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Home My WebLink About029 - Appendix O.1 - Seasonally High Groundwater 1091 Stoneridge Drive • Bozeman, Montana • Phone (406) 587-1115 • www.chengineers.com • E-Mail: info@chengineers.com March 8, 2022 City of Bozeman Engineering Division Attn: Cody Flammond, P.E Re: Seasonally High Groundwater – Ferguson Farm II Subdivision; Bozeman, MT (170827) Dear Cody, The following letter is meant to address your comments regarding the seasonally high groundwater elevation at the Ferguson Farm II Subdivision. The Ferguson Farm II Subdivision is located in the Gallatin River Basin. The floor or bottom of the basin consists of Precambrian bedrock that has been overlain by relatively thick Tertiary age sediments and Quaternary Alluvium. The shallowest source of groundwater is from the quaternary alluvium, which varies in thickness from around 70 feet near Bozeman, Hot Springs to more than 800 feet deep north of Belgrade. The tertiary sediments are generally considered to be a semi-confined aquifer, and although not fully separated from the overlying quaternary alluvium by an impermeable layer, could be considered a second aquifer. Given the significant depth to the tertiary deposits of 70 feet below grounds surface (bgs) or more, it is our opinion that this aquifer will not be affected by the proposed development. The only potentially impacted aquifer beneath the subject property is within the quaternary alluvium that is located nearer to the surface. The depth to the quaternary alluvium aquifer was determined by monitoring the groundwater elevations across the subject property. To complete this monitoring, we installed a total of five groundwater monitoring wells. The groundwater elevations within these wells were checked weekly starting on April 5, 2019 and continued through July 26, 2019. Also, the groundwater levels were also recorded on the day of the test pit excavations, which was March 19, 2019. The shallowest groundwater levels were recorded on April 23, 2019 and the deepest groundwater levels were recorded during the initial test pit excavations on March 19, 2019. The shallowest groundwater elevation observed was 4.28 feet bgs and the deepest was 10.0 feet bgs. Please note that this high-water level was only observed in 1 of the five wells, with the other highest recorded water levels being 4.73 feet bgs, 5.50 feet bgs and 5.89 feet bgs. Also one of our Civil/Structural Engineering and Surveying groundwater monitoring wells never did encounter groundwater during the monitoring period; this well was installed to a depth of 8.17 feet bgs. The quaternary alluvium aquifer is primarily recharged through infiltration into the aquifer following the snowmelt and spring precipitation season. The peak groundwater elevation across the valley typically correlates with this recharge of the aquifer and usually occurs sometime in early April to late May. Additionally, infiltration from irrigation ditches does contribute to a seasonal rise in groundwater levels, and is especially pronounced on properties that practice flood irrigation. Given the high permeability of the quaternary alluvium aquifer, flood irrigation impacts are generally localized and do not increase the groundwater elevations significantly on properties that are not directly adjacent to where the flood irrigation is occurring or on properties that are not located directly downgradient in the direction of groundwater flow. Typically, the water table is at its lowest elevation during the winter months, when the ground is frozen and infiltration is not readily occurring while at the same time groundwater is being drawn from the aquifer via water wells for residential, agricultural (water for livestock) and commercial purposes. This is supported by the groundwater elevations encountered on the day the test pits were excavated and the groundwater monitoring wells were installed, at which time we observed the deepest groundwater levels. Based on the groundwater contours from the Gallatin City County Health Department Environmental Mapper (which is based on the Slagle Map), the groundwater flow direction beneath the subject property is nearly directly north. From a review of aerial images, it appears the nearest property that potentially flood irrigates