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Report GEODESIGN, INC. GEOTECHNICAL, ENVIRONMENTAL, AND GEOLOGICAL CONSULTANTS /35 - 5 N5- 791 REPORT OF GEOTECHNICAL ENGINEERING SERVICES 72n Avenue Office Buildings Tigard, Oregon GDI Project: PNWP -18 For Pacific Northwest Properties 17400 SW Upper Boones Ferry Rd., Suite 230 • Portland, Oregon 97224 • Phone (503) 968 -8787 • Fax (503) 968 -3068 GEODESIGN, INC. GEOTECHNICAL, ENVIRONMENTAL, AND GEOLOGICAL CONSULTANTS October 26, 1999 Pacific Northwest Properties 9665 SW Allen Boulevard, Suite 115 Beaverton, Oregon 97005 Attention: Mr. Paul Gram Report of Geotechnical Engineering Services 72n Avenue Office Buildings Tigard, Oregon GDI Project: PNWP -18 GeoDesign, Inc. is pleased to submit four copies of our "Report of Geotechnical Engineering Services" for the proposed 72" Avenue Office Buildings to be constructed in Tigard, Oregon. Our services for this project were conducted in accordance with our August 20, 1999 proposal. We appreciate the opportunity to be of service to Pacific Northwest Properties. Please call if you have questions regarding this report. Sincerely, GeoDesign, Inc. A e_6 1 ),„..5 4 w - � George Saunders, P.E. Principal cc: Mr. Gene Mildren, Mildren Design Group, P.C. (3 bound & 1 unbound copies) Mr. Brian DeHaas, WRG Design, Inc. (1 bound copy) RKW:GPS:kt Attachments Document ID: PNWP -18 -geor Four copies submitted 17400 SW Upper Boones Ferry Rd., Suite 230 • Portland, Oregon 97224 • Phone (503) 968 -8787 • Fax (503) 968 -3068 Table of Contents Page No. INTRODUCTION 1 PURPOSE AND SCOPE 1 SITE CONDITIONS 2 Surface Conditions 2 Subsurface Conditions 2 CONCLUSIONS AND RECOMMENDATIONS 3 General 3 Site Preparation and Erosion Control 3 Construction Considerations 4 Structural Fill 4 Cement Amendment 5 Permanent Slopes 5 Shallow Foundations 6 Floor Slabs 6 Pavement Recommendations 7 Utility Trenches 8 Retaining Structures 8 Site Drainage 9 Seismic Design 10 OBSERVATION OF CONSTRUCTION 10 LIMITATIONS 10 FIGURES Vicinity Map Figure 1 Site Plan Figure 2 APPENDIX A Field Explorations A -1 Laboratory Testing A -1 Key to Test Pit and Boring Log Symbols Table A -1 Soil Classification System and Guidelines Table A -2 Logs of Test Pits Figure A -1 GeoDesign, Inc. i PNWP- 18:102699 Report of Geotechnical Engineering Services Proposed 72 Avenue Office Buildings Tigard, Oregon INTRODUCTION This report presents the results of GeoDesign's geotechnical engineering evaluation of the site of the proposed 72n Avenue Office Buildings. The approximately 2.6 -acre site is located at the northwest corner of SW Cherry Drive and SW 72n Avenue in Tigard, Oregon. The general location of the site relative to surrounding physical features is shown in Figure 1. We understand that the project will consist of constructing two (2) one -story, concrete tilt - up buildings with slab -on -grade floors, and appurtenant paving and utilities. We have assumed that column Toads will be less than about 150 kips and wall loads will be Tess than about 4.5 kips per linear foot, which is typical for concrete tilt -up construction. Sustained floor slab live loads will be less than about 300 pounds per square foot (psf). PURPOSE AND SCOPE The purpose of our services was to explore the subsurface conditions at the site to provide the basis for geotechnical recommendations for site development. Our specific scope of work included the following: • Coordinate and manage the field investigation, including site access authorizations and scheduling of subcontractors and GeoDesign field staff. • Explore subsurface conditions by excavating 11 test pits to depths of up to 14.0 feet or to refusal using a conventional rubber -tired backhoe. • Obtain soil samples at select depths in the test pit excavations. • Classify the materials encountered in the test pits. Maintain a detailed log of each exploration. Observe groundwater conditions in the explorations. • Determine the natural moisture content and density of select samples obtained from the explorations. • Provide recommendations for site preparation, grading and drainage, stripping depths, fill type for imported materials, compaction criteria, trench excavation and backfill, use of on -site soils, and wet/dry weather earthwork. • Provide recommendations for design and construction of shallow spread foundations, including allowable design bearing pressure and minimum footing depth and width. • Provide recommendations for preparation of floor slab subgrade. • Recommend design criteria for retaining walls, including lateral earth pressures, backfill, compaction, and drainage. • Provide recommendations for the management of identified groundwater conditions that may affect the performance of structures or pavement. GeoDesign, Inc. 1 PNWP- 18:102699 • Provide recommendations for construction of asphalt pavements for on -site access roads and parking areas, including subbase, base course, and asphalt paving thickness. • Provide recommendations for subsurface drainage of foundations and roadways, as necessary. • Provide a written report summarizing the results of our geotechnical evaluation. SITE CONDITIONS SURFACE CONDITIONS The approximately 2.6 -acre site is located '/4 mile south of Highway 217 at the northwest corner of SW Cherry Drive and SW 72' Avenue in Tigard, Oregon. The site slopes down about 14 feet to the west from SW 72n Avenue and approximately 24 feet down to SW