Prepared For: Town of Castle Valley, Utah

HYDROLOGIC ASSESSMENT OF THE SURFACE WATER AND GROUNDWATER RESOURCES OF CASTLE VALLEY, UTAH: PART 2: HESA-BASED SITING OF CULINERY WELL FOR TOWN OF CASTLE VALLEY Authors: Dr. Kenneth E. Kolm, Hydrologic Systems Analysis, LLC., Golden, Colorado and Paul K.M. van der Heijde, Heath Hydrology, Inc., Boulder, Colorado Prepared For: Town of Castle Valley, Utah December 2016

Front Page: Town of Castle Valley, Utah (November 2013)

Table of Contents 1. INTRODUCTION... 1 2. HYDROLOGIC AND HYDROGEOLOGIC CONSIDERATIONS REGARDING LOCATION OF CASTLE VALLEY CULINARY WELL SITE 3 3. OTHER CONSIDERATIONS REGARDING LOCATION OF CASTLE VALLEY CULINARY WELL SITE 5 4. SUMMARY AND CONCLUSIONS.. 8 5. REFERENCES. 9 List of Figures Figure 1 Topographic Map Showing the Locations of the Town of Castle Valley, the Castle Creek/Placer Creek Watershed, and the Proposed Well in a Regional Setting.. 1 Figure 2 Ortho Image Showing the Locations of the Incorporated Area of the Town of Castle Valley, Parcels, and the Proposed Well 2 Figure 3 Ortho Image Showing the Locations of Parcels and the Proposed Well. 3 Figure 4 Map Showing Major Hydro-units and Hydro-structures (Faults and Fracture Zones) in the Lower Castle Valley Area. 4 Figure 5 Map Showing the Location of the Proposed Well Site and Shallow Aquifer Thicknesses 4 Figure 6 Recharge and Discharge Zones and Groundwater Flow Direction in Shallow Unconsolidated and Deep Bedrock Aquifers 5 Figure 7 Total Dissolved Solids (TDS) of the Castle Valley Groundwater System. 6 Figure 8 Map Showing the Location of the Town of Castle Valley Culinary Well Site Based on the HESA-Derived Castle Creek Subsystem and Preliminary Water Balances in the TCV Area 7 Town of Castle Valley, Grand County, Utah Culinary Well Siting HSA/HHI page iii

1 INTRODUCTION Under an agreement with Town of Castle Valley, Utah, Hydrologic Systems Analysis LLC (HSA) of Golden, Colorado, in conjunction with Heath Hydrology, Inc. (HHI) of Boulder, Colorado, was tasked: 1) to perform a Hydrologic and Environmental System Analysis (HESA) of the surface water and groundwater resources of the valleys and uplands of the Castle Creek Watershed in the vicinity of the Town of Castle Valley in Grand County, Utah; 2) to collect climate, hydrological, and other data necessary for constructing a water budget for the lower section of the Valley in the vicinity of the Town of Castle Valley, and to develop such water budget; and 3) to determine the siting of a town well for culinary water supply and fire protection application. The first two tasks were reported in: The report "Hydrologic Assessment of the Surface Water and Groundwater Resources of Castle Valley, Utah: Part 1: Hydrologic and Environmental System Analysis (HESA) and Preliminary Water Budget" prepared by Dr. Kenneth E. Kolm, Hydrologic Systems Analysis, LLC., Golden, Colorado and Paul K.M. van der Heijde, Heath Hydrology, Inc., Boulder, Colorado for The Town of Castle Valley, Utah (March 2016). The current report presents the HESA/GIS - based siting considerations for a new Town of Castle Valley well. Figure 1. Topographic Map Showing the Locations of the Town of Castle Valley, the Castle Creek/Placer Creek Watershed, and the Proposed Well in a Regional Setting (Utah GIS, 2016). Town of Castle Valley, Grand County, Utah Culinary Well Siting HSA/HHI page 1

