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HomeMy WebLinkAboutGeoTechnical Assessment - GEO General - 2/14/2005 �,� s Geotechnical Assessment Corbitt Commercial 24943 NE State Route 3 Belfair, WA Prepared for e Jack and Steve Johnson by Geotechnical Testing Laboratory Olympia, Washington February 14, 2005 GEOTECHNICAL TESTING LABORATORY .TACK AND STEVE JOHNSON P. O. BOX 1119 BELFAIR,WA 98528 RE: GEOLOGICAL ASSESSMENT CORBITT COmmiRCIAL PROJECT 24943 NE STATE ROUTE 3 BELFAIR,WA PARCEL123213400020 N47027.883' W 122°48.882' As per your request, we have conducted a soils exploration and foundation evaluation for the above referenced property. The objective of the geological assessment is to assess the surface and subsurface conditions prevalent at the subject site according to Mason County Ordinance 17.01.100.E4. The results of this investigation, together with our recommendations, are to be found in the following report. We have provided three copies for your review and distribution. During our exploration, soil samples were collected for laboratory testing from the project site. The data has been carefully analyzed to determine soils bearing capacities and footing embedment depths. The results of the exploration and analysis indicate that conventional spread footings appear to be the most suitable type of foundation for the support of the proposed structures. Some variability was encountered in comparing the soil profiles of the site. Net allowable soil pressures, embedment depth, and total expected settlements have been presented for the site later in the report. Often, because of design and construction details that occur on a project, questions arise concerning soil conditions. We would be pleased to continue our role as geotechnical consultants or provide testing services during the project implementation. We appreciate this opportunity to be of service to you and we look forward to working with you in the future. If you have any questions concerning the test results, the procedures used, or if we can be of any further assistance please call on us at (360)754-4612. �a pt a$ ' >� Respectfully Submitted, �O GEOTECHNICAL TESTING LABORATORY O Harold Parks, L.G., L.E.G. eq$ed Ggo�p Senior Engineering Geologist HAROLD PARKS LXP -7 —3 s' 10011 Blomberg Street SW,Olympia,WA 98512 1 Phone#: (360)754-4612 Fax#: (360)754-4848 G EOTECHNICAL TESTING LABORATORY TABLE OF CONTENTS SUBSURFACE INVESTIGATION Subsurface Investigation 3 Introduction: 3 Authorization: 3 Purpose: 3 General: 3 Geology Of Area: 4 Climate Of Area: 5 FIELD EXPLORATION 5 General Notes: 5 Drilling&Sampling Procedures: 6 PROJECT DESCRIPTION, 6 SUBSURFACE CONDITIONS 7 Description Of Foundation Materials: 7 SLOPE STABILITY 8 EROSION CONTROL 9 TREE REMOVAL 9 SUMMARY 10 GEOTECHNICAL GENERAL NOTES 12 Soil Property Symbols 12 Drilling And Sampling Symbols 12 Relative Density And Consistency Classification 12 Particle Size 12 10011 Blomberg Street SW,Olympia, WA 98512 2 Phone#: (360)754-4612 Fax#: (360)754-4848 GEOTECHNICAL TESTING LABORATORY SUBSURFACE INVESTIGATION INTRODUCTION: This report presents the results of a geological assessment for the Corbitt Commercial Project west of State Route 3 approximately 1 mile north-northeast of Belfair, WA. This investigation was conducted for Jack and Steve Johnson. AUTHoRaAnom Authorization to perform this exploration and analysis was in the form of a verbal authorization to proceed from Jack Johnson. PURPOSE: The purpose of this foundation exploration and analysis was to determine the various soil profile components, the engineering characteristics of the foundation materials, and to provide criteria for use by the design engineers and architects in preparing or verifying the suitability of the foundation design and to satisfy the requirements of the Mason County Critical Areas Ordinance. Geotechnical Testing Laboratory is therefore providing geologic and hydrogeologic services for the project. Specifically, our scope of services for this project will include the following: 1. Review the available geologic, hydrogeologic and geotechnical data for the site area. 2. Conduct a geologic reconnaissance of the site area. 3. Evaluate the erosion hazards at the site per the Mason County Critical Areas Ordinance regulations. 4. Provide geotechnical recommendations for site grading including site preparation, subgrade preparation, fill placement criteria(including hillside grading), suitability of onsite soils for use as structural fill, temporary and permanent cut and fill slopes, drainage and erosion control measures. 