrett Varra, Vice President
Varra Companies, Inc.
ATTACHEMENTS:
• Technical Revision Submittal Fee — Check #: 34221 in the Amount of $216.00.
• Proof of Placement — Weld County Clerk to the Board
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