The URL can be used to link to this page

Home My WebLink AboutSWP272855(1) GEOTECHNICAL ENGINEERING STUDY — c�- PROPOSED BLACKRIVER CORPORATE PARK POWELL AVENUE SOUTHWEST RENTON, WASHINGTON E-1990-20 November 3, 1999 PREPARED FOR BLACKRIVER-RIVERTECH LLC Kristina M. Weller, P.E. Project Engineer M� i ram` - Al- Kyle R. Campbell, P.E. "� 3 Manager of Geotechnical Services APR 18 2.000 P Earth Consultants, Inc. BUILDING DIVISION 1805 - 136th Place Northeast, Suite 201 Bellevue, Washington 98005 i i (425) 643-3780 -NN� Toll Free 1-888-739-6670 LAOW:51 %4 0 =vJ&*7 IMPORTANT INFORMATION ABOUT YOUR GEOTECHNICAL ENGINEERING REPORT .40 More construction problems are caused by site subsur- technical engineers who then render an opinion about face conditions than any other factor. As troublesome as overall subsurface conditions, their likely reaction to subsurface problems can be, their frequency and extent proposed construction activity, and appropriate founda- have been lessened considerably in recent years,due in tion design. Even under optimal circumstances actual large measure to programs and publications of ASFE/ conditions may differ from those inferred to exist, The Association of Engineering Firms Practicing in because no geotechnical engineer, no matter how the Geosciences. qualified,and no subsurface exploration program, no matter how comprehensive.can reveal what is hidden by The following suggestions and observations are offered earth,rock and time.The actual interface between mate- to help you reduce the geotechnical-related delays, rials may be far more gradual or abrupt than a report cost-overruns and other costly headaches that can indicates.Actual conditions in areas not sampled may occur during a construction project. differ from predictions. Nothing can be done to prevent the unanticipated, but steps can be taken to help minimize their A GEOTECHNICAL ENGINEERING impact. For this reason, most experienced owners retain their geotechnical consultants through the construction stage,to iden- REPORT IS BASED ON A UNIQUE SET tify variances,conduct additional tests which may be OF PROJECT-SPECIFIC FACTORS needed, and to recommend solutions to problems encountered on site. A geotechnical engineering report is based on a subsur- face exploration plan designed to incorporate a unique SUBSURFACE CONDITIONS set of project-specific factors. These typically include: the general nature of the structure involved, its size and CAN CHANGE configuration: the location of the structure on the site Subsurface conditions may be modified by constantly- and its orientation: physical concomitants such as changing natural forces. Because a geotechnical engi- access roads, parking lots, and underground utilities, neering report is based on conditions which existed at and the level of additional risk which the client assumed the time of subsurface exploration, construction decisions by virtue of limitations imposed upon the exploratory should not be based on a geotechnical engineering report whose program. To help avoid costly problems.consult the adequacy may have been affected by time. Speak with the geo- geotechnical engineer to determine how any factors technical consultant to learn if additional tests are which change subsequent to the date of the report may advisable before construction starts. affect its recommendations. Construction operations at or adjacent to the site and Unless your consulting geotechnical engineer indicates natural events such as floods, earthquakes or ground- otherwise. your geotechnical engineering report should not water fluctuations may also affect subsurface conditions be used: and, thus, the continuing adequacy of a geotechnical . When the nature of the proposed structure is report.The geotechnical engineer should be kept changed, for example, if an office building will be apprised of any such events,and should be consulted to erected instead of a parking garage. or if a refriger- determine if additional tests are necessary ated warehouse will be built instead of an unre- frigerated one: •when the size or configuration of the proposed GEOTECHNICAL SERVICES ARE structure is altered: PERFORMED FOR SPECIFIC PURPOSES •when the location or orientation of the proposed AND PERSONS structure is modified: .when there is a change of ownership, or Geotechnical engineers' reports are prepared to meet • for application to an adjacent site. the specific needs of specific individuals. A report pre- Geotechnical engineers cannot accept responsibility for problems pared for a consulting civil engineer may not be ade- which may develop if they are not consulted after factors consid- quate for a construction contractor,or even some other ered in their report's development have changed. consulting civil engineer. Unless indicated otherwise, this report was prepared expressly for the client involved and expressly for purposes indicated by the client. Use MOST GEOTECHNICAL "FINDINGS" by any other persons for any purpose, or by the client ARE PROFESSIONAL ESTIMATES fora different purpose, may result in problems. No indi- vidual other than the client should apply this report for its Site exploration identifies actual subsurface conditions intended pr. urpose per without first shouldon apply this reporth t fors geotechnical purpose only at those points where samples are taken, when other than that originallycontemplated without first conferring they are taken. Data derived through sampling and sub- with the eotechni al engineer sequent laboratory testing are extrapolated by geo- g Earth Consultants Inc. Grntt,c hnic iii Iiny(Inrrrs.G-1AogisLs&Fnvircaum•ntill S('i(-ntisti ,low. November 3, 1999 E-1990-20 Blackriver-Rivertech LLC c/o Alper Northwest 700 Fifth Avenue, Suite 6000 Seattle, Washington 98104 Attention: Dean Erickson Dear Mr. Erickson: We are pleased to submit our report titled "Geotechnical Engineering Study, Proposed Blackriver Corporate Park, Powell Avenue Southwest, Renton, Washington." This report presents the results of our field exploration, selective laboratory tests, and engineering analyses. The purpose and scope of our study was