Attachment B - Geotechnical Report.pdf

ENGINEERING DESIGN AND OPERATIONS PLAN: NORTH LANDFILL

Larimer County, Colorado

Appendix A

Appendix A.

Geotechnical Engineering Report (Terracon 2020)

REPORT COVER PAGE

Geotechnical Engineering Report

Larimer CO Hydro

Larimer County, Colorado

January 17, 2020

Terracon Project No. 2019P031

Prepared for:

HDR Engineering, Inc.

Denver, Colorado

Prepared by:

Terracon Consultants, Inc.

Fort Collins, Colorado

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REPORT TOPICS

INTRODUCTION

SITE CONDITIONS

PROJECT DESCRIPTION

GEOTECHNICAL CHARACTERIZATION

GEOTECHNICAL OVERVIEW

SEISMIC CONSIDERATIONS

GENERAL COMMENTS

Note: This report was originally delivered in a web-based format. Orange Bold text in the report indicates a referenced section heading. The PDF version also includes hyperlinks which direct the reader to that section and clicking on the

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ATTACHMENTS

EXPLORATION AND TESTING PROCEDURES

PHOTOGRAPHY LOG

SITE LOCATION AND EXPLORATION PLANS

EXPLORATION RESULTS

SUPPORTING INFORMATION

Note: Refer to each individual Attachment for a listing of contents.

http://client.terracon.com/

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INTRODUC TION

Geotechnical Engineering Report

Larimer CO Hydro

County Road 11 and County Road 76

Larimer County, Colorado Terracon Project No. 2019P031

January 17, 2020

INTRODUCTION

Previously, Terracon Consultants, Inc. (Terracon) prepared a Hydrogeologic and Geotechnical

Investigation Workplan (Project No. 3519P031; report dated August 20, 2019) for the project referenced above. We also submitted two DRAFT Geotechnical Data Report (Project No.

2019P031; report dated October 14, 2019 and report dated December 10, 2019) to provide portions of the subsurface information to assist other members of the project team with performing analyses as we continued with our field exploration and prepared our final report. Terracon has substantially completed the subsurface geotechnical investigation for the proposed new municipal solid waste landfill (MSWLF) project. A description of the project, discussion of project background, site geologic setting, description of field activities, geotechnical soil borings, piezometers, and groundwater monitoring wells, and geotechnical discussions and conclusions are presented below.

SITE CONDITIONS

The following description of site conditions is derived from our site visits in association with the field exploration and our review of publicly available geologic and topographic maps.

Item Description

Existing

Improvements

An existing power line spans from the northwest portion of the site to the southeast portion of the site.

Current Ground

Cover

The ground surface is covered with native grasses and weeds with isolated areas of shrubs and some trees.

Existing Topography

The site generally consists of rolling hills with a valley directing drainage through the site from the northwest to the southeast. Topographic mapping indicates relief across the property is about 45 to 50 feet generally sloping towards the valley spanning the middle of the site and down towards the southeast.

Larimer CO Hydro ■ Larimer County, Colorado

January 17, 2020 ■ Terracon Project No. 2019P031

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PROJECT DESCRIPTION

Item Description

Project Description

Larimer County Colorado is proposing to construct a new municipal solid waste landfill northeast of the intersection of County Road (CR) 11 and CR 76 in Larimer County, Colorado. The area designated for landfill development includes approximately 211 acres (Waste Disposal Unit 1) and approximately

104 acres (Waste Disposal Unit 2) of undeveloped land located approximately

5.6 miles north of Wellington, Colorado. The site is located in portions of the

NW ¼, portions of the SW ¼, and portions of the SE ¼ of Section 29, Township 10 N, Range 68 W as shown on the Site Location plan. We understand the proposed MSWLF will be used for disposal of solid waste from household, community, commercial and industrial sources that do not contain hazardous wastes.

Scope of Services and Purpose

The geotechnical engineering services for this project were performed as part of the proposed Larimer County MSWLF permit application associated with development of the landfill and supporting operational features. The purpose of this geotechnical investigation is to thoroughly characterize aspects of the subject property which may directly or indirectly affect the design, construction, operation or monitoring of the proposed landfill facility. We are in the process of completing the hydrogeologic investigation and associated analyses, which will be reported under a separate cover. These studies are intended to meet the requirements of the Colorado Department of Public

Health and Environment (CDPHE) Regulation 6 CCR 1007-2, PART 1, Section 3 – Standards for Solid Waste Disposal Landfill Sites and Facilities.

Project Background

Larimer County intends to permit, design and operate the proposed landfill on an approximately 626-acre tract of land owned by Larimer County, with a smaller portion of two non-contiguous tracts (Unit 1 is approximately 211 acres and Unit 2 is approximately 104 acres) designated as the waste disposal area.

Previously, Terracon has completed two subsurface exploration programs in the general area of the proposed MSWLF. Five geotechnical borings (TW-1 through TW-5) were completed at the site by Terracon in September 2002. In addition, fifteen soil borings (T-1 through T-15) were drilled at the site by

Terracon in January 2017. The previous studies were completed to evaluate the suitability of the site as a potential future landfill, and to evaluate soil properties and estimate overburden thickness for potential aggregate use.

We have included the boring logs from these previous studies in this report to assist with the current analyses and design.

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GEOTECHNICAL CHARACTERIZATION

Geology

The project area is located within the Colorado Piedmont section of the Great Plains physiographic province. The Colorado Piedmont, formed during Late Tertiary and Early

Quaternary time (approximately 2,000,000 years ago), is a broad, erosional trench which separates the Southern Rocky Mountains from the High Plains. Structurally, the site lies along the western flank of the Denver Basin. During the Late Mesozoic and Early Cenozoic Periods

(approximately 70,000,000 years ago), intense tectonic activity occurred, causing the uplifting of the Front Range and associated down-warping of the Denver Basin to the east. Relatively flat uplands and broad valleys characterize the present-day topography of the Colorado Piedmont in this region.

