8-8-MP27006-26032100 Geotechnical Report.pdf

PO Box 880 Midvale, Utah 84047

801.849.0055 gerhartcole.com

TECHNICAL MEMORANDUM

To: Kasey Chestnut, PE Horrocks Engineers 2162 W. Grove Parkway, Suite 100 Pleasant Grove, Utah 84062 Cell: (801) 687-8448 kaseyc@horrocks.com

From: Travis M. Gerber, PhD, PE

Reviewed by: Ryan Cole, PhD, PE, BCGE

Date: March 28, 2026

Job Number: 25-1962

Subject: Geotechnical Engineering Services USCF 0.5MG Tank

INTRODUCTION AND BACKGROUND

We understand that DFCM (Owner) desires to build a second, at-grade water tank to provide fire water at the Utah State Correctional Facility (USCF). Horrocks Engineers (Horrocks) has asked Gerhart Cole (GC) to provide geotechnical engineering support for its design of the tank. A second tank was originally contemplated during the original design and construction of the USCF, but it was removed from the project. We understand that this new second tank (to be ~0.5MG [~500k gallons] and smaller than the first) will be located near the first tank, at the site GC previously assessed and where there is an existing CPT sounding very near the footprint of the new tank (with other existing geotechnical data immediately adjacent to it; see Figure 1). Per Horrocks’ request, GC will rely upon existing geotechnical data in doing its work. The existing water tank is founded on rigid inclusion ground improvement (“GeoConcrete Columns” as designed and installed by Geopier Northwest, acting in a design-builder role). We understand that there are no concerns/reports of adverse performance for this existing tank. The new tank is expected to also be founded on some type of ground improvement. Final design of the ground improvement will be provided by the ground improvement specialty contractor selected for the project.

SCOPE OF WORK

Our work for this geotechnical study for the new, second water tank has been performed for Horrocks in general accordance with our proposal dated April 2, 2025, under the previously executed Subconsultant Services Master Agreement between Horrocks and Gerhart Cole dated April 18, 2024. The scope of work provided includes:

1. Reviewing GC’s existing geotechnical information for the tank area.

2. Providing geotechnical design recommendations and construction considerations for the new tank, including the working/fill platform for the tank.

mailto:kaseyc@horrocks.com

3. Providing guidance relative to select parameters to be considered in design of ground improvement by the specialty sub-contractor.

a. Part of this guidance will be a guide specification for the ground improvement, adapted from the specification used previously for the existing water tank.

i. Horrocks will need to insert some performance criteria into the specification (it will not fully be plug-and-play) consistent with its design criteria for the water tank and other improvements.

ii. Horrocks will need to coordinate the guide specification with other specifications and construction documents for the project.

4. Assessing potential interactions between the existing and new tanks, existing pump station, and existing cell tower using routine stress and one-dimensional settlement analyses (numerical analyses such as finite element are excluded).

5. Preparing this written technical memorandum (TM) which presents the results of the foregoing activities.

METHODS OF STUDY AND SITE CHARACTERIZATION

As requested by Horrocks, we have not collected new geotechnical surface data for the site; but rather, we have relied upon information gathered and developed during the original USCF design and construction effort. This information is presented/available in multiple documents prepared by Gerhart Cole for the USCF project, the most pertinent being:

1. “Geotechnical Study – Phase 2, Utah State Correctional Facility (USCF)” dated January 9, 2018.

2. “Geotechnical Study – Phase 4, Utah State Correctional Facility” dated October 30, 2018.

3. “Geotechnical Study – Phase 5 (Relocated Water Tanks), Utah State Correctional Facility” dated April 11, 2019.

The reader is referred to these documents for more information (such as regional geologic and seismological setting as well as test hole data, CPT sounding data, and laboratory test results from the USCF site) beyond the summary information presented herein. These reports and others relating to geotechnical aspects of the USCF are available from the Owner, DFCM.

The location of the new tank relative to existing facilities is provided in Figure 1.

Based on the subsurface data collected in the vicinity of the tank, the native subsurface soil profile may generally be described as follows. Below any fill placed since the original field studies were performed in 2019 (it should here be noted that existing contour information was requested but not provided to GC for this current study; the information that was provided indicates that the original ground surface at the new tank site is likely at approximate elevation 4220 feet), the uppermost native subgrade consists of soft to medium stiff silt (ML), silty clay (CL-ML), and clay (CL) along with loose to medium dense silty sand (SM) and poorly graded sand (SP), extending down to a depth of about 6 feet. These soils are in turn underlain by soft to medium stiff lean clay (CL) and high plasticity clay (CH) that generally extend to a depth of about 27 feet. Below this depth, there is a 10- to 11-foot thick medium dense to dense sand layer. This layer of sand could serve as the founding layer for ground improvement. Deeper soils consist of siltier and/or stiffer clays interbedded with some sand down to a depth of 50 feet. This layer of sand could also serve as the founding layer for ground improvement.

Additional site-specific subsurface information may be obtained from the cone penetrometer test (CPT) sounding 19-CPT-15 which was made in 2019 very near the new tank. A log for this sounding (together with sounding 19-CPT-16 made within the footprint of the nearby existing tank) is provided in Appendix A of this present document. When interpreting soil types from CPT results, it is important to recognize that the soil behavior type (SBT) index shown on the logs is determined by correlation, and actual soil types may vary; soil behavior type index is not the same as a Unified Soil Classification System (USCS) soil type which is typically shown on test hole log. It should be recognized that at the time that soundings 19- CPT-15 and 19-CPT-16 were made, the working platform placed widely within the USCF site had not yet been constructed in the area of the existing and new tanks. Additional information regarding sounding 19-CPT-15 and 19-CPT-16 is summarized in Table 1. It should be noted that any latitude, longitude, or elevation information shown on sounding logs in Appendix A is approximate, obtained in the field at the time of the field study without the benefit of a more traditional land survey. The location/position information shown in Table 1 provided by the USCF project team is considered to be more reliable.