Castle Valley is located between the La Sal Mountains to the south, the Colorado River to the north, the Porcupine Rim to the west, and the Castle Spires Rim to the east (Figure 1). The HESA performed under Task 1 distinguishes between 3 hydrologic entities: 1) the entire Castle Creek watershed (including Placer Creek drainage); 2) the lower Castle Valley hydrologic system (northwest of roughly a line from the Castleton area to the Porcupine Ranch); and 3) the Castle Valley Groundwater Basin (Quaternary and Tertiary sand and gravels, and underlying fractured bedrock). The lower Castle Valley hydrologic system is the setting for the preliminary water budget discussed in Kolm and van der Heijde (2016). The siting of a Town well in the lower Castle Valley is based on the nature and extent of the major hydrogeological systems present; the surface water hydrology of the area; water resources-related land use considerations such as nearby irrigation, landfill disposal, septic tank locations, and domestic water wells; access during construction and (occasional) water utilization; and proximity to the Town jurisdictional areas and fire station. According to Town staff, the proposed well will provide backup water supply and additional fire protection use, and will not be part of a piped municipal water supply distribution system. The preferential site identified by Town staff is located at approximately 109 23'23.552"W and 38 38'37.515"N in the eastern part of parcel 090000367, located on the northeast side of the platted area just north of Castle Creek, within the incorporated area of the Valley (Figures 2 and 3). The study included a site visit together with Town staff. Figure 2. Ortho Image Showing the Locations of the Incorporated Area of the Town of Castle Valley, Parcels, and the Proposed Well (Utah GIS, 2016). Town of Castle Valley, Grand County, Utah Culinary Well Siting HSA/HHI page 2

Figure 3. Ortho Image Showing the Locations of Parcels and the Proposed Well (Utah GIS, 2016). 2 HYDROLOGIC AND HYDROGEOLOGIC CONSIDERATIONS REGARDING LOCATION OF CASTLE VALLEY CULINARY WELL SITE The proposed well site is located in the Castle Creek watershed, and is part of the lower Castle Valley Groundwater Basin composed of Quaternary and Tertiary sand and gravels, and underlying fractured bedrock (Figure 4). The site is located in the Stream Alluvium (Qal) hydrogeologic unit, possible underlain by other Quaternary unconsolidated sand and gravel units. The estimated thickness of the unconsolidated deposits at the well site is 300-350 ft (Figure 5). Neighboring well depths show a depth to water table of about 100 ft, therefore, the potential saturated thickness at the well site is approximately 200 250 ft. The proposed well site is located on the edge of the Permian Cutler Bedrock High K Zone hydrostructure (Figure 4), which may increase its saturated thickness and yield, but may also decrease the water quality. Otherwise, the impermeable bedrock under the well site location is Permian Cutler Formation (Kolm and van der Heijde, 2016). Town of Castle Valley, Grand County, Utah Culinary Well Siting HSA/HHI page 3

Figure 4. Map Showing Major Hydro-units and Hydro-structures (Faults and Fracture Zones) in the Lower Castle Valley Area (Detail; from Kolm and van der Heijde, 2016). Figure 5. Map Showing the Location of the Proposed Well Site and Shallow Aquifer Thicknesses (After Kolm and van der Heijde, 2016). Town of Castle Valley, Grand County, Utah Culinary Well Siting HSA/HHI page 4

According to Kolm and van der Heijde (2016), the proposed well location is in the Castle Creek Subsystem in the middle of the flow system where Castle Creek is a losing stream, and recharge (Rc) to the Quaternary gravels is occurring (Figures 6). Castle Creek in this area is 80-100ft above the water table and pumping at of a well at the proposed site location should not affect the stream (Castle Creek) since the stream and the groundwater systems are not connected. Figure 6. Recharge and Discharge Zones and Groundwater Flow Direction in Shallow Unconsolidated and Deep Bedrock Aquifers (Detail from Kolm and van der Heijde, 2016). 3 OTHER CONSIDERATIONS REGARDING LOCATION OF CASTLE VALLEY CULINARY WELL SITE The water quality data indicate that regardless of the hydrogeologic framework configuration, good water quality of low TDS (251-500 mg/l) to slightly higher TDS (501-750 mg/l) water is expected in the vicinity of the proposed well site (Lowe and Others, 2004) (Figure 7). The proposed well site is located up gradient approximately 425 ft and 540 ft from the nearest well and septic sites, 115 ft from Castle Creek, which is a losing stream at this location, and over 375 ft from the nearest trash disposal site and irrigated lands, none of which are upgradient of the proposed well (Figure 8). The proposed well is intended for domestic culinary supply and fire protection. The Town does not anticipate to operate the well as part of a conventional municipal distribution system, but to deliver water in 1,000 gallon loads once an hour (a rate that will hardly if ever actually occur) on an occasional basis. This means that the Town wants to be able to pump 50-100 gallons per minute for 10-20 minutes once every hour during the day from the proposed well. If the Town wants to be able to fill fire trucks quickly, then perhaps more pumping capacity Town of Castle Valley, Grand County, Utah Culinary Well Siting HSA/HHI page 5

may be needed, but it would only be used once in a great while. The Town does not anticipate to get into any arrangements where it is pumping from this well to supplement Castle Creek or enhance the green belt. So, the worst case scenario is: 2,000 gal/hr for 24 hrs = 48,000 gal/day. If this pumping rate would be sustained for an entire year, it results in a consumptive use of 53.767 acre-ft/yr, which is far below the 2400 acre-ft/yr of groundwater coming into the Valley according to Kolm and van der Heijde ( 2016). Figure 7. Total Dissolved Solids (TDS) of the Castle Valley Groundwater System (From Lowe and Others, 2004) The next phase is for the Town of Castle Valley to complete a well design and aquifer test to determine the precise effects and yields of the new Town well at the recommended site location. Town of Castle Valley, Grand County, Utah Culinary Well Siting HSA/HHI page 6

