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HomeMy WebLinkAboutLimited Geological Reconnaissance - PLN General - 1/3/2019 &SOIV6 Environmental PLANNINProject No. 18-140 & Geotechnical Inc Meussner Property Geo Recon—Union.WA January 3,2019 Mr.Rod Meussner R EC EO t d�� 7005 218"'Avenue NE V t4 ' ' Redmond,Washington 98053 BAN r 8 Reference: Limited Geological Reconnaissance 8532 Washington State Highway 106 615 W AJder Union,Washington Stregl Dear Mr. Meussner: Resolve Environmental and Geotechnical, Incorporated (Resolve) is pleased to provide this letter report for the limited site reconnaissance at the above-referenced property. Resolve understands that the object of the investigation was to perform a limited visual inspection of the site and geologic conditions wherein proposed future construction of a stairway will be undertaken. The subject site is located along Washington State Highway 106, Union, Mason County, Washington. The latitude is approximately 47 degrees, 20 minutes, 57.9 seconds north, and -123 degrees, 02 minutes, 20.0 seconds west. The elevation is landward of the ordinary mean high water . The site is surrounded by rural residential properties to the west, east and south, with Hood Canal to the north. State Highway 106 is directly adjacent, and to the south of, the proposed construction site. A site Vicinity Map is attached to this report. A Washington State Licensed Geologist from Resolve(Ronald P.Nance,P.G.)performed the limited site reconnaissance on December 15th, 2018. Our observations were preceded by a review of local geologic databases, local geology,and area slope evaluations of the immediate vicinity. Proposed Development It is our understanding that the property owner is proposing construction of a stairway on the site. The stairway will extend from very near the crest of slope adjacent to the highway,to the beach below. --Geologic Setting The subject site lies within the central Puget Lowland. The lowland is part of a regional north-south trending trough that extends from southwestern British Columbia to near Eugene, Oregon. North of Olympia, Washington,this lowland is glacially carved with a depositional and erosional history including at least four separate glacial advances and retreats. 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 non- glacial sediments consisting of interbedded gravel,sand,silt,clay,till,and peat lenses. --Site Review Summary The subject property soil and slope conditions were visually examined and evaluated in a field reconnaissance on December 15, 2018. At the time of the site visit there was no visual evidence of imminent slope movement or instability. No seepages were found on the site slopes. There was no indication of depth to groundwater on the site. If proper erosion/drainage controls are instituted where required, the proposed stairway construction appears unlikely to be affected by slope conditions, and construction on the site is not considered likely to affect slope stability. A `Geological Reconnaissance Report' is presented here, and based on observations, the geologic hazards mapped for the subject site appear to be cautionary, with minimal hazards actually noted on the subject property. &solve Environmental Project No. 18-140 & Geotechnical Inc Meussner Property Geo Recon—Union,WA Soil and Slope Research The following information provided a basis for a general understanding of the subject soils and geologic conditions: --Mason County: • Per Mason County Code 8.53.030, the site has associated Critical Areas, including slope and shoreline proximity. Although the slopes are within 300 feet of slope and the bank of the stairway is greater than 15%,the shoreline and slopes are not considered likely to be affected by stairway construction. • Landslide Hazards erosion are mapped for the site, although no historic sliding or erosion channels/rill were observed in the area of construction on the subject site. • Seismic hazards do not appear to be significant issues on the subject parcel. No faults, folds, or other indications of seismic activity were noted on the site. • Based on the soil types listed by the USDA for the subject site, the liquefaction hazard for the area,including the subject site,appears minimal. • Washington State Department of Ecology (DOE) Coastal Atlas maps do not indicate flood or other extreme hazard zones for the subject site. The map shows ratings of 0.5 K Factor and a Soil