Exhibit D_Geotechnical Study_101 W Main RFP.pdf

240 Annie Road | PO Drawer 1887

Silverthorne, Colorado 80498

Fax: (970) 468-5891

Phone: (970) 468-1989

Email: hpksummit@kumarusa.com

Office Locations: Denver (HQ), Colorado Springs, Fort Collins, Glenwood Springs Parker and Summit County, Colorado

GEOTECHNICAL ENGINEERING STUDY

PROPOSED MULTI-FAMILY AFFORDABLE HOUSING DEVELOPMENT

LOT B-1, AMENDED WEST FRISCO 70, FILING #2

101 WEST MAIN STREET

FRISCO, COLORADO

Prepared by: Reviewed by:

James A. Parker, P.E, P.G Steven L. Pawlak, P.E.

PREPARED FOR:

ALLEN-GUERRA ARCHITECTURE

ATTN: SUZANNE ALLEN-SABO

P.O. BOX 5540

FRISCO, COLORADO 80443

suzanne@allen-guerra.com

Project No. 23-6-231 December 14, 2023

EXHIBIT D

mailto:suzanne@allen-guerra.com

TABLE OF CONTENTS

PURPOSE AND SCOPE OF STUDY

PROPOSED CONSTRUCTION

SITE CONDITIONS

FIELD EXPLORATION

LABORATORY TESTING

GEOTECHNICAL ENGINEERING CONSIDERATIONS

SITE GRADING

FOUNDATIONS

FOUNDATION AND RETAINING WALLS

FLOOR SLABS

EXTERIOR FLATWORK

UNDERDRAIN SYSTEM AND DAMPPROOFING

SURFACE DRAINAGE

CONTINUING SERVICES

LIMITATIONS

FIG. 1 – LOCATION OF EXPLORATORY PITS

FIG. 2 – LOGS OF EXPLORATORY PITS

FIG. 3 – GRADATION TEST RESULTS

FIG. 4 – TYPICAL DRAIN DETAIL

TABLE 1 – SUMMARY OF LABORATORY TEST RESULTS

PURPOSE AND SCOPE OF STUDY

This report presents the results of a geotechnical engineering study for a proposed multi-family affordable housing development, located at Lot B-1, Amended West Frisco 70, Filing #2, with a physical address of 101 West Main Street, Frisco, Colorado. The project site is shown on Fig.

1. The purpose of the study was to develop recommendations for the foundation design. The study was conducted in accordance with our proposal for geotechnical engineering services, dated November 27, 2023, Proposal P6-23-287.

A field exploration program consisting of exploratory pits and a site reconnaissance was conducted to obtain information on the surface and subsurface conditions. Samples of the subsoils obtained during the field exploration were tested in the laboratory to determine their classification and other engineering characteristics. The results of the field exploration and laboratory testing were analyzed to develop recommendations for foundation types, depths and allowable pressures for the proposed structure foundations. This report summarizes the data obtained during this study and presents our conclusions, design recommendations and other geotechnical engineering considerations based on the proposed construction and the subsoil conditions encountered.

PROPOSED CONSTRUCTION

We understand that the project will consist of the construction of a multi-family affordable housing building, associated infrastructure, and parking and drive lanes on the subject site, as shown on Figure 1. Review of preliminary plans indicate the structure will be a three-level building, with a slab-on-grade lower-level, and at-grade parking. Grading for the project is assumed to be relatively minor to moderate with anticipated cuts of up to about 4 to 6 feet below the adjacent ground surface. We assume relatively light foundation loads, typical of the proposed type of construction.

When final building locations, plans, grading and loading information have been developed, we should be notified to re-evaluate the recommendations presented in this report.

SITE CONDITIONS

The project site is an approximate 0.83-acre lot, located at the northeast corner of Creekside

Drive and West Main Street, as shown on Figure. 1. At the time of our exploration the site was occupied with a commercial building in the northern portion of the lot and paved parking area in the central and south portions of the lot. The majority of the site was relatively flat, with a slope down to the north at the northern edge of the lot. The lot is bordered by Creekside Drive to the

Kumar and Associates west, West Main Street to the South, a condominium development to the east, and 10-mile

Creek to the North.

