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Home My WebLink About007 Preliminary Stormwater ReportPRELIMINARY DRAINAGE REPORT FOR North 3rd Ave Apartments Bozeman, MT 59715 November 18, 2022 Parcel No.: RGG6409 and RGG6410 Applicant Name: Chase Huber Devco Family of Companies Applicant Address: PO Box 4108 Bellevue, WA 98009 Applicant Telephone: (425) 736-0580 Owner Name: Devco Family of Companies Applicant Address: PO Box 4108 Bellevue, WA 98009 Applicant Telephone: (425) 736-0580 Project Engineer Name: Chris Miller, P.E. Project Engineer Address: 1000 2nd Ave, Suite 3900 Seattle, WA 98104 Project Engineer Telephone: (206) 639-7938 Project Engineer Email: chris.miller@kimley-horn.com Contact Name: Chris Miller, P.E. Project Engineer Address: 1000 2nd Ave, Suite 3900 Seattle, WA 98104 Project Engineer Telephone: (206) 639-7938 Project Engineer Email: chris.miller@kimley-horn.com NORTH 3RD APARTMENTS, LLC. NORTH 3RD APARTMENTS, LLC. North 3rd Apartments Kimley-Horn and Associates, Inc. Bozeman, MT Preliminary Drainage Report November 2022 Page ii PREPARED FOR: DEVCO FAMILY OF COMPANIES PO BOX 4108 BELLEVUE, WA 98009 PREPARED BY: KIMLEY-HORN AND ASSOCIATES, INC. 1000 SECOND AVENUE, SUITE 3900 SEATTLE, WA 98101 CHRIS MILLER, PE Disclosure Statement: This document, together with the concepts and designs presented herein, as an instrument of service, is intended only for the specific purpose and client for which it was prepared. Reuse of and improper reliance on this document without written authorization and adaptation by Kimley-Horn and Associates, Inc. shall be without liability to Kimley-Horn and Associates, Inc. NORTH 3RD APARTMENTS, LLC. North 3rd Apartments Kimley-Horn and Associates, Inc. Bozeman, MT Preliminary Drainage Report November 2022 Page iii Table of Contents 1.0 PROJECT OVERVIEW .............................................................................................................................. 1 2.0 EXISTING SITE CONDITIONS .................................................................................................................... 1 3.0 PROPOSED SITE DESIGN ......................................................................................................................... 2 ATTACHMENTS AND APPENDICES APPENDIX A: MAPS ATTACHMENT NO. 1 – VICINITY MAP ATTACHMENT NO. 2 – PRE-DEVELOPMENT DRAINAGE AREA MAP ATTACHMENT NO. 3 – POST-DEVELOPMENT DRAINAGE AREA MAP ATTACHMENT NO. 4 – USGS SOILS MAP ATTACHMENT NO. 5 – FEMA FLOOD INSURANCE RATE MAP (FIRM) APPENDIX B: GEOTECHNICAL REPORT (BY OTHERS) APPENDIX C: RETENTION SYSTEM SIZING CALCULATIONS APPENDIX D: CONVEYANCE CALCULATIONS North 3rd Apartments Kimley-Horn and Associates, Inc. Bozeman, MT Preliminary Drainage Report November 2022 Page 1 1.0 PROJECT OVERVIEW The Devco Bozeman N 3rd Ave Multifamily project proposes to develop a 5.8 acre, currently vacant R-5 zoned property, into a multi-family apartment housing complex. The project site is located to the West of N 3rd Ave and W Cottonwood St. in Bozeman, MT within Gallatin County. The project area is bounded to the north by single- family residential developments, to the west by Westlake Park, to the south by other multifamily residential developments, and to the east by N 3rd Ave. Approximately all 5.8 acres of the site will be disturbed for regrading, drainage, and development purposes. The site is not located near any environmentally critical areas or buffer zones. The purpose of this technical information report is to provide an explanation of the site improvements and to demonstrate how the project will meet stormwater requirements. Figure 1 below shows the project site location. Figure 1. Vicinity Map 2.0 EXISTING SITE CONDITIONS The existing site is undeveloped with the majority of landcover as grass. Generally the site sheet flows north/northwest onto neighboring property in existing conditions. The soils are predominantly classified as Turner Loam with a hydrologic soil group of type B. The existing conditions are shown in Appendix A, Attachment 2. The USGS soils summary has been provided in Appendix A, Attachment 4. The project site is not located within a FEMA Special Flood Hazard Area (SFHA). The site is mapped on FEMA Flood Insurance Rate Map (FIRM) Panels 30031C0808E and 30031C0816E, effective date 4/21/2021 for both panels. The PROJECT SITE North 3rd Apartments Kimley-Horn and Associates, Inc. Bozeman, MT Preliminary Drainage Report November 2022 Page 2 site lies within an unshaded FEMA Zone X, outside the 0.2% annual chance floodplain. See the FIRM Panel in Appendix A, Attachment 5. 3.0 PROPOSED SITE DESIGN The proposed site will consist of a multifamily residential development and North Third Avenue with 7 proposed apartment buildings, clubhouse, parking, and associated utility and storm infrastructure. In the final design, stormwater runoff from the development will route into inlets throughout the site where water will then be conveyed to a retention system. The proposed conditions are shown in Appendix A, Attachment 3. The retention system has been sized to the 10-year, 2-hour storm event per City of Bozeman Requirements. Calculations showing the proposed volume calculations can be seen in Appendix C. An ADS StormTech Chamber System is proposed to accommodate the volume. Infiltration has not been factored into the sizing of the vault per City of Bozeman Standards; however, infiltration is feasible onsite, and therefore the bottom of the chamber is gravel and will allow stormwater to percolate as in existing conditions. The details for the StormTech Chamber can be seen in sheets C5.30 and C5.40 of the plans accompanying this submittal. An emergency overflow pipe connection has been made between the onsite conveyance pipes and an existing conveyance system on the western portion of the site. For the overflow sizing, the system was analyzed with infiltration. Based on this analysis, the vault can infiltrate storms up to the 100-year 24-hour event. Larger storm events are intended to bypass. Conveyance calculations for the storm infrastructure onsite were completed using the Bentley StormCAD program. The rational method was used with a 25 year storm per City of Bozeman standards. Results for the conveyance calcs can be seen in Appendix D. North 3rd Apartments Kimley-Horn and Associates, Inc. Bozeman, MT Preliminary Drainage Report November 2022 Page 3 APPENDIX A: MAPS National Flood Hazard Layer FIRMette 0 500 1,000 1,500 2,000250 Feet Ü SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT SPECIAL FLOODHAZARD AREAS Without Base Flood Elevation (BFE)Zone A, V, A99With BFE or DepthZone AE, AO, AH, VE, AR Regulatory Floodway 0.2% Annual Chance Flood Hazard, Areasof 1% annual chance flood with averagedepth less than one foot or with drainageareas of less than one square mileZone X Future Conditions 1% Annual Chance Flood HazardZone X Area with Reduced Flood Risk due to Levee. See Notes.Zone X Area with Flood Risk due to LeveeZone D NO SCREENArea of Minimal Flood Hazard Zone X Area of Undetermined Flood HazardZone D Channel, Culvert, or Storm Sewer Levee, Dike, or Floodwall Cross Sections with 1% Annual Chance 17.5 Water Surface Elevation Coastal Transect Coastal Transect Baseline Profile Baseline Hydrographic Feature Base Flood Elevation Line (BFE) Effective LOMRs Limit of Study Jurisdiction Boundary Digital Data Available No Digital Data Available Unmapped This map complies with FEMA's standards for the use of digital flood maps if it is not void as described below.The basemap shown complies with FEMA's basemapaccuracy standards The flood hazard information is derived directly from theauthoritative NFHL web services provided by FEMA. This mapwas exported on 11/17/2022 at 9:21 PM and does notreflect changes or amendments subsequent to this date andtime. The NFHL and effective information may change orbecome superseded by new data over time. This map image is void if the one or more of the following map elements do not appear: basemap imagery, flood zone labels, legend, scale bar, map creation date, community identifiers, FIRM panel number, and FIRM effective date. Map images for unmapped and unmodernized areas cannot be used for regulatory purposes. Legend OTHER AREAS OF FLOOD HAZARD OTHER AREAS GENERAL STRUCTURES OTHER FEATURES MAP PANELS 8 B 20.2 The pin displayed on the map is an approximatepoint selected by the user and does not representan authoritative property location. 1:6,000 111°2'49"W 45°41'26"N 111°2'12"W 45°41'1"N Basemap: USGS National Map: Orthoimagery: Data refreshed October, 2020 9 Custom Soil Resource Report Soil Map 505912050591605059200505924050592805059320505936050594005059440505912050591605059200505924050592805059320505936050594005059440496600 496640 496680 496720 496760 496800 496840 496600 496640 496680 496720 496760 496800 496840 45° 41' 18'' N 111° 2' 37'' W45° 41' 18'' N111° 2' 25'' W45° 41' 8'' N 111° 2' 37'' W45° 41' 8'' N 111° 2' 25'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 12N WGS84 0 50 100 200 300 Feet 0 20 40 80 120 Meters Map Scale: 1:1,600 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Gallatin County Area, Montana Survey Area Data: Version 26, Aug 30, 2022 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Aug 3, 2009—Sep 1, 2016 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Custom Soil Resource Report 10 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 450C Blackdog-Quagle silt loams, 4 to 8 percent slopes 0.1 0.7% 457A Turner loam, moderately wet, 0 to 2 percent slopes 10.3 90.7% UL Urban land 1.0 8.6% Totals for Area of Interest 11.3 100.0% Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit. A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils. Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each. A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic classes but rather to separate the landscape into landforms or landform segments that have similar use and management requirements. The Custom Soil Resource Report 11 delineation of such segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, however, onsite investigation is needed to define and locate the soils and miscellaneous areas. An identifying symbol precedes the map unit name in the map unit descriptions. Each description includes general facts about the unit and gives important soil properties and qualities. Soils that have profiles that are almost alike make up a soil series. Except for differences in texture of the surface layer, all the soils of a series have major horizons that are similar in composition, thickness, and arrangement. Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity, degree of erosion, and other characteristics that affect their use. On the basis of such differences, a soil series is divided into soil phases. Most of the areas shown on the detailed soil maps are phases of soil series. The name of a soil phase commonly indicates a feature that affects use or management. For example, Alpha silt loam, 0 to 2 percent slopes, is a phase of the Alpha series. Some map units are made up of two or more major soils or miscellaneous areas. These map units are complexes, associations, or undifferentiated groups. A complex consists of two or more soils or miscellaneous areas in such an intricate pattern or in such small areas that they cannot be shown separately on the maps. The pattern and proportion of the soils or miscellaneous areas are somewhat similar in all areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example. An association is made up of two or more geographically associated soils or miscellaneous areas that are shown as one unit on the maps. Because of present or anticipated uses of the map units in the survey area, it was not considered practical or necessary to map the soils or miscellaneous areas separately. The pattern and relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha-Beta association, 0 to 2 percent slopes, is an example. An undifferentiated group is made up of two or more soils or miscellaneous areas that could be mapped individually but are mapped as one unit because similar interpretations can be made for use and management. The pattern and proportion of the soils or miscellaneous areas in a mapped area are not uniform. An area can be made up of only one of the major soils or miscellaneous areas, or it can be made up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example. Some surveys include miscellaneous areas. Such areas have little or no soil material and support little or no vegetation. Rock outcrop is an example. Custom Soil Resource Report 12 Gallatin County Area, Montana 450C—Blackdog-Quagle silt loams, 4 to 8 percent slopes Map Unit Setting National map unit symbol: 56sw Elevation: 4,400 to 5,500 feet Mean annual precipitation: 15 to 19 inches Mean annual air temperature: 39 to 45 degrees F Frost-free period: 90 to 110 days Farmland classification: Farmland of statewide importance Map Unit Composition Blackdog and similar soils:60 percent Quagle and similar soils:30 percent Minor components:10 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Blackdog Setting Landform:Stream terraces Down-slope shape:Linear Across-slope shape:Linear Parent material:Calcareous loess Typical profile A - 0 to 10 inches: silt loam Bt - 10 to 19 inches: silty clay loam Bk - 19 to 60 inches: silt loam Properties and qualities Slope:4 to 8 percent Depth to restrictive feature:More than 80 inches Drainage class:Well drained Capacity of the most limiting layer to transmit water (Ksat):Moderately high (0.20 to 0.57 in/hr) Depth to water table:More than 80 inches Frequency of flooding:None Frequency of ponding:None Calcium carbonate, maximum content:30 percent Available water supply, 0 to 60 inches: High (about 10.9 inches) Interpretive groups Land capability classification (irrigated): 3e Land capability classification (nonirrigated): 3e Hydrologic Soil Group: C Ecological site: R044BB032MT - Loamy (Lo) LRU 01 Subset B Hydric soil rating: No Description of Quagle Setting Landform:Stream terraces Down-slope shape:Linear Across-slope shape:Linear Custom Soil Resource Report 13 Parent material:Silty calcareous loess Typical profile A - 0 to 6 inches: silt loam Bw - 6 to 9 inches: silt loam Bk - 9 to 60 inches: silt loam Properties and qualities Slope:4 to 8 percent Depth to restrictive feature:More than 80 inches Drainage class:Well drained Capacity of the most limiting layer to transmit water (Ksat):Moderately high to high (0.57 to 1.98 in/hr) Depth to water table:More than 80 inches Frequency of flooding:None Frequency of ponding:None Calcium carbonate, maximum content:35 percent Maximum salinity:Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm) Available water supply, 0 to 60 inches: High (about 10.8 inches) Interpretive groups Land capability classification (irrigated): 4e Land capability classification (nonirrigated): 4e Hydrologic Soil Group: B Ecological site: R044BB030MT - Limy (Ly) LRU 01 Subset B Hydric soil rating: No Minor Components Beanlake Percent of map unit:5 percent Landform:Stream terraces, alluvial fans Down-slope shape:Linear Across-slope shape:Linear Ecological site:R044BB030MT - Limy (Ly) LRU 01 Subset B Hydric soil rating: No Bowery Percent of map unit:3 percent Landform:Alluvial fans, stream terraces Down-slope shape:Linear Across-slope shape:Linear Ecological site:R044BB032MT - Loamy (Lo) LRU 01 Subset B Hydric soil rating: No Anceney Percent of map unit:2 percent Landform:Stream terraces Down-slope shape:Linear Across-slope shape:Linear Ecological site:R044BB036MT - Droughty (Dr) LRU 01 Subset B Hydric soil rating: No Custom Soil Resource Report 14 457A—Turner loam, moderately wet, 0 to 2 percent slopes Map Unit Setting National map unit symbol: 56tb Elevation: 4,300 to 5,200 feet Mean annual precipitation: 15 to 19 inches Mean annual air temperature: 39 to 45 degrees F Frost-free period: 90 to 110 days Farmland classification: Prime farmland if irrigated Map Unit Composition Turner and similar soils:85 percent Minor components:15 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Turner Setting Landform:Stream terraces Down-slope shape:Linear Across-slope shape:Linear Parent material:Alluvium Typical profile A - 0 to 6 inches: loam Bt - 6 to 12 inches: clay loam Bk - 12 to 26 inches: clay loam 2C - 26 to 60 inches: very gravelly loamy sand Properties and qualities Slope:0 to 2 percent Depth to restrictive feature:More than 80 inches Drainage class:Well drained Capacity of the most limiting layer to transmit water (Ksat):Moderately high to high (0.57 to 1.98 in/hr) Depth to water table:About 48 to 96 inches Frequency of flooding:None Frequency of ponding:None Calcium carbonate, maximum content:15 percent Maximum salinity:Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm) Available water supply, 0 to 60 inches: Low (about 5.4 inches) Interpretive groups Land capability classification (irrigated): 3e Land capability classification (nonirrigated): 3e Hydrologic Soil Group: B Ecological site: R044BB032MT - Loamy (Lo) LRU 01 Subset B Hydric soil rating: No Custom Soil Resource Report 15 Minor Components Beaverton Percent of map unit:5 percent Landform:Stream terraces, alluvial fans Down-slope shape:Linear Across-slope shape:Linear Ecological site:R044BP818MT - Upland Grassland Hydric soil rating: No Turner Percent of map unit:5 percent Landform:Stream terraces Down-slope shape:Linear Across-slope shape:Linear Ecological site:R044BB032MT - Loamy (Lo) LRU 01 Subset B Hydric soil rating: No Meadowcreek Percent of map unit:5 percent Landform:Stream terraces Down-slope shape:Linear Across-slope shape:Linear Ecological site:R044BP815MT - Subirrigated Grassland Hydric soil rating: No UL—Urban land Map Unit Composition Urban land:100 percent Estimates are based on observations, descriptions, and transects of the mapunit. Custom Soil Resource Report 16 References American Association of State Highway and Transportation Officials (AASHTO). 2004. Standard specifications for transportation materials and methods of sampling and testing. 24th edition. American Society for Testing and Materials (ASTM). 2005. Standard classification of soils for engineering purposes. ASTM Standard D2487-00. Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of wetlands and deep-water habitats of the United States. U.S. Fish and Wildlife Service FWS/OBS-79/31. Federal Register. July 13, 1994. Changes in hydric soils of the United States. Federal Register. September 18, 2002. Hydric soils of the United States. Hurt, G.W., and L.M. Vasilas, editors. Version 6.0, 2006. Field indicators of hydric soils in the United States. National Research Council. 1995. Wetlands: Characteristics and boundaries. Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service. U.S. Department of Agriculture Handbook 18. http://www.nrcs.usda.gov/wps/portal/ nrcs/detail/national/soils/?cid=nrcs142p2_054262 Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classification for making and interpreting soil surveys. 2nd edition. Natural Resources Conservation Service, U.S. Department of Agriculture Handbook 436. http:// www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053577 Soil Survey Staff. 2010. Keys to soil taxonomy. 11th edition. U.S. Department of Agriculture, Natural Resources Conservation Service. http:// www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053580 Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service and Delaware Department of Natural Resources and Environmental Control, Wetlands Section. United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of Engineers wetlands delineation manual. Waterways Experiment Station Technical Report Y-87-1. United States Department of Agriculture, Natural Resources Conservation Service. National forestry manual. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/ home/?cid=nrcs142p2_053374 United States Department of Agriculture, Natural Resources Conservation Service. National range and pasture handbook. http://www.nrcs.usda.gov/wps/portal/nrcs/ detail/national/landuse/rangepasture/?cid=stelprdb1043084 17 United States Department of Agriculture, Natural Resources Conservation Service. National soil survey handbook, title 430-VI. http://www.nrcs.usda.gov/wps/portal/ nrcs/detail/soils/scientists/?cid=nrcs142p2_054242 United States Department of Agriculture, Natural Resources Conservation Service. 2006. Land resource regions and major land resource areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/? cid=nrcs142p2_053624 United States Department of Agriculture, Soil Conservation Service. 1961. Land capability classification. U.S. Department of Agriculture Handbook 210. http:// www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_052290.pdf Custom Soil Resource Report 18 North 3rd Apartments Kimley-Horn and Associates, Inc. Bozeman, MT Preliminary Drainage Report November 2022 Page 4 APPENDIX B: GEOTECH REPORT GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA 1 Table of Contents 1.0 INTRODUCTION............................................................................................................. 3 2.0 PROPOSED STRUCTURE ............................................................................................. 3 3.0 INVESTIGATION ............................................................................................................ 3 3.1 FIELD INVESTIGATION ...................................................................................................... 3 4.0 SITE EVALUATION ....................................................................................................... 4 4.1 SITE DESCRIPTION ........................................................................................................... 4 4.2 SUBSURFACE SOILS AND CONDITIONS ............................................................................. 4 4.3 NATURAL RESOURCES CONSERVATION SERVICE SOIL SURVEY ...................................... 5 4.4 GEOLOGIC SETTING ......................................................................................................... 5 4.5 SEISMICITY ...................................................................................................................... 6 4.5.1 Regional Faults ........................................................................................................... 7 4.5.2 Liquefaction ................................................................................................................ 7 4.5.3 Lateral Spreading ....................................................................................................... 