Erosion Factor of 3. --USDA Soils The United States Department of Agriculture (USDA) Soil Survey of Kitsap County Area, Washington, information indicates the following soil type exists on the project site: • Everett very gravelly sandy loam(8 to 15 percent slopes);and, • Alderwood gravelly sandy loam(30 to 80 percent slopes) A soils map and the soil survey descriptions of these soil types are attached to this report. The soils actually observed in the immediate vicinity of the project indicated that the soils listed by the USDA soil map profile were apparently accurate. In the eastern areas, probing the soils with a %2-inch aluminum alloy T-Probe showed six to eight inches of penetration into the existing topsoil, fill, and debris. These loose soils appeared to be above the very dense Everett Complex soils. This included the proposed construction site and lower portions of the slope along the beach area. In the accessible portions of the site, soils in the shallow subsurface at the site, beneath the topsoil, were described in the field as brown, damp to moist, silty sand with gravel (USCS SM). These were observed in minor denuded areas along the bank. Below two to three feet, soils appeared to be very dense and relatively impermeable. Although soils in the near surface appeared moisture-sensitive, the relatively low height of the subject bank and previously-developed bulkheads and rock terrace walls in the immediate vicinity of the site would tend to preclude any heavy erosion, sliding or slumping. Various slopes were measured by Brunton during our investigation. Slopes were estimated to be between 60 and 70 percent, with the exception of the immediate drop-off from the highway to the proposed top of stairway. Those soils that were observed on the subject slopes of the site appeared stable. The slopes on the site showed no signs of past, historical sliding or creep. No sediment piles or overgrown lobate structures indicating sliding were seen near the base of the slope or into the Hood Canal. No major sediment piles or denuded slopes suggesting recent sliding or slumping were observed on the site or in the immediate vicinity. Local sheetflow and stormwater would naturally flow down-slope, mostly to the east, down dip towards the Hood Canal. Much of the water would likely be infiltrated into the soils and taken up by vegetation. No weather-driven erosion channels or incised drainage pathways were observed on the subject site. It is Solve Environmental Project No. 18-140 & Geotechnical Inc Meussner Property Geo Recon—Union,WA possible that there is an existing drainage system from the slopes above the subject stairway site,although none was observed.Pipes may be observable at medium or low tides. No major cracks or lineations suggesting large-scale geologic problems were observed on any portions of the property or in the vicinity. No major, areal geologic issues were noted in the sloping portions of the property,or in observable areas of adjacent property. --Geologic Setting The subject site lies within the central Puget Lowland. The lowland is part of a regional north-south trending trough that extends from southwestern British Columbia to near Eugene, Oregon. North of Olympia, Washington,this lowland is glacially carved with a depositional and erosional history including at least four separate glacial advances and retreats. 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 non- glacial sediments consisting of interbedded gravel,sand,silt,clay,till,and peat lenses. —Site Review Summary The subject property soil and slope conditions were visually examined and evaluated in a field reconnaissance on December 15, 2018. At the time of the site visit there was no visual evidence of imminent slope movement or instability. No seepages were found on the site slopes. There was no indication of depth to groundwater on the site. No sinkholes, depressions, or other signs or geological instability were observed. If proper erosion/drainage controls are instituted,and appropriately-supported posts are emplaced on the site where required, the proposed construction appears unlikely to be affected by slope conditions, and construction on the site is not considered likely to affect slope stability. A `geological report' is presented here, and based on observations, the geologic hazards mapped for the subject site appear to be cautionary, with minimal hazards actually noted on the subject