Surficial geologic conditions mapped in the vicinity of the site (1Workman, et al, 2018), (2Tweto, 1979), (3Hershey and Schneider, 1972) generally consist of alluvial deposits. Researched publications describe the project area as either older gravel and alluvium associated with the

Slocum Alluvium (Workman, Tweto), or pediment deposits consisting of arkosic sand with minor amounts of red clay (Hershey and Schneider).

Bedrock units mapped in the vicinity of the site include the upper member of Pierre Shale (Tweeto) and Colton4, Hills Sandstone (Klf). Bedrock was encountered in our borings at depths ranging from about 1 to 49 feet below existing ground surface. The bedrock formations in the area have been reported to include mostly gray concretionary shale. Our subsurface exploration generally confirmed the conditions anticipated from the geologic maps.

The geologic conditions presented in this section were obtained by locating the subject site on available large-scale geologic maps. Because of the scales involved, precise location of the site can be difficult to determine. In addition, the large-scale geologic maps describe only general trends. Local variations are possible and site specific geology may differ from those described above.

1Workman, J.B., Geologic Map of the Fort Collins 30’x60’ Quadrangle, Larimer and Jackson Counties Colorado, and Albany and Laramie Counties, Wyoming United States Geological Survey, Map SIM-3399.

2 Tweto, Ogden, 1979 Geologic Map of Colorado, United States Geological Survey.

3 Hershey, L.A. and Schneider, P.A., 1972 Geologic Map of the Lower Cache La Poudre River Basin, United States Geologic Survey, Map I-68.

4Colton, Roger B., 1978 Geologic Map of the Boulder-Fort Collins-Greeley Area, Colorado, United States Geological Survey, Map I-855-G

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Subsurface Profile

Our geotechnical subsurface exploration program consisted of the completion of geotechnical exploratory soil borings, installation of groundwater piezometers, and installation of groundwater monitoring wells. As previously stated, twenty borings (T-1 through T-5 and TW-1 through TW-

15) were previously completed at this site and are attached to this report. For the current geotechnical study, we completed the following to supplement the subsurface information previously obtained:

◼ Thirty-six (36) geotechnical soil borings completed to depths of approximately 19½ to 59½ feet below existing site grades.

◼ Five (5) groundwater piezometers completed to depths of approximately 73 to 120 feet below existing site grades.

◼ Ten (10) groundwater monitoring wells finished to depths of approximately 33 to 83 feet below existing site grades.

Vegetative Layer: Approximately 6 to 8 inches of a vegetative layer or topsoil was encountered in each of the borings, groundwater monitoring well boreholes and piezometer boreholes completed at this site.

Overburden Soils: The overburden soils encountered in our exploratory borings varied across the site and consisted of interlayered clay, silt and sand with varying amounts of gravel. Clay soils were lean with liquid limits generally ranging from about 24 to 48 and plasticity indices ranging from about 9 to 34. Clay soils contained between 50 and 96 percent fines (passing the

No. 200 sieve). In general, clay soils were stiff to very stiff. Clayey to silty sands with varying amounts of gravel were encountered in many of the borings with liquid limits generally ranging from non-plastic to 28 and plasticity indices ranging rom non-plastic to 14. Clayey silty sands contained between 12 and 44 percent fines (passing the No. 200 sieve). Poorly-graded sand with varying amounts at gravel was also found in many of the borings at varying depths and contained between about 5.4 and 11.7 percent fines. Silts with varying amounts of sand and/or gravel was encountered in several of our borings and contained between about 50 to 75 percent fines.

Bedrock: Bedrock was encountered below the overburden soils and generally consisted of interbedded clay/siltstone, interbedded clay/sandstone and shale. Typically, interbeds were shallow with varying thicknesses as shown in the photographs of core samples obtained during the field exploration and presented in the Photography Log section of this report. The depth to bedrock varied significantly across the site, varying from about 1 to 49 feet below existing site grades. The upper 2 to 5 feet of bedrock in several of the borings was highly weathered. In general, the shale was the lower bedrock unit. Samples of bedrock selected for laboratory testing exhibited liquid limits ranging from about 39 to 48 and plasticity indices ranging from about 23 to

30. Bedrock samples contained between about 74 to 89 percent fines (passing the No. 200 sieve).

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Specific conditions encountered at each exploration point are indicated on the individual boring, monitoring well, and piezometer logs. Stratification boundaries on the logs represent the approximate location of changes in soil types; in situ, the transition between materials may be gradual. Details for each of the borings can be found in Exploration Results. A discussion of field sampling and laboratory testing procedures and test results are presented in Exploration and

Testing Procedures.

We are currently in the process of completing two additional piezometers (PZ-6 and PZ-7) to provide additional groundwater data within Unit 1 as well as an additional groundwater monitoring well (MW-11) located southwest of Unit 1. Maps showing the site, boring, monitoring well and piezometer locations are shown in the Site Location and Exploration Plan sections, respectively.

In order to provide a visual representation of subsurface conditions encountered during our field exploration, we prepared diagrams showing various cross-sections throughout the site. We have attached an Exploration Plan with Various Cross-Sections showing a plan view of where these various cross-sections were selected. We have also attached fourteen Subsurface Profiles for

Unit 1 and another three Subsurface Profiles for Unit 2.

As noted in General Comments, this characterization is based upon widely spaced exploration points across the site and variations are likely.

