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Geotechnical Investigation and Seismic Hazard Study

Albany Police Station Albany, Oregon Prepared for: City of Albany Albany, Oregon July 15, 2015

Foundation Engineering, Inc.

Professional Geotechnical Services

Albany Police Station July 15, 2015 Geotechnical Investigation and Seismic Hazard Study 1. Project 2151053 Albany, Oregon City of Albany

GEOTECHNICAL INVESTIGATION AND SEISMIC HAZARD STUDY

ALBANY POLICE STATION ALBANY, OREGON

BACKGROUND

The City of Albany (City) plans to construct a new police station in Albany, Oregon. The proposed site is a currently undeveloped, rectangular, ±3.7-acre parcel located in the 2400 block of SW Pacific Boulevard. A conceptual site plan provided by the City indicates the new building will be ±100x150 feet in plan (i.e., a ±15,000 SF footprint). The building will be surrounded by paved parking areas.

The City is the project owner and Mackenzie is the structural consultant. Foundation Engineering was retained by the City as the geotechnical consultant. Our scope of work was outlined in a proposal dated June 4, 2015, and authorized by a purchase order dated June 5, 2015.

LOCAL GEOLOGY

An abbreviated discussion of local geology is provided below. Detailed discussions of the regional geology, tectonic setting, local faulting and historical seismicity are presented in the Seismic Hazard Study (Appendix C). References cited in this section are found in Appendix C.

The site is located in Albany, ±¾ mile east of the Calapooia River and ±1½ miles south of the Willamette River. Local geologic mapping indicates the flat site is underlain by alluvial deposits including Willamette Silt followed by fluvial deposits of clay, silt, sand and gravel from the Willamette River and associated local tributaries (Wiley, 2006; Yeats et al., 1996). It is estimated up to ±300 feet of sand and gravel have been deposited by the Willamette River in the vicinity of downtown Albany, ±1¼ miles north (Orr and Orr, 1999). The fluvial deposits also contain clay overbank deposits at the river edges. In localized areas, the overbank deposits can extend to ±150 feet deep. Therefore, we do not anticipate bedrock in the upper ±100 feet of the subsurface profile at the project site.

The subsurface conditions encountered in our explorations are consistent with the mapped local geology. Details are provided in the Subsurface Conditions section of this report.

FIELD EXPLORATION

We dug eight exploratory test pits (TP-1 through TP-8) at the site on June 29, 2015, using a tracked excavator. Four test pits were located at the approximate corners of the proposed building footprint. The other four test pits were located within the pavement areas across the site. The approximate test pit locations are shown on Figure 2A (Appendix A).


The test pits extended to depths of ±4 to 9 feet. Disturbed soil samples were obtained for possible laboratory testing. Undrained shear strength measurements were made on the test pit side walls using a Field vane shear device. Upon completion of the excavation work, the test pits were backfilled with the excavated materials and compacted in lifts by tamping with the bucket of the excavator. The soil profile, sampling depths and strength measurements are summarized on the test pit logs (Appendix B).

We drilled one borehole (BH-1) at the site on June 30, 2015. The borehole was located near the center of the proposed building footprint (see Figure 2A (Appendix A)). The borehole was drilled using a CME 55, truck-mounted drill rig with mud-rotary and hollow-stem auger drilling techniques. The borehole extended to a maximum depth of ±51.5 feet. Samples were obtained at 2.5-foot intervals to a depth of ±20 feet and at 5-foot intervals thereafter. Disturbed samples were obtained with a split-spoon sampler. The Standard Penetration Test (SPT), which is run when the split-spoon is driven, provides an indication of the relative stiffness or density of the foundation soils.

The borehole was continually logged during drilling. The final log (Appendix B) was prepared based on a review of the field log and an examination of the soil samples in our laboratory. Ground surface elevations shown on the test pit logs and borehole log were estimated using a topographic site plan prepared by K&D Engineering, Inc. (KDE) and should be considered approximate only. The subsurface conditions are discussed below.

DISCUSSION OF SITE CONDITIONS

Site Topography and Vegetation

The site is relatively flat and is covered by grass. The topographic site plan prepared by KDE indicates the ground surface elevation ranges from ±El. 214 to ±El. 215.

Subsurface Conditions

A brief discussion of the soil types encountered in the test pits is provided below. A detailed summary of the conditions encountered in each test pit are provided in the appended logs.

Topsoil. Topsoil was encountered in all of the explorations to a depth of ±10 to 12 inches. This unit consists of brown, stiff, low to medium plasticity silty clay with scattered organics. Organics consisted of fine roots.

Clay (alluvium). The topsoil is underlain by grey and iron-stained, very stiff high plasticity clay. Trace sand or gravel was encountered in several of the test pits. The clay extends to depths of ±1.7 to 2.9 feet. Field Vane shear tests completed on the sidewalls of the test pits in this stratum indicate the soil has an undrained shear strength of greater than 1 ton/ft2 (tsf).


Silt (alluvium). Brown, very stiff, low plasticity silt was encountered below the clay. The silt extends to ±4 to 9 feet in the test pits (the limits of the exploration), and to ±9.5 feet in BH-1. Field Vane shear tests completed on the test pit sidewalls in this stratum indicate the soil has an undrained shear strength of greater than 1 tsf. A thin lens of silty, sandy gravel (±4 to 21 inches thick) was encountered at depths of ±2.6 to 3.7 feet within this unit in most of the explorations.

Clayey Gravel (alluvium). Grey clayey gravel with some sand extends below the silt to ±15 feet in BH-1. SPT N-values of 18 and 28 were recorded in the gravel, suggesting a medium dense consistency.

Sandy Gravel (alluvium). Grey, sandy gravel with trace silt was encountered below the clayey gravel in BH-1. SPT N-values ranging from of 51 and 75 were recorded in the gravel, suggesting a very dense consistency. Drilling action suggested the sandy gravel extends to a depth of ±29 feet.

Silt (alluvium). Grey, low to medium plasticity silt extends below the gravel to ±45 feet in BH-1. SPT N-values ranging from of 31 to 38 were recorded in the silt, suggesting a hard consistency.

Silty Sand (alluvium). Dark grey silty sand extends below the silt to ±50 feet. An SPT N-value of 40 was recorded in the silty sand, suggesting a dense consistency.

Clay (alluvium). The silty sand is underlain by grey, high plasticity clay to ±51.5 feet, the limit of the exploration. An SPT N-value of 19 was recorded in the clay, suggesting a very stiff consistency.

Ground Water

We observed no ground water infiltration in any of the exploratory test pits to a depth of ±9 feet. We were unable to measure the water level in the boring during drilling because mud-rotary drilling methods were used.

Well logs within the project vicinity indicate static ground water depths ranging from ±9 to 20 feet. Because the site is relatively flat and is underlain by a layer of high plasticity clay, we anticipate a shallow perched water condition will also develop near the ground surface during periods of extended rainfall.

LABORATORY TESTING

The laboratory work included natural water content and Atterberg limits tests to classify the foundation soils, determine their homogeneity and estimate their overall engineering properties. Results of these tests are summarized in Table 1.


