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HomeMy WebLinkAboutSWP272300(1) r r �- 16t:,t` v t+ .t : i �� DEVELOPMENT PLANNING '•' :,( ;�.. t ,' t i s .} OITV 0;"RFNTON' 1995 RECEIVED t1l t ;Report' r , Geotechnical Engineering Sevicet`• `• i J. Proposed Busch Subdivision ^ ,• ,; " �� i �• ` t Renton, Washington December 19,1 1995 r ' / For , PanWest, Inc. Val .: �., . vri 1 G e.o E n g i n e e r s He No.4750-001-R02/121995 i r ; GCo 1 Erlgi Ileel•S December 19, 1995 Consulting Engineers and Geoscientists Offices in Washinglon, Oregon,and Alaska PanWest, Inc. 550 Kirkland Way, No. 408 Kirkland, Washington 98033 Attention: Mr. Christopher Oosterhoff J J We are pleased to submit two copies of our report of geotechnical engineering services for the proposed 34-lot, single-family residential subdivision in Renton, Washington. Our services were conducted in general accordance with the scope of services described in our proposal dated October 27, 1995. We appreciate the opportunity to be of service to you on this project. Please contact us if you have any questions regarding our findings or report. Yours very truly, GeoEngineers, Inc. I / I o McFadden, P.E. Project Manager Jon W. Koloski I� Principal JHC:JJM:JWK:vvl Document ID: 475(MI.R cc: Mr. Tom TOLlina Touma Engineers 15668 West Valley Hwy. Seattle, WA 98188 File No.4750-(H)1-R02 I� GeoEngineers,hic. 8410 154th Avenue N.E. l� Redmond,WA 98052 ((1a 'telephone(200)801-0000 Fax(2t)6)8016050 CONTENTS Page No. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 SCOPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 SITE CONDITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 SURFACE CONDITIONS 2 SUBSURFACE CONDITIONS 2 COAL MINE FEATURES 3 OTHER GEOLOGIC HAZARDS 4 CONCLUSIONS AND RECOMMENDATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 GENERAL 4 SITE PREPARATION AND EARTHWORK 4 STEEP SLOPE HAZARDS 5 COAL MINE HAZARDS 5 EROSION HAZARDS 6 LANDSLIDE HAZARDS 7 LIMITATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 FIGURES Figure No. Vicinity Map 1 Site Plan 2 APPENDICES Page No. Appendix A - Field Explorations A-1 APPENDIX A FIGURES Figure No. Soil Classification System A-1 Logs of Hand Borings A-2 ... A-4 G e o E n g i n e e r s t File No.4750-001-R02/12�y REPORT GEOTECHNICAL ENGINEERING SERVICES PROPOSED BUSCH SUBDIVISION RENTON, WASHINGTON FOR PANWEST, INC. INTRODUCTION This report presents the results of our geotechnical engineering services for the proposed Busch single-family residential subdivision. The project site is located west of the 2100 block of Shattuck Avenue South in Renton, Washington. The location of the site is shown on the Vicinity Map, Figure 1. Based on information provided by Mr. Tom Touma of Touma Engineers, we understand that the proposed subdivision will include 34 lots. We expect that the lots will be developed as one or two-story single family residences with relatively light foundation and floor loads. The existing and proposed site features are shown on the Site Plan, Figure 2. SCOPE The purpose of our services is to provide you with an assessment of the critical areas hazards at the property and respond to the requirements set forth by the city of Renton. Specifically, our scope of services includes the following tasks: 1. Review available geologic information for the site and surrounding area from published reports and maps, and our files. This included reviewing historical information on coal mines in the project area and copies of the Critical Areas Inventory maps. 2. Complete a geologic reconnaissance of the site and immediately adjacent area to identify any apparent signs of instability or erosion hazard. This included reconnaissance of roadway cut slopes and excavation of shallow hand borings to evaluate the general shallow subsurface soil conditions. 3. Provide guidelines for earthwork including stripping, removal of soft, organic or other unsuitable material and grading. This includes evaluating the effects of weather and construction equipment on the site soils. 4. Provide recommendations for suitable building setback from adjacent steep slopes. 