Groundwater Monitoring Wells and Piezometers

Our geotechnical engineering services included installation of ten groundwater monitoring wells at selected locations around the perimeter of the disposal areas (Unit 1 and Unit 2) as well as five piezometers at selected locations within the disposal areas. While drilling the boreholes to be completed as groundwater monitoring wells and piezometers, it was very difficult to accurately determine where groundwater was present within the various strata underlying the site.

Boreholes were effectively dry with no significant evidence of groundwater at depth; however, groundwater would slowly accumulate in the boreholes within several days after completion.

Initial efforts included drilling boreholes to selected depths and waiting several days for groundwater to accumulate within the borehole. This process was determined to be ineffective and would have taken too much time.

The project design team elected to drill a group of comparatively closely-spaced “nested” boreholes (within about 10 feet of each other) at many of the groundwater monitoring well and piezometer locations. The “nested” boreholes were completed to varying depths and temporary piezometers were inserted into each of the boreholes to allow time for groundwater to stabilize.

Temporary piezometers consisted of 1-inch diameter, 0.010-inch machine slotted PVC well screen and 1-inch diameter PVC riser to facilitate delayed groundwater measurements. We periodically measured groundwater levels as groundwater slowly accumulated in some of the

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“nested” temporary piezometers to assist with determining the appropriate screening interval for the permanent groundwater monitoring wells and piezometers.

Once the screening interval was determined at each location, we either drilled a new borehole for the permanent groundwater monitoring well or piezometer or reamed out one of the “nested” boreholes to the desired depth for completion. The remaining “nested” borehole locations for temporary piezometers were abandoned by removing the PVC pipe and backfilling with bentonite or a mixture of auger cuttings and bentonite.

We have attached a Summary of Groundwater Level Measurements presenting the periodic groundwater levels measured in the “nested” temporary piezometer locations. We have labelled which of the “nested” temporary piezometer locations were abandoned after screening intervals for each location were determined, as well as subsequent groundwater level readings after a permanent groundwater monitoring well or piezometer was installed.

The water levels observed in groundwater monitoring wells and piezometers are provided on the groundwater measurements table included in the Exploration Results section of this report and are noted on the attached boring-well-piezometer logs.

Groundwater level fluctuations occur due to seasonal variations in the water levels present in nearby water features, amount of rainfall, runoff and other factors not evident at the time the field subsurface exploration was performed. Subsequent hydrogeologic studies will also address likely impacts due to construction of the MSWLF. Therefore, groundwater levels during construction or at other times in the life of the landfill may be higher or lower than the levels indicated on the boring-well-piezometer logs. Our scope of services also includes monthly groundwater monitoring at the site to provide information regarding likely groundwater level fluctuations over a one-year period.

Laboratory Testing

A laboratory testing program was formulated and completed to measure applicable properties of the subsurface materials encountered in our geotechnical exploratory borings completed at this site. Laboratory testing included the following:

◼ Atterberg limits (ASTM D4318)

◼ Particle-size analysis (ASTM D422 and D7928)

◼ USCS Soil Classification (ASTM D2216)

◼ Specific gravity (ASTM D854)

◼ One-dimensional swell-consolidation (ASTM D4546)

◼ Laboratory compaction characteristics (ASTM D698 and D1557)

◼ Remolded hydraulic conductivity (ASTM D5084)

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Several bulk samples of various soils and/or bedrock were obtained. Bulk samples No. 1, 2, 3 and 4 were obtained from specific borings at respective depths. Bulk samples Nos. 5, 6, and 7 were prepared by combining similar materials from multiple borings at various depths that exhibited similar soil properties.

The results of the laboratory testing performed on soil and bedrock samples obtained from the site during the field exploration are included on the boring logs and as separate graphs in the

Exploration Results section of this report. We have also compiled all the laboratory test results completed to date in a Summary of Laboratory Test Results provided in the Exploration Results section of this report.

As described in the Exploration and Testing Procedures section of this report, samples of the soils and bedrock obtained from our borings completed at this site were generally obtained using a modified California barrel and/or standard split-barrel sampling procedures. It is typically preferred to utilize thin-walled tube samples pushed hydraulically into the ground to obtain relatively undisturbed samples of cohesive soils. However, the comparatively hard and dry subsurface conditions caused crimping of the tubes and poor sampling was experienced. We elected to utilize a modified California sampler lined with rings to obtain samples of the soils and bedrock at selected depths within the borings for various laboratory testing. We understand there was concern by other members of the project team regarding the disturbance of samples obtained using the modified California sampler. Our experience suggests this type of sampler is very common along the Front Range of Colorado. We have performed multiple subsurface investigations in these types of soils and bedrock underlying this site. Based on our experience, we believe the unit weights and other soil and bedrock properties measured using these types of samplers are valid with minor amounts of sample disturbance. If comparatively softer or higher moisture content soils were encountered, we would have utilized thin walled tubes to obtain samples of cohesive soils for testing.

GEOTECHNICAL OVERVIEW

Based on subsurface conditions encountered in the borings, groundwater monitoring wells, and piezometers, the site appears suitable for the proposed construction from a geotechnical point of view. We have identified several geotechnical conditions that could impact design, construction and performance of the proposed MSWLF facility. These included shallow groundwater, expansive soils and bedrock, potentially soft/loose, low strength soils, and excavatability of the bedrock and shale units present below the site. These conditions will require particular attention in project planning, design and during construction and are discussed in greater detail in the following sections. Once the design of the facility has progressed and site grading, slope configuration, structure locations, etc. are determined, site-specific, design-level geotechnical studies should be performed for each of these elements.

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Mine Subsidence Potential

Review of coal mine subsidence maps completed by the Colorado Geological Survey (1Amuedo and ivy, 1975), indicates the subject property is not located within the boundaries of a coal subsidence hazard as defined by this study.