7 4.6 GROUNDWATER ............................................................................................................... 8 5.0 GEOTECHNICAL ANALYSIS ...................................................................................... 8 5.1 ALLOWABLE BEARING CAPACITY .................................................................................... 8 5.2 SETTLEMENT .................................................................................................................... 9 5.2.1 Collapsible Soils ......................................................................................................... 9 5.3 SLOPE STABILITY ........................................................................................................... 10 5.4 LATERAL PRESSURES ..................................................................................................... 10 6.0 RECOMMENDATIONS ................................................................................................ 11 6.1 FOUNDATION ................................................................................................................. 11 6.2 FOUNDATION EXCAVATION ........................................................................................... 11 6.3 STRUCTURAL FILL ......................................................................................................... 12 6.4 FOUNDATION WALL BACKFILL ...................................................................................... 12 6.5 INTERIOR SLABS-ON-GRADE .......................................................................................... 13 6.6 EXTERIOR SLABS-ON-GRADE ........................................................................................ 14 6.7 ASPHALT PAVING IMPROVEMENTS ................................................................................ 14 6.8 SITE GRADING ............................................................................................................... 15 6.9 UNDERGROUND UTILITIES ............................................................................................. 15 6.10 CONSTRUCTION ADMINISTRATION ................................................................................. 16 7.0 CONCLUSIONS ............................................................................................................. 16 8.0 REPORT LIMITATIONS ............................................................................................. 17 9.0 REFERENCES ................................................................................................................ 17 GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA 2 List of Appendices Appendix A – USGS Topographic Map ..................................................................................... A-1 Appendix B – Test Pit Location Map ......................................................................................... A-2 Appendix C – NRCS Web Soil Survey Map .............................................................................. A-3 Appendix D – Geology Maps ..................................................................................................... A-4 Appendix E – Test Pit Logs ........................................................................................................ A-5 Appendix F – Report Limitations ............................................................................................... A-6 GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA 3 1.0 Introduction C&H Engineering and Surveying Inc., (now IMEG) has conducted a geotechnical investigation for the proposed commercial improvements to be constructed on Lots 1 & 2, Block 1 of the Westlakes 4th Addition Subdivision. The subject property is found in the Southeast Quarter of Section 1, Township 2 South, Range 5 East, in Bozeman, Montana. The site location is shown on a United States Geological Survey (USGS) topographic quadrangle map in Appendix A, “USGS Topographic Map.” The scope of services was to conduct a site investigation, evaluate the site, and provide a geotechnical investigation report. The report documents the sites’ soil and groundwater conditions, subsurface soil properties, and provides foundation design and construction recommendations. 2.0 Proposed Structure Detailed plans regarding the proposed structure(s) were not provided at the time of this report. It was understood that 7 multi-family residential structures are planned for construction. This report has assumed that these structures will be a maximum of 3 stories in height and they will utilize crawlspace or slab-on-grade with stem wall foundations. If more than three stories are desired, it is recommended that additional subsurface exploration be conducted. The additional subsurface investigation should include borings to a depth appropriate for the proposed height of construction. It has been assumed that the foundation footings will not be subjected to unusual loading conditions such as eccentric loads. A footing is eccentrically loaded if the load transferred to the footing is not directed through the center of the footing. This creates a bending moment in the footing and results in a non-uniform load transfer to the underlying soil. If any of the foundation footings will be eccentrically loaded, please contact this office so we can appropriately revise our allowable bearing capacity and settlement estimates. 3.0 Investigation The investigation is separated into two parts: the field investigation and the laboratory analysis. While the scope of this project focuses more on the field investigation, we feel it is important to spend time verifying our field observations and conducting tests that will aid in the geotechnical analysis. 3.1 Field Investigation On April 28, 2022, a member of the staff of IMEG visited the site to conduct a subsurface soils investigation and to observe ground features. The subsurface soils investigation consisted of examining seven exploratory test pit excavations. The exploratory test pits were excavated with a CAT 305 mini tracked excavator provided by Burke Construction and Excavation. The test pit locations were chosen based on site topography, accessibility, and the location of underground GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA 4 utilities. The soil profiles revealed by the excavations were logged and visually classified according to ASTM D 2488, which utilizes the nomenclature of the Unified Soil Classification System (USCS). The relative density of each soil layer was estimated based on the amount of effort required to excavate the material, probing of the excavation sidewalls with a rock hammer, and the overall stability of the excavation. Penetration tests were performed on fine grained materials with a static cone penetrometer. Any evidence of seepage or other groundwater conditions were also noted. The locations of the test pits are shown on the Test Pit Location Map included in Appendix B. The subsurface soil conditions encountered in the test pits are described briefly in Section 4.2 and in more detail in Appendix E, “Test Pit Logs.” 4.0 Site Evaluation The site evaluation is based on both the field investigation and research of the sites’ surface geology, soil survey information, and seismic history. 4.1 Site Description The subject property consists of two subdivision lots that have a combined area of 5.87 acres. The subject property is relatively flat with no significant topographical or geological features. The surrounding land use is a mix of commercial, single-family residential, and multi-family residential. 4.2 Subsurface Soils and Conditions The seven test pits (TP) excavated for the field investigation exhibited similar soil profiles. The following paragraphs briefly summarize the subsurface soils and conditions observed in the exploratory test pits excavated for the field investigation. The soil horizons are described as they were encountered in the test pit excavations, starting with the horizon nearest the surface and proceeding with each additional horizon encountered with depth. Please refer to Appendix E, “Test Pit Logs” for more detailed descriptions. The first soil horizon encountered in TP-2, TP-3, TP-5, and TP-6, was undocumented fill. This material was a mix of gravel, cobbles, clay, sand, organics, and woody/construction debris. This material was present to a depth of 0.83 feet below grounds surface (bgs) in TP-2, a depth of 2.33 feet bgs in TP-3 and a depth of 2.0 feet bgs in TP-5 and TP-6. This material must be removed beneath all foundation footings and from beneath all paving improvements. This material may be stockpiled onsite and used for final site grading purposes or for use as foundation wall backfill. The first soil horizon encountered in TP-1, TP-4, and TP-7 was a Silty Clay Organic Soil of low plasticity (OL). This material was black in color, moist, and soft. This material was encountered to depths varying from 1.17 feet bgs to 1.5 feet bgs. Organic soils are highly compressible and are not suitable for foundation support. This material must be removed from beneath all interior and exterior slabs as well as beneath all asphalt paving. This material may be stockpiled onsite GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA 5 and used for final site grading purposes. The second soil horizon encountered in each test pit was a Sandy Lean Clay (CL), which was encountered to depths ranging from 3.5 feet bgs to 5.0 feet bgs. This material was brown in color, moist, and soft to medium stiff in consistency. The third soil horizon encountered in each test pit was a Poorly Graded Gravel with Sand and Cobbles (GP), which was encountered to the end of each excavation, depths varying from 6.5 feet bgs to 7.5 feet bgs. This material was grayish brown in color, moist, and medium dense to dense in consistency. This material appeared to be alluvial in origin. The target bearing material for each structure is the Poorly Graded Gravel with Sand and Cobbles encountered at depths ranging from 3.5 feet bgs to 5.0 feet bgs in the exploratory excavations. 4.3 Natural Resources Conservation Service Soil Survey The Natural Resources Conservation Service (NRCS) Web Soil Survey (WSS) provides soil data and information produced by the National Cooperative Soil Survey. The NRCS has determined the physical characteristics and engineering properties, among other data, of near surface soils across the United States. These data are reviewed against our observations and analysis of the subsurface soils encountered during the field investigation to determine if a correlation is present. If a strong correlation is determined, it is likely that other engineering properties or characteristics described by the NRCS regarding the soils present on the subject property are accurate as well. It should be noted that the NRCS typically only describes the soils located within 5 feet of the surface. NRCS Soil Survey information of the area was taken from the NRCS WSS, Version 2.0. For more information, please visit the NRCS Web Soil Survey on the World Wide Web, at http://websoilsurvey.nrcs.usda.gov/app/. The NRCS Soils Survey identifies the soil near the subject property as 457A – Turner Loam. The NRCS describes the upper soil horizon of this complex as Alluvium. The NRCS also indicates that groundwater is located 48 to 96 inches below the surface. The seven test pits excavated correlate well with the NRCS soils description of the near surface soils. 