Table 1. Natural Water Content and Atterberg Limits

Sample Number

Sample Depth (feet)

Natural Water Content (percent)

LL

PL

PI

USCS Classification

S-1-1 1.0 – 2.0 16.3

S-1-2 2.2 – 2.9 26.9

S-2-1 1.5 – 2.5 28.1

S-4-1 1.0 – 2.0 25.3

S-5-1 1.0 – 1.5 27.6 78 28 50 CH

S-5-2 2.5 – 3.5 32.7 43 32 11 ML

S-6-1 1.0 – 1.5 24.9

S-6-2 2.0 – 3.0 31.9

S-8-2 2.6 – 3.1 23.3

SEISMIC DESIGN

Bedrock Acceleration and Site Response

The site is underlain by predominantly stiff, fine-grained soils and medium dense to very dense, coarse-grained soils. Based on these conditions, a 2014 Oregon Structural Specialty Code (OSSC) Site Class D (stiff soil) is recommended for seismic design.

The 2014 OSSC is based on the 2012 International Building Code (IBC). The design maximum considered earthquake ground motion maps provided in the 2014 OSSC are modified 2008 USGS maps with a 1% probability of exceedance in 50 years (i.e., a ±4,975-year return period). The modifications include factors to adjust the spectral accelerations to account for directivity and risk. The IBC 2012/OSSC 2014 site response spectrum and seismic design parameters are summarized on Figure 3A (Appendix A).

Liquefaction

Liquefiable soils typically consist of saturated, loose sand and non-plastic silt. These soils were not encountered in the explorations. Therefore, it is our opinion there is no liquefaction hazard at the site.


DISCUSSION

Construction Timing

We understand construction is planned for the spring of 2016. Therefore, recommendations provided herein are based on wet-weather construction techniques. In the event construction is delayed until summer 2016, we should be contacted to modify our recommendations to reflect dry weather construction.

The fine-grained soils underlying the site are moisture-sensitive and will soften considerably when wet and exposed to construction traffic. Wet-weather construction will require a thickened building pad and access roads to support construction traffic and reduce the risk of subgrade damage as discussed in the Recommendations section. It has been our experience that a minimum rock section consisting of 24 inches of Select Fill over a separation geotextile is typically required to support construction traffic over wet, medium stiff to stiff soils.

Building Foundations

The explorations within the proposed building footprint encountered a subsurface profile that consists of a thin layer of topsoil underlain by ±8.5 feet of very stiff fine-grained soil, followed by medium dense gravel grading to very dense gravel to ±29 feet. Based on the conditions, we have concluded conventional shallow spread and continuous footings will be suitable to support the new building with the following site preparation.

We understand the new building will have a finished floor elevation (FFE) of El. 217.0. The FFE will extend ±2 to 3 feet above the existing grades. We also understand the bottom of the interior footings will lie ±2.5 feet below the FFE (i.e., ±El. 214.5) and the bottom of the exterior footings will lie ±3 to 4.5 feet below the FFE (i.e., ±El. 212.5 to ±El. 214.0).

High plasticity clay was encountered beneath the topsoil at depths ranging from ±9 to 12 inches (i.e., ±El. 213.3 to ±El. 213.7) below the ground surface and extends to depths of ±1.7 to 2.6 feet (i.e., ±El. 212.1 to ±El. 213.3). This material is prone to shrink and swell with changes in water content. Shrinkage or swelling of subgrade soils may cause movement (heave or differential displacement) of slabs, foundations, sidewalks and other deformation-sensitive structures if not properly mitigated. The building pad will be at least 24 inches thick. The relatively thick building pad will help reduce the risk of floor slab damage due to shrink/swell. The planned footing elevations will require excavations extending through the building pad and topsoil and extending into the high plasticity clay. We recommend completely removing the plastic clay beneath the footings to reduce the risk of damage to the structure. We estimate a nominal excavation depth of 24 inches below the base of the footings will be adequate to remove the clay. The overexcavation beneath the footings should be backfilled with compacted Select Fill.


ENGINEERING ANALYSIS

The structural engineer estimated a maximum dead load (DL) of 150 kips and live load (LL) of 175 kips for columns. An estimated maximum wall load of 3 kips per lineal foot (k/lf) was also provided. Bearing capacity and settlement analyses were completed assuming these loads.

Bearing Capacity

The field vane shear tests recorded in the foundation soils indicated undrained shear strengths typically greater than ±1 ton/ft2 (tsf). We selected an undrained shear strength of 1 tsf for our calculations to account for variation in soil strength across the building site and with depth. The analysis also assumed the footings will bear on a minimum of 24 inches of compacted Select Fill (or as required to bypass the clay) extending a minimum of 12 inches beyond the footprint of the footings.

Column footings ranging from 5 to 9.5 feet square and continuous strip footings ranging from 2 to 3-feet wide were considered. Our calculations indicate an allowable bearing pressure of 3,000 lbs/ft2 (psf) for continuous wall footings and 3,500 psf for isolated column footings and braced framed footings. The analyses assumed a typical factor of safety of 3. A one-third increase in this allowable bearing pressure may be assumed for transient (i.e., wind and seismic) loading.

We used the provided loads and the calculated bearing pressures to size the footings. Our calculations indicate a column footing size of 9.5x9.5 feet for the estimated maximum column load. We recommend a minimum continuous strip footing width of 2 feet.

Settlement

Settlement analysis was performed using the computer program Settle3D in combination with the field and laboratory testing. Consolidation data from previous tests performed on similar types of soils was used to estimate the compressibility properties of the very stiff silt. Footing sizes, as discussed above, were considered for design. Our analysis assumed a column load of 225 kips (150 kip DL + 75 kip sustained LL), and a wall load of 3 k/lf. We also assumed all footings will bear on 24 inches of compacted Select Fill.

Our analysis indicates total foundation settlement of less than ±½ inch. Differential settlement between adjacent footings may be assumed to be approximately half of the total settlement.

Sliding Coefficient and Passive Resistance

A sliding coefficient of 0.5 is recommended for footings poured on compacted Select Fill.


Passive resistance of the soil in front of the footings was calculated as an equivalent fluid density equal to γ*Kp, where γ is the unit weight of the soil and Kp is the passive earth pressure coefficient. We assumed an angle of internal friction (φ) of 30 degrees and a moist unit weight of 115 pcf for design, assuming the footings would be backfilled with compacted Select Fill surrounded by native, fine-grained soil. We recommend an equivalent fluid density of ±345 pcf as an ultimate passive resistance (assuming drained conditions).

The base sliding resistance will develop with very small translational movement. However, development of the full passive resistance could be mobilized in front of the buried footings during an earthquake without undue translation of the footings. Assuming small movements (on the order of a fraction of an inch), we recommend using one-third of the ultimate passive resistance in combination with the base friction. Therefore, a coefficient of friction of 0.5 and an allowable passive resistance of ±115 pcf are recommended for design.

Slab-on-Grade

The slab will be supported on a minimum of 24 inches of compacted Select Fill or Granular Site Fill, capped with Select Fill underlain by undisturbed native soil. A modulus of subgrade reaction of 250 lb/in3 (pci) is recommended for floor slab design.

