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HomeMy WebLinkAboutWHEATON WAY, 2025General Testing Laboratories, Inc. 18970 3rd Avenue NE, P.O. Box 1586, Poulsbo, Washington 98370, (206) 779-9196 2601 70th Avenue W., Suite L, Tacoma, Washington 98466, (206) 272-6 • (206) 565-8110 October 22, 1984 Project B-6828 Gary Lindsey P.O. Box 56 Silverdale, WA 98383 Re: Soils and Foundation Investigation Port Washington Narrows Bremerton, Washington Gentlemen: This report presents the results of our soils and foundation investiga- tion at the referenced site. The site is located on Wheaton Way and overlooks the east side of the Port Washington Narrows in Bremerton, Washington. Our work was verbally authorized by Mr. Gary Lindsey on October 11, 1984. General The planned structure will be two stories in height and roughly square in shape with foundation plan dimensions on the order of 46 feet by 40 feet. The main west foundation line will be ten feet east of the steep downward slope to Port Washington Narrows, An exterior line of piers is planned west of the main west foundation line, and retaining walls of varying heights will be constructed along the north and east foundation lines. The planned construction will incorporate both concrete and wood materials. The foundation design plans have been completed and are based on an assumed allowable soil bearing of 2000 psf. The lower level of the structure will have a slab -on -grade floor at elevation 59.0. Extensive filling and regrading of the parking area will be required to bring that portion of the site up to the desired grades. Site Conditions The proposed building area is nearly level, sloping slightly towards the west while the parking area slopes fairly steeply downward, towards the west, from Wheaton Way. The total topographic relief across the proposed development area is on the order of 16 feet. That portion of the property not designated for development slopes steeply downward to Port Washington Narrows with slope angles ranging from 40 degrees to near vertical with a vertical height of about 50 feet. Gary Lindsey October 22, 1984 Project B-6828 Page Two At the time of our fieldwork, the building area had been cleared and grubbed and all of the large trees on the slope to Port Washington Narrows felled. The limbs and other debris from the felled trees had been left on the slope. No groundwater or seepage vas observed in the area of proposed development or in the upper portion of the slope to Port Washington Narrows. Subsurface Exploration Program The subsurface exploration program consisted of logging a series of four test pits across the site and making a reconnaissance of the site and adjacent areas. The test pit locations were selected and the excavations logged by an engineering geologist from our office who examined the soils exposed, and evaluated the difficulty of excavating the soil as an indication of its relative density. The soil strata shown on the test pit logs were observed at spot locations across the site. Actual subsoil conditions between test pit locations and exposed in excavations may vary from those shown on the test it logs. The test pit logs are presented at the end of this report and the test pit locations are shown on Figure 1. Subsurface Soil Conditions Based upon the results of our subsurface exploration program, it appears that the upper 1.0 to 1.5 foot of soil consists of silty sand with some gravel in a very loose condition. Based upon the appearance of the material and presence of roots, sticks and limbs (test pits 2 and 3), we believe that this unit was disturbed and mixed during the previous stripping and grubbing of the site. In test pit 3 this unit extends to a depth of 3.0 feet with only the upper 1.5 feet disturbed and mixed with debris. .Underlying the uppermost soils is a layer of loose sand which ranges in thickness from about 1.0 to 1.5 feet. In test pit 3 gravels are mixed with the sand. The lowermost unit encountered in test pits 1 and 2 consists of a medium dense sand and gravel, while in test pits 3 and 4 the lowermost material consists of a medium dense sand with a trace of silt and gravel. Gary Lindsey October 22, 1984 Project B-6828 Page Three Moisture contents of the soils encountered ranged from very moist to moist at the surface, caused by recent heavy rainfall, to damp or dry at depth. RECOMMENDATIONS Site Preparation All building, pavement and fill areas should be stripped of any remaining vegetation, existing fill or other deleterious materials. Over most of the site this will be a matter of inches, locally extending to