4.4 Geologic Setting The following paragraphs discuss the geologic setting in the direct vicinity of the subject property. The geologic setting is determined from a review of surface geology maps and reports published by the United States Geological Survey and others that contain the subject property. This information is especially helpful in determining any geologic hazards that may be present in the immediate area (such as landslide deposits) and what types of soil and rock may be present in the area. Additional information regarding the parent material and depositional environment of a given soil type can also sometimes be obtained or inferred from these maps and reports. GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA 6 The local surface geology in the direct vicinity of the subject property was determined from the United States Geological Survey (USGS) Geologic Map of the Bozeman 30' x 60' Quadrangle, Southwest Montana. Please refer to Appendix D, “Geology Maps” for a complete geologic description and map. The USGS Geological Map identifies the surface geology in the vicinity of the subject property as Braid Plain Alluvium, Older. For a narrative description of this formation see the Geologic Map in Appendix D. The subsurface soils encountered during the field investigation correlates well with the USGS description of Braid Plain Alluvium, Older. The Poorly Graded Gravel with Sand and Cobbles contained an abundance of rounded and subrounded gravels and cobbles, as described by the USGS. 4.5 Seismicity The Bozeman area is located in an earthquake zone known as the intermountain seismic belt, which is a zone of earthquake activity that extends from northwest Montana to southern Arizona. In general, this zone is expected to experience moderately frequent, potentially damaging earthquakes. With that in mind, it is important that the structure be designed to withstand horizontal seismic accelerations that may be induced by such an earthquake, as is required by the International Building Code. The USGS provides seismic design parameters for the design of buildings and bridges across the United States. These parameters are based on the National Earthquake Hazards Reduction Program (NEHRP) Recommended Seismic Provisions. The primary intent of the NEHRP Recommended Seismic Provisions is to prevent, for typical buildings and structures, serious injury and life loss caused by damage from earthquake ground shaking. The following seismic design parameters were determined for the subject property using the USGS Seismic Design Application: Approximate site Location: Latitude = 45.6866° N Longitude = 111.0416° W Maximum Considered Earthquake (MCE) Spectral Response Acceleration Parameters: Short Period (SS) = 0.684g 1- Second Period (S1) = 0.214g Site Coefficients and Adjusted MCE Spectral Response Acceleration Parameters: SMS = 0.857 SM1 = 0.465g Design Spectral Response Acceleration Parameters: SDS = 0.571g SD1 = 0.310g GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA 7 The Seismic Site Class is D. 4.5.1 Regional Faults The USGS and Montana Bureau of Mines and Geology (MBMG) have compiled a map of Quaternary Class A faults and earthquake epicenters in western Montana; a Class A fault is one that is associated with at least one large magnitude earthquake within the last 1.6 million years. The earthquake epicenters shown on the map (yellow circles) are associated with earthquakes of magnitude 2.5 or greater, with stars indicating epicenters of earthquakes with a magnitude greater than 5.5. A review of this map indicated that there are 4 Class A faults located within 15 miles of the subject property and 17 earthquake epicenters have been recorded within 10 miles of the subject property. The four faults mapped near the subject property are the Central Park Fault, Bridger Fault, Elk Creek Fault, and the Gallatin Range Fault. Each of these faults is described as a normal fault, indicating that one side of the fault will move downward into the earth relative the other side during an earthquake. The Central Park Fault is located approximately 10 miles northwest of the subject property and runs east to west through the middle of the Gallatin Valley. The Bridger Fault is located approximately 5.3 miles northeast of the subject property and runs along the western side of the Bridger Mountains. The Gallatin Range fault is located approximately 7 miles south of the subject property and runs along the northern border of the Gallatin Range. The Elk Creek Fault is located approximately 13 miles west-southwest of the subject property and extends from Goose Creek (southwest of Gallatin Gateway) to approximately 13 miles northwest of where Norris Road crosses the Madison River. See the Quaternary Fault and Seismicity Map of Western Montana in Appendix D for more information regarding the location of these faults and nearby earthquake epicenters. 4.5.2 Liquefaction In general terms, liquefaction is defined as the condition when saturated, loose, silt or fine sand-type soils lose their support capabilities due to the development of excessive pore water pressure, which can develop during a seismic event. Loose silty sandy soils, if located below the groundwater table, have the potential to liquefy during a major seismic event. Our subsurface investigation did not encounter any loose silt or sand horizons within the depth of excavation. It is our opinion that the potential for differential settlement resulting from liquefaction during a moderate seismic event is low. 4.5.3 Lateral Spreading Lateral spreading is the slow-to-rapid lateral extensional movement of rock or soil masses. The primary cause of lateral spreading is liquefaction, usually induced by an earthquake, and subsequent flowage of a weak soil layer within a slope. The potential for, and magnitude of, lateral spreading is dependent upon many conditions, including the presence of a relatively thick, continuous, potentially liquefiable sand or sensitive clay layer, and the slope of the site. GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA 8 As stated previously, our subsurface investigation did not reveal any loose silt or sand horizons, nor any potential slip planes within the depth of excavation. Therefore, it is our opinion that any structure built on the subject property is at a low risk of sustaining damage due to lateral spreading. 4.6 Groundwater Groundwater or seepage was not observed within any of the exploratory test pits excavated during the site visit. Groundwater is not anticipated to be encountered within the excavation for the structure. It is possible that a perched groundwater table may occur seasonally during the snowmelt. The most likely time this would occur would be in the spring. Please note that our subsurface investigation is not a detailed groundwater study, and groundwater conditions may change dramatically due to conditions that are out of our control. Our assessment of the groundwater conditions is based on the conditions observed within the exploratory test pits on the day of the excavation, our general experience in the project area, and any available literature regarding groundwater conditions in the vicinity of the subject property. If more detailed knowledge of the seasonally high groundwater elevation across the subject property is desired, it is recommended that groundwater monitoring wells be installed and checked weekly from the early spring to late summer months. 5.0 Geotechnical Analysis The geotechnical analysis takes into account the field investigation and site evaluation to make engineering recommendations pertaining to bearing capacity, lateral pressures, settlement, and slope stability. 5.1 Allowable Bearing Capacity The allowable bearing capacity of a soil is defined as the maximum pressure that can be permitted on a foundation soil, giving consideration to all pertinent factors (such as settlement and seismic considerations), with adequate safety against rupture of the soil mass or movement of the foundation of such magnitude that the structure is impaired. The allowable bearing capacity is determined from the geotechnical analysis, the field investigation, available soil and geology information, and our experience in the project area. Based on the site investigation, it recommended that all loads from the proposed structures bear on the Poorly Graded Gravel with Sand and Cobbles. All foundation footings shall be dimensioned for an allowable bearing capacity of 2,500 pounds per square foot (psf). The allowable bearing capacity may be increased by 1/3 for short term loading conditions such as those from wind or seismic forces. GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA 9 5.2 Settlement While the soil at the site may be able to physically support the footings, it is also important to analyze the possible settlement of the structure. In many cases, settlement determines the allowable bearing capacity. When a soil deposit is loaded by a structure, deformations within the soil deposit will occur. The total vertical deformation of the soil at the surface is called total settlement. Total settlement is made up of two components: elastic settlement and consolidation settlement. Elastic settlement is the result of soil particles rearranging themselves into a denser configuration due to a load being imposed on them and usually occurs during the construction process and shortly after. Consolidation settlement occurs more slowly and over time as water within the pore spaces of a soil are forced out and the soil compresses as the stress from the load is transferred from the water molecules to the soil particles. Consolidation settlement is more of a concern with fine-grained soils with low permeability and high in-situ moisture contents. The degree of settlement is a function of the type of bearing material, the bearing pressure of the foundation elements, local groundwater conditions, and in some cases determines the allowable bearing capacity for a structures’ footings. In addition to analyzing total settlement, the potential for differential settlement must also be considered. Differential settlement occurs in soils that are not homogeneous over the length of the foundation or in situations where the foundation rests on cut and fill surfaces. If the foundation rests on structural fill overlaying properly prepared soils with rock, differential settlement is expected to be well within tolerable limits. Areas that have significantly more fill under the foundation footings (four feet of more) create greater potential for differential settlement. In these cases, the structural fill must be installed properly and tested frequently. Compaction efforts and structural fill consistence are vital in minimizing differential settlement. For this project it is not anticipated that significant quantities of structural fill will be required. For this project, total settlement is expected to consist of elastic settlement. A settlement analysis based on conservative soil parameter estimates, the allowable bearing capacity recommended in Section 5.1, and the assumption that all recommendations made in this report are properly adhered to, indicates the total and differential settlement are expected to be ½-inch or less. Structures of the type assumed can generally tolerate this amount of movement, however, these values should be checked by a structural engineer to verify that they are acceptable. Please note that the settlement estimates are based on loads originating from the proposed structure. If additional loads are introduced, such as the placement of large quantities of fill, our office should be contacted to re-evaluate the settlement estimates and provide a written response. 