A2_CDO_Soils_FinalReport.pdf

Geotechnical Investigation

USFS District Office

136471 Hwy 97, Crescent , Oregon

Project No: 2129055-900

Prepared by:

FEI Testing & Inspection, Inc.

62979 NE Plateau Drive, #3

Bend, Oregon 97701

July 5, 2012

Project No: 2129055-900 USFS District Office

Contents

1 INTRODUCTION 1

1.1 Site Location

1.2 Site Conditions

1.3 Proposed Construction

2 GEOLOGIC SETTING 2

3 FIELD EXPLORATIONS & TESTING 2

3.1 Subsurface Exploration & Testing

3.2 Subsurface Conditions

4 LABORATORY TESTING 3

5 CONCLUSIONS & RECOMMENDATIONS 4

5.1 Seismic Design Parameters

5.2 Foundation & Lateral Design Criteria

5.3 Pavement Design

5.4 Grading of Building and Pavement Areas

5.5 General Site Grading

5.6 Inspection and Testing

5.7 Preliminary Stormwater Disposal

6 LIMITATIONS 9

7 REFERENCES 9

Figure 1 – Geologic & Vicinity Map

Figure 2 – Site Map

Appendix A – Test Pit Logs

Appendix B – Laboratory Test Results

July 5, 2012

1 INTRODUCTION

This report presents results of a geotechnical exploration performed by FEI Testing & Inspection, Inc. (FEI) at the site of a proposed office project in Crescent, Oregon. The purpose of the exploration is to provide information and design guidelines for:

• Seismic Design Criteria

• Foundation and Lateral Design Criteria

• Slab-on-grade Design

• Pavement Section Design

• Excavations and Site Grading

• Construction Observation and Testing

• Preliminary Stormwater Disposal

The recommendations, conclusions, and opinions presented in this report are based on our field observations and laboratory testing, published geologic data for the area, and our experience with similar projects. A topographic map of the site was provided for our reference during the investigation, and forms the basis of the site map in this report.

1.1 Site Location

The project site is located on the east side of Highway 97, south of Crescent Cut-off Road, in Crescent, Oregon. The site is generally described as lying within the southwest quarter of Section 30, Township 24 South, Range 9 East, Willamette Meridian, Klamath County, Oregon. The proposed building site is a portion of the Crescent Administrative Site at 136471 Hwy 97. A Geologic and Vicinity Map showing the general location is shown on Figure 1.

1.2 Site Conditions

The site is located in generally level terrain, which locally slopes towards the west at gradients of less than 1 percent. The area consists of mostly paved parking areas, inter-spersed with buildings and landscaping. The project area is bounded by Highway 97 on the west, Main Street on the east, and light commercial type and residential buildings on the north and south.

July 5, 2012 1

1.3 Proposed Construction

Preliminary information for the proposed construction includes a fire equipment building near the existing office complex on the south, and an office building on the north, with parking areas and landscaping. The construction type is expected to consist predomi-nantly of wood or steel framing, supported by individual columns and continuous wall footings. Maximum loads are anticipated to be on the order of 100 kips, with wall loads to continuous footings of up to 5 kips/ft. We have also assumed that soil supported ground floor loads will not exceed 300 pounds per square foot (psf). Grade changes for the building pads are expected to be relatively minor, with maximum cuts and fills of about 3 feet. Paved access streets and buried utilities will be included in the de-velopment. Stormwater will be collected and directed to shallow infiltration ponds or swales.

2 GEOLOGIC SETTING

The project site lies within the relatively wide basin of the Little Deschutes River, on an extensive series of alluvial and air-fall deposits, including gravels and sands laid by streams, with substantial wind deposited silt and ash. Pumiceous and cindery at many locations, much of the area contains a shallow layer of poorly consolidated Mazama ash, radiocarbon dated 6600 years old. The area is shown on the 1991 Geologic Map of Oregon near the 2.0 meter contour for Mazama ash fallout, and public records of subsurface explorations nearby confirm the magnitude and uniformity of this deposit.

