ATTACHMENT G GEOTECHNICAL REPORT Geotechnical Engineering Report Avon Wastewater Treatment Facility Nutrient Upgrades Project Avon, Colorado March 2019 March 27, 2019 File Number: 517050-000 Carollo Engineers, Inc. 390 Interlocken Crescent, Suite 800 Broomfield, CO 80021 Attention: Jeff Berlin, P.E. Subject: Geotechnical Engineering Report Avon Wastewater Treatment Facility Nutrient Upgrades Project Avon, Colorado Mr. Berlin: Submitted herewith is the geotechnical engineering report for the Avon Wastewater Treatment Facility Nutrient Upgrades Project. This study was conducted in accordance with the contract between Brierley Associates and Carollo Engineers, Inc. This report contains the results of our findings, an engineering interpretation with respect to the available project characteristics, and recommendations to aid design and construction of earth-related phases of this project. We appreciate the opportunity to work with you on this project. If we can be of further assistance, or if you have any questions, please contact our office. Sincerely, BRIERLEY ASSOCIATES 3/27/19 Derek Magnuson, PG, CEG Steven Kuehr, PE Project Geologist Principal 990 South Broadway, Suite 222, Denver, CO 80209 | 303-703-1405 | www.BrierleyAssociates.com Geotechnical Engineering Report Avon Wastewater Treatment Facility 3/27/2019 Page i of ii TABLE OF CONTENTS 1 Introduction ....................................................................................................................... 1 2 Site Description ................................................................................................................. 2 3 Project Description ........................................................................................................... 2 4 Field and Laboratory Investigations ................................................................................ 3 Field Investigation ........................................................................................................ 3 Laboratory Investigation ............................................................................................... 4 4.2.1 Geotechnical Testing ............................................................................................ 4 4.2.2 Corrosion Testing ................................................................................................. 4 5 Subsurface Conditions ..................................................................................................... 5 Site Geology ................................................................................................................ 5 Summary of Subsurface Materials ............................................................................... 6 5.2.1 Fill (CL, GC-GM) ................................................................................................... 6 5.2.2 Alluvium (CL-ML, SM, SC-SM, GM, GC-GM, GW, GP-GM) .................................. 6 5.2.3 Residuum ............................................................................................................. 7 5.2.4 Bedrock ................................................................................................................ 7 5.2.5 Groundwater ......................................................................................................... 7 Geologic Hazards ........................................................................................................ 8 6 Design Recommendations ............................................................................................... 9 General ........................................................................................................................ 9 Shallow Foundations .................................................................................................... 9 Deep Foundations.......................................................................................................10 Lateral Earth Pressures ..............................................................................................11 Geotechnical Parameters for Counteracting Buoyancy ...............................................12 Frost Heave ................................................................................................................13 Surface Drainage ........................................................................................................13 Site Piping ..................................................................................................................13 6.8.1 Modulus of Soil Reaction (E’) ...............................................................................14 6.8.2 Thrust Restraint ...................................................................................................14 Seismic Parameters ....................................................................................................14 .........................................................................15 7 Construction Procedures and Recommendations ........................................................15 General .......................................................................................................................15 Excavation Slopes ......................................................................................................16 Geotechnical Engineering Report Avon Wastewater Treatment Facility 3/27/2019 Page ii of ii 7.2.1 Temporary Slopes ...............................................................................................16 7.2.2 Permanent Slopes ...............................................................................................17 Site Grading and Earthwork ........................................................................................17 7.3.1 Site Preparation ...................................................................................................17 7.3.2 Excavations .........................................................................................................17 7.3.3 Engineered Fill Placement and Compaction ........................................................18 7.3.4 Trench Backfill, Placement and Compaction ........................................................19 7.3.5 Recommended Compaction Specifications ..........................................................20 Construction Dewatering .............................................................................................20 Bedrock Excavation ....................................................................................................21 Micropile Construction ................................................................................................21 8 Limitations ........................................................................................................................21 TABLES Table No. Title I Summary of Geotechnical Laboratory Test Results II Summary of Corrosion Test Results FIGURES Figure No. Title 1 Site Vicinity 2 Boring Locations APPENDIX A – Test Boring Key and Test Boring Reports APPENDIX B – Laboratory Testing Results Geotechnical Engineering Report Avon Wastewater Treatment Facility 3/27/2019 Page 1 of 22 1 INTRODUCTION Brierley Associates (Brierley) has been retained by Carollo Engineers, Inc. (Carollo) to conduct a geotechnical engineering investigation for proposed Nutrient Upgrades Project at the Avon Wastewater Treatment Facility (WWTF) located in Avon, Colorado. The purpose of the geotechnical investigation is to provide key subsurface and geotechnical information necessary to complete the foundation design and provide earthwork recommendations for the proposed structures and pavements. In preparing this report, our firm has relied on the following references: • 2015 International Building Code, Section 1613; • American Society of Civil Engineers (ASCE), 2010, Minimum Design Loads for Buildings and Other Structures; • Chen & Associates, 1984, Soil and Foundation Investigation, Proposed Building Addition, Avon Wastewater Treatment Plant, Avon, Colorado, dated June 5; • Colorado Association of Geotechnical Engineers (CAGE), December 1996, Guidelines for Slab Performance Risk Evaluation and Residential Basement Floor System Recommendations’; • Colorado Geological Survey (CGS), 2008, EG-14 Collapsible Soils in Colorado; • Ductile Iron Pipe Research Association (DIPRA), 2017, Corrosion Control Polyethylene Encasement, revised January; • HP Geotech, 2009, Geotechnical Engineering Study, Proposed Heat Recovery System, WWTP to West Benchmark Road, Avon, Colorado, dated September 30; • Kosmatka, S.H., Beatrix Kerkhof, and William C. Panarese, Design and Control of Concrete Mixtures, Portland Cement Association (PCA), 14th Edition, 2002; • Mock, R.G., and Pawlak, S.L., 1983, Alluvial fan hazards at Glenwood Springs; • Mock R.G., 2015, Engineering Geologic Practices on the Western Slope; • Occupational Safety & Health Administration, Standards 29 CFR, 1926 Subpart P App A; • Peak Land Consultants (PLC), 2017, Topographic Map, Tract N and O, Benchmark at Beaver Creek, Town of Avon, Eagle County, Colorado, Sheet 1 of 3, dated February 1; • Tweto, O., Moench, R.H., Reed, J.C., 1978, Geologic Map of the Leadville 1° x 2° Quadrangle, Northwestern Colorado, Scale 1:250,000. Geotechnical Engineering Report Avon Wastewater Treatment Facility 3/27/2019 Page 2 of 22 • United States Geological Survey (USGS), 2018, U.S. Seismic Design Maps Web Application, http://earthquake.usgs.gov/designmaps/us/application.php. • USDOT, FHWA,