5. Provide an assessment of potential coal mine hazards and delineate coal mine hazard areas which might affect development of the property. 6. Provide an assessment of potential landslide hazards and describe any evidence of existing or past instability evident during our site reconnaissance. This includes recommendations for fill placement on or near slopes. G e o E n g i n e e r s 1 File No.4750-001-R02/121995 7. Provide an assessment of potential erosion hazards and describe any existing erosion problems evident during our site reconnaissance. This includes discussion of potential impacts and necessary mitigating techniques. SITE CONDITIONS SURFACE CONDITIONS The site is situated in Section 19, Township 23 North, Range 5 East, Willamette Meridian. The area proposed for development consists of about six acres of land located at the northern tip of a northwest-southeast trending ridge that is west of Shattuck Avenue South and east of the extension of Lake Avenue South. The site is bordered by residences to the east and southeast, open space to the southwest, a steep slope to the west, and residences to the north. The crest of the ridge and the portion of the site generally located east of the crest consists of a grassy field with scattered deciduous and fruit trees. The western portion of the ridge is vegetated with a dense second growth forest of mixed coniferous and deciduous trees with a moderately dense understory of oregon grape, sword fern and shrubs. We did not observe any evidence of surface water drainage at the site. Slopes at the site include the nearly level ridge crest, the moderate east and north flanks, and the moderate to steep west flank of the ridge. Our field measurements indicate that the slopes on the eastern flank of the ridge are less than 40 percent. Slopes at the northern end of the ridge may locally exceed 40 percent where cuts have been made for an access road along the northern property boundary. Most of these roadway cut areas are on adjacent property. Slopes along most of the western flank of the ridge are generally less than 40 percent with the exception of the northwestern and southwestern site corners. Slopes at the northwestern corner of the site are approximately SO percent below a break in slope at about Elevation 170 feet. Slopes at the southwestern corner of the site exceed 40 percent in cut slopes for two unpaved roadways located below about Elevation 150 feet. Steep slopes are also present north, west, and south of the proposed development. We observed debris piles consisting of household and construction debris at several locations on the site, including the top of the slope west of the existing Busch residence and near the woodshed. A large debris slope is present near the southern boundary of Lot 22 and to the south of the lot along the slope. SUBSURFACE CONDITIONS We reviewed the Geologic Map of the Renton Quadrangle, King County, Washington, by D.R. Mullineaux, dated 1965, for information regarding site geology. The site and vicinity are mapped as Tertiary Renton Formation, which generally consists of sandstone, mudstone, and shale that has been folded and faulted. Coal is found in seams within this formation beneath a portion of the site. G e o E n g i n e e r s 2 Fibs No.4750-001-802/0,2?995 We explored shallow subsurface soil and ground water conditions during our reconnaissance at the site on November 16, 1995 by excavating 5 borings with hand tools to depths ranging from 3.0 to 4.0 feet below the ground surface. The approximate locations of the hand borings are shown in Figure 2. Details of our field exploration programs together with the hand boring logs are presented in Appendix A. The shallow subsurface conditions, as encountered in our hand borings, are relatively uniform across the site. Soils in the hand borings in the open grassy portions of the site typically include a surficial sod layer approximately 3 to 4 inches in thickness overlying a topsoil layer that extends to a depth approximately 1 to 1.2 feet below the ground surface. This topsoil layer was about 5 to 6 inches thick in HB-4, located in a forested portion of the site. The soils underlying the topsoil consist of medium