Pavement Analysis and Design

Employee, public, and police vehicle parking lots are planned around the new building. An average daily traffic (ADT) count was not available at the time this report was written. Based on the size of the facility, we assumed an ADT of 200 vehicles for design. We assumed the design ADT would include five (5), 2 to 3-axle delivery trucks based on information from the design team. A subgrade resilient modulus (Mr) value of 3,000 psi was selected for analysis based on an assumed California Bearing Ratio (CBR) value of 2.

We used the assumed traffic and subgrade modulus, and a 20-year design life to estimate a pavement section for the new parking lots. Based on our analyses, we recommend a minimum flexible pavement section consisting of 3 inches of asphaltic concrete (AC) over 12 inches of base rock (Select Fill) for parking stalls and pavement section consisting of 4 inches of AC over 12 inches of base rock for all other areas subject to heavier vehicle traffic.

The explorations within the proposed parking areas encountered a subsurface profile that consists of a thin layer of topsoil underlain by high plasticity clay extending to depths of ±2.2 to 2.9 feet (±El. 211.6 to ±El. 212.5). Very stiff, low plasticity silt is present beneath the clay. If constructed at or near current grades, the pavement subgrade will likely consist of high plasticity clay. As discussed previously, this material is prone to shrink and swell with changes in water content. Shrinkage or swelling of the pavement subgrade may cause movement (heave or differential displacement) and a reduced pavement life. Complete removal of the clay beneath pavements may not


be economically practical. At a minimum, we recommend increasing the base rock thickness to 24 inches or adding a 12 inch subbase section consisting of granular fill (Granular Site Fill) beneath the 12-inch base rock section to reduce the risk of pavement damage due to shrink/swell. Assuming the site work will be completed in the spring (during wet weather or when the soils are still wet of optimum), the thickened base rock or base/subbase section described above will likely be needed to protect the wet subgrade from softening due to construction traffic.

RECOMMENDATIONS

Construction recommendations provided below are based on the earthwork occurring during wet weather. Depending on the actual time of year construction begins, modifications to the respective recommendations may be required. Therefore, we recommend a preconstruction conference with the earthwork subcontractor to review the recommendations and make any necessary adjustments at that time.

General Earthwork and Material Recommendations

1. Select Fill as defined in this report should consist of 1 or ¾-inch minus, clean (i.e., less than 5% passing the #200 U.S. Sieve), well-graded, crushed gravel or rock.

2. Granular Site Fill should consist of 3-inch minus, clean, well-graded, crushed (quarry) rock or approved bar-run gravel. The latter is appropriate only if placed during dry weather or when the gravel is adequately dry for compaction.

3. Drain Rock should consist of 1 to 2-inch, clean (less than 2% passing the #200 sieve), open-graded gravel or rock.

4. Filter Fabric as defined in this report should consist of a non-woven geotextile with a grab tensile strength greater than 200 lb., an apparent opening size (AOS) of between #70 and 100 (US Sieve), and a permittivity greater than 0.1 sec-1.

5. Separation Geotextile should have Mean Average Roll Value (MARV) strength properties meeting the requirements of an AASHTO M 288-06 Class 2 woven geotextile.

The geotextile should have MARV hydraulic properties meeting the requirements of AASHTO M 288-2006 (geotextile for separation) with a permittivity greater than 0.10 sec.-1 and an AOS less than 0.6 mm. We should be provided a specification sheet on the selected geotextile for approval prior to delivery to the site.


6. Compact all fill in loose lifts not exceeding 12 inches. Thinner lifts (8 inches or less) will be required if light or hand-operated equipment is used. Compact all fill to a minimum of 95% relative compaction, unless otherwise specified. The maximum dry density of ASTM D 698 should be used as the standard for estimating relative compaction, unless otherwise specified. Field density tests should be run frequently to confirm adequate compaction of the fill.

7. Overexcavate all test pits that extend under the building and pavements. Replace the test pit backfill with compacted Select Fill. The test pit locations identified on Figure 2A (Appendix A) should be considered approximate only. The test pit locations were staked in the field at the time of the explorations.

8. Inform contractors that utility construction may encounter perched ground water and require dewatering for any excavations completed during wet weather. Shoring will be needed in all trenches to protect workers from sloughing or caving soils. Assume an OR-OSHA Type B soils for planning utility trenching and/or shoring (OR-OSHA, 2011). This soil may degrade to an OSHA Type C soil when exposed to sustained wet weather or in the presence of ground water.

Site Preparation for Building

We recommend the site grading be completed as follows during wet weather:

9. Strip the existing ground ±6 inches, or as required to remove roots and sod. Haul all strippings from the site.

10. Excavate to the depth required to accommodate a minimum 24-inch thick building pad. Dispose of all spoils outside of construction areas.

Complete the excavation using a hoe equipped with a smooth bucket to minimize disturbance to the fine-grained subgrade. The excavator should operate from outside of the excavation or from a thickened rock section extending into the excavation. Do not permit vehicles or construction equipment on the subgrade unless they are supported on a minimum of 24 inches of compacted Select Fill. Do not expose more subgrade than can be covered with rock the same day.

11. Grade the subgrade to promote drainage away from the building area. If needed, install a sump and dewater the excavation prior to placing the Separation Geotextile and Select Fill. Overexcavate areas that are soft or have been disturbed by construction traffic.

12. Place a Separation Geotextile on the prepared subgrade that meets the requirements specified in Item 5. The geotextile should be laid smooth, without wrinkles or folds, in the direction of construction traffic. Overlap adjacent rolls a minimum of 2 feet. Pin fabric overlaps or place


the granular fill in a manner that will not separate the overlap during construction. Seams that have separated will require removal of the granular fill to establish the required overlap.

13. Construct the building pad using Select Fill. A minimum building pad thickness of 24 inches is recommended to support construction traffic during wet weather. The fill should be end-dumped outside the building area and pushed over the Separation Geotextile using a low ground-pressure dozer. Compact the fill as specified in Item 6. If the subgrade is wet or the fill is placed during wet weather, the initial lift may need to be thickened to ±18 inches to reduce the risk of subgrade softening.

14. Grade the finished ground surface surrounding the building to promote runoff away from the foundations.

Foundation Design and Construction

Foundation construction should be in general accordance with the following recommendations.

15. Design all continuous wall footings using an allowable bearing pressure of 3,000 psf. Design all isolated column and braced-framed footings using an allowable bearing pressure of 3,500 psf. A one-third increase in these allowable bearing pressures may be assumed for transient (i.e., wind and seismic) loading. These values assume the footings are underlain by at least 24 inches of Select Fill extending a minimum of 12 inches beyond the footprint of the footings.

16. Assume total settlements of ½ inch or less, if the footings are designed, and built as recommended herein. Differential settlement between adjacent footings may be assumed to be approximately half of the total settlement values.

17. Design the structure using the seismic parameters shown on Figure 3A (Appendix A).

18. Excavate for footings using a hoe equipped with a smooth bucket. The excavation should be deep enough to remove the plastic clay and accommodate a minimum of 24 inches of compacted Select Fill beneath the footings. Excavations should terminate in light brown, stiff silt having a minimum undrained shear strength of 1 tsf. All footing excavations should be evaluated by a Foundation Engineering representative prior to backfilling.

19. Backfill the footing excavations using Select Fill compacted as specified in Item 6. Place the fill in a minimum of two lifts.