FIELD EXPLORATION

The field exploration for the project was conducted on December 7, 2023. Two exploratory pits were excavated, as site access and underground utilities allowed, at the approximate locations shown on Fig. 1 to evaluate the subsurface conditions. The pits were excavated with a tracked mini-excavator and logged by a representative of Kumar and Associates, Inc.

Samples of the subsoils were taken with disturbed sampling methods. Depths at which the samples were taken are shown on the Logs of Exploratory Pits, Fig. 2. The samples were returned to our laboratory for review by the project engineer and testing.

LABORATORY TESTING

Samples of soils obtained from the exploratory pits were visually classified in the laboratory by the project manager and samples were selected for laboratory testing. Laboratory testing performed on samples obtained from the pits consisted of natural moisture content, percent passing the No. 200 sieve and gradation analysis. Results of a gradation analysis performed on the minus 1½-inch fraction of the natural coarse granular soils are shown on Figure 3. The laboratory test results are summarized on the Logs of Exploratory Pits, Fig. 2, and on Table 1.

SUBSURFACE CONDITIONS

Soil Types Encountered: Graphic logs of the subsurface conditions encountered at the site are shown on Fig. 2. Subsoils encountered in the exploratory pits consisted of 1 and 3 feet of existing fill, related to existing site development. The fill was comprised of silty sand, gravel and cobbles, with scattered organics. Underlying the fill, the natural soils consisted of medium dense, poorly graded silty gravel (GP-GM) with sand, cobbles, and small boulders, extending to the full depth of exploration of 9 feet. Excavating the coarse granular soils was difficult, and practical refusal to excavation occurred in Pit 1 at a depth of 6 feet below the existing site grade on cobbles and boulders.

Groundwater: Free water was not encountered in the pits at the time of excavation, and the pits were backfilled after sampling. Subsoils were general slightly moist to moist. In mountainous areas it has been our experience that groundwater depths may fluctuate seasonally and perched water or zones of moist to wet soils can occur within the soil profile.

GEOTECHNICAL ENGINEERING CONSIDERATIONS

Subsurface data indicates that existing man-placed fill and medium dense, poorly graded silty gravel, with sand, cobbles, and boulders, will likely be the predominant materials encountered beneath shallow foundation, floor slab, flatwork and pavement areas. The natural granular soils at anticipated foundation levels are generally considered good to excellent for shallow foundation support. Existing fill, and building, utility and pavement remnants should be removed from development areas and replaced with properly compacted structural fill, as needed, to re-establish finish grades.

At the time of our field exploration access for subsurface exploration was limited due to the existing development and underground utilities. Based on our professional experience in the project area, subsurface conditions encountered in the exploratory pits were consistent with expected conditions at the project site. Kumar & Associates should be contacted to evaluate the exposed subgrade in proposed building and parking areas following demolition of the existing building and removal of the existing parking area pavement, to verify the recommendations presented in this report and recommend additional subsurface exploration, if warranted.

SITE GRADING

The following recommendations should be followed for grading, site preparation, and fill compaction.

1. Where fill is to be placed, existing fill, organics, and building, utility or pavement remnants, and loose, disturbed, or otherwise unsuitable material should be removed prior to placement of new fill. The exposed soils should then be scarified to a depth of 6 inches, moisture conditioned and compacted to the minimum requirements of the overlying fill. Soils should be compacted with appropriate equipment for the lift thickness placed. Lift thickness should be no more than 10 loose inches subsequently compacted at the recommended moisture content and to the minimum required density.

2. Permanent unretained cut and fill slopes should be graded at 2 horizontal to 1 vertical

(2:1) or flatter and protected against erosion by revegetation or other means. The risk of slope instability will be increased if seepage is encountered in cuts and flatter slopes may be necessary. If seepage is encountered in permanent cuts, an investigation should be conducted to determine if the seepage will adversely affect the cut stability.

This office should review site grading plans for the project prior to construction.

3. Slopes of 4:1 or steeper should be benched to provide a level surface for compaction.

4. All backfill should be processed so that it does not contain fragments larger than

6-inches in diameter and placed at the recommended moisture content.

