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HomeMy WebLinkAbout721022006 Geotech Assessment& ASSQCIATES.INC. GEOTECHNICAL ENGINEERING ENVIR©NMENTAL ENGINEERING CONSTRUCTION TESTING $z INSPECTION May 16, 2040 Mr. Ken Hagerman 22340 Miller Bay Road NE Poulsbo, Washington 98370 I2E: Limited Slope Assessment Proposed Hagerman Residence Shine Road Port Ludlow, Washington Dear Mr. Hagerman: KA Project No. Ob2-00028 In accordance with your request, we have completed a limited slope assessment of the subject property located along Shine Road and Highway 104 in Port Ludlow, Washington. The purpose of this assessment was to determine whether the proposed residential development would significantly impact the stability of the slope at the site. This work was performed in general accordance with our proposal dated March 4, 2000, which was signed by you on March 5, 2000. The subject site is located north of Shine Road in Port Ludlow, Washington and is located within Section 2, Township 27 North, Range ] East and shown on Figure 1. We understand that design of the proposed development is currently underway. On a preliminary basis, we understood that the development will consist of a two-story, wood frame, single-family structure with a daylight basement and detached garage/workshop. At the time of the report, the exact dimensions of the proposed development for the structure footprint were not available. The proposed building pad area for the residence is on a descending slope. The proposed garage/workshop building area is on a relatively level plateau with minimal grading anticipated. Footing loads are anticipated to be light to moderate. A representative of Krazan performed a site reconnaissance visit on May 11, 2000. A vegetated pathway off of Shine Road provided access to the site. In general, the entire parcel was heavily vegetated, consisting of ferns, grasses, nettles, and blackberry shrubs as well as firs and maples. At the time of the site visit, the parcel consisted of a heavily vegetated plateau that was partially forested on the western half, with a gently descending slope with an approximate 3H:1V (Horizontal to Vertical) ratio beyond to the south. The northern portion of the parcel was a vegetated, descending slope with an approximate 2H:1V ratio, ranging in height from 15 to 25 feet, and terminated at State Route 104. The southern portion of the parcel was a descending slope with an approximate 2H:1V ratio, ranging in height from 4 to 10 feet, and terminating at Shine Road. The western portion of the parcel consisted of a small ravine trending north /south. The ravine was heavily vegetated. No surface water was noted during the time of the site visit. It is our understanding that the subject parcel was lagged approxi~ey- # -----~----d- Ten Offices Serving The Western United States 383 Northwest Equestrian Drive •Poulsbo, Washing on 98370 • {350) 598-2226 • ~ ~~ -~ ~~ ...q..~ ..,_. ~2t~~u~a~i`~QzVsI.~Pht~`~~T" KA Project Ivo. 452-0002$ Page No. 2 The subject site lies within the central Puget Lowland. The lolvland is part of a regional north-south trending trough that extends from southwestern British Columbia to near Eugene, Oregan. North of Olympia Washington, this lowland is glacially carved, with a depositianal and erosional history including at least four separate glacial advancelretreats. The Puget Lowland is bounded on the west .by the Olympic Mountains and on the east by the Cascade Range. The lowland is filled with glacial and nonglaeial sediments consisting of interbedded gravel, sand, and silt, till, and peat lenses. The USGS Seattle, Washington Quadrangle Geologic Map, indicates that the site and vicinity are in an area mapped as Vachon Tiil consisting of a Tight to dark gray, non-sorted, non-stratified mixture of clay. silt, sand and gravel up to boulder-size (diamicton}. The till is very stiff and impermeable, ofren resulting in poorly drained bogs developing on the unit in relatively flat areas. It often contains minor amounts of interbedded stratified sand and gravel, sometimes separating the till into multiple sheets. The till generally overlies advanced outwash deposits. The USDA Sail Conservation Services (SCS} Soil Survey for Jefferson County Area, Washington maps native soils in the project vicinity as belonging tQ the group known as Kitsap silty loam usua}ly found on 15 to 30 percent slopes. These moderately well-drained soils formed in glacial lacustrine or marine sediments and are typically found on upland benches, terraces, canyon slopes and ocean bluffs. According to the SCS, the USDA texture for these soils is silty loam. Kitsap silty loam soils are described as having the following characteristics: medium to rapid runoff, the hazard of erosion and slippage are moderate to severe, a low to moderate shrink swell potential, and a moderate risk of corrosion to uncoated steel and concrete. According