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Correspondence RECE p w,' : a 9725 SW Beaverton - Hillsdale Hwy. Suite 140 JAN ry 2',e 2010 • ', � ,i G t � ; Beaverton, OR 97005 -3364 G ., �. >" L. .,� p1 503-641-3478 11503-644-8034 CITY OF TIGARD BUILDING DIVISION October 27, 2009 - 49,35 GEOTECHNICAI RPT Murray, Smith & Associates, Inc. l��O} — CM ('S 121 SW Salmon Street, Suite 900 Portland, OR 97204 OFFICE COPY Attention: Matt Hickey, PE 2 A — l' 5— L SUBJECT: Geotechnical Investigation and Site - Specific Seismic Hazard Study New Pump Station and Seismic Retrofit of Existing 10-MG Reservoir Bull Mountain Reservoir Site Tigard, Oregon At your request, GRI has completed a geotechnical investigation and site - specific seismic hazard study for the above- referenced reservoir site in Tigard, Oregon. The general location of the site is shown on the Vicinity Map, Figure 1. The purpose of the investigation was to evaluate subsurface materials and conditions at the site and develop geotechnical recommendations for use in design and construction of the new pump station, seismic retrofit of the existing tank, and street improvements on SW Bull Mountain Road and SW 125th Street. The investigation included review of available information for the site and vicinity, subsurface explorations, laboratory testing, and engineering and seismic analyses. This report describes the work accomplished and provides our conclusions and recommendations for design and construction of the proposed pump station and road improvements. As part of our study, we reviewed the original April 21, 1976, report for the site prepared by Northwest Testing Laboratories (NTL) entitled, "Soils and Foundation Investigation, Proposed Reservoir, Bull Mountain, Oregon." A copy of the report is provided in Appendix C. PROJECT DESCRIPTION The City of Tigard (City) will construct a new pump station adjacent to the existing 10 -MG Bull Mountain reservoir. The existing reservoir site is located at the intersection of SW 125th Avenue and SW Bull Mountain Road. The proposed pump station will be located in the northwest corner of the site; an existing well house is located in the southwest corner of the site. A full street improvement will be completed along SW 125th Avenue, and a half- street improvement is being considered along SW Bull Mountain Rd. The existing reservoir is 223.5 ft in diameter, embedded approximately 25 ft, and is founded near elevation 440 ft. The proposed pump station building will be about 50 by 25 ft and founded at elevation 430 ft, about 10 ft deeper than the existing reservoir. The southwest corner of the proposed pump station will be located within about 17 ft of the existing tank structure. The configuration of the reservoir site, including adjacent streets, existing tank, and proposed pump station, is shown on the Site Plan, Figure 2. Review of the existing plans indicates the concrete roof is supported by 20- in.- diameter columns on 20 -ft centers, supported on 6 -ft- square footings. The external concrete wall is supported by a 6 -ft -wide ring wall. As part of the improvements, the project team will complete a seismic evaluation of the existing reservoir. Providing geotechnical and environmental consulting services since 1984 SITE DESCRIPTION Topography and Surface Conditions The site is located on the east flank of the Bull Mountain upland. The ground surface ranges from about elevation 460 to 485 ft, and the majority of the site slopes gradually to the northwest. The proposed pump station is located in the northwest corner of the site in an existing landscape area that slopes eastward. The existing topography and site configuration are shown on Figure 2. Geology The project area is mantled with fill and Upland Silt. The Upland Silt locally consists of silt with a trace of clay and fine - grained sand. These surficial materials are underlain by basalts of the Columbia River Basalt Group. The contact between the sedimentary materials and the underlying basalt is unconformable, indicating that a considerable period of time elapsed between the solidification of the last of the basalt flows and the deposition of the overlying sedimentary materials. During this period of time, the upper portions of the basalt were subjected to surficial processes, including erosion, mass wasting, and chemical and physical degradation. These processes resulted in variable weathering of the upper portions of the basalt. SUBSURFACE CONDITIONS General Subsurface materials and conditions at the proposed pump station site were investigated on December 16, 2008, with one boring, designated B -1. The boring was advanced to a depth of 60 ft at the location shown on Figure 2. Boring B -2, made to evaluate the roadway, was advanced to a depth of 6.5 ft. Two hand - augered borings, designated HA -1 and HA -2, were advanced to depths of 6 and 5 ft, respectively, on January 5, 2009, to evaluate subsurface materials and conditions for the proposed widening of Bull Mountain Road. The field and laboratory testing programs completed for this investigation are discussed in Appendix A. Logs of borings B -1 and B -2 are provided on Figures 1A and 2A, and logs of the hand - augered borings are provided on Figure 3A. The terms used to describe the materials encountered in the borings are defined in Tables 1 A and 2A. The materials disclosed in boring B -1 are generally similar to the subsurface conditions described in the NTL report (NTL, 1976). For the purpose of discussion, the materials disclosed by the borings have been grouped into the following categories based on their physical characteristics and engineering properties. Listed as they were encountered from the ground surface downward, the units are: 1. FILL 2. SILT 3. SILT (Residual Soil) 4. BASALT 1. FILL. Silt fill was encountered from the ground surface to a depth of about 12.5 ft in boring B -1 and to depths of at least 6 and 3 ft in borings HA -1 and HA -2, respectively. The silt fill varies from light to dark brown and is highly variable in composition, typically containing a trace of fine- to coarse - grained sand and a trace to some gravel and fragmented basalt. The clay content of the silt fill varies from a trace of clay to clayey. Two N- values of 8 and 9 blows /ft recorded in boring B -1 indicate the relative consistency of the silt fill ranges from medium stiff to stiff. Soft fill was encountered in borings HA -1 and HA -2. 10 2 Scattered to significant organics were observed in the fill at depths of 2 to 6 ft in boring HA -1. The natural moisture content of the silt fill ranges from about 21 to 32 %. A 1 -ft -thick layer of angular crushed rock fill was encountered at depths of 1 and 0.5 ft in borings HA -1 and HA -2, respectively. 2. SILT. Light brown mottled rust silt (Upland Silt) was encountered below the pavement and base course fill in boring B -2 and extends to a depth of at least 6.5 ft, the maximum depth explored. The silt contains a trace of clay and fine - grained sand. An N -value of 15 blows /ft indicates the relative consistency of the silt is typically stiff. The natural moisture content of the silt is about 31%. 3. SILT (Residual Soil). The silt and fill are underlain by silt with a variable clay content, ranging from some clay to clayey. The residual soil results from complete decomposition of the underlying basalt. The residual soil is typically reddish -brown and has mottling of red, orange, rust, and black. N- values ranging from 7 to 9 blows /ft indicate the relative consistency of the residual soil ranges from medium stiff to stiff. The natural moisture content of the residual soil ranges from about 27 to 32 %. 4. BASALT. Basalt was encountered beneath the residual soil at a depth of 25 ft in boring B -1. The basalt is vesicular to non - vesicular and greenish -gray. The degree of weathering is highly variable, ranging from predominantly decomposed to moderately weathered. The relative hardness of the basalt is typically extremely soft (RO). Harder, less weathered basalt (R2 or harder) was encountered below a depth of about . 57.5 ft in boring B -1 to the maximum depth explored, 60 ft. Groundwater The borings were drilled using mud -rotary methods, which does not permit measurement of groundwater levels during drilling. Review of a nearby well log indicates the permanent groundwater table was encountered about 300 ft below the ground surface. Light groundwater seepage was encountered at a depth of about 5 ft in the hand - augered borings completed along Bull Mountain Road. In this regard, perched, shallow groundwater conditions may develop at this site following periods of prolonged or intense rainfall. The 1976 NTL report indicates that groundwater was not encountered in the borings made for that investigation. The borings extended to a maximum depth of 36 ft. CONCLUSIONS AND RECOMMENDATIONS General The boring made for this investigation indicate the proposed pump station location is mantled with up to 12.5 ft of soft to stiff silt or silt fill over medium stiff to stiff residual soil to a depth of about 25 ft. The residual soil is underlain by extremely soft (RO) basalt to a depth of about 57.5 ft, where R2 or harder • basalt was encountered. The elevation of the R2 or harder basalt is about 20 ft deeper than the planned pump station excavation. In our opinion, the primary geotechnical considerations associated with the design and construction of the proposed pump station include proximity of the excavation to the existing reservoir, deep utility excavations, and the moisture - sensitive nature of the fine - grained surface soils. With regard to the roadway improvements, uncontrolled fill was observed in the explorations along Bull Mountain Road, and some overexcavation should be anticipated. As part of this investigation, we also completed a site - specific seismic study to evaluate potential seismic hazards associated with the site and develop criteria for seismic analysis of the existing reservoir. The seismic study is discussed in detail in Appendix B. RI , 3 The following sections provide our conclusions and recommendations for design and construction of the pump station and roadway improvements. Seismic Considerations General. We understand the tank retrofit will be completed using the American Water Works Association document AWWA D110 -04, "Prestressed Concrete Water Tanks," and the 2006 International Building Code (IBC) with 2007 Oregon Structural Specialty Code (OSSC) modifications. Based on the subsurface conditions disclosed by our recent boring B -1, the 1976 NTL report, and the log for the on -site well, the site would be classified as AWWA Soil Profile Type A, within Seismic Zone Class 3. With regard to the 2007 OSSC, the site is classified as Site Class C based on the existing and proposed foundation grades. The IBC -based 0.2- and 1.0- second spectral response accelerations (Ss, Si) for the site are approximately 0.92 and 0.33 g, respectively. We understand a 0.5% damped spectrum is used to calculate sloshing heights and forces. The 5% damped design spectrum can be multiplied by a factor of 1.5 to convert the spectrum to 0.5% damping. According to the OSSC, the reservoir is considered an essential facility. For this reason, we completed a site - specific seismic hazard study for this project. Details regarding the site - specific seismic hazard study are provided in Appendix B. The results of the seismic study indicate the IBC Site Class C site coefficients are appropriate to model site amplification characteristics. As discussed in Appendix B, the estimated trace of the Canby Molalla fault zone passes approximately 1 km east of the site. Based on these findings, it is our opinion the risk of fault rupture at the site is low. Based on the site topography and soil conditions, it is our opinion the risk of earthquake- induced slope instability is low. Based on the soil conditions encountered at the site, it is our opinion the risk of liquefaction and liquefaction- induced lateral spreading, settlement, and subsidence is absent. Based on the elevation and location of the site, the risk of damage by tsunamis and /or seiches is also absent. Site Preparation The proposed pump station site is mantled with medium stiff to stiff silt fill likely associated with earthwork from the existing tank. Based on the proposed floor elevations, we anticipate the foundation subgrade for the pump station will be well below the fill that mantles the site and will be established in weathered basalt. Beneath planned improvements such as roads and slabs, the surficial organics and rooted zone should be stripped to firm subgrade. Upon completion of the site stripping, the exposed subgrade should be observed by a qualified geotechnical engineer. Areas of soft subgrade, fill, or otherwise unsuitable materials should be overexcavated to firm soil and backfilled with structural fill. Several feet of variable, uncontrolled fill were encountered in the hand - augered borings along SW Bull Mountain Road. It should be anticipated that some overexcavation will be necessary along the length of the improvements. Additional recommendations regarding roadway subgrade preparation are provided in the Roadway Fill section of this report. The fine - grained soils that mantle the site are sensitive to moisture content and are easily disturbed and softened by construction activity during wet conditions. If possible, site preparation and earthwork should 19:G$ € R 4 be accomplished during the dry summer months, typically extending from mid -May through September. It has been our experience that the moisture content of the