Pore pressure dissipating testing performed at part of sounding 19-CPT-15 indicated that the piezometric surface was 2.1 feet below the ground surface. (A similar 2.7-foot depth was indicated at sounding 19-CPT-16; no records of groundwater levels during construction of the existing tank and pump station are available to GC). While water table depths can be evaluated from CPT pore pressure dissipation testing results, they can be affected by groundwater gradients. Also, it should be recognized that groundwater levels can fluctuate in response to irrigation, canal flow, construction activities, meteoric events, and with seasonal or longer-period changes. The Contractor should confirm current groundwater levels as part of his work.

GEOTECHNICAL DESIGN RECOMMENDATIONS

General

Based on information provided by the design team we understand that the new tank will be constructed as an above-grade, reinforced concrete structure, being approximately 68 feet in outside diameter and 22 feet tall (20-foot wall height plus an allowance for roof thickness).

The floor slab is expected to be integral with the wall and column foundations. With an anticipated finished top of floor elevation of 4226.0 feet, it appears that there will be an approximate 6-foot maximum grade change. In as site grading is critical to the assessment of settlement at the USCF site, if site grading or floor elevations change, design parameters and recommendations should be re-evaluated. We similarly recommend that the site Design Engineer (Horrocks) seek to keep site grading increases to a minimum to reduce adverse settlement risks.

Based on preliminary information from the Structural Engineer (Horrocks; see Appendix C), followed by several more recent iterations, the water depth in the tank is to be 19 to 20 feet (with 20 feet being used in our analyses). Column loads are to be approximately 70 kips (inclusive of dead) for the unfactored service case and 96 kips for the unfactored strength case (inclusive of dead, live, and snow loads). Walls load are to be approximately 5.2 kip/lineal foot for the unfactored service case and 5.6 kip/lineal foot for the unfactored strength case. A floor thickness has not been provided but has been estimated to be on the order of 24 inches, with a 6 inch reveal at its periphery.

Seismic Design Parameters

The basis of seismic design of original USCF facilities was either IBC 2015 (which derives from ASCE 7-10) or a site-specific ground response analysis which was developed for the project. Since that time, Utah’s state construction code has been revised. The current code is IBC 2021, but should be replaced with IBC 2024 later this year. We recommend that the more current ground motions of IBC 2024 (which derive from ASCE 7-22) be considered for design of the tank. It should also be recognized that with the newer code, seismic site classification definitions have changed. Given this, together with the presence of somewhat thinner and firmer clay at the new tank site as compared to USCF locations to the west and south, we characterize the site has having site class DE conditions. Seismic acceleration response spectrum parameters (corresponding to a 5% damping ratio) as obtained from USGS (see USGS, 2026a) are presented in Table 2. The “design response spectrum” parameters presented in the table have not been adjusted to account for any particular occupancy category or seismic importance factor, and are essential two-thirds of the MCEr values.

The MCE geometric mean peak ground acceleration (PGAm) provided in Table 2 is derived from the probabilistic seismic hazard analysis performed by the US Geological Survey as part of is 2018 National Seismic Hazard Mapping, which underlies IBC 2024.

Locally, this value generally represents ground motions having a 2% chance of exceedance in 50 years (i.e., 2PE50), and is typically used for non-structural geotechnical evaluations. evaluation. For deterministic-based analyses which require definition of a single “most representative” earthquake, modal values from a deaggregation of the probabilistic ground motion are commonly used. For a 2PE50 hazard level, the modal magnitude and distance pair (where distance is the closest site-to-source distance) associated with the peak ground acceleration is 7.09 and 12 km, respectively, which contributed about 25% of the hazard, based on USGS’ default binning (USGS, 2026b).

Tank Foundation

Inasmuch as soils at the USCF site are quite compressible even under relatively modest loadings, and with the tank presenting both significant column/wall loads and a widely distributed floor load, we do not believe that shallow or mat foundations are appropriate for the water tank. For the existing tank, GC recommended that a piled-raft foundation or ground improvement be considered for the water tank foundation system. Ground improvement was elected by the design team. Based on this precedent and the reportedly good performance of the existing tank, we recommend that ground improvement be used to support the new tank. Ground improvement may consist of one of many different types of technology, including aggregate piers or stone columns, rigid inclusions, compaction grouting, deep soil mixing, or jet grouting. In the case of the existing tank, a rigid inclusion-type of ground improvement (“GeoConcrete Columns” as designed and installed by Geopier Northwest) was used. The intent of the ground improvement used for new tank will be to improve bearing resistance and reduce settlement. We do not specify a single technology in order to allow potential specialty contractors the flexibility to provide the type of ground improvement which offers the best value for the Owner, consistent with performance criteria, although more favorable consideration should be given toward the technology used previously which has presented reportedly good performance for the existing tank.

Ground improvement is typically designed by a specialty contractor retained for the project. The special contractor’s designer will determine the number / spacing / depth / density of ground improvement foundation elements based on specified footing locations and structural loads. Loads to be used for design of ground improvement should be provided separately for dead, live, seismic, and other load cases. The reason for this differentiation of loads is that settlement performance is based on dead load (and any sustained live load) whereas strength performance (i.e., bearing capacity with respect to shear failure) is based on a critical combination of the various load types.

It should be recognized that when ground improvement is used, a range of allowable bearing capacities (i.e., resistances) can be selected as the basis for structural design of overlying foundation elements. The higher the capacity, the more robust the ground improvement design needs to be. Some particular high bearing capacities may not be attainable, or at least may not be economically acceptable. In the case of the tank, the loads from the three following elements should be considered: strips/walls, squares/columns, and floor mats/widely distributed loads.

