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HomeMy WebLinkAboutSubsurface Exploration and GeoTech Report - SWG Letters / Memos - 1/30/1990 Tollef sonDavidson P R O P E R T I E S January 30, 1990 Mr. Stan Mar Mar/Hara Architects 1923 First Avenue Seattle, Washington 98101 Re: Belfair Dear Stan: Enclosed is a copy of the January 23, 1990 soils report prepared by Associated Earth Sciences, Inc. Why does the engineer say on page 2 that up to 8 feet of fill will be required in the building areas? We ' re going to also send a copy of the report to one of the former property owners. Maybe he can refer back to his soil logs 9 and/or as-built drawings for the storm system to provide us with more information on other holes that might contain unsuitable materials. Best regards, TMLEFSON-DAVIDSON PROPER TIES Philip J. Davidson PJD/sh Enclosure cc: Mark Kuhlman w/enclosure Marley Young w/enclosure Rick Krueger w/enclosure k 1 606-110th Avenue N.E.,Suite 206 Bellevue,WA 98004 (206)455-2849 4 SUBSURFACE EXPLORATION AND GEOTECHNICAL ENGINEERING REPORT BELFAIR CENTER Belf air, Washington PREPARED FOR Claremont Development Co. PROJECT NO. 8909-23G JANUARY 23, 1990 ASSOCIATED EARTH SCIENCES, INC 911 -5th Avenue,Suite 100,Kirkland,WA98033 (206) 827-7701 f 1 SUBSURFACE EXPLORATION AND GEOTECHNICAL ENGINEERING REPORT BELFAIR CENTER BELFAIR, WASHINGTON January 23, 1990 Project No. 8909-23G I. PROJECT AND SITE CONDITIONS 1.0 INTRODUCTION This report presents the results of our subsurface exploration, geologic, and geotechnical engineering study for the proposed shopping center in Belfair , Washington. The proposed building locations and approximate locations of the explorations accomplished for this study are presented on the Site and Exploration Plan, Figure 1 . In the event that any changes in the nature, design or locution of the structures are planned , the conclusions and recommendations contained in this report should be reviewed and modified, or verified as necessary. 1 . 1 Purpose and Scope The purpose of this study was to provide subsurface data to be utilized in the design and development of the above mentioned project . Our field study included excavation of exploration pits and performing geologic studies to assess the type , thickness , distribution and physical properties of the subsurface soils . Engineering studies were also conducted to determine the type of suitable foundation , allowable bearing pressures , anticipated settlements, lateral wall pressures, floor support recommendations, drainage and erosion considerations , and rockery construction recommendations. This report summarizes our current field work and offers development recommendations based on our present understanding of the project. 1.2 Authorization Written authorization to proceed with this study was granted by Mr. Phil Davidson of Claremont Development Company. Our study was accomplished in general accordance with our proposal dated February 27 , 1989 . This report has been prepared for the exclusive use of Claremont Development Company and their agents , for specific application to this project, in accordance with generally accepted geotechnical engineering and engineering geology practices . No other warranty, expressed or implied is made. Our observations , findings, and conclusions are a means to identify and reduce risks. r 2.0 PROJECT AND SITE DESCRIPTION This report was completed with an understanding of the project based on a grading plan developed by PAC-TECH Engineers received December 18 , 1989 (undated) , and a preliminary site plan by PAC-TECH Engineers dated November 11 , 1989 . Present plans call for an approximate 94 , 000 square foot shopping center including a supermarket, drugstore and retail shops in the main complex located on the northern portion of the site. Two smaller (3600 square foot) building sites (Pads 1 and 2, Figure 1) are to be located near SR-3 on the southern portion of the site. The slab-on-grade finish floor elevations for the main complex vary from 100. 5 for the market to 106 . 0 for the easternmost retail shops. These floor elevations will require up to approximately 8 feet of fill above existing grade on the building interiors and up to 4 feet of fill to reach the planned exterior grades next to the complex. The fill depths range from near zero along the southern portion of the main complex to the aforementioned maximum depths along the north building perimeter. Building pad No. 1 will require up to 2 feet of fill above existing grade in the northwest corner and Building Pad No. 2 will require approximately 4 feet of cut to reach finish grade. The areas surrounding the complex will be paved and utilized for parking. Grading for the parking area will require cuts up to 13 feet in the area of the east property line . The current grading plans call for a rockery in this cut area and along a fill section bordering Roy Boad Road. Details of the type of construction and floor and foundation loads for the buildings were not available at the time this report was prepared. The subject parcel consists of approximately 8.4 acres situated near the northwest corner of the intersection of State Route 3 and Old Belfair Road. The site is bordered on the south by SR-3 , on the north by Roy Boad Road and residential property, on the east by a retail business and on the west by a residential area . Site topography consists of a moderate slope dipping predominately to the west from the east site boundary. The majority of this slope is at an inclination within the range of 9H:1V (Horizontal :Vertical) to 5H: 1V. Near the central area of the site, the slope flattens and trends more northward. In one area along the east boundary near the northeast corner, an approximate 12 foot high, 1H: lV slope exists. In this area, it appears that the original grade was steepened by fill placed on the adjacent property. Total elevation change across the site was approximately 34 feet. Vegetation consisted of scattered young trees , grass and weeds. The site was apparently logged and partially cleared in the recent past. The only standing surface water observed at the time of our I exploration was in a small , man-made pond located near the north central site boundary. 