Shallow groundwater is common throughout the area. The Water Resources Department Well Log Database indicates static water levels in Section 30 range typically from 3 to 8 feet. The combination of shallow groundwater and cohesionless soils implies some risk of liquefaction in a seismically active area. The overall seismic risk is moderate.

3 FIELD EXPLORATIONS & TESTING

3.1 Subsurface Exploration & Testing

Subsurface conditions were explored by digging three test pits at the locations indicated on Figure 2. Backhoe excavations were made using a Bobcat BCT excavator with a 12-inch bucket. The test pit locations were sited by FEI to provide general profiles of subsurface conditions within areas of future development. Testing was performed in each test pit using a hand operated dynamic cone penetrometer as a means of evaluating the bearing capacity. Test pits were logged at the time of excavation by a FEI Geotechnical Engineer, and are included in Appendix A. A bulk sample of the surficial soil was taken from test pit TP-1 for laboratory analysis. Caving and heaving of test pits was severe, and prevented exploration to the planned depth.

July 5, 2012 2

Infiltration testing was performed at the approximate location shown on Figure 2 using the ”EPA Falling Head Method”. The test as implemented here consists of excavation of a 6 inch diameter by 12 inch deep test hole, placement of a plastic cylinder liner and gravel to prevent scour, and inverting a 5 gallon reservoir to maintain a nearly constant water level during the pre-soak period. Timed readings were taken following absorption of the pre-soak volume of the water drop relative to the top of the liner in 1.0 inch increments. The percolation testing rate was calculated to be 6 minutes per inch at a depth of 24 inches below the pavement.

3.2 Subsurface Conditions

The test pits indicate that the site is underlain by generally granular materials consisting of silty sands, volcanic ash and pumice, sands, and gravels. Near surface soils consist of

0.6 to 1.5 feet of silty sands grading to a young air-fall ash and pumice deposit. This unit is in a very loose to loose condition. Because reliable compaction testing is problematic in loose pumice deposits, Dynamic Cone Penetration (DCP) testing was performed as a means of estimating bearing capacity and settlement potential. Test results and soil types were fairly consistent within each test pit, and varied only slightly between test pits. The predominant soil type is a light yellow to gray, medium to coarse grained pumice, with a well compacted dry unit weight of about 50 pounds per cubic foot. DCP counts varied from 1 to 3 blows per increment. In this data range, DCP values are essentially numerically equal to the more common N-value of the Standard Penetration Test. Severe caving due to the cohesionless nature of the soil, and seepage pressure from groundwater occurred below a depth of about 5.5 feet. The bottom of the test pit heaved at about 6.5 feet, preventing further excavation.

Groundwater was encountered in each test pit at a depth of about 3.5 feet. Oxidation-reduction mottling was encountered at a depth of 2.0 feet below the surface. Well logs from Section 30 indicate that static well levels have ranged from about 3 to 5 feet in the vicinity of the site. Changes in drainage patterns, seasonality, well pumping, and landscaping all may affect future groundwater levels.

4 LABORATORY TESTING

Laboratory tests were performed on representative bulk samples to determine some of the physical and engineering properties of the subsurface soils. The results of the laboratory testing are presented in Appendix B, and include the following:

Particle Size Analysis (ASTM C117/C136 or AASHTO T-11/27) – Sieve analyses were performed on one selected soil sample to aid in classification and characterization of the engineering properties of the soil. The soil is type SP in the Unified Soil Classification System, and type A-1-b in the AASHTO classification system.

July 5, 2012 3

Moisture-Density Compaction Curve (ASTM D698 or AASHTO T-99) - One sample was selected for a compaction curve. This test uses a standardized method to compact soil into a mold at varying moisture contents. The resulting data curve identifies the optimum moisture and maximum density. The maximum density can then be compared to the field density of natural or fill soils to determine relative compaction. The relative compaction is useful for estimating shrinkage during grading, and estimating the settlement potential of soils.

5 CONCLUSIONS & RECOMMENDATIONS

Based on the results of our investigation, it is our opinion that the site soil and bedrock conditions are adequate for construction of the proposed structures and appurtenant features, providing the design and construction incorporates the recommendations found in this report.