outlined in our September 17, 1999 proposal. Based on the results of our study, it is our opinion the project can be constructed generally �as planned. Building support may be provided using conventional spread and continuous foundation systems bearing on at least two feet of structural fill. Slab-on-grade floors may be supported on one foot of structural fill. We appreciate this opportunity to be of service to you. If you have any questions or if we can be of further assistance, please call. Respectfully submitted, EARTH CONSULTANTS, INC. ll� Kyle R. Campbell, P.E. Manager of Geotechnical Services KME/KRC/bkm 1805-136th Place N.E.,Suite 201,Bellevue,Washington 98005 Bellevue(425)643-3780 FAX(425)746-0860 Toil Free(888)739-6670 TABLE OF CONTENTS E-1990-20 PAGE INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Proiect Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 SITECONDITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Subsurface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Laboratory Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 DISCUSSION AND RECOMMENDATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Site Preparation and General Earthwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Retaining and Foundation Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Slab-on-Grade Floors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Seismic Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Excavations and Slopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Site Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Utility Support and Backfill : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 9 Pavement Areas 9 LIMITATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Additional Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 APPENDICES Appendix A Field Exploration Appendix B Laboratory Test Results ILLUSTRATIONS Plate 1 Vicinity Map Plate 2 Test Pit Location Plan Plate 3 Typical Footing Subdrain Detail Plate 4 Utility Trench Backfill Plate Al Legend Plates A2 through A5 Test Pit Logs Plate B1 Grain Size Analyses Earth Consultants, Inc. GEOTECHNICAL ENGINEERING STUDY PROPOSED BLACKRIVER CORPORATE PARK POWELL AVENUE SOUTHWEST RENTON, WASHINGTON E-1990-20 INTRODUCTION General This report presents the results of the geotechnical engineering study completed by Earth Consultants, Inc. (ECI) for the proposed Blackriver Corporate Park in Renton, Washington. The general location of the site is shown on the Vicinity Map, Plate 1 . The purpose of this study was to explore the subsurface conditions at the site and based on the conditions encountered to develop geotechnical recommendations for the proposed site development. Project Description We understand it is planned to develop the site with a one-story office building and associated parking. At the time our study was performed, the site, proposed building location and our exploratory locations were approximately as shown on the Test Pit Location Plan, Plate 2. 0 The proposed development will include asphalt-surfaced parking and driveway areas. We anticipate traffic will consist of passenger vehicles and occasional service and delivery trucks. If the above design criteria are incorrect or change, we should be consulted to review the recommendations contained in this report. In any case, ECI should be retained to perform a general review of the final design. SITE CONDITIONS Surface The subject site is located north and east of the north end of Powell Avenue Southwest (see Plate 1 , Vicinity Map). The site is approximately triangular in shape, extending about 1150 feet in the east-west direction and 420 feet in the north-south direction. The site is bordered on the west and south by commercial developments and on the northeast by wetlands and the Burlington Northern railroad tracks. The site is relatively flat. Site vegetation consists of blackberries and trees. Earth Consultants, Inc. GEOTECHNICAL ENGINEERING STUDY Blackriver-Rivertech LLC c/o Alper Northwest E-1990-20 November 3, 1999 Page 2 Subsurface Subsurface conditions were evaluated by excavating four test pits at the approximate locations shown on Plate 2. Please refer to the Test Pit Logs, Plates A2 through A5, for a more detailed description of the conditions encountered at each location explored. A description of the field exploration methods is included in Appendix A. The following is a generalized description of the subsurface conditions encountered. Our test pits indicate the site is immediately underlain by a four-inch thick layer of topsoil and rootmass. This soil unit is characterized by its brown to black color and the presence of organic material. This soil layer is not considered suitable for use in support of foundations, slabs-on-grade, or pavements. In addition, it is not suitable for use as a structural fill, nor should it be mixed with material to be used as structural fill. Underlying the topsoil in our test pits, we encountered eight to eleven feet of loose to medium dense silt, silty sand and sandy silt (Unified Classification ML, SM and ML) underlain by medium dense poorly graded sand to poorly graded gravel with sand (SP and GP). Groundwater Rapid groundwater seepage was encountered in our test pits at eight to eleven feet below the ground surface. The seepage appears to represent the groundwater table. The contractor should be made aware that groundwater is not static. There will be fluctuations in the level depending on the season, amount of rainfall, surface water runoff, and other factors. Generally, the water level is higher and seepage rate is greater in the wetter winter months (typically October through May). Laboratory Testing Laboratory tests were conducted on several representative soil samples to verify or modify the field soil classification and to evaluate the general physical properties and engineering characteristics of the soil encountered. Visual field classifications were supplemented by grain size analyses on representative soil samples. Moisture content tests were performed on all samples. The results of laboratory tests performed on specific