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HomeMy WebLinkAbout601283014 Geotech AssessmentNT/ JLS GROUP~ INC. NORTHWESTERN TERRITORIES, INC. A JLS GROUP COMPANY 717 SOUTH PEABODY STREET, PORT ANGELES, WA 98362 [] Engineers [] Land Surveyors [] Geo/ogists [] Construction Inspection [] Materia/s Testing (360) 452-8491 FAX 452-8498 www. nti4u.com E-Mail: info@nti4u.com GEOTECHNICAL REPORT For Tax Parcel #.601283014 Located in Section 28, Township 26 North, Range 1 West, W.M. Jefferson County, Washington Prepared for PATRICK and JENNIFER SHELDON Prepared by NORTHWESTERN TERRITORIES, INC. 717 S. Peabody Street Port Angeles, Washington 98362 Phone 360-452-8491 Fax 360-452-8498 Email info@nti4u.com Web www.nti4u.com January 23, 2003 GEOTECHNICAL REPORT FOR TAX PARCEL NO. 601283014 January 23, 2003 Patrick and Jennifer Sheldon 5725 Ward Avenue NE Bainbridge Island, WA 98110 Subject: Geotechnical report for the property described as Parcel # 601283014, in Section 28,-Township 26 North, Range 1 West, W.M., Jefferson County, WA. Dear Mr. And Mrs. Sheldon: Introduction At your request, Bill Payton of Northwestern Territories, Inc. conducted a geotechnical inspection of the above mentioned property on January 14, 2002. The purpose of this inspection was to examine the proposed homesite at the subject property by visual means and make recommendations regarding the development of the property in accordance with the Jefferson County Critical Areas Ordinance. It is our understanding that you desire to construct a home on the subject property. Improvements to the property currently include a driveway and septic system. Site Conditions The subject property is located off of Seahawk Drive west of Coyle on the Toandos Peninsula. The property is hilly with a marine bluff roughly 75 feet high along the north and northeast sides (Photo 1 ). A small creek flows eastward along the base of the bluff and empties into a small inlet east of the property. The distance from the base of the bluff to the shore of Dabob Bay is roughly 120 feet. The property is predominantly vegetated with young to mature native trees, brush and grass.'AIthough some areas have been cleared for development (Photo 2). Some of the trees on the bluff face have curved trunks, suggesting that shallow slope creep of the surface soils is occurring. A portion of the bluff face near the west end of the property has been thinned of vegetation. This area is also the site of a recent slide that reportedly occurred in February of 2002. The slide began roughly 20 feet below the top of the bluff and is approximately 35 feet wide and 3 to 6 feet deep. The slide scar is devoid of vegetation. Ongoing erosion of the bluff faCe .in the area of the slide scar is eVidenCed by severaI gullies. No seeps or springs were nOticed on the property. small The average slope angle of the marine bluff is approximately 38 to 40 degrees (78-84%). On the east side of the property, the bluff overloOking the inlet is approximately 25 to 30 degrees (47-58%). There is an existing septic tank and two drainfields on the west side of the property (FigUres 1, 2 and 3). The subject property and the adjacent property to the west share a common drainfield location, which bisects the property boundary. The septic system plans indicate that the pump chamber is 40 feet from the top of the bluff. The drainfields appear to begin about 60 feet back from the edge of the bluff and continue southward for roughly 60 feet. South of the drainfield, the septic plans-show a curtain drain oriented in an east-west direction and it appears to be draining toward the bluff to the north. No tightline was noticed for this drain and it is suspected that the drain empties near the top of the bluff. The driveway runs northward along the west property line, turns eastward just south of the septic tank and ends at the top of the bluff on the east side of the property at the head of a drainage corridor. There is a culvert under the driveway south of the septic tank which drains into the above mentioned drainage corridor