Laserfiche WebLink
The alluvial aquifer at the Site consists mainly of gravelly sand which grades to sandy gravel, usually becoming more <br /> gravelly with depth. Aggregate unit thickness varied from 11 feet in H-13 west of the Site to 57 feet in H-02 in the <br /> northeastern side of the Site. <br /> 4.0 EXISTING GROUNDWATER CONDITIONS <br /> Groundwater was measured in seven (7) piezometers, and typically occurs at depths usually ranging from 4.6' to 29.3' <br /> feet below surface with shallower groundwater to the north and west of the Site. The prevailing groundwater flow <br /> direction at the Site is to the northwest reflecting the Site topography. Groundwater in the area is tributary to the South <br /> Platte River located west of the site. Depth to groundwater is shallower, as little as 5 feet, underlying the Town of <br /> Gilcrest likely due to the deep bedrock and low topography relative to the surrounding area. Locally the groundwater <br /> levels and flow directions are influenced by: <br /> > The South Platte River is northwest of the Site. For most of the year,the river likely acts as a drainage <br /> way, or gaining river reach, maintaining groundwater levels at elevations greater than water elevations <br /> in the river. In shorter periods of high runoff, usually in the spring, river water levels will locally <br /> recharge the groundwater table. <br /> ➢ The Farmers Independent Ditch (FIDCO) passes southeast of the Site under the intersection of Weld <br /> County Road 42 and Weld County Road 29. North of Weld County Road 36, the ditch joins with a <br /> wetland drain which likely provides water year-round. During the irrigation season, the ditch diverts <br /> water from the South Platte River as well raising the water level of the ditch. <br /> > The Western Mutual Ditch (Western)traverses the southeast corner of the Site and bisects Cell 1 and <br /> 2. The ditch flows most of the year based on diversion records for the ditch headgate located <br /> southwest of Platteville. <br /> > The Evans#2 Ditch passes southeast of the Town of Gilcrest on the eastern side of Highway 85. The <br /> ditch did not have discharge during the months of November and December but did have flow during <br /> the remainder of the year. <br /> > The Platte Valley Ditch branches off from the Evans#2 Ditch south of the Town of Gilcrest. The Platte <br /> Valley Ditch does not have a stream gage, so it was assumed that it was flowing at the same time as <br /> the Evans#2 Ditch. <br /> ➢ There are two unnamed sloughs approximately 500 feet to the west and another a 1/2 a mile to the <br /> northeast of the Site, respectively. These sloughs receive groundwater flowing out from the higher <br /> terrace and act as drains transporting water to the river. <br /> ➢ There are multiple recharge ponds in the area of interest which provide groundwater recharge (refer <br /> Figure 2). <br /> > Irrigation: The Site is located in an area of irrigated cropland. Applied irrigation that is not lost to <br /> evaporation and transpiration recharges the groundwater. <br /> ➢ Alluvial wells: Other than the seven monitoring wells drilled at the Site for monitoring groundwater <br /> levels,there are also eight pumping wells permitted within 600 feet of the mine property. <br /> Groundwater Model Report—Monarch DENM Gravel Mine Site -2- January 2023 <br />