5.2.1 Collapsible Soils Collapsible soils are soils that compact and collapse after wetting. The soil particles are originally loosely packed and barely touch each other before moisture infiltrates into the soil. As water infiltrates into the soil, it reduces the friction between the soil particles and allows them to slip past each other and become more tightly packed, often resulting in a radical reduction in GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA 10 volume; this radical reduction in volume can occur without any additional loading of the soil. Another term for collapsible soils is "hydrocompactive soils" because they compact after water is added. The amount of collapse depends on how loosely the particles are packed originally and the thickness of the soil layer susceptible to collapse. Soils with dry densities of less than 80 pounds per cubic foot (pcf), generally silts deposited by the wind, are considered to be susceptible to collapse. Soils with dry unit weights greater than 90 pcf are not considered susceptible to collapse. Using this correlation, it is our opinion that the proposed structures are not at risk of sustaining damage due to collapsible soils. 5.3 Slope Stability The subject property is relatively flat with no significant topographical or geological features. It is our opinion that the risk of localized slope instability for the subject property is very low. 5.4 Lateral Pressures It is recommended that all foundation and retaining walls be backfilled with well-draining granular material. Well-draining granular backfill has a more predictable behavior in terms of the lateral earth pressure exerted on the foundation or retaining wall and will not generate expansive related forces. If backfill containing significant quantities of clayey material is used, the seepage of water into the backfill could potentially generate horizontal swelling pressures well above at-rest values. Additionally, seepage into a clayey backfill material will also cause significant hydrostatic pressures to build up against the foundation wall due to the low permeability of clay soils and will make the backfill susceptible to frost action. Lateral pressures imposed upon foundation and retaining walls due to wind, seismic forces, and earth pressures may be resisted by the development of passive earth pressures and/or frictional resistance between the base of the footings and the supporting soils. If a foundation or retaining wall is restrained from moving, the lateral earth pressure exerted on the wall is called the at-rest earth pressure. If a foundation or retaining wall is allowed to tilt away from the retained soil, the lateral earth pressure exerted on the wall is called the active earth pressure. Passive earth pressure is the resistance pressure the foundation or retaining wall develops due to the wall being pushed laterally into the earth on the opposite side of the retained soil. Each of these pressures is proportional to the distance below the earth surface, the unit weight of the soil, and the shear strength properties of the soil. Subsurface walls that are restrained from moving at the top, such as basement walls, are recommended to be designed for an equivalent fluid pressure of 62 pounds per cubic foot (at-rest pressure); the equivalent fluid pressure is the product of the retained soils unit weight and its coefficient of active or at-rest earth pressure. Any subsurface walls that are allowed to move away from the restrained soil, such as cantilevered retaining walls, are recommended to be designed for an equivalent fluid pressure of 39 pounds per cubic foot (active pressure). For passive pressures, an equivalent fluid pressure of 350 pcf is recommended, and the coefficient of friction between cast-in-place concrete and the native Poorly Graded Gravel with Sand and Cobbles is estimated to be 0.5. GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA 11 These recommended values were calculated assuming a near horizontal backfill and that the native Sandy Lean Clay and/or the Poorly Graded Gravel with Sand and Cobbles would be used as backfill. Also, please note that these design pressures do not include a factor of safety and are for static conditions, they do not account for additional forces that may be induced by seismic loading. 6.0 Recommendations The following recommendations are given as guidance to assure for a safe and effective foundation for the proposed structure. These recommendations are determined by the geotechnical analysis, code requirements, our experience, and local construction practices. 6.1 Foundation Based on the site evaluation and geotechnical analysis it will be acceptable to utilize a crawl space or slab-on-grade with stem wall foundation. Please find the following as general recommendations for all foundation elements: • In order to keep the footing out of the active frost zone it is recommended that the bottom of all footing elevations be a minimum of 48 inches below finished grade. • The target bearing material is the Poorly Graded Gravel with Sand and Cobbles encountered at depths varying from 3.5 feet bgs to 5.0 feet bgs. • The foundation footings may be dimensioned for an allowable bearing capacity of 2,500 psf. • The subgrade must remain in a dry condition throughout construction of the foundation elements. • If construction takes place during the colder months of the year, the subgrade must be protected from freezing. This may require the use of insulating blankets and/or ground heaters. 6.2 Foundation Excavation In general, the excavation for the foundation must be level, uniform, and end within the Poorly Graded Gravel with Sand and Cobbles. If any soft spots, overly saturated soils, or boulders are encountered, they will need to be removed and backfilled with structural fill. The excavation width must extend a minimum of one footing width from the outer edges of the footings. For best results, a smooth bucket should be used to complete the excavation. The subgrade must be kept dry and from freezing throughout construction. At no time should surface water runoff be allowed to flow into and accumulate within the excavation for the foundation elements. If necessary, a swale or berm should be temporarily constructed to reroute GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA 12 all surface water runoff away from the excavation. Excavation should not proceed during large precipitation events. If any of the foundation footings are found to be located on a test pit, the area will need to be excavated down to the full depth of the test pit and structural fill be placed and compacted in lifts to bring the area back up to the desired grade. 6.3 Structural Fill Structural fill is defined as all fill that will ultimately be subjected to structural loadings, such as those imposed by footings, floor slabs, pavements, etc. The native Poorly Graded Gravel with Sand and Cobbles may be used as structural fill provided any cobbles larger than 6 inches in size are removed. Structural fill may also be imported for this project if it is required. Imported structural fill is recommended to be a well graded gravel with sand that contains less than 15 percent of material that will pass a No. 200 sieve and that has a maximum particle size of 3 inches. Also, the fraction of material passing the No. 40 sieve shall have a liquid limit not exceeding 25 and a plasticity index not exceeding 6, and the gravel and sand particles need to be made up of durable rock materials that will not degrade due to moisture or the compaction effort; no shale or mudstone fragments should be present. Structural fill must be placed in lifts no greater than 12 inches (uncompacted thickness) and be uniformly compacted to a minimum of 97 percent of its maximum dry density, as determined by ASTM D698. Typically, the structural fill must be moisture conditioned to within + 2 percent of the materials optimum moisture content to achieve the required density. It is recommended that the structural fill be compacted with a large vibrating smooth drum roller. Please note that if a moisture-density relationship test (commonly referred to as a proctor) needs to be performed for a proposed structural fill material to determine its maximum dry density in accordance with ASTM D698, a sample of the material must be delivered to this office a minimum of three full working days prior the density testing being needed. Achieving proper compaction is imperative, as it will ensure no additional settlement of the structure occurs. Therefore, it is required that IMEG verifies proper compaction of all structural fill lifts. 6.4 Foundation Wall Backfill Approved backfill material should be placed and compacted between the foundation wall and the edge of the excavation. The soils encountered within the exploratory excavations, except for the Organic Soil and Undocumented Fill, may be used as backfill against the foundation walls. Structural fill is recommended for foundation wall backfill in all areas that will be supporting concrete slabs-on-grade or other paving improvements. The structural fill shall meet the requirements of Section 6.3. The backfill shall be placed in uniform lifts and be compacted to a minimum of 95 percent of the materials maximum dry density, as determined by ASTM D698. The foundation wall backfill GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA 13 will need to be compacted with either walk behind compaction equipment or hand operated compaction equipment in order to avoid damaging the foundation walls. If walk behind compaction equipment is used lifts should not exceed 8-inches (loose thickness) and if hand operated compaction equipment is used lifts should not exceed 4-inches (loose thickness). A 6-to-12-inch cap of low permeability topsoil should be placed, compacted, and appropriately graded above the approved foundation wall backfill on the outside of the foundation wall where there are no pavements. This will effectively cap the backfill and redirect surface water away from the structure. Please note, if the foundation wall backfill is not compacted properly it will settle and positive drainage away from the foundation will not be maintained. 