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Home My WebLink AboutGEO2018-00073 - GEO Geological Review - 12/20/2018 Coo 2b �8 -0�0�3 GEORESOURCES earth science & geotechr:ical engineering 5007 Pacific Hwy E., Suite 16 Fife, WA 98424 253.896.1011 www.georesources.rocks Se tember 28, 2018 Port of Grapeview c/o Soundview Consultants 2907 Harborview Drive, Suite D Gig Harbor, Washington 98335 Attn: Ms.Ann Boeholt, PWS (253)514-8953 ext 020 ann@soundviewconsultants.com ngineering gy Report oposed Shoreline Restoration Jx ,,,4.peview Loop Road Mason County, Washington PN: 121055163003 'Doc ID: PortofGrapeview.GrapeviewLoop.RG INTRODUCTION This geotechnical eri' r,port summarizes our site observations, our geotechnical data review and engineering nalys and provides geotechnical recommendations for the proposed shoreline restoration to cate at xxx-Grapeview Loop Road near the Port of Grapeview in Mason runderstand Washi as n on the Site Location Map, Figure 1. Our u er di the project is based on our correspondence with Ann Boeholt of iew Co ultan ur September 20, 2018 site visit, and our experience in the site area. We tha e P rt of Grapeview is planning to install a new floating dock to provide short term e to users existing public boat ramp located at Grapeview Loop Road and that the Army f Engines is requiring mitigation for potential aquatic impacts. We further understand that the Port of Gra*view proposes to purchase an adjacent parcel that has a creosote timber pile ulkhead that ` dysfunctional, and proposes to remove the old timber pile and wood lagging khead an place it with large woody debris soft armoring. SCOPE The purpose of our services was to evaluate the surface and subsurface conditions at the site as a basis for assessing potential impacts to and from the wave and tidal erosion on the shoreline portion of the parcel. Specifically,our scope of services for the project included the following: 1. Conducting a geologic reconnaissance of the site area; 2. Observing subsurface conditions at the site by logging the soils exposed along the beach; 3. Describing surface and subsurface conditions, including soil type; 4. Providing conclusions and recommendations regarding the type of bulkhead and alternative materials; PortofGrapeview.G rap eviewLoop Rd.RG September 28,2018 Page 1 2 5. Preparing this written Geotechnical Engineering Report summarizing our site observations and conclusions, and our geotechnical recommendations and design criteria, along with the supporting data. The above scope of work was summarized in our Proposal for Geo technical Engineering Services dated September 18, 2018. We received your written authorization to proceed on September 19, 2018. SITE CONDITIONS Surface Conditions The subject mitigation site is located at xxx Grapeview Loop Road, two lots north of the Port of Grapeview boat ramp and marina in Mason County, Washington. According to the Mason County WA GIS website,the parcel is roughly flag-pole in shape. The"flag'portion is approximately 60 feet wide (north to south) by about 218 to 236 feet deep(east to west). The"pole"section of the parcel measures about 20 feet wide by about 74 to 82 feet deep. The entire site area encompasses approximately 0.31 acres. The site is currently undeveloped except for the failing creosote timber bulkhead. The site is bounded by the residence located at 5054 E Grapeview Loop Road to the south, by Grapeview Loop Drive to the west,the residence at 5100 E Grapeview Loop Road to the north,and by the Puget Sound to the east. From Grapeview Loop Road, the site slopes down from the northwest to the southeast at about 10 percent or less. The shoreline portion of the site is generally vertical and about 4 feet tall. Total topographic relief across the site is on the order of 15 feet. The current site configuration is shown on the Site Vicinity Map, Figure 2. Vegetation in the upland portion of the site consists of grasses and scattered deciduous trees in the west portion of the site. No seeps were observed on the slopes at the time of our site visit. As stated, the old timber pile/wood lagging bulkhead that extended along the shoreline portion of the site is failing and tidal scour is occurring behind the old bulkhead. Scour has extended back as far as 9 to 10 feet from the face of the old bulkhead. No other evidence of upland erosion, landslide activity or deep-seated slope instability was observed at the site at the time of our site visit. The adjacent parcels to the north and south are protected by concrete cast-in-place bulkheads. Site Soils The USDA Natural Resource Conservation Service (NRCS) Web Soil Survey maps the soils in the area of the site as Alderwood gravelly sandy loam(Ab)soils. The Alderwood soils are derived from glacial drift or glacial outwash over dense glaciomarine deposits and form on slopes of 8 to 15 percent. These soils have a"moderate to severe"erosion hazard when exposed,and are included in hydrologic soils group B. A copy of the SCS map for the site vicinity is attached as Figure 3. Site Geology The Geologic Map of the Vaughn 7.5-minute Quadrangle, Pierce and Mason Counties, Washington (Logan et Al., 2007) indicates the site is underlain by Vashon glacial till (Qgt) deposits. The glacial till soils were deposited during the most recent Vashon Stade of the Fraser Glaciation some 12,000 to 15,000 years ago. The glacial till consists of a heterogeneous mixture of gravel,sand,silt and clay that was deposited at