property. Conclusions and Recommendations It is noted that most of the slopes in the Puget Sound region will almost certainly experience some retreat, as natural weathering, erosion, and seismic activity are inherent in the environment. The weathering of the faces of the relatively steep slopes at the subject site is to be expected over time. Sliding and slumping is somewhat mitigated by some vegetative cover of grass, salal, and shrubberies. At no time should slope faces be left intentionally denuded for extended periods of time, particularly during wet weather conditions. Also, slopes should not be loaded with yard waste,tree trimmings, or other debris. It is considered a possibility that some retreat of the slope will occur during the expected lifetime of the proposed stairs,and occasional sliding(particularly during storms and wet weather)is a possibility. It is therefore recommended that posts/supports for the proposed stairway be set well through surface materials (and any beach sands and rocks that may be encountered) and into dense to very dense soils below. It is our opinion that posts or supports should be set well into soils with an assumed N value greater than 20 (medium dense to dense soils). Probing with an aluminum alloy T-Probe indicates that competent, dense to very dense soils were, in some places, six inches to eight inches below the surficial soils. Other portions of the bank showed very dense materials with less than two inches of probe penetration. Provided the supports are set into competent soils, and the inherent risks of slope construction are understood by the client and stairway contractor, Resolve did not observe any geologic conditions that preclude construction of the stairway. Resolve did not observe any conditions wherein stairway construction would impact the subject slope stability. A periodic re-evaluation of bank, slope, drainage, and groundwater conditions should be conducted as a matter of due diligence along the bank slopes and over the subject site in general. Solve Environmental Project No. 18-140 & Geotechnical Inc Meussner Property Geo Recon Union,WA As mentioned,no perched groundwater appeared to be emanating from the sands along the bank,however extra care should be taken during construction should groundwater be encountered. No preferred drainage pathways appear to have been established on the slope/bank face. Best Management Practices regarding erosion control inherent in projects such as proposed for the stairway should be adhered to as construction proceeds. Any existing subsurface elements of any previous structures on the bank will have to be removed for new construction. As with all construction projects in the region, standard erosion control BMP's should be employed. It is our opinion that this geological reconnaissance report satisfies the intent of the requirements for the Mason County Critical Areas codes for geologically hazardous areas. It is Resolve's opinion that due diligence was employed in this reconnaissance-level investigation. Limitations Our conclusions are based on the information obtained from available databases, limited field observation of the subject site, and on our interpretation of the visible surface conditions only. No subsurface evaluation or geotechnical engineering report was conducted per the client-requested scope of work. We make no other warranty, either expressed or implied. If conditions are encountered that appear to be different than those described in this report, we should be notified so that we may review and verify or modify our recommendations. Resolve appreciates the opportunity to provide these services, and hopes the information presented in this report provides for your needs and requirements. Please feel free to call with any comments or questions regarding this letter report. Our telephone number is(360)865-1843. Sincerely, Resolve Environmental &Geotechnical, Inc. Ronald P.Nance,P.G. Senior Geologist and Environmental Professional WA License No.2533 Meussner Property Vicnity Map "tJrnori i . WA1 %1� �. .�,..z SkokomIsh } i - $ j • -�►,� ;. , 44 it Google Earth a n PROJECT:FIGURE 1 EnvironmentalResolve - &Geotechnical, Inc. Limited . . 