Shallow Groundwater

As previously stated, groundwater was measured at depths ranging from about 21.2 to 71.3 feet below existing site grades. Shallower groundwater areas may be present in other areas of the site, particularly where the topography of the site is lower in elevation. Final site grading should be planned and designed to avoid cuts where shallow groundwater is known to exist, and also in areas where such grading would create shallow groundwater conditions. If deeper cuts are unavoidable, installation of a subsurface drainage system may be needed.

Expansive Soils and Bedrock

Expansive soils and bedrock are present on this site and these conditions constitute a geologic hazard. This report provides recommendations to help mitigate the effects of soil shrinkage and expansion. However, even if these procedures are followed, some movement and cracking in the structures, pavements, and flatwork is possible. The severity of cracking and other damage such as uneven floor slabs and flat work will probably increase if modification of the site results in excessive wetting or drying of the expansive clays and/or claystone bedrock. Eliminating the risk of movement and cosmetic distress is generally not feasible, but it may be possible to further reduce the risk of movement if significantly more expensive measures are used during construction.

Low Strength Soils

Comparatively soft clay and/or loose sand soils were encountered within the upper approximately

10 feet of some of the borings completed at this site. These materials can be susceptible to disturbance and loss of strength under repeated construction traffic loads and unstable conditions could develop. Stabilization of soft soils may be required at some locations to provide adequate support for construction equipment and proposed structures. Terracon should be contacted if these conditions are encountered to observe the conditions exposed and to provide guidance regarding stabilization on a case-by-case basis (if needed).

1Amuedo & Ivey, 1975, Ground Subsidence and Land-Use Considerations Over Coal Mines in the Boulder-Weld Coal Field, Colorado, Colorado Geological Survey, Environmental Geology No. 9.

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Excavatability

It is anticipated that the vast majority of the site excavation for the anticipated construction can be accomplished with conventional earthmoving equipment. The overburden soils consist of varying layers of clay, silt, sand and gravel. Where granular soils, such as sand and gravel, comprise the subsurface conditions, the contractor should expect areas of weak and likely caving conditions.

We believe assessing ripper performance for medium hard to very hard bedrock is best analyzed using shear wave velocities from field testing. Our scope of services did not include obtaining shear wave velocities from this site. However, we have utilized the results of our field exploration to provide some general discussion about rippability of the bedrock underlying the overburden soils at this site.

Excavatability depends on the methods used for excavation and the material properties. Factors contributing to how easily a material can be excavated depend on many factors including degree of weathering, material strength bedding dip and spacing, type of excavation, and weather conditions. Our field exploration suggests areas of the upper portions of the interbedded claystone/sandstone/siltstone bedrock can be excavated with low to moderate difficulty. Greater difficulty for ripping will likely be encountered with depth. We believe the bedrock underlying the site will experience difficult to very difficult rippability where field penetration resistance (blow counts) values exceed about 50 blows for 4 inches of penetration. Terracon is also available to provide surface shear wave velocity testing to obtain more data to supplement our cursory recommendations for rippability.

HDR has required we elaborate on excavatability to assist them with defining a baseline for difficult rock excavation for the earthwork contractor. We believe blasting will very likely not be needed to excavate bedrock underlying this site. our experience indicates practical auger refusal encountered during drilling of borings is a fairly reliable indicator at very hard bedrock conditions that would suggest blasting may be needed. We did not encounter practical auger refusal during completion of borings at this site.

We understand Larimer County mobilized to the site to complete exploratory test pits where shallow bedrock was present to provide a cursory evaluation of excavatability. We understand

Larimer County was able to excavate bedrock with blow counts as high as 50 blows for 4 inches of penetration with an excavator with low to moderate resistance.

Our observations of core samples obtained from our borings and observation of exploratory test pit excavations completed during previous studies completed at this site indicate the bedrock is highly fractured with nearly horizontal bedding planes. Bedrock excavations were completed at this site with low to moderate resistance as fractured pieces of bedrock were removed. We believe the vast majority of bedrock below the site (shale and interbedded claystone/siltstone) will

Responsive ■ Resourceful ■ Reliable 10 be rippable with a D8 dozer and single tooth where blow counts core less than 50 blows for 4 inches of penetration. However, our borings and previously completed exploratory test pits were widely spaced and there may be isolated areas of well-cemented bedrock layers that may require more aggressive excavation techniques such as jack-hammering.

SEISMIC CONSIDERATIONS

Our scope of services included determining if the proposed MSWLF is planned in a seismic impact zone which is defined by CDPHE as an area with a ten percent or greater probability that the maximum horizontal acceleration in lithified earth material, expressed as a percentage of the earth’s gravitational pull will exceed 0.10g in 250 years. We used the (United States Geological

Survey (USGS) National Seismic Hazard Mapping Program (NSHMP) Interactive Deaggregation website to obtain this information. For a 2373-year return period (10% exceedance probability in

250 years), the website output indicates a PGA of 0.0975g for the site. The output indicates the

MSWLF site does not fall within a seismic impact zone.

If more extensive evaluation of the site is needed to confirm the landfill is not planned within a seismic impact zone, more detailed analysis will be required. Based on published data, no active faults are known to transverse the site and no evidence of faulting was observed during various field exploration activities conducted at this site. We also believe risk for potential liquefaction is very low for this site. Once the design of slopes associated with the MSWLF facility have been finalized, Terracon can assist the design team with seismic slope stability analyses.

GENERAL COMMENTS

Our analysis and opinions are based upon our understanding of the project, the geotechnical conditions in the area, and the data obtained from our site exploration. Natural variations will occur between exploration point locations or due to the modifying effects of construction or weather.

The nature and extent of such variations may not become evident until during or after construction.

Terracon should be retained as the Geotechnical Engineer, where noted in this report, to provide observation and testing services during pertinent construction phases. If variations appear, we can provide further evaluation and supplemental recommendations. If variations are noted in the absence of our observation and testing services on-site, we should be immediately notified so that we can provide evaluation and supplemental recommendations.