samples are provided either at the appropriate sample depth on the individual boring logs or on a separate data sheet contained in Appendix B. It is important to note that these test results may not accurately represent the overall in-situ soil conditions. Our geotechnical recommendations are based on our interpretation of these test results and their use in guiding our engineering judgement. ECI cannot be responsible for the interpretation of these data by others. In accordance with our Standard Fee Schedule and General Conditions, the soil samples for • this project will be discarded after a period of fifteen days following completion of this report unless we are otherwise directed in writing. Earth Consultants, Inc. GEOTECHNICAL ENGINEERING STUDY Blackriver-Rivertech LLC c/o Alper Northwest E-1990-20 November 3, 1999 Page 3 DISCUSSION AND RECOMMENDATIONS General Based on the results of our study, it is our opinion the proposed development can be constructed generally as planned. Building support may be provided using conventional spread and continuous foundation systems bearing on at least two feet of structural fill. Slab- on-grade floors may be supported on one foot of structural fill. This report has been prepared for specific application to this project only and in a manner consistent with that level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area for the exclusive use of Blackriver-Rivertech LLC and their representatives. No warranty, expressed or implied, is made. This report, in its entirety, should be included in the project contract documents for the information of the contractor. Site Preparation and General Earthwork Based on the preliminary site plan, it appears site grading will consist of grading the site to provide a level building pad, installing underground utilities and grading the parking areas. The building and pavement areas should be stripped and cleared of surface vegetation, organic matter and other deleterious material. Existing utility pipes to be abandoned should be plugged or removed so that they do not provide a conduit for water and cause soil saturation and stability problems. Based on the thickness of the topsoil layer encountered at our test pit locations, we estimate a stripping depth of four inches. Deeper areas of stripping will be required to remove the larger root balls of the trees. Stripped materials should not be mixed with materials to be used as structural fill. Following the stripping, the ground surface where structural fill, foundations, or slabs are to be placed should be observed by a representative of ECI. Proofrolling may be necessary in order to identify soft or unstable areas. Proofrolling should be performed under the observation of a representative of ECI. Soil in loose or soft areas, if recompacted and still yielding, should be overexcavated and replaced with structural fill to a depth that will provide a stable base beneath the general structural fill. The optional use of a geotextile fabric placed directly on the overexcavated surface may help to bridge unstable areas. Earth Consultants, Inc. GEOTECHNICAL ENGINEERING STUDY Blackriver-Rivertech LLC c/o Alper Northwest E-1990-20 November 3, 1999 Page 4 0 The soils encountered during the site exploration are moisture sensitive due to their high fines content. As such, in an exposed condition, they will become disturbed from normal construction activity, especially when in a wet or saturated condition. Once disturbed, in a wet condition, they will be unsuitable for support of foundations, slabs or pavements. Therefore, during construction where these soils are exposed and will support new structures, care must be exercised not to disturb their condition. Consideration should be given to placement of rock or other methods to protect exposed native, undisturbed soils that will support foundations or new structural fill. If disturbed conditions develop, the affected soils must be removed and replaced with structural fill. The depth of removal will be dependent on the level of disturbance developed during construction. Given the above, a summer earthwork schedule is recommended. Structural fill is defined as compacted fill placed under buildings, roadways, slabs, pavements, or other load-bearing areas. Structural fill under floor slabs and footings should be placed in horizontal lifts not exceeding twelve (12) inches in loose thickness and compacted to a minimum of 90 percent of its laboratory maximum dry density determined in accordance with ASTM Test Designation D-1557-91 (Modified Proctor). The fill materials should be placed at or near their optimum moisture content. Fill under pavements and walks should also be placed in horizontal lifts and compacted to 90 percent of maximum density except for the top twelve (12) inches which should be compacted to 95 percent of maximum density. During dry weather, most soils which are compactible and non-organic can be used as structural fill. Based on the results of our laboratory tests, the native soils are generally over the optimum moisture content and will require moisture conditioning (drying out) prior to their use as structural fill. Based on laboratory testing, the native soil has between 30 and 43 percent fines passing the No. 200 sieve. Soil with fines in this range will degrade if exposed to excessive moisture, and compaction and grading will be difficult if the soil moisture increases significantly above its optimum condition. If the native soil cannot be adequately moisture conditioned and compacted then it may be necessary to import a soil which can be compacted. During dry weather, most non-organic compactible soil with a maximum particle size of six inches can be used. Fill for use during wet weather should consist of a fairly well graded granular material having a maximum particle size of six inches and no more than five percent fines passing the No. 200 sieve based on the minus 3/4-inch fraction. A contingency in the earthwork budget should be included for this possibility. Earth Consultants, Inc. GEOTECHNICAL ENGINEERING STUDY Blackriver-Rivertech LLC c/o Alper Northwest