dense silty sand with occasional gravel that typically grade to dense at depths of about 3 to 4 feet below the ground surface. This material is weathered bedrock of the Renton Formation, based on the geologic map and our observations of outcrops on and near the site. We observed weathered bedrock in a cut made for a garage/shed on adjacent property near the northwestern corner of the site. We observed relatively competent bedrock in an outcrop near a junction of two unpaved roads along the western portion of the site. The bedrock at this location consists of poorly cemented sandstone and dips steeply to the north. Ground water seepage was encountered in hand boring HB-2 at a depth of 3 feet below the ground surface. We did not encounter ground water in our other hand borings. Based on our observations at the northeast portion of the site and our conversations with the site owner, Mrs. Busch, we expect that the water table in the northeast portion of the site is at or within a few feet of the ground surface during the wet season. In general, ground water conditions at the site fluctuate as a function of precipitation, season and other related factors. Shallow perched ground water should be expected during extended periods of wet weather where excavations extend to the underlying bedrock. COAL MINE FEATURES We reviewed a study of coal training in the Renton area by Morrison Knudsen titled, "Engineering Investigation for the Renton, Washington Area," dated January 1985. This study provides information regarding the location and history of coal mining activity on and near the site. We also reviewed coal mine maps available from the Department of Natural Resources. Based on information from these sources, we understand that workings of the Sunbeam Mine are located approximately 150 feet beneath the ground surface near the south portion of the site. The coal seams mined in the workings dip steeply to the north-northeast at about 60 degrees following the trend of the bedrock structure. The Sunbeam Mine began operation in about 1925 and closed in 1929 as a result of a mine fire. The approximate locations of the coal mine workings are shown in Figure 2. We did not observe any sinkholes, spoil piles or other features that appear to be related to coal mine activity on the site. We understand from maps of features observed by others that some of these features may be present on undeveloped land south of the site. G e o E n g i n e e r s 3 File No.4750-001-R02/121995 OTHER GEOLOGIC HAZARDS The northwestern and southwestern portions of the site are mapped as high landslide hazard areas by the city of Renton. We did not observe evidence of slope instability on undisturbed slopes with the exception of scattered tilted or butt-bowed conifers. We observed an area of shallow landsliding on the cut slope of an unpaved roadway about 100 feet south of the site. We did not observe evidence of significant existing erosion at the site with the exception of evidence of soil creep and slope ravel on steep cuts on and adjacent to the site. CONCLUSIONS AND RECOMMENDATIONS GENERAL In our opinion, the site conditions are generally favorable for development as proposed. However, several proposed lots on the western portion of the site contain steep slopes and are within landslide or erosion hazard areas as mapped by the city of Renton. Individual lots within this area may require site-specific investigations, as described in the following sections. Based on existing site grades, we expect that cuts and fills will be required to attain design grades. Unless earthwork operations are completed during periods of extended dry weather, imported fill will be required for structural fill since the on-site native soils are moisture sensitive. Cuts greater than about 4 feet below the ground surface or near the surface in local areas may encounter competent bedrock that will require ripping with heavy equipment or jackhammering to remove. Our specific geotechnical recorunendations for the subdivision are presented in the following sections of this report. SITE PREPARATION AND EARTHWORK The following recommendations apply to all earthwork and