Our Scope of Services does not include either specifically or by implication any environmental or biological (e.g., mold, fungi, bacteria) assessment of the site or identification or prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the potential for such contamination or pollution, other studies should be undertaken.

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Our services and any correspondence or collaboration through this system are intended for the sole benefit and exclusive use of our client for specific application to the project discussed and are accomplished in accordance with generally accepted geotechnical engineering practices with no third-party beneficiaries intended. Any third-party access to services or correspondence is solely for information purposes to support the services provided by Terracon to our client.

Reliance upon the services and any work product is limited to our client, and is not intended for third parties. Any use or reliance of the provided information by third parties is done solely at their own risk. No warranties, either express or implied, are intended or made.

Site characteristics as provided are for design purposes and not to estimate excavation cost. Any use of our report in that regard is done at the sole risk of the excavating cost estimator as there may be variations on the site that are not apparent in the data that could significantly impact excavation cost. Any parties charged with estimating excavation costs should seek their own site characterization for specific purposes to obtain the specific level of detail necessary for costing.

Site safety, and cost estimating including, excavation support, and dewatering requirements/design are the responsibility of others. If changes in the nature, design, or location of the project are planned, our conclusions and recommendations shall not be considered valid unless we review the changes and either verify or modify our conclusions in writing.

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ATTACHMENTS

Contents:

EXPLORATION AND TESTING PROCEDURES

PHOTOGRAPHY LOG

SITE LOCATION AND EXPLORATION PLANS

EXPLORATION RESULTS

SUPPORTING INFORMATION

Note: Refer to each individual Attachment for a listing of contents.

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EXPLORATION AND TESTING PROCEDURES

Field Exploration

The field exploration program consisted of the following:

Number of Exploration Points

Depth (feet) Location

36 borings About 19½ to 59½ Within planned waste disposal areas

(Units 1 and 2)

5 piezometers About 73 to 120 Within planned waste disposal areas

(Units 1 and 2)

10 groundwater monitoring wells About 33 to 83

Around perimeter of planned waste disposal areas (Units 1 and 2)

Exploration Point Layout and Elevations: Initially, we used handheld GPS equipment to locate geotechnical borings, groundwater monitoring wells and piezometers with an estimated horizontal accuracy of +/-20 feet. Field measurements from existing site features were also utilized. After the borings, wells and piezometers were completed, we retained the services of Northern

Engineering to survey the actual test locations. Northern Engineering provided the latitude, longitude and ground surface elevations at each of the exploration points which are shown on the logs.

Subsurface Exploration Procedures: We advanced geotechnical borings, groundwater monitoring wells, and piezometers with several different truck-mounted and all-terrain vehicle drill rigs using continuous-flight solid-stem and/or hollow-stem augers. Samples were obtained at selected intervals of each geotechnical boring, generally at intervals of 5 feet. Soil sampling was performed using thin-wall tube, modified California barrel, and/or standard split-barrel sampling procedures. For the thin-walled tube sampling procedure, a thin-walled, seamless steel tube with a sharp cutting edge was pushed hydraulically into the soil to obtain a relatively undisturbed sample; however, the comparatively hard and dry subsurface conditions caused crimping of the tubes and poor sampling was experienced. For the standard split-barrel sampling procedure, a standard 2-inch outer diameter split-barrel sampling spoon is driven into the ground by a 140-pound automatic hammer falling a distance of 30 inches. The number of blows required to advance the sampling spoon the last 12 inches of a normal 18-inch penetration is recorded as the Standard Penetration Test (SPT) resistance value. The SPT resistance values, also referred to as N-values, are indicated on the boring logs at the test depths. For the modified California barrel sampling procedure, a 2½-inch outer diameter split-barrel sampling spoon is used for sampling. Modified California barrel sampling procedures are similar to standard split-barrel sampling procedures; however, blow counts are typically recorded for 6-inch intervals for a total of 12 inches of penetration. The samples were placed in appropriate containers, taken to our soil laboratory for testing, and classified by a geotechnical engineer.

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We understand there was concern by other members of the project team regarding the disturbance of samples obtained using the modified California sampler. Our experience suggests this type of sampler is very common along the Front Range of Colorado. We have performed multiple subsurface investigations in these types of soils and bedrock underlying this site. Based on our experience, we believe the unit weights and other soil and bedrock properties measured using these types of samplers are valid with minor amounts of sample disturbance. If comparatively softer or higher moisture content soils were encountered, we would have utilized thin walled tubes to obtain samples of cohesive soils for testing.

In addition, we observed and recorded groundwater levels during drilling observations.

Rock coring (using HQ rock core barrel) was performed at several of the exploration points. The cores obtained were placed in a core box, sealed and returned to our laboratory for observation and classification. Air and/or water was used as a drilling fluid for rock coring and the spent water was discharged on site.

Our exploration team prepared field boring logs as part of standard drilling operations including sampling depths, penetration distances, and other relevant sampling information. Field logs included visual classifications of materials encountered during drilling, and our interpretation of subsurface conditions between samples. Final boring logs, prepared from field logs, represent the geotechnical engineer's interpretation, and include modifications based on observations and laboratory test results.