E-1990-20 November 3, 1999 Page 5 Foundations Based on the results of our study, it is our opinion the proposed building may be supported on a conventional spread and continuous footing foundation bearing on at least two feet of structural fill. For frost protection considerations, exterior foundation elements should be placed at a minimum depth of eighteen (18) inches below final exterior grade. Interior spread foundations can be placed at a minimum depth of twelve (12) inches below the top of slab, except in unheated areas, where interior foundation elements should be founded at a minimum depth of eighteen (18) inches. With foundation support obtained as described, for design, an allowable bearing capacity of two thousand five hundred (2,500) psf for structural fill can be used. Continuous and individual spread footings should have minimum widths of eighteen (18) and twenty-four (24) inches, respectively. Loading of this magnitude would be provided with a theoretical factor- of-safety in excess of three against actual shear failure. For short-term dynamic loading conditions, a one-third increase in the above allowable bearing capacities can be used. With structural loading as expected, total settlement in the range of one inch is anticipated with differential movement of about one-half inch. Most of the anticipated settlements should occur during construction as dead loads are applied. Horizontal loads can be resisted by friction between the base of the foundation and the supporting soil and by passive soil pressure acting on the face of the buried portion of the foundation. For the latter, the foundation must be poured "neat" against the competent native soils or backfilled with structural fill. For frictional capacity, a coefficient of .35 can be used. For passive earth pressure, the available resistance can be computed using an equivalent fluid pressure of three hundred (300) pcf. These lateral resistance values are allowable values, a factor-of-safety of 1 .5 has been included. As movement of the foundation element is required to mobilize full passive resistance, the passive resistance should be neglected if such movement is not acceptable. Footing excavations should be observed by a representative of ECI, prior to placing forms or rebar, to verify that conditions are as anticipated in this report. Earth Consultants. Inc. GEOTECHNICAL ENGINEERING STUDY Blackriver-Rive rtech LLC c/o Alper Northwest E-1990-20 November 3, 1999 Page 6 Retaining and Foundation Walls Retaining walls and foundation walls that act as retaining walls should be designed to resist lateral earth pressures imposed by the retained soils. Walls that are designed to yield can be designed to resist the lateral earth pressures imposed by an equivalent fluid with a unit weight of thirty-five (35) pcf. If walls are to be restrained at the top from free movement, the equivalent fluid weight should be increased to fifty (50) pcf. These values are based on horizontal backfill and that surcharges due to backfill slopes, hydrostatic pressures, traffic, structural loads or other surcharge loads will not act on the wall. If such surcharges are to apply, they should be added to the above design lateral pressure. The passive pressure and friction coefficients previously provided in the Foundations section are applicable to retaining walls. For calculating the base resistance to sliding, the passive pressure and friction coefficient provided in the Foundations should be used. In order to reduce the potential for hydrostatic forces building up behind the walls, retaining walls should be backfilled with a suitable free-draining material extending at least eighteen (18) inches behind the wall. The remainder of the backfill should consist of structural fill. The free-draining backfill should conform to the WSDOT specification for gravel backfill for walls (WSDOT 9-03.12(2)). A perforated drainpipe should be placed at the base of the wall and should be surrounded by a minimum of one cubic foot per lineal foot with three-eighths inch pea gravel. Slab-on-Grade Floors Slab-on-grade floors may be supported on one foot of structural fill. Disturbed subgrade soil must either be recompacted or replaced with structural fill. Concrete slabs resting on soil ultimately cause the moisture content of the underlying soils to rise. This results from continued capillary rise and the ending of normal evapotranspiration. As concrete is permeable, moisture will eventually penetrate the slab resulting in a condition commonly known as a "wet slab" and poor adhesion of floor coverings. Therefore, the slab should be provided with a minimum of four inches of free-draining sand or gravel. In areas where slab moisture is undesirable, a vapor barrier such as a 6-mil plastic membrane may be placed beneath the slab. Two inches of damp sand may be placed over the membrane for protection during construction and to aid in curing of the concrete. Seismic Design Considerations The Puget Lowland is classified as a Seismic Zone 3 in the 1994 Uniform Building Code (UBC). Earthquakes occur in the Puget Lowland with regularity, however, the majority of these events are of such low magnitude they are not detected without instruments. Large earthquakes do occur, as indicated by the 1949, 7.1 magnitude earthquake in the Olympia area and the 1965, 6.5 magnitude earthquake in the Midway area. Earth Consultants, Inc. GEOTECHNICAL ENGINEERING STUDY Blackriver-Rivertech LLC c/o Alper Northwest E-1990-20 November 3, 1999 Page 7 There are three potential geologic hazards associated with a strong motion seismic event at this site: ground rupture, liquefaction, and ground motion response. Ground Rupture: The strongest earthquakes in the Puget Lowland are widespread, subcrustal events, ranging in depth from thirty (30) to fifty-five (55) miles. Surface faulting from these deep events has not been documented to date. Therefore, it is our opinion, that the risk of ground rupture during a strong motion seismic event is negligible. Liquefaction: Liquefaction is a phenomenon in which soils lose all shear strength for short periods of