2018-01-16_PERMIT FILE - M2017036 ‎(2)‎

• Permit No: M2017036
• IBM Index Class Name: Permit File
• Doc Date: 1/16/2018
• Doc Name: Groundwater Study
• From: Loveland Ready-Mix Concrete
• To: DRMS
• Email Name: JLE
• Media Type: D
• Archive: No

Second Submittal
3.0 NUMERICAL MODEL FRAMEWORK
3.1 Numerical Modeling Code
Telesto chose the widely-accepted groundwater flow model,MODFLOW 2005 (Harbaugh,
2017). Groundwater flow is mathematically simulated utilizing a block-centered, finite
difference approach to solve the corresponding governing differential equations.
MODFLOW 2005 is a series of modular subroutines that are highly independent of one
another that allows flexibility in simulating a multitude of boundary and geometric
conditions. Modeling input was accomplished with a variety of tools including Model
Muse (Winston, 2009), Global Mapper 16 (Blue Marble Geographics, 2015) and internal
codes developed by Telesto.
3.2 Numerical Modeling Domain
The modeling domain is best described as a rectangular grid oriented parallel to the main
direction of groundwater flow. ,In MODFLOW,the modeling coordinates start in the upper
left,corner and are defined by rows and columns. The upper left corner of the model is
located at geographical northing of 40' 38' 57.2758" N and easting of 105' 08' 05.4861"
W. The modeling grid is oriented clockwise around the upper left corner at 208' 07'29.0"
from true north. The model domain is 23,609 feet (4.47 miles) in the x-dimension and
9,834 feet (1.86 miles) in the y-dimension. The model domain is gridded in the x-
dimension by 158 columns ranging from 25 to 1,000 feet in width, and in the y-dimension
by 147 rows ranging from 24 to 1,000 feet. The extents of the model are sufficiently large
as to avoid unduly influencing the hydraulics near the Site and areas of concern. Figure 9
displays the model domain oriented against Colorado State Plane North coordinates.
3.3 Numerical Model Boundaries
Model boundaries define the hydrologic conditions of the aquifer throughout the model
domain. As described in Section 2.3.1,various boundary conditions exist. Where bedrock
outcrops or sub-crops,the model is inactive or has a zero flux boundary. Sealed gravel pits
are also treated as zero flux boundaries and are represented by inactive cells in the model.
The two main ditches influencing groundwater near the Site are the Little Cache la Poudre
Loveland Ready-Mix Concrete 13 Telesto Sohitions,Inc.
21)180112_gm=lwmi wdy_2xWsubimnaI d— Jan uary 2018