2 Existing improvements on the site include a subsurface drainage system situated in the western area. A Grading and Storm plan by Norman L. Olsen, P.E. dated February 15, 1988 , indicates that this system consists of 2 catch basins and approximately 315 lineal feet of pipe at depths up to 7 feet below existing grade (Figure 1 ) . This drain was apparently placed in a natural drainage swale that crossed the property from south to north prior to filling the swale. The drain discharges into the aforementioned pond located adjacent to Roy Boad Road approximately 400 feet east of the northwest property corner. 3.0 SUBSURFACE EXPLORATION Our field study included excavating a series of 25 exploration pits to gain information about the site. The various types of soils , as well as the depths where the soils or characteristics of the soils changed , are indicated on the exploration logs presented in the Appendix. The depths indicated on the logs where soil conditions changed may represent gradational changes between soil types in the field. Our exploration pits were approximately located in the field by measuring from known site features shown on a topographic survey prepared by R.M. McGinnis and Associates , Inc. P.L.S. dated May 17 , 1988. The conclusions and recommendations presented in this report are based on the 25 exploration pits completed for this study. The number , location, and depth of the explorations were completed within site and budgetary constraints . Because of the nature of exploratory work below ground , extrapolation of subsurface conditions between field explorations is necessary. It should be noted that differing subsurface conditions may sometimes be present due to the random nature of deposition and the alteration of topography by past grading and/or filling. The nature and extent of any variations between the field explorations may not become fully evident until construction. If variations are observed at that time, it may be necessary to re-evaluate specific recommendations in this report and make appropriate changes . 3.1 Exploration Pits Our field study included excavating a series of exploration pits with a tractor-mounted backhoe. Each of the pits penetrated between 5 and 16 feet below present ground surface and permitted direct , visual observation of subsurface conditions . The materials encountered in the exploration pits were studied and classified in the field by a geotechnical engineer from our firm. All exploration pits were backfilled immediately after examination and logging. i i 3 4 .0 SUBSURFACE CONDITIONS Subsurface conditions on the parcel were inferred from the field explorations accomplished for this study, visual reconnaissance of the site and review of applicable geologic literature. As shown on the field logs, the exploration pits generally encountered medium dense to dense sand and gravel sediments . Fill soils were also encountered, predominately in the south half of the site. 4 .1 Stratigraphy Fill soils ( those not naturally placed) were encountered in exploration pits EP-3, EP-8 , EP-11 , EP-12, EP-13, EP-14 , EP-20, EP- 21 , EP-22, EP-23, and EP-24 . The fill ranged in thickness from 1 foot in several locations to 5-1/2 feet in EP-20 and EP-22 . As noted on the exploration logs , the fill consisted of a medium dense/medium stiff , dry to moist , brown, silt , sand and gravel mixture with organics and wood debris . The majority of these materials probably originated from filling and grading in and around the aforementioned natural drainage swales and depressions . The fill material likely originated from both onsite and an offsite borrow source. In many areas, the organic fill was capped with a 1 to 2 foot thick layer of granular fill . Other isolated areas of fill or debris may exist where large stumps were removed and at burn pile locations. Since only limited documentation is available to define the previously existing ground surface topography, the extent of grading and filling can only be estimated and is shown in Figure 1 . Compaction of the fill materials was apparently not documented. The specific nature , extent and uniformity of such materials are therefore uncertain and unpredictable. Below the fill in the representative areas of EP-20, EP-21, EP-22, EP-23 and EP-24 , the natural sediments generally consisted of medium dense to dense, damp to saturated, brown to grey sand, or sand and gravel . These sediments extended below the termination depth of the exploration pits. In EP-20, the sediments were similar in gradation to those in other exploration pits but were in a loose condition. These may represent fluvial sediments deposited in the swale that was present in this area prior to filling. At the surface in the unfilled areas of the site below approximate elevation 96, in exploration pits EP-6 , EP-7 , EP-9 and EP-10, the natural sediments consisted of a 1/2 to 1-1/2 foot thick layer of loose to medium dense, dry to damp, dark brown to grey-brown, fine sand or sand and silt . This layer usually