structural fill placement and compaction for roadway construction and will generally apply to development of individual lots. • We recommend that the existing sod and vegetation be stripped to a depth of about 4 to 6 inches. • We recommend that the topsoil and any loose soil underlying the sod and vegetation be removed to expose a firm base. We expect that the total stripping depth will be about 6 to 12 inches or more below the existing ground surface. • The exposed subgrade should be compacted to a firm, nonyielding condition prior to placing structural fill or formwork. • Imported structural fill should consist of sand and gravel containing less than 5 percent fines by weight relative to the fraction of the material passing the 3/4-inch sieve. Structural fill should be free of rock fragments larger than 6 inches, debris and organic materials. G e o E n g i n e e r s 4 File No.4750-001-R02/121995 • Structural fill placed within 2 feet of pavement subgrade in proposed roadway areas must be compacted to at least 95 percent of MDD (maximum dry density) as determined in accordance with the ASTM-D1557 test standard. This will also apply to all structural fill for foundation and floor slab support. Structural fill placed below a depth of 2 feet to pavement subgrade should be compacted to at least 90 percent MDD. • Structural fill placed in utility trenches should be compacted to at least 90 percent of MDD in accordance with ASTM-D1557, except in any areas to be paved. In these areas, the upper 2 feet below finished subgrade elevation must be compacted to at least 95 percent of the same standard. • During periods of wet weather, subgrade areas being prepared should be limited in size such that the exposure of the subgrade to wet weather is minimized. STEEP SLOPE HAZARDS Tile city of Renton defines steep slopes as slopes inclined at more than 40 percent. According to the city of Renton greenbelt regulations,development is prohibited on slopes greater than 40 percent. In addition, we recommend the following setbacks from the tops of steep slopes: • A combined buffer and setback of at least 25 feet should be maintained from the tops of slopes steeper than 40 percent and greater than 20 feet in height. This will consist of a 10-foot buffer where the existing vegetation is maintained and a 15-foot setback to the building. • Slopes steeper than 40 percent and less than 20 feet in height may be regraded to a slope flatter than 40 percent or may be subject to a shorter combined buffer and setback as determined by a qualified geotechnical engineer or engineering geologist. COAL MINE HAZARDS Based on our review of published literature and our site observations, it is our opinion that coal mining activity in the vicinity of the site is limited to workings of the Sunbeam Mine. Documented surficial features related to this mine are situated south and west of the site. We did not observe any mine-related features that would impact the development of the site. We recommend, however, that access to the documented features south of the site be actively discouraged. This can be accomplished by methods such as fencing, maintaining the present blackberry cover, and other means. Based on our review of available information, underground mines exist approximately 150 feet below the ground surface at the south portion of the site. These workings are shown on Figure 2. The generally accepted depth or thickness of overburden for "safe" surface development over underground mines is 200 feet. The 200-foot-depth represents a risk of less than 1 percent for the possible occurrence of a sinkliole(subsidence feature) based on case history studies in underground mining areas in Colorado. Based on our research in King County, no G e o E n g i n e e r s 5 File No.4750-001-1102/121995 known sinkholes have been observed where the depth to the workings is in excess of 50 feet. It is therefore our opinion that the risk of sinkhole occurrence is small for the workings underlying the south portion of the site. It is our opinion that the south portion of the site is at risk regarding regional downwarping of the ground surface caused by collapse