and then into the previously mentioned inlet. A ditch along the east side of the driveway drains north then east into the drainage corridor. Site Geology The Soil Survey of Jefferson County maps the soil at the property as the Hoypus gravelly loamy sand, 30%-50% slopes (HUE) (Figures 4, 5, and 6). This soil is described as having formed in glacial outwash on terraces and is found on the side of ravines and waterways. Runoff is medium to rapid and the hazard of water erosion is moderate to severe. The Coastal Zone Atlas of Washington maps the sOil at the subject property Undifferentiated stratified sediments older than the Vashon lodgement till (Qpf) (Figure 7). This soil'is described mainly sand and gravel, but in some areas contains silt, clay, peat and possibly till. The Atlas labels the slope stability of the property as Unstable (U). The Department of Ecology's Geology and Ground-Water Resources of Eastern Jefferson County, Washington maps the soil at the property as Undifferentiated glacial, fluvial, glaciofluvial, lacustrine and glaciolacustrine deposits. This includes sediments resulting from pre-Frasier Glaciations (Possession Drift, Double Bluff Drift), interglaciation (Whidbey Formation), and advance outwash sands of the Fraser Glaciation ~_[~ ¥,~.~., 2 Visual observations of the slide Scar On the bluff face revealed the upper material above the head of the slide Scar to be compact silty,~ sandy gravel while the loWer material consisted of stratified sand and gravellY sand. Conclusions and Recommendations: There has been recent slide aCtivity on the blUff face and there are old slide scars Visible elsewhere on the bluff. It appears that the main caUse of the slides is saturation of the sandy soils by groundwater during the wet season. When the soil becomes saturated; the pOre water pressure between the soil grains increases resulting in a reduction in the strength of the soil. Usually, these types of slides in sandy soil are relatively shallow as evidenced by the geometry of the most recent slide. The potential fOr future .SlideS still exiSts and should, be expected. Sandy soil is most stable at angles less than arOund 33-37 degrees (termed the "angle of repose"). Most of the bluff at the propertY is Slightly over this threshold, which also contributes to the potential fOr slides, especially when the soil is weakened due to saturationl If the top of bluff were to recede-back to its angle of repose, anYWhere from 10 t° 30 feet-Could be lost. The sloPes on the east side of the property near the above mentioned drainage corridor are less than the angle of repose and are thus more Stable. The toe of the bluff is relatively well protected from wave erosion but may experience occasional erosion during Storms. The~stream along the base of the bluff appeared relatively benign-at current water levelS but may alsO cauSe erosion to the toe of the bluff during periods of higher flOw. Based upon visual observations of the subject property, we recommend that the setback distance from the Proposed home to the tOp of the bluff on the north 'Side be at least 60 feet. This distanCe should provide a safe buffer in case of fUture shallow slides on the bluff face. And, we recommend that the setback diStance from the house to the top of the blUff on the east side, where the bluff is less than the angle of repose, be at least 35 feet. These setbacks maY necesSitate a reconfiguration of the eXisting driveway and drainage Structures. The following recommendations should'be considered With regards to development of the subject property: · It will be necessary to maintain ground cover t° reduCe erosion from surface runOff. Any bare areas that develop on the upland or bluff should be revegetated. Native deep-rooted vegetation that requires little-or no irrigation would be the most benefiCial The established live vegetation on the bluff should be left undiSturbed except for minor pruning for view enhancement. Any dead trees shoUld be cut to reduq~:~~-g~¢C~d~\~y~ i L . . windthrow, but the stumps should be left in place