8532 State Highway • . (360)865-1843 -• • � • Union, Washington Prepared for: Mr. Rod Meussner • Solve Environmental & Geotechnical Inc USDA INFORMATION 3 Soil Map—Mason County,Washington (Meussner Property Soils Map) 4%780 496870 49M 49M 497140 497230 49732D 497410 497500 497590 ^0 47°21'3"N A• L"711 — 7 I N ry 4 47°20'457N 47°20'4S N 49M 4MM 49MM 497050 497140 497230 497320 497410 497590 • 3 3 Nap scale:1:4,010 If prtftd on A landscape(11"x B.5")sheet " Meters N � 0 50 100 zoo Soo Feet 0 150 30o so0 soo Map projeCbM:Web Merotor Comer Wordirlates:WGS84 Edge tars:IJfM Zone 1ON WGS84 USDA Natural Resources Web Soil Survey 1 2/1 312 0 1 8 �� Conservation Service National Cooperative Soil Survey Page 1 of 3 Sod Map—Mason County,Washington (Meussner Property Soils Map) MAP LEGEND MAP INFORMATION Area of Interest(AOi) Spoil Area The soid euveys that comprise your AOI were mapped at 0 Area of Interest(AOI) Stony Spot 1:31.700. 4j Soils Very stony Spot Warning:Soil Map may not be valid at this scale. `-� Soil Map Unit Polygons Wet stol Enlargement of maps beyond the scale of mapping can cause ,.�. Soil Map Unit Lines misunderstanding of the detail of mapping and accuracy of soil ,.� Other line placement.The maps do not show the small areas of Soil Map unit Points contrasting soils that could have been shown at a more detailed Special Line Features i Seale Special Point Features i o Blowout Water Features V Streams and Canals Please rely on the bar scale on each map sheet for map Boo,Pit measurements. Transportation +� Clay Spot Rails Source of Map: Natural Resources Conservation Service Web Soil Survey URL: i^ Closed Depression N Interstate Highways Coordinate System: Web Mercator(EPSG3857) Gravel Pit US Routes Maps from the Web Soil Survey are based on the Web Mercator Gravelly Spot Major Roads projection,which preserves direction and shape but distorts distance and area.A projection that preserves area,such as the Landfill Loral Roads Albers equal-area conic projection,should be used if more accurate calculations of distance or area are required Lava Flow _ lit.. Background Marsh or swamp Aerial Photography This product is generated from the USDA-NRCS certified data as of the version date(s)listed below. i Mine or Quarry Soil Survey Area: Mason County,Washington Miscellaneous Water Survey Area Data: Version 14,Sep 10,2018 0 Perennial Water Soil map units are labeled(as space allows)for map scales 1,50,000 or larger. Rock Outcrop Dale(s)aerial images were photographed: Apr 1,201 G—Sep 27, + Seine Spot 2016 Sandy Spot The orthophoto or other base map on which the soil lines were ,%t. Severely Eroded Spot compiled and digitized probably differs from the background imagery displayed on these maps.As a result,some minor Sinkhole shifting of map unit boundaries may be evident. 7y Slide or Slip Sortie Spot USDA Natural Resources Web Soil Survey 1 211 3/2 01 8 T Conservation Service National Cooperative Soil Survey Page 2 of 3 Soil Map—Mason County,Washington Meussner Property Soils Map Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI Ad Alderwood gravelly sandy 55.1 94.7% loam,30 to 50 percent slopes Eh Everett very gravelly sandy 0.4 0.7% loam,8 to 15 percent slopes Totals for Area of Interest _ 58.2 100.0% USDA Natural Resources Web Soil Survey 12/13/2018 �� Conservation Service National Cooperative Soil Survey Page 3 of 3 Map Unit Description:Everett very gravelly sandy loam,8 to 15 percent slopes---Mason Meussner Property Soils Description County,Washington Mason County, Washingt on Eh—Everett very gravelly sandy loam, 8 to 15 percent slopes Map Unit Setting National map unit symbol: 2t62b Elevation: 30 to 900 feet Mean annual precipitation: 35 to 91 inches Mean annual air temperature: 48 to 52 degrees F Frost-free period: 180 to 240 days Farmland classification: Farmland of statewide importance Map Unit Composition Everett and similar soils: 80 percent Minor components: 20 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Everett Setting Landform. Kames,eskers, moraines Landform position(two-dimensional): Shoulder,footslope Landform position (three-dimensional): Crest, base slope Down-slope shape: Convex Across-slope shape: Convex Parent material: Sandy and gravelly glacial outwash Typical profile Oi-0 to 1 inches: slightly decomposed plant material A- 1 to 3 inches: very gravelly sandy loam Bw-3 to 24 inches: very gravelly sandy loam C1 -24 to 35 inches: very gravelly loamy sand C2-35 to 60 inches: extremely cobbly coarse sand Properties and qualities Slope: 8 to 15 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Somewhat excessively drained Capacity of the most limiting layer to transmit water(Ksat): High (1.98 