Addendum1_Attachment1_Geotech Report YWTP.pdf

March 16, 2009

Young Women’s Transition Facility Geotechnical Investigation Oak Creek Youth Correctional Facility Project No. 006-09-01 Albany, Oregon

Geotechnical Investigation Oak Creek Youth Correctional Facility

Young Women’s Transition Facility 4400 Lochner Road SE

PROJECT INFORMATION

We understand that the Oregon Youth Authority plans to construct a new Young Women’s Transition Facility at their existing Oak Creek Youth Correctional Facility located at 4400 Lochner Road SE in Albany, Oregon. The site location is shown on the Vicinity Map (Figure 1) included in Appendix A. The new development will include a single story residential housing building located immediately to the east of the existing facility. The proposed improvements will also include some access pavements, parking areas and landscaping. The proposed new building layout is shown on the Site Plan (Figure 2, Appendix A).

The proposed building will be ±9,000 SF in plan area, wood framed with a slab on grade floor. Foundation loads for the structure are expected to be relatively light.

We anticipate that site grading will be limited to minor cuts and fills of less than ±4 feet across the relatively flat site. Utility construction may require trenches to depths of ±4 to 8 feet below grade.

FIELD EXPLORATION

The field exploration focused on characterization of the upper soils at the site that will be involved in the proposed foundation excavations and site grading of the parking areas. We visited the site on February 27, 2009 to observe surface conditions and conducted limited subsurface explorations. During our visit we conducted a brief surface reconnaissance of the proposed development area. Subsurface conditions were investigated by digging test pits using a small track mounted excavator at three locations across the parcel. The approximate locations of the test pits are shown on the attached Site Plan (Figure 2, Appendix A). The test pits were excavated to maximum depths of ±8.5 feet. The soil profiles in each test pit were logged and representative samples were collected from some locations. The soil profiles are summarized on the narrative test pit logs attached in Appendix B. Our surface and subsurface observations are summarized in the following sections.

Young Women’s Transition Facility Geotechnical Investigation Oak Creek Youth Correctional Facility Project No. 006-09-01 Albany, Oregon

SITE CONDITIONS

Surface Conditions:

The site includes relatively level terrain over the proposed development area. At the time of our investigation the east portion of the site was predominately grass covered. A gravel surfaced area is present over the western portion of the building pad. There is also a narrow access road that extends to the east across the site that includes some gravel surfacing. An area of oak trees and blackberry bushes is present to the south of the proposed building area. The site slopes slightly to the south with a shallow swale present in the area of the oak trees.

Subsurface Conditions:

The site is located to the north of Oak Creek and includes alluvial soils. Subsurface conditions were evaluated using test pit explorations across the proposed development area.

Ground water was encountered in the test pits at relatively shallow depth. Minor seepage was noted as shallow as ±2 feet. More moderate seepage was noted at some locations. The higher infiltration rates were typically associated with roots or animal burrowing that was encountering in the test pit side walls. Based on the observed clay, we anticipate that surface water perches in the upper several feet of the soil profile during winter months. Due to the proximity of the site to Oak Creek, we also expect that ground water levels are relatively shallow throughout the year.

Subsurface conditions observed at the site as part of our field exploration typically included the following strata:

Fill.

The western portion of the building area includes granular fill that has previously been placed on the site. Test pit TP-3 was excavated in the area of the existing granular fill and encountered a thin layer of ¾-inch minus crushed rock overlying angular, ±6-inch minus quarry rock. The granular fill is ±12 inches thick at the test pit location.

Topsoil.

The upper ±0.5 to 0.8 feet of the soil profile includes soft organic clay with variable silt and sand. The organics typically consist of fine roots. The clay is moist with high plasticity.

Clay Alluvium.