Figure 8. Map Showing the Location of the Town of Castle Valley Culinary Well Site Based on the HESA- Derived Castle Creek Subsystem and Preliminary Water Balances in the TCV Area. Town of Castle Valley, Grand County, Utah Culinary Well Siting HSA/HHI page 7

4 SUMMARY AND CONCLUSIONS Under an agreement with Town of Castle Valley, Utah, Hydrologic Systems Analysis LLC (HSA) of Golden, Colorado, in conjunction with Heath Hydrology, Inc. (HHI) of Boulder, Colorado, was tasked to perform a Hydrologic and Environmental System Analysis (HESA) of the surface water and groundwater resources of the valleys and uplands of the Castle Creek Watershed; 2) to collect climate, hydrological, and other data necessary for constructing a water budget for the lower section of the Valley in the vicinity of the Town of Castle Valley, and to develop such water budget; and 3) to determine the siting of a town well for culinary water supply and fire protection application. The first two tasks were reported in: The report "Hydrologic Assessment of the Surface Water and Groundwater Resources of Castle Valley, Utah: Part 1: Hydrologic and Environmental System Analysis (HESA) and Preliminary Water Budget" prepared by Dr. Kenneth E. Kolm, Hydrologic Systems Analysis, LLC., Golden, Colorado and Paul K.M. van der Heijde, Heath Hydrology, Inc., Boulder, Colorado for The Town of Castle Valley, Utah (March 2016). The current report presents the HESA/GIS - based siting considerations for a new Town of Castle Valley well. Summary of the Town of Castle Valley municipal well site characteristics, based on the HESA-derived information (Kolm and van der Heijde, 2016) is as follows: 1) The well is located in the Stream Alluvium (Qal) hydrogeologic unit with a potential thickness of 300-350 ft. Neighboring well depths show a depth to water table of about 100 ft, therefore, the potential saturated thickness at the well site is approximately 200 250 ft; 2) The well site is located on the edge of the Permian Cutler Bedrock High K Zone hydrostructure, which may increase its saturated thickness and yield, but may also decrease the water quality. The impermeable bedrock under the well site locations is Permian Cutler Formation; 3) The water quality data indicate that regardless of the hydrogeologic framework configuration, good water quality of low TDS (251-500 mg/l) to slightly higher TDS (501-750 mg/l) water is expected; 4) The well site is in the Castle Creek Subsystem in the middle of the flow system where Castle Creek is a losing stream, and recharge to the Quaternary gravels is occurring. The pumping of the well at the site location should not affect the stream (Castle Creek) since the stream and the groundwater systems are not connected at this location; and 5) Human affects should be minimal since most of the neighboring well activity, irrigation, septic systems, and trash disposal are located downgradient from the proposed well site. The anticipated maximum well use is about 54 acreft/yr, well below the more than 2,400 acre-ft/yr of groundwater flowing into the Valley. The next phase is for the Town of Castle Valley to complete a well design and aquifer test to determine the precise effects and yields of the new Town well at the recommended site location. Town of Castle Valley, Grand County, Utah Culinary Well Siting HSA/HHI page 8

5 REFERENCES Kolm, K.E, and P.K.M. van der Heijde, 2016. Hydrologic Assessment of the Surface Water and Groundwater Resources of Castle Valley, Utah: Part 1: Hydrologic and Environmental System Analysis (HESA) and Preliminary Water Budget. Report prepared for the Town of Castle Valley, Grand County, Utah. Lowe, M., J. Wallace, C.E. Bishop, and H.A. Hurlow. 2004. Ground-water Quality Classification and Recommended Septic Tank Soil-Absorption-System Density Maps, Castle Valley Grand County, Utah. Utah Geological Survey, SS-113. Utah GIS, 2016. Utah Automated Geographic Reference Center (AGRC), State Geographic Information Database (SGID) (https://gis.utah.gov/data/#). Data downloaded in 2016. Town of Castle Valley, Grand County, Utah Culinary Well Siting HSA/HHI page 9