a foot or so. Test pit excavations should be dug out sufficiently to permit refilling using heavy equipment. A clean excavation with no lenses of loose backfill is important. Stripped soil should be wasted, or the portion relatively free of organic material and debris could be used in landscape areas. Areas which will require filling to bring site grades up to the desired underslab/pavement grades should be filled using granular material free from roots, trash, wood waste, organics or other deleterious material. The granular on -site soils will be suitable for use as fill, Imported materials should conform to the following gradation' limits: U.S. Standard Percent Passing Sieve Size By Weight 22" 100 #4 25-100 #10 10-80 #40 0-35 #200 0-5 Following the stripping and grubbing of in the construction area or where fill is to the Gary Lindsey October 22, 1984 Project B-6828 Page Four All fill materials in loose thickness and to at least 95% of its Foundation Support should be placed in lifts not exceeding eight inches thoroughly compacted by suitable vibratory equipment maximum dry density as determined by ASTM D-1557. We recommend that individual columns and load -bearing walls be supported on spread and continuous footings respectively. Foundations east of building Line 2 should bear on the medium dense sand and sand and gravel at depths of two to three feet below the existing site grades. Foundations west of and including building line 2 should be embedded into the medium dense soils at least 18 inches. An allowable soil bearing capacity of 2000 psf is recommended for the design of footings. However, continuous footings should not be less than 16 inches wide and isloated footings should measure at least 18 inches in their smallest dimension, regardless of the resulting bearing pressure. All footings should bottom a minimum of 18 inches below the lowest adjacent exterior finish grade and be at least 12 inches below the lowest adjacent interior slab grade. It is recommended that all footing excavations be inspected prior to placing concrete and any disturbed soil removed. Settlements, for foundations designed and constructed as recommended, are estimated to be less than one inch. Slab -On -Grade Floors Due to the very loose to loose nature of the near surface soils, we recommend that slab subgrade areas be over -excavated a minimum of one foot and the subgrade rolled and the area refilled as described in the Site Preparation section of this report. Following refilling and compaction of the slab area, a capillary break consisting of four inches of clean, coarse sand and gravel or crushed rock should be placed below the floor slab. The capillary break material should contain less than 3% fines (material passing a U.S. standard #200 sieve). A vapor barrier should be placed between the capillary break and the floor slab. Outlets should be provided so that any water which accumulates in the capillary break may escape. Gary Lindsey October 22, 1984 Project B-6828 Page Five Site Drainage and Moisture Protection Generally, groundwater is not expected to create any problems during or after construction. However, to preclude the possible build-up of groundwater or storm runoff in the soils adjacent to the building, it is recommended that a four inch diameter perforated pipe be placed, perforations down, around the outside of the building foundation at the footing subgrade elevation. All of the drainage system should be bedded in pea gravel and designed to carry any accumulated water away to the storm drainage system or offsite. Offsite discharge should not be allowed where the waters will hazard soils, slopes, retaining structures or property. All storm water runoff from roofs, patios, decks and parking areas should also be collected and discharged into the storm drain system or offsite. If offsite discharge is employed for disposal of storm and/or ground - waters, we recommend that such a system tight -line all of the collected water to the beach. No surface water should be channeled or allowed to drain into the perforated subdrains. The two water collection systems should remain separate unless an offsite discharge system is used in which case the two drainage systems may be connected into a common tight -line 15 feet downslope of the structure. In addition, all foundation backfill and soils used in landscaping should slope away from the building for a distance of at least five feet. Slope Protection and Maintenance Slopes similar to those on the western end of the site have remained stable for varying periods of time. Similar slopes have