time during an earthquake. Groundshaking of sufficient duration results in the loss of grain to grain contact and rapid increase in pore water pressure, causing the soil to behave as a fluid. To have a potential for liquefaction, a soil must be cohesionless with a grain size distribution of a specified range (generally sands and silt); it must be loose to medium dense; it must be below the groundwater table; and it must be subject to sufficient magnitude and duration of groundshaking. The effects of liquefaction may be large total and/or differential settlement for structures founded in the liquefying soils. The soils encountered on-site in the top eight to eleven (1 1 ) feet would be subject to liquefaction if saturated. The water table at the time of our explorations was eight to eleven 0 (1 1 ) feet below grade at the interface between the loose to medium dense silts and sands and the sand and gravel layer. Isolated areas may be subject to liquefaction, however, the effect on the planned development is anticipated to be minimal provided the recommendations contained in this report are followed. We estimate liquefaction induced settlement would be in the range of the post- constructed settlements discussed earlier. Ground Motion Response: In accordance with Table 16-J of the 1997 UBC, soil type Sp should be used in design. Excavations and Slopes The following information is provided solely as a service to our client. Under no circumstances should this information be interpreted to mean that ECI is assuming responsibility for construction site safety or the contractor's activities; such responsibility is not being implied and should not be inferred. In no case should excavation slopes be greater than the limits specified in local, state and Federal safety regulations. Based on the information obtained from our field exploration and laboratory testing, the native soil would be classified as Type C by OSHA. Temporary cuts greater than four feet in height in Type C soils should be sloped at an inclination of 1 .5H:1 V. If slopes of this inclination, or flatter, cannot be constructed, temporary shoring may be necessary. Earth Consultants, Inc. GEOTECHNICAL ENGINEERING STUDY Blackriver-Rivertech LLC c/o Alper Northwest E-1990-20 November 3, 1999 Page 8 Shoring will help protect against slope or excavation collapse, and will provide protection to workers in the excavation. If temporary shoring is required, we will be available to provide shoring design criteria. Permanent cut and fill slopes should be inclined no steeper than 2H:1 V. Cut slopes should be observed by ECI during excavation to verify that conditions are as anticipated. Supplementary recommendations can then be developed, if needed, to improve stability, including flattening of slopes or installation of surface or subsurface drains. In any case, water should not be allowed to flow uncontrolled over the top of slopes. Permanently exposed slopes should be seeded with an appropriate species of vegetation to reduce erosion and improve stability of the surficial layer of soil. Site Drainage Rapid groundwater seepage was encountered in our test pits at depths ranging from eight to eleven (1 1 ) feet below the existing ground surface. Due to the rapid nature of the seepage and the caving associated with the seepage, excavations in excess of eight feet will be 0 difficult or impossible without shoring and/or dewatering. If seepage is encountered in foundation or grade beam excavations during construction, the bottom of the excavation should be sloped to one or more shallow sump pits. The collected water can then be pumped from these pits to a positive and permanent discharge, such as a nearby storm drain. Depending on the magnitude of such seepage, it may also be necessary to interconnect the sump pits by a system of connector trenches. The appropriate locations of subsurface drains, if needed, should be established during grading operations by ECI's representative at which time the seepage areas, if present, may be more clearly defined. During construction, the site must be graded such that surface water is directed off the site. Water must not be allowed to stand in areas where buildings, slabs or pavements are to be constructed. Loose surfaces should be sealed at night by compacting the surface to reduce the potential for moisture infiltration into the soils. Final site grades must allow for drainage away from the building foundations. The ground should be sloped at a gradient of three percent for a distance of at least ten feet away from the buildings, except in paved areas, which can be sloped at a gradient of two percent. Footing drains should be installed around the building perimeters, at or just below the invert of the footing, with a gradient sufficient to initiate flow. A typical detail is provided on Plate 3. Earth Consuttants, Inc. GEOTECHNICAL ENGINEERING STUDY Blackriver-Rivertech LLC c/o Alper Northwest E-1990-20 November 3, 1999 Page 9 Under no circumstances should roof downspout drain lines be connected to the footing drain system. Roof downspouts must be separately tightlined to discharge. Cleanouts should be installed at strategic locations to allow for periodic maintenance of the footing drain and downspout tightline systems. Utility Support and Backfill Based on the soil conditions encountered, the soils expected to be exposed by utility excavations should provide adequate support for utilities provided excavations are limited to eight feet. Utility trench backfill is a primary concern in reducing the potential for settlement along utility alignments, particularly in pavement areas. It is important that each section of utility line be adequately supported in the bedding material. The material should be hand tamped to ensure support is provided around the pipe haunches. Fill should be carefully placed and hand tamped to about twelve inches above the crown of the pipe before heavy compaction equipment is brought into use. The remainder of the trench backfill should be placed in lifts having a loose thickness of less than twelve inches. A typical trench backfill section