Cherry Street to the south. There are currently two houses and two detached garages in the northeast portion of the site. A house previously located at the southeast comer of the site has been demolished with signs of the foundation still visible. The remainder of the site is covered with grass. Large deciduous and evergreen trees are present around the house at the north end of the site and occasionally in other areas. SUBSURFACE CONDITIONS We explored subsurface conditions at the site by excavating 11 test pits (TP -1 through 11) to depths of up to 14.0 feet below the existing ground surface. The approximate locations of the test pit excavations are shown in Figure 2. We tested selected soil samples from the explorations to determine the natural moisture content and dry density of the soils. Descriptions of the field explorations, exploration Togs, and laboratory procedures are included in Appendix A. We encountered relatively consistent subsurface conditions in the explorations. Subsurface materials at the site consist of 8 to 12 feet of stiff to very stiff silt underlain by medium dense to dense sand with varying amounts of silt. In Test Pits TP -1 to TP -5 we encountered a Tens of weak siltstone and partially cemented sand. However, this material was easily excavated with the backhoe. In addition, we observed between 3 and 5 feet of silt and gravel fill in Test Pits TP-4 and TP -5. We met practical refusal in TP -10 when we encountered a large boulder at approximately 11 feet. We observed slow groundwater seepage at depths of approximately 11.5 to 14 feet in Test Pits TP -1, TP-4, TP -6, and TP -9. Groundwater seepage was not observed in the remaining explorations. Slight caving was observed in Test Pit TP -1 below 10.0 feet. GeoDesign. Inc. 2 PNWP- 18:102699 CONCLUSIONS AND RECOMMENDATIONS GENERAL Based on the results of our explorations, laboratory testing, and analyses, it is our opinion that the proposed structures, with the building Toads as previously stated, can be supported on shallow footings bearing on the medium stiff to stiff silts, or on structural fill that is properly installed during construction. The following paragraphs present specific geotechnical recommendations for design and construction of the proposed development. SITE PREPARATION AND EROSION CONTROL • Based on our site plan, the existing structures will need to be removed prior to developing the site. All demolition debris and foundation elements, including those associated with the previously demolished dwells, should be removed prior to site grading. A member of our geotechnical staff should observe the exposed subgrade to determine if there are areas of unsuitable soil that may require overexcavation. Basement cavities (if present) and excavations formed by removal of unsuitable material, should be backfilled with structural fill. Trees should be removed from all building and paved areas. In addition, root balls should be grubbed out to the depth of the roots, which could exceed 2 feet below the ground surface. Depending on the methods used to remove the root balls, considerable disturbance and loosening of the subgrade could occur during site grubbing. We recommend that soil disturbed during grubbing operations be removed to expose firm undisturbed subgrade. The resulting excavations should be backfilled with structural fill. If grubbing activities disturb less than a 12 -inch depth of soil and the earthwork is being completed in the drier summer period, the material can be scarified, moisture - conditioned, and compacted in place. The existing topsoil, where it exists, and the thick root zone should be stripped and removed from the site in all proposed building and pavement areas and for a 5 -foot margin around such areas. Based on our explorations, the depth of stripping will be approximately 4 to 6 inches, although greater stripping depths may be required to remove localized zones of loose or organic soil. Greater stripping depths should be expected in the eastern third of the site and areas of the site that are heavily treed. Actual stripping depths should be based on field observations at the time of construction. Stripped material should be transported off -site for disposal or used in landscaped areas. After demolition, stripping and required site cutting have been completed, we recommend proofrolling the subgrade with a fully - loaded dump truck or similar -size, rubber -tire construction equipment to identify areas of excessive yielding. A member of our geotechnical staff, who will evaluate the subgrade, should observe the proofrolling. If areas of excessive yielding are identified, the material should be excavated and replaced with structural fill. Areas that appear to be too wet and soft to support proofrolling equipment should be prepared in accordance with the recommendations for wet weather construction. GeoDesign, Inc. 3 PNWP- 18:102699 The test pit excavations were backfilled using the relatively minimal compactive effort of the backhoe bucket and soft spots can be expected at these locations. In pavement and floor slab areas, we recommend that a minimum of 3 feet of the backfilled material be removed and the resulting excavation backfilled with structural fill. We recommend that the full depth of the backfill be removed and replaced with structural fill if the test pit is located within 2 feet of a footing. Silt fences, hay bales, buffer