5. The following compaction requirements should be used:

TYPE OF FILL

PLACEMENT

MOISTURE

CONTENT

SOIL TYPE - Compaction Percent

(ASTM D698 – Standard Proctor)

Below Foundations 2% Optimum Structural Fill – 98%

Foundation Wall

Backfill 2% Optimum Processed On-site or Structural Fill – 95%

Below Floor Slabs 2% Optimum Structural Fill – 95%

Landscape Areas 2% Optimum Processed On-site – 90%

Below Concrete

Flatwork/Pavements 2% Optimum Structural Fill – 95%

Utility Trenches As they apply to the finished area

Suitability of On-Site Soil Poorly graded silty gravel with sand, cobbles and boulders was encountered across the project.

site and is anticipated in foundation excavations. The on-site gravel soils are suitable as backfill after processing to remove all plus 6-inch material and moisture treatment. The existing fill should be suitable or use as backfill, following processing to remove over-size rock and deleterious material, but should be evaluated by Kumar & Associates for suitability at the time of excavation.

Considerable processing will be necessary to reduce the on-site soil to fragments of minus 6-inches. Processing may include screening, rock raking and crushing. All on-site soil should be processed, moisture-conditioned and placed to at least the minimum required compaction.

Structural Fill Structural fill used for support of the building, concrete flatwork and pavement areas should consist of processed on-site granular soils, clean existing fill, or a relatively well-graded imported granular material with a liquid limit of 35 or less, a plasticity index of 10 or less, 5 to 25 percent material passing the No. 200 sieve, 60 percent or more passing the No. 4 sieve and no rocks larger than 6 inches. CDOT Class 1 structural backfill is acceptable as structural fill.

Structural fill should be properly placed and compacted to reduce the risk of settlement and distress. Structural fills should be placed in accordance with the recommendations presented in the SITE GRADING section of this report.

Import Fill The Geotechnical engineer should evaluate the suitability of any proposed import fill for its intended use.

Excavations It is the responsibility of the Contractor to provide safe working conditions and to comply with the regulations in OSHA Standards, Excavations, 29CFS Part 1926. The onsite gravel soils will classify as “Type C” in accordance with OSHA regulations. The regulations allow slopes of 1½ horizontal to 1 vertical (1½:1) for dry temporary excavations less than 20 feet deep.

The presence of water, seepage, fissuring, vibrations or surcharge loads will require temporary excavation to have flatter slopes. The excavation contractor’s Competent Person should make decisions regarding cut slopes. A qualified Geotechnical engineer should observe any questionable slopes or conditions. Temporary shoring may be necessary.

FOUNDATIONS

Considering the subsoil conditions encountered in the exploratory pits and the nature of the proposed construction, we recommend the structure be founded with spread footings bearing on the undisturbed natural granular soils or properly compacted structural fill.

The design and construction criteria presented below should be observed for a spread footing foundation system.

1) Footings placed on the undisturbed natural granular soils or properly compacted structural fill should be designed for an allowable soil bearing pressure of 3,000 pounds per square foot (psf). Based on experience, we expect settlement of footings designed and constructed as discussed in this section will be about 1 inch or less.

2) The footings should have a minimum width of 18 inches for continuous walls and 2 feet for isolated pads.

3) Exterior footings and footings beneath unheated areas should be provided with adequate soil cover above their bearing elevation for frost protection. Placement of foundations at least 40 inches below exterior grade is recommended for foundations bearing on the native soils. Concrete should not be placed on frost, frozen soil, snow or ice.

4) Continuous foundation walls should be reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 10 feet. Foundation walls acting as retaining structures should also be designed to resist lateral earth pressures as discussed in the "Foundation and Retaining Walls" section of this report.

5) Existing fill, and building, utility, and pavement remnants, and any loose or disturbed soils should be removed, and the footing bearing level extended down to the relatively undisturbed natural granular soils. The exposed soils in footing areas should then be moistened to near optimum moisture, if necessary, and compacted. If water seepage is encountered, the footing areas should be dewatered before concrete placement and we shall be contacted for further evaluation.

6) Voids created by boulder removal in foundation areas should be backfilled with properly compacted structural fill, lean mix concrete or structural concrete to re-establish bearing elevations.