Groundwater Monitoring Wells and Piezometers: Several of the boreholes advanced on the site were completed as either groundwater monitoring wells or piezometers. Groundwater monitoring wells and piezometers were installed in general accordance with ASTM D 5092. The wells and piezometers were registered with the Colorado Department of Natural Resource

Division. The wells and piezometers were constructed using the following methodology:

◼ Installation of 10 feet of 2-inch diameter, 0.010-inch machine slotted PVC well screen with a threaded bottom cap;

◼ Installation of 2-inch diameter, threaded, flush joint PVC riser pipe to approximately 3 feet above the existing ground surface;

◼ Addition of pre-sieved 10/20 grade (or similar) annular silica sand pack from the bottom of the borehole to approximately 2 to 5 feet above the top of the well screen;

◼ Addition of bentonite pellet seal (partially hydrated) to a depth of about 2 feet above the top of the sand pack filter zone;

◼ Addition of bentonite chips or a mixture of bentonite and auger cuttings to a depth of about

2 feet below existing site grades;

◼ Addition of partially hydrated bentonite chips for the upper 2 feet of backfill around riser to the ground surface;

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◼ Installation of a steel protective collar with a hinged surface mount with lockable cover.

The protective casing extended about 3 feet above the ground surface. An approximately

3-foot by 3-foot concrete pad was constructed around each of the monitoring wells and piezometers; and

◼ We are in the process of ordering and installing protective bollards at the surface of each monitoring well location. We will install three bollards at each well location, paint them safety yellow, and fill with concrete. These services will be retained from a professional fencing contractor.

◼ Where groundwater monitoring wells or piezometers were completed within one of the

“nested” boreholes at shallower depths than the total depth drilled, the bottom of the borehole below the well/piezometer was filled with bentonite.

We have partially completed development of the monitoring wells at the site. Well development is consisting of bailing out the water within the well, measuring periodic turbidity and volume extracted during well development. We are working with HDR to determine when the wells have been fully developed based upon measured turbidity values. Development water is being discharged to the ground surface near each well location.

Property Disturbance: We backfilled the geotechnical borings with auger cuttings after completion. Where “nested” boreholes were used to install temporary piezometers, we backfilled these boreholes with bentonite. Our services did not include repair of the site beyond backfilling our boreholes. Excess auger cuttings were dispersed in the general vicinity of the boreholes.

Because backfill material often settles below the surface after a period, we recommend checking boreholes periodically and backfilling, if necessary. We can provide this service for additional fees, at your request.

Laboratory Testing

The project engineer reviewed field data and assigned various laboratory tests to better understand the engineering properties of various soil and bedrock strata. Laboratory testing was conducted in general accordance with applicable or other locally recognized standards.

Procedural standards noted in this report are for reference to methodology in general. In some

Our laboratory testing program includes examination of soil samples by an engineer. Based on the material’s texture and plasticity, we described and classified soil samples in accordance with the Unified Soil Classification System (USCS). Soil and bedrock samples obtained during our field work will be disposed of after laboratory testing is complete unless a specific request is made to temporarily store the samples for a longer period of time.

Bedrock samples obtained had rock classification conducted using locally accepted practices for engineering purposes. Boring log rock classification is determined using the Description of Rock

Properties.

Responsive ■ Resourceful ■ Reliable PHOTOGRAPHY LOG 1 of 2

PHOTOGRAPHY LOG

Interlayered sandstone and siltstone

Interlayered claystone and silstone

Responsive ■ Resourceful ■ Reliable PHOTOGRAPHY LOG 2 of 2

Shale Bedrock

Horizontal bedding planes in sandstone/siltstone

Horizontal bedding planes in shale

Responsive ■ Resourceful ■ Reliable

SITE LOCATION AND EXPLORATION PLANS

Contents:

Site Location

Exploration Plans (3 pages)

Note: All attachments are one page unless noted above.

SITE LOCATION

SITE LOCA TION

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES MAP PROVIDED BY MICROSOFT BING MAPS

EXPLORATION PLAN

Note to Preparer: This is a large table with outside borders. Just click inside the table above this text box, then paste your GIS Toolbox image.

When paragraph markers are turned on you may notice a line of hidden text above and outside the table – please leave that alone. Limit editing to inside the table.

The line at the bottom about the general location is a separate table line. You can edit it as desired, but try to keep to a single line of text to avoid reformatting the page.

EXHIBIT E 11X1 7 LANDSCAPE

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES MAP PROVIDED BY MICROSOFT BING MAPS

Note: At the time of this report, PZ-6 and PZ-7 had not been completed. We will revise this report once these piezometer have been completed.

EXPLORATION PLAN (UNIT 1)

EXPLORATION P LAN

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES MAP PROVIDED BY MICROSOFT BING MAPS

EXPLORATION PLAN (UNIT 2)

EXPLORATION P LAN

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES MAP PROVIDED BY MICROSOFT BING MAPS

EXPLORATION RESULTS

EXPLORATION PLAN WITH VARIOUS CROSS-SECTIONS

Note to Preparer: This is a large table with outside borders. Just click inside the table above this text box, then paste your GIS Toolbox image.

When paragraph markers are turned on you may notice a line of hidden text above and outside the table – please leave that alone. Limit editing to inside the table.

The line at the bottom about the general location is a separate table line. You can edit it as desired, but try to keep to a single line of text to avoid reformatting the page.

EXHIBIT D 11X1 7 LANDSCAPE

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES MAP PROVIDED BY MICROSOFT BING MAPS

5,420

5,430

5,440

5,450

5,460

5,470

5,480

5,490

5,500

5,510

5,520

0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000 2,200 2,400 2,600 5,420

5,430

5,440

5,450

5,460

5,470

5,480

5,490

5,500

5,510

5,520 0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000 2,200 2,400 2,600

BT-39.3 Ft.

B-34

BT-29.4 Ft.

B-35

BT-39.8 Ft.

B-36

BT-39.9 Ft.

B-37

BT-25.4 Ft.

B-38

BT-83.0 Ft.

B-39/MW-4

BT-80.0 Ft.

B-40/MW-5

NOTES:

Borehole Number

Liquid and Plastic Limits

AR

BT

LL PLMoisture Content %w

B-34

Water Level Reading at time of drilling.