upper approximately 2 to 3 ft of the silt soils will decrease during warm, dry weather. However, the moisture content of the soil below this depth tends to remain relatively unchanged and well above the optimum moisture content for compaction. As a result, the contractor must employ working procedures that prevent disturbance and softening of the subgrade soils. It may be necessary to construct granular haul roads and work pads to minimize disturbance of silt subgrade and support construction traffic. In general, a minimum 18- to 24 -in. thickness of relatively clean, fragmental rock having a nominal maximum size of 4 to 6 in. would be required to support heavy construction traffic and protect the subgrade during wet ground conditions. Placement of a geotextile fabric (AMOCO 2000, or equivalent) on the subgrade as a separation membrane prior to placing and compacting the granular work pad may improve the performance of haul roads and work pads. Excavation and Temporary Shoring Based on cross sections you provided, we estimate the maximum depth of excavation to construct the pump station will be about 40 ft. Due to limited room between the existing tanks, property line, and street, the excavation will require shoring. We recommend designing the temporary shoring to resist a rectangular lateral earth pressure distribution of 25 *H (psf), where H is the height of the excavation. This criterion assumes the shoring is drained and the ground behind the shoring is horizontal (i.e., non - sloping condition). Surcharge loads at the ground surface can be evaluated using the criteria provided • n Figure 3. The actual magnitude of surcharge- induced lateral loading on the shoring will depend on the contractor's approach to the work; however, a minimum uniform lateral pressure of 200 psf is often used to account for construction - related equipment and surcharge loads. If the excavation encroaches within a projected 1H:1V slope extending from the bottom of the existing reservoir footing, the surcharge loading from the tank should be considered in the shoring design. In addition, any voids between the shoring system and temporary excavation below elevation 440 ft should be immediately backfilled to reduce the risk of slope movement and loss of soil support for the existing tank. Temporary excavation slopes should be made no steeper than about 1H:1V, and permanent cut slopes should be no steeper than 2H:1V. Temporary slopes should be covered with plastic sheeting to reduce erosion during wet weather. In addition, excavation spoils and construction materials should not be stockpiled within 25 ft of the top of cut slopes. It should be emphasized that these recommendations are intended to reduce the risk of a slope failure to an acceptable level. However, implementation of these recommended cut slopes does not preclude the possibility of blocks of soil moving into the excavation. Loosened material left on the cut slopes after excavation may also tend to move into the excavation during construction. To further limit the risk of excavation failure, the excavation slopes should be monitored frequently for indications of sloughing, cracking, or seepage. Boring B - at the location of the proposed pump station disclosed the top of relatively hard, intact basalt bedrock at a depth of 57.5 ft below the ground surface, which is deeper than the planned excavation. We anticipate the silt fill, silt, and decomposed basalt overlying the harder basalt can be excavated using a hydraulic excavator. It has been our experience that the basalt within the depth of excavation and as disclosed by the boring can usually be excavated with a trackhoe equipped with rock teeth. However, zones of harder, Tess fractured rock, if present, may require rock excavation methods such as chipping. x M G/ 5 The degree of weathering of the basalt and the elevation of the contact between the soil -like decomposed basalt and basalt rock may vary significantly. We anticipate the permanent groundwater level will occur below the bottom of the excavation. However, localized, perched water may develop within the depths of excavation during the normally wet winter and spring months. A ditch should be installed at the top of the cut slopes to direct surface runoff away from the excavation. We anticipate that seepage can be controlled by pumping from temporary sumps. Structural Fill Pump Station Backfill. We anticipate up to 35 ft of backfill may be placed around the pump station walls. Due to the confined work area and relatively high moisture content of the excavated on -site, fine - grained soil, we recommend using imported granular material to backfill the pump station walls. Sand, sandy gravel, or fragmental rock of up to about 2 -in. maximum size and having less than about 5% passing the No. 200 sieve would be suitable for this purpose. Fill placed within 10 ft of the pump station walls should be compacted in the range of 93 to 95% of the maximum dry density as determined by ASTM D 698 (standard Proctor). Overcompaction of fill near the pump station should be avoided to prevent excessive lateral pressures from developing behind the walls during construction. In this regard, heavy compactors and large pieces of construction equipment should not operate within 5 ft of the tank wall. Compaction close to the wall should be accomplished with hand - operated, or small, compactors. Appropriate lift thickness will depend on the type of compaction equipment used. For hand- operated, or small, compactors, we recommend a maximum loose lift thickness of 8 in. For moderate- to heavy- weight compactors, we recommend a maximum loose lift thickness of 12 in. On -Site Materials. Excluding the surface strippings, the on -site overburden silty soils approved by the geotechnical engineer may be used to construct structural fills beneath new roadways, slabs, and sidewalks. However, the silty soils are sensitive to moisture content and can only be placed and compacted during dry weather. Care should be exercised to maintain a reasonably well - graded distribution of material sizes. Silty soils used to construct structural fills should be placed in maximum 9- in. -thick (loose) lifts and compacted using segmented -pad rollers to at least 95% of the maximum density as determined by ASTM D 698 method of compaction. Granular Material. Imported granular material used to construct structural fills or work pads during wet conditions should consist of a hard, durable fragmental rock with a nominal maximum size of up to 4 in. and with not more than about 5% passing the No. 200 sieve (washed analysis). The first lift of granular fill material placed during wet conditions should be in the range of 12 to 18 in. thick (loose). Subsequent lifts should be placed 12 in. thick (loose). All lifts should be compacted with a medium- weight (48 -in.- diameter drum), smooth, steel - wheeled roller to at least 95% of the maximum dry density, as determined by ASTM D 698 or until well keyed. Generally, a minimum of four to five passes with the roller are required to achieve the proper compaction. Utility Trench Backfill. All backfill placed in utility trench excavations within the limits of any improvements, such as the pump station, roadways, slabs, sidewalk, or similar paved areas, should consist of sand, sand and gravel, or crushed rock with a maximum size of up to 2 in. and not more than about 8% passing the No. 200 sieve (washed analysis). Granular backfill should be placed in lifts and compacted with vibratory equipment. We recommend the upper 5 ft of the trench backfill be compacted to at least r aG YR' 6 95% of the maximum dry density, as determined by ASTM D 698. Trench backfill below a depth of 5 ft should be compacted to at least 92% of the recommended standard. Appropriate lift thicknesses will depend on the type of compaction equipment used. For example, if hand - operated vibratory plate equipment is used, lifts should be limited to 6 to 8 in. thick. If trackhoe- mounted vibratory plates are used, thicker lifts may be appropriate to achieve the required compaction. Flooding or jetting the backfilled trenches with water should not be permitted. Free - Draining (Drainage) Material. Materials used to construct free - draining fills should consist of open - graded, angular crushed rock with a maximum size of up to 1 in., with not more than about 2% passing the No. 200 sieve (washed analysis). Crushed rock of 3 /4 to 1 /2 -in. gradation (drain rock) is suitable for this purpose. Utilities In our opinion, there are three major considerations in the design and construction of new utilities. 1) Provide stable excavation side slopes or support for trench sidewalls to minimize loss of ground. 2) Provide a safe working environment during construction. 3) Minimize post - construction settlement of the utility and the ground surface. The method of excavation and design of trench support are the responsibility of the contractor and subject to applicable local, state, and federal safety regulation, including the current OSHA excavation and trench safety standards. The means, methods, and sequencing of construction operations and site safety are also the responsibility of the contractor. The information provided below is for the use of our client and should not be interpreted to mean that we are assuming responsibility for the contractor's actions or site safety. According to the most recent OSHA regulations, the majority of the fine - grained soils and weathered basalt materials encountered in the boring may be classified as Type C. In our opinion, trenches less than 4 ft deep may be cut vertically and left unsupported during the normal construction sequence, i.e., assuming trenches are excavated and backfilled in the shortest possible sequence, and excavations are not allowed to remain open longer than 8 hrs. Excavations that are greater than 4 ft deep should be laterally supported or alternatively provided with stable side slopes of 1H:1V or flatter. In our opinion, adequate lateral support may be provided by common methods, such as the use of a trench shield or hydraulic shoring systems. Based on discussions with you, we understand the proposed waterline excavations will extend to an elevation similar to the finished floor of the pump station. Boring B -1 at the pump station location disclosed the top of relatively hard, intact basalt bedrock occurs at a depth of 57.5 ft, or about 20 ft deeper than the proposed excavation. We anticipate the silt fill, silt, and decomposed basalt overlying the basalt bedrock can be excavated using large hydraulic excavators. It has been our experience that the weathered and highly fractured basalt such as disclosed by the boring can often be excavated with a large trackhoe equipped with rock teeth. However, zones of hard, less fractured rock, if encountered, may require rock excavation methods such as chipping. The degree of weathering of the basalt and the elevation of the contact between the decomposed basalt and the basalt bedrock may vary significantly over short distances. 4 , JR 7 Trench shoring can be designed using the same criteria provided for the pump station shoring in the Excavation and Temporary Shoring section of this report. We anticipate that minimal seepage will be encountered in the utility trench excavations if work is completed during the drier months of the year. However, perched water may be encountered in the surface silty soils following periods of sustained heavy precipitation. In areas where groundwater inflow occurs, it may be necessary to overexcavate the trench bottom and place clean fragmental rock up to about 4 in. in size to stabilize the trench bottom. We anticipate that groundwater inflow, if encountered, can be controlled by pumping from sumps. Utility trenches within structural, pavement, and sidewalk areas should be backfilled with granular structural fill, as described in the Structural Fill section of this report. Foundation Support We anticipate the excavation for the pump station will result in a net unloading at the foundation subgrade level. Based on our exploration and review of the existing information, the subgrade will consist of residual soil /decomposed rock that overlies the basalt bedrock. In our opinion, the spread footings or base mat for the pump station can be designed to impose an allowable soil bearing pressure of 5,000 psf. This value applies to the total of dead Toad plus frequently and /or permanently applied live loads and can be increased by at least one half for the total of all loads. We estimate that foundation settlements will likely be less than 0.5 in., and the settlement will occur quickly as the fill and structural loads are placed. All crushed rock placed beneath the pump station base mat/foundation should be placed in loose lifts not exceeding a thickness of 12 in. and compacted as structural fill to at least 95% of the maximum dry density according to ASTM D 698. Fill placed beneath the pump station can consist of crushed rock and open - graded rock (drain rock) with a maximum particle size of up to 2 in. Lateral loads (seismic, soil, etc.) can be resisted partially or completely by frictional forces developed between the base of the mat slab foundation and underlying crushed rock. We recommend an ultimate value of 0.45 for the coefficient of friction between mass concrete cast directly on angular, granular structural fill. If additional lateral resistance is required, passive earth pressures against embedded foundations and the pump station walls can be computed on the basis of an equivalent fluid having a unit weight of 225 pcf for