contained a large quantity of roots and organics . Below this layer and below the fill in EP-8 , EP-12, EP-13, and EP-14 , medium dense, dry to moist, brown or grey sand with variable quantities of silt and gravel extended to depths varying from 4 to 8 feet . Underlying this layer , medium dense to dense, damp to saturated, grey sand, and sand and gravel sediments were encountered for the remaining depth of the exploration pits. i I 4 i t r In the unfilled area of the higher, eastern portion of the site above elevation 96 (exploration pits EP-1, EP-2, west end of EP-3, EP-4 , EP-5 , and EP-15 through EP-19) , the surficial sediments extended to a depth ranging from 1/2 to 6 feet and generally consisted of medium dense , dry to damp, brown, silty sand and gravel , or gravelly sand with some silt. The upper 1/2 to 2 feet of this unit contained numerous roots and organics. Below this and at the surface in EP-25 , medium dense to dense , damp, grey to grey- brown sand, to sand and gravel with a small fraction of silt was found . The gravel content generally increased with depth. This unit extended below the termination depth of all of the representative exploration pits. The natural , medium dense to dense , coarser sand and gravel sediments described above are interpreted to be ice contact recessional sediments deposited behind the retreating ice after the last glacial advance . The finer-grained sand and silt sediments found at the lower site elevations were likely deposited later in the lower energy alluvial or flood plain environment of the Union River located northeast of the site. 4 . 2 Hydrology I Ground water seepage was encountered in some of our exploration pits at the time of our field study. The depth of seepage ranged from 5 feet to 11 feet and probably indicated the actual local water table in the lower portion of the site and ground water seepage from upslope through the original swale area in the southeastern portion of the site. Seepage may also occur at random depths and locations G in unsupervised or non-uniform fills. It should be noted that our exploration was completed in October when the ground water depths are near minimum . During the wetter seasons , ground water elevations and flow rates may be significantly higher. 5 r r January 23, 1990 Project No. 8909-23G II. DESIGN RECOMMENDATIONS 5.0 INTRODUCTION Our exploration indicates that, from a geotechnical standpoint, the parcel is suitable for the proposed development . In most of the proposed building areas , the bearing stratum is relatively shallow and spread footing foundations are feasible . In the previously filled areas of the site , remedial work including removal and replacement of the existing fill, as outlined in Section 6.0, Site Preparation , will be required for support of spread footing foundations. 6.0 SITE PREPARATION Prior to site preparation, the portion of the existing drain system that traverses beneath the planned supermarket building should be removed. This would include catch basin 2 and the segment of non- perforated pips that extends from CB-2 to the outlet . The collection portion of the system outside the building envelopes should be left intact and connected to the site storm drain system. It is recommended that this portion of the drain system remain functional since it does assist in removing water from the filled swale area. Following removal of the required pipe sections, any remaining pipe backfill material , fill , and underlying , unsuitable natural sediments should be removed to expose suitable non-organic, natural sediments. The area of fill removal and stripping should extend a distance of 10 feet outside the building perimeters . The area should then be filled with structural fill as discussed in Section 7 .0, Structural Fill . The depth of the existing fill material to be removed will range from up to approximately 7 feet around the pipe, tapering to zero at the fill margins . Prior to refilling and grading of the remaining building, access and parking areas , all stumps , brush, debris and any other deleterious material should be removed. Additionally, the upper organic laden soil should be removed and the remaining roots grubbed . In previously undisturbed or other filled areas, the depth of stripping will range from approximately 6 inches to 1-1/2 feet. Areas where loose surface soils exist due to grubbing operations should be considered as fill to the depth of disturbance and treated as subsequently recommended for fill placement. If, during stripping, areas of soft subgrade are encountered , these areas should be overexcavated and backfilled with structural fill. 6 i e Due to the variability of the quality and thickness of the fill materials onsite, the amount and areal extent of stripping is best determined in the field by the geotechnical engineer or his representative. The thickness of the fill indicated in this report and on the exploration pit logs is representative of these exact pit locations only, and variations may occur between pits . These thicknesses should be used for estimating purposes only, not for assigning a fixed fee contract for fill removal . 