to avoid exposing bare soil. Heavy irrigation or other activities that would contribute large quantities of water to the soil should be avoided. One cause of landslides is the presence of excessive groundwater in the soil. . Surface runoff from hard surfaces such as roofs, driveways, walkways and patios should be controlled and routed to the toe of the bluff via tightline. A possible route may be down the drainage corridor on the east side of the property mentioned earlier. Surface water discharge to adjacent properties should not exceed predevelopment conditions. An engineered drainage control plan should be developed for this property to address these issues. 4.' The water from the curtain drain should also be directed to the toe of the bluff via tightline. . Silt fences or other sediment control devices may be needed during construction so that sedimentation onto adjacent properties does not exceed predevelopment conditions. . All drainage control devices should be maintained in good working order and inspected at least once a year. 7. The erosion of the bluff face by surface water runoff needs to be prevented as much as possible, especially in the area of the slide. It may be possible to construct a shallow berm or ditch across the upland several feet back from the top of the' bluff and direct the discharge towards the drainage corridor on the east slope, tying into the recommended tightline to the toe of the bluff. Based on the findings, recommendations and limitations of this rePort: · . . . . There has been landslide activity at the subject property in the recent past, however, the recommendatiOns .of this report should provide for minimal landslide hazard to the proposed homesitel _ An analysis of slope stability indicates that the proposed .homesite should not be subject to risk of landslide under normal conditi°ns. The proposal would not increase Surface water discharge or sedimentation to adjacent Properties beyond' predevelopment cOnditions. The proposal would not decrease sloPe stabilitY on adjacent, properties. The proposed home site shOuld be stable under normal rc~.o(~¢~ conditions. ~ DEPT. OF For further information please review the three }amphlets, which are enclosed with the original of this report, published by the Washington State Department of Ecology entitled: "Slope Stabilization and Erosion Control' Using Vegetation", "Surface Water and Groundwater on Coastal Bluffs" and "Vegetation Management: A Guide for Puget Sound Bluff Property Owners". Limitations This report is based on a visual inspection of the existing site conditions. No scientific, measurements, tests or calculations were performed. The findings and report are limited to the normal standard of care of the industry for an investigation without benefit of scientific data and calculations. The sole objective of this investigation has been to diagnose the geotechnical conditions at the site. The report has been prepared for the exclusive use of our client in conjunction with the above mentioned project. It may be used by others only with expressed written permission of the Engineer. The observations, interpretations, and conclusions herein are based on generally accepted professional engineering and geologic principles and practice. This warranty is in lieu of all others, either expressed or implied. Sincerely, NORTHWESTERN TERRITORIES, INC. Robert A Leach, P.E., M~A~ Principal 'Engineer il '~'i,~ ~-"~"-~'~'~-'~--~ ~ 111 ~41RES 12/30/2004 Bill Payton, L.E.G. Engineering Geologist G:\Gen\Bill\Reports\SHEL0301 ,bluff stability.28(26-1 ).Toandos Pen.JCou Expires 11-06-03 APPENDIX IF~!~ JUN 16 2003 · JEFFERSOn,: COUNTY DEPT. OF CC'?,~iJ;*;!