5. Provide recommendations and design criteria for the structural foundation and floor slab support, including allowable bearing capacity, subgrade modulus, lateral resistance values and estimates of settlement. 6. Provide recommendations and design criteria for design of conventional subgrade/retaining walls, including backfill and drainage requirements, lateral design loads, and lateral resistance values. GENERAL: The exploration and analysis of the foundation conditions reported herein are considered sufficient in detail and scope to form a reasonable basis for the foundation design. Any revision in the plans for the proposed structure from those enumerated in this report should be brought to the attention of the soils consultant so that he may determine if changes in the foundation recommendations are required. If deviations from the noted subsurface conditions are encountered during construction, they should also be brought to the attention of the soils consultant. The soils consultant warrants that the findings, recommendations, specifications, or professional advice contained herein, have been promulgated after being prepared according to generally accepted professional engineering practice in the fields of foundation engineering, soil mechanics and engineering geology. No other warranties are implied or expressed. 10011 Blomberg Street SW,Olympia,WA 98512 3 Phone#: (360)754-4612 Fax#: (360)754-4848 G EOTECHNICAL TESTING LABORATORY This report has been prepared for the exclusive use of Jack and Steve Johnson and their retained design consultants. Findings and recommendations within this report are for specific application to the proposed project. All recommendations are according to generally accepted soils and foundation engineering practices. GEOLOGY OF AREA: The Soil Survey of Mason County, USDA Soil Conservation Service (1960) has mapped the site soils as Everett gravelly loamy sand, 15 to 30 percent slopes(Ef) and Everett gravelly loamy sand, 5 to 15 percent slopes (E,). The survey reads: The Everett soils are very deep, somewhat excessively drained soil on terraces and outwash plains formed in the glacial outwash stage of the most recent Fraser glaciation. These Everett soils coarsen with depth. Permeability is rapid(up to 20 inches per hour) with a high rate of water transmission. These soils are typically classified as "Hydrologic Group A" relative to surficial runoff. The water capacity for plants is low. The soils are further characterized by having medium runoff potential and moderate water erosion potential. Shrink-swell potential is described as low due to the low organic content. } The Geologic Map of Washington —Northwest Quadrant (2002) has mapped the site geology as advance outwash deposits(Qga) of continental glacial origin. The report reads: 10011 Blomberg Street SW, Olympia,WA 98512 4 Phone#: (360)7544612 Fax#: (360)7544848 GEOTECHNICAL TESTING LABORATORY Advance outwash — Glaciojluvial sand and gravel and lacustrine clay, silt, and sand deposited during the advance of glaciers; sandy units commonly thick, well sorted, and fine grained, with interlayered coarser sand, gravel, and cobbles; locally contains nonglacial sediments and deposits mapped as transitional between glacial and nonglacial. Includes the Colvos and Esperance Sand Members of the Vashon Drift and part of the Vashon Drift undivided f r The Relative Slope Stability of the Southern Hood Canal Area, Washington, (1977) describes the site area as Class 2. Class 2 is described as: Areas believed to be stable under normal conditions, but may become unstable if disturbed by man's activities, if slope is oversteepened by erosion, or if subjected to strong seismic shaking. Slopes generally steeper than 15 percent, but may be less in some areas of weak geologic materials. Includes areas underlain by: well-drained sand and gravel, mostly on valley sides that lack known slope failures; glacial till with steep slopes; and bedrock. CLIMATE OF AREA: The climate is temperate and marine. The influence of Hood Canal modifies summer and winter temperatures and reduces periods of extreme heat and cold. FIELD EXPLORATION GENERAL NOTES: The field exploration, to determine the impact from logging, included a reconnaissance of the project site and recovering grab samples. 