and compaction requirements for load supporting and non-load supporting areas is presented on Plate 4. Pavement Areas The adequacy of site pavements is related in part to the condition of the underlying subgrade. To provide a properly prepared subgrade for pavements, the subgrade should be treated and prepared as described in the Site Preparation and General Earthwork section of this report. This means at least the top twelve (12) inches of the subgrade should be compacted to 95 percent of the maximum dry density (per ASTM D-1557-91). It is possible that some localized areas of soft, wet or unstable subgrade may still exist after this process. Therefore, a greater thickness of structural fill or crushed rock may be needed to stabilize these localized areas. The following pavement section for lightly-loaded areas can be used: • Two inches of asphalt concrete (AC) over four inches of crushed rock base (CRB) material, or • Two inches of AC over three inches of asphalt treated base (ATB) material. Earth Consultants, Inc. GEOTECHNICAL ENGINEERING STUDY Blackriver-Rivertech LLC c/o Alper Northwest E-1990-20 November 3, 1999 Page 10 Heavier truck-traffic areas will require thicker sections depending upon site usage, pavement life and site traffic. As a general rule, the following sections can be considered for truck- trafficked areas: • Three inches of AC over six inches of CRB, or • Three inches of AC over four and one-half inches of ATB. We will be pleased to assist in developing appropriate pavement sections for heavy traffic zones, if needed. Pavement materials should conform to WSDOT specifications. The use of a Class B asphalt mix is suggested. LIMITATIONS Our recommendations and conclusions are based on the site materials observed, selective laboratory testing and engineering analyses, the design information provided us, and our experience and engineering judgement. The conclusions and recommendations are professional opinions derived in a manner consistent with that level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area. No warranty is expressed or implied. The recommendations submitted in this report are based upon the data obtained from the test pits. Soil and groundwater conditions between test pits may vary from those encountered. The nature and extent of variations between our exploratory locations may not become evident until construction. If variations do appear, ECI should be requested to reevaluate the recommendations of this report and to modify or verify them in writing prior to proceeding with the construction. Additional Services As the geotechnical engineer of record, ECI should be retained to perform a general review of the final design and specifications to verify that the earthwork and foundation recommendations have been properly interpreted and implemented in the design and in the construction specifications. ECI should also be retained to provide geotechnical services during construction. This is to observe compliance with the design concepts, specifications or recommendations and to allow design changes in the event subsurface conditions differ from those anticipated prior to the start of construction. We do not accept responsibility for the performance of the foundation or earthwork unless we are retained to review the construction drawings and specifications, * and to provide construction observation and testing services. Earth Consultants, Inc. �! _dill �•�J�3 �. ?�J..... .. t I � .: lrg'8L^! /cj lc�i �r 1 �1 C, 'z tt72'CTN .�ir i tii'H ✓ �T �a .�Y >S11 7r r I z i r�ram",= RflrTCr� ' _., ram' AIR ORT WY r sr N 2 ST '' uas, Il?Ic' 4" p yl c llC�t �ST T tag \F. r c rt d•x C rr(n�[r _T �1 \� �~ � M QIS VE..TCRI'' t Dt f5.'...av! F, j; 41tCi7q.A T �� 5'T FA Tn� 4s -�Qrrr 1 �`� 8 Rrntr�,v r �' T I ��' etrn Sr r nr r'� �\~�W J_I- v L___--� C vti' f7S vi( Le)14 s .' .fir '� __ .� zrr• Ise -� � , j f, J ! rto y��'o F� P� �`-`-` ry� Ya�K[-. -SGKtc �'�� N f�. FS ;�' ■ nl \?` ��I l.Y tdJW�� C 1fT`w N. •�• i vti J 3RD 1i IrfiS( �wc 1 '�ria� r Rigx t �` S • 1:D A` f A i _ 5+lj ai?! SUN-?, -��1 S ::j L�{; a N I .`-o�j � I L13 rKllt• T i ! x I C•" f FA; -J i 5T I S4'SrK CT �7 �� fRFI1 n sal v l "K a x rrly F 1 V yam. McYER 5 41 $' w 5TH' ST t�` 70 G •�CENTER� yn �SITTE` 1 �.�-siy. �ti RR ¢TH S'T�'h - SW ra 7TN r.,• �� L u o r z P.I RiC l,D\� F•t $ RrOF G� � VrcAGE UJ� CEtVTER ton y c u 1Q �,�'t AY S R i tl VILLAGE FL = `j {' 12 HUIL14Y 1 n SW o�l 13 2 `� 'fit' Vi d rt 1 /Uxf srhi { get s15TH ;' w�'' ❑2 PAN S=: 16TH ST SW ST C{� r _ 4 16TN '' T S I If ST , s' 11 S SW 1991H ST ,9 n v,ll ST=�r7m ys 4 t t 1,; S �QTN v...ST h ztrcnr E Earth Consultants, Inc. Reference: Geotechnical Engineers.Geologists&Environmental Scientists Puget Sound (King) / Map 656 By Thomas Brothers Maps Vicinity Map Dated 2000 Blackriver Corporate Park Renton, Washington NOTE: This plate may contain areas of color. ECI cannot be responsible for any subsequent Drwn. GLS Date Oct. '99 Proj. No. 1990-20 misinterpretation of the information resulting from black &white reproductions of this plate. Checked KMW Date 10/15/99 Plate 1 i t � // II / Approximate Scale / 0 80 160 320ft. t C- Natural Area LEGEND r / U �= TP-1 — —Approximate Location of ECI Test Pit, Proj. No. r s t E-1990-20 Oct. 1999 Existing r 2 / - TP 1 1 s4�ts� I Drainage c �o Swale Subject Site TP-2 10, Proposed Building Existing Wetland Area - —■— �" '• (per Referenced Plan � _TP-3 Limits of Existing Road r' POWELL ---- ' AVE. S.W. Proposed Road / Parking Areas Reference: Existin Sheet No. A-1 g Biofi@ratan Job No. 99008 z- Drainage i Swale Site Plan & Site Section By LPN Architects and Planners _t_ _ Dated 7/29/99 f ,--------- t Earth Consultants, Inc. Geotechnical Engineers,Geologists&Environmental scientists NOTE: This plate may contain areas of color. Test Pit Location Plan ECI cannot be responsible for any subsequent Blackriver Corporate Park misinterpretation of the information resulting Renton, Washington from black& white reproductions of this plate. Drwn. GLS Date Oct. '99 Proj. No. 1990-20 Checked KMW Date 10/15/99 Plate 2 0 o � so , Slope To Drain ° inch min. ° o o ° .�'.:o 'v.