7 .0 STRUCTURAL FILL After site preparation has been performed to the satisfaction of the geotechnical engineer/engineering geologist, the upper 12 inches of exposed ground should be compacted to 90 percent of the Modified Proctor Maximum Density using ASTM:D 1557 as the standard. If the subgrade in the lower areas of the site contains too much moisture, adequate recompaction may be difficult or impossible to obtain and should probably not be attempted. In lieu of recompaction, the area to receive fill should be blanketed with select , free-draining onsite gravel , washed rock, or quarry spalls to act as a capillary break between the new fill and the wet subgrade. After recompaction of the exposed ground is tested and approved or a free-draining base course is laid, structural fill may be placed to attain desired grades . Structural fill is defined as soil acceptable to the Geotechnical Engineer, placed in 8 inch loose lifts , with each lift being compacted to a minimum of 95 percent of the Modified Proctor Maximum Density using ASTM:D 1557 as the standard. For roadway and utility trench backfill , the fill should be placed and compacted in accordance with current Local or County codes and standards. The compacted edges of the fill should extend outward a minimum distance equal to the depth of the fill plus 3 feet beyond the location of the perimeter footings for the structures. The contractor should note that any proposed fill soils must be evaluated by Associated Earth Sciences, Inc. prior to their use in fills. This would require that we have a sample of the material 48 hours in advance to determine its characteristics and field compaction standard. Soils in which the amount of fine-grained material (smaller than No. 200 sieve) is greater than approximately 5 percent should be considered moisture-sensitive. Use of moisture- sensitive soil in structural fills should be limited to favorable dry weather conditions . A portion of the onsite soils in the i proposed cut areas on the east area of the site had less than 5 percent fines and were below their "optimum moisture content" . The optimum moisture content of soil is that which allows the highest density to be obtained under a given compactive effort . Consequently, part of the onsite, non-organic soils are suitable for use as structural fill . The lower, northern area of the site which is planned to be filled , consists of moisture-sensitive , finer- grained sands and silt. During the wetter winter months , it also appears that the local ground water table may rise to near the G 'I 7 c ground surface in this area . Thus , the contractor must exercise care during site preparation and filling so that the underlying soils are not disturbed. If disturbance occurs , the softened soils should be removed and replaced with structural fill . If possible, filling of this area should be performed during the summer months. Organic soils are not suitable for use in fills but may be used in landscaping. A representative from our firm should inspect the stripped subgrade and be present during placement of structural fill to observe the work and perform a representative number of in-place density tests. In this way, the adequacy of the earthwork may be evaluated as filling progresses and any problem areas may be correct at that time. It is important to understand that taking random compaction tests on a part-time basis will not assure uniformity or acceptable performance of a fill . As such, we available to aid the owner in developing a suitable monitoring and testing program. 8 .0 FOUNDATIONS Spread footings may be used for building support when founded on medium dense, natural soils, or structural fill placed as discussed under Section 7 .0, Structural Fill. In order to reduce potential differential settlement between foundations placed partially on structural fill , medium dense and dense natural sediments , we recommend that an allowable bearing pressure of 2 , 500 pounds per square foot (psf) may be utilized for design purposes , including both dead and live loads. An increase of one-third may be used for short-term wind or seismic loading. Perimeter footings should be buried at least 18 inches into the surrounding soil for frost protection. Interior footings need only extend 12 inches below adjacent grade. However , all footings must penetrate to the prescribed bearing stratum and no footing should be founded in or above loose , organic , or existing fill soils . In addition, all footings should have a minimum width of 18 inches. Anticipated settlement of footings founded on medium dense to dense sands and gravels , or approved structural fill should be on the order of 1 inch. However, disturbed soil not removed from footing excavations prior to footing placement, could result in increased settlements. All footing areas should be inspected by Associated Earth Sciences , Inc. prior to placing concrete, to verify that the bearing soils are undisturbed and consistent with the recommendations contained in this report. Such inspections may be required by the governing municipality. Perimeter footing drains should be provided as discussed under Section 11 . 0 , Drainage Considerations. In the representative area of EP-20 in the vicinity of building pad No . 1 , an unusual thickness of loose , natural sediments was encountered below the fill soils . The areal extent and depth of this loose material should be determined during the earthwork phase 8 of the project and any appropriate remedial measures implemented at that time . We are concerned about the possibility of excessive depth of these sediments within the building envelope. 9.0 LATERAL WALL PRESSURES Grade differentials of up to 4-1/2 feet between the interior finish floors and exterior parking grades of the market , drug store and retail buildings are currently planned. All backfill behind these walls or around foundation units should be placed as per our recommendations for structural fill and as described in this section of the report . Free-draining backfilled walls which are free to yield laterally at least 0 . 