7) Structural fill used for support of the foundation should meet the requirements listed in the SITE GRADING section of this report.

8) A representative of the geotechnical engineer should observe all footing excavations prior to forming footings and concrete placement to evaluate bearing conditions.

FOUNDATION AND RETAINING WALLS

Foundation walls and retaining structures which are laterally supported and can be expected to undergo only a slight amount of deflection should be designed for a lateral earth pressure computed on the basis of an equivalent fluid unit weight of at least 50 pounds per cubic foot

(pcf) for backfill consisting of the on-site processed granular soils. Cantilevered retaining structures which are separate from the foundation and can be expected to deflect sufficiently to mobilize the full active earth pressure condition should be designed for a lateral earth pressure computed on the basis of an equivalent fluid unit weight of at least 40 pcf for backfill consisting of the processed on-site granular soils. The backfill should not contain rock larger than about 6 inches in diameter.

The lateral resistance of foundation or retaining wall footings will be a combination of the sliding resistance of the footing on the foundation materials and passive earth pressure against the side of the footing. Resistance to sliding at the bottoms of the footings can be calculated based on a coefficient of friction of 0.45. Passive pressure of compacted backfill against the sides of the footings can be calculated using an equivalent fluid unit weight of 420 pcf. The coefficient of friction and passive pressure values recommended above assume ultimate soil strength.

Suitable factors of safety should be included in the design to limit the strain which will occur at the ultimate strength, particularly in the case of passive resistance. Fill placed against the sides of the footings to resist lateral loads should be an on-site soil granular material compacted to at least 95% of the maximum standard Proctor dry density at a moisture content near optimum.

All foundation and retaining structures should be designed for appropriate hydrostatic and surcharge pressures such as adjacent footings, traffic, construction materials and equipment.

The pressures recommended above assume drained conditions behind the walls and a horizontal backfill surface. The buildup of water behind a wall or an upward sloping backfill surface will increase the lateral pressure imposed on a foundation wall or retaining structure.

An underdrain should be provided to limit hydrostatic pressure buildup behind walls.

Backfill in patio, pavement, and walkway areas should be placed in uniform lifts and compacted to at least 95% of the maximum standard Proctor (ASTM D-698) dry density. Backfill placed in landscape areas should be compacted to at least 90% of the maximum standard Proctor dry density at a moisture content near optimum. Care should be taken not to over-compact the backfill or use large equipment near foundation and retaining walls, since this could cause excessive lateral pressure on the wall. Some settlement of deep foundation wall backfill should be expected, even if the material is placed correctly, and could result in distress to facilities constructed on the backfill.

FLOOR SLABS

The natural on-site granular soils are suitable to support lightly loaded slab-on-grade construction. Existing fill, and building, utility and pavement remnants, should be removed from floor slab areas and replaced with properly compacted new structural fill to re-establish floor slab bearing elevations.

To reduce the effects of some differential movement, floor slabs should be separated from all bearing walls and columns with expansion joints which allow unrestrained vertical movement.

Floor slab control joints should be used to reduce damage due to shrinkage cracking. The requirements for joint spacing and slab reinforcement should be established by the designer based on experience and the intended slab use. A minimum 4-inch layer of free-draining gravel should be placed beneath below-grade slabs (if constructed) to facilitate drainage. This material should consist of minus 2-inch aggregate with at least 50% retained on the No. 4 sieve and less than 2% passing the No. 200 sieve. All backfill under floor slabs should be placed in accordance with the SITE GRADING section of this report. Proper drainage design to prevent wetting of the under-slab soils will be important in reducing the potential for slab movement.

We recommend vapor retarders conform to the minimum requirements of ASTM E1745 Class B material. Certain floor types are more sensitive to water vapor transmission than others. For floor slabs bearing on angular gravel or where flooring system sensitive to water vapor transmission are utilized, we recommend a vapor barrier be utilized conforming to the minimum requirements of ASTM E1745 Class A material. The vapor retarder should be installed in accordance with the manufacturers’ recommendations.