The upper topsoil transitions to clay alluvium. The clay is typically medium stiff grading to stiff and contains some silt and fine sand. The sand content typically increases with depth. The clay is grey to brown, moist to wet and

Young Women’s Transition Facility Geotechnical Investigation Oak Creek Youth Correctional Facility Project No. 006-09-01 Albany, Oregon medium to high plasticity. The clay extends to the limits of our exploration at the site (±8.5 feet below existing grades).

SEISMIC DESIGN

The average soil conditions in the upper ±100 feet beneath the proposed development area are expected to include predominately alluvial soils consisting of stiff silt and clay. Therefore, we believe that use of a site class D is appropriate for seismic design. In our opinion, the spectral accelerations and attenuation relationships provided in the 2007 OSSC are appropriate for seismic design of the new structure. We recommend using the General Procedure of OSSC, Section 1613 to develop parameters for seismic design of the structure.

Peak ground accelerations and spectral accelerations (on rock) were determined for design using 2% probability of exceedence in 50 years (i.e., ±2,475 year return interval). The ground motions provided in OSSC are based on the 1996 USGS mapping, however, the USGS updated the maps in 2002 to reflect improved modeling of the Cascadia Subduction Zone earthquake. We have used the 2002 USGS modeling as the most current and accurate information for the site. This modeling considers a variety of seismic sources including crustal and subduction zone earthquakes. However, the principal source of the design ground motion is due to a large magnitude (Mw 8.3 to 9.0) earthquake along the Cascadia Subduction Zone ±40 miles west of the site. Crustal earthquakes were also considered, but do not contribute significantly to the design ground motion. The peak ground acceleration (PGA) on rock for the site is 0.31g with a short period spectral acceleration (Ss) of 0.73g at 0.2 second period and long period spectral acceleration (S1) of 0.34g at 1.0 second period. The parameters for establishing the General Procedure Response Spectrum using OSSC Section 1613 are summarized in Table.

1. The values for SDS and SD1 include a two-thirds reduction as discussed in Section 1613.5.4.

Table 1. OSSC 2007 Seismic Design Parameters

Site Class Ss S1 Fa Fv SMS SM1 SDS SD1

D 0.73 0.34 1.22 1.72 0.89 0.59 0.59 0.39

DISCUSION OF GEOTECHNICAL ISSUES

Building Pad:

We understand that initial site grading will include constructing the building pad to El.

231 to prepare the site for the future structure. The prepared building pad will accommodate a finished floor elevation of 231.5 for the new structure. The west portion of the building pad includes existing granular fill, which may be utilized for the

Young Women’s Transition Facility Geotechnical Investigation Oak Creek Youth Correctional Facility Project No. 006-09-01 Albany, Oregon currently proposed work. The stability of the existing granular fill will need to be evaluated at the time of building pad preparation to identify areas of soft or unsuitable subgrade that will require excavation and replacement. Approved portions of the existing granular fill could be prepared by simply adding aggregate base to the required elevation.

The eastern portion of the building pad will require stripping the soft topsoil and constructing a granular building pad. We anticipate that removal of the soft upper soils will require excavation depths of ±9 to 12 inches below existing grades. Final excavation of the building pad subgrade should be conducted with care using an excavator equipped with a smooth bucket to minimize soil disturbance. The moisture of the exposed subgrade should be maintained throughout the work. Due to the work being conducted during spring months, we recommend that a separation geotextile and initial lift of ±3-inch minus, angular quarry rock be placed over the undisturbed subgrade. Placement of the initial lift of fill will require care and use of only light construction equipment to minimize the risk of pumping or softening of the subgrade soils. The lower quarry rock should be capped with a minimum of 12 inches of compacted aggregate base. A schematic of the building pad section is provided on Figure 3, Appendix A.

We have assumed that the final grading and slab preparation will also include placement of a vapor barrier beneath the slab that is compatible with the planned floor coverings and method of slab curing.