limiting lateral deflections to 1 /4 to 1 /2 in. and 300 pcf for larger deflections. These design passive earth pressures values would be applicable only if the backfill for the foundations or walls is placed as compacted structural fill. The recommended coefficient of friction values are also applicable for the frictional interaction of backfill soils against walls. Design Lateral and Uplift Pressures Design lateral earth pressures for embedded walls depend on the type of construction, i.e., the ability of the wall to yield. The two possible conditions regarding the ability of the wall to yield include the at -rest and the active earth pressure cases. The at -rest earth pressure case is applicable to a wall that is considered to be relatively rigid and laterally supported at top and bottom and therefore unable to yield. The active earth pressure case is applicable to a wall that is capable of yielding slightly away from the backfill by either sliding or rotating about its base. A conventional cantilevered retaining wall is an example of a wall v � G E 8 that develops the active earth pressure case by yielding. The embedded pump station walls should be considered non - yielding. The lateral earth pressures acting on the wall depend in part on the drainage condition behind the walls. We anticipate that granular structural fill will be used as wall backfill due to the limited area. As indicated in the groundwater section, we anticipate shallow perched groundwater can occur during periods of heavy rainfall, particularly in this situation, where the granular backfill soils will be confined by less permeable fine - grained soils. Based on discussions with you, we understand drainage options being considered for the exterior of the pump station include: 1) drain the walls and floor slab by installing a sump system in a drainage layer below and surrounding the pump station; 2) design the structure for groundwater at the ground surface; or 3) design the structure for groundwater up to an elevation where drains can be installed and water pressure can be relieved into existing gravity drains on site. If the structure is completed drained, the non - yielding walls can be designed using a lateral earth pressure based on an equivalent fluid having a unit weight of 45 pcf. This design lateral earth pressure assumes the wall backfill is completely drained, and the ground behind the wall is horizontal (i.e., non - sloping backfill). If a drainage system is installed to dissipate hydrostatic pressures below the pump station mat foundation, the mat should be underlain by a minimum 18 -in. -thick drainage blanket consisting of open - graded crushed rock with a maximum size of 1 in. and less than 2% passing the No. 200 sieve (washed analysis). Crushed rock of 3 /4- to 1 /2 -in. gradation is often used for this purpose. The drainage layer should be provided with rigid 4 -in.- diameter perforated drainage pipes designed for the imposed loads from the pump station or construction traffic, whichever is greater. The drain pipes should be placed with a maximum center -to- center spacing of about 20 ft. The drainage blanket can be drained by gravity or pumped from a sump. The drainage blanket may be capped with 2 to 3 in. of relatively clean, 3 /4 -in.- minus crushed rock to facilitate compaction of the drainage blanket and limit contamination from construction activities prior to constructing the floor slab. If this approach is adopted, the walls should also be drained by placing a minimum 2 -ft -wide zone of free - draining granular fill adjacent to the walls. The free - draining granular fill should meet the recommendations for free - draining granular fill discussed above. The remainder of the backfill between the drainage material and the shoring can consist of 1 -in. -minus crushed rock, or the contractor can elect to backfill the entire excavation with drain rock. If drainage is not provided to the exterior of the structure and the structure is designed to be watertight, the walls will be subject to full hydrostatic pressures and lateral earth pressures assuming buoyant unit weights. For this situation, the embedded . walls of the pump station can be designed on the basis of an equivalent fluid having a unit weight of 85 pcf. If drainage is provided at an intermediate elevation on the exterior walls, the lateral earth pressures can be evaluated using the criteria on Figure 4. With this option, a drain pipe should be placed within a layer of drain rock that extends from the shoring system to the pump station walls. The minimum total thickness of the drain rock should be 5 ft with at least 1 ft below and 4 ft above the pipe invert elevation. The remaining backfill above and below the drainage layer can consist of 1 /2 -in. -minus crushed rock conforming to our previous recommendations for granular structural fill. a t 9 The structure should be designed to resist the full hydrostatic uplift pressure to the assumed groundwater level for the selected drainage alternative. The uplift force is computed by multiplying the volume of the structure by the unit weight of water (62.4 pcf). Common methods used to resist the uplift force include increasing the thickness of the walls and /or base, or extending the base slab beyond the sidewalls of the structure. Regarding extending the base of the pump station beyond the sidewalls of the structure, only the compacted backfill within the limits of the outside edge of the slab should be considered as additional load to resist the uplift force. The effective weight of the submerged backfill should be evaluated using a buoyant unit weight of 60 pcf, assuming the wet well will be backfilled with granular structural fill material. Shearing stresses in the backfill above the perimeter of the base slab should provide some additional uplift resistance; however, for the purpose of design, it is recommended that the shearing resistance of the backfill be neglected. If additional resistance is required to resist uplift forces, rock anchors extending into the underlying basalt can also be considered. GRI can assist in the evaluation of this option, if necessary, when design loads are known. We recommend using a reverse triangular distribution of 10H to account for seismic earth pressures, with the resultant applied at 0.6H from the base of the wall. Surcharge loads at the ground surface can be evaluated using the criteria provided in Figure 3. Roadway Fill We understand Bull Mountain Road will be widened slightly with sliver fills to accommodate a new lane and approaches. We anticipate that less than 5 ft of embankment fill will be placed to widen the roadway, and the structural fill will be constructed with imported material. As indicated previously, some soft/loose, uncontrolled fill was observed in the hand - augered borings completed along the shoulder of SW Bull Mountain Road. We anticipate some overexcavation will be necessary to reach suitable subgrade material. Where new fill will be placed, the ground surface should be stripped to remove vegetation and loose or soft surficial materials. Imported fill can consist of sand, sandy gravel, or fragmental rock. Structural fill should be placed in 12 -in. -thick loose lifts and compacted with a vibratory roller to at least 95% of the maximum density as determined by ASTM D 698. The prepared subgrade should be evaluated by the geotechnical engineer prior to fill placement. We anticipate settlement due to the placement of 5 if of embankment fill will be less than 1 in. and will occur rapidly as the fill is placed. Final graded slopes consisting of silty and granular soils should be no steeper than 2H:1V and 1.5H:1V, respectively. Predominantly silty fill material can only be placed and compacted as structural fill during warm, dry weather conditions when the moisture content of the material can be controlled. Fill material placed during wet conditions can consist of sand, gravel, or crushed rock having less than 5% passing the No. 200 sieve (washed analysis). El 10 Pavement Recommendations We understand a full street improvement will be completed along SW 125th Avenue, and a half- street improvement is being considered along SW Bull Mountain Road. We also understand the City of Tigard has had repeated maintenance problems with the existing asphaltic -concrete (AC) pavement over trench backfill areas. Based on our experience, this poor AC performance may be due to unsuitable trench backfill material and /or lack of compaction. To reduce the risk of future maintenance in new pavement areas, we recommend the following remedial measures. 1) Identify areas of existing damaged pavement over trench areas. 2) Overexcavate trench backfill to a depth equivalent to two times the trench width. 3) Backfill the excavation with granular structural fill compacted to at least 95% of the maximum density as determined by ASTM D 698. However, care should be taken in shallow trenches to avoid damage to existing pipes or conduits. Within other pavement areas, the subgrade should be evaluated by the geotechnical engineer. Proof rolling with a dump truck may be part of the evaluation. Any identified soft areas or unsuitable subgrade areas should be overexcavated and replaced with compacted structural fill. We understand the improvement along SW 125th Avenue will be completed in accordance with the City of Tigard standard pavement section. The proposed improvements along SW Bull Mountain Road are under Washington County jurisdiction. If Washington County does not have a standard pavement section, GRI can provide design recommendations for SW Bull Mountain Road once the improvements are better defined. Design Review and Construction Services We welcome the opportunity to review and discuss construction plans and specifications for this project as they are being developed. In addition, GRI should be retained to review all geotechnical- related portions of the plans and specifications to evaluate whether they are in conformance with the recommendations provided in our report. Additionally, to observe compliance with the intent of our recommendations, design concepts, and the plans and specifications, we are of the opinion that all construction operations dealing with earthwork and foundations should be observed by a GRI representative. Our construction - phase services will allow for timely design changes if site conditions are encountered that are different from those described in this report. If we do not have the opportunity to confirm our interpretations, assumptions, and analyses during construction, we cannot be responsible for the application of our recommendations to subsurface conditions that are different from those described in this report. LIMITATIONS This report has been prepared to aid the project team in the planning and design of this project. The scope is limited to the specific project and location described herein, and our description of the project represents our understanding of the significant aspects of the project relevant to earthwork and design and construction of the pump station and roadway improvements. In the event that any changes in the design and location of the pump station as outlined in this report are planned, we should be given the opportunity it 11 to review the changes and to modify or reaffirm the conclusions and recommendations of this report in writing. The conclusions and recommendations submitted in this report are based on the data obtained from the borings made at the locations indicated on Figure 2 and from other sources of information discussed in this report. In the performance of subsurface investigations, specific information is obtained at specific locations at specific times. However, it is acknowledged that variations in soil and rock conditions may exist between exploration locations. This report does not reflect any variations that may occur between these explorations. The nature and extent of variation may not become evident until construction. If, during construction, subsurface conditions different from those encountered in the explorations are observed or encountered, we should be advised at once so that we can observe and review these conditions and reconsider our recommendations where necessary. Submitted for GRI, O 4 i, - - 1 A 1 / • rid . • ��i 30. t9� o �� C// T J. HAR� 1 n n.. wn ��/' Dwight J. Hardin, PE Scott M. Schlechter, PE, GE Principal Project Engineer This document has been submitted electronically. • �' 12 ld 133, GPI • p P� �SS 1 ill • S 1 0TH A� S' E AWAY ��� _ V R ? 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ASSOCIATFS,IN 8 C. ° FT . , , ..,„ ) r / ' / / / I ,/ , o - / ,' , , , f BLit I. MOUNTAIN POMP STATION - - - - 0 _ . ----ai.-------------- ,,,-.-,,,/,__T____-- _ _ ___1 SITE PLAN OCT 2005 10B NO. 4 H0. 2 X =mH >1 STRIP LOAD, q LINE LOAD, Qr IVIIIIII Z =nH V v NW For mS0.4: VW H II F ah = Qr 0.2n H (0.16 + n Form > 0.4: a h= z (g- SINg COS 2a) n ah ah = QI. 1.28m - n a h H (m'+ n / j (p in radians) LINE LOAD PARALLEL TO WALL STRIP LOAD PARALLEL TO WALL < X =mH POINT LOAD, Q n Z =nH OM For m S 0.4: A ikr____ W WAS- A' a h = Qn 0.28n H ar H' (0.16 + n lir Form > 0.4: ah ah = Qp 1.77m H" (m` + n o' h =ah COS NOTES: ah 1. THESE GUIDELINES APPLY TO RIGID WALLS WITH POISSON'S O l O RATIO ASSUMED TO BE 0.5 FOR BACKFILL .MATERIALS. 