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Home My WebLink About036 Appendix X.4 - Geo Report Supplement SUPPLEMENTAL GEOTECHNICAL REPORT LAUREL MEADOWS SUDIVISION BOZEMAN, MONTANA CLIENT ROI, LLC P.O. BOX 11388 BOZEMAN, MONTANA 59718 PREPARED BY ANDREW PILSKALNS P.E. C A S T L E R O C K G E O T E C H N I C A L E N G I N E E R I N G C:\Users\andy\Job Files\JBS 2025\025026CR\GI, Laurel Meadows Sub. ROI.docx SUPPLEMENTAL GEOTECHNICAL REPORT LAUREL MEADOWS SUBDIVISION May 12th, 2025 ROI, LLC P.O. Box 11388 Bozeman, Montana 59718 Atten: Mr. Patrick Eibs Re: Laurel Meadows Subdivision A.K.A. The Lakes at Valley West (South) Castle Rock Geotechnical Job No. 25026 Dear Mr. Patrick Eibs, This letter is the second supplemental letter to the Geotechnical Report prepared for what was previously called “The Lakes at Valley West (South)” development which is now known as the Laurel Meadows Subdivision. This report will reference all previous work completed by Castle Rock Geotechnical for The Lakes at Valley West (South) as Laurel Meadows Subdivision. Castle Rock Geotechnical has prepared ‘Study of Grounds’ (geotechnical) Reports for multiple phases of the Lakes at Valley West Subdivision since 2014 and the Study of Grounds Report for the April 10th, 2020, Laurel Meadows Subdivision, and the August 29th, 2022, Supplemental Report. I received a phone call on March 3, 2025, from Patrick Eibs to coordinate with Best Excavation to conduct a subsurface field investigation for Blocks 1 & 2 and part of 3 of the Laurel Meadows Subdivision. A limited excavated test hole geotechnical investigation was performed on April 29th, 2025, at 8:00 am. Best Excavation and Patrick Eibs were present during the field investigation. The primary purpose of this subsurface investigation is to share subsurface information gathered from 36 test holes excavated. See Figure 1A – Test Hole Map in the Attachments at the end of this report. C:\Users\andy\Job Files\JBS 2025\025026CR\GI, Laurel Meadows Sub. ROI.docx SUPPLEMENTAL GEOTECHNICAL REPORT LAUREL MEADOWS SUBDIVISION Sincerely, Andrew Pilskalns P.E., M. ASCE, M, GBA CASTLE ROCK GEOTECHNICAL ENGINEERING, INC. C:\Users\andy\Job Files\JBS 2025\025026CR\GI, Laurel Meadows Sub. ROI.docx SUPPLEMENTAL GEOTECHNICAL REPORT LAUREL MEADOWS SUBDIVISION TEST HOLE LOGS Test Hole 1 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-6” CL – Clay Loam 1’-6” GP –Gravel w/Sand wet Test Hole 2 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-6” CL – Clay Loam 1’-6” GP –Gravel w/Sand wet Test Hole 3 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-0” CL – Clay Loam 2’-0” GP –Gravel w/Sand wet Test Hole 4 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-6” CL – Clay Loam 1’-6” GP –Gravel w/Sand wet Test Hole 5 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-0” CL – Clay Loam 1’-5” GP –Gravel w/Sand Test Hole 6 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-0” CL – Clay Loam 2’-0” wet GP –Gravel w/Sand Test Hole 7 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-0” CL – Clay Loam 1-6” wet GP –Gravel w/Sand Test Hole 8 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-0” CL – Clay Loam 2’-3” GP –Gravel w/Sand wet Test Hole 9 USDA Classification Horizon Thickness OL, ML –Topsoil 0’-8” CL – Clay Loam 2’-0” GP –Gravel w/Sand Test Hole 10 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-0” CL – Clay Loam 2’-2” wet GP –Gravel w/Sand Test Hole 11 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-2” CL – Clay Loam 2’-0” wet GP –Gravel w/Sand Test Hole 12 USDA Classification Horizon Thickness OL, ML –Topsoil 2’-0” CL – Clay Loam 1’-6” wet GP –Gravel w/Sand Test Hole 13 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-6” CL – Clay Loam 1’-6” wet GP –Gravel w/Sand Test Hole 14 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-6” CL – Clay Loam 3’-0” GP –Gravel w/Sand wet C:\Users\andy\Job Files\JBS 2025\025026CR\GI, Laurel Meadows Sub. ROI.docx SUPPLEMENTAL GEOTECHNICAL REPORT LAUREL MEADOWS SUBDIVISION Test Hole 15 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-0” CL – Clay Loam 2’-6” GP –Gravel w/Sand wet Test Hole 16 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-6” CL – Clay Loam 3’-0” GP –Gravel w/Sand wet Test Hole 17 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-0” CL – Clay Loam 2’-0” wet GP –Gravel w/Sand Test Hole 18 USDA Classification Horizon Thickness OL, ML –Topsoil 0’-10” CL – Clay Loam 2’-2” wet GP –Gravel w/Sand Test Hole 19 USDA Classification Horizon Thickness OL, ML –Topsoil 0’-10” CL – Clay Loam 2’-0” GP –Gravel w/Sand wet Test Hole 20 USDA Classification Horizon