Foundations:

The proposed structures will be supported by shallow foundations constructed over medium to high plastic clay. Due to the plasticity of the foundation soils and associated risk of seasonal shrink/swell movements, we recommend that the base of all perimeter footings be embedded a minimum of 2 feet below finished grades. A leveling course of ±6 inches of compacted crushed rock should be used beneath the perimeter foundations during dry weather to help minimize disturbance of the underlying clay during foundation construction and maintain the moisture of the foundation soils. The thickness of the rock beneath the footings should be increased to 12 inches during wet weather conditions.

Drainage:

The site is relatively flat and the upper clay is expected to have a relatively low permeability. Surface water is expected to perch on the upper clay at the site.

Therefore, we have assumed saturated conditions for our bearing capacity analysis and believe that it will be necessary to raise the building pad above current site grades. We recommend that the finished grading surrounding the structure be sloped to promote surface drainage away from the foundations. Foundation drains should be included around the structure to help control water adjacent to the new building.

Young Women’s Transition Facility Geotechnical Investigation Oak Creek Youth Correctional Facility Project No. 006-09-01 Albany, Oregon

We understand that the improvements may also require construction of a storm water detention basin or pond. Due to the plasticity of the clay and proximity to Oak Creek, we do not anticipate that significant water infiltration will occur in the native soils during winter storm events. In addition, excavations below ±2 feet are likely to intercept water that perches on the stiffer clay soils underlying the topsoil stratum.

Weather Conditions:

We understand that the initial site work, including preparation of the building pad will be conducted in the upcoming spring months. We recommend that site work for other elements, such as pavement and parking areas be delayed until summer months when the subgrade soils can be processed and better accommodate the required construction traffic.

The upper soil present at the site is moisture sensitive and will be susceptible to softening and pumping during wet weather conditions. In addition, water will tend to perch on the upper clay soils during winter months; therefore, dewatering/drainage is expected to be a concern for wet weather work. The upper clay is highly plastic and expected to have moderate shrink/swell potential. Careful control of subgrade moisture contents throughout the work will be required regardless of weather conditions at the site.

Site grading conducted during wet weather conditions is expected to require use of a thickened granular fill surface to support even light construction equipment. Use of on-site materials will not be viable during wet weather conditions. Therefore, all excavated topsoil and clay should be either hauled from the site or stockpiled outside the proposed development area for use in finished grading of landscape areas around the new structure.

GEOTECHNICAL ANALYSIS

OGD has conducted geotechnical analysis of the foundation soils for design of the new foundations. Our work is briefly summarized below.

Bearing Capacity:

We conducted bearing capacity analysis for the anticipated foundation loads for the new structure. Foundation loads were not available at the time of this report. We have assumed that the loads for the structure may be as great as 2 kips/linear foot for continuous footings and as great as 20 kips for spread footings.

Lightly loaded footings may be constructed over the upper medium stiff clay alluvium using an allowable bearing pressure of 2,000 psf. All continuous footings should have a minimum width of 16 inches. Isolated spread footing foundations should have a minimum dimension of 24 inches. Our analysis assumed that the perimeter footings would be underlain by a nominal ±6 inches of compacted crushed rock that extends a minimum of 6 inches beyond the limits of the footing. The base of all

Young Women’s Transition Facility Geotechnical Investigation Oak Creek Youth Correctional Facility Project No. 006-09-01 Albany, Oregon perimeter footings should be embedded a minimum of 24 inches below finished grades.

The footings should be designed using an ultimate subgrade friction coefficient of

0.5 for foundations constructed on compacted crushed rock. A factor of safety of 1.5 is appropriate for this coefficient to minimize relative movements when considering long- term loads.

Soil parameters used in the bearing capacity evaluation were also used to estimate the modulus of subgrade reaction beneath the proposed slab. Our calculations suggest that slab design using a ks value of 100 kips/ft3 is appropriate for the site assuming a minimum aggregate base thickness of 18 inches over the medium stiff subgrade soils.