zones of natural growth, sedimentation ponds, and granular haul roads should be used as required to reduce sediment transport during construction to acceptable levels. Measures to reduce erosion should be implemented in accordance with Oregon Administrative Rules 340-41 -006 and 340 - 41-455 the City of Tigard and Washington County regulations regarding erosion control. CONSTRUCTION CONSIDERATIONS Trafficability of the silty areas of the site will be difficult during or after extended wet periods. When wet, the silty surficial soils are easily disturbed and will not provide adequate support for construction equipment. Proofrolling of the subgrade should not be performed during wet weather or if wet ground conditions exist. Instead, the subgrade should be evaluated by probing. Soils that have been disturbed during site preparation activities, or soft or loose zones identified during probing, should be removed and replaced with compacted structural fill. Haul roads subject to repeated construction traffic will require a minimum of 18 inches of imported granular material or 16 inches of cement amended soil (see "Cement Amendment" section of this report) overlain by a crushed rock wearing course. For Tight staging areas 12 inches of imported granular material should be sufficient. The imported granular material should consist of crushed rock that is well- graded and has less than 8 percent by weight passing the U.S. Standard No. 200 Sieve. A geosynthetic should be placed in the haul roads below the granular material and should have a minimum Mullen burst strength of 250 pounds per square inch (psi) for puncture resistance and an apparent opening size (AOS) between an U.S. Standard No. 70 and No. 100 Sieve. We recommend that 3 to 4 inches of imported granular material be placed in the bottom of footing excavations in wet weather conditions. The granular material reduces subgrade disturbance, prevents water softening of the upper surface, and provides a clean environment for reinforcing steel. STRUCTURAL FILL On -site Materials The on -site soils are suitable for use as structural fill. However, the silty soils at the site are sensitive to small changes in moisture content and are highly susceptible to disturbance when wet. Laboratory testing indicates that the moisture content of the on -site silt is greater than the anticipated optimum moisture content required for satisfactory compaction. Therefore, moisture conditioning will be required to achieve adequate compaction. We recommend using imported granular material for structural fill if the on -site materials cannot be properly moisture - conditioned. As an altemative, use of the on -site silt for structural fill GeoDesign. Inc. 4 PNWP- 18:102699 may be acceptable if it is properly amended with portland cement or lime. When used as structural fill, the on -site silty material should be placed in lifts with a maximum uncompacted thickness of 6 to 8 inches. The silt should be compacted to not less than 92 percent of the maximum dry density, as determined by American Society for Testing and Materials (ASTM) D 1557. If construction is planned for the wet season then careful consideration of the construction methods and schedule should be made to reduce overexcavation of disturbed site soils, and the project budget should reflect the recommendations for wet weather construction contained in this report. Imported Granular Material If imported granular material is used as structural fill, this material should consist of pit or quarry run rock, crushed rock, or crushed gravel and sand that is fairly well- graded between coarse and fine, contains no organic matter or other deleterious materials, has a maximum particle size of 3 inches, and has less than 5 percent passing the U.S. Standard No. 200 Sieve. The percentage of fines can be increased to 12 percent of the material passing the U.S. Standard No. 200 Sieve if placed during dry weather. Imported granular material should be moisture - conditioned to the approximate optimum moisture content, placed in 12- inch -thick lifts, and compacted to not less than 95 percent of maximum dry density as determined by ASTM D 1557. CEMENT AMENDMENT As an alternative to the use of imported granular material for structural fill, working blankets, and haul roads, an experienced contractor may be able to amend the on -site soils with portland cement to obtain suitable support for fill operations and /or support of construction equipment. Based on the moisture contents, soil type, and processing speed, cement amendment would be more suitable at this site than lime amendment. Successful use of soil amendment depends on use of correct techniques and equipment, soil moisture content, and the amount of portland cement added to the soil. Recommended cement percentages are based on soil moisture contents at the time of placing the structural fill. Based on our tests and experience, about 4 percent by dry weight of soil can generally be used when the soil moisture content does not exceed approximately 25 percent. If the soil moisture content is in the range of 25 to 35 percent, we recommend 5 to 6 percent cement by weight of dry soil. It is difficult to accurately predict field performance due to the variability in soil response to portland cement amendment. The percentage of cement may need to be adjusted based on field observations and performance. For preliminary