of the abandoned underground workings. The damage to structures built in this portion of the site as a result of regional downwarping may be manifested by jammed doorways or windows, or cracks in drywall or masonry finishing. The structural damage could be similar to that expected for most new, wood-framed construction as a result of ground adjustments to the home foundation loads. We do not characterize this type of damage as threatening to the structure. The northward limit of anticipated downwarping is shown in Figure 2. There is an inherently higher risk of potential damage to a structure built on the subject lots as compared to a similar home built in an area with no underground mines. This is because of the possibility of undocumented underground workings and prospects, and the unknown nature by which regional downwarping is manifested in this area. The area mine workings have been abandoned for several decades, and for this reason, a substantial amount of the collapse in the deep workings should have already occurred. In order to minimize the risk of structural damage because of potential regional downwarping, we recommend that the use of extra rigid foundations supporting a flexible superstructure be considered in the general design. A small, square or a nearly square-shaped building pad is favored over a large, irregularly shaped building pad. Consideration in design of the superstructure should include the ability to relevel the building and any gravity-dependent utilities (sanitary sewers, for example). Utility couplings should be flexible enough to anticipate some post-construction ground movement. We recommend that we be present at the site when the site preparation is initiated. The purpose of our site observations during grading would be to observe the underlying soils to see whether any mining related features (subsidence, sinkholes, adits, air shafts, portals, etc.) are exposed. EROSION HAZARDS We recommend that an Erosion and Sedimentation Control Plan (ESCP) detailing specific locations for engineering controls be prepared for use during and after construction. Erosion control measures should be designed in accordance with the King County Surface Water Design Manual and with applicable city of Renton regulations. The ESCP should incorporate the recommendations described below. • Erosion control measures should be specifically developed to address the individual causes and sources of erosion and sedimentation, and should emphasize erosion control rather than relying primarily on sediment control. G e o E n g i n e e r s 6 Hf! Nn. 4750-txlt-R'2!1219G5 • The erosion control system should include redundancies or back-up protection, such that no single element of the system is relied upon to completely control erosion and sedimentation, and should be monitored and maintained. • Preventative erosion control measures that should be implemented on the site include minimizing the area of site disturbance, site grading to avoid concentration of surface runoff onto or off of cut or fill slopes and natural slopes, and reestablishing ground cover and vegetation as soon as possible in disturbed areas. • Preventative sediment transport measures that should be implemented along the site boundaries include installation of silt fences, straw bales, or other devices and techniques Ithat will trap sediment and prevent it from moving off site. LANDSLIDE HAZARDS We reconunend the following measures to mitigate potential landslide hazards at the site: • An erosion and sedimentation control plan (ESOP) should be developed and implemented Ias described in the Erosion hazards section of this report. • Combined buffers and setbacks should be maintained as described in the Steep Slope Hazards section of this report. • No fill should be placed on slopes steeper than 4H:1V (horizontal to vertical) without an f evaluation of the proposed fill configuration by a representative of GeoEngineers. 