}-':' D5VELOF.M.E~T Photo 1. View of bluff from beach looking south. Note slide at right, JEFFERSON COUf4TY Photo 2. View of upland looking north along west property line. , (SE 1,,/~ 29 - 26N - ! I 260.00 T LOT 3O7.22 / / / 4 / / / / °'qi / / / / / N --1 7 JUN .l JEFFERSON COUNTY AREA, WASHINGTON R. lW. -- SHEET NUMBER 66 (Joins sheet SUBJECT PROPERTY SnC (Joins sheet 68) JEFFERSON COUNTY AREA, WASHINGTON 25 ture is about 50°F. The above 32°F growing season ranges from abou{' 150 to 200 days, and the' above 28°F gro;~dng season ranges from about 200 to 240 clays. These soils are associated mainly with Ahl, Grove, 'Lystair, 01ere, and Triton soils. In a representative profile about 3 inches of needles, leaves, bark, and humus cover the surface. The upper 17 inches of the soil is reddish-brown very gravellY sandy loam. Below this, to a depth of 28 inches, is dark yellowish-brown gravelly sandy loam. Beneath this is a very dark gray-ce- mented layer. Glacial cobbles and stones are present on the surface and throughout the soil. Nearly all of the Hoodsport soils are wooded. Besides production of trees, another important use is for rural wood- land homesites. Hoodsport very gravelly sandY loam, 0 to 15 percent slopes (HoC).--This nearly level to rolling soil is on glacial terraces. In most places slopes range from 6 to 12 percent. Representative profile 60 feet west of U.S. Highway 101 and 120 yards south and 120 yards west of SE~,4SW~ corner sec. 29, T. 25 N., R. 2 W.' 01--2~ inches to 1 inch, needles, leaves, wood, and bark. 02--1 inch to 0, black (SYR 2/1) partly decomposed needles, leaves, wood, and bark; strongly acid; abrupt, smooth bound- ary. (~ to 2 inches thick) B21ir--0 to 6 inches, reddish-brown (SYR 4/4) very gravelly sandy loam, reddish brown (SYR 5/4) dry; weak, medium and coame, granular structure; soft, very friable, nonsticky, nonplastie; many roots; 60 percent gravel; strongly acid; gradual, wavy boundary. (4 to 8 inches thick) B22ir--6 to 17 inches, reddish-brown (SYR 4/4) very gravelly sandy loam; reddish brown (SYR 5/4) dry; weak, fine and medium, subangular blocky structure; soft, very friable, non- sticky, nonplastic; many roots; 60 percent gravel; strongly acid; gradual, wavy boundary. (10 to 16 inches thick) C1--17 to 28 inches, dark yellowish-brown (10YI~ 4/4) very gravelly sandy loam, yellowish brown (10YR 5/6) dry; mas- sive; sOft, very friable, nonstieky, nonplastic; many roots; 70 percent gravel; strongly acid; abrupt., smooth boundary. (6 to 12 inches thick) C2sim--28 to 45 inches, dark-gray (SY 4/1) very gravelly sandy loam, gray (5~5/1) dry; massive; extremely hard, extremely firm; strongly cemented; 55 percent gravel; strongly acid; diffuse, smooth boundary. (14 to 20 inches thick) C3--45 inches, very compact, weakly cemented glacial till. (Many feet thick) The B horizons are dark reddish brown to reddish brown. The B and C horizons are 50 to 70 percent gravel and cobbles. The C2sim horizon is gray, dark gray, or olive gray and many feet thick. This soil is medium acid or strongly acid throughout the profile. The soil is moderately well drained. Permeability is moder- ately rapid above thc cemented layer. Roots penetrate to a depth of 20 to 36 inches. This soil holds 2 to 4 inches of water available for plants. Runoff is slow to medium, and the hazard of water erosion is slight to moderate. A perched water table is on top of the cemented laycr during the rainy season. This soil is used mainly for producing trees and for wild- life habitat and recreation areas. Capability unit Vie-l; woodland group 3d2. Hoodsport very gravelly sandy loam, 15 to 30 percent slopes (HoD).--This hilly soil is on glacial terraces. In the higher areas the soil is generally 20 to 24 inches deep to the cemented layer, and in the lower areas it is 24 to 36 inches deep to this layer. Includcd with this soil in mapping are small areas having large basalt, boulders and basalt bedrock outcrops. Runoff is medium, and the hazard of water erosion is moderate. This soil is used mainly for producing trees and for ~41dlife habitat and recreation areas. Capability unit Vie'l; woodland group 3d2. Hoodsport gravelly loam, 0 to 15 percent slopes (I-I~G).