remained relatively unchanged for periods of 15 to 20 years or more. The length of time a slope area is stable is highly dependent upon the intensity of winter storms, modifications to the slope (undercutting of the slope, removal of vegetation, loading, etc.), and on the efficiency of measures taken to protect the slope toe and to divert surface water runoff from flowing toward and over the top or across the slope. The past history of slope recession in similar areas indicates these longevity estimates are reasonable; however, no guarantee can be, or is made in this regard. Gary Lindsey October 22, 1984 Project B-6828 Page Six As a general rule, we strongly recommend that efforts be made to protect all slope areas by planting deep-rooted, fast-growing trees, shrubs and other types of vegetation, and controlling water runoff. However, some erosion of the protected slope may still be anticipated due to natural runoff and weathering of the slope. In addition, there is substantial evidence to indicate that certain actions will accelerate the deterioration of the slope. Any cutting of the existing deep-rooted vegetation, trees or brush which tend to anchor the soil, or any action which tends to retain or accumulate moisture or loading at the top of the slope would adversely affect the slope. Finally, although the Puget Sound region is not noted as being overly active seismicly, some quaking does occur and could cause a large soils movement if other conditions are favorable. Based upon our observations, it does not appear that the existing slopes require the addition of structural support at this time. However, we do make the following recommendations. First, all of the logs and limbs from the felled trees should be removed along with any other debris and no additional dumping of debris over the slope should be allowed. Second, no storage of construction materials should be allowed west of the building. Third, the re-establishment of deep-rooted, fast-growing trees and shrubs is strongly recommended. Fourth, periodic inspections of the slope area should be made to check for increased erosion rates or other signs of slope distress which could indicate the need of additional protective measures. Please call our office if you have any questions regarding this report or if we may be of additional service. Respectful f su mitted, GENER �' T LABORATORIES, INC. A en Ly`�- a r t Engineering Geologist PORT WASHINGTON NARROWS Bremerton, tJashin�ton Project 8-6828 Wheaton Way Property Line ®3 4 • � �- .' �. J � �- Foundation Line ---, 2------------1®- Port Washington Narrows FIGURE 1 1 ® Test Pit Number and Location Scale 1" = 20' Top of Bank North General Testing Laboratories, Inc. SITE PLAN _�� TEST PIT 1 Depth - Feet Soil 0.0 - 1.2 Dark brown, silty SAND with some gravel (Very loose, very moist becoming moist)(Disturbed soil zone) 1.2 - 2.3 Light brown to tan SAND (Loose, damp becoming dry) 2.3 - 6.0 Tan to gray SAND and GRAVEL, trace silt with lenses of clean sand (Medium dense becoming dense, dry) No groundwater observed TEST PIT 2 Depth - Feet Soil 0.0 - 1.0 Dark brown silty SAND with some gravel mixed with roots, limbs and sticks (Very loose, very moist becoming moist) (Disturbed soil zone) 1.0 - 2.8 Light brown to tan SAND (Loose, damp) 2.8 - 6.0 Tan to gray SAND and GRAVEL occasional cobbles and boulders (Medium dense becoming dense, dry) Root zone extends to 2.2 feet No groundwater observed FIGURE 2 Depth - Feet TEST PIT 3 Soil 0.0 - 3.0 Dark brown silty SAND with some gravel mixed with roots, limbs and sticks in upper 1.5 feet (Very loose becoming loose, very moist becoming moist) (Disturbed soil zone) 3.0 - 4.7 Brown to tan gravelly SAND grading to SAND and GRAVEL (Medium dense, moist becoming dry) 4.7 - 7.5 Gray to tan SAND with .trace silt and gravel (Medium dense, dry) Root zone extends to 2.5 feet No groundwater observed TEST PIT 4 Depth - Feet Soil 0.0 - 1.0 Dark brown silty SAND with some gravel,mixed with limbs and roots (Very loose, very moist becoming moist)(Disturbed soil zone) Light brown SAND with trace silt (Loose, moist) 2.1 - 7.8 Gray SAND with some gravel, trace silt (Medium dense, dry) Root zone extends to 2.0 feet No groundwater observed FIGURE 3 • �a •�• i Sjj•-�•• • GAp,Y LINDSEY• iN & CAJ�DLE LOIDHAMER BUILDING AREA: LOWER 1933 SQUARE FEET aU TOTAL 3799 SQUARE FEET I � a•�pp a C f I z f 1" : 10'-0 V/1 ;7 I � i I i G� I I. 0000 l l eL ' PLAN / LANDSC A zf �83 Gu1T=R !o' ��-R g C a r i 16 r J� ax i 'A; _✓ i =Xwoo 1r era"+ �"• bJ.N1 Ez�FY ��TI� i N>rw cc�-iG 5�. 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