Based on our assessment of potential ground improvement options, we believe that the following values are reasonable expectations for improved ground that the Structural Engineer may consider in the design of the tank. Actual capacities will be based on the design provided by the specialty contractor and the requirements of the specifications provided. It is therefore important that the Structural Engineer provide tank design-compatible criteria in the ground improvement performance specification. These criteria will need to be added to the preliminary specification template that GC has provided in Appendix B (Section 3.2.B). These criteria should also be submitted to GC for review to help assure consistency with previous GC analyses and preliminary loading estimates provided by the Structural Engineer.

As a preliminary structural design basis for the tank wall foundation (preliminary wall widths of 14 inches provided by Horrocks) with ground improvement, we believe that with respect to soil shear strength, an allowable bearing resistance on the order of

2.7 ksf may be used. For the preliminary 5.2 kip/foot dead load provided by the Structural Engineer and a minimum recommended width of 3 feet, we anticipate that a long-term settlement target of 1 inch or less may be used. These estimates are subject to confirmation by the ground improvement specialty contractor’s design.

As a preliminary structural design basis for tank column foundations (18-inch diameter columns provided by Horrocks) with ground improvement, we believe that with respect to soil shear strength, an allowable bearing resistance on the order of 3.3 ksf may be used. For the preliminary 70 kip dead load provided by the Structural Engineer and a minimum recommended width of 5.5 feet, we anticipate that a long-term settlement target of 1 inch or less may be used. These estimates are subject to confirmation by the ground improvement specialty contractor’s design.

As a preliminary structural design basis for the tank floor (thickness yet to be determined/communicated by Horrocks) with ground improvement, settlement rather than soil shear strength will control the allowable bearing pressure. For a long-term settlement target of 1 inch or less and in consideration of the proposed tank diameter, we anticipate that an allowable bearing resistance with respect to dead load in the range of up to 1.8 ksf may be used. This assessment assumes that the ground improvement beneath the floor is comparable in type and stiffness to that provided beneath the walls and columns. This estimate is subject to confirmation by the ground improvement specialty contractor’s design.

Because of the soft soil conditions present, we recommend that ground improvement extend beyond the outer edges of foundations, thereby providing additional confinement and strength to adjacent elements located directly beneath loads. This recommendation should be considered in project estimates and specifications. While the question of how much further ground improvement should extend beyond the outer edges of foundations is a matter to be answered in the analyses for final design, we believe that a distance of at least 14 feet (half the depth to the anticipated founding soil stratum) or 2 elements may be considered as a preliminary estimate.

Recognizing that relatively stiff ground improvement elements tend to cause slabs/mats to span softer soils between those elements, we recommend that the structural design of foundations and floors overlying ground improvement accommodate a maximum spacing of no more 8 feet between ground improvement elements (the actual structural design may require smaller spacing). This maximum spacing should be identified as a ground improvement design parameter. It should be recognized that the actual spacing provided in a final design may be less than the specified maximum.

As stated earlier, once established, design parameters and performance criteria for the tank foundations should be provided in a project specification that can be referenced and used by a ground improvement specialty contractor as he/she develops their design. A guide specification adapted for this project has been provided in Appendix B.

Earthwork

General

Based on our understanding of the project, grading will largely consist of fill placement with minimal cuts or excavation. Any excavations should comply with Occupational Safety and Health Administration’s (OSHA) construction standards [Standard for Excavations, 29 CFR Part 1926, Subpart P], as well as applicable state and local regulations. The Contractor should rely upon his own methods to determine and maintain safe and stable slopes during construction, subject to his particular construction procedures and those subsurface conditions more fully exposed during construction.

Fill materials supporting improvements where settlement or stability is of concern should not be placed in free water or on frozen ground. Compaction and/or proof-rolling of the subgrade or fill soils are ineffective if they are frozen. In no case should frozen materials, or materials that contain debris, organics, or deleterious substances, or materials that are reactive to metal or concrete, be used and placed as fill.

Site Subgrade Preparation and Fill Placement

During construction of the USCF, the existing subgrade soils were prepared by first minimally stripping the site. The root mat of existing grasses and weeds was generally left in place. The intent of this approach was to preserve, to the extent possible, the firmer surficial soil crust that exists in areas. Existing vegetation which is relatively sparse was closely mowed (residual of 1-1/2 inches or less; or burned [if allowed]) and the cuttings removed.

Larger roots of shrubs and/or trees were locally removed to a depth of 12 inches. We recommend that this process be followed for the new tank project. However, prior to this, any fill that has been placed in the footprint of the new tank during previous construction activities should be treated as being undocumented (unless otherwise assessed by the Geotechnical Engineer) and removed prior to preparation of the subgrade.

Stripping (vegetation and large root removal) operations should be observed by the Geotechnical Engineer to note if unstable, pumping subgrade conditions develop. In this event, the Contractor may need to resort to lighter-weight equipment, or track-mounted equipment to accomplish the required stripping.

Following stripping, the exposed subgrade should be proof-rolled with the type of equipment anticipated to be used in construction of the tank pad to identify any areas of significant instability. Initially, low ground pressure, track-mounted equipment should be used prior to using heavier equipment. Proof-rolling operations should be observed by the Geotechnical Engineer to note areas of concern. Where significant instability or pumping conditions are observed, these areas should be stabilized with the placement of clean, angular gravel and/or geotextile reinforcement fabric or geogrid. The Geotechnical Engineer should assess the severity of the conditions exposed and assist the Contractor in identifying an appropriate means to mitigate the unstable conditions.