design purposes, we recommend a minimum of 5 percent cement and a treatment depth of 12 inches. At this site, 5 percent cement would correspond to about 4.8 pounds of cement per square foot, for a 12 -inch treatment depth. PERMANENT SLOPES Permanent cut and fill slopes should not exceed 2H:1V (horizontal to vertical). Buildings, access roads, and pavements should be located at least 5 feet from the top of cut and fill GeoDesign. Inc. 5 PNWP- 18:102699 slopes. The slopes should be planted with appropriate vegetation to provide protection against erosion as soon as possible after grading. Surface water runoff should be collected and directed away from slopes to prevent water from running down the face of the slope. SHALLOW FOUNDATIONS We recommend that spread footings bear on the very stiff silt, or structural fill that is properly installed during construction and underlain by undisturbed native materials. Spread footings should have a minimum width of 24 inches, with the base of the footings founded at least 12 and 18 inches below the lowest adjacent grade for interior and exterior footings, respectively. Continuous wall footings should have a minimum width Of 18 inches, and be founded a minimum of 18 inches below the lowest adjacent grade. Bearing Pressure and Settlement Footings with the preceding loads and founded as recommended should be proportioned for a maximum allowable soil bearing pressure of 2,500 psf. This bearing pressure is a net bearing pressure and applies to the total of dead and long -term live loads and may be increased by 1/3 when considering earthquake or wind loads. The weight of the footing and overlying backfill can be ignored in calculating footing loads. For a 2,500 psf design bearing pressure, total settlement of footings is anticipated to be less than about 1 -inch for the building loads discussed above. Differential settlements should not exceed 'h -inch. Lateral Capacity We recommend using a passive pressure of 250 pounds per cubic foot (pcf) for design purposes for footings confined by native silt or structural fill. In order to develop this capacity, concrete must be poured neat in excavations or the adjacent confining structural fill must consist of granular soils compacted to 95 percent relative to ASTM D 1557. Adjacent floor slabs, pavements, or the upper 12 -inch depth of adjacent, unpaved areas should not be considered when calculating passive resistance. A coefficient of friction equal to 0.35 may be used when calculating resistance to sliding on silt subgrades. FLOOR SLABS Satisfactory subgrade support for building floor slabs supporting up to 300 psf areal loading can be obtained from the stiff native silt, or from structural fill, when prepared in accordance with the recommendations presented in the "Site Preparation" and "Structural Fill" sections of this report. A minimum 6- inch -thick layer of base rock should be placed over the prepared subgrade to assist as a capillary break. A subgrade modulus of 250 pounds per cubic inch can be used for the design of the floor slab. Floor slabs constructed as recommended will likely settle less than 'A -inch. GeoDesign, Inc. 6 PNWP- 18:102699 Vapor barriers are often required by flooring manufacturers to protect flooring and flooring adhesives. Many flooring manufacturers will warrant their product only if a vapor barrier is installed according to their recommendations. Selection and design of an appropriate vapor barrier, if needed, should be based on discussions among members of the design team. We can provide additional information to assist you with your decision. Floor Slab Base Floor slab base rock should consist of crushed rock that is fairly well - graded between coarse and fine, contains no organic matter or other deleterious materials, has a maximum particle size of 1'% inches, and has less than 5 percent passing the U.S. Standard No. 200 Sieve. The floor slab base rock should be placed in one lift and compacted to not Tess than 95 percent of maximum dry density, as determined by ASTM D 1557. PAVEMENT RECOMMENDATIONS General The pavement subgrade should be prepared in accordance with the previously described site preparation, wet weather construction, and structural fill recommendations. Our pavement recommendations assume that paving will be conducted in an extended period of dry weather. Wet weather construction could require an increased thickness of aggregate base. We do not have specific information on the frequency and type of vehicles that will use the area; however, we have assumed that traffic conditions will consist of fewer than 20, 18 -kip Equivalent Single Axle Loads (ESAL's) per day. We should reevaluate these thicknesses if traffic exceeds this assumption. We used a subgrade resilient modulus of 6,000 psi in our analyses. We recommend a section consisting of 3.0 inches of asphalt concrete (AC) over 10.0 inches of aggregate base in areas where truck traffic is expected. If parking areas are limited to passenger automobiles only, the pavement section can be reduced to 2.5 inches of AC over 8.0 inches of crushed rock. If the subgrade is amended with portland cement, the pavement section can be reduced to 2.5 inches of AC over 6.0 inches of aggregate base for both truck and passenger car traffic areas. This recommendation is based on a minimum mixing depth of 12 inches and a minimum 7 -day unconfined compressive strength of 100 psi. The