6.5 Interior Slabs-on-Grade In preparation for any interior slabs-on-grade, the excavation must continue through any overlying topsoil and/or undocumented fill to a minimum of 6 inches below the proposed bottom of slab elevation. If required, structural fill can then be placed and compacted to 6 inches below the bottom of slab elevation. For all interior concrete slabs-on-grade, preventative measures must be taken to stop moisture from migrating upwards through the slab. Moisture that migrates upwards through the concrete slab can damage floor coverings such as carpet, hardwood and vinyl, in addition to causing musty odors and mildew growth. Moisture barriers will need to be installed to prevent water vapor migration and capillary rise through the concrete slab. Capillarity is the result of the liquid property known as surface tension, which arises from an imbalance of cohesive and adhesive forces near the interface between different materials. With regards to soils, surface tension arises at the interface between groundwater and the mineral grains and air of a soil. The height of capillary rise within a given soil is controlled by the size of the pores between the soil particles and not the size of the soil particles directly. Soils that have small pore spaces experience a higher magnitude of capillary rise than soils with large pore spaces. Typically, soils composed of smaller particles (such as silt and clay) have smaller pore spaces. In order to prevent capillary rise through the concrete slab-on-grade it is recommended that 6 inches of ¾-inch washed rock (containing less than 10 percent fines) be placed and compacted once the excavation for the slab is complete. The washed rock has large pore spaces between soil particles and will act as a capillary break, preventing groundwater from migrating upwards towards the bottom of the slab. Water vapor is currently understood to act in accordance with the observed physical laws of gases, which state that the water vapor will travel from an area of higher concentration to that of a lower concentration until equilibrium is achieved. Because Earth contains large quantities of liquid water, water vapor is ubiquitous in Earth’s atmosphere, and, as a result, also in soils located above the water table (referred to as the vadose zone). Typically, the concentration of water vapor in the vadose zone is greater than that inside the residence. This concentration difference may result in an upward migration of water vapor from the vadose zone through the GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA 14 concrete slab-on-grade and into the building. In order to prevent this upward migration of water vapor through the slab, it is recommended that a 15-mil extruded polyolefin plastic that complies with ASTM E1745 (such as a Stego Wrap 15-mil Vapor Barrier) be installed. The vapor barrier should be pulled up at the sides and secured to the foundation wall or footing. Care must be taken during and after the installation of the vapor barrier to avoid puncturing the material, and all joints are to be sealed per the manufacture’s recommendations. Once the excavation for the interior slab-on-grade is completed as described in the first paragraph of this section, and the ¾ inch washed rock and moisture barriers have been properly installed, it will be acceptable to form and cast the steel reinforced concrete slab. It is recommended that interior concrete slabs-on-grade have a minimum thickness of 4 inches, except garage slabs have a recommended minimum thickness of 6 inches, unless directed otherwise by a structural engineer. 6.6 Exterior Slabs-on-Grade For exterior areas to be paved with concrete slabs, it is recommended that, at a minimum, the topsoil and any organics be removed. The subgrade soils then need to be compacted to an unyielding condition. Then for non-vehicular traffic areas, a minimum of 6 inches of ¾-inch minus rock needs to be placed, and 4 inches of 4000 pounds per square inch concrete placed over the ¾-inch minus rock. For areas with vehicular traffic, a minimum of 9 inches of ¾-inch minus rock should be placed, followed by 6 inches of 4000 pounds per square inch concrete. Exterior slabs that will be located adjacent to the foundation walls need to slope away from the structure at a minimum grade of 2 percent and should not be physically connected to the foundation walls. If they are connected, any movement of the exterior slab will be transmitted to the foundation wall, which may result in damage to the structure. Additionally, any exterior columns (such as those for patios or decks) should not bear on exterior slabs. Any movement of the exterior slab will be transmitted to the column, which may also result in damage. If concrete slabs are to be placed on foundation wall backfill, the backfill must be compacted to a minimum of 95 percent of its maximum dry density, as determined by ASTM D698. It is recommended the backfill be placed in uniform lifts and compacted as described in Section 6.4. 6.7 Asphalt Paving Improvements For areas to be paved with asphalt, it is recommended that, as a minimum, the topsoil and any organics be removed. The native subgrade then needs to be rolled at ± 2 percent of its optimum moisture content to a minimum of 95 percent of its maximum dry density, as determined by ASTM D698. Next a 12-inch layer of compacted 6-inch minus gravel needs to be placed, followed by a 6-inch layer of compacted 1-inch minus road mix. Both gravel courses must be compacted at ± 3 percent of their optimum moisture content to a minimum of 95 percent of their maximum dry densities. A 3-inch-thick layer of asphalt pavement can then be placed and compacted over this cross-section. GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA 15 If asphalt paving is to be placed on foundation wall backfill, the backfill must be compacted to a minimum of 95 percent of its maximum dry density, as determined by ASTM D698. It is recommended the backfill be placed in uniform lifts and compacted as described in Section 6.4. 6.8 Site Grading Surface water should not be allowed to accumulate and infiltrate the soil near the foundation. Proper site grading will ensure surface water runoff is directed away from the foundation elements and will aid in the mitigation of excessive settlement. Please find the following as general site grading recommendations: • In unpaved areas, finished grade must slope away from the building a minimum of 5 percent within the first 10 feet, in order to quickly drain ground surface and roof runoff away from the foundation walls. In areas paved with concrete slabs or asphalt, finished grade must slope away from the structure at a minimum grade of 2 percent. Please note that in order to maintain these slopes, it is imperative that any backfill placed against the foundation walls be compacted properly. If the backfill is not compacted properly, it will settle and positive drainage away from the structure will not be maintained. • Permanent sprinkler heads for lawn care should be located a sufficient distance from the structure to prevent water from draining toward the foundation or saturating the soils adjacent to the foundation. • Rain gutter down spouts are to be placed in such a manner that surface water runoff drains away from the structure. • All roads, walkways, and architectural land features must properly drain away from all structures. Special attention should be made during the design of these features to not create any drainage obstructions that may direct water towards or trap water near the foundation. 6.9 Underground Utilities The onsite soils contain clayey material. Clayey material can be moderately corrosive to metallic conduits. We recommended specifying non-corrosive materials or providing corrosion protection unless additional tests are performed to verify the onsite soils are not corrosive. It is recommended that ¾-inch minus gravel be used as a bedding material, where bedding material is defined as all material located within 6 inches of the utility pipe(s). The bedding material should be thoroughly compacted around all utility pipes. Trench backfill shall be compacted to a minimum of 95 percent of its maximum dry density in landscaped areas and a minimum of 97 percent of its maximum dry density beneath foundation footings. Backfilling around and above utilities should meet the requirements of Montana Public Works Standard Specifications. GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA 16 6.10 Construction Administration The foundation is a vital element of a structure; it transfers all of the structures dead and live loads to the native soil. It is imperative that the recommendations made in this report are properly adhered to. A representative from IMEG should observe the construction of any foundation or drainage elements recommended in this report and should verify proper compaction has been achieved in all structural fill lifts. The recommendations made in this report are contingent upon our involvement. If the soils encountered during the excavation differ than those described in this report or any unusual conditions are encountered, our office should be contacted immediately to examine the conditions and re-evaluate our recommendations and provide a written response. If construction and site grading take place during cold weather, it is recommended that approved winter construction practices be observed. All snow and ice shall be removed from cut and fill areas prior to site grading taking place. No fill should be placed on soils that are frozen or contain frozen material. No frozen soils can be used as fill under any circumstances. Additionally, Concrete should not be placed on frozen soils and should meet the temperature requirements of ASTM C 94. Any concrete placed during cold weather conditions shall be protected from freezing until the necessary compressive strength has been attained. Once the footings are placed, frost shall not be permitted to extend below the foundation footings, as this could heave and crack the foundation footings and/or foundation walls. It is the responsibility of the contractor to provide a safe working environment with regards to excavations on the site. All excavations should be sloped or shored in the interest of safety and in accordance with local and federal regulations, including the excavation and trench safety standards provided by the Occupational Safety and Health Administration (OSHA). According to OSHA regulations (29 CFR 1926 Subpart P Appendix A) the subsurface soils encountered in the test pit excavations can be generally classified as Type C. For Type C soils, OSHA regulations state that cut slopes shall be no steeper than 1.5H:1V for excavations less than 20 feet deep. A trench box may also be used, provided the system extends at least 18 inches above the top of the trench walls. Please understand the preceding OSHA soil classification is provided for planning purposes only and the actual classification of the onsite soils will need to be determined by the contractor onsite during excavation. 7.0 Conclusions The soils present at the site will be adequate to support the proposed structure, provided the recommendations made in this report are properly followed. Please find the following recommendations as particularly crucial: • In order to keep the footing out of the active frost zone it is recommended that the bottom of all footing elevations be a minimum of 48 inches below finished grade. • The target bearing material is the Poorly Graded Gravel with Sand and Cobbles encountered at depths varying from 3.5 feet bgs to 5.0 feet bgs. GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA 17 • The foundation footings may be dimensioned for an allowable bearing capacity of 2,500 psf. • The subgrade must remain in a dry condition throughout construction of the foundation elements. • If construction takes place during the colder months of the year, the subgrade must be protected from freezing. This may require the use of insulating blankets and/or ground heaters. 