•�. ° °. 18 inch min. o _ _ .�- - .• a• 'ice• o .o 0 4 inch min. '•'' `°- •'� _ - •'�_�.°�:_o:•� `I ° `�°'o Diameter Perforated Pipe Wrapped in Drainage Fabric ' 1I ,-•a. 1 •a 2 inch min. 2 inch min. / 4 inch max. 12 inch min. SCHEMATIC ONLY - NOT TO SCALE NOT A CONSTRUCTION DRAWING LEGEND Surface seal; native soil or other low permeability material. Fine aggregate for Portland Cement Concrete; Section 9-03.1(2) of the WSDOT Specifications. O Drain pipe; perforated or slotted rigid PVC pipe laid with perforations or slots facing down;tight jointed;with a positive gradient. Do not use flexible corrugated plastic pipe. Do not tie building downspout drains into footing lines. Wrap with Mirafi 140 Filter Fabric or equivalent. TYPICAL FOOTING SUBDRAIN DETAIL Earth Consultants Inc. Blackriver Corporate Park Ktv calEngyw'CrsceoboALusd Fmitr rnmwlsci niis+s Renton, Washington 7P7( oj. No.1990-20 Drwn. GLS Date Od. '99 Checked KMW Date 10/15/99 Plate 3 Non-Load Supporting Floor Slab or Areas Roadway Areas ° Varies �o°oo0°0 95 a ° 0. o p o 0 85 95 1 Foot Minimum Back-fill 80 90 Varies 0 0' PIPE �° 0000 .o O •0 4°0 �'O.o•oao, ooaoa.a °.ObO ;• b.•o . Bedding •.'Q'° oe C • ° Varies o o..ao.. O.o'•o0 00• . oo Oo • o.• O;oO000Oa oo pOup o�oD0. O0000'00•°0�00 .•.00:•ooa:o°0•0°•0��•°o�.0oa��oa�°•o°�a� LEGEND: . Asphalt or Concrete Pavement or Concrete Floor Slab Base Material or Base Rock Backfill; Compacted On-Site Soil or Imported Select Fill Material as Described in the Site Preparation of the General Earthwork Section of the Attached Report Text. 95 Minimum Percentage of Maximum Laboratory Dry Density as Determined by ASTM Test Method D 1557-78 (Modified Proctor), Unless Otherwise Specified in the Attached Report Text. Bedding Material; Material Type Depends on Type of Pipe and °:0.�oo;p Laying Conditions. Bedding Should Conform to the Manufacturers Recommendations for the Type of Pipe Selected. TYPICAL UTILITY TRENCH FILL III I Earlh Consultants Inc. Blackriver Corporate Park >.>,,fi„K,�„a„.•�.�. ,w u.,. �;.;,,�,,,�,,,, ,,, , Renton, Washington Proj. No. 1990-20 Drwn. GLS Date Oct. '99 Checked KMW Date 10/15/99 Plate 4 APPENDIX A FIELD EXPLORATION E-1990-20 Our field exploration was performed on October 12, 1999. Subsurface conditions at the site were explored by excavating four test pits to a maximum depth of twelve (12) feet below the existing grade. The test pits were excavated by Five Ball Construction subcontracted to ECI, using a track mounted excavator. Approximate test pit locations were determined by pacing from site features. The locations of the test pits should be considered accurate only to the degree implied by the method used. These approximate locations are shown on the Test Pit Location Plan, Plate 2. The field exploration was continuously monitored by a engineer from our firm who classified the soils encountered, maintained a log of each test pit, obtained representative samples, measured groundwater levels, and observed pertinent site features. Samples were visually classified in accordance with the Unified Soil Classification System which is presented on Plate Al , Legend. Representative soil samples were placed in closed containers and returned to our laboratory for further examination and testing. Test Pit Logs are presented on Plates A2 through A5. The final logs represent our interpretations of the field logs and the results of the laboratory tests of field samples. The stratification lines on the logs represent the approximate boundaries between soil types. In actuality, the transitions may be more gradual. The consistency of the soil shown on the logs was estimated based on the effort required to excavate the soil, the stability of the trench walls, and other factors. Earth Consultants, Inc. GRAPH LETTER TYPICAL DESCRIPTION MAJOR DIVISIONS SYMBOL SYMBOL GW Well-Graded Gravels, Gravei-Sand Gravel d ° d ° d ° gW Mixtures, Little Or No Fines And Clean Gravels Gravelly (little or no fines) GP Poorly-Graded Gravels,Gravel- Coarse Soils ' ' ' gP Sand Mixtures, Little Or No Fines Grained Soils More Than GM Silty Gravels,Gravel-Sand- 50°% Coarse Gravels With gm Silt Mixtures Fraction Fines(appreciable Retained On amount of fines) GC Clayey Gravels, Gravel-Sand- No. 4 Sieve gC Clay Mixtures o SW Well-Graded Sands, Gravelly Sand SW Sands, Little Or No Fines And Clean Sand ° o ' ° o Sandy (little or no fines) '17. Graded Sands, Gravel) > SP Poorly- Y More Than Soils <.>q>.;�;,: S Sands, Little Or No Fines 50% Material " "' "`'a"' P No. 200 Sieve 50% Coarse SfTI Silty Sands, Sand- Silt Mixtures Larger Than More Than SNI Size Sands With Fraction Fines(appreciable RINI], Passing No.4 amount of fines) SC Clayey Sands, Sand-Clay Mixtures Sieve SC ML Inorganic Silts&Very Fine Sands,Rock Flour,Silty- ml Clayey Fine Sands;Clayey Silts w/ Slight Plasticity Fine Silts Inorganic Clays Of Low To Medium Plasticity, Liquid Limit CL Grained And Less Than 50 CI Gravelly Clays, Sandy Clays, Silty Clays, Lean Soils Clays jOrganic Silts And Organic CL o1 Silty Clays Of Low Plasticity I MH Inorganic Silts, Micaceous Or Diatomaceous Fine. More Than mh Sand Or Silty Soils 501/, Material Silts Liquid Limit CH Inorganic Clays Of High Smaller Than And Greater Than 50 No.200 Sieve Clays CFl Plasticity, Fat Clays Size OLI Organic Clays Of Medium To High Oh Plasticity, Organic Silts PT Peat, Humus, Swamp Soils Highly Organic Soils II 11 Pt With High Organic Contents Topsoil y \L y Humus And Duff Layer Fill Highly Variable Constituents The discussion in the text of this report is necessary for a proper understanding of the nature of the material presented in the attached logs. DUAL SYMBOLS are used to Indicata borderline soil classification. C TORVANE READING,tsf 2- O.D. SPLIT SPOON SAMPLER qu PENETROMETER READING,tsf W MOISTURE, %dry weight 24' I.D. RING OR SHELBY TUBE SAMPLER P SAMPLER PUSHED SAMPLE NOT RECOVERED WATER OBSERVATION WELL pcf DRY DENSITY, lbs. per cubic ft. LL LIQUID LIMIT, % SL DEPTH OF ENCOUNTERED GROUNDWATER PI PLASTIC INDEX EXCAVATION I SUBSEQUENT GROUNDWATER LEVEL W/DATE Earth Consultants Inc. LEGEND ti \.) 