Settlement:

Considering the anticipated foundation loads and stiffness of the underlying clay, we do not believe that settlement will be a significant issue. However, variations in the consistency and depth of the alluvium underlying the foundations could result in some minor differential settlement. Therefore, total and differential settlements of ±0.5 inch should be assumed. Minor seasonal shrink/swell is likely to occur due to seasonal moisture variations in the plastic clay soils.

Pavements:

We have conducted pavement thickness analysis using assumed traffic, based on our experience with similar facilities. Our traffic evaluation assumes that the paved areas will be limited to car traffic with occasional light truck traffic. The assumed traffic includes a daily volume of 100 cars and pickups and 2 light two-axle delivery trucks (28k gross vehicle weight). The traffic applied over a 20 year design life results in an Equivalent Single Axle Loading (ESAL’s) of ±18,000. A Mr value of 3,000 psi was selected for our analysis based on available correlations and our experience with similar clay subgrade soils. We assumed a 20 year design life for our analysis, a reliability of 90% and terminal serviceability of 2.0. Our calculations suggest that a pavement section consisting of 3.5 inches of asphalt over 12 inches of aggregate base should be used over the approved subgrade.

Table 2. Pavement Analysis Summary

Traffic ESAL’s Asphalt

Thickness (inches)

Aggregate Base Thickness (inches)

Car Traffic 18,000 3.5 12

Young Women’s Transition Facility Geotechnical Investigation Oak Creek Youth Correctional Facility Project No. 006-09-01 Albany, Oregon

RECOMMENDATIONS

Based on our observations of the soils and our understanding of the proposed development OGD believes that it will be practical to construct the improvements using conventional construction techniques.

Materials:

1. Aggregate base as defined in this report should consist of ¾ or 1-inch minus, well graded crushed rock. The rock should be relatively clean with less than 5% (by weight) passing the #200 sieve.

2. Granular fill, as defined in this report, should consist of ±2 to 3 inch minus, clean, well-graded, angular rock than contains less than 2% (by weight) passing the #200 sieve.

3. Topsoil is expected to include the upper ±9 to 12 inches of the soil over the site. The topsoil is soft and contains unsuitable materials including fine organics. Therefore, these materials should be either placed in landscape areas or hauled from the site.

4. Compact all aggregate base and granular fill to 95% relative compaction. The maximum dry density of ASTM D 698 should be used as the standard for evaluation of relative compaction. Field density testing should be conducted on the compacted aggregate base fill to document proper compaction at regular intervals throughout the work.

5. Subgrade beneath pavements and building pads should be evaluated and approved by the engineer prior to placement of aggregate base. Proof rolling of the pavement subgrade using a partially loaded dump truck may be used to assist in the evaluation. The clay subgrade beneath the building pad should not be proof rolled during spring months (wet weather).

Utilities:

6. Provide shoring for all trench excavations greater than 4 feet below grade.

Anticipate that minor caving of trench sidewalls may occur, even in shallow excavations.

7. Dewatering of trenches may be required, particularly during winter and spring months. Use of slightly deeper excavation and stabilization of the bottom of the trenches may also be required in wet conditions.

Foundation Design:

8. Design all lightly loaded foundations (continuous wall footings and isolated column footings) using a maximum allowable bearing capacity of 2,000 psf.

Young Women’s Transition Facility Geotechnical Investigation Oak Creek Youth Correctional Facility Project No. 006-09-01 Albany, Oregon

This evaluation assumes that footing preparation and placement of compacted aggregate base will be conducted as recommended.

9. Provide a minimum footing width of 16 inches for continuous perimeter footings and 24 inches for isolated column footings. Place the base of all footings at least 24 inches below the finished grade or paved surfaces.

10. Provide a minimum of 6 inches of compacted aggregate base beneath the footings that extends laterally 6 inches beyond the footing limits during dry weather. The aggregate base thickness should be increased to 12 inches during wet weather.

Site Preparation- Building Pad:

Recommendations for building site preparation conducted in the upcoming spring months are provided below.