10011 Blomberg Street SW,Olympia,WA 98512 5 Phone#: (360)754-4612 Fax#: (360)754-4848 G EOTECHNICAL TESTING LABORATORY DRILLING& SAMPLING PROCEDURES: The soil boring was performed with a conventional rubber tired back hoe. Representative samples were obtained from selected soil intervals. These samples were classified in the field by a soils technician, identified according to test boring number and depth, placed in plastic bags to protect against moisture loss and transported to the laboratory for additional testing. PROJECT DESCRIPTION The project site is located approximately 1 mile northeast of Belfair, Washington. The site will be developed for commercial structures. The 9.75-acre site has topography that consists of rolling hills that are covered with a well established understory and harvestable trees. Timberland bounds the property on the north and south. Cleared land is to the west. A railroad borders the east. Drainage patterns are well established. The site has vegetation common to the Northwest such as fir, cedar, hemlock, alder, and madrone trees as well as Scot's broom, salal, bracken ferns, sword ferns, Oregon grape, huckleberry. Onsite trees were observed straight and vertical. i rya Y, No onsite surface water was observed. No active erosion was observed. Groundwater seepage was not observed at or near the proposed building locations. No wetland vegetation was observed ,fit or near the proposed building locations. Depth to static groundwater is unknown, but is assumed to be beyond the scope of the project. Typically, dense gravelly sandy loam is found throughout the site. Competent soil can be expected approximately 14 inches below the ground surface. 10011 Blomberg Street SW,Olympia,WA 98512 6 Phone#: (360)7544612 Fax#: (360)754-4848 G EOTECHNICAL TESTING LABORATORY SUBSURFACE CONDITIONS DESCRIPTION OF FOUNDATION MATERIALS: The soil encountered throughout the site is mapped as consistent Everett gravelly sandy loam. Layers of gravelly sand loam were encountered in all the road cuts and exposed areas and extended to depths beyond the scope of this investigation. i • r _`' � "� .marts '� � k IM { } t k - 'Mt 10011 Blomberg Street SW,Olympia,WA 98512 7 Phone#: (360)754-4612 Fax#: (360)754-4848 GEOTECHNICAL TESTING LABORATORY The Liquefaction Susceptibility Map of Mason County, Washington by Palmer, Magsino, Poelstra, Bilderback, Folger, and Niggemann (September 2004) maps the site area as having a very low to low liquefaction potential. The Site Class Map of Mason County, Washington by Palmer, Magsino, Bilderback, Poelstra, Folger, and Niggemann (September 2004) maps the site area as site class C to D. Site class C is a very stiff soil or soft rock; site class D is a stiff soil. Based on our review of the subsurface conditions, we conclude that the site soils are not susceptible to liquefaction. The near-surface soils are generally in a dense condition and the static water table is located well below the surface. Shaking of the already dense soil is not apt to produce a denser configuration and subsequently excess pore water pressures are not likely to be produced. SLOPE STABILITY Based on our field observations, explorations and our experience with the soil types encountered on the property, we conclude that although portions of the slopes approach 38 percent, they are generally stable relative to deep-seated failure in their present configuration. The Mason County Critical Areas Ordinance (17.01.100) defines a landslide hazard area as one containing slopes equal to or greater than 40 percent with more than a 10-foot vertical relief. No site slopes are in excess of 40 percent with a vertical relief in excess of 10 feet. Based on this, this site does not meet the technical criteria of a landslide hazard. Near the proposed building locations, trees were found straight and vertical. No indication of past instability was discerned at the proposed building locations or throughout the site. Adjoining parcels display similar signs of stability as the subject site. No changes in slope stability are expected as a result of the proposed development of the site. Grading in the building portion of the site should be conducted in accordance with geotechnical recommendations provided herein. Site drainage can be discharged anywhere on the individual sites without negative impact. Weathering, erosion, and the resulting surficial sloughing and landsliding are natural processes that affect slope areas. This site has little or no potential for landslide activity. Building locations are proposed near slopes that are approximately 38 percent. The potential for landslide activity is not a concern. 