--This nearly level to rolling soil is in small, isolated areas on glacial terrace ridgetops. Elevation ranges from 300 to 500 feet. The upper 12 inches or more is dark reddish- brown gravelly loam. Reaction is slightly acid to medium acid. Permeability is moderate above the cemented layer. This soil holds about 3 to 5 inches of water available for plants. This soil is used mainly for production of trees for wildlife habitat and recreation areas. Capability unit IVc-1; woodland group 3d2. Hoodsport-Grove very gravelly sandy loams, 0 to 30 percent slopes (HrD).--This mapping unit consists of about equal proportions of Hoodsport very gravelly sandy loam, 0 to 15 percent slopes, and Grove very gravelly loamy sand, 15 to 30 percent slopes. The Hoodsport soil is mostly undulating to gently rolling, and the Grove soil is mostly hilly. This complex is used mainly for production of trees and for wildlife habitat and recreation areas. Capability unit Vie-l; woodland group 3d2. The Hoypus series consists of somewhat excessively drained, gravelly soils. These soils formed in glacial ou~- wash on terraces. Slopes range from 0 to 50 percent. Eleva- tion ranges from 100 to 500 feel Native vegetation consists mainly of Douglas-fir, western hemlock, western redccdar, madrone, rhododendron, salal, Oregon grape, huckleberry, and bracken. Annual precipitation ranges from 18 to 30 inches. The average annual air temperature is about 50°F. The above 32°F growing season ranges from 200 to 260 days, and the above 28°F growing season ranges from 260 to 300 days. These soils are associated mainly with Agnew, Alderwood, Cassolary, Carlsborg, Clallam, Dick, Everett, Kitsap, and Sinclair soils. In a representative profile in a wooded area, about 3 inches of needles, leaves, txx~gs, and decomposing organic matter cover the surface. The upper 10 inches of the soil is dark-gray and dark-brown gravelly loamy sand. Below tbs, to a depth of 26 inches, is dark yellowish-brown gravelly loamy sand. The underlying material consists of two dark grayish-brown layers. The upper layer, between depths of 26 and 44 inches, is gravelly loamy sand, and the lower layer, between depths of 44 and 60 inches, is very gravelly sand. Most of thc Hoypus soils are wooded. Besides production of trees, other imPortant uses are limited pasture, home gardens, and homesites. Hoypus gravelly loamy sand, 0 to 15 percent slopes (HuC).--This nearly level soil is on rolling glacial moraine terraces. In most places slopes range from 6 to 12 percent. Representative profile on south side of road m SW~NE~NE~ sec. 16, T. 26 N., R. 1 W.' 01--3 inch~ to I inch, needle, leave, bark, and fragmen~ of wood. 02--1 inch to 0, black (5YR 2/1), partly decomposed organic matter from needle, leaves, bark, and fragments of wood; strongly.acid; abrupt, ~avy :ho~dary.. (~ ~o~ 1~ inch~ thick) A2--0 ~6~;!~ i~b~dar~gr~y ~!~Y~' 4/~')'gravelly loamy sand, ~ ~ .... . ~ ~ ~; . ~; ~:, ~ ~.' ~, . gra~. (10Y~6f~y dr weah: fine ~an-la~ structure, soft 26 SOIL very friable, nonsticky, nonplastic; many fine and medium roots; 35 percent gravel; strongly acid; abrupt, wavy bound- ary. (1 to 3 inches thick) B21ir--1~/~ to 10 inches, dark-brown (7.5YR 4/4) gravelly loamy sand, light brown (7.5Y1~ 6/4) dry; reddish-brown (SYI~ 4/4) stains and coatings on surfaces of pebbles; single grained; loose, nonsticky, nonplastic; many fine and medium roots; 45 percent gravel; medium acid; clear, wavy boundary. (8 to 12 inches thick) B22ir--10 to 26 inches, dark yellowish-brown (10YR 4/4) gravelly loamy sand, light yellowish brown (10YR 6/4) dry; single grained; loose, nonsticky, nonplastic; common fine roots; iron and manganese stains on some pebbles; 40 percent gravel; medium acid; clear, wavy boundary. (12 to 18 inches thick) C1--26 to 44 inches, dark grayish-brown (10YI~ 4/2) gravelly loamy sand, light brownish gray (10YP~ 6/2) dry; single grained; loose, nonsticky, nonplastic; few fine roots; 45 percent gravel; medium acid; abrupt, wavy boundary. (10 to 20 inches thick) C2--44 to 60 inches, dark grayish-brown (10YR 4/2) very gravelly sand, light brownish gray (10¥R 6/2) dry; single grained; loose, nonsticky, nonplastic; 60 percent gravel; medium acid. The A2 horizon is dark-gray to dark grayish-brown gravelly loamy sand or sandy loam. The B2 horizons