11. Preparation of the building pad should extend ±3 to 5 feet beyond the proposed building limits.

12. Evaluate the existing granular fill within the proposed building pad by proof rolling the surface using a loaded ±12 cubic yard dump truck. Areas of the granular fill that rut, pump or deflect excessively (greater than ±½ inch) should be delineated and treated similar to the soil surfaced portions of the building pad.

13. Following the proof roll do not allow construction traffic over the existing granular fill within the building pad area unless the surface is over built with an additional ±1 foot of aggregate base.

14. Strip the soil surfaced portion of the proposed building pad of the existing soft topsoil to a depth of ±9 to 12 inches, or as necessary to remove all soft and organic soils. Excavate the building pad location to allow placement of a minimum of 18 inches of granular fill (i.e., El. 228.5).

15. Do not compact the subgrade. Minimize disturbance to the subgrade by completing the excavation using an excavator equipped with a smooth bucket. Maintain the subgrade moisture throughout the work.

16. The excavated subgrade should be observed and approved immediately prior to placement of granular fill. Any areas of soft or unsuitable subgrade should be excavated to expose firm subgrade.

17. Cover the approved subgrade with a separation geotextile and the initial lift of granular fill. Place and spread the granular fill with a dozer or other suitable piece of light, low ground pressure construction equipment and compact using a vibratory roller.

18. Place and compact ±12 inches of aggregate base over the granular fill to support the building slab. Compact the aggregate base to 95% relative

Young Women’s Transition Facility Geotechnical Investigation Oak Creek Youth Correctional Facility Project No. 006-09-01 Albany, Oregon compaction according to ASTM D 698. Field density testing should be conducted to confirm adequate compaction.

Foundation/Slab Construction:

19. Foundation excavations extending through the aggregate base fill should be extended to allow placement and compaction of the required thickness of aggregate base beneath the footings. All foundation excavations should be conducted using an excavator equipped with a smooth bucket to minimize disturbance to the foundation soils.

20. Place and compact a minimum of 6 inches of aggregate base beneath all foundations.

21. Construct a perimeter foundation drain around the new structure that includes a perforated 3 or 4 inch diameter drain pipe with the flow line near the base of footing level. The foundation drain should be bedded in drain rock and include at least 12 inches of drain rock cover over the pipe. The entire mass of drain rock should be wrapped in a drainage geotextile.

22. After completion of all pluming and electrical trenching in the building pad the aggregate base should be finish graded and compacted.

23. Install the vapor barrier beneath the slab per the manufacturer’s recommendations.

Site Preparation- Access Pavements and Parking Areas:

Recommendations for site preparation of pavement areas conducted in the summer months are provided below.

24. Pavements should be constructed during dry weather to the extent practical.

The pavement sections recommended herein are not intended to support construction traffic. Therefore, the aggregate base thickness should be increased to a minimum of 24 inches in all areas that will support construction traffic or staging during wet weather.

25. Subgrade preparation of the upper soils is expected to require moisture conditioning and compaction of the upper ±16 inches of the subgrade. The moisture content of the prepared subgrade should be maintained throughout the work.

26. The compacted subgrade should be evaluated to identify any areas of fill, soft soils or unsuitable material. Conduct moisture density testing and proof-rolling of the compacted subgrade. Any areas of soft soil, rutting or pumping should be identified and stabilized prior to placement of aggregate base.

27. Place and compact the required aggregate base section over the approved subgrade as soon as practical. We anticipate that the base section will support limited construction traffic during dry weather conditions. Field

Young Women’s Transition Facility Geotechnical Investigation Oak Creek Youth Correctional Facility Project No. 006-09-01 Albany, Oregon density testing should be conducted on the compacted aggregate base to confirm adequate compaction.

28. Provide a flexible pavement section consisting of 3.5 inches of asphalt over 12 inches of aggregate base in the new parking areas.