20. Use a modulus of subgrade reaction, ks, of 250 pci for floor slab design. This value assumes the slabs will be supported on a minimum of 24 inches of compacted Select Fill underlain by stiff subgrade. Reinforce all floor slabs to reduce the risk of cracking and warping.

21. Provide a suitable vapor barrier under the slab that is compatible with the proposed floor covering and the method of slab curing. The proposed vapor barrier and installation plan should be reviewed by the flooring manufacturer and architect.

22. Provide a minimum of 6 inches of compacted Select Fill beneath isolated concrete slabs and sidewalks. The Select Fill should be placed on firm, relatively undisturbed subgrade. The minimum Select Fill thickness may need to be increased to 12 inches if the work occurs during wet weather to reduce the risk of subgrade softening. All isolated slabs and sidewalks should be reinforced with rebar to help reduce cracking and crowning.

Foundation Drainage

23. Install a foundation drain along the perimeter of the building. The drain should consist of 3 or 4-inch diameter, perforated or slotted, PVC pipe. The flow line of the pipe should be set at the base of the perimeter foundation. The pipe should be bedded in at least 4 inches of Drain Rock and backfilled to within 6 inches of the ground surface with Drain Rock. The entire mass of Drain Rock should be wrapped in Filter Fabric that laps at least 12 inches at the top.

24. Provide clean-outs at appropriate locations for future maintenance of the drainage systems.

25. Discharge the foundation drain by gravity flow into the nearest storm drain. If necessary, discharge the water into a common sump and pump it to an appropriate disposal location.

Subgrade Preparation and Pavement Construction

The following recommendations assume the parking lots will be constructed at or near existing grades during wet weather.

26. Strip the existing ground ±6 inches, or as required to remove roots and sod. Haul all strippings from the site.

27. Excavate the pavement areas to the required subgrade elevation and dispose of the material off site. The excavation depth should accommodate a Base Rock section of 24 inches of Select Fill or 12 inches of Select Fill (Base Rock) over 12 inches of Granular Site Fill (Subbase). Overexcavate any soft subgrade and replace it with compacted Select Fill or Granular Site Fill.


28. Complete the excavation using a hoe equipped with a smooth bucket to minimize disturbance to the fine-grained subgrade. The excavator should operate from outside of the excavation or from a thickened rock section extending into the excavation.

29. Do not permit heavy trucks on the subgrade. Heavy trucks should operate on a minimum of 24 inches of compacted Select Fill or 12 inches of compacted Select Fill over 12 inches of compacted Granular Site Fill. Do not expose more subgrade than can be covered with rock the same day.

30. Place a Separation Geotextile on the prepared subgrade that meets the requirements specified in Item 5. The Separation Geotextile should be laid smooth, without wrinkles or folds, in the direction of construction traffic. Overlap adjacent rolls a minimum of 2 feet. Pin fabric overlaps or place the granular fill in a manner that will not separate the overlap during construction. Seams that have separated will require removal of the granular fill to establish the required overlap.

31. Place Select Fill or Granular Site Fill over the Separation Geotextile to construct the Base Rock/Subbase section. The fill should be end-dumped outside the building area and pushed over the Separation Geotextile using a low ground-pressure dozer. Compact the fill as specified in Item 6. If the subgrade is wet or the fill is placed during wet weather, the initial lift may need to be thickened to ±18 inches prior to compaction to reduce the risk of subgrade softening.

32. Proof-roll the prepared Base Rock section prior to paving. Overexcavate and replace any areas of pumping Base Rock and/or subgrade with additional Select Fill.

33. Provide 3 inches of AC for the parking stalls and 4 inches of AC for all other paved areas. Compact the AC to a minimum of 91% relative compaction according to the theoretical maximum density calculated from the Rice specific gravity.

DESIGN REVIEW/CONSTRUCTION OBSERVATION/TESTING

Foundation Engineering should be provided the opportunity to review all drawings and specifications that pertain to site preparation and foundation and pavement construction. Foundation preparation will require field confirmation of subgrade conditions in accordance with recommendations provided herein. We recommend we be present to confirm the soil conditions beneath the building pad, footings, and pavement excavation prior to backfilling. Mitigation of any undocumented fill, high plasticity clay, foundation subgrade pumping or persistent ground water infiltration will also require engineering review and judgment. That judgment should be provided


by one of our representatives. Frequent field density tests should be run on all fill. We recommend we be retained to provide the necessary construction observations.

VARIATION OF SUBSURFACE CONDITIONS, USE OF THIS REPORT AND WARRANTY

The analyses, conclusions and recommendations contained herein assume the soil conditions encountered in the borehole and test pits are representative of the overall site conditions. The above recommendations assume we will have the opportunity to review final drawings and be present during construction to confirm the assumed foundation conditions. No changes in the enclosed recommendations should be made without our approval. We will assume no responsibility or liability for any engineering judgment, inspection or testing performed by others.

This report was prepared for the exclusive use of the City of Albany and their design consultants for the Albany Police Station project in Albany, Oregon. Information contained herein should not be used for other sites or for unanticipated construction without our written consent. This report is intended for planning and design purposes. Contractors using this information to estimate construction quantities or costs do so at their own risk. Our services do not include any survey or assessment of potential surface contamination or contamination of the soil or ground water by hazardous or toxic materials. We assume those services, if needed, have been completed by others.

Climate conditions in western Oregon typically consist of wet weather for almost half of the year (typically between mid-October and late May). It is assumed adequate drainage will be provided for construction. The recommendations for site preparation and foundation drainage are not intended to represent any warranty (expressed or implied) against the growth of mold, mildew or other organisms that grow in a humid or moist environment.

Our work was done in accordance with generally accepted soil and foundation engineering practices. No other warranty, expressed or implied, is made.

REFERENCES

AASHTO, 1993, Guide for Design of Pavement Structures, American Association of State Highway and Transportation Officials (AASHTO).

AASHTO, 2006, Geotextile Specification for Highway Applications, American Association of State Highway and Transportation Officials (AASHTO), M 288-06, 21 p.

IBC, 2012, International Building Code, prepared by the International Code Council, Inc., Sections 1613 and 1803.3.

ODOT, 2011, ODOT Pavement Design Guide, Oregon Department of Transportation (ODOT), Pavement Services Unit, August 2011.


OR-OSHA, 2011, Oregon Administrative Rules, Chapter 437, Division 3 - Construction, Subdivision P - Excavations, Oregon Occupational Safety and Health Division (OR-OSHA).

OSSC, 2014, Oregon Structural Specialty Code (OSSC): Based on the International Code Council, Inc., 2012 IBC, Sections 1613 and 1803.3.

USGS (2008b, National Seismic Hazard Mapping Project, US Seismic Design Maps, USGS website: http://earthquake.usgs.gov/designmaps/us/application.php.

Appendix A

Figures



Notes:1. The Design Response Spectrum is based on IBC 2012 Section 1613.

2. The following parameters are based on the modified USGS 2008 maps provided in IBC 2012/OSSC 2014:

Site Class= D Damping = 5%SS = 0.90 Fa = 1.14 SMS = 1.02 SDS = 0.68

S1 = 0.44 Fv = 1.56 SM1 = 0.69 SD1 = 0.46

3. SS and S1 values indicated in Note 2 are the mapped, risk-targeted maximum considered earthquake spectral acclerations for 1% probability of exceedence in 50 years.