0 -- 2. LATERAL PRESSURES FROM ANY COMBINATION OF ABOVE - lir LOADS MAY BE DETERMINED BY THE PRINCIPLE OF SUPERPOSITION. a'h X =mH > DISTRIBUTION OF HORIZONTAL PRESSURES VERTICAL POINT LOAD MURRAY, SMITH & ASSOCIATES, INC. { 1r I , w ' BULL MOUNTAIN PUMP STATION SURCHARGE - INDUCED LATERAL PRESSURE OCT. 2009 JOB NO. 4935 FIG. 3 H� 45H v 2 45H 85H2 NOTE: SURCHARGE EFFECTS FROM TRAFFIC, CONSTRUCTION EQUIPMENT, ETC., SHOULD BE ADDED TO THE ABOVE DESIGN PRESSURES. THE ACTUAL AMOUNT OF THIS SURCHARGE WILL DEPEND ON THE CONTRACTOR'S APPROACH TO THE WORK AND MAY BE ESTIMATED USING THE GUIDELINES ON FIGURE 3. II MURRAY, SMITH & ASSOCIATES, INC. � 4 R K'h BULL MOUNTAIN PUMP STATION LATERAL EARTH PRESSURE ON NON YIELDING PERMANENT EMBEDDED WALLS OCT. 2009 JOB NO. 4935 FIG. 4 APPENDIX A Field Explorations and Laboratory Testing APPENDIX A FIELD EXPLORATIONS AND LABORATORY TESTING FIELD EXPLORATIONS Subsurface materials and conditions at the site were evaluated on December 16, 2008, with two borings, designated B -1 and B -2, and on January 5, 2009, with two hand - augered borings, designated HA -1 and HA -2. The approximate locations of the borings are shown on Figure 2. The explorations were observed and documented by a geotechnical engineer provided by our firm. Borings B -1 and B -2 were advanced to a depth of 60 and 6.5 ft, respectively, using mud -rotary methods and a truck - mounted drill rig provided and operated by Western States Soil Conservation of Hubbard, Oregon. Disturbed and undisturbed samples were obtained from the borings at 2.5- to 5 -ft intervals of depth. Disturbed samples were obtained using a standard split -spoon sampler. At the time of sampling, the Standard Penetration Test was conducted. This test consists of driving a standard split -spoon sampler into the soil a distance of 18 in. using a 140-lb hammer dropped 30 in. The number of blows required to drive the sampler the last 12 in. is known as the Standard Penetration Resistance, or N- value. The N -value provides a measure of the relative density of granular soils and the relative consistency of cohesive soils. The soil samples obtained in the split -spoon sampler were carefully examined in the field, and representative portions were saved in airtight jars for further examination and physical testing in our laboratory. In addition, relatively undisturbed samples of fine - grained, cohesive soils were obtained by pushing 3 -in.- O.D. Shelby tubes into the undisturbed soil a maximum distance of 24 in. using the hydraulic ram of the drill rig. The soil exposed in the end of the Shelby tube was examined and classified in the field. After classification, the tubes were sealed with plastic caps and returned to our laboratory for further examination and testing. Logs of borings B -1 and B -2 are provided on Figures 1A and 2A; logs of borings HA -1 and HA -2 are provided on Figure 3A. The boring logs present a descriptive summary of the various types of materials encountered in the borings and note the depth at which the materials and /or characteristics of the materials change. To the right of the descriptive summary, the numbers and types of samples taken during the drilling operation are indicated. Farther to the right, N- values are shown graphically, along with natural moisture contents. The terms used to describe the soil and rock encountered in the borings are defined in Tables 1A and 2A. LABORATORY TESTING General The samples obtained from the borings were examined in our laboratory where the physical characteristics of the samples were noted, and the field classifications were modified where necessary. Laboratory testing was limited to natural moisture content determinations in conformance with ASTM D 2216. The results are summarized on Figures 1A through 3A. Al Table 1A GUIDELINES FOR CLASSIFICATION OF SOIL Description of Relative Density for Granular Soil Standard Penetration Resistance Relative Density (N- values) blows per foot very loose 0 - 4 loose 4 - 10 medium dense 10 - 30 dense 30 - 50 very dense over 50 Description of Consistency for Fine - Grained (Cohesive) Soils Standard Penetration Torvane Resistance (N- values) Undrained Shear Consistency blows per foot Strength, tsf very soft 2 less than 0.125 soft 2 -4 0.125 -0.25 medium stiff 4 - 8 0.25 - 0.50 stiff 8 - 15 0.50 - 1.0 very stiff 15 -30 1.0 -2.0 hard over 30 over 2.0 Sandy silt materials that exhibit general properties of granular soils are given relative density description. Grain -Size Classification Modifier for Subclassification Boulders Percentage of 12 - 36 in. Other Material Adjective In Total Sample Cobbles 3 - 12 in. clean • 0 - 2 Gravel trace 2 - 10 1 /4 - in. (fine) 3 /4 - 3 in. (coarse) some 10 - 30 Sand sandy, silty, 30 - 50 No. 200 - No. 40 sieve (fine) clayey, etc. No. 40 - No. 10. sieve (medium) No. 10 - No. 4 sieve (coarse) Silt /Clay - pass No. 200 sieve Table 2A GUIDELINES FOR CLASSIFICATION OF ROCK . RELATIVE ROCK WEATHERING SCALE: Term Field Identification Fresh Crystals are bright. Discontinuities may show some minor surface staining. No discoloration in rock fabric. Slightly Rock mass is generally fresh. Discontinuities are stained and may contain clay. Some discoloration in rock Weathered fabric. Decomposition extends up to 1 in. into rock. Moderately Rock mass is decomposed 50% or less. Significant portions of rock show discoloration and weathering effects. Weathered Crystals are dull and show visible chemical alteration. Discontinuities are stained and may contain secondary mineral deposits. Predominantly Rock mass is more than 50% decomposed. Rock can be excavated with geologist's pick. All discontinuities Decomposed exhibit secondary mineralization. Complete discoloration of rock fabric. Surface of core is friable and usually pitted due to washing out of highly altered minerals by drilling water. Decomposed Rock mass is completely decomposed. Original rock "fabric" may be evident. May be reduced to soil with hand pressure. RELATIVE ROCK HARDNESS SCALE: Hardness Approximate Unconfined Term Designation Field Identification Compressive Strength Extremely RO Can be indented with difficulty by thumbnail. May be < 100 psi Soft moldable or friable with finger pressure. Very R1 Crumbles under firm blows with point of a geology pick. 100 - 1,000 psi Soft Can be peeled by a pocket knife and scratched with fingernail. Soft R2 Can be peeled by a pocket knife with difficulty. Cannot 1,000 - 4,000 psi be scratched with fingernail. Shallow indentation made by firm blow of geology pick. • Medium R3 Can be scratched by knife or pick. Specimen can be 4,000 - 8,000 psi Hard fractured with a single firm blow of hammer /geology • pick. Hard R4 Can be scratched with knife or pick only with difficulty. 8,000 - 16,000 psi Several hard hammer blows required to fracture specimen. Very R5 Cannot be scratched by knife or sharp pick. Specimen > 16,000 psi Hard requires many blows of hammer to fracture or chip. Hammer rebounds after impact. RQD AND ROCK QUALITY: Relation of RQD and Rock Quality Terminology for Planar Surface RQD (Rock Description of Quality Designation), % Rock Quality Bedding Joints and Fractures Spacing 0 - 25 Very Poor Laminated Very Close < 2 in. 25 - 50 Poor Thin Close 2 in. — 12 in. 50 - 75 Fair Medium Moderately Close 12 in. — 36 in. 75 - 90 Good Thick Wide 36 in. — 10 ft 90 - 100 Excellent Massive Very Wide > 10 ft Mi V- U cc STD PENETRATION RESISTANCE o CLASSIFICATION OF MATERIAL a (140 LB WEIGHT, 30 IN. DROP) LL U L o w A BLOWS PER FOOT _ _ _ a 0 MOISTURE CONTENT, o o SURFA ELEVATION 468 ft (±) o 1 50 100 FILL: Medium stiff to stiff, light brown mottled rust SILT; some 1 1 1 -- — — — clay, trace fine - grained sand and scattered fragments of ::�= ■ -- - -- - weathered basalt, 6-in.-thick moderately rooted zone at the • • ground surface • 1 • •• l i - 5— I I I I S -1 I hi, ME 1: - I f — i:� : :- :_ __ I1 11 � - f i 10— 1 1 S -2 I Mum ■ 11 _ i � ■ — ■. ■■ is — — 12.5 � ■ ■ ■ ■ —■ — Medium stiff to stiff, reddish -brown SILT; some clay, trace fine- I:�:::: ■ ■■ _ grained sand (Residual Soil) • ,t ■= �, 15— III I=111 o: : :: — I■ .... ■ — ui. ii. :: :: - 20_ I E- ii: :::E9:E :: S-4 I . I 1 = 25 — + + ++ 25.0 11 11 — + + + + Extremely soft (RO), greenish -gray BASALT; vesicular s 5 :� MI - : : ■■: + + + + predominantly decomposed — + + ++ ••••11•I• l— • •• — + + ++ —I- : - -.::- — + + ++ — ++ + + ••••••• ■■I_ • - 30 — + +++ — + + ++ — - - -- _++++ S -7 I • .( • — + + ++ :� :: 1 ■■ ■■■— 1•_•011 . 35 — + + ++ : IL. :: — + + ++ — + + + + s -8 ■ .4 • do _ - + + ++ . 111 :+ + ++ . _::: — + + ++ 11�.... : ■ ::- —++++ :— :": ::� :■ - 40 — + + ++ 1 — - 1 '2 -IN -OD SPLIT -SPOON SAMPLER ® TORVANE SHEAR 0 0.5 1.0 STRENGTH, TSF (TONS PER FT 1) II 3-IN.-OD THIN - WALLED SAMPLER ® UNDRAINED SHEAR G GRAB SAMPLE OF DRILL CUTTINGS STRENGTH, TSF it * NO RECOVERY B NIX CORE RUN t G, ` R B B -1 — SLOTTED PVC PIPE 1 L , —Liquid Lint Moisture Content 1 V Water Level (date) Plastic lime OCT. 2009 JOB NO. 4935 FIG. 1A cc STD PENETRATION RESISTANCE c� (140-LB WEIGHT, 30-IN. DROP) o CLASSIFICATION OF MATERIAL LL L o w - ® BLOWS PER FOOT a 0 a 0 MOISTURE CONTENT, % w cc 0 0 SURFACE ELEVATION 468 ft (±) o 0 50 100 —40 — + + ++ 1 1 —+ + + + Extremely soft (RO), greenish -gray BASALT; vesicular, S-9 4 I —+ + + + predominantly decomposed — • — — _ + + ++ — ra — + + ++ —■ — + + ++ •• 45 — + + ++ I — + + ++ 1 M•• ■ -v — + + ++ — + + ++ _ + + + + — + + ++ 50 — + + + + —fragments of harder basalt below 50 ft �� • ME= - + + ++ - + + ++ ■, M + + ++ — + + ++ =Mg EINEM — + + ++ — L — + + ++ 55—++++ S-12 I - - + + ++ 4' -514;" — + + ++ — + + + + —soft (R2), moderately weathered basalt below 57.5 ft - + + ++ — + + ++ —+ + + + P — - 1 -- 60 60.1 S-13 = 511 "A — (12/16/2008) 65 1 1 2-IN.-OD SPLIT -SPOON SAMPLER • TORVANE SHEAR 0 0.5 1.0 STRENGTH, TSF (TONS PER FT') D 3-IN.-OD THIN- WALLED SAMPLER ® UNDRAINED SHEAR G GRAB SAMPLE OF DRILL CUTTINGS STRENGTH, TSF NX CORE RUN * NO RECOVERY 1 '- , R_ BORING B -1 (cont.) — SLOTTED PVC PIPE 'Uqoitl Lime V Water Level (date) _ Plb�UmA Moisture Content OCT. 2009 JOB NO. 4935 FIG. 1A STD PENETRATION RESISTANCE o CLASSIFICATION OF MATERIAL ¢ (140 LB WEIGHT, 30-IN. DROP) ,„ ® BLOWS PER FOOT a a o a 0 MOISTURE CONTENT, % w o SURFACE ELEVATION 473 ft ( ±) o u) 0 50 100 ::!∎ • Asphaltic- concrete PAVEMENT (1.5 in.) over crushed rock _ — f ;:'1c: BASE COURSE (34.5 in.) — • 3.0 T Stiff, light brown mottled rust SILT; trace clay and fine - grained S - 1 sand 5— T � I S 1 Ir -__ _ -- f 6.5 (12/16/2008) -- 10- 15- 20 25 30 35 — —40 I 0 0.5 1.0 24N. -OD SPLIT -SPOON SAMPLER • TORVANE SHEAR STRENGTH, TSF (TONS PER FT 1) Il 3-IN.-OD THIN - WALLED SAMPLER ® UNDRAINED SHEAR G GRAB SAMPLE OF DRILL CUTTINGS STRENGTH, TSF * NO RECOVERY NX CORE RUN ', R BORING B -2 1--� I- SLOTTED PVC PIPE Liquid Lime L 1 Moisture Content V Water Level (date) — F%stc Limit • OCT. 2009 JOB NO. 4935 FIG. 2A • • D HA -1 Elev. 476 ft ( ±) D HA -2 Elev. 472 ft (±) FILL: Soft, brown SILT; some fine to coarse, FILL: Medium stiff, brown SILT; trace clay and — angular gravel, trace clay and fine- to coarse- -ne- grained sand J grained sand 1 — 1 — FILL: Medium dense GRAVEL; fine to coarse, FILL: Medium dense GRAVEL; fine to coarse, angular — angular FILL: Soft to medium stiff, reddish - brown, clayey 2 — 2 - SILT; contains gravel-size pieces of basalt ❑ S -1 0 FILL: Medium stiff, rust to olive-brown SILT; trace ❑ W 2 /o C — w = 24 / o = — to some fine- to coarse - grained sand and fine to a 3 coarse, subangular to subrounded gravel, ❑ S -2 0 3 scattered organics w = 23% 0 1 Medium stiff to stiff, reddish - brown, clayey SILT; — olive brown below 3 ft contains gravel -size pieces of basalt 4 ❑ S -3 4 wet below 4 ft ❑ S -2 FILL: Soft, dark brown SILT; trace fine - grained w = 28% — w = 27% — sand, trace to some organics 5 - wet, organic odor below 5 ft 5 - Bottom of hand auger at 5 ft (1/5/09) — Light groundwater seepage below 4 ft 6 ❑ S -4 Bottom of hand auger at 6 ft (1/5/09) w = 42 Light groundwater seepage below 5 ft LEGEND ❑ = GRAB SAMPLE w = NATURAL MOISTURE CONTENT GROUND SURFACE ELEVATIONS FROM SITE PLAN, FIGURE 2. GR 0 HAND -AUGER BORING LOGS OCT. 2009 JOB NO. 4935 FIG. 3A • APPENDIX B Site- Specific Seismic Hazard Study APPENDIX B SITE - SPECIFIC SEISMIC HAZARD STUDY General GRI has completed a site - specific seismic hazard study for the existing City of Tigard 10 -MG reservoir at the location shown on Figure 1. Our work was based on the potential for regional and local seismic activity as described in the existing scientific literature and on the subsurface conditions at the site interpreted from subsurface explorations. Specifically, our work included the following tasks: 1) A detailed review of the literature, including published papers, maps, open -file reports, seismic histories and catalogs, works in progress, and other sources of information regarding the tectonic setting, regional and local geology, and historical seismic activity that might have a significant effect on the site. 2) Compilation, examination, and evaluation of existing subsurface data gathered at and in the vicinity of the site, including classification and laboratory analyses of soil samples. This information was used to prepare a generalized subsurface profile for the site. 3) Identification of potential seismic events (earthquakes) appropriate for the site and characterization of those events in terms of a series of generalized design events. 