Due to the existing low and variable relative compaction, and expected disturbance of near-surface soils during clearing and demolition, a nominal soil improvement scheme is warranted. We recommend that soils supporting building foundations be compacted to a depth corresponding to the footing load. Specific recommendations for recompaction are provided in section 5.4.

Conventional spread footing foundation systems are suitable for the support of structures at this site. Settlement of moderately loaded foundations bearing on properly compacted native soils or engineered fill should be less than 3/4-inch, with 1/2-inch potential dif-ferential settlement within a 30 foot span. Foundation design parameters, including allowable bearing capacity for recompacted soil are provided in section 5.2.

We recommend that fill placed within the future building areas consist of granular well-graded 3-inch minus material suitable for compaction testing. Over-size rock fragments used in engineered fill in landscape and pavement areas should be sized and placed in accordance with ODOT requirements as noted in their Standard Specifications, Section 00330.42(c-2-d). On-site soils may be stockpiled and used for structural fills and backfills subject to the compaction requirements in section 5.4. Fills, subgrade, and pad surfaces exposed to the elements can be degraded due to freeze-thaw and dessication cycles;

recompaction of surfaces should be expected when foundation construction or paving significantly lag initial grading.

Groundwater may be expected to encroach to within 2.0 feet of the existing ground surface on the basis of soil mottling. Accordingly, buried utilities, vaults, and other buried structures should consider buoyant forces in location and design. Vapor retarders are recommended in section 5.2 for slabs-on-grade.

A ground source heat pump may be installed for this project. In lieu of site specific or proprietary soil data, thermal conductivity and related properties may be estimated

July 5, 2012 4 from the design equations presented in the Foundation Engineering Handbook noted in the References section.

5.1 Seismic Design Parameters

Deterministic seismic parameters were developed from results of the on-site investigation and in accordance with Section 1613 of the 2010 OSSC. These parameters are as follows:

• Site Classification: D

• Maximum Considered Earthquake Spectral Response Acceleration Ss: 0.717

• Maximum Considered Earthquake Spectral Response Acceleration S1: 0.280

5.2 Foundation & Lateral Design Criteria

• Allowable bearing capacity for spread footings bearing on nominally compacted native soils as described in section 5.4 shall be 1000 psf for dead load plus live load. Footings located on over-excavated soils or engineered fill as described in section 5.4 may be designed for an allowable bearing capacity of 2000 psf for dead load plus live load. These values may be increased 1/3 for analysis of seismic and wind conditions.

• Continuous footings shall not be less than 12 inches wide. Isolated footing pads shall not be less than 18 inches square. It is recommended that all perimeter foundation elements be placed a minimum of 24 inches below lowest adjacent grade in order to be below frost penetration.

• Unrestrained retaining walls may be designed for on-site or similar imported soils using an equivalent fluid pressure of 30 pcf for level backfill, and 40 pcf for backfill sloping up to 2H:1V. Restrained retaining walls may be designed for on-site or similar imported soils using an equivalent fluid pressure of 45 pcf for level backfill.

A passive earth pressure of 400 psf/ft may be used for that portion of members which are embedded more than 12 inches below lowest adjacent grade or confined below a slab. A static coefficient for lateral sliding of 0.5 may be used for design.

The above values are unfactored; construction and service surcharges should be applied to these parameters. Positive piped drainage should be provided behind retaining walls. Final site topography should prevent water from ponding above or adjacent to the foundation. Degree of compaction of backfill shall be as for general fill.

• Interior slabs-on-grade should have a minimum of one No. 3 bar at 24 inches o.c.e.w. Slab reinforcement shall be placed at mid-depth of slabs. Slab subgrade

July 5, 2012 5 shall be compacted to a minimum of 92 percent of ASTM D1557 to a depth of 12 inches. A minimum 4-inch clean granular cushion shall be placed under all slabs to prevent capillary rise. The granular cushion shall be clean sand and gravel consisting of 1 inch minus with less than 5 percent passing the #200 sieve. In areas where moisture sensitive floor coverings are anticipated, it is recommended that the slab concrete mix contain moisture retarding admixture to reduce the moisture in the slab and minimize moisture condensation under floor coverings. Minimum slab thickness shall be four inches, actual. Significantly greater slab thickness and reinforcing may be required by the structural engineer or architect to meet loading requirements. A modulus of subgrade reaction k=180 pci may be used for design.