4. Fa and Fv were established based on IBC 2012, Tables 1613.3.3(1) and 1613.3.3(2) using the selected SS and S1 values. SDS and SD1 values include a 2/3 reduction on SMS and SM1 as discussed in IBC 2012 Section 1613.3.4.

5. Site location is: Latitude 44.6167, Longitude -123.1146.

Project 2151053

FIGURE 3A

Albany Police StationAlbany, Oregon

IBC 2012/OSSC 2014 SITE RESPONSE SPECTRUM

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 0.5 1 1.5 2 2.5 3

Spec

tral

Acc

eler

atio

n, S

a(g

)

Period (seconds)

IBC 2012/OSSC 2014Response Spectrum

Appendix B

Boring and Test Pit Logs



Very stiff silty CLAY, scattered organics (CL);grey-brown and iron-stained, dry, low to mediumplasticity, organics consist of fine roots, (topsoil).Very stiff CLAY (CH); grey and iron-stained, damp,high plasticity, (alluvium).Very stiff SILT, trace sand (ML); brown, damp tomoist, low plasticity, fine to coarse sand, (alluvium).

Silty sandy gravel lens (±5 inches thick) at ±5 feet.

Medium dense clayey GRAVEL, some sand (GC);grey, wet, medium plasticity clay, fine to coarse sand,fine to coarse gravel, subrounded to rounded gravel,(alluvium).

Very dense sandy GRAVEL, trace silt (GP); grey, wet,low plasticity silt, fine to coarse sand, fine to coarsegravel, subrounded to rounded gravel, (alluvium).

Caving from ±17 to 20 feet.

Hard SILT (ML); grey, damp, low to medium plasticity,blocky structure, (alluvium).

SS-1-1

SH-1-2SS-1-3

SS-1-4

SS-1-5

SS-1-6

SS-1-7

SS-1-8

SS-1-9

SS-1-10

Backfilledwith

bentonitechips

213.31.0

211.82.5

204.89.5

199.315.0

185.329.0


Moisture, %

RQD., %


Elev.

Depth Water Table0 50 1000 50 100

Depth

Feet

Soil and Rock Descriptionand

CommentsLog

SPT,N-Value

DepthSamples

Installations/N-Value

Water Table

Moisture, %

RQD., %Recovery

Elev.Samples

Installations/

Recovery

Depth

Feet


CommentsLog

SPT,

0.0

Surface Elevation: Albany Police Station

Project No.:

Page 1 of 2

214.3

Boring Log: BH-1

June 30, 2015

214.3 feet (Approx.)

Page 1 of 2

214.3

Albany, Oregon

Boring Log: BH-1

June 30, 2015Date of Boring:

2151053


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Albany, Oregon

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Date of Boring:

2151053Project No.:

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38

Scattered sand lenses and no blocky structure below±40 feet.

Dense silty SAND (SM); dark grey, wet, low plasticitysilt, fine sand, (alluvium).

Very stiff CLAY (CH); grey, moist, high plasticity,(alluvium).

BOTTOM OF BORING

SS-1-11

SS-1-12

SS-1-13

SS-1-14

169.345.0

164.350.0

162.851.5


Project No.:

Page 2 of 2

182.3

Boring Log: BH-1

June 30, 2015


Page 2 of 2

182.3

Albany, Oregon

Boring Log: BH-1

June 30, 2015Date of Boring:

2151053


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Albany, Oregon

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Date of Boring:

2151053Project No.:


Moisture, %

RQD., %


Elev.

Depth Water Table0 50 1000 50 100

Depth

Feet


CommentsLog

SPT,N-Value

DepthSamples

Installations/N-Value

Water Table

Moisture, %

RQD., %Recovery

Elev.Samples

Installations/

Recovery

Depth

Feet


CommentsLog

SPT,

34

31

40

19

34

31

40

19

34

31

40

19

34

31

40

19

S-1-1

S-1-2

Very stiff silty CLAY, trace gravel and scattered organics (CL);brown and iron-stained, dry, low to medium plasticity, fine gravel,subrounded gravel, organics consist of fine roots, (topsoil).Very stiff CLAY (CH); grey, manganese and iron-stained, dry,high plasticity, (alluvium).

Very stiff SILT (ML); brown, moist, low plasticity, (alluvium).

BOTTOM OF TEST PIT

>1.0

>1.0

Surface: grassFine roots extend to ±12 inches.

No seepage or ground waterencountered to the limit of excavation.

Albany, Oregon

Surface Elevation:

Date of Test Pit:

Project No.:

215.3 feet (Approx.) Albany Police Station

June 29, 2015

2151053 Test Pit Log: TP-1

Comments

Sym

bo

l

Dep

th,

Fee

t

Sam

ple

#

Lo

cati

on

Cla

ss S

ymb

ol

Wat

er T

able

C, T

SF

Soil and Rock Description

1

2

3

4

5

6

7

8

9

S-2-1

S-2-2

S-2-3

Very stiff silty CLAY, scattered organics (CL); grey-brown andiron-stained, dry, low to medium plasticity, organics consist offine roots, (topsoil).Very stiff CLAY (CH); grey and iron-stained, damp, highplasticity, (alluvium).


Medium dense to dense silty sandy GRAVEL (GM); brown,moist, medium plasticity silt, fine to coarse sand, fine to coarsegravel, subrounded to rounded gravel, (alluvium).Very stiff SILT (ML); brown, damp, low plasticity, (alluvium).BOTTOM OF TEST PIT

>1.0

>1.0

>1.0



Albany, Oregon

Surface Elevation:

Date of Test Pit:

Project No.:


June 29, 2015


Comments

Sym

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Dep

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Fee

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C, T

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1

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5

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7

8

9

S-3-1

S-3-2

Very stiff silty CLAY, scattered organics (CL); grey-brown andiron-stained, dry, low to medium plasticity, organics consist offine roots, (topsoil).Very stiff CLAY, trace sand (CH); grey and iron-stained, damp,high plasticity, fine to coarse sand, (alluvium).


BOTTOM OF TEST PIT

>1.0

>1.0



Albany, Oregon

Surface Elevation:

Date of Test Pit:

Project No.:


June 29, 2015


Comments

Sym

bo

l

Dep

th,

Fee

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Sam

ple

#

Lo

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C, T

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1

2

3

4

5

6

7

8

9

S-4-1

S-4-2

Very stiff silty CLAY, scattered organics (CL); brown, dry todamp, low to medium plasticity, organics consist of fine roots,(topsoil).Very stiff CLAY, trace gravel (CH); grey and iron-stained, damp,high plasticity, fine gravel, subrounded gravel, (alluvium).

Stiff SILT, trace gravel (ML); brown, moist, low plasticity, finegravel, subrounded gravel, (alluvium).Medium dense silty GRAVEL, some sand (GM); grey-brown,moist, medium plasticity silt, fine to coarse sand, fine to coarsegravel, subrounded to rounded gravel, (alluvium).Stiff SILT (ML); brown, moist, low plasticity, (alluvium).BOTTOM OF TEST PIT

>1.0

0.70



Albany, Oregon

Surface Elevation:

Date of Test Pit:

Project No.:


June 29, 2015


Comments

Sym

bo

l

Dep

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Fee

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Sam

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#

Lo

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Cla

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ymb

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C, T

SF


1

2

3

4

5

6

7

8

9

S-5-1

S-5-2

S-5-3

S-5-4

Very stiff silty CLAY, scattered organics (CL); grey-brown andiron-stained, dry, low to medium plasticity, organics consist offine roots, (topsoil).Very stiff CLAY, trace sand (CH); grey and iron-stained, damp,high plasticity, fine sand, (alluvium).Very stiff SILT (ML); brown, moist, low to medium plasticity,(alluvium).