1 LIMITATIONS 1 We have prepared this report for use by PanWest and Touma Engineers and other members of the design team in the design of a portion of this project. The data and report should be provided to prospective contractors for bidding or estimating purposes. However, our report, conclusions and interpretations should not be construed as a warranty of the subsurface conditions. The conclusions and recommendations in this report should be applied in their entirety. The project was in the preliminary planning stage at the time this report was completed. We therefore expect that modifications to the proposed plat layout may be made as plans are finalized. If there are any changes in the locations or type of improvements to be constructed, the conclusions and recommendations presented in this report might not be fully applicable. If any such changes are made, we should be retained to review our conclusions and recommendations and to provide written modifications or verifications of these recommendations. Variations in subsurface conditions are possible between the locations of the explorations. Such variations can also occur over time. A contingency for unanticipated conditions should be included in the project budget and schedule for such an occurrence. G e o E n g i n e e r s 7 file No.4750.001-R02l121995 Within the limitations of scope, schedule and budget, our services have been executed in accordance with generally accepted geotechnical practices in this area at the time the report was prepared. No warranty or other conditions, express or implied, should be understood. O ► We appreciate the opportunity to be of service to PanWest, Inc. Please call if you have any questions regarding this report or require additional information. Respectfully submitted, GeoEngineers, In . � )Vt c `'v WP �• �� , 'Y c,l net 1-1. Curran Engine ring Geo gis � f c�; '1•re- Gam. cFadden, P.E. EXPIRES 3 7 roject Engineer on W. Koloski Principal JHC:JJM:JWK:vvi Document ID: 4750001.R Copyright© 1995 by GeoEngineers.Inc.,All rights reserved G e o E n g i nee r s 8 File No.4750-001-1102/121995 RAILROAa_ \,\I ` `fit, — �� Q� � �RAp`_ goo I ��•r•47e .� • •' .�. ;y ••w��•�' �/ _� � -- 13 tiN cull course Ir Z�r 1 & ' NOR7t. �.� LING ♦ F a Sew e �•, I •• 1/' '" �I •��� sub e� .\ •►••�ZsUosa 1. � •�_ .. ` .455 M 16 19 'Longacre4 r 1- _ �: ✓-4 I\ 1 §I — SITE L,i Track "—" —_ I -- -- -- ' .' -- , �$ :BM ` _ l ---- ,4T6 4ism Lp .1 -_ ;I I I I 'I I,I •1_ 1• �/ off _ I '�a BM i - - -- - ----- -- .3o ,I l �.� V - IB 2 _ 25 ��`� 0 203 —.- BM 1 F�_ N 1 0 2000 4000 SCALE�1�_FEET Reference: USGS 7.5' topographic quadrangle map 'Renton. Wash.,' photorevised 1973. � VICINITY MAP Geo�vlEngineers FIGURE 1 „t'�'tJ.�?j t•�`[i:.� r _ fr . : i l � I; �, ) �� � `. F r �:•. 1 fF < •��r< •1 r : (�- \.. %' �” ` '` tti '• !fit ' r t ) , APPENDIX A 7 } r ( t r 1 Al. , •r :•`• � 1, / - i I .}. `� `� if+ .(,- r , APPENDIX A FIELD EXPLORATIONS Subsurface soil conditions were explored by excavating 5 hand borings at the approximate locations shown in Figure 2. The explorations were located in the field by taping from existing site features. The hand borings were excavated on November 16, 1995 by an engineering geologist on our staff using hand tools. The hand borings were excavated to depths ranging from approximately 3.0 to 4.0 feet below the existing ground surface. The explorations were backfilled with the excavated material and compacted with hand tools upon completion. Our representative visually classified the soils encountered, obtained representative soil samples, observed ground water seepage conditions and prepared a detailed log of each exploration. Soils encountered were classified in general accordance with the classification system described in Figure A-1. The hand boring logs are presented in Figures A-2 through A-4. 