4) Office studies, based on the generalized subsurface profile and the generalized design earthquakes, resulting in conclusions and recommendations concerning: a) specific seismic events that may have a significant effect on the site, b) the potential for seismic energy amplification at the site, and c) site - specific acceleration response spectrum for a design earthquake. This appendix describes the work accomplished and summarizes our conclusions. Geologic Setting The general area occupied by the project site is mantled by up to about 10 ft of silt or silt fill. Locally, these soils consist of silt with a trace of clay and fine - grained sand. These surficial materials are underlain by flood basalts of the Columbia River Basalt Group (Madin, 2004). The boundary between the soil and underlying basalt is unconformable, indicating that a considerable period of time elapsed between the solidification of the last of the basalt flows and the deposition of the overlying sedimentary materials (Schlicker and Deacon, 1967). During this period of time, the upper portions of the basalt were subjected to surficial processes, including erosion, mass wasting, and chemical and physical degradation. These processes resulted in variable weathering of the upper portions of the basalt. The upper severely weathered portion of the basalt is decomposed to the consistency of hard residual soil. The underlying predominantly decomposed rock extends to a depth of about 60 ft below the existing ground surface, where it is underlain by soft, moderately weathered basalt. 6 * ;R1 , I `. tL . B -1 On a regional scale, the site lies in the Tualatin Valley at the northern end of the Willamette Valley, a broad, gently deformed, north- south - trending topographic feature separating the Coast Range to the west from the Cascade Mountains to the east. The valley lies approximately 150 km inland from the surface expression of the Cascadia Subduction Zone (CSZ), an active plate boundary along which remnants of the Farallon Plate (the Gorda, Juan de Fuca and Explorer plates) are being subducted beneath the western edge of the North American continent. The configuration of these plates and the location, extent, and geometry of the surface expression of the subduction zone are shown schematically on the Tectonic Setting Summary, Figure 1 B(a). The subduction zone is a broad, eastward- dipping zone of contact between the upper portion of the subducting slabs of the Gorda, Juan de Fuca, and Explorer plates and the over - riding North American Plate, as shown schematically on Figure 1 B(b). On a local scale, the site is located on the east flank of the Bull Mountain upland, which is underlain by Columbia River Basalt. The Bull Mountain upland forms a portion of the southeastern margin of the Tualatin Basin, a large, well- defined, northwest- trending syncline bounded by high - angle, northwest - trending, right - lateral strike -slip faults generally considered to be seismogenic. The distribution of these faults relative to the site is shown on the Regional Geologic Map and Local Fault Map, Figures 2B and 3B, respectively. Information regarding the precise location and extent of discrete faults within the basin is lacking, although a limited number of intrabasin faults have been mapped on the basis of stratigraphic offsets and geophysical evidence. The relationship between specific earthquakes and individual faults in the area is not well understood, since few of the faults in the area are expressed clearly at the ground surface. Other faults may be present within the basin, but clear stratigraphic evidence regarding their location and extent is not presently available. Because of the proximity of the site to the CSZ and its location within the fault - bounded Tualatin Basin, three distinctly different sources of seismic activity contribute to the potential for the occurrence of damaging earthquakes at the site. Each of these sources is considered capable of producing damaging earthquakes. Two of these sources are associated with deep - seated tectonic activity related to the subduction zone; the third is associated with movement on the local, relatively shallow structures within and adjacent to the Tualatin Basin. Subsurface Conditions The site vicinity is immediately underlain by silt or fill to a depth of about 10 ft. The silt and fill are underlain by residual soil and predominantly decomposed basalt. In our experience, the thickness of this severe weathering is quite variable from place to place, and, based on boring B -1, extends to a depth of about 57.5 ft below the existing ground surface. This zone of decomposed basalt is underlain by extensively fractured, less- weathered basalt. The floor slab of the existing reservoir is at about elevation 440 ft, and the proposed lowest level of the pump station will be about 430 ft. Based on materials and conditions disclosed by our boring, the pump station and reservoir will be underlain by decomposed rock grading to harder, less weathered rock. • Seismicity The geologic and seismologic information available for identifying the potential seismicity at the site is incomplete, and large uncertainties are associated with any estimates of the probable magnitude, location, and frequency of occurrence of earthquakes that might affect the site. The information that is available ' B -2 indicates that the potential seismic sources that may affect the site can be grouped into three independent categories: subduction zone events related to sudden slip between the upper surface of the Juan de Fuca plate and the lower surface of the North American plate, subcrustal events - related to deformation and volume changes within the subducted mass of the Juan de Fuca plate, and local crustal events associated with movement on shallow, local faults within and adjacent to the Tualatin Basin. Based on our review of currently available information, we have developed generalized design earthquakes for each of these categories. The design earthquakes are characterized by three important properties: size, location relative to the subject site, and the peak horizontal bedrock accelerations produced by the event. In this study, size is expressed in Richter (local) magnitude (MI ), surface wave magnitude (Ms), Japanese Meteorological Association magnitude (Mir,,,), or moment magnitude (Mw); location is expressed as epicentral or focal distance, measured radially from the subject site in kilometers; and peak horizontal bedrock accelerations are expressed in gravities (1 g = 32.2 ft/sec' = 980.6 cm /sec'). Subduction Zone Event. There have not been any interplate earthquakes on the CSZ in the historical record of the Pacific Northwest; however, geological studies suggest that great interplate megathrust earthquakes on the CSZ have repeatedly occurred in the past 7,000 years (Atwater and others, 1995; Clague and others, 1997; Goldfinger, 2003; and Kelsey and others, 2005). Geodetic studies (Hyndman and Wang, 1995; Savage and others, 2000) indicate rate of strain accumulation consistent with the assumption that the CSZ is locked beneath offshore northern California, Oregon, Washington, and southern British Columbia (Fluck and others, 1997; Wang and others, 2001). Numerous geological and geophysical studies suggest the CSZ may be segmented (Hughes and Carr, 1980; Weaver and Michaelson, 1985; Guffanti and Weaver, 1988; Goldfinger, 1994; Kelsey and others, 1994; Mitchell and others, 1994; Personius, 1995; Nelson and Personius, 1996; Witter, 1999), but the most recent studies suggest that for the last great earthquake in 1700, most of the subduction zone ruptured in a single M 9 earthquake (Satake and others, 1996; Atwater and Hemphill - Haley, 1997; Clague and others., 2000). Published estimates of the probable maximum size of subduction zone events range from moment magnitude Mw 8.3 to >9.0. Numerous detailed studies of coastal subsidence, tsunamis, and turbidites yield a wide range of recurrence intervals, but the most complete records ( >4,000 years) indicate average intervals of 350 to 600 years between great earthquakes on the CSZ (Adams, 1990; Atwater and Hemphill - Haley, 1997; Witter, 1999; Clague, and others, 2000; Goldfinger and others, 2003; Kelsey and others, 2002; Kelsey and others, 2005; Witter and others, 1997). We have chosen to represent the subduction zone event deterministically by a design earthquake of Mw 9.0 at a focal depth of 15 km and an epicentral distance of 100 km. This corresponds to a sudden rupture of the whole length of the Juan de Fuca -North American plate interface, assuming the lock zone is located at the coastline, due west of Tigard. Based on an average of the attenuation relationships published by Youngs and others (1997), Atkinson and Boore (2003), and Gregor, and others (2002), a subduction zone earthquake of this size and location would result in a peak horizontal bedrock acceleration of approximately 0.13 g at this site. Subcrustal Event. There is no historic earthquake record of subcrustal, intraslab earthquakes in Oregon. Although both the Puget Sound and northern California region have experienced many of these earthquakes in historic times, Wong (2005) hypothesizes that due to subduction zone geometry, geophysical conditions and local geology, Oregon may not be subject to intraslab earthquakes. In the Puget Sound area, these moderate to large earthquakes are deep (40 to 60 km) and over 200 km from the deformation front of the subduction zone. Offshore, along the northern California coast, the earthquakes are shallower (up to 40 km) and located along the deformation front. Estimates of the probable size, 4 '` B-3 location, and frequency of subcrustal events in Oregon are generally based on comparisons of the CSZ with active convergent plate margins in other parts of the world and on the historical seismic record for the region surrounding Puget Sound, where significant events known to have occurred within the subducting Juan de Fuca plate have been recorded. Published estimates of the probable maximum size of these events range from moment magnitude Mw 7.0 to 7.5. The 1949, 1965, and 2001 documented subcrustal earthquakes in the Puget Sound area correspond to Mw 7.1, 6.5, and 6.8, respectively. Published information regarding the location and geometry of the subducting zone indicates that a focal depth of 50 km and an epicentral distance of 40 km from the site are probable (Weaver and Shedlock, 1989). We have chosen to represent the subcrustal event by a design earthquake of magnitude Mw 7.0 at a focal depth of 50 km and an epicentral distance of 40 km. As with the subduction zone event, this choice is based on an estimate of the capability of the source region rather than on a probabilistic analysis of a historical record of events of this type. Based on an average of attenuation relationships published by Youngs and others (1997), and Atkinson and Boore (1997), a subcrustal event of this size would result in a peak horizontal bedrock acceleration of approximately 0.15 g at the site. Similar to the subduction zone earthquake, this acceleration is based on a deterministic estimate of the source rather than a probabilistically based design value. Local Crustal Event. Sudden crustal movements along relatively shallow, local faults in the Tigard area, although rare, have been responsible for local crustal earthquakes. The precise relationship between specific earthquakes and individual faults is not well understood, since few of the faults in the area are expressed at the ground surface, and the foci of the observed earthquakes have not been located with precision. The history of local seismic activity is commonly used as a basis for determining the size and frequency to be expected of local crustal events. Although the historical record of local earthquakes is relatively short (the earliest reported seismic event in the area occurred in 1841), it can serve as a guide for estimating the potential for seismic activity in the area. Based on fault mapping conducted by the U.S. Geological Survey (USGS) (2002), the Canby Molalla fault zone passes approximately 1 mile to the east. Assuming the fault is located 1 km from the site and has a characteristic earthquake magnitude of Mw = 6.5, a crustal earthquake of this size would result in a peak horizontal bedrock acceleration of approximately 0.45 g. This acceleration is based on an average of the following NGA ground motion relations developed by the Pacific Earthquake Engineering Research (PEER) in 2006: Boore and Atkinson, Campbell and Bozorgnia, and Chiou and Youngs. It should be noted that although the Canby Molalla fault is considered Holocene active by the USGS (Personius, 2003), the fault is not considered in the 2002 USGS probabilistic seismic hazard assessment (PSHA). Summary of Earthquake Sources In summary, three distinctly different types of earthquakes may contribute to the seismicity of the project area. Published attenuation relationships were used to estimate the peak bedrock accelerations at the site. The parameters for each deterministic estimate are summarized in the following table. These deterministic parameters are provided as required by the Oregon Structural Specialty Code, but are not intended for design purposes. „< .,� B -4 Average Earthquake Attenuation Relationships Epicentral Focal Peak Bedrock Peak Bedrock Source for Target Spectra Magnitude, Mw Distance, km Depth, km Acceleration, g Acceleration, g Subduction Zone Youngs, et al., 1997 9.0 100 15 0.14 Atkinson and Boore, 2003 9.0 100 15 0.06 0.13 Gregor, et al., 2002 9.0 100 15 0.19 Subcrustal Youngs, et al., 1997 7.0 40 50 0.22 0.15 Atkinson and Boore, 1997 7.0 40 NA 0.07 Local Crustal Campbell and Bozorgnia, 2007 6.5 1 NA 0.47 Chiou and Youngs, 2006 6.5 1 NA 0.52 0.45 Boore and Atkinson, 2007 6.5 1 NA 0.35 Probabilistic Considerations and Code Spectra While three different types of earthquake sources exist in the Pacific Northwest, the likelihood of each type of earthquake occurring is not equal. The probability of an earthquake of a specific magnitude occurring at a given location is commonly