Medium dense to dense silty sandy GRAVEL (GM); brown,moist, medium plasticity silt, fine to coarse sand, fine to coarsegravel, subrounded to rounded gravel, (alluvium).Very stiff SILT, trace sand (ML); brown, damp, low plasticity, fineto coarse sand, (alluvium).Moist below ±5.5 feet.

BOTTOM OF TEST PIT

>1.0

>1.0



Albany, Oregon

Surface Elevation:

Date of Test Pit:

Project No.:


June 29, 2015


Comments

Sym

bo

l

Dep

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Fee

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1

2

3

4

5

6

7

8

9

S-6-1

S-6-2

S-6-3

S-6-4

S-6-5

Very stiff silty CLAY, scattered organics (CL); grey andiron-stained, dry, medium plasticity, organics consist of fineroots, (topsoil).Very stiff CLAY, trace sand (CH); grey and iron-stained, damp,high plasticity, fine sand, (alluvium).Very stiff SILT (ML); brown, moist, low plasticity, (alluvium).

Medium dense to dense silty sandy GRAVEL (GM); brown,moist, medium plasticity silt, fine to coarse sand, fine to coarsegravel, subrounded to rounded gravel, (alluvium).

Very stiff SILT, trace sand (ML); brown, damp, low plasticity, finesand, (alluvium).

BOTTOM OF TEST PIT

>1.0

>1.0



Albany, Oregon

Surface Elevation:

Date of Test Pit:

Project No.:


June 29, 2015


Comments

Sym

bo

l

Dep

th,

Fee

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Sam

ple

#

Lo

cati

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ymb

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Wat

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able

C, T

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1

2

3

4

5

6

7

8

9

S-7-1

S-7-2

S-7-3

S-7-4

S-7-5

Very stiff silty CLAY, trace gravel, scattered organics (CL); brownand iron-stained, dry to damp, low plasticity, fine gravel,subrounded gravel, organics consist of fine roots, (topsoil).Very stiff CLAY (CH); grey and iron-stained, damp, highplasticity, (alluvium).Very stiff SILT (ML); brown, damp to moist, low to mediumplasticity, (alluvium).Medium dense to dense silty sandy GRAVEL (GM); grey-brown,moist, medium plasticity silt, fine to coarse sand, fine to coarsegravel, subrounded to rounded gravel, (alluvium).Very stiff SILT (ML); brown, damp, low plasticity, fine sand,(alluvium).

Moist below ±6.5 feet.

BOTTOM OF TEST PIT

>1.0



Albany, Oregon

Surface Elevation:

Date of Test Pit:

Project No.:


June 29, 2015


Comments

Sym

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Fee

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1

2

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5

6

7

8

9

S-8-1

S-8-2

S-8-3

S-8-4

S-8-5

Very stiff silty CLAY, trace gravel, scattered organics (CL); greyand iron-stained, dry, medium plasticity, fine gravel, subroundedgravel, organics consist of fine roots, (topsoil).Very stiff CLAY (CH); grey and iron-stained, damp, highplasticity, (alluvium).

Very stiff SILT (ML); brown and iron-stained, damp to moist, lowplasticity, (alluvium).Medium dense silty sandy GRAVEL (GM); grey-brown, moist,medium plasticity silt, fine to coarse sand, fine to coarse gravel,subangular to subrounded gravel, (alluvium).Very stiff SILT, trace sand (ML); brown, moist, low plasticity, fineto coarse sand, (alluvium).

No sand below ±7 feet.

BOTTOM OF TEST PIT

>1.0



Albany, Oregon

Surface Elevation:

Date of Test Pit:

Project No.:


June 29, 2015


Comments

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Appendix C

Seismic Hazard Study



Albany Police Station July 15, 2015

Seismic Hazard Study 1. Project 2151053

Albany, Oregon City of Albany

SEISMIC HAZARD STUDY ALBANY POLICE STATION

ALBANY, OREGON

INTRODUCTION

The seismic hazard study was completed to identify potential geologic and seismic

hazards and evaluate the effect those hazards may have on the proposed project.

The study fulfills the requirements presented in the 2014 Oregon Structural Specialty

Code (OSSC), Section 1803 for site-specific seismic hazard reports for essential and

hazardous facilities and major and special-occupancy structures (OSSC, 2014).

The following sections provide a discussion of the regional geology, seismic and

tectonic setting, earthquakes and seismic hazards. A detailed discussion of the

subsurface conditions at the project location including exploration logs is provided in

the main report.

LITERATURE REVIEW

Available geologic and seismic publications and maps were reviewed to characterize

the local and regional geology and evaluate relative seismic hazards at the site. Local

water well logs available from the Oregon Water Resources Department (OWRD)

website and information from several other geotechnical and seismic hazard

investigations previously conducted by Foundation Engineering in the Albany area

were also reviewed.

Regional Geology

The site is located within the central Willamette Valley. The Willamette Valley is a

broad, north-south-trending basin separating the Coast Range to the west from the

Cascade Range to the east. In the early Eocene (±50 to 58 million years ago), the

Willamette Valley was part of a broad continental shelf extending from the Western

Cascades west beyond the present coastline (Orr and Orr, 1999). Basement rock

underlying most of Willamette Valley includes the Siletz River Volcanics, which

erupted as part of a submarine oceanic island-arc. The thickness of the basement

volcanic rock is unknown; however, it is estimated to be ±3 to 4 miles thick (Yeats

et al., 1996).

The island-arc collided with and was accreted to the western margin of the

converging North American Plate near the end of the early Eocene. Volcanism

subsided and a fore arc basin was created and infilled (primarily to the south) with

marine sediments of the Flournoy, Yamhill, Spencer and Eugene Formations

throughout the late Eocene and Oligocene and terrestrial sedimentary deposits of the

Fisher Formation and Little Butte Volcanics of the Oligocene (Orr and Orr, 1999).

These marine sediments typically overlie, but are also interbedded with the basalt

and volcanics of the Siletz River Volcanics and younger Tertiary volcanics.




After emerging from a gradually shallowing ocean, the marine and volcanic

formations were covered by the terrestrial Columbia River Basalt. The basalt poured

through the Columbia River Gorge from northeastern Oregon and southwestern

Washington, spreading as far south as Salem (±17 to 10 million years ago) (Tolan

et al., 2000) with some flows reaching the Pacific Ocean (Crenna and Yeats, 1994).

Uplift and tilting of the Coast Range and the Western Cascades during the late

Miocene formed the trough-like configuration of the Willamette Valley. Thick layers

of Pleistocene and Holocene fluvial and floodplain deposits blanket the Columbia

River Basalt and older Tertiary deposits (Orr and Orr, 1999; Tolan et al., 2000).