5.3 Pavement Design

• Based on the above data regarding site soils, and the anticipated vehicle loads, we recommend a minimum pavement section of 2.0 inches of Asphalt Concrete (AC) over 6 inches of crushed Aggregate Base (AB) in areas restricted to light trucks and automobiles. In areas such as through streets or delivery drives subject to regular truck or bus traffic we recommend a minimum pavement section of 3.0 inches of AC over 8.0 inches of AB. If Portland cement concrete (PCC) or composite heated pavement sections are used, a light vehicle section should consist of a minimum effective depth of 5.5-inches of PCC having a modulus of rupture of 600 psi.

• Aggregate Base should consist of 1-inch minus crushed aggregate conforming to applicable ODOT Standards. Subgrade should be compacted at least 12 inches deep to a minimum relative compaction of 90 percent of maximum density as determined by ASTM D1557. Aggregate Base should be compacted to a minimum of 95 percent of maximum density as determined by ASTM D1557.

5.4 Grading of Building and Pavement Areas

• Preparation of future building areas should consist of removal of all existing un-controlled fill, loose or disturbed soil, and deleterious materials within 5 feet of the building footprint, including exterior columns. Where lightly loaded (1000 psf) footings will be located at or near native soil elevations, excavations should be thoroughly moistened and compacted to a minimum depth of 12 inches below the footing base using suitable heavy dynamic compaction equipment, such as a large backhoe or excavator equipped with a hoe-pack. Where moderately loaded (2000 psf) footings are utilized, a minimum of 2.0 feet of engineered fill should exist below the footing base. The 2.0 feet of engineered fill thickness may be achieved through a process of over-excavation and filling below the native ground surface, or increased building pad elevation with engineered fill. Compaction testing should be performed to verify that sufficient depth and degree of compaction is achieved.

July 5, 2012 6

Placement of granular fill within footing areas should be in loose lifts of 9 inches or less, then thoroughly compacted. Degree of compaction shall not be less than 92 percent relative compaction as determined by ASTM D1557.

• In private street, sidewalk, or other paved areas, placement of fill should be pre-ceded by removal of loose materials, and compaction of the surface to a minimum of 90 percent relative compaction, or proof-rolled at near optimum moisture to verify a dense and non-yielding condition. Compaction depth of finished subgrade should equal the thickness of new fill or 12 inches, whichever is greater. Minimum relative compaction of the upper 12 inches of subgrade is 90 percent of maximum density as determined by ASTM D1557.

5.5 General Site Grading

• If old utility lines or water pipes are found within the construction area, they shall be properly abandoned or removed. All excavation caused from such removals, including such things as cistern or vault excavations, shall be backfilled and com-pacted. The degree compaction shall be as specified below for general fill.

• Remove all vegetation, organic material, and any deleterious debris, such as wood, roots, or demolition debris, from the construction area. The observed density of tree roots and organic matter in landscaped areas indicates that significant hand picking or screening of woody debris will be necessary from soil from these areas used as structural fill. Existing ground, including the bottom of over-excavation areas shall be scarified and compacted prior to placement of fill. Where moisture addition is required, scarification to a depth of 12 inches shall be accomplished by ripping at intervals no further apart than 18 inches in all areas requiring moisture conditioning. All scarified surfaces shall be compacted to a minimum relative compaction of 90 percent of maximum density as determined by ASTM D1557.

• Fill material shall be free of organic matter, debris, and any rocks or chunks over three inches in dimension, unless otherwise specified and approved by the Geotech-nical Engineer. Import soils shall not be composed of cinders or pumice, shall be granular in nature, and shall be approved by the Geotechnical Engineer prior to transporting to the site.