expressed by its return period, i.e., the average length of time between successive occurrences of an earthquake of that size or larger at that location. These expected earthquake recurrences are expressed as a probability of exceedance during a specified time period (50 years, for example), or design life. Historically, building codes have required structural design for ground acceleration associated with an earthquake that has a 10 probability of exceedance in 50 years, which corresponds to an earthquake recurrence interval of 475 years. The IBC re- evaluated this design level, and identified the new design spectrum by using two- thirds of the Maximum Considered Earthquake (MCE) ground motion. The MCE earthquake is defined as an earthquake with a 2% probability of exceedance in 50 years (return period of about 2,500 years), except where subject to deterministic limitations (Leyendecker, et al., 2000). Using the MCE is intended to reduce the risk of building collapse in regions where the 2,500 -year recurrence interval earthquake is significantly larger than the previous 475 -year recurrence interval design earthquake. The IBC design response spectrum is two- thirds of the MCE response spectrum, which adjusts the design spectrum to a more traditional "life safety" level. The ground motion parameters for the 2007 Oregon Structural Specialty Code (2006 IBC) are based on the 2002 USGS PSHA. The USGS mapping identifies the likelihood of movement for all identified seismic sources (i.e., local crustal, subcrustal, and subduction zone earthquakes) and probabilistically determines a uniform hazard curve. The IBC design methodology uses two spectral response coefficients, Ss and Si, corresponding to periods of 0.2 and 0.1 seconds to develop the design level spectrum. The Ss and Si coefficients for the site are 0.92, and 0.33 g, respectively. Estimated Site Response The effect of an earthquake on the site is related to the seismic energy delivered by the earthquake and to the thickness and material characteristics of soil overlying bedrock at the site. Based on our subsurface explorations at the site, the existing tank and proposed pump station are underlain by at least 25 ft of decomposed rock, with the consistency of hard soil, overlying hard basalt. Because the reservoir and pump station are both founded in weathered rock and within 25 to 35 ft of hard rock, estimation of site amplification is not appropriate using conventional site response models. For the purpose of this pump station and reservoir retrofit design, site response is best estimated using the code -based site amplification factors to adjust the rock response spectrum. Based on these subsurface conditions, we recommend defining the site as IBC Site Class C, or a soft rock site. B -5 Conclusions The IBC -based 0.2- and 1.0 -sec spectral response accelerations (Ss, S1) for the site are approximately 0.92 and 0.33 g, respectively. Due to the presence of decomposed rock overlying hard rock at a shallow depth, for the design of the proposed pump station and existing reservoir, we recommend using the IBC design spectrum for Site Class C (soft rock) at a damping ratio of 5 %. To calculate the response spectrum at a damping ratio of 0.5% for sloshing, the IBC design spectrum for Site Class C can be multiplied by a factor of 1.5. References Abrahamson, N.A., and Silva, W.J., 1997, Empirical response spectral attenuation relations for shallow crustal earthquakes, v. 68, no. 1, pp.94 -109 Adams, J., 1984, Active deformation of the Pacific Northwest continental margin: Tectonics, v. 3, p. 449 -472. , 1990, Paleoseismicity of the Cascadia subduction zone: Evidence from turbidites off the Oregon - Washington margin: Tectonics, v. 9, no. 4, p. 569 -583. Army Corps of Engineers, 2000, TI 809 -04 Seismic design for buildings, Washington, D.C. Atkinson, G.M., and Boore, D.M., 1997, Stochastic point- source modeling of ground motions in the Cascadia region: Seismological Research Letters, v. 68, no. 1, pp. 74 -85. Atwater, B.F., 1987, Evidence for great Holocene earthquakes along the outer coast of Washington State: Science, v. 236, p. 942- 944. , 1988, Geologic studies for seismic zonation of the Puget Lowland: U.S. Geological Survey Open -File Report, v. 25, p. 120 -133. Atwater, B.F., and Hemphill - Haley, E., 1997, Recurrence intervals for great earthquakes of the past 3,500 years at northeastern Willapa Bay, Washington: U.S. Geological Survey Professional Paper 1576, 108 p. Beeson, M.H., Tolan, T.L., and Madin, I.P, 1991, Geologic map of the Portland quadrangle, Clackamas, Multnomah, and Washington counties, Oregon, and Clark County, Washington: Oregon Department of Geology and Mineral Industries, Geologic Map Series GMS -75, scale 1;24,000. Boore, D.M., Joyner, W.B., and Fumal, T.E., 1997, Equations for estimating horizontal response spectra and peak acceleration from western North American earthquakes: a summary of recent work: Seismological Research Letters, v. 68, no. 1, p. 128- . 153. Clague, J.J., 1997, Evidence for large earthquakes at the Cascadia subduction zone: Reviews of Geophysics, v. 35, no. 4, p. 439- 460. Clague, J.J., Atwater, B.F., Wang, K., Wang, Y., and Wong, I., 2000, Penrose conference report-Great Cascadia earthquake tricentennial: GSA Today, v. 10, no. 11, p. 14 -15. Couch, R.W., Johnson, S. and Gallagher, J., 1968, The Portland earthquake of May 13, 1968, and earthquake energy release in the Portland area: The Ore Bin (Oregon Department of Geology and Mineral Industries), v. 30, no. 10, p. 185 -190. Dragert, H., Hyndman, R.D., Rogers, G.C., and Wang, K., 1994, Current deformations and the width of the seismogenic zone of the northern Cascade subduction thrust: Journal of Geophysical Research, vol. 99, pp. 653 -668. Fluck, P., Hyndman, R.D., and Wang, K., 1997, Three - dimensional dislocation model for great earthquakes of the Cascadia subduction zone: Journal of Geophysical Research, v. 102, no. B9, p. 20,539- 20,550. Geomatrix Consultants Final report, seismic design mapping, state of Oregon, project no. 2422; prepared for Oregon Department of Transportation. Goldfinger, C., 1994, Active deformation of the Cascadia Forearc- Implications for great earthquake potential in Oregon and Washington: Oregon State University, unpublished Ph.D. dissertation, 246 p. Goldfinger, C., 2003, Great earthquakes in Cascadia: a who dunnit success story: presentation at 2003 EERI national conference, Portland, Oregon. Guffanti, M., and Weaver, C.S., 1988, Distribution of Late Cenozoic volcanic vents in the Cascade Range - Volcanic arc segmentation and regional tectonic considerations: Journal of Geophysical Research, v. 93, no. B6, p. 6513 -6529. Hughes, J.M., and Carr, M.J., 1980, Segmentation of the Cascade volcanic chain: Geology, v. 8, p. 15 -17. B -6 • Hyndman, R.D., and Wang, K., 1995, The rupture zone of Cascadia great earthquakes from current deformation and the thermal regime: Journal of Geophysical Research, v. 100, no. B11, p. 22,133 - 22,154. International Code Council, 2003, International building code: Building Officials and Code Administrators International, Inc., International Conference of Building Officials, Southern Building Code Congress International. Kelsey, H.M., and Bockheim, J.G., 1994, Coastal landscape evolution as a function of eustasy and surface uplift rate, Cascadia margin, southern Oregon: Geological Society of America Bulletin, v. 106, p. 840 -854. Kelsey, H.M., Witter, R.C., and Hemphill - Haley, E, 2002, PI.-boundary earthquakes and tsunamis of the past 5500 yr, Sixes River estuary, southern Oregon: Geological Society of America Bulletin, v. 114, no. 3, p. 298 -314. Kelsey, H.M., Nelson, A.R., Hemphill - Haley, E., Witter, R.C., 2005, Tsunami history of an Oregon coastal lake reveals a 4600 yr record of great earthquakes on the Cascadia subduction zone: GSA Bulletin, v. 117 p 1009 -1032. Mabey, M.A. and Madin, I.P., 1995, Down -hole and seismic cone penetrometer shear -wave velocity measurements for the Portland metropolitan area, 1993 and 1994: Oregon Department of Geology and Mineral Industries Open -File Report 0- 95-7. Madin, I.P., 2004, Preliminary Digital Geologic Compilation Map of the Portland Urban Area, Oregon: Oregon Department of Geology and Mineral Industries, Open File Report 0 -04 -2. Mitchell, C.E. Vincent, R, Weldon, R.J., III, and Richards, M.A., 1994, Present -day vertical deformation of the Cascadia margin, Pacific Northwest, United States: Journal of Geophysical Research, v. 99, no. B6, p. 12,257- 12,277. Nelson, A.R., and Personius, S.F., 1996, Great -earthquake potential in Oregon and Washington -An overview of recent coastal geologic studies and their bearing on segmentation of Holocene ruptures, central Cascadia subduction zone, in Rogers, A.M., Walsh, T.J., Kockelman, W.J., and Priest, G.R., eds., Assessing earthquake hazards and reducing risk in the Pacific Northwest: U.S. Geological Survey Professional Paper 1560, v. 1, p. 91 -114. Personius, S.F., 1995, Late Quaternary stream incision and uplift in the forearc of the Cascadia subduction zone, western Oregon: Journal of Geophysical Research, v. 100, no. B10, p. 20,193- 20,210. Personius, S., Dart, R., Bradley, L., and Haller, K., 2003 Map of Quaternary Faults and Folds in Oregon, US Geological Survey, Open File Report OFR 03 -095, version 1.1. Peterson, C.D., and Darienzo, M.E., 1989, Discrimination of flood, storm and tectonic forcing of marsh burial events from Alsea Bay, Oregon: Final (unpublished) Report to the National Earthquake Hazards Reduction Program, p. 1 -33. , 1991, Episodic tectonic subsidence of late Holocene salt marshes, northern Oregon coast, central Cascadia margin, USA: Tectonics, v. 8. Sadigh, K., Chang, C. -Y., Egan, J.A., Makdisi, F., Youngs, R.R., 1997, Attenuation relationships for shallow crustal earthquakes based on California strong motion data: Seismological Research Letters, V.68, No.1, pp. 180 -189. Satake, K., Shimazaki, K., Tsuji, Y., and Ueda, K., 1996, Time and size of a giant earthquake in Cascadia inferred from Japanese tsunami records of January 1700: Nature, V.379, pp. 246 -249, 18 January. Satake, K., Wang, K., and Atwater, B.F., 2003, Fault slip and seismic moment of the 1700 Cascadia earthquake inferred from Japanese tsunami descriptions: Journal of Geophysical Research, v. 108, no. 11, 17 p. Savage, J.C., Svarc, J.L., Prescott, W.H., and Murray, M.H., 2000, Deformation across the forearc of the Cascadia subduction zone at Cape Blanco, Oregon: Journal of Geophysical Research, v. 105, no. B2, p. 3095 -3102. Schlicker, H.G., and Deacon, R.J., 1967, Engineering Geology of the Tualatin Valley Region, Oregon: Oregon Department of Geology and Mineral Industries, Bulletin B -60. U.S. Geological Survey, 1996, Probabilistic hazard lookup by latitude, longitude, accessed 9/18/06, from USGS website: http://eqint.cr.usgs.gov/eq-men/html/lookup-interp-06.html U.S. Geological Survey, 2006, Quaternary fault and fold database for the United States, accessed 9/22/06, from USGS web site: http // earthquakes .usgs.gov /regional /gfaults/ Walker, G.W., and MacLeod, N.S., 1991, Geologic map of Oregon: U.S. Geological Survey, scale 1:500,000. Wang, Y., He, J., Dragert, H., and James, T.S., 2001, Three - dimensional viscoelastic interseismic deformation model for the Cascadia subduction zone: Earth, Planets and Space, v. 53, p. 295 -306. Weaver, C.S., and Shedlock, K.M., 1989, Potential subduction, probable intraplate and known crustal earthquake source areas in the Cascadia Subduction Zone: U.S. Geological Survey Open -File Report 89 -465, p. 11 -26. Weaver, C.S., and Michaelson, C.A., 1985, Seismicity and volcanism in the Pacific Northwest- Evidence for the segmentation of the Juan de Fuca Pl.: Geophysical Research Letters, v. 12, no. 4, p. 215 -218. Wells, D.L., and Coppersmith, K.J., 1994, New empirical relationships among magnitude, rupture length, rupture width, rupture area, and surface displacement: Bulletin of the Seismological Society of America, v. 84, no. 4, p. 974 -1002. ;� .:� B -7 I , Witter, R.C., 1999, Late Holocene Paleoseismicity, tsunamis and relative sea -level changes along the south - central Cascadia subduction zone, southern Oregon: University of Oregon, unpublished Ph.D. dissertation, 178 p. Witter, R.C., Kelsey, H.M., and Hemphill - Haley, E., 1997, A paleoseismic history of the south - central Cascadia subduction zone — Assessing earthquake recurrence intervals and upper -pl. deformation over the past 6600 years at the Coquille River Estuary, southern Oregon: Technical report to U.S. Geological Survey, under Contract 1434- HQ -97-GR -03036, 54 p. Wong, I., Silva, W., Bott, J., Wright, D., Thomas, P., Gregor, N., Li, S., Mabey, M., Sojourner, A., and Wang, Y., 2000, Earthquake scenario and probabilistic ground shaking maps for the Portland, Oregon Metropolitan Area. Portland Hills Fault M6.8 earthquake, peak horizontal acceleration (g) at the ground surface: Oregon Department of Geology and Mineral Industries, Interpretive Map Series IMS -15. Wong, I., Silva, W., Bott, J., Wright, D., Thomas, P., Gregor, N., Li, S., Mabey, M., Sojourner, A., and Wang, Y., 2000, Earthquake scenario and probabilistic ground shaking map for the Portland, Oregon Metropolitan Area: Oregon Department of Geology and Mineral Industries, Interpretive Map Series IMS -16. Wong, I., 2005, Low potential for large intraslab earthquakes in the central Cascadia Subduction Zone: Bulletin of the Seismological Society of America, vol. 95, no. 5. Youngs, R.R., Chiou, S.J., Silva, W.J. and Humphrey, J.R., 1997, Strong ground motion attenuation relationships for