AC pavement should conform to Section 00745 for standard- and heavy -duty asphalt pavements of the Supplemental Standard Specifications for Highway Construction, Oregon Department of Transportation, 1996 Edition. The crushed rock base should conform to Section 02630 of Standard Specifications for Highway Construction, Oregon Department of Transportation, 1996 Edition and have less than 5 percent passing the U.S. No. 200 Sieve. Crushed rock base should be placed in a single lift and compacted to not less than 95 percent of the maximum dry density, as determined by ASTM D 1557. GeoDesign, Inc. 7 PNWP- 18:102699 • UTILITY TRENCHES Utility Trench Excavation Trench cuts should stand vertical to a depth of approximately 4 feet, provided no groundwater seepage is observed in the trench walls. Open excavation techniques may be used to excavate trenches with depths between 4 and 8 feet, provided the walls of the excavation are cut at a slope of 1 H:1 V, groundwater seepage is not present and with the understanding that some sloughing may occur. The trenches should be flattened to 1 %H:1 V if excessive sloughing occurs. Additionally, trench dewatering may be required to maintain dry working conditions if the invert elevations of the proposed utilities are below the groundwater level. Pumping from sumps located within the trench will likely be effective in removing water resulting from seepage. While we have described certain approaches to the trench excavation, it is the contractors responsibility to select the excavation and dewatering methods, to monitor the trench excavations for safety and to provide any shoring required to protect personnel and adjacent improvements. All trench excavations should be in accordance with applicable OSHA and state regulations. Trench Backfill Material Trench backfill for the utility pipe base and pipe zone should consist of well - graded granular material containing no organic material or other deleterious material, have a maximum particle size of 3 h -inch, and have less than 8 percent passing the U.S. Standard No. 200 Sieve. Backfill for the pipe base and within the pipe zone should be placed in maximum 12 -inch- thick lifts and compacted to not less than 90 percent of the maximum dry density, as determined by ASTM D 1557 or as recommended by the pipe manufacturer. Backfill above the pipe zone should be placed in maximum 12- inch -thick lifts and compacted to not less than 90 percent of the maximum dry density, as determined by ASTM D 1557. Trench backfill located within 2 feet of finish subgrade elevation should be placed in maximum 12- inch -thick lifts and compacted to not less than 95 percent of the maximum dry density, as determined by ASTM D 1557. RETAINING STRUCTURES The following design recommendations are based on the assumptions that: (1) the walls consist of conventional cantilevered retaining walls or embedded building walls, (2) the walls are less than 10 feet in height, (3) the backfill is level and drained and consists of SQ imported granular materials, and (4) no surcharges are imposed behind the wall. °/� Reevaluation of our recommendations will be required if the retaining wall design criteria for the project vary from these assumptions. For walls not restrained from rotation, we recommend using an equivalent fluid pressure of 38 pcf for design. We recommend using an equivalent fluid pressure of 55 pcf for design of walls restrained from rotation. When computing resistance to lateral loads, a base friction GeoDesign, Inc. 8 PNWP- 18:102699 coefficient of 0.35 and a passive resistance of a 250 pcf fluid can be used. Footings for the retaining walls should be designed in accordance with the recommendations given for shallow spread footings. As stated above, our recommendations are based on the assumption of drained conditions. Drains that consist of a 6- to 8- inch - diameter perforated drainpipe should be installed behind all retaining structures. The pipe should be embedded in a minimum 3- foot -wide zone of drain rock and sloped to drain (minimum slope of 1 /2 percent) toward a suitable discharge. The drain rock should be wrapped in a geotextile. Backfill material placed behind the wall and extending a horizontal distance of 1H, where H is the height of the retaining wall, should consist of the well - graded gravel, with not more than 5 percent by weight passing the U.S. Standard No. 200 Sieve. Alternatively, the on -site soils can be used as backfill material provided a minimum 2- foot -wide column of drain rock wrapped in a geotextile is placed against the wall. The rock column should extend from the foundation drains to within approximately 1 -foot of the ground surface. The geotextile should have an AOS between the U.S. Standard No. 70 and 100 Sieve and a water permittivity greater than 1.5 sec'. The drain rock should be uniformly graded, have a maximum particle size of 3 inches, and have less than 2 percent passing the U.S. Standard No. 200 Sieve (washed analysis). Backfill should be placed and compacted as recommended for structural fill, with the exception of backfill placed immediately adjacent to walls. Backfill adjacent to walls should be compacted to a lesser standard to reduce the potential for generation of excessive pressure on the walls. Backfill located within a horizontal distance of 3 feet from the retaining walls should be compacted to approximately 90 percent of the