Thickness OL, ML –Topsoil 2’-0” CL – Clay Loam 1’-5” GP –Gravel w/Sand wet Test Hole 21 USDA Classification Horizon Thickness OL, ML –Topsoil 2’-0” CL – Clay Loam 2’-1” wet GP –Gravel w/Sand wet Test Hole 22 USDA Classification Horizon Thickness OL, ML –Topsoil 2’-0” CL – Clay Loam 0’-10” GP –Gravel w/Sand wet Test Hole 23 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-0” CL – Clay Loam 2’-1” GP –Gravel w/Sand wet Test Hole 24 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-6” CL – Clay Loam 2’-0” GP –Gravel w/Sand wet Test Hole 25 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-3” CL – Clay Loam 2’-0” wet GP –Gravel w/Sand wet Test Hole 26 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-0” CL – Clay Loam 1’-6” GP –Gravel w/Sand wet Test Hole 27 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-0” CL – Clay Loam 1’-10” GP –Gravel w/Sand wet Test Hole 28 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-0” CL – Clay Loam 2’-6” wet GP –Gravel w/Sand wet C:\Users\andy\Job Files\JBS 2025\025026CR\GI, Laurel Meadows Sub. ROI.docx SUPPLEMENTAL GEOTECHNICAL REPORT LAUREL MEADOWS SUBDIVISION Test Hole 29 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-2” CL – Clay Loam 2’-0” wet GP –Gravel w/Sand Test Hole 30 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-0” CL – Clay Loam 2’-0” GP –Gravel w/Sand wet Test Hole 31 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-6” CL – Clay Loam 1’-6” GP –Gravel w/Sand wet Test Hole 32 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-6” CL – Clay Loam 1’-6” GP –Gravel w/Sand Test Hole 33 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-0” CL – Clay Loam 2’-6” GP –Gravel w/Sand wet Test Hole 34 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-2” CL – Clay Loam 2’-0” GP –Gravel w/Sand wet Test Hole 35 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-0” CL – Clay Loam 3’-0” wet GP –Gravel w/Sand wet Test Hole 36 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-0” CL – Clay Loam 1’-6” wet GP –Gravel w/Sand wet Test Hole 37 USDA Classification Horizon Thickness OL, ML –Topsoil 1’-0” CL – Clay Loam 2’-3” wet GP –Gravel w/Sand wet C:\Users\andy\Job Files\JBS 2025\025026CR\GI, Laurel Meadows Sub. ROI.docx SUPPLEMENTAL GEOTECHNICAL REPORT LAUREL MEADOWS SUBDIVISION INTRODUCTION The following is a short summary of the scope of geotechnical services for the Laurel Meadows Subdivision. Castle Rock Geotechnical conducted the subsurface field investigation in Blocks 1, 2 and portions of Block 3. The investigation was to primarily determine the depth of suitable load-bearing gravel and sand aggregate for subdivision development and residential home construction. The Test Pit Logs are recorded and tabulated in the previous pages. Figure 1 - Site Map shows the project location in the Bozeman Montana Topographic Map. Groundwater monitoring is being conducted by Others. Castle Rock Geotechnical does not determine the finished floor elevation of buildings. All soils were field classified using the Unified Soil Classification System. In general, the subsurface grounds consist primarily of three horizons. The first is a very dark brown organic topsoil horizon from 12 to 18 inches thick USCS symbol (OL-ML). FIGURE 1 – Vicinity Topographic Map The second horizon is a brown-gray lean clay loam USCS symbol (CL) which is from 12 to 24 inches thick depending on location. In areas shown as wet, the clay is saturated by water for long periods of time and oxygen diffusion is restricted, leading to anaerobic conditions where reduction reactions dominate. The presence of decomposable organic materials provides an energy source for microbes, further influencing redox conditions. Lean clays, which are fine- textured soils with poor drainage, tend to develop redoximorphic features due to prolonged saturation such as color change and hard and soft irregular shaped bodies. The masses are accumulation of iron or manganese oxides in the soil which lead to the formation of secondary clay minerals. C:\Users\andy\Job Files\JBS 2025\025026CR\GI, Laurel Meadows Sub. ROI.docx SUPPLEMENTAL GEOTECHNICAL REPORT LAUREL MEADOWS SUBDIVISION Areas where “wet’ is placed next to the second horizon indicates that some level of redox reaction is occurring in the relatively thin lean clay horizon. The third horizon consists of gravel and sand aggregate, commonly referred to as alluvium, with a Unified Soil Classification System (USCS) symbol of GP. All test holes were excavated down to stiff alluvial gravels, with Test Pits 14, 16, 21, and 35 being the deepest, reaching native alluvial gravels from 4 feet