1 percent of their height , may be designed using an equivalent fluid equal to 35 pounds per cubic foot (pcf) . Fully restrained rigid walls which cannot yield should be designed for an equivalent fluid of 50 pcf . The lateral pressures presented above are based on the conditions of a uniform, horizontal backfill consisting of onsite, free-draining sand and gravel compacted to 90 percent of ASTM:D 1557. A higher degree of compaction is not recommended as this will increase the pressure acting on the wall . Surcharges from adjacent floors or equipment must be added to the above values. Retainage will also be required for the north portion of the cut along the east property line, where loose fill soils are present. This may consist of an approximate 4 to 5 foot high cantilever wall with a 2H: 1V backslope. For this case, an equivalent fluid equal to 58 pcf should be used for design of the wall . Footing drains should be provided for all retaining walls as discussed under the section on Drainage Considerations. 9. 1 Passive Resistance and Friction Factors Retaining wall footings/keyways cast directly against undisturbed, dense soils in a trench may be designed for passive resistance against lateral translation using an equivalent fluid equal to 400 pounds per cubic foot ( pcf ) . This value applies only to footings/keyways where concrete is placed directly against the trench sidewalls without the use of forms. If footings are placed on grade and then backfilled, the top of the compacted backfill must be horizontal and extend outward from the footing for a minimum lateral distance equal to three times the height of the backfill , before tapering down to grade. With backfill placed as discussed, footings may be also designed for passive resistance against lateral translation using an equivalent fluid equal to 325 pcf . This value would also apply where the base of the wall is founded in medium dense native soils. Passive resistance values include a factor of safety equal to 3 in order to reduce the amount of movement necessary to generate passive resistance. 9 The friction coefficient for footings cast directly on undisturbed, medium dense or dense soils may be taken as 0.40. Since it will be difficult to excavate these soils without disturbance , the soil under the footings must be recompacted to 95 percent of the above mentioned standard for this value to apply. 10.0 FLOOR SUPPORT Slab-on-grade floors may be placed over structural fill or pre- rolled , medium dense , natural ground . The floors should be cast atop a minimum of 4 inches of washed granulithic material or pea gravel to act as a capillary break. It should also be protected from dampness by an impervious moisture barrier. 11 .0 DRAINAGE CONSIDERATIONS All retaining and footing walls should be provided with a drain at the footing elevation. Drains should consist of rigid, perforated, PVC pipe surrounded by washed pea gravel (see attached Wall/Footing Drain Detail) . The level of the perforations in the pipe should be set 2 inches below the bottom of the footing at all locations and the drains should be constructed with sufficient gradient to allow gravity discharge away from the building. Roof and surface runoff should not discharge into the footing drain system but should be handled by a separate, rigid, tightline drain that discharges to the site storm drain system. In planning, exterior grades adjacent to walls should be sloped downward away from the structure to achieve surface drainage. 12.0 EROSION MITIGATION The subject site would be characterized as having a moderate potential for erosion. The surficial sediments are generally erodable but site gradients are sufficiently low so that only small erosional forces would be produced. To minimize the potential for offsite sediment transport during construction, we recommend the following: seasonally 1) If possible, time construction to take advantage of son lly drier weather. 2) Construct a silt fence along the lower, northern perimeter of the site. 3) Where channelized flow can occur, utilize check dams to reduce the runoff velocity. 4) If erodable material is to be stockpiled onsite , the stockpiles should be low and covered with plastic sheeting. 10 5) Once the site storm drain system is constructed, runoff should be directed into the system. Temporary drainage system inlets should be protected from siltation by surrounding the inlet with a silt fence or straw bale filter. Permanent erosion control measures would include the following: 1) Cut and fill slopes should be no steeper than a 2H : 1V inclination. 2) Graded areas should be landscaped as soon as possible. 3) All runoff from impervious surfaces should be routed into the site storm drain system. 13.0 ROCKERIES A rockery is currently planned along an approximate 330 foot portion of the north property line bordering Roy Boad Road. This rockery will provide grade separation between the site parking lot and service roads and the lower grade of Roy Boad Road. The rockery will have a maximum height of approximately 4 feet based on the current grading plans. The material behind the rockery will consist of fill required to reach the parking lot grade. For stability of q P g 9 Y the rockery, it is essential that the fill be compacted to a minimum of 95 percent of its maximum dry density prior to rocker P Y n Y P Y II' construction. i In the cut area along the east site boundary, a sloped excavation is planned from the property line down to the edge of the parking lot, located 20 feet inside the property line . The maximum height of this cut will occur at the northern end and will be approximately 14 feet. Since