The ground improvement specialty contractor may want to construct a working pad/platform from which to install ground improvement. This matter is largely a construction means-and-methods issue. The pad should be robust enough to support equipment and materials handling activities. Prior to its installation, we recommend that the subgrade be prepared as described above. Inasmuch as the platform typically provides better support than the native subgrade, it may be left in place after ground improvement installation, provided that the pad remains firm and has not become soft, rutted, or excessively fouled by fine grained soils. If such conditions exist (as judged by the Design Engineer), affected portions of the pad must be removed. The top of ground improvement elements may also need to be reworked to provide adequate subgrade support for overlying fill and/or foundations. The tops of ground improvement elements must be exposed and observed by the Design Engineer prior to placement of overlying fill and/or foundations. These considerations/requirements should be incorporated into project drawings and specifications.

It is anticipated that additional structural fill will need to be placed in the area of the ground improvement in order to reach the bottom of the tank floor. Based on preliminary site drawings, a 15-foot wide perimeter fill will also need to be placed adjoining the tank. These fills should consist of structural fill, prepared and placed in a manner similar to that used for the original USCF site, as presented below. It is important to recognize that fill will need to be placed and work stopped prior to construction of the tank, to allow settlements to take place, particularly in areas not underlain by ground improvement.

Placement of site fill and the placement of the working platform for the ground improvement will need to be coordinated. The working pad/platform used broadly through the USCF site may present challenges to subsequent installation of ground improvement. It is anticipated that the ground improvement working platform will be built first, becoming the lower portion of the USCF working pad (described below), and then be overlain by the remainder of structural fill needed to reach the grade of the tank.

During construction of the USCF, an initial “working pad” (“platform”) was typically constructed prior to placing other fill materials. After proof-rolling and subgrade preparation (and compaction of loose granular soils if found), it was recommended that the subgrade be overlain with a separation/reinforcement geotextile fabric, such as a Mirafi 600X or approved substitute. Fabric rolls should be overlapped a minimum of 1 foot, with greater overlap (2 feet or more) in areas of extreme rutting/pumping. It is critically important that the fabric be pulled and held taut as backfill is placed over the fabric. Care should be taken to avoid direct contact between the fabric and equipment tires or tracks. The fill should be back-dumped on the fabric or subgrade soil and spread with low-pressure tracked equipment.

An initial 12-inch thick layer of crushed rock would then be placed over the fabric. This material should consist of maximum 1-1/2-inch sized crushed rock with less than 5 percent passing the No. 4 mesh sieve. It is expected that this material will be such that a meaningful proctor test cannot be obtained; consequently, compaction will be assessed on a prescriptive/performance basis. This material should be compacted with a medium-weight, smooth drum, static roller under the observation of the Geotechnical Engineer, with the intent of producing as firm of lift as reasonably possible. The Geotechnical Engineer can assist the Contractor in establishing an optimal rolling pattern without over-stressing the subgrade.

The initial rock layer should then be overlain by a separation geotextile such as Mirafi 140N or approved substitute. Afterward, a 6-inch lift of select structural fill material is recommended to be placed over the separation geotextile. This material should meet criteria for A-1-a soil as designated by AASHTO M 145, with a maximum particle size of 1 inch. This material should be moisture conditioned to within 2 percent of optimum moisture content and ideally compacted to a minimum of 95 percent of the maximum dry density (MDD) as determined by ASTM D1557 (modified Proctor). However, for soft subgrade conditions, the minimum target compaction level of this initial lift of fill should be 90 percent of MDD (modified Proctor), but only subject to prior written approval by the Geotechnical Engineer. A second lift would then be placed, moisture-conditioned as above, and the compacted to a minimum of 95 percent of MDD (modified Proctor), resulting in a total 12-inch compacted thickness of select structural fill, inclusive of both lifts. It is important to recognize that there may be difficulty in achieving these levels of compaction, and the Geotechnical Engineer should be consulted to assess the causes and recommend remedial measures and/or modify the acceptance requirements. Without such input and indiscriminate attempts to achieve target compaction levels, there is potential for aggravating/destabilizing already challenging ground conditions.

Select structural fill (as described above) should continue to be placed below either structure foundations or slabs. Select structural fill should extend a minimum of 1 foot below the foundation and extend laterally beyond the edge of the foundation a minimum distance equal to the thickness of the fill, or 5 feet, whichever is greater. The material should be moisture conditioned, placed, and compacted as follows: the material should be within 2 percent of optimum moisture content, placed in approximately 10-inch loose lifts (or less if using smaller compaction equipment), and compacted to a minimum of 95 percent of the maximum dry density (MDD) as determined by ASTM D1557 (modified Proctor).

In the case of this tank, grading fill may be used in the areas outside/beyond the select structural fill used for the tank. Grading fill should meet criteria for A-2-4 or A-2-5 or better as designated by AASHTO M145. The material should be placed in maximum 10-inch loose lifts, moisture conditioned to within 2 percent of optimum moisture content. The material should be compacted to a minimum of 95 percent of MDD (modified Proctor). Locally-available pit-run materials may meet this gradation criteria. It should be noted, however, that if fill placement activities occur during extended wet weather conditions, the Contractor may elect to use an imported material with limited fines (15% or less passing the #200 mesh sieve) and a higher gravel content (maximum 50% passing the #4 mesh sieve). Such material will be less susceptible to instability under wet-weather placement conditions.

Stockpiling

Large and/or steeply sloped stockpiles can cause localized / differential settlements and possibly a failure of the soil subgrade. Consequently, large fill placements such as in stockpiles are to be avoided, and particularly near adjacent structures. Maximum allowable geometries would need to be assessed on a case-by-case basis; however, a conservative initial estimate is approximately 6 feet high. Similarly, it should be recognized that the timing of earthwork can have a significant effect on the performance of constructed works. For example, if one structure is built and a large load is later placed adjacent to the structure, the induced stresses in the ground from the load can initiate new (additional) settlement beneath the structure. In this case, the term “structure” may also be applied to subsurface utilities. Typically, stockpiling of materials is considered part of a contractor’s means-and-methods. However, for this project proper stockpiling of materials will need to be incorporated into the project documents to reduce settlement risks to existing surface or subsurface structures / utilities.