to 4½ feet below top of existing ground. In all other test holes, native alluvial gravels and sand aggregate were closer to the ground surface. RECOMMENDATIONS Based on the field investigation all previous geotechnical recommendations can be adhered to. All building sites should be observed and approved by the Geotechnical Engineer that prepared the report at the time the building footprint is excavated. Upon approval of the Geotechnical Engineer free draining washed rock can be placed or if the water table is drawn down 2 feet in the building footprint, imported 3-inch minus pit run gravels can be placed in 1- foot lifts up to footing grade. Based on high groundwater elevations it is assumed that as much as 2½-feet of structural fill may be necessary to elevate a foundation. Footing elevations should be a minimum 20 inches above high groundwater. Structural fill for this project can be durable, hard 3/4-inch diameter free-draining, highly durable, hard gravels with excellent resistance to water damage and erosion. These gravels provide superior stability, excellent load-bearing capacity, and effective permeability, making them ideal for drainage applications, road bases, and construction projects. Imported processed, durable 3 inch minus pit run gravels containing less than 10% non-plastic fines USCS Symbol (GW) is also defined as structural fill. If water is present then ¾ inch diameter durable free draining gravels should be placed 1-foot above the water level. The washed rock will act as a suction break so that additional 3-inch minus gravels placed upon the washed rock will not liquify and bring up water into the well-graded pit run during compaction of the material to densify it. Additional geotechnical recommendations are provided in the Castle Rock Geotechnical Report 2020 – The Lakes at Valley West (South), prepared on April 10, 2020. C:\Users\andy\Job Files\JBS 2025\025026CR\GI, Laurel Meadows Sub. ROI.docx SUPPLEMENTAL GEOTECHNICAL REPORT LAUREL MEADOWS SUBDIVISION CONCLUSION If the subgrade improvement recommendations are adhered to for residential development and construction, they should be adequate for supporting the residential building loads given above. If you have any questions or concerns about the contents of this letter, please contact me at your convenience. Services performed by Castle Rock Geotechnical Engineering for this project have been conducted with that level of care and skill ordinarily exercised by members of the profession currently practicing in this area under similar budget and time constraints. The successful completion of the geotechnical engineering of this project is dependent on continued professional geotechnical services to ensure the proper interpretation and intentions of the recommendations herein and to observe the construction phases of the design (earthwork, foundation, site grading). The Geotechnical Recommendations within are strictly for the use of the Client at this location and should not be applied to other sites. Castle Rock Geotechnical is a member of the Geoprofessional Business Association (GBA). To better understand how geotechnical reports are to be interpreted please read Important Information about Your Geotechnical Report, found in the Attachments provided by GBA. PROFESSIONAL CERTIFICATION I hereby certify this report was prepared by me and that I am a duly licensed Professional Engineer under the laws of the State of Montana. Thank you for using Castle Rock Geotechnical Engineering. If you have any questions regarding this report or require our services during the construction phase of this project, please call our office. I appreciate the opportunity to work with you. Prepared By: Andrew Pilskalns, P.E., M. ASCE, M.GBA Civil Engineer LICENSED – Montana, Utah, Colorado, Hawaii, Nevada, North Dakota, Wyoming C:\Users\andy\Job Files\JBS 2025\025026CR\GI, Laurel Meadows Sub. ROI.docx SUPPLEMENTAL GEOTECHNICAL REPORT LAUREL MEADOWS SUBDIVISION CASTLE ROCK GEOTECHNICAL ENGINEERING 9 Cedar Lake Drive Butte, MONTANA 59701 C: (406) 539-8439 O: (406) 209-5573 ATTACHMENTS Figure 1A – TEST HOLE MAP Figure 2 – Important Information About Your Geotechnical Report C:\Users\andy\Job Files\JBS 2025\025026CR\GI, Laurel Meadows Sub. ROI.docx SUPPLEMENTAL GEOTECHNICAL REPORT LAUREL MEADOWS SUBDIVISION Figure 1A – Test Hole Map 22 C:\Users\andy\Job Files\JBS 2025\025020CR\136 Countryside Lane, BG, MT.docx SUPPLEMENTAL GEOTECHNICAL REPORT LAUREL MEADOWS SUBDIVISION FIGURE 2 – IMPORTANT INFORMATION ABOUT YOUR GEOTECHNICAL REPORT 23 C:\Users\andy\Job Files\JBS 2025\025020CR\136 Countryside Lane, BG, MT.docx