Structural fill placed beneath slabs can consist of processed on-site granular soils, excluding organics and oversized rocks, or an imported well-graded granular material. Structural fill should be spread in thin horizontal lifts, adjusted to at or above optimum moisture content, and compacted to at least 95% of the maximum standard Proctor dry density. All existing fill, organics, building or utility remnants, and loose or disturbed soil should be removed prior to fill placement.

EXTERIOR FLATWORK

Structural fill placed beneath exterior flatwork can consist of processed on-site granular soils excluding topsoil and oversized rocks or an imported well-graded granular material. Structural fill should be spread in thin horizontal lifts, adjusted to at or above optimum moisture content, and compacted to at least 95% of the maximum standard Proctor dry density. All existing fill, vegetation, topsoil and loose or disturbed soil should be removed prior to fill placement.

UNDERDRAIN SYSTEM AND DAMPPROOFING

Although groundwater was not encountered in the exploratory pits, it has been our experience in mountainous areas that the water level can rise and that local perched groundwater can develop during times of heavy precipitation or seasonal runoff. Frozen ground during spring runoff can create a perched condition. We recommend below-grade construction, such as retaining walls and crawlspace areas (if constructed), be protected from wetting and hydrostatic pressure buildup by an underdrain and wall drain system. Slab-on-grade, at-grade construction, should not require a foundation drain.

The underdrain should consist of drainpipe placed in the bottom of the wall backfill surrounded above the invert level with free-draining gravel. The drain should be placed at each level of excavation and at least 12-inches below lowest adjacent finish grade and sloped at a minimum

1% to a suitable gravity outlet, sump and pump system or drywell. Free-draining gravel used in the underdrain system should contain less than 2% passing the No. 200 sieve, less than 50% passing the No. 4 sieve and have a maximum size of 1-inch. The drain gravel backfill should be at least 1½ feet deep and protected by filter fabric. A typical drain detail is shown on Figure 4.

For exterior below grade foundation walls, we recommend, as a minimum, damp proofing consist of bituminous material, 3 lbs per square yard, extending from the top of the footing to above ground level. A wall drain system consisting of a geocomposite, MiraDrain 6000, or equivalent, should be placed adjacent to below grade construction walls, with 100 percent coverage on the foundation wall facing the uphill slope and a minimum of 50 percent coverage for the adjacent foundation walls. The wall drain system should connect into the underdrain and extend to within 1 to 2 feet of the ground surface.

SURFACE DRAINAGE

The following drainage precautions should be observed during construction and maintained at all times after the structure has been completed:

1) Inundation of the foundation excavations and underslab areas should be avoided during construction.

2) Backfill in slab areas should be compacted to at least 95% of the maximum standard

Proctor dry density at a moisture content within 2% of optimum. Exterior backfill placed in landscape areas should be compacted to at least 90% of the maximum standard

Proctor dry density at a moisture content near optimum.

3) The ground surface surrounding the exterior of the buildings should be sloped to drain away from the foundation in all directions. We recommend a minimum slope of 6 inches in the first 10 feet in unpaved areas and a minimum slope of 2½ inches in the first 10 feet in paved areas.

4) Roof downspouts and drains should discharge well beyond the limits of all backfill.

5) Landscaping which requires regular heavy irrigation should be located at least 5 feet from foundation walls. The upper 2 feet of foundation wall backfill should consist of relatively impervious cover soil.

CONTINUING SERVICES

Two additional elements of geotechnical engineering service are important to the successful completion of this project.

1) Consultation with design professionals during the design phases. This is important to ensure that the intentions of our recommendations are properly incorporated in the design, and that any changes in the design concept properly consider geotechnical aspects.

2) Observation and monitoring during construction. A representative of the Geotechnical engineer from our firm should observe the foundation excavation, earthwork, and foundation phases of the work to determine that subsurface conditions are compatible with those used in the analysis and design and our recommendations have been properly implemented. Placement of backfill should be observed and tested to judge whether the proper placement conditions have been achieved. We recommend a representative of the geotechnical engineer observe the drain and damp-proofing phases of the work to judge whether our recommendations have been properly implemented.