are dark-brown or dark yellowish-brown gravelly loamy sand to gravelly fine sand. They are 35 to 70 percent gravel. The C horizons are dark-gray or dark grayish-brown gravelly loamy sand or very gravelly loamy sand. In places at depths below 40 inches, there are compacted or weakly cemented layers. The B and C horizons are medium acid to slightly acid. Included with this soil in mapping are small areas of somewhat poorly drained heavy silt loam. This soil is somewhat excessively drained. Permeability is rapid. Roots penetrate to a depth of more than 60 inches. This soil holds 2 to 4 inches of water available for plants. Runoff is slow to medium, and the hazard of water erosion is slight to moderate. This soil is used mainly for production of trees, recreation areas, and' rural summer homesites. About 10 to 15 percent of the acreage is used for growing permanent pasture, hay, and home garden crops. Capability unit Vis-l; woodland group 4f2. Hoypus gravelly loamy sand, 15 to 30 percent slopes (]-[uD).--This hilly soil is on glacial outwash terraces where they converge with the steep ravines and drainageways. Included with this soil in mapping are small areas of some- what poorly drained heavy silt loam. Runoff is medium, and the hazard of water erosion is moderate. This soil is used mainly for producing trees and for wildlife habitat and recreation areas. Capability unit Vis-l; woodland group 4f2. i" Hoypus gravelly loamy sand, 30 to 50 percent slopes ([-tuE).--This steep soil is on the sides of ravines and waterways below the terraces. Runoff is medium to rapid, and the hazard of water erosion lis moderate to severe. This soil is used mainly for production of trees and for wildlife habitat and recreation areas. Cap- ability unit Vis-l; woodland group 4f2. · Hoypus gravelly sandy loam, 0 to 15 percent slopes ' ' ([-tvC).--This nearly level to rolling soil is on glacial terraces. The upper 3 to 4 inches of this soil is gravelly fine sandy loam. Below this is 6 to 9 inches of dark-brown gravelly sandy loam. This soil holds 3 to 4 inches of water available for plants. Runoff is slow to medium, and the hazard of water erosion is slight to moderate. This soil is used mainly for production of trees and for '-' wildlife habitat and recreation areas. About 15 to 20 per- cent of the acreage has been cleared and is used for growing SURVEY permanent pasture, hay, an~ Capability unit Vie-l; woo~l~'fl~group 4f2. The Huel series consists of mo~'era?e!~'..we~P;&.6~9~" soils that formed in alluvium Slopes range from 0 to 3 sea level to 300 feet. Native vegetation consists mostly of red alder, Mllow, cottonwood, western hemlock, Sitka spruce, bigleaf maple, annual grasses, and swordfern. Annual pre- cipitation ranges from 120 to 160 inches. The average annual air temperature is about 49°F. The above 32°F growing season ~s about 180 days, and the above 28°F growing season is about 210 days. These soils are associated Mth Hob and Queers soils. In a representative profile in a wooded area, the upper 6 inches of the soil is dark olive-gray loamy fine sand. Beneath this, to a depth of 10 inches, is dark-gray fine sandy loam. The next layer, extending to a depth of 22 inches, is loamy fine sand. Beneath this, to a depth of 30 inches, is very dark gray very gravelly loamy sand. Below this is very gravelly coarse sand that extends to a depth of 60 inches. Huel soils are used mainly for production of trees and for wildlife habitat and recreation areas. Huel loamy fine sand (HW).