1 1 1 ' 1 l G e o E n g i n e e r s A - 1 File No.4750-001-R02/121995 UNNEW SOIL CLASSIFICATION SYSTEM GROUP MAJOR DIVISIONS SYMBOL GROUP NAME GRAVEL CLEAN GW WELL-GRADED GRAVEL,FINE TO COARSE GRAVEL COARSE GRAVEL GRAINED GP POORLY-GRADED GRAVEL SOILS More Than 50% of Coarse Fraction GRAVEL GM SILTY GRAVEL Retained WITH FINES on No. 4 Sieve GC CLAYEY GRAVEL More Than 50% SAND CLEAN SAND SW WELL-GRADED SAND, FINE TO COARSE SAND Retained on No. 200 Sieve Sp POORLY-GRADED SAND More Than 50% of Coarse Fraction SAND SM SILTY SAND Passes WITH FINES No. 4 Sieve SC CLAYEY SAND FINE SILT AND CLAY ML SILT GRAINED INORGANIC SOILS CL CLAY Liquid Limit ORGANIC OL ORGANIC SILT,ORGANIC CLAY Less Than 50 More Than 50% SILT AND CLAY MH SILT OF HIGH PLASTICITY, ELASTIC SILT Passes INORGANIC CH CLAY OF HIGH PLASTICITY, FAT CLAY No. 200 Sieve Liquid Limit ORGANIC OH ORGANIC CLAY,ORGANIC SILT 50 or More HIGHLY ORGANIC SOILS PT PEAT NOTES: SOIL MOISTURE MODIFIERS: 1. Field classification is based on visual examination of soil Dry- Absence of moisture, dusty, dry to the touch in general accordance with ASTM D2488-90. Moist- Damp, but no visible water 2. Soil classification using laboratory tests is based on ASTM D2487-90. Wet - Visible free water or saturated, usually soil is obtained from below water table 3. Descriptions of soil density or consistency are based on interpretation of blow count data, visual appearance of soils, and/or test data. M V'1 O u �� SOIL CLASSIFICATION SYSTEM W Geo��Engineers FIGURE A-1 LOG OF HAND BORING DEPTH BELOW SOIL GROUP GROUND SURFACE CLASSIFICATION (FEET) SYMBOL DESCRIPTION HAND BORING HB-1 Approximate ground surface elevation: 192 feet 0.0-0.3 Sod 1 0.3- 1.0 Topsoil 1.0-3.0 SM Brown and gray silty fine sand with occasional fine to coarse gravel(medium dense, 1 moist)(weathered bedrock) 3.0-4.0 SM Tan and orange silty fine sand(medium dense,moist)(weathered bedrock) 1 Becomes sandier,dense at 4.0 feet Iland boring completed at 4.0 feet on 11/16/95 No ground water seepage observed Disturbed soil sample obtained at 3.5 feet HAND BORING IIB-2 Approximate ground surface elevation: 145 feet 0.0-0.3 Sod 0.0- 1.2 Topsoil 1.2-3.5 ML Dark brown sandy silt with occasional fine to coarse gravel(medium stiff, moist) Grades to brown at 2.5 feet Grades to wet at 3.0 feet 3.5-3.8 SM Tan and orange silty fine sand with occasional coarse sand and gravel (medium dense,moist)(weathered bedrock) . Eland boring completed at 3.8 feet on 11/16/95 Slight ground water seepage observed at 3.0 feet Met refusal on gravel at 3.8 feet Disturbed soil sample obtained at 3.7 feet i I THE DEPTHS ON THE HAND BORING LOGS,ALTHOUGH SHOWN TO 0.1 FOOT,ARE BASED ON AN AVERAGE OF MEASUREMENTS ACROSS THE HAND BORING AND SHOULD BE CONSIDERED ACCURATE TO 0.5 FOOT. LOG OF HAND BORING Geo !Engineers FIGURE A-2 a LOG OF HAND BORING DEPTH BELOW SOIL GROUP GROUND SURFACE CLASSIFICATION (FEET) SYMBOL DESCRIPTION HAND BORING 1113-3 Approximate ground surface elevation: 200 feet 0.0-0.5 Topsoil 0.5- 1.0 ML/SM Topsoil with lenses of tan and orange silty sand with occasional fine to coarse gravel (medium stiff/medium dense,moist) 1.0-3.0 SM Tan and orange silty fine to medium sand(dense,moist)(weathered bedrock), t Grades to very dense at 3.0 feet Hand boring completed at 3.0 feet on 11/16/95 No ground water seepage observed Met refusal on very dense weathered bedrock at 3.0 feet Disturbed soil sample obtained at 2.5 feet HAND BORING 11134 Approximate ground surface elevation: 175 feet 0.0-0.4 Topsoil 0.4-3.0 SM Brown silty fine sand with medium sand and occasional fine to coarse gravel(loose, moist) Grades to medium dense at 2.0 feet 3.0-3.8 SP-SM Orangish brown fine sand with silt(medium dense,moist) Lenses of gravel at 3.5 feet Hand boring completed at 3.8 feet on 11/16/95 No ground water seepage observed Disturbed soil sample obtained at 3.7 feet THE DEPTHS ON THE HAND BORING LOGS,ALTHOUGH SHOWN TO 0.1 FOOT,ARE BASED ON AN AVERAGE OF MEASUREMENTS ACROSS THE HAND BORING AND SHOULD BE CONSIDERED ACCURATE TO 0.5 FOOT. LOG OF HAND BORING Geo I Engineers FIGURE A-3 DEPTH BELOW SOIL GROUP LOG OF HAND BORING GROUND SURFACE CLASSIFICATION (FEET) SYMBOL DESCRIPTION 11AND BORING IIB-5 ' Approximate ground surface elevation: 182 feet 0.0- 1.0 Topsoil 1 1.0-3.7 SM Tan silty fine sand with occasional coarse sand(medium dense,moist) Hand boring completed at 3.7 feet on 11/16/95 ' No ground water seepage observed F Disturbed soil sample obtained at 3.7 feet 1 1 1 1 l l THE DEPTHS ON THE HAND BORING LOGS,ALTHOUGH SHOWN TO 0.1 FOOT,ARE BASED ON AN AVERAGE OF MEASUREMENTS ACROSS THE HAND BORING AND SHOULD BE CONSIDERED ACCURATE TO 0.5 FOOT. e'Alts. LOG OF HAND BORING Geo��Engineers FIGURE A-4