Additional Recommendations / Considerations

Frost Depth

A frost depth of 30 inches was used for the original design of USCF structures.

Soil Corrosion Considerations

The results of field and laboratory resistivity tests coupled with inorganic chemistry tests performed on soil samples within the USCF site indicate that the project site presents an aggressive environment with respect to corrosion of metallic elements and degradation of concrete. The reader is referred to previous study reports for additional information.

Drainage

Positive drainage should be established to carry any surface waters quickly away from structures and improvements, both during construction and afterward throughout the project’s design life.

SETTLEMENT IMPACTS FOR SELECT ADJACENT STRUCTURES

Estimated Settlements

Per Horrocks’ request, we have estimated settlements for the existing north tank, existing pump station, and existing cell tower based on the project drawings and the proposed grading shown thereon, provided to us by Horrocks (see Appendix C).

As a matter of reference, we calculate that without ground improvement, the center of the new tank would settle on the order of 9 to 10 inches.

We calculate that absence any ground improvement beneath the existing tank, the nearest point of the existing tank would settle about 1/4-inch due to the new tank and the fill around the new tank. Because there is ground improvement below the new tank, we expect that actual settlement would be less.

Due to the placement of the new tank and the fill surrounding it, we calculate that the nearest corner of the existing pump station would settle about 1/2-inch, provided that the revised finished grade tapers down to no new fill next to the pump station. We highly recommend that any increase in grade be kept to a minimum adjacent to the pump station.

At the nearest point on the fenceline surrounding the cell tower, we calculate ground settlement to be about 1/3-inch due to the placement of the new tank and the fill surrounding it.

While GC has provided estimates of settlement near/at select structures, GC has not assessed what the impacts of those settlements might be on functional and structural performance (particularly the cell tower). GC strongly recommends that other project team members perform such assessments.

Condition Surveys and Settlement Monitoring

GC recommends that pre-construction surveys and documentation of conditions be prepared for nearby existing structures, including the water tank, pump station, and cell tower. We also recommend that these same facilities be monitored throughout the duration of the project, and particularly during any vibratory activities associated with earthwork compaction or installation of ground improvement elements. Buried utilities in proximity to the new tank should also be documented and monitored. Instrument and settlement data should be reviewed and assessed by the Contractor and Geotechnical Engineer as soon as it is collected.

ADDITIONAL SERVICES

Subsurface conditions are inherently variable. It is important that we observe subsurface materials and conditions exposed during construction, thereby taking advantage of opportunities to recognize potentially differing site conditions and reducing the risk of unanticipated and/or adverse outcomes. Additional services critical to the success of this project and recommended by GC include, but are not necessarily limited to:

• Review of final designs, project plans, and specifications, for compatibility with our assessments and recommendations; particularly for the foundation of the water tank.

• Review of construction submittals for ground improvement.

• Observation of ground improvement installation.

o As a bare minimum, we recommend that GC be retained to make at least two site visits during construction. However, it is our opinion that more frequent visits and observations by qualified personnel are merited to provide a reasonable level of assurance that acceptable levels construction quality are being realized. This is in addition to the contractor’s specified quality control activities.

▪ GC is not responsible for site visits or observations not made due to lack of sufficient notice, funding, or coordination on the part of others.

• Review of ground improvement quality control/ assurance tests.

• Observation of earthwork activities, including clearing/grubbing, excavation, preparation of subgrade, placement and testing of fill for working/fill platform for the tank.

• Instrumentation installation and vibration/settlement monitoring during construction.

• Review and interpretation of settlement monitoring data.

• Consultation as may be required during construction.

Additional information regarding such services can be obtained from our office.

LIMITATIONS

The assessments and recommendations presented in this document are based on limited field studies and laboratory testing, as well as our understanding of the project’s design and manner of construction. If the project’s design or manner of construction changes, or if conditions are found that are different from those described, we should be notified immediately so that we can make revisions as necessary.

This document was prepared solely for the use of the addressee (our Client) for the specified project, and may not contain sufficient information for other parties or uses.

Excepting portions explicitly identified otherwise, this document does not constitute a specification and should not be treated or referred to as such in project design drawings or documents.

We represent that our services are performed within the limitations prescribed by our Client, in a manner consistent with the level of care and skill ordinarily exercised by other professional consultants under similar circumstances. No other representation, expressed or implied, and no warranty or guarantee is included or intended. We do not assume responsibility for the accuracy of information provided by others.

REFERENCES

United States Geological Survey [USGS]. (2026a). ASCE Hazard Tool.

https://ascehazardtool.org/

United States Geological Survey [USGS]. (2026b). Disaggregation.

https://earthquake.usgs.gov/nshmp/hazard/disagg.