the maximum permanent slope inclination is 2H:1V, up to 4 feet of vertical slope will be required to reach the parking lot grade. A rockery may be utilized to protect this 4 foot vertical section where the cut encounters natural sediments . In the northernmost portion of this cut, fill soils will be encountered, and a concrete retaining wall is recommended as discussed in Section 9.0, Lateral Wall Pressures. ! Rockeries may be used to prevent erosion of slopes, however, they are not engineered structures and we strongly suggest that they not be used in place of retaining walls. In addition, rockeries should not be used in areas where uncontrolled fill exists . Rockery construction is an art which depends largely on the skill of the builder . We would like to point out that although rockeries are commonly used, they should be considered a long-term maintenance item. Care must be exercised in selecting a rock source since some of the material presently being supplied is soft and disintegrates in a relatively short period of time. Samples of rock should be tested by Associated Earth Sciences prior to their use in rockeries to evaluate soundness and durability. 11 The following notes present considerations for the proposed rockery and fill section. A typical sketch is shown in the Appendix. The contractor should confirm that his configuration conforms with any current municipal specifications. 1) The base of the rockery should be started by excavating a trench to a minimum depth of 12 inches below subgrade into firm , undisturbed ground . If loose , soft or disturbed materials exist at the base rock location , they should be removed and replaced with free-draining sand and gravel or crushed rock. This material should be compacted to 90 percent of the Modified Proctor Maximum Density using ASTM:D 1557 as the standard. The gradation of the sand and gravel should be such, that of the material passing the No. 4 sieve, not more than 5 percent by weight should be finer than No. 200 sieve. 2) The base rock should have a minimum width (perpendicular to the line of the rockery) of 1/2 the height of the rockery. All rocks should also meet the following weight requirements: Height of Rockery Minimum Weight of Rock Upper 2 feet 300 pounds Lower 2 feet 800 pounds 3) The rock material should all be as nearly rectangular as possible . No stone should be used which does not extend through the wall . The rock material should be hard, sound, durable, and free from weathered portions , seams , cracks or other defects. The rock density should be a minimum of 160 pounds per cubic foot. 4) Rock selection and placement should be such that there will be minimum voids and, in the exposed face of the wall , no open voids over 6 inches across in any direction. The rocks should be placed in a manner such that the longitudinal axis of the rock will be at right angles or perpendicular to the rockery face. Each rock should be placed so as to lock into two rocks in the lower tier. After setting each rock course, all voids between the rocks should be chinked on the back with quarry rock to eliminate any void sufficient to pass a 2-inch square probe. The rockery should be limited to 4 feet in height for the given minimum rock weight requirements. 5) The rockery backfill should consist of quarry spalls with a maximum size of 4 inches and a minimum size of 2 inches. This material should be placed to a 12-inch minimum thickness between the entire wall and the cut material. The backfill j material should be placed in lifts to an elevation approximately 6 inches below the top of each course of rocks ! as they are placed, until the uppermost course is placed. Any I backfill material falling onto the bearing surface of a rock course should be removed before the setting of the next course. a. 12 6) Asphalt paving should be sloped to drain away from the rockery or a curb provided to direct runoff into a storm drain inlet. 14 . 0 PROJECT DESIGN AND CONSTRUCTION MONITORING At the time of this report , structural plans and construction methods have not been finalized . We are available to provide additional geotechnical consultation as the project design develops and possibly changes from that upon which this report is based. We recommend that Associated Earth Sciences , Inc . , perform a geotechnical review of the plans prior to final design completion. In this way, our earthwork and foundation recommendations may be properly interpreted and implemented in the design. We are also available to provide geotechnical engineering and monitoring services during construction. The integrity of the foundation depends on proper site preparation and construction procedures . In addition, engineering decisions may have to be made in the field in the event that variations in subsurface conditions become apparent. We have enjoyed working with you on this study and are confident that these recommendations will aid in the successful completion of your project. If you should have any questions, or require further assistance, please do not hesitate to call. I'4 Sincerely, ASSOCIATED EARTH SCIENCES, INC. Bruce L. Blyton, Geotechnical Engineer �S401 C�Pl�OS wAsy;�c'l� 3 jGary Lobdell , P.E. , P.G. y Princ ' al Z SS�ONAL ENS/' Gary A. Flowers, P.G. Principal i i BLB/lb A909-23G DK1/1/90 lb 13 i i i 90 p m i -u J Q I I M T I OC Q � � M O / (O %C 0 p o m e J O "' x ea � In d 1 O N W _ N n p 00 N OD cnvNm k = m � OW i e v \ p arM» da �m ". ' C ; / p oD �v n / � CA) °a 3 O b v , p a � rn m p m i r M A e J e OD 9 (0 c \ ae � x 'ro \ p — m 1 A o > rn p rn \ _ -+ e F ; ae »dvo ro e o ,.o r» O e0ae C ;9 d i 0 M R:r-kery Retaining Wall Rc mmended Recommended M m -- — — p -- — CO-- m -- -- D m a?coi AT O i � ° 0. o >O e N ,�XL. O m c v a " '0 Z � O s ome e Z a• M �MD o A mD� ' e w s mO �_� o o Z � m > m � 0 (A M r 02 G) _ t , APPENDIX �I i WALL/FOOTING DRAIN DETAIL USING ONSITE BACKFILL (Typical) A. Washed Drain Rock a Onsite Backfill 4 Vapor Barrier Typical Floor Slab fill 4' Granulithie Material or Pea Gravel Bearing Soil Bottom of 4' Die. rigid PVC pipe 12• a minimum of Z' below the bottom Minimum-1 of the footing. 