subduction zone earthquakes: Seismological Research Letters, vol. 68, no. 1, pp. 58 -73. Youngs, R.R., and Coppersmith, K.J., 1989, Attenuation relationships for evaluation of seismic hazards from large subduction zone earthquakes: U.S. Geological Survey Open File Report 89 -465, pp. 42 -50. a c � r s 4.0.1 • u 1 w B -8 APPENDIX C Geotechnical Report by Northwest Testing Laboratories (April 21, 1976) • r Soils and Foundation Investigation Tigard Water District Proposed Reservoir L Bull Mountain, Oregon J t -'cr .fSU, ,.,: Yalta, f 25�i i , ,e,-;e5; .:Ygiii 1% : '",2.::, ;: i i 1. If9 Pal I , D 4115 N. Mississippi Ave. - Portland, Oregon 97217 288 -7086 NORTHWEST TESTING LABORATORIES 4115 N. MISSISSIPPI AVENUE PORTLAND. OREGON 97217 CONSTRUCTION INSPECTION NONDESTRUCTIVE TESTING MATERIALS INSPECTION WELDING CERTIFICATION CHEMICAL ANALYSIS April 21, 1976 SO.L TESTING ►HY3ICAL TESTING ASSAYING Tigard Woter District 8841 S.W. Commercial Street Tigard, Oregon 97223 Attention: Mr. Robert Santee Re: Soils and Foundation Investigation Proposed Reservoir Bull Mountain, Oregon Gentlemen: At your request we have performed a soils and foundation investigation at the site of your proposed reservoir on Bull Mountain, Oregon. We present herewith a report of our findings, conclusions and recommendations. Site Description The proposed reservoir site is located on the northeast corner of S. W. 125th Avenue and Bull Mountain Road, west of Tigard, Oregon. The site slopes gently in a generally northern direction with a total relief of 20 ft. The 2.42 acre site is now utilized as a filbert orchard. Subsurface Exploration Five test borings, locations of whi ch are shown in Fig. 1, attached, were made on April 12, and 13, 1976 with a truck- mounted power auger using 8 -in. hollow flight augers. Samples were taken at 2.5 ft intervals up to 15 ft in depth and at 5 ft intervals thereafter with a 2 -in. O.D. split -spoon sampler, in conjunction with the Standard Penetration Test. The Standard Penetration Test is performed by driving a 2 -in. O.D. split -spoon sampler into the undisturbed formation at the bottom of the boring with repeated blows of a 140-lb pin- guided hammer falling 30 -in. The number of blows required to drive the sampler a given distance is a measure of the soil consistency. Samples were identified in the field, placed in sealed containers and transported - 2 - Tigard Water District Soils and Foundation Investigation to the laboratory for further classification and testing. Laboratory Tests Laboratory tests were performed on representative samples. These included natural water content, Atterberg Limits and particle size distribution. Results of tests are summarized in Table 1. Geology and Soils Units encountered during the course of this investigation consist of the Columbia River Basalts overlain by a series of silts termed locally the Upland Silts. A brief description of the encountered units is as follows: 1. Upland Silts (ML) A 12.5 ft to 15 ft thick unit of soft to moderately firm, Tight -brown clayey silt, merging to a rust brown, clayey silt with basalt fragments at depth and topped by a weathered crust of dark brown, clayey silt. This series is found throughout the Tualatin Valley on topographic highs, overlying the basalt. 2. Columbia River Basalts ,4 unit several hundreds of feet thick of dense gray basalt topped by a layer of highly weathered basalt. At this site the basalt is overlain by a 5 ft to 10 ft thick layer of residual silty sand with rock fragments. Test boring logs have been combined with topographic information to develop geologic cross sections (Figs. 2 and 3). - 3 - Tigard Water District Soils and Foundation Investigation Groundwater No groundwaterwas encountered during the course of this investigation; published hydrographs of the area show groundwater to be several hundred feet below surface level. Proposed Construction We understand construction plans call for a 10 million gallon reinforced concrete water reservoir to be located in the center of the proposed site. The tank will measure 221 ft in diameter and be founded directly on the underlying basalts, approximately 20 ft to 30 ft below present surface level. Conclusions and Recommendations From our investigation of the proposed reservoir site we draw the following principal con - clusions: 1. The upland silts may be used to support Tight or settlement tolerant structures; they should not, however, be used to support the main structure nor its contents. Bearing pressures of 3000 psf may be used in the Upland Silt. 2. The weathered basalt should be used as the bearing horizon. Footings placed in the weathered basalt basalt can be designed for contact pressures of 15,000 psf. 3. Excavations of up to 10 ft into the basalt will be necessary in some areas of the reservoir site. 4. If the excavation can be controlled to within 3 ft of the structure line, lateral earth pressures on the reservoir wall may be calculated - 4 - Tigard Water District Soils and Foundation Investigation 4. on the basis of equivalent fluid pressure of 30 pcf (for level backfill). -- 5. Asphalt access roads and parking pads may be designed on the overlying silts for a CBR of 10. 6. Because the silts are sensitive to disturbance in presence of excess i moisture, great care should be taken in earthwork operations and site preparation during the rainy season. We shall be pleased to assist you further in the completion of the design phase of the project and in resolving any unforeseen difficulties during the construction phase. Report Number 160581 Respectfully submitted, NORTHWEST TESTING LABORATORIES y- Charles R. Lane, Manager 12 i '° Z 1 % ' P 4 � 07-'7, a - ;.� ` Neil H- `fwelker • pr i 4236 OREGON / i TIGARD WATER DISTRICT Natural Moisture Boring Sample Depth Content, Liquid Plastic Plastic Number Number In Feet Percent Limit Limit Index B -5 1 2.5 - 4.0 22.2 37 24 13 4 10.0 - 11.5 20.8 53 24 29 6 15.0 - 16.5 27.7 50 31 19 8 25.0 - 26.5 32.5 52 27 25 * * * * * * * * * * * * ** PARTICLE SIZE - PERCENT RETAINED Boring Sample Depth Number Number In Feet # 4 # 8 # 16 #40 # 100 0 200 - #200 B -5 1 2.5 - 4.0 0 0.1 1.3 3.2 10.4 18.9 66.0 4 10.0 -11.5 0 0 0.6 9.6 22.2 16.5 51.0 6 15.0 -16.5 0 0.3 6.7 15.5 24.1 18.4 35.0 8 25.0 -26.5 0 0 3.5 15.7 32.3 16.9 31.5 TABLE 1 . .. .. . .... / / 1 4 --___-------1•B' 6/ I / / / 47 ,---- ' N .•.A... 1 3 , • Y? C--" 1 Z. -- • '_ ! - 'la, B-1 _, - - ' B4 1-:,-- r - \ ! 4 4 , I ! I \ I I \ '.. . . ------- .\../../. 1E.k.)1...\-,_ 1--40kik--171=.\ I!) 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VI CI - O \ - 9 - ° J . a ' v usck "; . �2 �{. 13 • n . ,� \7aNA ws`DNraCfxS. - 71 - q:37 S" fl �-'�- ;�- " -- �= i .-uq �p .-- 7 ,' \ s,r ,,, � h — --�— — . ass `� — _i -i '•t t • o. �a _ —. — — — z.�-� rirob j S ss�N T r'tl7g — • 4 Tt•'t8 • • Emery a Sons PO Box 4109 Construction, Inc. • Salem, OR 97302 r` General Contractors Ph : (503)588 -7576 Underground Specialists Fax : (503)375 -6148 www.emeryandsons.com TRANSMITTAL OF CONTRACTOR'S SUBMITTAL (ATTACH TO EACH SUBMITTAL) DATE: November 30, 2009 TO: Murray Smith & Associates Submittal No.: 035 Attn: Brendan V. O'Sullivan r, New Submittal f" Resubmittal 121 SW Salmon Suite 900 Project: Sherwood Water Supply Improvs Portland, OR 97204 -2919 Project No.: 09 -13385 FROM: Emery & Sons Construction, Inc. Spec. Section No.: 15102 Contractor (Cover only one section with each transmittal) P.O. Box 4109 Stayton, OR 97302 Description: Butterfly Valves Schedule Date of Submittal: November 30, 2009 SUBMITTAL TYPE: r Shop drawings r Sample r Informational The following items are hereby submitted: Number of Description of Item Submitted Spec. and Contains Variations Copies (Type, Size, Model Number, Etc.) Para. No. to Contract Butterfly Valves 15102 Contractor hereby certifies that (i) Contractor has complied with the requirements of Contract Documents in preparation, review, and submission of designated submittal and (ii) the submittal is complete and in accordance with the Contract Documents and requirements of laws and regulations and governing agencies. By: Contractor (Authorized Signature) • GCB: OR - 312 1 CA - 920395 1 WA - EMERYSC11 OPR 1 NV - 0071718 • C 4 \, \ 130°0 1 126 122°W TIGARD s % tk b 4 / 52 °N. Coastline Coastal Cascades e 3 NORTH AMERICA Range °! / PLATE 0 British . _ Co lumbia . 4 t 1 • r Cf t220 121.5 121,5 121.0 127.5 123.0 j i 122.6 ("r / ■ E R 1 0 _ LONOltUt EXPLORER \ E , ® 1 I PLATE a Vancouver – I C 0. g9TANCE N� Crustal faults l y vs ' i. d (dj v l� \\ i• ` 10. 30. 50. 70. 90. 110. 1 3 0 . 15( 170. 190. 210. 230 250. 270. 290. r Fa � d I .. 0 46 ° — 1 1 I 1 1 1 1 1 • V 11 1 1 L—°' I f o �� • ° . e I o Seattle lo. o e ° 0 ` . .I , . '' : M. r : • :... • a 01 0 ° 460 .°' Nort America Plate D G Washington — ° ' e o 6 - 0 A ' -- _ PI6te 1 ' Crustal 50. D m/ JUAN DE FUCA n m • 70. - Interface J aelsmlelty p _ 70. 1 / PLATE p Portlande _ r!a' 0eF > > Intraslab Ic N L �. - I hquakes 8494 - i t - -T , 150. PACIFIC PLATE 8 - - - - - - - - 121.5 124.0 123.8 123.0 1225 122.0 121.5 P 1 / GORDA A - LoNOITUDE 1:3 PLATE Califomia DEFORMATION BI FAST -WEST CROSS - SECTION 1HR000H W'ESI ERN OREGON AT THE LATITUDE OF SHERWOOD, SHOWING THE SEISMIC SOURCES CONSIDERED IN THE SITE- SPECIFIC SEISMIC HAZARD SIUD1' (MODIFIED FROM • 0 200 km Mendocino Fa ' 1, 4U' GEONTATRIZ, 1993) Al TECTONIC MAP OF PACIFIC NORTHWEST, SHOWING ORIENTATION AND EVENT OF CASCADIA SLIBDLICTION ZONE I.NTODIFIED FROM DRAGERT AND OTHERS, 19941 O TECTONIC SETTING SUMMARY OCT. 2009 • LOB NO 4935 FIG. 1B • H s7 rC ` ' U t)M 14 ` „ 1 11 ,.....,-,-,, 1. t J �. ¢ ~ '{'r \� � .. ' .i � _ •, ` ti , 1 • l t • • tr t 1. ,, CS 4` 't • r ''} 4� � � r - • •• ,'LsGi.tJ is t ti_� ' • • 1 0 _v I, !" " ' 1 � , ■ • �' V - ) 'i c J Tmyt � '7 . ♦ OgiT /"�dj 1 , 1 i �....--f__ •; , .� r �7_ y,' � � �' �$ 1 V y `C /� 7 � \�\ •�. 1. - ..r _ I �t f lL,(0.„. :/ '�` iti \ • f ) J /( '\�' . t•^ ..t ! �/ ) O i t ' . 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Contact — Approximately located - -••• Fault- Dashed where inferred: dotted where concealed; queried where doubtful: hall and bar on do.tnthrown side REGIONAL GEOLOGIC MAP -- Thrust intuit— Dashed where inferred; dotted where concealed. queried where doubtful; sawteeth on upper plate -1 Strike and dip of bed 00.2009 106 N0. 4033 FIG. ?B • 1 1 1 1 , 1 MAP EXPLANATION ' 1 . f , r l 0 I — '' -• - -_ ./.— r L IME OF MOST RCCENT SURFACE flUl'LI141 STRUCTURE TYPE AND RELATED FEATURES r‘t / _- 1a.ocaa 0410 pp yawl, a po. 0e0 0,Aeaapn I<15.PM Maa 15101 - : : L Nam. a Mqn ang..... 1.1{0 51 � � / / I .'- 1` . ( / no 44.000 °0100 m 0 _% S1.00431004 ") i 9 _.l !_ . .�_ ti .j — Lan aammarvl<Ia0000 po : al pa°wmato gla0a 71000lwo 4 1, •� � , � ( : i - -- Law and malda O,mavlvhl50000 wars, 150101 — MI.. 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Q 51041K1gn 0000 aNM SIP TRACE — / t1 ~ • � •• ..s ( (( CULTURAL AND GEO0RAP AbaIM 00400tI001090 xnb NIC FEATURES ' - \ � ' - 1, ' A i • 1\ 9 v � - ' - �. � \`:� / I.baMeao°uarous al map VC./ � omMn Noway v • _ roman a ax•laa 1000 .,� . -7— _" l'` , ,. - - ,) ...._ , 01000 a o°laoame ` �• t ' 781 ' �` Amara. m °aa a Paean • ;� \,[ c Camas Washou al ,711$ ..1. -.,, r i -` , �. _ " `��,n;.r� — � = y - iOugal min.°rIw°I ma a ...I _ ••. � "\ R \� 11 i l' 'u- _ �` ° ->,... i , Perm:me. or ommr enl man I ' �.% ^ . ! ti-. , v \\ :.5 . t : 1_ r C o /, „ R - . \-,-.....„,. y \ r ' � `i- -- _ x87 6 '; QS 141:=1 $78_ , � ' _ )� _Hillsboro -- i \ l "--- 1` . � � ^ ' 1 ,-- �� Fl T N.tIBER 8 1851E OF STRUCTURE �,. ... /, : ` ��— �� -y f —t w • �•� 4 � tL - y ( .. - • - F�UI. - 715 U BCA\rt.R10U FAULT 7061E CANBY MOLLAL4 �� J L r { 8f1(� t 1 ( ('{ N•-+•- 7I6 � E-AU 11 zoNr ' _1 — 1 _ k _ Y j � Giesham l \ l "'t ) ) `'� 1 .i.._ f I I 1 f , f , t J, 875 04TFIELD FAULT A\ 1 BI averl i -1,�.,,r !_-_.`\ ` 1C 4 t `,-- LJ 1 ^ r � • IN : a . _l. $ - 1, ' 6 i I 875 EAST RANK FAULT { — s7$ ti 879 +� • t 1 16 ,- �� _1. — a ; .` r � ` M R , ` � ^ !. � ` S �� _ 877 PORTLAND HILL FAl1LT i \ - 1 _ i 1 L.Jni I ' G am / 'I e.‘ � ` y- % . _- 8 79-1 f 7.1-4-,:,-.‘,, , % / RV ' { � tt . . er ,,, .t iff . C . \ \ - \5 ? � .` - - R y i I � 1 , 4 " :'- -- ' _ :.:1\ , \ \\ � � FROM IT2 �) II 5.F ?'D UiHEF 10 nwt 073 TIiP OF 677007 1077R�. (1 177. R1 F 1 I1Lfi 7 c- - J t y \K % r7 � J •�• - -R . ! � •p \ 669 Ft1D� I7 0106117 77 FILE 7977. i � 7 I j - ' - i . -1111) 1 71'7 1 I s �;� 1 i � \ _.J \j'.7 ', 0 5 10 MILES Newberg � 0 5 IO KIL01ffTER$ lYszommemisseid \� \ 4 Canby L 11 \ ~�, LOCAL FAULT MAP OCT. 2009 IOR NO. 4935 FRG. 38 APPEN DIX C Geotechnical Report by Northwest Testing Laboratories (April 21, 1976) Soils and Foundation Investigation Tigard Water District Proposed Reservoir Bull Mountain, Oregon J L i.y f v„?'" 