8.0 Report Limitations This report is for the exclusive use of DevCo, LLC. In the absence of our written approval, we make no representation and assume no responsibility to other parties regarding the use of this report. The recommendations made in this report are based upon data obtained from test pits excavated at the locations indicated on the attached Test Pit Location Map. It is not uncommon that variations will occur between these locations, the nature and extent of which will not become evident until additional exploration or construction is conducted. These variations may result in additional construction costs, and it is suggested that a contingency be provided for this purpose. If the soils encountered during the excavation differ than those described in this report or any unusual conditions are encountered, our office should be contacted immediately to examine the conditions and re-evaluate our recommendations and provide a written response. This report is applicable to the subject property only and is not applicable to other construction sites. Under no circumstances shall a portion of this report be removed or be used independently of the rest of the document, this report is applicable as a full document only. The preparation of this report has been performed in a manner that is consistent with the level and care currently practiced by professionals in this area under similar budget and time restraints. No warranty, expressed or implied, is made. Please review Appendix F, “Report Limitations.” This Appendix has been prepared to relay the risks associated with this report. 9.0 References Das, Braja M., “Principles of Foundation Engineering,” 5th ed., Pacific Grove, CA, Brooks/Cole- Thompson Learning, 2004. Day, Robert W., “Foundation Engineering Handbook,” McGraw-Hill, 2006. International Code Council, Inc., “2018 International Building Code (IBC),” International Code Council, Inc., 2018. Kehew, Alan, “Geology for Engineers and Environmental Scientists,” 3rd ed., Prentice Hall, 2006. GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA 18 Das, Braja M., “Principles of Geotechnical Engineering,” 3rd ed., Boston, MA, PWS Publishing Company, 1994. National Earthquake Hazards Reduction Program Recommended Seismic Provisions for New Buildings and Other Structures, FEMA P-1050-2, 2015. GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA Appendix A USGS Topographic Map GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA Appendix B Test Pit Location Map GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA Appendix C NRCS Web Soil Survey Map (APPROXIMATE)(APPROXIMATE)LEGENDNatural Resources Conservation Service Web Soil SurveySource: Natural Resources Conservation Service, "Web Soil Survey - Version 25," September 2, 2021, United States Department of Agriculture, <http://websoilsurvey.nrcs.usda.gov/app/>Aerial Photo Date = August 3, 2009 - September 1, 2016Turner Loam described as alluvium with a typical soil profile of Loam (0-6 Inches), Clay Loam (6-26 inches), and Very Gravelly Loamy Sand(26-60 inches). Depth to groundwater is listed as 48 to 96 inches. GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA Appendix D Geology Maps (APPROXIMATE)(APPROXIMATE)LEGENDBraid plain alluvium, older than Qab (Pleistocene)Rounded to well-rounded, dominantly cobble gravel with clasts as large as boulders, and sand, silt, and clay; mostly composed of clasts of Archean metamorphic rock, anddark-colored volcanic rock, with subordinate Paleozoic limestone and Proterozoic Belt rocks. Clast lithologies in general order of decreasing abundance include Precambrianmetamorphic rocks, mafic volcanic rocks, dacite(?) porphyry, quartzite, sandstone, limestone, and chert. A well in this unit indicates a thickness of 9 m (30 ft) of alluviumoverlying Tertiary deposits.Alluvial-fan deposit, older than Qaf (Pleistocene)Light brown, gray, and locally reddish gray, angular and subangular, locally derived gravel in a coarse sand and granule matrix. Clast size ranges from pebble to smallboulder. Fan morphology dissected. Maximum thickness probably about 45 m (150 ft).Source: Vuke, Susan M., Lonn, Jeffrey D., Berg, Richard B., & Schmidt, Christopher J., "Geologic Map of the Bozeman 30' x 60' Quadrangle, Southwestern Montana," MBMG, Open File Report 648, 2014.Braid Plain Alluvium, OlderApproximate Site LocationAlluvial Fan Deposit, OlderGEOLOGIC MAP OF THE BOZEMAN 30' X 60' QUADRANGLE (APPROXIMATE)(APPROXIMATE)LEGENDQuarternary Fault & Seismicity Map of Western MontanaSource: Stickney, Michael C., Holler, Kathleen M., Machette Michael N., "Quaternary Faults and Seismicity in Western Montana ," MBMG, Special Publication No. 114, 2000.Class A Faults are associated with at least 1 large magnitude earthquake within the last 1.6 million years. GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA Appendix E Test Pit Logs OL CL GP 1.2 3.5 7.0 0 TO 1.17 FEET: SILTY CLAY ORGANIC SOIL; (OL); dark brown to black; moist; soft. 1.17 TO 3.5 FEET: SANDY LEAN CLAY; (CL); brown; moist; medium plasticity; soft to medium stiff; approximately 30 percent fine to coarse grain sand; approximately 70 percent clayey fines. 3.5 TO 7 FEET: POORLY GRADED GRAVEL WITH SAND; (GP); brown; moist; mediumdense to dense; approximately 60 percent subangular gravels; approximately 30 percent fine to coarse grain sand; approximately 10 percent clayey fines. Bottom of test pit at 7.0 feet. NOTES GROUND ELEVATION LOGGED BY Noah J. Schaible, E.I. EXCAVATION METHOD CAT 305 Mini Tracked Excavator EXCAVATION CONTRACTOR Burke Construction and Excavation GROUND WATER LEVELS: DATE STARTED 4/28/22 COMPLETED 4/28/22 AT TIME OF EXCAVATION --- AFTER EXCAVATION --- AT END OF EXCAVATION ---DEPTH(ft)0.0 2.5 5.0 SAMPLE TYPENUMBERPAGE 1 OF 1 TEST PIT NUMBER TP 1 PROJECT NUMBER 220290 CLIENT DevCo, LLC PROJECT LOCATION Lots 1-2, Westlake 4th Addition PROJECT NAME Geotechnical Investigation GENERAL BH / TP / WELL - GINT STD US.GDT - 6/10/22 10:52 - \\FILES\CORPORATE\OFFICES\BOZEMAN\CANDH\OFFICEDATA\CH\22\220290\GEOTECH\TEST PIT LOGS (220290).GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION CL GP 0.8 4.5 7.5 0 TO 0.83 FEET: UNDOCUMENTED FILL; dark brown to black; moist; soft; consisted of a varying mixture of gravel, sand, clay, organics, and various construction debris. 0.83 TO 4.5 FEET: SANDY LEAN CLAY; (CL); brown; moist; medium plasticity; soft to medium stiff; approximately 30 percent fine to coarse grain sand; approximately 70 percent clayey fines. 4.5 TO 7.5 FEET: POORLY GRADED GRAVEL WITH SAND; (GP); brown; moist; medium dense to dense; approximately 60 percent subangular gravels; approximately 30 percent fine to coarse grain sand; approximately 10 percent clayey fines. Bottom of test pit at 7.5 feet. NOTES GROUND ELEVATION LOGGED BY Noah J. Schaible, E.I. EXCAVATION METHOD CAT 305 Mini Tracked Excavator EXCAVATION CONTRACTOR Burke Construction and Excavation GROUND WATER LEVELS: DATE STARTED 4/28/22 COMPLETED 4/28/22 AT TIME OF EXCAVATION --- AFTER EXCAVATION --- AT END OF EXCAVATION ---DEPTH(ft)0.0 2.5 5.0 7.5 SAMPLE TYPENUMBERPAGE 1 OF 1 TEST PIT NUMBER TP 2 PROJECT NUMBER 220290 CLIENT DevCo, LLC PROJECT LOCATION Lots 1-2, Westlake 4th Addition PROJECT NAME Geotechnical Investigation GENERAL BH / TP / WELL - GINT STD US.GDT - 6/10/22 10:52 - \\FILES\CORPORATE\OFFICES\BOZEMAN\CANDH\OFFICEDATA\CH\22\220290\GEOTECH\TEST PIT LOGS (220290).GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION CL GP 2.3 5.0 7.5 0 TO 2.33 FEET: UNDOCUMENTED FILL; dark brown to black; moist; soft; consisted of a varying mixture of gravel, sand, clay, organics, and various construction debris. 2.33 TO 5 FEET: SANDY LEAN CLAY; (CL); brown; moist; medium plasticity; soft tomedium stiff; approximately 30 percent fine to coarse grain sand; approximately 70 percentclayey fines. 5 TO 7.5 FEET: POORLY GRADED GRAVEL WITH SAND; (GP); brown; moist; medium dense to dense; approximately 60 percent subangular gravels; approximately 30 percent fine to coarse grain sand; approximately 10 percent clayey fines. Bottom of test pit at 7.5 feet. NOTES GROUND ELEVATION LOGGED BY Noah J. Schaible, E.I. EXCAVATION METHOD CAT 305 Mini Tracked Excavator EXCAVATION CONTRACTOR Burke Construction and Excavation GROUND WATER LEVELS: DATE STARTED 4/28/22 COMPLETED 4/28/22 AT TIME OF EXCAVATION --- AFTER EXCAVATION --- AT END OF EXCAVATION ---DEPTH(ft)0.0 2.5 5.0 7.5 SAMPLE TYPENUMBERPAGE 1 OF 1 TEST PIT NUMBER TP 3 PROJECT NUMBER 220290 CLIENT DevCo, LLC PROJECT LOCATION Lots 1-2, Westlake 4th Addition PROJECT NAME Geotechnical Investigation GENERAL BH / TP / WELL - GINT STD US.GDT - 6/10/22 10:52 - \\FILES\CORPORATE\OFFICES\BOZEMAN\CANDH\OFFICEDATA\CH\22\220290\GEOTECH\TEST PIT LOGS (220290).GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION OL CL GP 1.5 5.0 7.5 0 TO 1.5 FEET: SILTY CLAY ORGANIC SOIL; (OL); dark brown to black; moist; soft. 1.5 TO 5 FEET: SANDY LEAN CLAY; (CL); brown; moist; medium plasticity; soft to medium stiff; approximately 30 percent fine to coarse grain sand; approximately 70 percent clayeyfines. 5 TO 7.5 FEET: POORLY GRADED GRAVEL WITH SAND; (GP); brown; moist; medium dense to dense; approximately 60 percent subangular gravels; approximately 30 percent fine to coarse grain sand; approximately 10 percent clayey fines. Bottom of test pit at 7.5 feet. NOTES GROUND ELEVATION LOGGED BY Noah J. Schaible, E.I. EXCAVATION METHOD CAT 305 Mini Tracked Excavator EXCAVATION CONTRACTOR Burke Construction and Excavation GROUND WATER LEVELS: DATE STARTED 4/28/22 COMPLETED 4/28/22 AT TIME OF EXCAVATION --- AFTER EXCAVATION --- AT END OF EXCAVATION ---DEPTH(ft)0.0 2.5 5.0 7.5 SAMPLE TYPENUMBERPAGE 1 OF 1 TEST PIT NUMBER TP 4 PROJECT NUMBER 220290 CLIENT DevCo, LLC PROJECT LOCATION Lots 1-2, Westlake 4th Addition PROJECT NAME Geotechnical Investigation GENERAL BH / TP / WELL - GINT STD US.GDT - 6/10/22 10:52 - \\FILES\CORPORATE\OFFICES\BOZEMAN\CANDH\OFFICEDATA\CH\22\220290\GEOTECH\TEST PIT LOGS (220290).GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION CL GP 2.0 5.0 7.5 0 TO 2 FEET: UNDOCUMENTED FILL; dark brown to black; moist; soft; consisted of a varying mixture of gravel, sand, clay, organics, and various construction debris. 2 TO 5 FEET: SANDY LEAN CLAY; (CL); brown; moist; medium plasticity; soft to medium stiff; approximately 30 percent fine to coarse grain sand; approximately 70 percent clayey fines. 