maximum dry density, as determined by ASTM D 1557. Backfill placed within 3 feet of the wall should be compacted in lifts less than 6 inches thick using hand - operated tamping equipment (such as jumping jack or vibratory plate compactors). If flat work (slabs, sidewalk, or pavement) will be placed adjacent to the wall, we recommend that the upper 2 feet of fill be compacted to 95 percent of the maximum dry density, as determined by ASTM D 1557. Settlements of up to 1 percent of the wall height commonly occur immediately adjacent to the wall as the wall rotates and develops active lateral earth pressures. Consequently, we recommend that construction of flat work adjacent to retaining walls be postponed at least four weeks after construction, unless survey data indicates that settlement is complete prior to that time. SITE DRAINAGE We recommend that subsurface drains be connected to a tightline leading to the storm drain. Pavement surfaces and open space areas should be sloped such that the surface water runoff is collected and routed to suitable discharge points. We recommend that the ground and paved surfaces adjacent to the building be sloped to drain away from the building. GeoDesign, Inc. 9 PNWP- 18:102699 SEISMIC DESIGN We recommend that the building be designed using the applicable provisions of the State of Oregon Structural Specialty Code for Zone 3. Site conditions correspond to a soil profile type of So and Uniform Building Code 1997 seismic coefficient of C = 0.36. OBSERVATION OF CONSTRUCTION Satisfactory foundation and earthwork performance depends to a large degree on quality of construction. Sufficient monitoring of the contractor's activities is a key part of determining that the work is completed in accordance with the construction drawings and specifications. Subsurface conditions observed during construction should be compared with those encountered during the subsurface exploration. Recognition of changed conditions often requires experience; therefore, qualified personnel should visit the site with sufficient frequency to detect whether subsurface conditions change significantly from those anticipated. We recommend that GeoDesign be retained to monitor construction at the site to confirm that subsurface conditions are consistent with the site explorations and to confirm that the intent of project plans and specifications relating to earthwork and foundation construction are being met. LIMITATIONS We have prepared this report for use by Pacific Northwest Properties and its design team in the proposed development of the proposed 72' Avenue Office Buildings in Tigard, Oregon. The data and report can be used for bidding or estimating purposes, but our report, conclusions, and interpretations should not be construed as a warranty of the subsurface conditions and are not applicable to other sites. Test pit excavations indicate soil conditions only at specific locations and only to the depths penetrated. They do not necessarily reflect soil strata or water level variations that may exist between exploration locations. If subsurface conditions differing from those described are noted during the course of excavation and construction, reevaluation will be necessary. The site development plans and design details were preliminary at the time this report was prepared. When the design has been finalized and if there are changes in the site grades or location, configuration, design loads, or type of construction for the building, the conclusions and recommendations presented may not be applicable. If design changes are made, we should be retained to review our conclusions and recommendations and to provide a written evaluation or modification. The scope of our services does not include services related to construction safety precautions, and our recommendations are not intended to direct the contractor's methods, GeoDesign, Inc. 10 PNWP- 18:102699 techniques, sequences or procedures, except as specifically described in our report for consideration in design. Within the limitations of scope, schedule and budget, our services have been executed in accordance with the generally accepted practices in this area at the time this report was prepared. No warranty or other conditions, express or implied, should be understood. ♦♦ We appreciate the opportunity to be of continued service to you. Please call. if you have questions concerning this report or if we can provide additional services. Sincerely, GeoDesign, Inc. Ryan K. White, E.I.T. Geotechnical Staff .<4' 0IiV d :p ALe-"cbb a 18.025 L AGON c George Saunders, P.E. PO -GAY 25.1 c�°i,� Principal Qty P. 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' :•I. !I' , 3nv� : �B M a3 • ' 'i; l .r�s' ..v r,t ! ••I ei : :a' :•\ ` ; - ;.'' 11. , `I •' 1 l ' . 1 i 1 I 1 I f 1 1' i ,, 1 ', ■ * (T) ji* I , . . TP_:7 . __.1 IL-2-.7.-7-.1=J I - -- TP -9 ° - - , - TP- 8 1 . 0 0 ___ _„, . e I , , , ______ ( --7------* A' i I PROPOSED BUILDING : i I ° j .1 * L. . 0 _______ _.I. -1 1 1 ) C 1 I I r I i . .. -i : i I i w' TP- I z Lu r l TP -5 w III w I TP -10 - -- iJ _ Q I N. I` Z h I TP -3� H cv • - -- I -- - 1 .