1• of pea gravel surround pipe. Perforations are in the lower 1/3 of the pipe. i I NOT TO SCALE ASSOCIATED Belfair Center EARTH Belfair, Washington. 14W93CIENCESsINC 8909-23G 1/23/90 ROCKERY DETAILS (NOT TO SCALE) For flat backslope, surface should 2 (or flatter) be impervious i sloped to drainlee . / V min. 1 00 00 o (min.161 00e0 / 6 ° 000 Oe Deo le Upper 2' pp•0•0 2 man rocks •p• / eO 00 e� Height 00 O / / Min. 1 foot wide layer of 2'-4' quarry (max 4' ) 0a 00 //� *palls adjacent to rockery 000 O0 / 000, Stable cut face in natural material Lower 2' 40 see note 4 3 man rocks •e ///DOe 0 08 hei ht .00 (min — ) / 2 V (or less) diameter washed gravel; min. 12 inches i min. 6' cover over pipe; min. 2' gravel under pipe. Firm, undisturbed soil Min. 4' diam. pert. rigid pipe; min. 1% see note i , continous slope to outlet. NOTES: 1. Inspection of subgrade, placement of base course and drainage, and finished rockery by geotechnical engineer is required. 2. Rock shall be sound and have a minimum density of 160 pounds per cubic foot. 3. The long dimension of all rocks shall be placed perpendicular to the wall. Each rock should bear on two rocks in the tier below. 4. Rockeries are erosion-control structures, not retaining walls, material must be stable and free-standing in cut face. Rock LB, 1 man 100-300 2 man 300-800 3 man 800-1500 4 man 1500-2200 5 man 2200-4000 ASSOCIATED Belfair Center EARTH Belfair, Washington. SCIENCES, INC [:8909-23CG. 1/23/90 EXPLORATION PIT LOGS NUMBOER EP-1 SEDIMENT DE801PI N Surface: Weeds and grass Medium dense, dry, brown, silty, sand and gravel with numerous roots in upper 12' 5 Medium dense to dense, damp, grey, sand and gravel with trace 10 silt. Gravel to 4" Dia. 15 BOH 16' Note: No seepage, no caving. NUMBER EP-2 O SEDMENT DESCRWTION Surface: Weeds and grass Medium dense, damp, brown, gravelly, sand with some silt, numerous roots in upper 2' 5 Dense, damp, grey, sand and gravel. Gravel to 4" Dia. 10 15 BOH 16' Note: No seepage, no caving. A8SOCIATEO Belfair Shopping Center EARTH Belfair, Washington. AA SCIENCES, INC 8909-23G Oct. 1989 4� EXPLORATION PIT LOGS NUMBER EP-3 MOMW DEseRP West Fast ,ft Ground Surface Fill Surface: Weeds and grass (E. end) Loose to medium dense, dry, tan, silt, sand and gravel mixture with roots and sticks. (Fill, embankment soils) 5 (W. end) Medium dense, damp, brown, gravelly, sand with some silt and numerous roots in upper 2' 1 0 Dense, damp, grey-brown, sandy, gravel. Gravel to S" Dia. BOH 14' Note: No seepage, no caving NUMBER EP-4 O SEDOrr DESCRIP I Surface: Weeds and grass Medium dense to dense, brown, fine sand with some silt and trace gravel. Numerous roots and organics to 1' depth 5 Medium dense to dense, damp, grey, fine to coarse sand with some gravel, grades to mostly gravel at S' depth. 1 BOH 91' Note: No seepage No caving 15 ASSOCIATED Belfair Shopping Center EARTH Belfair, Washington. SCIENCES, INC 8909-23G Oct. 1989 348 EXPLORATION PIT LOGS NUMBOER EP-5 99DOMM DESCRPTNM Surface: Weeds, grass and sticks. Medium dense, dry, brown, fine sand with some silt and trace gravel. Numerous roots to 11' depth. 5- Medium dense to dense, damp, grey, sand and gravel. Gravel to 4" Dia. BOH 7' Note: No seepage 10 No caving 15 t - - L NUMBER EP-6 sen r T 099c"r Surface: Wood debris. Loose, damp, dark brown, sand and silt with numerous roots and organics. Medium dense to dense, moist, grey, coarse sand. 5 Medium dense, wet to saturated, brown, sand and gravel with some C silt, becoming denser and mostly gravel at 10' depth. 10 i BOH 14' 5 Note: Rapid seepage at 7' depth Some caving below 4' depth 1J 3 � I A88OCIATEO EARTH Belfair Shopping Center SCIENCES, INC Belfair, Washington. 8909-23G Oct. 1989 81-8 EXPLORATION PIT LOGS NUMBOER EP-7 SEDMKW Mcnw-1 Surface: Grass, young alder and willow trees. Loose, damp, dark brown, sand and silt with numerous roots and organics. Medium dense, damp, grey, fine sand. 5 Medium dense, saturated, brown, fine to coarse sand and gravel. Gravel to 2" Dia. 10 BOH 10' Note: Rapid seepage below 6' depth Severe caving below 5' depth 15 NUMBER EP-8 0 eEDMME/R OE"Mrraa Surface: Grass and weeds. Loose damp, dark brown, sand and silt with numerous roots and organics. (Fill) Medium dense, damp, brown, fine sand with some silt. 5 Medium dense, damp to saturated, grey, sand and gravel with trace silt to no silt. Highly oxidized at 8' depth. 10 BOH 10' Note: Rapid seepage below 7' depth Caving below 6' depth 15 A88OCIATEO EARTH Belfair Shopping Center SCIENCES, INC Belfair, Washington. 8909-23G Oct. 1989 13CB EXPLORATION PIT LOGS NUMBER EP-9 sEDE oEscRan Surface: Grass and weeds. Medium dense, dry, dark brown, sand and silt with trace gravel and numerous roots. Medium dense, dry, brown, sand and gravel with some silt, 5- silt content decreases with depth. Medium dense to dense, damp, grey-brown, sand and gravel, becomes mostly gravel and wet below 8' depth. Rapid seepage and running gravel below 9' depth. 10 Medium dense to dense, saturated, grey, fine sand with trace silt. 15 BOH 14' Note: Seepage and caving from 6'-10' depth NUMBER EP-10 O WDNVff DESCHre Surface: Sod Medium dense, dry, grey-brown, fine sand with some silt and numerous roots in upper 6" Medium dense, dry, brown, fine sand with trace silt and some small gravel. 