10011 Blomberg Street SW,Olympia,WA 98512 g Phone#:(360)754-4612 Fax#: (360)754-4848 GEOTECHNICAL TESTING LABORATORY EROSION CONTROL The Mason County Critical Areas Ordinance(17.01.104) defines an erosion hazard area as: Areas in Mason County underlain by soils which are subject to severe erosion when disturbed. Such soils include, but are not limited to, those for which potential for erosion is identified in the Soil Survey of Mason County, USDA Soil Conservation Service, 1960, or any subsequent revisions or additions to this source. These soils include, but are not limited to, any occurrence of River Wash ("Ra') or Coastal Beaches ('Cg') and the following when they occur on slopes IS%or steeper: a. Alderwood gravelly sandy loam ("Ac"and "Ad') b. Cloquallum silt loam ("Cd') e. Harstine gravelly sandy loam ("Hb') d. Kitsap silt loam ("Kc') The soils at the site are mapped as Everett gravelly loamy sand (Ef and Ee). This site does not meet the technical criteria of an erosion hazard area. It is our opinion that the potential erosion hazard of the site is not a limiting factor for the proposed development. Erosion control measures should include, but not be limited to, berms and swales with ground cover/protection in exposed areas and silt fences. Graded areas should be shaped to avoid concentrations of runoff onto cut or fill slopes, natural slopes or other erosion-sensitive areas. Temporary ground cover/protection such as jute matting, excelsior matting, wood chips or clear plastic sheeting should be used until permanent erosion protection is established. TREE REMOVAL Due to the low angle slopes throughout the site, all trees may be removed, including the stumps. Established understory vegetation may be removed except fora 5 foot buffer that will remain undisturbed along the perimeter of the entire property. 10011 Blomberg Street SW,Olympia,WA 98512 9 Phone#:(360)754-4612 Fax#: (360)754-4848 GEOTECHNICAL TESTING LABORATORY • * b 4 141 SUMMARY When the plans and specifications are complete, or if significant changes are made in the character or location of the proposed structures, a consultation should be arranged to review them regarding the prevailing soil conditions. Then it may be necessary to submit supplementary recommendations. It is recommended that the services of a soils testing firm be engaged to test and evaluate the soils in the individual building areas to determine that the soils meet the fBC requirements. Monitoring and testing should also be performed to verify that suitable materials are used for structural fills and that they are properly placed and compacted. There is no evidence of soil erosion or deposition onsite to suggest that the site should be included in the Erosion Hazard Area designation. Site conditions for the proposed development do not warrant a more comprehensive Geotechnical Report. We recommend no further action is needed unless areas of concern are unearthed during construction. 10011 Blomberg Street SW,Olympia,WA 98512 10 Phone#:(360)754-4612 Fax#: (360)754-4848 GEOTECHNICAL TESTING LABORATORY If our analysis and recommendations are followed, we do not anticipate any onsite or offsite impact from the construction. It is our conclusion that potential landslide hazards from the landslide area can be overcome so as not to cause harm to property, public health and safety, or the environment. ♦. )fj' X 10011 Blomberg Street SW,Olympia,WA 98512 11 Phone#: (360)754-4612 Fax#: (360)754-4848 GEOTECHNICAL TESTING LABORATORY GEOTECHNICAL GENERAL NOTES SOIL PROPERTY SYMBOLS N: Standard"N'penetration: Blows per foot of a 140 pound hammer falling 30 inches on a 2 inch O.D. split-spoon. Q,: Unconfined compressive strength,tons/ft2 Qp: Penetrometer value,unconfined compressive strength,lbs/ft2 V: Vane value,ultimate shearing strength,lbs/ft2 M: Water content,% LL: Liquid limit,% PI: Plasticity index,% D• Natural dry h' 1 density, bs/ft 3 WT: Apparent groundwater level at time noted after completion. DRILLING AND SAMPLING SYMBOLS SS: Split-Spoon- 1 3/8"I.D., 2"O.D.,except where noted. ST: Shelby Tube-3"O.D.,except where noted. AU: Auger Sample. GB: Grab Sample. DB: Diamond Bit. CB: Carbide Bit. WS: Washed Sample. RELATIVE DENSITY AND CONSISTENCY CLASSIFICATION Terms(Non-Cohesive Soils) Standard Penetration Resistance Very Loose 0-2 Loose 2-4 Slightly Compact 4-8 Medium Dense 8- 16 Dense 16-26 Very Dense Over 26 Terms(Cohesive Soils) Q.-(tons/ft2) Very Soft 0-0.25 Soft 0.25-0.50 Firm(Medium) 0.50- 1.00 Stiff 1.00-2.00 Very Stiff 2.00-4.00 Hard 4.00+ PARTICLE SIZE Boulders 8 in.+ Coarse Sand 5 nun-0.6 mm Silts 0.074 nun-0.005 mm Cobbles 8 in. -3 in. Medium Sand 0.6 mm-0.2 mm Clays 0.005 mm&Smaller Gravel 3 in.-5 mm Fine Sand 0.2 mm-0.074 mm 10011 Blomberg Street SW,Olympia,WA 98512 12 Phone#: (360)754-4612 Fax#: (360)7544848 1 , 1 �� r •\�1���'M�- ,/ �/1(,r�l .J'Jfii� i� � t l JJ: - 1// DID -V ' � � � �► � t��.1 1,� s••�l �� ��,� � �s � , i. �� � �illlli�!:f\ � J����►l viff) at r•f on FIT 't L 11�t��n` lls�1_ IRFIdFbIR�� � �� i 1 1' 1 � 1 . 1•