--This nearly level soil is on low river terraces. The surface is dissected by many small stream channels. In most places slopes range from 0 to 3 percent. Representative profile 100 feet east of Spur Road, 200 yards from queets River Road in NE~SE~NW~ sec. 20, T. 24 N., R. 11 W.: Al--0 to 6 inch,, dark oliv~gray (SY 3/2) loamy fine sand, light gray (SY 7/2) dry; weak, coarse, granular structure; sof~, very friable, nonsticky, nonpl~tic; many fine and medium roots; medium acid; clear, smooth boundary. (5 to 8 inch~ t~ck) C1--6 to 10 inch,, dark-gray (5Y 4/1) fine sandy loam, gray (SY 6/1) dry; weak, thick, platy structure; soft, very friable, nonsticky, nonpl~tic; many fine and medium roots; medium acid; clear, smooth boundary. (3 to 6 inches thick) C2--10 to 22 inch,, dark-gray (5Y 4/1) loamy fine sand, gray (5Y 6/1) dry; m~sive; soft, very friable, nonsticky, non- pl~tic; many fine and medium roots; 6 bands, ~ inch thick, of loamy very fine sand; medium acid; abrupt, smooth bound- ary. (12 to 16 inch~ t~ck) IIC3--22 to 30 inches, very dark gray (5Y 3/1) very gravelly loamy sand, gray (SY 6/1) dry; single grained; loose, nonsticky, nonpl~tic; common fine and medium roots; medium acid; clear, wavy boundary. (8 to 10 inches thick) IIC4--30 to 60 inch,, very dark gray (SY 3/1) very gravelly cosine sand, gray (SY 6/1) dry; single grained; loose, non- s~icky, nonpl~tic; few roots; medium acid. The A1 horizon is dark olive-gray, gray, or very dark grayish- brown loamy fine sand to fine sandy loam and 10 to 20 percent gravel. The C1 and C2 horizons are very dark gray, dark gray, or very dark graykh brown. They have thin layers of fine sandy loam and loamy fine sand that contain gravel in places. The IIC3 and IIC4 horizons have the same color ranges as the C~ and C2 horizons. They are very gravelly and cobbly coarse sand or very gravqlly and cobbly loamy sand with thin layers of finer textures occurring at random. Gravel and cobbl~ make up 60 to 70 percent of the IIC3 and IIC4 horizons. Included with this soil in mapping are small areas of Hob soils and.Queers soils. This soil ks moderately well drained. Permeability is rapid. Roots can penetrate to a depth of more than 60 inches. This soil holds about 3 to 4 inches of water available for plants. Runoff is slow, and the hazard of water erosion is 165' 35' : Qpf ;:~' ~;'..:' :, ... ..- . i,-'7.z.' 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Vol. 11, Jefferson County, July 1978 ~,~///.--...-.- I~,..,, ,, . ,, ,, ..~: ,,. ..... :,~:_.,r:~-. . ,._-. -~.~.,:>~-:,~_ .,.,.,,,..,,_,,,,...,,,:~ · , , ~ ¢ ,,, _ _, .,,,, ,....-. ,, / ' ; ;/ltl .': .'.-...-V.?. ~."~,;" '~"..~ : ~ ~ ~_ ~ ~.. -'~ ',~Ei 't ~., /~ ~ %;:-..~:.\~:Z~.~-S~...~..~ ,?:-:::::~-'~,~ .'-' // i .z -~.¢ , ~ ! .-' /. .: · , , Figure 7 NT/ JLS GROUP, INC. NORTHWESTERN TERRITORIES, INC. A JLS GROUP COMPANY 717 SOUTH PEABODY STREET, PORT ANGELES, WA 98362 Engineers Land Surveyors Geologists Construction Inspection Materials Testing (360) 452-8491 FAX452-8498 www. nti4u.com E-Mail: info@nti4u.com August 11,2003 Patrick and Jennifer Sheldon 5725 Ward Avenue NE Bainbridge Island, WA 98110 JEFFEB$ON C U,N Subject: Addendum to the geotechnical report for the property described as Parcel # 601283014, in Section 28, Township 26 North, Range 1 West, W.M., Jefferson County, WA dated January 23, 2003. - Dear Mr. And Mrs. Sheldon: We recently received a letter from the Jefferson County Department of Community Development dated July 10, 2003 stating that the geotechnical report completed by NTI for the above referenced property "will need further analysis provided for review by the department". Bill Payton of NTI called the Jefferson County Department of COmmunity Development and talked to Kevin Russell about the report and what was needed in order for'the report to be acceptable to the county. From that conversation, it is understood that because of the presence of the recent slide mentioned in the report, the standard 1'1 setback of 75 feet will not be reduced. Also, from that conversation, it is understood that the report will be accepted if the setback is increased to 75 feet. Therefore, we hereby amend the above mentioned report and recommend that the buffer setback distance be established at least 75 feet back from the top of the marine bluff. If you have any questions regarding this matter please do not hesitate to contact this office. NORTHWESTERN TERRiTORiES, INC. Robert A. Leach, P.E., MBA Principal Engineer Sincerely, Bill Payton, L.E.G. Engineering Geologist G:\Gen\Bill\Reports\S H EL0301 .addend um.28(26-1 ).doc i EXPIRES 12J30/2004 Expires 11-06-03