FIGURE

Figure 1 Geotechnical Study Locations

TABLES

Table 1 Field Study Locations (select CPTs only) Table 2 ASCE 7-22 / IBC 2024 Seismic Design Parameters

APPENDICES

Appendix A Select Cone Penetration Test (CPT) Soundings Appendix B Guide Specification for Ground Improvement Appendix C Preliminary Drawings and Tank Loading Information by Horrocks

Parking Lot

Pump Station Nor th

P oin t C on so lid at ed

C an al

Cell Tower

1560 North

New 0.5MG Tank

Existing Water Tank

15-BH-06

16-TH-07

16-TP-0616-CPT-03

16-CPT-08

17-TP-09

17-CPT-18

17-CPT-22

17-CPT-23

17-CPT-24

17-CPT-25

18-TH-09

18-CPT-08

18-CPT-10

18-RMP-CPT-11

19-CPT-15

19-CPT-16

LEGEND

CPT - Tank Site

Previous Study Point

USCF 0.5MG TANK

Figure 1

0 150 30075

Feet

GEOTECHNICAL STUDY LOCATIONS

Service Layer Credits: Utah:

Nor th

P oin t C on so lid at ed

C an al

Study Point ID Date

Advanced

WGS 84 Latitude

(deg)

WGS 84

Longitude (deg)

Project

Northing a

Project

Easting a

Elevation

(ft) a

Total

Depth (ft)

Water Depth

(ft) b

19-CPT-15 2/26/2019 40.803314 -112.086306 7461897 1478094 4219.6 50.0 2.1

19-CPT-16 2/26/2019 40.803739 -112.086145 7462052 1478140 4219.8 50.0 2.7

Notes: a. Project survey information provided by design team; may be estimated in some cases.

b. CPT-based water depths calculated from PPD data at time of original study

Table 1: Field Study Locations

Site Class = DE TL (s) = 8

SS = 1.37 PGAM for MCEg (g) = 0.52

S1 = 0.47 SDS = 0.91

SMS = 1.37 SD1 = 0.83

SM1 = 1.24

T (s) Sa (g) T (s) Sa (g)

0 0.56 0 0.37

0.01 0.56 0.01 0.38

0.02 0.57 0.02 0.38

0.03 0.56 0.03 0.37

0.05 0.61 0.05 0.41

0.075 0.74 0.075 0.49

0.1 0.86 0.1 0.57

0.15 1.06 0.15 0.71

0.2 1.23 0.2 0.82

0.25 1.35 0.25 0.90

0.3 1.46 0.3 0.97

0.4 1.52 0.4 1.02

0.5 1.52 0.5 1.01

0.75 1.33 0.75 0.88

1 1.15 1 0.77

1.5 0.87 1.5 0.58

2 0.69 2 0.46

Notes: 1. Values reflect 5% damping ratio and importance factor of 1.0

MCER Response Spectrum Design Response Spectrum

Table 2: ASCE 7-22 / IBC 2024 Seismic Design

Parameters

Appendix A

Select Cone Penetration Test (CPT) Soundings

Cone Penetration Test Summary and

Standard Cone Penetration Test Plots

The reported coordinates were acquired from consumer grade GPS equipment and are only approximate locations. The coordinates should not be used for design purposes.

0 100 200 300 400 qt (tsf)

D e p th fe e t)

0.0 1.0 2.0 3.0 4.0 fs (tsf)

0 100 200 3000 u (ft)

0.0 2.0 4.0 6.0

Rf (%)

0 6 12

SBT

Gerhart Cole Job No: 19-52026

Date: 2019-02-26 10:44

Site: USCF

Sounding: 19-CPT-15

Cone: 553:T1500F15U500

Max Depth: 15.250 m / 50.03 ft Depth Inc: 0.025 m / 0.082 ft Avg Int: 0.150 m

File: 19-52026_CP15.COR Unit Wt: SBT (R&C1986)

SBT: Robertson and Campanella, 1986 Coords: Lat: 40.803289 Long: -112.086264

Clayey Silt Silt Clayey Silt Sandy Silt Clayey Silt Silt Clayey Silt Silt

Sensitive Fines

Silt

Sensitive Fines

Silt Clayey Silt Silt Sensitive Fines Silt

Sensitive Fines

Silt Silt

Silt

Sandy Silt

Sand

Silty Sand/Sand

Sand

Gravelly Sand

Gravelly Sand

Sand Sand Silt

Silty Sand/Sand Sandy Silt Silt

Sandy Silt

Silt Clayey Silt

Sandy Silt Silty Sand/Sand Sand Silt

29.3

Ueq(ft)

Target Depth Target Depth Target Depth Target Depth

Overplot Item: Assumed UeqUeq Dissipation, Ueq achieved Dissipation, Ueq not achieved Hydrostatic Line Phreatic Surface

The reported coordinates were acquired from consumer grade GPS equipment and are only approximate locations. The coordinates should not be used for design purposes.

qt (tsf)

D e p th fe e t)

0.0 1.0 2.0 3.0 4.0 fs (tsf)

0 100 200 3000 u (ft)

0.0 2.0 4.0 6.0

Rf (%)

0 6 12

SBT

Gerhart Cole Job No: 19-52026

Date: 2019-02-26 11:42

Site: USCF

Sounding: 19-CPT-16

Cone: 553:T1500F15U500

Max Depth: 15.250 m / 50.03 ft Depth Inc: 0.025 m / 0.082 ft Avg Int: 0.150 m

File: 19-52026_CP16.COR Unit Wt: SBT (R&C1986)

SBT: Robertson and Campanella, 1986 Coords: Lat: 40.803750 Long: -112.086138

Clayey Silt

Sensitive Fines

Silt Silty Sand/Sand Sandy Silt Clayey Silt Silt

Clay Sensitive Fines

Sensitive Fines Silt

Sensitive Fines

Clayey Silt Clayey Silt Sensitive Fines

Clayey Silt Sensitive Fines

Sensitive Fines Silt Sandy Silt Clayey Silt Clayey Silt Silt Silt

Silty Sand/Sand

Sand Silty Sand/Sand Sandy Silt

Sand

Gravelly Sand

Sand Silt

Sand Clayey Silt

Silt

Silty Sand/Sand Silt Clayey Silt

Silt

Sandy Silt

Silt

31.1

Ueq(ft)

Overplot Item: Assumed UeqUeq Dissipation, Ueq achieved Dissipation, Ueq not achieved Hydrostatic Line Phreatic Surface

Normalized Cone Penetration Test Plots

The reported coordinates were acquired from consumer grade GPS equipment and are only approximate locations. The coordinates should not be used for design purposes.