• All general fill shall be compacted to a minimum relative compaction of 90 percent of maximum density as determined by ASTM D1557. Fill material shall be placed at a moisture content which will allow adequate compaction. This is normally within three percent of optimum. Field density tests shall be made in conformance to ASTM D1556 or D2922.

• Compaction of fills shall be done with an adequate machine. On-site soils should be most readily compacted by heavy tracked, vibratory, or rubber-tired equipment.

July 5, 2012 7

• Backfill of utility trenches shall be done with approved on-site material or clean granular import fill in lifts, and thoroughly compacted to 90 percent of maximum density. Where backfill is placed within a previously filled area, e.g. a building pad, the backfill shall be compacted to at least the degree of compaction as the surrounding fill.

• Footing excavations and form areas shall be cleaned of all loose soils, clods and mud to expose firm undisturbed soils, or recompacted as needed. This shall be done as needed prior to placement of forms, reinforcement, or concrete.

• Excavation stability requires that temporary cuts for all soil and loose rock be sloped at not steeper than 1.5H:1V. Permanent slopes constructed of engineered fill or cut into native soil shall not be steeper than 2H:1V. Permanent cut and fill slopes greater than 5.0 feet in height should be evaluated for stability and specific drainage requirements by a geotechnical engineer or geologist.

5.6 Inspection and Testing

• All grading operations including demolition, excavation and fill placement, and foundation preparation shall be observed by the Geotechnical Engineer on a near continuous basis. The Contractor shall perform no grading operations until the Geotechnical Engineer has been notified. A pre-job meeting with the grading Contractor and Geotechnical Engineer should be conducted at the job site prior to the start of grading.

• All backfill and general fill shall be approved by the Geotechnical Engineer. Place-ment of all fill and backfill should be observed and tested for relative compaction by a qualified technician working under the direction of the Geotechnical Engineer.

A suitable testing frequency would be to test every one foot of fill depth as the material is placed, with each passing test representative of no more than 200 cu-bic yards of fill. The owner should notify the Geotechnical Engineer prior to the commencement of filling operations.

• All general excavations and footing excavations shall be inspected and approved by the Geotechnical Engineer or his representative prior to placement of any soil backfill or concrete.

5.7 Preliminary Stormwater Disposal

The site is generally suitable for dispersed shallow infiltration, although climatic con-siderations indicate that the design stormwater runoff volume may need to be stored for gradual absorption. Infiltration testing indicates soil absorption rates are fairly high below the existing compacted subgrade layer. Shallow groundwater will be a barrier to rapid and sustained infiltration, especially on a seasonal basis.

July 5, 2012 8

6 LIMITATIONS

Explorations performed for this study are intended to provide a reasonable picture of underground conditions for design purposes. Variations from the interpreted conditions, not indicated by our observations are possible. These variations are sometimes sufficient to necessitate modifications in the design. If unexpected conditions are observed during construction, or if the size, type, or location of the structures should change, we should be notified to review our recommendations. The professional judgments expressed in this report meet the current standard of care of our profession.

Our services did not include evaluation of regulated materials, hazardous wastes, hydro-logical phenomena, or environmental conditions which may be pertinent to development or use of the site. FEI Testing & Inspection, Inc. has performed its services in accor-dance with generally accepted engineering and consulting standards in effect at the time services were performed. No other warranty is offered, expressed or implied.

7 REFERENCES

Foundation Engineering Handbook, 2nd Edition, H-S, Fang, Van Nostrand Reinhold, 1991.

Geologic Map of Oregon, by G.W. Walker and N.S. Macleod, 1991.

Geology and Mineral Resources of Deschutes County, Oregon by N.V. Peterson and others, Oregon Department of Geology and Mineral Industries Bulletin 89, 1976.

Oregon State Water Resources Department, http://apps2.wrd.state.or.us/apps/gw/well_log/Default.aspx

Oregon Structural Specialty Code, International Conference of Building Officials, 2010.

Standard Specifications for Highway Construction, Oregon Department of Transporta-tion, 1996.