to the Slope Stability Map of the Uncas-Port Ludlow Area, Jefferson County, Washington, the area south of the proposed building site appears to be in a known area of recently active rapid downslope movement. While the site vicinity in close proximity to the Hood Canal has had recent landslide activity, there was no visible evidence of landslide activity on the subject site and adjacent parcels. The Geology and Groundwater Resources of Eastern Jefferson County, Washington, classifies the subject site to. be in an area referred to as the Chimacum Drift Plain. Over 130 wells were examined in this area, ranging from dry to some of the most productive wells in the area. The majority of groundwater being withdrawn is for domestic purposes. The residents of Quilcene rely on private wells for their water consumption. The Chimicum area is supplied by the City of Port Townsend, who diverts water from the Quilcene River and the development at Port Ludlow is supplied by water from various wells located in the uplands west of Port Ludlow. Research of documents did not indicate the presence of any springs within 1,004 feet of the subject property. In addition, a windshield reconnansance of the site vicinity did not show any visual indications of springs nearby. Based on our site reconnaissance, our research, and our experience with projects of similar nature, Krazan and Associates offers the following: • Based on the geology, the gradual steepness of the slope and our observation of the site conditions, the proposed development does not appear to pose a significant impact to the subject site. The site is mapped in an area of very dense soil conditions and at the time of the site visit, there was no visual evidence of slops failure on the subject site or adjoining properties. Krazan & Associates, Inc. Ten Offices Serving The Western United States 052-C0028Shine Road Sita Assrssmerst KA Project No. 062-00028 Fage Na. 3 • There was no visible evidence of water ponding on the site or water seepage, erosion andlor weeping on the slope face, at the time of our site visit. It is recommended that water runoff from the roof of the proposed residential structure and the garageJworkshop be tightlined to discharge at the base of the slope into the ditch, which is parallel to Shine Road. The slopes not affected by the development should remain vegetated to prevent erosion and infiltration of the soils. ~ It is recommended that Krazan & Associates review the final design including the landscaping plan to verify our assumptions concerning the proposed development. • It is recommended that a representative of Krazan & Associates view the excavated footings for the proposed residence prior to the placement of concrete in order to verify the footings are founded in suitable load-bearing soil. Reviewed Documents for this letter report were as follows: USGS Topographic Map, Lofall Quadrangle, Washington, dated 1953 and revised 1968. USGS Seattle, WA. Geologic Map U. S. Department of Agriculture, Soil Conservation Service of Jefferson County Area, Washington, dated 1975. Slope Stability Map of the Uncas-Port Ludlow Area, Jefferson County, Washington, dated 1976. Geology and Ground-Water Resources of Eastern Jefferson County, Washington, dated 1981. I# should be noted that no subsurface exploration or soil sampling was performed as part of this limited assessment. The geotechnicai engineer warrants that the findings; recommendations, specifications, or professional advice contained herein have been made in accordance with generally accepted professional geotechnical engineering practices in the local area. No other warranties are implied or expressed. if you have any questions, or if we .may be of further assistance, please do not hesitate to contact our office at (360) 598-2126. .~ SEW/TGB:ksm Respectfully submitted, KRAZAN & ASSOCIATES, INC. ~~ ~/ Shawn E. Williams Senior Environmental Geologist Timothy G. Beckerle, P. E. Engineering Manager Krazan & Associates, Inc. Ten Offices Serving The Western United States 062.OQO?S•Stune Road site Assessment sxa~RES: iarior by ~ - ~ ~ ij ~ 1 ! r/' ~ ~ ~ _ i t / ~ ~ f S ) 1 t ~ ~f ~~ ~~ ~ ~, ~ ~ / ~' 'tiy.i i ~. ~ f ~ t t.; - ,r ,~ ~ ~ ~~ ar'i ~ s` ~ _~ t ~~1~~ ~ ~ a ~ - f i ~ i ~ ;E~ ~I _ft 3 ~~/ t fa ~ [ ~ / .-~ - ~ iJ~, t i~ L ~~ ~ ~ l ` ~ ~~ _ ~~ 1~ C1 i li ~ ~~ r ti ~~ .b'it' h\ ~ _ ~# ,~~ ~ ` ~ t~` ~ `\ ~lJ / \ / 1 ~ t i s ...~~., f , 30c~ J h _.~ ` ;;~~\~~~ ~ ;( `1~- // ~ .!~ j ';~ ~~~` Lim ai k t\ ~. ~, ~L : ~ ' ~ ~~, ,~ 5.-~ \~, ~ ~ t :-~~',~ J ~ ~ ~1 i no' ,~ ~ ~ f~~ Mid ~~~ ~ t '~\ ~ /~~ ~-._._ i - _ ~-. _ - -_ _ Nate: Map adapted from USGS 7.5 Lafall, WA. dated 1953 and revised 196$. FIGURE 1-VICINITY MAP KRAZAN & ASSOCIATES, iNC. 383 EQUESTRIAN DRIVE POULSBO, WA 98370 360-598-2126 Location: Jefferson County, Washington Job No.: 062-00028 Client: Mr. Ken Hagerman Date: 5-8-fl0 ~ ~ ,~ ~ r--. ~ ~ .i i , ~ '1 ~~. 7 i