4 , 4 , U ,.sr b ra, y d � c -i +C+ 19d^ Q � � - � 1 �� air �I{ I l l r Ir P 51 J - +. -.tji 1 4115 N. Mississippi Ave. Portland, Oregon 97217 288 -7086 NORTHWEST TESTING LABORATORIES 4115 N. MISSISSIPPI AVENUE PORTLAND. OREGON 97217 CONSTRUCTION INSPECTION - NON•DESTRUCTIVE TESTING MATERIALS INSPECTION WELDING CERTIFICATION CHEMICAL ANALYSIS April 21, 1976 SO,L TESTING PHYSICAL TESTING ASSAYING • Tigard Water District 8841 S.W. Commercial Street Tigard, Oregon 97223 Attention: Mr. Robert Santee Re: Soils and Foundation Investigation Proposed Reservoir Bull Mountain, Oregon Gentlemen: At your request we have performed a soils and foundation investigation at the site of your proposed reservoir on Bull Mountain, Oregon. We present herewith a report of our findings, conclusions and recommendations. Site Description The proposed reservoir site is located on the northeast corner of S. W. 125th Avenue and Bull Mountain Road, west of Tigard, Oregon. The site slopes gently in a generally northern direction with a total relief of 20 ft. The 2.42 acre site is now utilized as a filbert orchard. Subsurface Exploration Five test borings, locations of which are shown in Fig. 1, attached, were made on April 12, and 13, 1976 with a truck- mounted power auger using 8 -in. hollow flight augers. Samples were taken at 2.5 ft intervals up to 15 ft in depth and at 5 ft intervals thereafter with a 2 -in. O.D. split -spoon sampler, in conjunction with the Standard Penetration Test. The Standard Penetration Test is performed by driving a 2 -in. O.D. split -spoon sampler into the undisturbed formation at the bottom of the boring with repeated blows of a 140-lb pin- guided hammer falling 30 -in. The number of blows required to drive the sampler a given distance is a measure of the soil consistency. Samples were identified in the field, placed in sealed containers and transported - 2 - Tigard Water District Soils and Foundation Investigation to the laboratory for further classification and testing. Laboratory Tests Laboratory tests were performed on representative samples. These included natural water content, Atterberg Limits and particle size distribution. Results of tests are summarized in Table 1. Geology and Soils Units encountered during the course of this investigation consist of the Columbia River Basalts overlain by a series of silts termed locally the Upland Silts. A brief description of the encountered units is as follows: 1. Upland Silts (ML) A 12.5 ft to 15 ft thick unit of soft to moderately firm, Tight -brown clayey silt, merging to a rust brown, clayey silt with basalt fragments at depth and topped by a weathered crust of dark brown, clayey silt. This series is found throughout the Tualatin Valley on topographic highs, overlying the basalt. 2. Columbia River Basalts A unit several hundreds of feet thick of dense gray basalt topped by a layer of highly weathered basalt. At this site the basalt is overlain by a 5 ft to 10 ft thick layer of residual silty sand with rock fragments. Test boring Togs have been combined with topographic information to develop geologic cross sections (Figs. 2 and 3). - 3 - Tigard Water District Soils and Foundation Investigation Groundwater No groundwater was encountered during the course of this investigation; published hydrographs of the area show groundwater to be several hundred feet below surface level. Proposed Construction We understand construction plans call for a 10 million gallon reinforced concrete water reservoir to be located in the center of the proposed site. The tank will measure 221 ft in diameter and be founded directly on the underlying basalts, approximately 20 ft to 30 ft below present surface level. Conclusions and Recommendations From our investigation of the proposed reservoir site we draw the following principal con - clusions: 1. The upland silts may be used to support light or settlement tolerant structures; they should not, however, be used to support the main structure nor its contents. Bearing pressures of 3000 psf may be used in the Upland Silt. 2. The weathered basalt should be used as the bearing horizon. Footings placed in the weathered basalt basalt can be designed for contact pressures of 15,000 psf. 3. Excavations of up to 10 ft into the basalt will be necessary in some areas of the reservoir site. 4. If the excavation can be controlled to within 3 ft of the structure line, lateral earth pressures on the reservoir wall may be calculated - 4 - Tigard Water District Soils and Foundation Investigation 4. on the basis of equivalent fluid pressure of 30 pcf (for level backfill). — 5. Asphalt access roads and parking pads may be designed on the overlying silts for a CBR of 10. 6. Because the silts are sensitive to disturbance in presence of excess moisture, great care should be taken in earthwork operations and site preparation during the rainy season. We shall be pleased to assist you further in the completion of the design phase of the project and in resolving any unforeseen difficulties during the construction phase. Report Number 160581 Respectfully submitted, NORTHWEST TESTING LABORATORIES By: Charles R. Lane, Manager o f r 7 \ yr - ,�.. n r .. - . /94 / � 5� Neil Hwelker • Pr 5 j 4�3� r OREGON `b� �Y "Z H . T1hE ti • ■ TIGARD WATER DISTRICT Natural Moisture Boring Sample Depth Content, Liquid Plastic Plastic Number Number In Feet Percent Limit Limit Index B - 1 2.5 - 4.0 22.2 37 24 13 4 10.0 -11.5 20.8 53 24 29 6 15.0 -16.5 27.7 50 31 19 8 25.0 - 26.5 32.5 52 27 25 * * * * * * * * * * * * ** PARTICLE SIZE - PERCENT RETAINED Boring Sample Depth Number Number In Feet # 4 # 8 # 16 #40 # 100 # 200 - #200 B -5 1 2.5 - 4.0 0 0.1 1.3 3,2 10.4 18.9 66.0 4 10,0 -11.5 0 0 0.6 9.6 22.2 16.5 51.0 6 15.0 -16.5 0 0.3 6.7 15.5 24.1 18,4 35.0 8 25.0 -26.5 0 0 3.5 15.7 32.3 16.9 31.5 TABLE 1 .. _ ,• - • , ( / i.... e i / // _.---- 41° (‘I N _- ...A. 3 \ F ....:----' 7 i - B-4 . B.- ‘ _.,-- - . ‘ i , 1 1 1 I \ 1 . ------- • 1 \ --) 1.- \ - 1 (DUN - 1 - P , 1 l•-.1 SZ...t) . . 15 o.‘P I D1 - 1 — 1 C:::. 1-1 C. C_C!\--1C..5?"- 1 --- \ 1 0 1 '+.._. . • . . 1" = VC:4:::■ • . . „ . . v\ c. 1 . t 1:1,Q1-4 G** 1 EL ,4-'77.3. / C.lic ■rri: 4.t. 125 E t to rr.cxt r g ,, --': . 4 - ` t 1 f irvvi 6.1 \c.. bran. c-lzs_z 12...:.. Q `e- t.1 - 1$ w � ag - w+c3t6r � Q q -- 1 - 2z. -1b. v.,/ '; ' i . , -- 25. $e ".. tCkn y Q -- 1A, - .32_ • - • • • • • • • • 1 • • .. ' • tt • „- V*9:0 - 2i= 1 C .•' - =c>z . �� _ _ ,- 1;14 ik'=: •qua Y " (1-' • Cl ' V - ` • 4 - 11c • • 9: 1/4 130 ` 126° 122 °W TIGARD X 11) DQ\i' �� . 52 °N Coastline Coastal Cascades °' G� r t __ NORTH AME RICA Range 4 r / a PLATE ' British �'� _ ' Columbi r r r / ` 124.5 124.0 123.5 123.0 1 122.5 122.0 121.5 4/ 4 a ) ♦ / A LONG1TUt. C /EXPLORER a D - i PLATE :. a Vancouver 'SO � , 1 c' - Q DISTANCE IN y M Crustal faults Al, (' // / l ea p ` Q • i 10. .30. 50. 70. 90. 110. 130. 15 170. 190. 210. 230 250. 270. 290. di I d A 48° ► 0 - • ° -1 i ,, t - .1 Seattle Io. ° ° 3 � �a. o o : , o p la ,' o ; ' °°D North America Plate G W ashington • ° j . 4 o o °. 4 a a Plate I Crustal 04 .. / , JUAN DE FUCA Y 70 Interface ✓ selsmlctty p _ 70. c, � c / PLA p Portland _ I f? ` ' a nd e > ' earthquakes F ca ' O /a / - 90. c o A* -,' Oregon / o '` 130. 130. v .` . � > A 150. 1 1 1 T ----t 1 150 PACIFIC PLATE __ ..... - 144.5 124.0 123.5 12 122.5 122.0 121.5 a a / GORDA n LONGITUDE CD PLATE California ' DEFORMATION B) EAST -WEST CROSS - SECTION THROUGH WESTERN OREGON AT THE LATITUDE OF SHERWOOD, SHOWING THE SEISMIC SOURCES CONSIDERED IN THE SITE - SPECIFIC SEISMIC HAZARD STUDY (MODIFIED FROM 0 200 km Mendocino Fault . 7 ce 40 • : GEOMATRIX, 1995) o It. . A) TECTONIC MAP OF PACIFIC NORTHWEST, SHOWING ORIENTATION AND EXTENT OF CASCADIA SUBDUCTION ZONE (MODIFIED FROM DRAGERT AND OTHERS, 1994) TECTONIC SETTING SUMMARY OCT. 2009 JOB NO. 4935 FIG. 1B ?! t{ V 7c ` Z J � *� , T • 1 ` 1 n t �1 Tc til'o /��= c.. .i"' .� .. " Imo. !m C, V! � ` �\ �`� _ > �, , 'ti- y • ,� 1 �.\ L -, -.t. Qsl I jl f /' �,� 'J � , c �tY a ',` _ ` • y �� Tss T �' \ a r 1 r �/ L I -a J (: L I r ,,,; K r IV' �_}/♦ `. r�e� !^ � �.' 7 r °�. ^ . I �. 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"�2 J` r '"(� t ` \ \ C- •t�� y•s� -: � `�_ •`• =�`- i 'v )(.�'', \ I - : ^ T_..1 -, �. ` \ , ''. ;r�;;. ! � �•C ^i. ` �,L 1 , , - r. 3 t_ CIS TI \.� :.� ` -� 4. - Y --`tom TSI. �� _ '�-\.•• 7�.."� (�,,. ::`,•.:T G� ,.r �? 1 \ Tk \ . -�; -) , -9 r' } � ; "'' . - 1 '" _ . , ,. , / `)+ ' ,7. 1 • a.. Y .� ▪ -� - . ^ Tb t T L� \ y / j, ^� �, ��.-! -� -•t ,. T ' .... �r',�, ,-/If.,. • „ � y'.,r'f-G :f• ` .f ��`.� � /���,/`•/�`TSO C -�,"r' 4 ' - ' .: /` " =•' ,.7.;''- SITE \ - \ .•i1 `. '�'C��' \ ; �� ° \ .' \ t y .TC - U . 7 t - - ' • . j� \' i N `\� ` l/_' ��� r T cr- .r y/ i� t , ^T�- =�` tQ ' ` S` - 1 , 'a `•..,: -" �{ 1 t7L�f'� ._ a \� i l- y ' r fi ~ w .4. - k , � r .. -Tbae�l ... : m /" ) 1 �� ` \ 'l . %'��� . •∎ I t TC �".. c • ,„ - 't\+' „S \4 ..T"� �:�w ` Q9 ,. — •• > / - -4 ,.� j 1_t.�. ; '�-y ` i - -�!! �'`� \ e, Taal z t 1 L ` : ...-v `:. . , , t t : '. r c r` .L • i i ..' ;, �___ fr .. (,J j �e \v _ ' �!'. �` 4 t` ` : a'` r� s R , . t v fr \ �Tba= I 1 , \ �a �� rc - S .` ` I .•-) ` e'.1r ;^ �. V tt - •s_.. _', 5�� �i't. � - , . C, • 1 = r } ��' / =� � c '• }� "' t TfC / �� ��` BASE MAP FROM: WALKER, G.1V. AND ntACLEOD, N.S., 1991, GEOLOGIC �� TY �Y�w, y �� ^ y .'r } r :' c� 'r j � -� Ll�b `� MAP OF OREGON: U.S. GEOLOGICAL SURVEY �. r; / .r= _ j Tcr ��� I �. ` i s ;/ \"` : \ l /, i 1 / (r r t , ic, QT�jq \ Tht v,; -- J/ Ti i j ``-t_ " _ t-- ti � T,� f : r r _ ~ J ` TC� - '' > '--,: ' '/ },�� -:,, �/1 1. '° - I �- f l } _ (•.\N" � G �; I� t . 7 m � t � c WALSH, T.J., ET. AL., 1987, GEOLOGICAL MAP OF WASHINGTON r "[1 •tc . .�. T f y f �..��Z : Y �� J s u a'1t1�• - � �;'7 j�� 1 1C-� [��] - _ _ L� i t_r- =; / _ // !� �Lt-i• ,.. e ' - `; ,�,_` -� i Tbae7 ••.•� , ' ��•.,�� WASHINGTON STATE DEPARTMENT OF NATURAL RESOURCES, GM -3d ' h. 7 ty' I �� ; r \ I r /' 1�, /� - ,, / c R QTb N t QTba �.��� �\ t- �� - J .,. \,- (.\� rc \�C\ �, -..r,1 • J �r ( • y 1 �`, QS y �� r 4t �`t ;.�t� 1� - `^:� Tj t1 Y C \ � � °�' � 7, `,� Tss ' Ttvm7�s•' t ! %-- , ,. 1. ...•� I \ Ts1 , Q / c l_ , f^ t �> TfiC7 cam, x 1 � (� r• .� -.. ��Qsf-- ._ �> t ':�' roa, ,'^ .� J_,.t: !'. ,�"'1`S °��- _.- ..�_..i- -�•"/� , �_� � t"[. �\ "�r '�.1 � - Z, C7 `'., 1 _��- �'�iO1 1'. {{{(([`'''???� ,`r `` . ,'. r . i ( � 1 ' . �� ° `-t_ \ 1 � Tubl ( Tim C' ' • l ( _ 3 :• �� V - w .1.' •*f.`Y� - 1 ii t _ . ti J Qa . . r .l / ! \ ` _1,. , �1-- '�.:_� . t`. Ttr�f C" .... ;'C�Y'h.' 1 t i 11� t .1"' . -°•� J r r.i ti I '' /'�. 3r -. � , r ,1• ,To..• j 0 10 20 MILES ^� V - �`�C`1'� t _ • �� _��/ s J �! r" °� 4ti ,� , C a9�1 t t �� �� fj. \Trb j_ Q9 ^` c 1_- • `__ -� -,:_ . - - -•-- t =,- :'1 r .� - �. 9 f. !� :� ,, 'fir` - Tub • c'- „'`` -•r-� _ j _�. , Tcg'' c �, ( �. , i. l.� I - _ [ 1 t /' i> r' f ` ' ` ::`� J ' r _ <. � ..� 1 Wr ±�_� , 0 10 20 KILOMETERS —` e N , i/` - .. ' n ( • � ' i . . /� .� 1 t _ n ---A -� {' - '�'1 , J 1. 1 ,:, • '�- ,,��;.._ - � .. ��' \ y � L.�l ' • �0 T t .Y \ TY �' _( i r / ! 7 ' / / 1 - 1! J'- 1,`_ t ��, ` ;`, ^ 1 � : C \ ���� QIs ,��; :G.. �.- i l' ` ✓� - (S ' ;�, �T$d r ,' d / ` , r : F-�. �' L r �! `' �,: �''l ° 1 `'l .i � 1` f �� �� t Q7 f . \ �, , / � i � a� '-- / , • ,7 f '` '_. -- 1.';r\ 7.7,_ , -- c T I r l2 Tib ` Th1 • l - -1 \ \ \? "`� i Nt ) \ \ \` 1 sC + 1 `. -��- y r � I ;, �,, ! ` ' ;,1, -, ti -�,. Tsm ;\� I Tbaa7 QYb •- - r - 1� ) rib (\ , V_� `\ . / l ` _._._ -., i!_`. - -- .�, r __ti. tC. .. _. -.'.^: �_ �� �- .,:.atE = "w .. i�... r�t,l t ��a'_ -- �� s - - - - _ . � - _ - .�:- ._.... ▪ _ \�'•��- °... `•,4.� \ GR Contact - Approximately located - ? -••• F Dashed where inferred: dotted where concealed; queried,�'here doubtful; ball and bar REGIONAL GEOLOGIC MAP on downthro�,'n side I -` ?J •A• Thrust fault- Dashed where inferred; dotted where concealed; queried where doubtful; sawteeth on upper plate OCT. 2009 JOB N0. 1935 FIG. 2B MAP EXPLANATION � � © ` - TIME OF MOST RECENT SURFACE RUPTURE STRUCTURE TYPE AND RELATED FEATURES T t ,' , Holocene (<10.000 years) or post last gtaaat on (<15.000 years: 15 ka): -T--• Norma! or high-angle reverse taint ' J , , f r } j " - .. no tris ruptures in O to dais - jam Strik -s faun • �� S : l - — Lato Ouatemary (<130,000: p penultimate glaciation) -'.----4--1-- Thrust IaUII 4 . ✓ -• � - t - LatB and middle Ouatemary (<750 ,000 years: 750 ka) Anti sn al told II I ✓ � °� ( �,, \ I _ Ouatemary. undittereneated ( <t,600,000 years; <1.6 Ma) Syn told • .' { ` ° - Class 8 st toric ructure ( or ori regon gin uncertain) tvbnoainal told • . \ � ♦ _ - - - SLIP RATE .— Plunge direction o told ! �_ \ ` ; \ . �. x • ti r -�_' fault suction ma rkor d s� ° '.\ V 1 � ' Van cou ie. �. � ♦ - >5mmyear r 1 • - 877 \ 1 - 1.0-5.0 mm ♦ - mm/year DETAILED STUDY SITES • ♦ • -�- r r /r "� N -, � - - ♦ > r' - 0.2.1.Ommtyear 731 - Z r r. r i 1 - Trench site r s i ` �� r•� f ` • ' ` e l ® t ` J ♦ ♦ ... <0.2 mmyear 7 81 -2� Subduction zone study site J ' / . r /! ✓ f �`'. `�' --- \ 8� TRACE ' ` 1 �' . � •r . CULTURAL AND GEOGRAPHIC FEATURES z - - Mostty continuous at map scale r r, - _. / - ?•- ` ' . -' - -'�� � w� Mostly discontinuous at map Scale ------ Divided highway . , - a ': r \ - _. - --%-,--_-_-_,-„,.... - . 1 �\ - 2 �. /, / / - ' - Interred or concealed Primary or secondary road 1111 * �� , x r N s \ .rk k . 7 81-2 1 � A C �, W as h ouga l r ` � i r Permanent river or stream 714 ), Er i ! ' 11 _ -•- >, ' - \ - Intermittent river or stream ‘ ref. t \ - -� 'l \ 1 _ ` ' ^ \� - Permanent or intermittent lake t 1 ♦f 7 i� \\\,, y ' : J • , � _ ` _ �o /i r ni hra le ; ;r ., ♦ -- 0 '4111001,1116... n I ♦ FAULT NUMBER NAME OF STRUCTURE Hillsboro v ■� ' ♦ ♦ ■ 715 BEAVERTON FAULT ZONE ` ♦ �- r :i Po eland I Gres am ■ ? ' < > 716 CANBY MOLLALA FAULT ZONE i •44 815 OATFIELD FAULT Bea, e rton ,. 1 • -b= I a 9 r �'' 876 EAST BANK FAULT I • - 1 • • D HILLS FAULT _ ! ! -,878 - `♦ Ir 877 PORTLAND i 1 j %f dr 8 75 ,t' 877 .' 9 ` y ' � .. ? . .. / C < o" : , - . "r , . r SIT La , � � ti `s `;_T � �� , .'F�� .0„ Tttut_�i s �:�� �'` 8 9 1 ` , �� \j.'1-71;:.' ` i e ' ♦ ,'. i^'P, ', 1 , . . ' =': r 874 1;; i i' �_� - ),/- 3 of c4, • ti /,' ) y ' - FROM: PERSONIUS, S.F., AND OTHERS, 2003, MAP OF QUATERNARY FAULTS -,',1 ,../2/1 r1 ' � ' OPEN , / r' 0 • AND FOLDS IN USGS OPE FILE REPORT OFR-03-095. � ^ i•, OREGON, U 718 ' . r � . - =! r. © ;, = 0 5 10 MILES . kil `� = .';1' E : , I ; ` r f Newberg Rly __ v /J 0 5 10 KILOMETERS � � Cab O ,. G R LOCAL FAU LT MAP (REVISED FEB. 2010) OCT. 2009 JOB NO. 4935 FIG. 3B