Catastrophic flood deposits later appeared during the Pleistocene (over 15,000 years

ago) and now mantle the Willamette Valley floor as far south as Eugene (Hampton,

1972; Yeats et al., 1996). These deposits originated from a series of glacial-outburst

floods that periodically drained Glacial Lake Missoula in western Montana. The older

deposits, typically found within the Portland Basin, usually consist of layers of

cobbles/boulders, gravel and sand during a period of time when the river(s) had

sufficiently high flow to move large boulders (i.e., erratics). In the Southern

Willamette Valley, turbid floodwater eventually settled, depositing a relatively thick

layer (50 to 100 feet) of silt and clay (i.e. Willamette Silt) (Orr and Orr, 1999; Wiley,

2006).

Tectonic Setting

The central Willamette Valley lies ±120 miles inland from the surface expression of

the Cascadia Subduction Zone (CSZ) (Goldfinger et al., 1992). The CSZ is a

converging, oblique plate boundary where the Juan de Fuca plate is being subducted

beneath the western edge of the North American continent (Geomatrix Consultants,

1995). The CSZ extends from central Vancouver Island in British Columbia, Canada,

through Washington and Oregon to Northern California (Atwater, 1970). Available

information indicates the CSZ is capable of generating earthquakes within the

descending Juan de Fuca plate (intraplate), along the inclined interface between the

two plates (interface or subduction zone), or within the overriding North American

Plate (crustal) (Weaver and Shedlock, 1996). Therefore, western Oregon is located

in an area of potentially high seismic activity due to its proximity to the CSZ.

Local Faulting

A review of nearby faults was completed to establish the seismic setting and the

seismic sources. Numerous concealed and inferred crustal faults are located within

±10 miles of the site (Beaulieu et al., 1974; Yeats et al., 1996; Wiley, 2006).

However, none of these faults show any evidence of movement in the last

±1.6 million years (Geomatrix Consultants, 1995; USGS, 2006). Five potentially

active Quaternary (<1.6 million years or less) crustal fault zones have been mapped

within ±40 miles of the site and are listed in Table 1C.

The approximate locations of the central Willamette Valley faults in Table 1C are

shown on Figure 1C, and additional fault information is available in the literature

(Personius et al., 2003; USGS, 2006).




All but the Corvallis fault are considered a USGS Class A fault. Class A faults have

geologic evidence supporting tectonic movement in the Quaternary, known or

presumed to be associated with large-magnitude earthquakes (Personius et al.,

2003).

The source of the co-seismic displacement on faults located within the Cascadia

forearc (along the coast) is not fully known. The displacement might be caused by

subduction zone megathrust earthquakes or other smaller earthquakes within the

North American plate (USGS, 2006). The USGS (2008) interactive deaggregation

indicates the primary seismic sources affecting the site are the CSZ faults, Western

US gridded, and deep intraplate. Additional fault information can be found in the

literature (Personius et al., 2003; USGS, 2006; USGS, 2015).

Table 1C. Potentially Active Quaternary Crustal Faults

within ±50 miles of Albany1

Fault Name Length (miles) Distance from Site

(miles) 2

Most Recent

Estimated

Deformation

Slip Rate

(mm/yr)

Corvallis (#869) ±25 ±8 W <1.6 million years <0.20

Owl Creek (#870) ±9 ±4 SW <750,000 years <0.20

Mill Creek (#871) ±11 ±10 N-NE <1.6 million years <0.20

Waldo Hills (#872) ±8 ±16 N-NE <1.6 million years <0.20

Mount Angel (#873) ±19 ±34 NE <15,000 years 0.0673

Notes: 1. Fault data based on Personius et al., 2003, USGS, 2006 and USGS, 2015.

2. Distance from site to nearest surface projection of the fault.

3. Slip rate data from Table H-1 (Petersen et al., 2008).

Historic Earthquakes

No significant interface (subduction zone) earthquakes have occurred on the CSZ in

historic times; however, several large-magnitude (>M ~8.0, M = unspecified

magnitude scale) subduction zone earthquakes are thought to have occurred in the

past few thousand years. This is evidenced by recently discovered tsunami

inundation deposits, combined with evidence for episodic subsidence along the

Oregon and Washington coasts (Peterson et al., 1993; Atwater et al., 1995). The

Oregon Department of Geology and Mineral Industries (DOGAMI) estimates the

maximum magnitude of an interface subduction zone earthquake ranges from

moment magnitude (Mw) 8.5 to Mw 9.0 (Wang and Leonard, 1996; Wang et al.,

1998; Wang et al., 2001), and the rupture may potentially occur along the

entire length of the CSZ (Weaver and Shedlock, 1996). Interface earthquakes

are believed to have an average return period of ±400 to 700 years (Nelson and

Personius, 1996), with the last event occurring ±315 years ago (January 26, 1700)

(Nelson et al., 1995; Satake et al., 1996).




Turbidite deposits in the Cascadia Basin have been investigated to help develop a

paleoseismic record for the CSZ (Adams, 1990; Goldfinger et al., 2012). Turbidite

findings (based on the last 10,000 years) suggest an average recurrence interval of

±240 years for a large interface earthquake on the southern portion of the CSZ

(Goldfinger et al., 2012). The estimated recurrence interval for a large interface

earthquake on the northern portion of the CSZ is ±500 to 530 years (Goldfinger et

al., 2012). Older deep-sea cores were recently re-examined. The findings may

indicate greater Holocene stratigraphy variability along the Washington coast

(Atwater et al., 2014). This complicated variability suggests possible uncertainty in

the previous turbidite correlations.

Intraplate (Benioff Zone) earthquakes occur within the Juan de Fuca Plate at depths

of ±28 to 37 miles (Weaver and Shedlock, 1996). The maximum estimated

magnitude of an intraplate earthquake is about Mw 7.5 (Wang et al., 2001). No

intraplate earthquakes have been recorded in Oregon in modern times. However, the

Puget Sound region of Washington State has experienced three intraplate events in

the last ±66 years, including a surface wave magnitude (Ms) 7.1 event in 1949

(Olympia), a Ms 6.5 event in 1965 (Seattle/Tacoma) (Wong and Silva, 1998), and a

Mw 6.8 event in 2001 (Nisqually) (Dewey et al., 2002).

Crustal earthquakes dominate Oregon's seismic history. Crustal earthquakes occur

within the North American plate, typically at depths of ±6 to 12 miles. The

estimated maximum magnitude of a crustal earthquake in the Willamette Valley and

adjacent physiographic regions is about Mw 6.5 (Wang and Leonard, 1996; Wang et

al., 1998; Wang et al., 2001). Only two major crustal events in Oregon have reached

Richter local magnitude (ML) 6 (the 1936 Milton-Freewater ML 6.1 earthquake and

the 1993 Klamath Falls ML 6.0 earthquake) (Wong and Bott, 1995). The majority of

Oregon’s larger crustal earthquakes are in the ML 4 to 5 range (Wong and Bott,

1995).