are the agricultural fields located approximately 0.31 miles southeast of the subject property. Because a mobile home park and residential structures are located directly south of the subject property, and the fact that flood irrigation is not practiced on the subject property or on any adjacent property, it is our opinion that flood irrigation practices will not have a significant impact on the groundwater elevations across the subject property. Please note that we are not saying there will be no impact, but that the impact will not result in a groundwater elevation that is higher than the peak elevation that was observed in April. This is supported by the static water levels recorded within two nearby potable water wells that were drilled during times of the year past the date of which we completed groundwater monitoring for this project, as well as our data from groundwater monitoring for the Norton Ranch Subdivision Phase 4. We were able to find well lithologic logs for a well drilled at 3950 Valley Commons Drive and another well that was drilled at 4181 Fallon Avenue (The Ridge Athletic Club). The well drilled at 3950 Valley Commons Drive had a static water level of 11 feet bgs on August 10, 2015 and the well drilled at 4181 Fallon Avenue had a static water level of 10 feet bgs on October 31, 2007. This is further supported by groundwater monitoring that was conducted for the Norton Ranch Subdivision Phase 4, which is located approximately 0.5 miles directly to the west of the Ferguson Farm II Subdivision. Our groundwater monitoring for this site was conducted from February 2018 to September 2018. The peak groundwater elevation for the Norton Ranch project was recorded on April 13, 2018, which is very similar to the date we observed a groundwater 3/8/22, 10:25 AM Montana's Ground-Water Information Center (GWIC) | Site Report | V.11.2022 https://mbmggwic.mtech.edu/sqlserver/v11/reports/SiteSummary.asp?gwicid=240395&agency=mbmg&session=1143282&1/1 MONTANA WELL LOG REPORT Other Options This well log reports the activities of a licensed Montana well driller, serves as the official record of work done within the borehole and casing, and describes the amount of water encountered. This report is compiled electronically from the contents of the Ground Water Information Center (GWIC) database for this site. Acquiring water rights is the well owner's responsibility and is NOT accomplished by the filing of this report. Return to menu Plot this site in State Library Digital Atlas Plot this site in Google Maps View scanned well log (2/7/2008 7:12:55 AM) Site Name: THE RIDGE ATHLETIC CLUB GWIC Id: 240395 DNRC Water Right: 30043437 Section 1: Well Owner(s) 1) THE RIDGE ATHLETIC CLUB (MAIL) 4181 FALLON AVEBOZEMAN MT 59718 [10/31/2007] Section 2: Location Township Range Section Quarter Sections 02S 05E 10 NE¼ SE¼ SE¼ County Geocode GALLATIN Latitude Longitude Geomethod Datum 45.68025 -111.097583 NAV-GPS WGS84 Ground Surface Altitude Ground Surface Method Datum Date Addition Block Lot Section 3: Proposed Use of Water UNKNOWN (1) Section 4: Type of Work Drilling Method: ROTARY Status: NEW WELL Section 5: Well Completion Date Date well completed: Wednesday, October 31, 2007 Section 6: Well Construction Details Borehole dimensions From To Diameter 0 60 6 Casing From To Diameter Wall Thickness Pressure Rating Joint Type -1.5 58.5 6 0.25 WELDED STEEL Completion (Perf/Screen) From To Diameter # of Openings Size of Openings Description 58.5 60 6 OPEN BOTTOM Annular Space (Seal/Grout/Packer) From To Description Cont. Fed? 0 0 BENTONITE Y Section 7: Well Test Data Total Depth: 60 Static Water Level: 10 Water Temperature: Air Test * 43 gpm with drill stem set at 55 feet for 1 hours. Time of recovery 1 hours. Recovery water level 10 feet. Pumping water level feet. * During the well test the discharge rate shall be as uniform as possible. This rate may ormay not be the sustainable yield of the well. Sustainable yield does not include the reservoir of the well casing. Section 8: Remarks Section 9: Well Log Geologic Source Unassigned From To Description 0 4 TOP SOIL 4 60 SAND AND GRAVEL WITH THIN LAYERS OF CLAY Driller Certification All work performed and reported in this well log is in compliance with the Montana wellconstruction standards. This report is true to the best