5- Medium dense to dense, damp, p grey, sand and gravel. BOH 6' Note: No seepage No caving 10 15 ASSOCIATED EARTH Belfair Shopping Center SCIENCES, INC Belfair, Washington. 8909-23G Oct. 1989 gig i EXPLORATION PIT LOGS NUMBOER EP-11 SEDIMENT DESCRWTION Surface: Grass and weeds. Medium dense, dry, grey-brown, sand and silt with numerous roots in upper 1' . Fill Medium dense, dry to damp, brown, sand with some silt and trace gravel. 5 Medium dense to dense, damp, brown to grey, sand and gravel, gravel content increases with depth. Gravel to 4" Dia. 10 BOH 10' Note: No seepage No caving 15 NUMBER EP-12 0 SEDOWU DESCRr'I Surface: Grass, weeds and sticks. Medium dense, damp, brown, silty, sand with numerous roots. (Fill Medium dense, damp, brown, sand with some silt and trace gravel. 5 Medium dense to dense, damp, grey-brown, mottled, sand and gravel. Becomes wet below 9' depth. 10 Medium dense to dense, saturated, grey, fine to medium sand with trace gravel. BOH 12' Note: Seepage below 11' depth 1 5 Minor caving below 10' depth. I f A88OCIATEO EARTH Belfair Shopping Center SCIENCES, INC Belfair, Washington. 8909-23G L Oct. 1989 80 EXPLORATION PIT LOGS NUMBER EP-13 sEo�Eur�EscR�raN Surface: Grass, weeds and young alder trees. r� :and edium dense, moist, brown to grey, fine sand with some silt numerous roots. (Fill) 5— Medium dense, moist, grey, fine sand, becomes denser with depth. Medium dense to dense, saturated, grey-brown, sand and gravel 10 with trace silt. BOH 10' Note: Seepage and caving below 8' depth 15 NUMBER EP-14 O eEoNEW DESCIWTM Surface: Grass and weeds. Medium dense, dry, brown, sand, silt and wood mixture. Strong organic odor, logs to 8" Dia. (Fill) Medium dense, damp to moist, brown, fine to medium sand with 5— trace silt and gravel. Medium dense to dense, moist to saturated, brown, sand and gravel with trace silt, mostly gravel to 2" Dia. to 8' depth. 10 BOH 9' Note: Seepage below 6' depth Caving below 3' depth 15 ASSOCIATED Belfair Shopping Center EARTH Belfair, Washington. INC E/AMASCIENCESs -23G Oct. 1989 8Lb EXPLORATION PIT LOGS NUM O R EP-15 aN sEoWKr oEscnrr Surface: Grass, weeds and sticks. Medium dense, dry, brown, fine to coarse sand with trace to some silt and gravel. Numerous roots in upper l' 5— Medium dense to dense, dry, brown, sand and gravel with trace silt, becomes grey at 7' depth. 1 BOH 9' Note: No seepage No caving 15 NUMBER EP-16 sEo�oEOCRr WH Surface: Weeds. Medium dense, dry, brown, fine to coarse sand with trace to some silt. Roots in upper 8". 5 Medium dense to dense, damp, grey-brown, sand and gravel with trace silt. 10 BOH 14' 1 5 Note: No seepage Caving of south pit wall below 4' depth A8S0CIATEO Belfair Shopping Center EARTH Belfair, Washington. SCIENCES, INC 8909-23G TOct. 1989 SO i EXPLORATION PIT LOGS NUM 0 REP-17 BEDWENT DESCRInM Surface: Grass and weeds. Medium dense, dry, brown, fine to coarse sand with trace silt and gravel. Numerous roots in upper 1' . 5 Medium dense to dense, damp, grey, sand and gravel. Gravel to 4" Dia. BOH 7' Note: No seepage 10 No caving I 15 NUMBER EP-18 � sEDMMENT DEscRwTaN Surface: Grass and weeds. Medium dense, dry to damp, brown, fine to coarse sand with trace silt and gravel. Numerous roots in upper 1' . 5 Medium dense to dense, damp, grey, sand and gravel, mostly gravel below 6' depth. BOH 7' Note: No seepage 1 0 No caving 15 ASSOCIATED Belfair Shopping Center EARTH Belfair, Washington. SCIENCES, INC 8909-23G Oct. 1989 ate E0 9 Y EXPLORATION PIT LOGS NUMBER EP-19 SEDIMENT DESCRII'10N Surface: Weeds and sticks. Medium dense, dry, brown, sand and gavel with some silt and numerous roots in upper 1' . 5 Medium dense to dense, damp, brown—grey, sand and gravel with charcoal and wood fragments. 10 BOH 10' Note: No seepage No caving 15 NUMBER EP-20 0 SEDWOfT DESCRIPI Surface: Bare scattered gravel. Loose to medium dense, sand and gravel. (Fill) Medium stiff, black, sandy organic silt and wood debris, logs to 6" Dia. (Fill) 5 i Loose, saturated, grey, sand and gravel with some silt. 10 Box 12' Note: Rapid seepage below 6' depth Severe caving below S' depth 15 ASSOCIATEO Belfair Shopping Center EARTH Belfair, Washington. SCIENCES, INC E09-23C Oct. 1989 aL8 F EXPLORATION PIT LOGS NUMBOER EP-21 •lDMENT OElCl1!'f10N Medium dense, damp, grey-dark brown, gravel and sand mixture with some silt and wood debris. (Fill) 5 Medium dense, saturated, brown, sand and gravel with some silt. 10 BOH 10' Note: Seepage below 6' depth Minor caving below 5' depth 15 NUMBER EP-2z � oEscRanoM Surface: Wood shavings. Loose to medium dense, sand and gravel. (Fill) Medium stiff,moist, very dark. brbwn, silt, sand and wood 5— mixture. (Fill) Dense, wet, grey, sand and gravel. BOH 61' Note: No seepage 1 O No caving 15 ASSOCIATED EARTH Belfair, Shopping Center SCIENCESs INC Belfair, Washington. 8909-23G L �Oct. 1989 8l,B i EXPLORATION PIT LOGS NUMBER EP-23 SEDWNT DESCRWTM Medium dense, dry to damp, dark brown, silt, sand and gravel mixture with wood debris. (Fill) Medium dense, damp, brown, gravelly, sand with trace silt. 5 BOH 6' Note: Seepage below 5' Minor caving 10 15 i i NUMBER EP-24 71 SEDMENT DESCRlT10N Surface: Bare gravel. Medium dense, dry to damp, sand and gravel. (Fill) Loose to medium dense, damp, grey, fine sand with wood and organic fragments. (Fill) 5 Medium dense, damp to moist, grey, fine sand. BOH 5' 1 Note: No seepage No caving I 10 I 1 i 15 3 i 1 ASSOCIATEO EARTH Belfair Shopping Center SCIENCES, INC Belfair, Washington. 8909-23G Oct. 1989 C31,� E0 9