LIMITATIONS

This study has been conducted in accordance with generally accepted geotechnical engineering principles and practices in this area at this time. We make no warranty either express or implied. The conclusions and recommendations submitted in this report are based upon the data obtained from the exploratory pits at the locations indicated on Figure 1, the proposed type of construction and our experience in the area. Our services do not include determining the presence, prevention or possibility of mold or other biological contaminants (MOBC) developing in the future. If the client is concerned about MOBC, then a professional in this special field of practice should be consulted. Our findings include interpolation and extrapolation of the subsurface conditions identified at the exploratory pits and variations in the subsurface conditions may not become evident until excavation is performed. If conditions encountered during construction appear different from those described in this report, we should be notified so that re-evaluation of the recommendations may be made.

This report has been prepared for the exclusive use by our client for design purposes. We are not responsible for technical interpretations by others of our information. As the project evolves, we should provide continued consultation and field services during construction to review and monitor the implementation of our recommendations, and to verify that the recommendations have been appropriately interpreted.

Pit 1

Pit 2

Proposed Building

*Pit Locations are Approximate

0 25' 50'

Approximate Scale

*Pit Locations are Approximate

0 25' 50'

Approximate Scale

Kumar & Associates

FOUNDATION WALL

BACKFILL SURFACE

10 PERCENT MINIMUM

SLOPE FOR LANDSCAPE

AREAS OR 3 PERCENT FOR

FLATWORK / ASPHALT FOR

10 FEET

FILTER FABRIC

DRAIN GRAVEL

DRAIN PIPE

TOP OF SLAB / LOWER LEVEL FLOOR

1' MINIMUM

VAPOR RETARDER

RELATIVELY IMPERVIOUS

BACKFILL IN THE UPPER 2

FEET OR FLATWORK /

ASPHALT

1. DRAIN PIPE - consists of 4-inch perforated PVC, surrounded by a minimum of 4 inches of drain gravel on the top and sides, sloped at 1 percent to a gravity discharge or drywell.

Bottom of pipe at the high point should be a minimum of 12-inches below the top of the floor.

2. DRAIN GRAVEL - consists of minus 1-inch aggregate with less than 50 percent passing the No. 4 sieve and less than 2 percent passing the No. 200 sieve. Drain gravel should fill the entire trench a be a minimum of 18 inches deep. A minimum of 4 inches of drain gravel is recommended under basement level concrete floors to facilitate drainage. The drain gravel under the slab should be connected to the perimeter drain system or connected directly to the drywell by perforated, rigid pipe under the slab or perforation in the drywell by means of piping under the footing on the downhill side of the building or other approved method.

3. VAPOR RETARDER - consists of a minimum 10-mil vapor retarder meeting the minimum requirements of ASTM E1745 Class C material, adequately overlaped and sealed. Vapor retarder should be installed in accordance with the manufacturers specifications.

4. FILTER FABRIC - protect drain gravel and drain pipe with Mirafi 180N, or equivalent.

DAMPPROOFING

DRAIN GRAVEL

WALL DRAIN

5. WALL DRAIN - consists of MiraDRAIN 6000 or equivalent.

NOT TO SCALE

JOB NO: 23-6-231

PROPOSED MULTI-FAMILY DEVELOPMENT 101 W. MAIN STREET TABLE 1

NATURAL NATURAL HVEEM WATER SOIL OR

MOISTURE DRY UNIT SILT & LIQUID PLASTIC SUR- STABILOMETER SOLUBLE BEDROCK

PIT DEPTH CONTENT WEIGHT GRAVEL SAND CLAY LIMIT INDEX SWELL CHARGE (R-VALUE) SULFATES DESCRIPTION

(#) (feet) (%) (pcf) (%) (%) (%) (%) (%) (%) (psf) (%)

1 1 6.1 11 POORLY GRADED SILTY GRAVEL WITH SAND

5 4.1 5 POORLY GRADED SILTY GRAVEL WITH SAND

2 2 5.4 13 59 28 FILL: SILTY SAND WITH GRAVEL

8 3.4 10 POORLY GRADED SILTY GRAVEL WITH SAND

JOB NAME:

SUMMARY OF LABORATORY TEST RESULTS

SAMPLE

LOCATION

GRADATION ATTERBERG LIMITS SWELL-COMPRESSION