Water Level Reading after drilling.

X X

Sampling (See General Notes)

El ev at io n -F ee t

Explanation

Borehole Lithology

Borehole Termination Type

Distance Along Baseline - Feet

Topsoil Poorly-graded Sand with Silt Silty Clay Colorado -

Claystone/Siltstone Silty Sand

Well-graded Sand

Lean Clay with Sand

Poorly-graded Sand with Silt and Gravel

Sands; clean sand to silty sand

Shale

See Exploration Plan for orientation of soil profile.

See General Notes in Supporting Information for symbols and soil classifications.

Soils profile provided for illustration purposes only.

Soils between borings may differ AR - Auger Refusal BT - Boring Termination

SUBSURFACE PROFILE

Unit 1 W-E, Section A-A'

LARIMER CO HYDRO

NORTHEAST OF CR 11 AND CR 76

LARIMER COUNTY, CO

Project No.: 2019P031

Date: 1/17/2020

Scale: 1"=500' 1901 Sharp Point Dr, Ste C Fort Collins, COTH

IS

BO

R

IN

G

LO

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N O

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(F

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/9 /1

Vegetative Layer

B-39/MW-4 is offset about 360 feet south of cross-section line

B-40/MW-5 is offset about 360 feet south of cross-section line

5,440

5,450

5,460

5,470

5,480

5,490

5,500

5,510

5,520

0 500 1,000 1,500 2,000 2,500 3,000 3,500 5,420

5,430

5,440

5,450

5,460

5,470

5,480

5,490

5,500

5,510

5,520 0 500 1,000 1,500 2,000 2,500 3,000 3,500

BT-20.5 Ft.

B-28

BT-75.0 Ft.

B-29/PZ-3

BT-34.9 Ft.

B-30

BT-34.4 Ft.

B-31

BT-80.0 Ft.

B-32/PZ-4

BT-25.5 Ft.

B-33

BT-25.5 Ft.

B-41

NOTES:

Borehole Number

Liquid and Plastic Limits

AR

BT

LL PLMoisture Content %w

B-28

Water Level Reading at time of drilling.

Water Level Reading after drilling.

X X

Sampling (See General Notes)

El ev at io n -F ee t

Explanation

Borehole Lithology

Borehole Termination Type

Distance Along Baseline - Feet

Topsoil Poorly-graded Sand with Silt Silty Clay Siltstone Colorado -

Claystone/Siltstone

Sands; clean sand to silty sand

Bedrock Sandy Lean Clay

Poorly-graded Sand with Silt and Gravel

Silt with Sand

See Exploration Plan for orientation of soil profile.

See General Notes in Supporting Information for symbols and soil classifications.

Soils profile provided for illustration purposes only.

Soils between borings may differ AR - Auger Refusal BT - Boring Termination

SUBSURFACE PROFILE

Unit 1 W-E, Section B-B'

LARIMER CO HYDRO

NORTHEAST OF CR 11 AND CR 76

LARIMER COUNTY, CO

Project No.: 2019P031

Date: 1/17/2020

Scale: 1"=500' 1901 Sharp Point Dr, Ste C Fort Collins, COTH

IS

BO

R

IN

G

LO

G

IS

N O

T

VA

LI

D

IF

SE

PA

R

AT

ED

FR

O

M O

R

IG

IN

AL

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EP

O R

T.

SM

AR

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FE

N

C E

P0

LA

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IM

ER

C O

H

YD

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(F

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-1 3-

).G

PJ

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AT

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G D

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/9 /1

Vegetative Layer

B-41 is offset about 230 feet north of cross-section line

5,475

5,480

5,485

5,490

5,495

5,500

5,505

5,510

5,515

5,520

5,525

5,530

5,535

5,540

0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000 2,200 2,400 2,600 5,475

5,480

5,485

5,490

5,495

5,500

5,505

5,510

5,515

5,520

5,525

5,530

5,535

5,540 0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000 2,200 2,400 2,600

BT-20.3 Ft.

B-22

BT-59.4 Ft.

B-23

BT-30.4 Ft.

B-24

BT-19.9 Ft.

B-25

BT-19.8 Ft.

B-26

BT-34.9 Ft.

B-27

NOTES:

Borehole Number

Liquid and Plastic Limits

AR

BT

LL PLMoisture Content %w

B-22

Water Level Reading at time of drilling.

Water Level Reading after drilling.

X X

Sampling (See General Notes)

El ev at io n -F ee t

Explanation

Borehole Lithology

Borehole Termination Type

Distance Along Baseline - Feet

Topsoil Lean Clay with Sand

Silty Sand with Gravel Clayey Sand

Poorly-graded Sand with Clay and Gravel

Colorado - Claystone/Siltstone

Well-graded Sand with Silt and Gravel

Lean Clay Silty Sand Sandy Lean Clay

See Exploration Plan for orientation of soil profile.

See General Notes in Supporting Information for symbols and soil classifications.

Soils profile provided for illustration purposes only.

Soils between borings may differ AR - Auger Refusal BT - Boring Termination

SUBSURFACE PROFILE

Unit 1 W-E, Section C-C'

LARIMER CO HYDRO

NORTHEAST OF CR 11 AND CR 76

LARIMER COUNTY, CO

Project No.: 2019P031

Date: 1/17/2020

Scale: 1"=500' 1901 Sharp Point Dr, Ste C Fort Collins, COTH

IS

BO

R

IN

G

LO

G

IS

N O

T

VA

LI

D

IF

SE

PA

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AT

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FR

O

M O

R

IG

IN

AL

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EP

O R

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SM

AR

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FE

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P0

LA

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ER

C O

H

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(F

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-1 3-

).G

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AT

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/9 /1

Vegetative Layer

5,440

5,450

5,460

5,470

5,480

5,490

5,500

5,510

5,520

5,530

5,540

0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000 2,200 2,400 2,600 2,800 3,000 5,430

5,440

5,450

5,460

5,470

5,480

5,490

5,500

5,510

5,520

5,530

5,540 0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000 2,200 2,400 2,600 2,800 3,000

BT-60.0 Ft.