Qtn (PKR 2009)

D e p th fe e t)

0.0 1.0 2.0 3.0 4.0

Norm: Fr (%)

0 100 200 3000 u (ft)

0.0 1.0 2.0 3.0 4.0

Ic (PKR 2009)

0 3 6 9

SBT Qtn

Gerhart Cole Job No: 19-52026

Date: 2019-02-26 10:44

Site: USCF

Sounding: 19-CPT-15

Cone: 553:T1500F15U500

Max Depth: 15.250 m / 50.03 ft Depth Inc: 0.025 m / 0.082 ft Avg Int: 0.150 m

File: 19-52026_CP15.COR Unit Wt: SBTQtn (PKR2009)

SBT: Robertson, 2009 and 2010 Coords: Lat: 40.803289 Long: -112.086264

Sand Mixtures

Silt Mixtures Sands Silt Mixtures Sand Mixtures Silt Mixtures Sand Mixtures

Silt Mixtures

Sensitive, Fine Grained Sand Mixtures Silt Mixtures Sensitive, Fine Grained

Sand Mixtures Silt Mixtures

Silt Mixtures Sand Mixtures Silt Mixtures Sand Mixtures

Silt Mixtures

Sand Mixtures

Silt Mixtures Sand Mixtures Silt Mixtures Sand Mixtures

Sands

Sand Mixtures

Sands

Gravelly Sand to Sand

Sands

Silt Mixtures Sand Mixtures Sands

Silt Mixtures

Sand Mixtures

Silt Mixtures Clays Sand Mixtures

Sands Sand Mixtures

29.3

Ueq(ft)

Overplot Item: Assumed UeqUeq Dissipation, Ueq achieved Dissipation, Ueq not achieved Hydrostatic Line Phreatic Surface

The reported coordinates were acquired from consumer grade GPS equipment and are only approximate locations. The coordinates should not be used for design purposes.

Qtn (PKR 2009)

D e p th fe e t)

0.0 1.0 2.0 3.0 4.0

Norm: Fr (%)

0 100 200 3000 u (ft)

0.0 1.0 2.0 3.0 4.0

Ic (PKR 2009)

0 3 6 9

SBT Qtn

Gerhart Cole Job No: 19-52026

Date: 2019-02-26 11:42

Site: USCF

Sounding: 19-CPT-16

Cone: 553:T1500F15U500

Max Depth: 15.250 m / 50.03 ft Depth Inc: 0.025 m / 0.082 ft Avg Int: 0.150 m

File: 19-52026_CP16.COR Unit Wt: SBTQtn (PKR2009)

SBT: Robertson, 2009 and 2010 Coords: Lat: 40.803750 Long: -112.086138

Silt Mixtures

Clays

Sands Silt Mixtures Sand Mixtures

Clays

Sand Mixtures

Clays

Silt Mixtures

Sand Mixtures Silt Mixtures Sand Mixtures

Silt Mixtures

Sand Mixtures

Silt Mixtures Sand Mixtures

Sand Mixtures Sands

Sands

Sand Mixtures

Sands

Gravelly Sand to Sand

Sands

Sand Mixtures Sands

Silt Mixtures

Sand Mixtures

Silt Mixtures Clays

Silt Mixtures

Sand Mixtures

Silt Mixtures

31.1

Ueq(ft)

Overplot Item: Assumed UeqUeq Dissipation, Ueq achieved Dissipation, Ueq not achieved Hydrostatic Line Phreatic Surface

Pore Pressure Dissipation Summary and

Pore Pressure Dissipation Plots

0 250 500 750

0.0

10.0

20.0

30.0

40.0

Time (s)

P o re

P re ss u re ft

Gerhart Cole

Job No: 19-52026

Date: 26-Feb-2019 10:44:02

Site: USCF

Sounding: 19-CPT-15

Cone: 553 Area=15 cm²

Trace Summary:

Filename: 19-52026_CP15.PPD

Depth: 9.575 m / 31.414 ft

Duration: 600.0 s u Min: 2.5 ft u Max: 30.0 ft u Final: 29.3 ft

WT: 0.645 m / 2.115 ft

Ueq: 29.3 ft

0 250 500 750

0.0

10.0

20.0

30.0

40.0

50.0

Time (s)

P o re

P re ss u re ft

Gerhart Cole

Job No: 19-52026

Date: 26-Feb-2019 11:42:33

Site: USCF

Sounding: 19-CPT-16

Cone: 553 Area=15 cm²

Trace Summary:

Filename: 19-52026_CP16.PPD

Depth: 10.300 m / 33.792 ft

Duration: 600.0 s u Min: -5.8 ft u Max: 42.3 ft u Final: 31.2 ft

WT: 0.819 m / 2.689 ft

Ueq: 31.1 ft

Appendix B

Guide Specification for Ground Improvement

GROUND IMPROVEMENT FOR USCF 0.5MG TANK 316900- 1

GUIDE SPECIFICATION (DESIGN CRITERIA TO BE PROVIDED/VERIFIED IN SECTION 3.2.B)

SECTION 316900 – GROUND IMPROVEMENT FOR USCF 0.5 MG TANK

PART 1 - GENERAL

1.1 SCOPE

A. This specification addresses the design and construction of Ground Improvement for the USCF

0.5MG Tank (aka, South Water Storage Tank at the Utah State Correctional Facility).

B. The Specialty Subcontractor (Ground Improvement Contractor [GIC]) shall provide all labor, materials, and equipment to complete the Work. Work includes design, installation, monitoring, and testing of Ground Improvement.

C. Design of the Ground Improvement by the GIC shall meet specified performance requirements while conforming to additional information presented in Project Drawings and Specifications.