29. Compact the asphalt cement pavement to a minimum of 91% relative compaction according to the theoretical maximum density calculated from the Rice specific gravity. Conduct density testing on the asphalt pavement at the time of compaction to confirm the required density is being achieved.

LIMITATIONS OF THIS REPORT

The analysis, conclusions and recommendations contained herein are based on the assumption that the soil conditions including ground water levels encountered in the test pits are representative of overall site conditions. The above recommendations assume that we will be present during construction to confirm the assumed foundation and subgrade conditions. We will assume no responsibility or liability for any engineering judgment, inspection or testing performed by others.

Our work was performed for the exclusive use by Beaman Architecture Ltd. and their design consultants for the new Young Women’s Transition Facility at the existing Oak Creek Youth Correction Facility on Lochner Road SE in Albany, Oregon. OGD performed our work in accordance with generally accepted professional geotechnical engineering practices in similar locations. Our services do not include any survey or assessment of potential contamination or contamination of the soil or ground water by hazardous or toxic substances. No other warranty, expressed or implied, is made.

Young Women’s Transition Facility

Appendix A

Figures

OGD Consulting, PC Serving Oregon Geotechnical Design and Consulting Needs

Young Women’s Transition Facility

Appendix B

Test Pit Summary Logs

OGD Consulting, PC Serving Oregon Geotechnical Design and Consulting Needs

Oak Creek Young Women’s Transitional Facility Geotechnical Investigation – Appendix B 4400 Lochner Road SE Project No. 006-09-01 Albany, Oregon

Geotechnical Investigation Oak Creek Youth Correctional Facility

Young Women’s Transition Facility

APPENDIX B

NARRATIVE TEST PIT SUMMARIES

Logged on February 27, 2009

Test Pit: TP-1

Depth (feet) Material Description Notes/Sampling

0 to 0.8 Soft organic CLAY with some silt; dark grey, moist, high plasticity, fine roots throughout, (topsoil).

0.8 to 2.3 Soft to medium stiff silty CLAY with scattered fine roots; grey with some brown mottling, moist to wet, high plasticity, (alluvium).

Tv = 0.4 tsf @ 1.5’ S-1-1 @ 1.5’ – 2’

2.3 to 8.5 Stiff silty CLAY with trace sand; brown, wet, medium to high plasticity, fine sand, (alluvium). Grades to sandy CLAY with some silt.

Moderate ground water infiltration below ±3 feet.

Test Pit: TP-2

0 to 0.5 Soft organic CLAY with some silt and sand; dark brown, moist, medium plasticity, fine organics, (topsoil).

0.5 to 1.9 Medium stiff CLAY with some silt and trace sand; dark grey, slightly moist, medium to high plasticity, (alluvium).

S-2-1 @ 1’ – 1.5’ Tv = 0.38 tsf @ 1.4’

1.9 to 8.0 Medium stiff to stiff CLAY with some sand; brown, wet, blocky structure, (alluvium).

Grades to sandy CLAY with fine sand and slightly moist to moist with depth.

Tv = 0.46 tsf @ 2.0’ Tv = 0.55 tsf @ 2.5’ S-2-2 @ 2.5’ – 3’ Minor caving of test pit side walls.

Minor seepage below ±2 feet, becomes moderate below ±3.5 feet.

Oak Creek Young Women’s Transitional Facility Geotechnical Investigation – Appendix B 4400 Lochner Road SE Project No. 006-09-01

Test Pit: TP-3

0 to 1.0 Dense sandy GRAVEL and COBBLES;

grey and brown, moist, ±¾-inch minus gravel overlying ±6-inch minus angular quarry rock, (FILL).

1.0 to 2.5 Medium stiff silty CLAY with trace organics; dark grey, moist, high plasticity, (alluvium).

2.5 to 8.0 Medium stiff silty CLAY with some sand grading to sandy CLAY; brown, wet, medium to high plasticity, fine sand, (alluvium)

Minor seepage below ±3 feet. Zone of heavier ground water infiltration at ±3.5 feet.