5 TO 7.5 FEET: POORLY GRADED GRAVEL WITH SAND; (GP); brown; moist; medium dense to dense; approximately 60 percent subangular gravels; approximately 30 percent fine to coarse grain sand; approximately 10 percent clayey fines. Bottom of test pit at 7.5 feet. NOTES GROUND ELEVATION LOGGED BY Noah J. Schaible, E.I. EXCAVATION METHOD CAT 305 Mini Tracked Excavator EXCAVATION CONTRACTOR Burke Construction and Excavation GROUND WATER LEVELS: DATE STARTED 4/28/22 COMPLETED 4/28/22 AT TIME OF EXCAVATION --- AFTER EXCAVATION --- AT END OF EXCAVATION ---DEPTH(ft)0.0 2.5 5.0 7.5 SAMPLE TYPENUMBERPAGE 1 OF 1 TEST PIT NUMBER TP 5 PROJECT NUMBER 220290 CLIENT DevCo, LLC PROJECT LOCATION Lots 1-2, Westlake 4th Addition PROJECT NAME Geotechnical Investigation GENERAL BH / TP / WELL - GINT STD US.GDT - 6/10/22 10:52 - \\FILES\CORPORATE\OFFICES\BOZEMAN\CANDH\OFFICEDATA\CH\22\220290\GEOTECH\TEST PIT LOGS (220290).GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION CL GP 2.0 3.8 7.0 0 TO 2 FEET: UNDOCUMENTED FILL; dark brown to black; moist; soft; consisted of a varying mixture of gravel, sand, clay, organics, and various construction debris. 2 TO 3.83 FEET: SANDY LEAN CLAY; (CL); brown; moist; medium plasticity; soft to medium stiff; approximately 30 percent fine to coarse grain sand; approximately 70 percent clayey fines. 3.83 TO 7 FEET: POORLY GRADED GRAVEL WITH SAND; (GP); brown; moist; medium dense to dense; approximately 60 percent subangular gravels; approximately 30 percent fine to coarse grain sand; approximately 10 percent clayey fines. Bottom of test pit at 7.0 feet. NOTES GROUND ELEVATION LOGGED BY Noah J. Schaible, E.I. EXCAVATION METHOD CAT 305 Mini Tracked Excavator EXCAVATION CONTRACTOR Burke Construction and Excavation GROUND WATER LEVELS: DATE STARTED 4/28/22 COMPLETED 4/28/22 AT TIME OF EXCAVATION --- AFTER EXCAVATION --- AT END OF EXCAVATION ---DEPTH(ft)0.0 2.5 5.0 SAMPLE TYPENUMBERPAGE 1 OF 1 TEST PIT NUMBER TP 6 PROJECT NUMBER 220290 CLIENT DevCo, LLC PROJECT LOCATION Lots 1-2, Westlake 4th Addition PROJECT NAME Geotechnical Investigation GENERAL BH / TP / WELL - GINT STD US.GDT - 6/10/22 10:52 - \\FILES\CORPORATE\OFFICES\BOZEMAN\CANDH\OFFICEDATA\CH\22\220290\GEOTECH\TEST PIT LOGS (220290).GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION OL CL GP 1.5 4.0 7.0 0 TO 1.5 FEET: SILTY CLAY ORGANIC SOIL; (OL); dark brown to black; moist; soft. 1.5 TO 4 FEET: SANDY LEAN CLAY; (CL); brown; moist; medium plasticity; soft to medium stiff; approximately 30 percent fine to coarse grain sand; approximately 70 percent clayeyfines. 4 TO 7 FEET: POORLY GRADED GRAVEL WITH SAND; (GP); brown; moist; medium dense to dense; approximately 60 percent subangular gravels; approximately 30 percentfine to coarse grain sand; approximately 10 percent clayey fines. Bottom of test pit at 7.0 feet. NOTES GROUND ELEVATION LOGGED BY Noah J. Schaible, E.I. EXCAVATION METHOD CAT 305 Mini Tracked Excavator EXCAVATION CONTRACTOR Burke Construction and Excavation GROUND WATER LEVELS: DATE STARTED 4/28/22 COMPLETED 4/28/22 AT TIME OF EXCAVATION --- AFTER EXCAVATION --- AT END OF EXCAVATION ---DEPTH(ft)0.0 2.5 5.0 SAMPLE TYPENUMBERPAGE 1 OF 1 TEST PIT NUMBER TP 7 PROJECT NUMBER 220290 CLIENT DevCo, LLC PROJECT LOCATION Lots 1-2, Westlake 4th Addition PROJECT NAME Geotechnical Investigation GENERAL BH / TP / WELL - GINT STD US.GDT - 6/10/22 10:52 - \\FILES\CORPORATE\OFFICES\BOZEMAN\CANDH\OFFICEDATA\CH\22\220290\GEOTECH\TEST PIT LOGS (220290).GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA Appendix F Report Limitations GEOTECHNICAL INVESTIGATION REPORT #220290 – LOTS 1 & 2, BLOCK 1, WESTLAKES 4TH ADDITION SUBDIVISION, BOZEMAN, MONTANA Report Limitations and Guidelines for Use This appendix has been prepared to help the client understand the risks associated with the use of this report and provide guidelines on the proper use of this report. This report was prepared to be used exclusively by DevCo, LLC for the residential development proposed to be constructed on Lots 1-2 of the Westlakes 4th Addition Subdivision located in the Southeast Quarter of Section 1, Township 2 South, Range 5 East, in Gallatin County, Montana. All of the work was performed in accordance with generally accepted principles and practices used by geotechnical engineers and geologists practicing in this or similar localities. This report should not be used by anyone it was not prepared for, or for uses it was not intended for. Field investigations and preparation of this report was conducted in accordance with a specific set of requirements set out by the client, which may not satisfy the requirements of others. This report should not be used for nearby sites or for structures on the same site that differ from the structures that were proposed at the time this report was prepared. Any changes in the structures (type, orientation, size, elevation, etc.) proposed for this site must be discussed with our company for this report to be valid. Our services consist of professional opinions based on subsurface exploration at specific points, surface observation of the site, and the review of available published data. These data are then extrapolated by geologists and geotechnical engineers to give an opinion of the overall subsurface conditions. Based on the subsurface conditions that are thought to occur at the site, we evaluate how those conditions would respond to the construction that is proposed and give recommendations on foundation design and subgrade improvement. Our subsurface exploration is limited to visual observation of the materials uncovered in an open test pit dug by an excavator. Soil testing was minimal in this investigation so conservative values have been estimated for bearing capacity and potential settlement from visual observation of the soil and reference to the International Building Code. Sampling and testing necessary for a local and global slope stability analysis have also not been completed for this site. Catastrophic events and other structures can contribute to the global stability of a slope and have not been analyzed. If more in depth subsurface investigation is desired, please contact our office to discuss your options. It is important to note that subsurface exploration identifies actual subsurface conditions only at specific points under the conditions present at the time of exploration. Because of this, actual conditions may differ from those inferred to exist. The transitions between materials observed may be much more gradual or abrupt than inferred and subsurface materials may be uncovered during construction that were not thought to occur when the initial subsurface investigation was carried out. Conditions at the site can also change with time due to natural processes and construction practices on the site or on adjacent sites. With these limitations in mind, it is recommended that our services be retained for observation of the materials encountered during construction and that we are informed of any changes that occur on the site and any unexpected conditions that are encountered. This report is only a preliminary recommendation, which may change if unexpected conditions are encountered during construction. We cannot be held responsible for damages due to constructing on a site with conditions that are different from conditions thought to occur from our investigation. The only way to verify if the conditions encountered during construction are the same as expected in our report is to have us inspect the subgrade materials during construction. We cannot be held responsible for constructing on materials that we have not seen in person. The scope of our investigation did not include an environmental assessment for determining the presence or absence of hazardous or toxic materials on the site. If information regarding the potential presence of hazardous materials on the site is desired, please contact us to discuss your options for obtaining this information. This report is valid as a complete document only. No portion of this report should be transmitted to other parties as an incomplete document. Misinterpretation of portions of this report (i.e. test pit logs) is possible when this information is transmitted to others without the supporting information presented in other portions of the report. If any questions arise with regards to any aspects of this report, please contact us at your convenience to avoid misinterpretation. Costly mistakes due to misinterpretation of geotechnical reports can usually be avoided by a quick phone call. North 3rd Apartments Kimley-Horn and Associates, Inc. Bozeman, MT Preliminary Drainage Report November 2022 Page 5 APPENDIX C: RETENTION SYSTEM SIZING CALCULATIONS North 3rd Apartments Bozeman, MT Kimley-Horn and Associates, Inc. Preliminary Drainage Report PROJECT NAME: CLIENT NAME: KH PROJECT Building 0.9 Paving & Sidewalk 0.9 Landscape 0.2 Building (SF) =72,209 Landscaping (SF) =63,836 Sidewalk & Paving (SF) = 166,934 Total (SF) = 302,979 A (ac) = 6.96 I (in/hr)*0.41 Cw 0.75 Qmax (cfs)2.1 Volume = 7200*Q Volume Required (cf)15451 North 3rd Ave Apartments DevCo *Design Storm is 10-yr 2-hr storm per Design Standards Land Use Areas Runoff Coefficients (C) 090071002 Post-Development Flow Calculations Retention Volume Calculation North 3rd Apartments Kimley-Horn and Associates, Inc. Bozeman, MT Preliminary Drainage Report November 2022 Page 6 APPENDIX D: CONVEYANCE CALCULATIONS Scenario: Base Page 1 of 176 Watertown Road, Suite 2D Thomaston, CT 06787 USA +1-203-755-1666 11/18/2022 StormCAD [10.03.04.53] Bentley Systems, Inc. Haestad Methods Solution CenterDevco_Bozeman.stsw FlexTable: Conduit Table Diameter (in) Section TypeLength (User Defined) (ft) Invert (Stop) (ft) Stop NodeInvert (Start) (ft) Start NodeLabelID 18.0Circle16.64,768.59CB-164,768.67CB-17PIPE -114 (oPIPE-STRM)72 18.0Circle29.44,768.44O-14,768.59CB-16PIPE -115 (oPIPE-STRM)74 15.0Circle193.04,768.67CB-174,770.07CB-9PIPE -09 (oPIPE-STRM)70 15.0Circle205.94,770.07CB-94,771.56CB-1PIPE -08 (oPIPE- STRM)66 12.0Circle12.14,769.12CB-144,769.01O-2PIPE -85 (oPIPE- STRM)71 15.0Circle177.04,772.84CB-34,771.56CB-1PIPE -11 (oPIPE- STRM)63 15.0Circle123.94,770.31CB-114,769.12CB-14PIPE -86 (oPIPE- STRM)68 12.0Circle84.14,773.45CB-44,772.84CB-3PIPE -12 (oPIPE-STRM)62 15.0Circle31.34,770.60CB-104,770.31CB-11PIPE -87 (oPIPE- STRM)67 15.0Circle31.64,770.46CB-134,770.31CB-11PIPE -116 (oPIPE-STRM)69 15.0Circle103.04,771.59CB-84,770.60CB-10PIPE -88 (oPIPE- STRM)65 15.0Circle362.04,775.04CB-74,771.59CB-8PIPE -89 (oPIPE- STRM)57 12.0Circle107.44,771.56CB-14,772.44CB-2PIPE -07 (oPIPE-STRM)64 15.0Circle30.84,775.33CB-64,775.04CB-7PIPE -90 (oPIPE- STRM)56 12.0Circle43.04,775.33CB-64,775.74CB-5PIPE -70 (oPIPE- STRM)55 12.0Circle34.24,768.35CB-154,770.00O-3PIPE -72 (oPIPE- STRM)73 Flow / Capacity (Design) (%) Capacity (Full Flow) (cfs) Velocity (ft/s) Flow (cfs) Manning's n Page 1 of 276 Watertown Road, Suite 2D Thomaston, CT 06787 USA +1-203- 755-1666 11/18/2022 StormCAD [10.03.04.53]Bentley Systems, Inc. Haestad Methods Solution CenterDevco_Bozeman.stsw FlexTable: Conduit Table Flow / Capacity (Design) (%) Capacity (Full Flow) (cfs) Velocity (ft/s) Flow (cfs) Manning's n 162.29.668.8615.660.010 162.29.668.8615.660.010 152.77.148.8910.910.010 92.77.145.396.620.010 86.74.526.483.920.010 60.17.143.504.290.010 47.88.206.613.920.010 31.93.941.601.260.010 23.28.205.441.900.010 22.75.943.911.350.010 21.78.205.341.780.010 15.78.204.871.290.010 13.24.190.700.550.010 12.78.204.581.040.010 8.84.523.550.400.010 1.210.180.620.120.010 Page 2 of 276 Watertown Road, Suite 2D Thomaston, CT 06787 USA +1-203- 755-1666 11/18/2022 StormCAD [10.03.04.53]Bentley Systems, Inc. Haestad Methods Solution CenterDevco_Bozeman.stsw