- TP -4 I j gi l ( J PROPOSED BUILDING I 0 •I 1 ) • 1) ___ --- -- �- i� , , : . ; 1 o T P -1� ,, , TP -11 I I 1 i : r --- I TP -2 J Ci)-leri 1 SW CHERRY DRIVE ---*** i / 6 \ N EXPLANATION: 0 50 1 + 0 FT TP -1 S TEST PIT SITE PLAN FROM DRAWING PROVIDED BY MILDREN DESIGN GROUP, P.C. G EODESIGN, INC. SITE PLAN PNWP -18 OCTOBER 1999 FIGURE: I APPENDIX A FIELD EXPLORATIONS We explored subsurface conditions at the site by excavating 11 test pits (TP -1 through TP- 11) at the approximate locations shown in Figure 2. Gordon Van Domelen Excavating excavated the test pits using a rubber -tired backhoe to depths of between 7 and 14 feet on September 1, 1999. We chose the test pit locations based on a site plan provided to our office by Mildren Design Group. We determined the exploration locations in the field from existing site features. The locations shown on Figure 2 should be considered approximate. A qualified member of GeoDesign's staff observed and documented all field activities. We obtained representative samples of the various soils encountered for geotechnical laboratory testing. Classifications and sampling intervals are shown on the Togs included in this appendix. We classified the materials in the field in accordance with the "Key to Test Pit and Boring Log Symbols" (Table A -1) and "Soil Classification System and Guidelines" (Table A -2), copies of which are included in this appendix. The test pit logs indicate the depths at which the soils or their characteristics change, although the change actually may be gradual. If the change occurred between sample locations, the depth was interpreted. LABORATORY TESTING We classified soil samples in the laboratory to confirm field classifications. The laboratory classifications are included in the test pit logs if those classifications differed from the field classifications. We tested the natural moisture content of selected soil samples in general accordance with guidelines presented in ASTM D 2216. The moisture contents are included in the test pit logs in this appendix. GeoDesign, Inc. A -1 PNWP- 18:091099 KEY TO TEST PIT AND BORING LOG SYMBOLS SYMBOL SAMPLE DESCRIPTION LOCATION OF SAMPLE OBTAINED IN GENERAL ACCORDANCE WITH ASTM D 1586 STANDARD PENETRATION TEST LOCATION OF SPT SAMPLING ATTEMPT WITH NO SAMPLE RECOVERY LOCATION OF SAMPLE OBTAINED USING THIN WALL, SHELBY TUBE, OR GEOPROBE SAMPLER IN GENERAL ACCORDANCE WITH ASTM D 1587 LOCATION OF THIN WALL, SHELBY TUBE, OR GEOPROBE SAMPLING ATTEMPT WLTH NO SAMPLE RECOVERY LOCATION OF SAMPLE OBTAINED USING DAMES AND MOORE SAMPLER AND 300 POUND HAMMER OR PUSHED LOCATION OF DAMES AND MOORE SAMPLING ATTEMPT (300 POUND HAMMER OR PUSHED) WITH NO SAMPLE RECOVERY LOCATION OF GRAB SAMPLE WATER LEVEL GEOTECHNICAL TESTING EXPLANATIONS PP POCKET PENETROMETER LL LIQUID LIMIT TOR TORVANE PI PLASTICITY INDEX CONSOL CONSOLIDATION PCF POUNDS PER CUBIC FOOT DS DIRECT SHEAR PSF POUNDS PER SQUARE FOOT P200 PERCENT PASSING U.S. NO. 200 SIEVE TSF TONS PER SQUARE FOOT W MOISTURE CONTENT P PUSHED SAMPLE DD DRY DENSITY OC ORGANIC CONTENT ENVIRONMENTAL TESTING EXPLANATIONS CA SAMPLE SUBMITTED FOR CHEMICAL ND NOT DETECTED ANALYSIS NS NO VISIBLE SHEEN PID PHOTOIONIZATION DETECTOR HEADSPACE ANALYSIS SS SLIGHT SHEEN PPM PARTS PER MILLION MS MODERATE SHEEN MG /KG MILLIGRAMS PER KILOGRAM HS HEAVY SHEEN P PUSHED SAMPLE KEY TO TEST PIT AND GEODESIGN, INC. BORING LOG SYMBOLS TABLE A -1 SOIL CLASSIFICATION SYSTEM MAJOR DIVISIONS SYMBOL NAME GRAVEL GW Well graded, fine 10 coarse gravel CLEAN GRAVEL More than 50% of GP Poorly graded gravel coarse fraction COARSE GRAINED retained on GM Silty gravel No. 4 Si GRAVEL WITH FINES o. Sieve SOILS GC Clayey grovel More than 50% retained on SW Well graded, fine to coarse sand No. 200 Sieve SAND CLEAN SAND SP Poorly graded sand More than 50% of coarse fraction passes SM Silty sand No. 4 Sieve SAND WITH FINES SC Clayey sand ML Low plasticity silt SILT AND CLAY INORGANIC Liquid Limit CL Low plasticity clay FINE GRAINED SOILS less than 50% ORGANIC OL Organic silt, organic clay More than 50% passes MH High plasticity silt No. 200 Sieve SILT AND CLAY INORGANIC Liquid Limit CH High plasticity clay, fat day greater than 50% ORGANIC OH Organic clay, organic silt HIGHLY ORGANIC SOILS PT Peat SOIL CLASSIFICATION GUIDELINES GRANULAR SOILS COHESIVE SOILS STANDARD STANDARD UNCONFINED RELATIVE DENSITY PENETRATION CONSISTENCY PENETRATION COMPRESSIVE RESISTANCE RESISTANCE STRENGTH (TSF) Very Loose 0 - 4 Very Soft Less than 2 Less than 0.25 Loose 4 - 10 Soft 2 - 4 0.25 - 0.50 Medium Dense 10 - 30 Medium Stiff 4 - 8 0.50 - 1.0 Dense 30 - 50 Stiff 8 - 15 1.0 - 2.0 Very Dense More than 50 Very Stiff 15 - 30 2.0 - 4.0 Hard More than 30 More than 4.0 GRAIN SIZE CLASSIFICATION Boulders 12 - 36 inches SUBCLASSIFICATIONS Cobbles 3 - 12 inches Percentage of other material in sample Gravel % - 3 inches (coarse) Clean 0 - 2 % -' /. inches (fine) Trace 2 - 10 Sand No. 10 - No. 4 Sieve (coarse) Some 10 - 30 No. 10 - No. 40 Sieve (medium) Sandy, Silty, Clayey, etc. 30 - 50 No. 40 - No. 200 Sieve (fine) Dry = very law moisture. dry to the touch; Moist = damp. without visible moisture; Wet = saturated, with visible free water. SOIL CLASSIFICATION SYSTEM GEODESIGN, INC. AND GUIDELINES TABLE A -2 DEPTH /FT MATERIAL DESCRIPTION TESTING TP -1 0- ML Hard, orange and gray mottled, brown SILT with trace sand; dry to moist (4 -inch thick root I - zone). 2 - 3 - 4 - becomes medium stiff to stiff at 4.0 feet W = 28% 5- 6- 7- 8- becomes soft; wet at 8.0 feet 9- 10- 11- 12- with siltstone lens at 12.5 feet 13- becomes gray with trace to some sand at 13.0 feet W =37% 14 Test pit completed at 14.0 feet on September 1, 1999. 