B-16/MW-3

BT-29.8 Ft.

B-17

BT-30.0 Ft.

B-18

BT-73.0 Ft.

B-19/PZ-2

BT-20.4 Ft.

B-20 BT-24.5 Ft.

B-21

NOTES:

Borehole Number

Liquid and Plastic Limits

AR

BT

LL PLMoisture Content %w

B-16/MW-3

Water Level Reading at time of drilling.

Water Level Reading after drilling.

X X

Sampling (See General Notes)

El ev at io n -F ee t

Explanation

Borehole Lithology

Borehole Termination Type

Distance Along Baseline - Feet

Topsoil Sands; clean sand to silty sand

Colorado - Claystone/Siltstone Bedrock Sandy Silty

Clay

Silty Sand Silty Sand with Gravel

Poorly-graded Sand with Silt Sandy Silt Sandy Lean

Clay

See Exploration Plan for orientation of soil profile.

See General Notes in Supporting Information for symbols and soil classifications.

Soils profile provided for illustration purposes only.

Soils between borings may differ AR - Auger Refusal BT - Boring Termination

SUBSURFACE PROFILE

Unit 1 W-E, Section D-D'

LARIMER CO HYDRO

NORTHEAST OF CR 11 AND CR 76

LARIMER COUNTY, CO

Project No.: 2019P031

Date: 1/17/2020

Scale: 1"=500' 1901 Sharp Point Dr, Ste C Fort Collins, COTH

IS

BO

R

IN

G

LO

G

IS

N O

T

VA

LI

D

IF

SE

PA

R

AT

ED

FR

O

M O

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IG

IN

AL

R

EP

O R

T.

SM

AR

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FE

N

C E

P0

LA

R

IM

ER

C O

H

YD

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(F

IX

ED

-1 3-

).G

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AT

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G D

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/9 /1

5,485

5,490

5,495

5,500

5,505

5,510

5,515

5,520

5,525

5,530

5,535

5,540

5,545

0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000 5,480

5,485

5,490

5,495

5,500

5,505

5,510

5,515

5,520

5,525

5,530

5,535

5,540

5,545 0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000

BT-20.5 Ft.

B-12

BT-49.8 Ft.

B-13

BT-19.9 Ft.

B-14

BT-20.5 Ft.

B-15

NOTES:

Borehole Number

Liquid and Plastic Limits

AR

BT

LL PLMoisture Content %w

B-12

Water Level Reading at time of drilling.

Water Level Reading after drilling.

X X

Sampling (See General Notes)

El ev at io n -F ee t

Explanation

Borehole Lithology

Borehole Termination Type

Distance Along Baseline - Feet

Topsoil Poorly-graded Sand with Silt Silty Clay Colorado -

Claystone/Siltstone Sandy Lean Clay

Silty Sand Clayey Sand Silty Sand with Gravel Lean Clay Weathered

Rock

See Exploration Plan for orientation of soil profile.

See General Notes in Supporting Information for symbols and soil classifications.

Soils profile provided for illustration purposes only.

Soils between borings may differ AR - Auger Refusal BT - Boring Termination

SUBSURFACE PROFILE

Unit 1 W-E, Section E-E'

LARIMER CO HYDRO

NORTHEAST OF CR 11 AND CR 76

LARIMER COUNTY, CO

Project No.: 2019P031

Date: 1/17/2020

Scale: 1"=500' 1901 Sharp Point Dr, Ste C Fort Collins, COTH

IS

BO

R

IN

G

LO

G

IS

N O

T

VA

LI

D

IF

SE

PA

R

AT

ED

FR

O

M O

R

IG

IN

AL

R

EP

O R

T.

SM

AR

T

FE

N

C E

P0

LA

R

IM

ER

C O

H

YD

R O

(F

IX

ED

-1 3-

).G

PJ

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R R

AC

O

N _D

AT

AT

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PL

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G D

T

/9 /1

5,490

5,500

5,510

5,520

5,530

5,540

5,550

0 200 400 600 800 1,000 1,200 1,400 1,600 5,480

5,490

5,500

5,510

5,520

5,530

5,540

5,550 0 200 400 600 800 1,000 1,200 1,400 1,600

BT-49.8 Ft.

B-7

BT-50.0 Ft.

B-8

BT-20.0 Ft.

B-9

BT-19.4 Ft.

B-10

NOTES:

Borehole Number

Liquid and Plastic Limits

AR

BT

LL PLMoisture Content %w

B-7

Water Level Reading at time of drilling.

Water Level Reading after drilling.

X X

Sampling (See General Notes)

El ev at io n -F ee t

Explanation

Borehole Lithology

Borehole Termination Type

Distance Along Baseline - Feet

Topsoil Poorly-graded Sand with Silt Lean Clay Silty Sand with

Gravel Colorado - Claystone/Siltstone

Clayey Sand with Gravel

Lean Clay with Sand

Poorly-graded Sand with Clay and Gravel

Sandy Lean Clay Silty Clay

See Exploration Plan for orientation of soil profile.

See General Notes in Supporting Information for symbols and soil classifications.

Soils profile provided for illustration purposes only.

Soils between borings may differ AR - Auger Refusal BT - Boring Termination

SUBSURFACE PROFILE

Unit 1 W-E, Section F-F'

LARIMER CO HYDRO

NORTHEAST OF CR 11 AND CR 76

L…