11/�i �) <4vici lu,ii al l!nbin.cn,(�nlugi�sS bnaln�uiwni.,luuniu�� Proj. Nol990-2 11 Date Oct. '99 TPlate Al Test Pit Log Project Name: Sheet of Blackdver Corporate Park 1 1 Job No. Logged by: Date: Test Pit No.: 1990-20 KMW 10/12/99 TP-1 Excavation Contactor: Ground Surface Elevation: Five Ball Notes: o L �, o Surface Conditions: Depth of Topsoil 4" General W a u E co Notes (°6) o cn SM Brown silty SAND, medium dense, moist 17.0 2 -30%fines 3 ML Reddish brown SILT, medium dense, moist 4 46.1 5 s ML Gray sandy SILT, loose,wet 7 35.2 8 -caving s SP Gray poorly graded SAND with gravel, medium dense,water bearing as 0 10 Test pit terminated at 10.0 feet below existing grade. Rapid groundwater seepage encountered at 8.0 feet dunng excavation. m r (V O_ F (7 U W a Test Pit Log Earth ConsultW-ItS II1C. Blackriver Corporate Park G�xcvy cilia)F�i.hirc-iS.G-.Mcri.�r�&Flt�i�cv ii�•.r+ir,�lYhi�l�'� o - Renton,Washington Proj. No. 1990-20 Dwn. GLS Date Oct. '99 Checked KMW Date 10/25/99 Plate AZ Subsurface conditions depicted represent our observations at the time and location of this exploratory hole,modified by engineering tests,analysis and judgment. They are not necessarily representative of other times and locations.We cannot accept responsibility for the use or interpretation by others of information presented on this log. Test Pit Log heet of Project Name: S Blackriver Corporate Park 1 1 Job No. Logged by: Date: Test Pit No.: 1990-20 KMW 10/12/99 TP-2 Ground Surface Elevation: Excavation Contactor: Five Ball Notes: Surface Conditions: Depth of Toposil 4" General W @ E u- E (0 E Notes (°,6) a in Z ML Brown sandy SILT, medium dense, moist 2 40.3 ffi 3 MUSM Interbedded reddish brown SILT,sandy SILT and silty fine SAND, medium dense, moist 4 5 29.3 6 7 8 9 : M Gray silty SAND, loose,wet 10 -caving 11 SP Reddish brown poorly graded GRAVEL with sand, medium dense, 7.6 water bearing ° 12 ° Test pit terminated at 12.5 feet below existing grade. Rapid groundwater seepage encountered at 1.0 feet during excavation. N O_ U W a Test Pit Log Earth l Consultw-ItS Inc. Blackriver Corporate Park C7 ' Gc:or�vimk:a�F1,R,nec, .G-nkrzLv�A.Fl,v1'c,�,i,•.r.,,n,��w'trc,it+1 Renton,Washington IL W Proj.No. 1990-20 Dwn. GLS Date Oct. '99 Checked KMW Date 10/25/99 Plate A3 ~Subsurface conditions depicted represent our observations at the time and location of this exploratory hole,modified by engineering tests,analysis and judgment. They are not necessarily representative of other times and locations.We cannot accept responsibility for the use or interpretation by others of information presented on this log. Test Pit Log of Project Name: Sheet 1 1 Blackriver Corporate Park 1 Job No. Logged by: Date: Tess Pit No.: 10/1 /991990-20 KMW 2 TP-3 Excavation Contactor: Ground Surface Elevation: Five Ball Notes: U O L U) o Surface Conditions: Depth of Topsoil 4" General W v r .n _ o_ n Notes (°6) o " N U) ML Brown sandy SILT, medium dense, moist 39.6 2 3 SM/ML Interbedded brown silty fine SAND and sandy SILT, medium dense, moist 4 23.9 5 6 -43%fines -caving o $ SP Gray poorly graded SAND, medium dense,water bearing 9 o , o 0 '0 6 34.6 0 °a'o� 10 -grades with gravel 0 11 Test pit terminated at 11.0 feet below existing grade. Rapid groundwater seepage encountered at 10.0 feet during excavation. it N O C- C7 U W a Test Pit Log Earth Consultants Inc. Blackriver Corporate Park p �� -tIII Fn)_- -is.G[ gius Renton,Washington FProj. No. 1990-20 Dwn. GLS Date Oct. '99 Checked KMW Date 10/25/99 Plate A4 subsurface conditions depicted represent our observations at the time and location of this exploratory hole,modified by engineering tests,analysis and judgment. They are not necessarily representative of other times and locations.We cannot accept responsibility for the use or interpretation by others of information presented on this log. Test Pit Log Project Name: Sheet of Blackriver Corporate Park 1 1 Job No. Logged by: Date: Test Pit No.: 1990-20 KMW 10/12/99 TP-4 Excavation Contactor: Ground Surface Elevation: Five Ball Notes: U d o Surface Conditions: Depth of Topsoil 4" General W a E u.. E u) E Notes (%) cn p rn ML Brown SILT, medium dense, moist 1 2 31.6 3 4 5 6 7 SM Reddish brown silty SAND, loose, moist 11.1 8 9 -severe caving 10 SP Gray poorly graded SAND, medium dense,water bearing 0 11 28.6 ° 12 Test pit terminated at 12.0 feet below existing grade. Groundwater seepage encountered at 11.0 feet during excavation. m N O H Q U W a Test Pit Log Earth Consultants Inc. Blackriver Corporate Paris U C�xc�'tu�h�dl F�rZhire-r;.Gc-!Nn3I.v>&F�rvl;nfin.riir,il�.Yrtin_�� o Renton,Washington Proj.No. 1990-20 1 Dwn. GLS Date Oct. '99 Checked KMW Date 10/25/99 Plate A5 Subsurface conditions depicted represent our observations at the time and location of this exploratory hole,modified by engineering tests,analysis and judgment. They are not necessarily representative of other times and locations.We cannot accept responsibility for the use or interpretation by others of information presented on this log. w APPENDIX B LABORATORY TEST RESULTS E-1990-20 • Earth Consultants, Inc. SIEVE ANALYSIS HYDROMETER ANALYSIS SIZE OF OPENING IN INCHES NUMBER OF MESH PER INCH U.S.STANDARD GRAIN SIZE IN MccM�� O 0 O ,..0 M N O �• N V a m N m p tD O O O 0In 0 000 0 p O O O p 0 O O O O Q O z 100 \ O i`Z — � 10 90 CD 1 1 Cp 20 o � so m m 7 T, 30 Y m 70 m O ao - T_ GO7. 50 50 (n d co m CD1A 4 m (n 60 40 co n m -� ? n 70 30 m IF G� (•) 80 .{ � 20 _ n CD 90 n 10 _ t 100 C tD (D x0 0 O O O °D '11 I O O ri DO O O O O O CO lD V M N r O O O O O O O rT H. D M IN SIZE IN MILLIMETERS J n z COARSE FINE COARSE MEDIUM FINE FINES CD rn COBBLES GRAVEL SAND r C7 N CDcn n m Moisture LL PL N N o D Boring or DEPTH DESCRIPTION v� I � ZD KEY Test Pit No. ft. USCS Content (%) � rt rt 0 m17.0 w rm p TP-1 2 SM Brown silty SAND m 23 CD p--- TP-3 4 SP•1 Brown silty SAND --- --- x DISTRIBUTION E-1990-20 4 Copies Blackriver-Rivertech LLC c/o Alper Northwest 700 Fifth Avenue, Suite 6000 Seattle, Washington 98104 Attention: Mr. Dean Erickson 2 Copies LPN Architecture and Planning 1535 Fourth Avenue South, Suite D Seattle, Washington 98134 Attention: Mr. Royce Berg Earth Consultants, Inc.