to 5.95 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None q Y Frequency of ponding. None Available water storage in profile: Low(about 3.2 inches) Interpretive groups Land capability classification(irrigated): None specified Land capability classification(nonirrigated): 4s Hydrologic Soil Group: A USDA Natural Resources Web Soil Survey 12/13/2018 Conservation Service National Cooperative Soil Survey Page 1 of 2 Map Unit Description:Everett very gravelly sandy loam,8 to 15 percent slopes--Mason Meussner Property Soils Description County,Washington Forage suitability group: Droughty Soils(G002XS401 WA), Droughty Soils(G002XF403WA), Droughty Soils (G002XN402WA) Hydric soil rating: No Minor Components Alderwood Percent of map unit: 10 percent Landform: Ridges,hills Landform position (two-dimensional): Shoulder Landform position (three-dimensional): Nose slope,talf Down-slope shape: Linear, convex Across-slope shape: Convex Hydric soil rating: No Indianola Percent of map unit: 10 percent Landform: Eskers, kames,terraces Landform position (three-dimensional): Riser Down-slope shape: Linear Across-slope shape: Linear Hydric soil rating: No Data Source Information Soil Survey Area: Mason County,Washington Survey Area Data: Version 14, Sep 10,2018 USDA Natural Resources Web Soil Survey 12/13/2018 Conservation Service National Cooperative Soil Survey Page 2 of 2 Map Unit Description:Alderwood gravelly sandy loam,30 to 50 percent slopes—Mason Meussner Property Soils Description County,Washington Mason County, Washington Ad—Alderwood gravelly sandy loam, 30 to 50 percent slopes Map Unit Setting National map unit symbol: 2t628 Elevation: 50 to 800 feet Mean annual precipitation: 25 to 60 inches Mean annual air temperature: 46 to 52 degrees F Frost-free period: 160 to 240 days Farmland classification: Not prime farmland Map Unit Composition Alderwood and similar soils: 80 percent Minor components: 20 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Alderwood Setting Landform: Ridges, hills Landform position (two-dimensional): Backslope Landform position (three-dimensional): Side slope, nose slope,talf Down-slope shape: Linear, convex Across-slope shape: Convex Parent material: Glacial drift and/or glacial outwash over dense glaciomarine deposits Typical profile A-0 to 7 inches: gravelly sandy loam Bw1 - 7 to 21 inches: very gravelly sandy loam Bw2-21 to 30 inches: very gravelly sandy loam Bg-30 to 35 inches: very gravelly sandy loam 2Cd1 -35 to 43 inches: very gravelly sandy loam 2Cd2-43 to 59 inches: very gravelly sandy loam Properties and qualities Slope: 30 to 50 percent Depth to restrictive feature: 20 to 39 inches to densic material Natural drainage class: Moderately well drained Capacity of the most limiting layer to transmit water(Ksat): Very low to moderately low(0.00 to 0.06 in/hr) Depth to water table: About 18 to 37 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: Very low(about 2.7 inches) Interpretive groups Land capability classification(irrigated): None specified Land capability classification (nonirrigated): 7e Hydrologic Soil Group: B USDA Natural Resources Web Soil Survey 12/13/2018 Conservation Service National Cooperative Soil Survey Page 1 of 2 Map Unit Description:Alderwood gravelly sandy loam,30 to 50 percent slopes--Mason Meussner Property Soils Description County,Washington Hydric soil rating: No Minor Components Everett Percent of map unit: 10 percent Landform: Kames,eskers, moraines Landform position (two-dimensional): Backslope Landform position(three-dimensional): Side slope Down-slope shape: Convex Across-slope shape: Convex Hydric soil rating: No Indianola Percent of map unit: 5 percent Landform: Eskers, kames, terraces Landform position (three-dimensional): Tread Down-slope shape: Linear Across-slope shape: Linear Hydric soil rating: No Shalcar Percent of map unit: 3 percent Landform: Depressions Landform position (three-dimensional): Dip Down-slope shape: Concave Across-slope shape: Concave Hydric soil rating: Yes Norma Percent of map unit. 2 percent Landform: Depressions,drainageways Landform positron (three-dimensional): Dip Down-slope shape: Concave, linear Across-slope shape: Concave Hydric soil rating: Yes Data Source Information Soil Survey Area: Mason County, Washington Survey Area Data: Version 14, Sep 10,2018 USDA Natural Resources Web Soil Survey 1 2/1 31201 8 �� Conservation Service National Cooperative Soil Survey Page 2 of 2