Table 2C summarizes earthquakes with a M of 4.0 or greater or Modified Mercalli

Intensities (MM) of V or greater that have occurred within a ±50-mile radius of Albany

in the last 182 years (Johnson et al., 1994; ANSS, 2015). Although not listed in

Table 2C, several sources make reference to a ML = 4+ earthquake (MM=V) with

an epicenter near Corvallis. The coordinates of this earthquake (44.6 N, 123.2 W)

suggest the 1946 or 1947 event was most likely located on the Corvallis fault (Bela,

1979; Yeats et al., 1996). Yeats et al. (1996) and Geomatrix Consultants (1995)

also indicate that two other earthquakes have been felt near the Corvallis fault. One

occurred in 1957 (MM= III) and the other in 1961 (MM= III-IV).




Table 2C. Historic Earthquakes within ±50-mile Radius of Albany

Latitude 44.616802 and Longitude -123.114673

Year Month Day Hour Minute Latitude Longitude Depth

(miles)

Magnitude

or Intensity

1957 11 17 06 00 45.3 -123.8 unknown MM = VI

1896 04 02 11 17 45.2 -123.2 unknown MM = VI

1921 02 25 20 00 44.4 -122.4 unknown MM = V

1930 07 19 02 38 45.0 -123.2 unknown MM = VI

1942 05 13 01 52 44.5 -123.3 unknown MM = V

1944 03 05 13 00 45.0 -123.4 unknown MM = V

1961 08 19 04 56 44.7 -122.5 unknown M = 4.5

1963 03 07 23 53 44.9 -123.5 29.2 Mb = 4.6

1993 03 25 13 34 45.0 -122.6 12.8 Mc = 5.6

Notes: M = unspecified magnitude, Mb = compressional body wave magnitude, Mc = primary coda magnitude, and

ML = local Richter magnitude

It should be noted that seismic events in Oregon were not comprehensively

documented until the 1840's (Wong and Bott, 1995). According to Wong and

Bott (1995), seismograph stations sensitive to smaller earthquakes (ML 4 to 5) were

not implemented in northwestern Oregon until 1979 when the University of

Washington expanded their seismograph network to Oregon. Prior to 1979, few

seismograph stations were installed in Oregon. OSU (Corvallis) likely had the first

station installed in 1946 (Wong and Bott, 1995). The local Richter magnitude (ML)

of events occurring prior to the establishment of seismograph stations have been

estimated based on correlations between magnitude and MM intensities. Some

discrepancy exists in the correlations.

Distant strong earthquakes felt in the Albany area are summarized in Table 3C (Noson

et al., 1988; Bott and Wong, 1993; Stover and Coffman, 1993; Dewey et al., 1994;

Wong and Bott, 1995; Black, 1996; Dewey et al., 2002). None of these events

caused significant, reportable damage in Albany.




Table 3C. Distant Earthquakes Felt in the Albany Area

Earthquake Modified Mercalli Intensities

(MM)

2001 Nisqually, Washington IV

1993 Scotts Mills, Oregon IV-V

1965 Seattle-Tacoma, Washington I-IV

1962 Portland, Oregon I-IV

1961 Lebanon/Albany, Oregon V

1957 NW Salem, Oregon I-VI

1949 Olympia, Washington VI

1873 Crescent City, California V

Seismic Hazards

Section 1803.7 of the 2014 OSSC requires the evaluation of risks from a range of

seismic hazards including: ground motion amplification, ground rupture, earthquake

induced landslides, liquefaction and lateral spread, and tsunami/seiche.

Geologic and seismic hazard studies completed by DOGAMI include Linn County and

the City of Albany (Burns et al., 2008) and they also provide online hazard

information through HazVu, LiDAR and SLIDO (DOGAMI, 2015b). Environmental

hazard maps for Linn County, including Albany, refer to, but do not cover all the

seismic hazards (Beaulieu et al., 1974). These studies are only a guide and do not

have precedence over site-specific evaluations.

We have developed the following conclusions regarding the seismic hazards based

on our on-site explorations, the soil/bedrock profiles encountered in local water well

logs, our knowledge of the site geology, and a review of previous geotechnical and

seismic studies performed in the area. Information from the DOGAMI seismic hazard

maps is also provided for comparison.

Ground Motion Amplification. Ground motion amplification is the influence of a soil

deposit on the earthquake motion. As seismic energy propagates up through the soil

strata, the ground motion is typically increased (i.e., amplified) or decreased

(i.e., attenuated) to some extent.

The police station site is underlain by very stiff silt and clay (topsoil) followed by very

stiff silt (fine-grained alluvium) grading to medium dense clayey gravel and very dense

sandy gravel (coarse alluvium) below ±9.5 feet. The coarse-grained alluvium is

followed by hard, low to medium plasticity silt to ±45 feet. A lens of dense silty

sand extends below the hard silt. Very stiff high plasticity clay extends to the limit

of our exploration (±51.5 feet).

Based on the subsurface conditions at this site and our experience at nearby sites, it

is our opinion the amplification hazard is low to moderate and is consistent with an




OSSC/IBC Site Class D soil profile. Burns et al. (2008) indicates the amplification

susceptibility for the site is moderate (NEHRP Site Class C). According to Oregon

HazVu, the expected shaking for a M9.0 CSZ earthquake would be very strong

(DOGAMI, 2015b).

Ground Rupture. The risk of ground rupture is expected to be low due to the lack of

known faulting beneath the site (Personius et al., 2003; USGS, 2006; Wiley, 2006;

USGS, 2015). However, hidden and/or deep-seated active faults could remain

undetected. Additionally, recent crustal seismic activity cannot always be tied to

observable faults. In the event of a catastrophic earthquake with a large seismic

moment, inactive faults could potentially be reactivated.

Liquefaction, Lateral Spread and Settlement. Liquefiable soils typically consist of

loose, fine-grained sand and non-plastic or low plasticity (i.e., PI less than 8) silt

below the ground water table. These soils were not encountered in the explorations.

Therefore, it is our opinion there is no liquefaction or lateral spread hazard at the site

and no liquefaction mitigation measures are required. Seismically-induced

settlement, if any, is also expected to be modest (less than 1 inch). Burns et al.

(2008) indicates moderate liquefaction susceptibility for the project area in Albany.

Landslides and Earthquake Induced Landslides. The existing topography at the site is

relatively flat. Therefore, there is no risk of landslides or earthquake-induced

landslides. DOGAMI’s references, including LiDAR, also indicate no mapped

landslides or slope instability features at the site (Burns et al., 2008; DOGAMI,

2015c; DOGAMI, 2015a; DOGAMI, 2015b).

Tsunami / Seiche. Tsunami inundation is not applicable to this site since Albany is

not on the Oregon Coast. Seiche (the back and forth oscillations of a water body

during a seismic event) is also not a concern due to the absence of large bodies of

water near the site.

SEISMIC DESIGN

Design Earthquakes

The 2014 OSSC, Section 1803.3.2.1, requires the design of structures classified as

essential or hazardous facilities, and major and special-occupancy structures address,

at a minimum, the following earthquakes:

Crustal: A shallow crustal earthquake on a real or assumed fault near the

site with a minimum moment magnitude (MW) of 6.0 or the design

earthquake ground motion acceleration determined in accordance

with the 2014 OSSC Section 1613.

Intraplate: A deep subduction earthquake (Benioff Zone earthquake) with a

moment magnitude (MW) of 7.0 or greater on the seismogenic part

of the subducting plate (Juan de Fuca) of the CSZ.




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