15- Disturbed samples obtained at 1.0, 4.0 and 14.0 feet. Slow groundwater seepage observed at 14.0 feet. Slight caving observed below 10.0 feet TP -2 0- ML -FILL Hard, brown SILT FILL with some angular cobbles; moist (4 -inch thick root zone). 2 - ML Very stiff, orange mottled, brown SILT; moist. 3 - W =203% 4 - 5 6 - 7- 8 - with siltstone lens at 8.0 feet 9- 10 - 11 W = 36% Test pit completed at 11.0 feet on September 1, 1999. 12 - Disturbed samples obtained at 3.0, 8.0 and 11.0 feet. No groundwater seepage or caving observed to the depth explored. 13- 14- 15- TEST PIT LOGS GEODESIGN, INC. PNWP -18 OCTOBER 1999 FIG. A -1 • I DEPTH /FT MATERIAL DESCRIPTION TESTING TP -3 0- ML Hard, brown SILT with trace fine sand; dry to moist (5 -inch thick root zone). 1 - 2 - 3 - 4 - becomes stiff to very stiff at 4.0 feet W = 25% 5 - 6 - 7 - becomes hard and partially cemented at 7.0 feet 8J / SP Medium dense, brown SAND with some silt; moist. 9- W =33% 10- 11 Test pit completed at 11.0 feet on September 1, 1999. 12- Disturbed samples obtained at 4.0 and 10.0 feet. No groundwater seepage observed to the depth explored. 13- No caving observed to the depth explored. 14- 15- TP-4 0- ML -FILL Dense, brown, silty GRAVEL FILL (4 -inch thick root zone). 1- 2 W = 10% 3 ML Medium stiff to stiff, dark brown SILT; moist. 4- W = 1 7% 5- 6 grades to with trace fine sand at 6.0 feet 7- 8- 9- 10 SP Hard, brown, partially cemented SAND; moist. 11_ SP Medium dense, brown SAND with trace to some silt; moist. W = 32% 12- Test pit completed at 11.5 feet on September 1, 1999. Disturbed samples obtained at 2.0, 4.5 and 11.5 feet. 13 - Slow groundwater seepage observed at 11.5 feet. 14 - No caving observed to the depth explored. 15- TEST PIT LOGS GEODESIGN, INC. PNWP -18 I OCTOBER 1999 FIG. A -2 • DEPTH /FT MATERIAL DESCRIPTION TESTING TP -5 0- GW -FILL Dense, gray rounded to subrounded GRAVEL ALL; dry. 1- ML -FILL Very stiff, brown SILT FILL with occasional gravel; moist. W = 22% 2 ML -FILL Soft to medium stiff, orange mottled, dark brown SILT FILL with trace fine sand and debris 3- (bumf wood). moist 4 - W = 26% 5 6 - ML Medium stiff, brown SILT with some fine sand; moist. 8 J SM Dense, brown and black, partially cemented, silty SAND; moist. 9- 10 W = 35% 11 - Test pit completed at 10.0 feet on September 1, 1999. Disturbed samples obtained at 1.0, 4.0 and 10.0 feet. 12- No groundwater seepage or caving observed to the depth explored. 13- 14- 15 TP -6 0- ML Hard, desiccated, orange and gray mottled, brown SILT; dry to moist; moist (3 -inch thick 1- root zone). W =9% 2- becomes very stiff at 2.5 feet 3 - 4- W = 32% 5- becomes medium stiff to stiff at 5.0 feet 6- 7- 8- 9 - 10 _ ML Soft, brown SILT with some fine sand; moist. 11- 12- 13- Test pit completed at 12.5 feet on September 1, 1999. 14 - Disturbed samples obtained at 2.0, 5.0 and 10.5 feet. Slow groundwater seepage observed at 12.5 feet. 15 - No caving observed to the depth explored. TEST PIT LOGS GEODESIGN, INC. PNWP -18 1 OCTOBER 1999 I FIG. A -3 • DEPTH /FT MATERIAL DESCRIPTION TESTING TP -7 0- MI Hard, desiccated, brown SILT; dry 10 moist (5 -inch thick root zone). 1- 2 - 3 - 4 - becomes very stiff at 4.0 feet W = 28% 5 - 6- 7_ 8 SM Medium dense, brown, silty SAND; moist. 9- 10- 11 W = 31% Test pit completed at 11.0 feet on September 1, 1999. 12 - Disturbed samples obtained at 4.0 and 11.0 feet. No groundwater seepage or caving observed to the depth explored. 13 14- 15- TP -8 0- 1 " ML Hard, desiccated, orange mottled, brown SILT with trace fine sand; dry to moist W = 11% 2 (6 -inch thick root zone). 3- 4 5 - becomes very stiff at 5.0 feet W = 31% 6 - 7 Test pit completed at 7.0 feet on September 1, 1999. 8 - Disturbed samples obtained at 1.0 and 5.0 feet. No groundwater seepage or caving observed to the depth explored. 9- 10- 11- 12- 13- 14- 15- GEODESIGN, INC. TEST PIT LOGS PNWP -18 OCTOBER 1999 FIG. A -4 DEPTH /FT MATERIAL DESCRIPTION TESTING TP -9 0- ML Hard, desiccated, orange and gray mottled, brown SILT; dry to moist (4 -inch thick root 1 - zone). 2- 3- W =13% 4- becomes very stiff with trace fine sand at 4.0 feet 5- 6 - 7- • 8- 9- 10- boulder encountered at 10.0 feet 11- W= 28% 12- Test pit completed at 11.5 feet on September 1, 1999. Disturbed samples obtained at 3.0 and 11.5 feet. 13 - Slow groundwater seepage observed 0 1 1 1 . 5 feet. t 4 - No caving observed to the depth explored. 15- TP-10 0- ML Hard, desiccated, orange mottled, brown SILT; moist (6 -inch thick root zone). - W =14% 2- 3 - 4 - 5- becomes stiff to very stiff at 5.0 feet W = 31% 6- 7 - 8 - 9- 10- 1 large boulder encountered at 11.0 feet 12- Test pit completed 0 1 1 1 . 0 feet due to practical refusal on September 1, 1999. Disturbed samples obtained at 2.0 and 5.0 feet. 13- No groundwater seepage or caving observed to the depth explored. 14- 15- GEODESIGN, INC. TEST PIT LOGS PNWP -18 OCTOBER 1999 I FIG. A -5 DEPTH /FT MATERIAL DESCRIPTION TESTING TP -11 0- ML Very stiff, orange and brown mottled SILT; moist (5 -inch thick root zone). 1 - W =10% 2- 3 - 4- 5 - becomes stiff at 5.0 feet W = 31% 6- DD = 90 PCF W = 32% 8 - 9 10 SM Medium dense, brown, silty, fine SAND; moist. 11- W = 36% 12 Test pit completed at 12.0 feet on September 1, 1999. 13- Relatively undisturbed sample obtained from 5.0 to 7.0 feet. 14- Disturbed samples obtained at 1.5, 5.0 and 1 1.5 feet. No groundwater seepage or caving observed to the depth explored. 15- GEODESIGN, INC. TEST PIT LOGS PNWP -18 OCTOBER 1999 FIG. A -6