D. Ground Improvement may consist of one of several technologies, typically being those which reinforce the ground using discrete elements, to increase bearing resistance and reduce settlement. Potential technologies include:

1. Aggregate Piers (i.e., Vibro-Replacement Stone Columns or Rammed Aggregate Piers)

2. Compaction Grouting

3. Deep Soil Mixing

4. Jet Grouting

5. Lime Cement Columns

6. Vibro-Concrete Columns

7. Other technologies authorized by the Owner’s Representative.

Only one type of technology may be used per structure, unless otherwise authorized by the

Owner’s Representative. All Ground Improvement technology, designs, and work plans must be reviewed and authorized by the Owner’s Representative prior to mobilization.

E. Scope of work includes any pre-drilling or excavation needed to install the Ground

Improvement. This includes handling, temporary stockpiling, and final disposal of excavated material, spoils, or waste materials.

F. Scope of work includes construction, repair, and/or replacement of any working platform, load transfer platform, or pre-existing building pad.

GROUND IMPROVEMENT FOR USCF 0.5MG TANK 316900- 2

1.2 INTENT

A. The intent of the Ground Improvement specified herein is to improve bearing resistance and/or reduce settlement of soils, relative to new structure and appurtenances, consistent with the performance requirements (criteria) provided herein.

B. The intent of this Specification is to allow the Contractor the flexibility to provide the type of

Ground Improvement which provides the best value for the Owner, consistent with the requirements provided herein.

1.3 DEFINITIONS

A. As used in this specification, the term Contractor may refer to either the project’s General

Contractor or the Subcontractor retained to install the Ground Improvement / foundation system. The Subcontractor is also referred to as the Specialty Subcontractor or Ground

Improvement Contractor (GIC). The services (Work) provided by the Subcontractor include the design, installation, monitoring, and testing of the Ground Improvement.

B. Owner’s Representative is Geotechnical Engineer of Record for Owner, Gerhart Cole.

1.4 AVAILABLE INFORMATION

A. Information relative to subsurface conditions at the USCF site is available as “Information

Only” in the Project Documents, which includes:

1. “Geotechnical Study – Phase 1, Utah State Correctional Facility,” prepared for DFCM by

Gerhart Cole, dated January 31, 2017.

2. “Geotechnical Study – Phase 2, Utah State Correctional Facility,” prepared for DFCM by

Gerhart Cole, dated January 9, 2018.

3. “Geotechnical Study – Phase 3, Utah State Correctional Facility,” prepared for DFCM by

Gerhart Cole, dated March 22, 2018.

4. “Geotechnical Study, Utah State Correctional Facility (USCF) Offsite Improvements,” prepared for DFCM by Gerhart Cole, dated September 10, 2018.

5. “Geotechnical Study – Phase 4, Utah State Correctional Facility,” prepared for DFCM by

Gerhart Cole, dated October 30, 2018.

6. “Geotechnical Study – Phase 5 (Relocated Water Tanks), Utah State Correctional

Facility,” prepared for DFCM by Gerhart Cole, dated April 11, 2019.

7. “Geotechnical Study – USCF 0.5MG Tank” prepared for Horrock by Gerhart Cole, dated

March 2026.

GROUND IMPROVEMENT FOR USCF 0.5MG TANK 316900- 3

B. Opinions and recommendations presented or described in Information Only geotechnical study documents are based on interpretations of subsurface conditions, tests, and analyses conducted by the Owner. Information Only Geotechnical study reports or similar documents prepared for the Project include both factual and interpretive information. The test hole, cone penetration test (CPT) sounding, and test pit logs and similar study data accompanying the geotechnical study documents are believed to be factual and accurate but may not be fully representative of all conditions present. There is no guarantee regarding subsurface conditions at the site; subsurface conditions may vary between study locations, with depth, and with time. Variations between conditions indicated in the information provided and actual conditions found during the course of the work do not relieve the GIC of the responsibility to complete the work. The GIC will complete additional subsurface studies as necessary to further characterize the subsurface conditions at the site to the GIC’s satisfaction. Any references in Information Only geotechnical study reports to Ground Improvement are primarily conceptual or preliminary, for the purpose of evaluating project options, and do not represent a final design for Ground Improvement unless explicitly indicated otherwise.

1.5 CONTRACTOR QUALIFICATIONS

A. The GIC shall have a minimum of 5 years of experience with the installation of the type of

Ground Improvement to be used and shall have successfully completed at least 20 projects of similar size and scope.

B. The GIC’s field supervisor and key personnel shall have completed a minimum of 5 projects of similar size and scope in the last 2 years, utilizing similar equipment and methods which will be utilized on this project.

C. The GIC shall have and maintain Errors and Omissions (Professional Liability) insurance for the design, construction, and performance of the ground improvement. The insurance policy shall provide a minimum coverage of $2 million per occurrence, $3 million in aggregate.

D. The GIC’s designer engineer shall be a Professional Engineer licensed in the State of Utah, with a minimum of 5 years of experience in the design of the type of Ground Improvement to be used.

1.6 SUBMITTALS

A. The following shall be submitted to the Owner by the Contractor with the bid documents:

1. Qualifications of the GIC as described in Section 1.5.

2. Resumes of the management, supervisory, and key personnel for the GIC.

B. Design Report. Contractor shall submit a design report for the Ground Improvement / foundation system, including calculations and construction drawings, prepared by the GIC for review and authorization by the Owner.

GROUND IMPROVEMENT FOR USCF 0.5MG TANK 316900- 4

1. The design report should be submitted for authorization at least 3 weeks before beginning installation.

2. The report, calculations, and drawings shall be sealed by a Professional Engineer licensed in the State of Utah.

a. Working drawings showing the identification number; dimensions (such as diameter); layout; planned…