of my knowledge. Name:BERNARD WESTRA Company:VAN DYKEN DRILLING INC License No:WWC-380 Date Completed:10/31/2007 3/8/22, 10:23 AM Montana's Ground-Water Information Center (GWIC) | Site Report | V.11.2022 https://mbmggwic.mtech.edu/sqlserver/v11/reports/SiteSummary.asp?gwicid=284069&agency=mbmg&session=1143282&1/1 MONTANA WELL LOG REPORT Other Options This well log reports the activities of a licensed Montana well driller, serves as the official record of work done within the borehole and casing, and describes the amount of water encountered. This report is compiled electronically from the contents of the Ground Water Information Center (GWIC) database for this site. Acquiring water rights is the well owner's responsibility and is NOT accomplished by the filing of this report. Return to menu Plot this site in State Library Digital Atlas Plot this site in Google Maps View scanned update/correction (12/14/2020 1:05:13 PM) Site Name: SEVEN COMMONS CONDOMINIUM OWNERS ASSC. GWIC Id: 284069 Section 1: Well Owner(s) 1) SEVEN COMMONS CONDOMINIUM OWNERS ASSC. (WELL) 3950 VALLEY COMMONS DR BOZEMAN MT 59718 [11/19/2020] 2) HECK, SCOTT (MAIL)700 DELL PLACE BOZEMAN MT 59715 [08/10/2015] 3) HECK, SCOTT (WELL) 3950 VALLEY COMMONS DR. BOZEMAN MT 59718 [08/10/2015] Section 2: Location Township Range Section Quarter Sections 02S 05E 10 SE¼ SW¼ SE¼ County Geocode GALLATIN Latitude Longitude Geomethod Datum 45.672055541 -111.088488214 TRS-SEC NAD83 Ground Surface Altitude Ground Surface Method Datum Date Addition Block Lot VALLEY COMMONS BUSINESS PARK 7 Section 3: Proposed Use of Water IRRIGATION (1) Section 4: Type of Work Drilling Method: ROTARY Status: NEW WELL Section 5: Well Completion Date Date well completed: Monday, August 10, 2015 Section 6: Well Construction Details Borehole dimensions From To Diameter 0 60 6 Casing From To Diameter Wall Thickness Pressure Rating Joint Type -1.5 56 6 0.25 WELDED A53B STEEL Completion (Perf/Screen) From To Diameter # of Openings Size of Openings Description 56 60 6 OPEN BOTTOM Annular Space (Seal/Grout/Packer) From To Description Cont. Fed? 0 25 BENTONITE Y Section 7: Well Test Data Total Depth: 60 Static Water Level: 11 Water Temperature: Air Test * 42 gpm with drill stem set at 50 feet for 1 hours. Time of recovery 1 hours. Recovery water level 11 feet. Pumping water level feet. * During the well test the discharge rate shall be as uniform as possible. This rate may ormay not be the sustainable yield of the well. Sustainable yield does not include the reservoir of the well casing. Section 8: Remarks Section 9: Well Log Geologic Source Unassigned From To Description 0 3 TOPSOIL 3 60 SAND AND GRAVEL WITH THIN LAYERS OF CLAY Driller Certification All work performed and reported in this well log is in compliance with the Montana wellconstruction standards. This report is true to the best of my knowledge. Name:KURT WESTRA Company:VAN DYKEN DRILLING INC License No:WWC-656 Date Completed:8/10/2015 Gallatin County GIS311 W. Main Room 305Bozeman, MT 59715Phone: (406) 582-3049Email: GIS@gallatin.mt.gov March 8, 2022 Gallatin County GIS ± 0 0.15 0.3 0.45 0.6 Miles Water Addresses Minor Roads Numbered Highways StreamsRiversLakes Structure AddressesRecent AddressesParcels Cities Quarter SectionsSubdivisionsMinor Subdivisions " " Sections Townships Alley/DrivewayUnpavedPaved Rail Line MontanaU.S.Interstates Public LandsLocal GovernmentState of MontanaU.S. Bureau of Land ManagementU.S. Forest ServiceU.S. Park Service Project Engineer:Matt H Project: Well Information:bgs = below ground surface ags = above ground surface MW-1 MW-2 MW-3 MW-4 10'10'10'10' 0.58 1.71 0.71 0.92 Groundwater Information: MW-1 MW-2 MW-3 MW-4 02/14/18 6.81 6.29 4.20 4.38 03/13/18 6.94 6.39 4.20 4.34 04/13/18 6.10 5.10 3.12 3.30 05/11/18 6.87 6.36 4.20 4.35 05/25/18 6.78 6.18 4.14 4.31 06/08/18 6.99 6.62 4.37 4.54 06/22/18 6.30 6.51 4.48 4.60 07/06/18 8.64 8.21 5.91 6.10 07/20/18 7.49 7.32 4.85 5.10 08/03/18 7.47 7.32 4.85 5.21 08/17/18 7.57 7.10 5.00 5.21 08/30/18 7.15 6.82 4.50 4.70 09/14/18 7.25 6.85 4.65 4.80 Monitor Well Data Project Number:161140 Norton East Ranch Subdivision, Phase 4 Project Location:Bozeman Well ID Well Depth (feet-bgs) Top of Well (feet-ags) Date Depth to Ground Water (feet-bgs) BB+z z2:1 Δσ EtBqH DCompressible soil layerRigid soil layer