July 5, 2012 9

GEOLOGIC VICINITY MAP

USFS District Office Building

136471 Hwy 97 Crescent, Oregon

Date: July 2012 Figure: 1

Scale: 1:500000

Project No. : 2129055-900

SITE MAP

USFS District Office Building

136471 Hwy 97 Crescent, Oregon

Date: July 2012 Figure: 2

Scale: N/A

Project No. : 2129055-900

APPENDIX A

Test Pit Logs

July 5, 2012 A

-2

8-c:

\m te ch

\u sf sc do

\tp 1.

bo r

Log of Trench TP-1 (Page 1 of 1)

Geotechnical Investigation Steele Architects

USFS-Crescent District Office

Crescent Oregon

Project No: 2129055

Excavation Date : June 26, 2012

Contractor : Latham

Equipment : BCT w/ 1' bucket

Surface : Paved, 2'' AC

Logged By : W.A. Smith

Feet

U S

C S

SM

SP

SILTY SAND, with gravel, brown-gray, moist, dense, fill and compacted subgrade.

GRAVELLY SAND, fine-coarse, yellow-gray, moist to saturated below 3.5', medium dense.

Severe caving and heave.

End of trench, groundwater at 3.5', mottling at 2.0'.

Dynamic Cone (bpi)

3/3/3

2/2/2

8-c:

\m te ch

\u sf sc do

\tp 2.

bo r

Log of Trench TP-2 (Page 1 of 1)

Geotechnical Investigation Steele Architects

USFS-Crescent District Office

Crescent Oregon

Project No: 2129055

Excavation Date : June 26, 2012

Contractor : Latham

Equipment : BCT w/ 1' bucket

Surface : Planter/path

Logged By : W.A. Smith

Feet

U S

C S

SM

SP

SILTY SAND, with gravel, brown-gray, moist, medium dense, fill or cultivated.

GRAVELLY SAND, fine-coarse, yellow-gray, moist to saturated below 3.5', medium dense. Particles a bit rounded, uniform, equigranular zones.

Severe caving and heave.

End of trench, groundwater at 3.5', mottling at 2.0'.

Dynamic Cone (bpi)

3/3/3

2/2/1

8-c:

\m te ch

\u sf sc do

\tp 3.

bo r

Log of Trench TP-3 (Page 1 of 1)

Geotechnical Investigation Steele Architects

USFS-Crescent District Office

Crescent Oregon

Project No: 2129055

Excavation Date : June 26, 2012

Contractor : Latham

Equipment : BCT w/ 1' bucket

Surface : Lawn

Logged By : W.A. Smith

Feet

U S

C S

SM

SP

SILTY SAND, with gravel, brown-gray, moist, medium dense, fill or cultivated.

GRAVELLY SAND, fine-coarse, yellow-gray, moist to saturated below 3.5', medium dense.

Severe caving and heave.

End of trench, groundwater at 3.5', mottling at 2.0'.

Dynamic Cone (bpi)

3/3/3

2/2/1

APPENDIX B

Laboratory Test Results

July 5, 2012 B

B-1

% < No.200 =

Plasticity Index =Liquid Limit = Sp.G. =Nat. Moist. =

AASHTO:USCS:Classifications -

Description:

MATERIAL DESCRIPTION

Remarks:

Date:Project No.:

COMPACTION TEST REPORT

FEI Testing & Inspection, Inc.

TEST RESULTS

% > No.4 = 9.0 %

Location: Crescent Oregon

Optimum moisture = 74.1 %

Maximum dry density = 50.1 pcf

3.9 %

NP

66. %

A-1-bSP

Yellow gray gravelly sand, fine coarse, volcanic ash and pumice

6-27-122129055

D ry d en si ty

, p cf

Water content, %

100% SATURATION CURVES

FOR SPEC. GRAV. EQUAL TO:

2.8 2.7 2.6

Test specification:

AASHTO T 99 Method A Standard

50 55 60 65 70 75 80 85 90

Project: USFS Crescent, Oregon

Figure B-2