the base of the continental ice mass, and was subsequently over-ridden. As such, GEORESOURCE PortofG rap eview.G rap eviewLoop Rd.RG September 28,2018 page 1 3 the glacial till is considered to be over consolidated and generally exhibits high strength and low compressibility characteristics where undisturbed. The near surface soils at the site have been disturbed by natural weathering processes that have occurred since their deposition. An excerpt of the above referenced map is included as Figure 4. The Washington State Department of Ecology (DOE) Coastal Atlas maps the site as being "stable". We also reviewed a series of oblique aerial photos from 1992 to 2016 which show minor erosion along the shoreline from 2000 to 2016. The Coastal Zone Atlas also shows the drift cell current as undefined in the site area. A copy of the Coastal Zone Atlas is attached as Figure 5,while copies of the aerial photographs are attached as Figures 6a through 6d. Subsurface Conditions We were able to observe subsurface conditions at the site by logging the bare soils along the shoreline. We observed about 6 inches of sod and topsoil mantling about 18 to 24 inches of light orange- brown silty sand with gravel that appeared to be medium dense and moist. These soils appeared to be consistent with weathered glacial till soils. Underlying the surficial soils, we observed grey/tan with orange mottling silty sand with gravel that appeared dense and moist. These soils appear to be consistent with glacial till deposits.The glacial till extended down to the beach sand and gravel. ENGINEERING CONCLUSIONS AND RECOMMENDATIONS Based on our site evaluation, it is our opinion that an active shoreline erosion hazard does exist at the site. The combination of shoreline tidal and wave action is resulting in active toe erosion, sloughing and shoreline regression. We recommend that new soft armoring be installed to prevent additional erosion at the site. The new soft armor bulkhead will be constructed at the toe of the active shoreline area, landward of old timber pile bulkhead, Mean High Water (MHW) and Ordinary High Water(OHW)and tie into the adjacent concrete cast-in-place bulkheads. Bulkhead Materials We understand that the selected material for replacement bulkhead is large woody debris with scattered large rocks used to hold the ends of the woody debris in place. There are a variety of alternative materials that may be considered for the construction of shoreline bulkheads. Virtually all shoreline protection construction methods and materials require beach access and/or beach disturbance. In general, the shoreline protective materials can be divided into three basic types, including the following: cast-in-place construction materials (concrete), placed materials(rock, blocks and timber), and "soft armor" materials(anchored large woody debris). Based on our experience, although poured in-place concrete bulkheads provide excellent protection of the shoreline from erosion, they are not a preferred alternative by regulatory staff because of water quality issues during construction and redirection or reflection of shoreline energy often resulting in scour on the adjacent properties. Large rock, block or treated timber materials are common bulkhead materials in the Puget Sound area. Treated timber materials provide adequate protection of the toe, but are not considered permanent, as illustrated by the number of timber bulkheads that are replaced on a regular basis owing to damage, rot or decay.The treated timber materials are also considered to have water quality issues by some agency staff,depending on the treatment(creosote). Because the permitted structure GEORESOURCES PortofGrapeview.G rap eviewLoop Rd.RG September 28,2018 page 1 4 would not be at risk of failure within 3 years, the state agencies would not support the use of hard armoring. We understand that you propose to use soft armoring to mitigate the toe erosion along the shoreline. Although technically not a bulkhead, anchored large wood placed at or near the toe of the shoreline bank and beach area can provide limited erosion protection for the toe of the shoreline. The large wood does have a limited life expectancy and requires maintenance and possibly occasional replacement, but should adequately mitigate toe erosion at the site. It is our opinion that the use of soft armoring will reduce the rate of shoreline regression and will provide opportunity for biologic activity and variation of the energy dissipation patterns along the shoreline. The shoreline across the front of the site faces east towards Reach Island and has a fetch of less than 1,000 feet to the east, and 1,250 to 1,400 feet to the southeast and northeast respectively. The fetch to the southeast is interrupted by the exiting Port of Grapeview Marina. The predominant winter storm direction results in severe, damaging winds from the south and southwest, which the site is not subject too. Also, the Washington State Department of Ecology Coastal Atlas indicates that the site does not have "any appreciable drift". Given the short fetch, east facing direction of the shoreline, and little to no drift current along the shoreline, the use of soft armoring does appear feasible from a geotechnical standpoint. The anchored large woody debris should abut the adjacent cast-in-place concrete bulkheads so as to not result in scour eddies or sediment traps. The logs should be installed along the new "active" shoreline behind the failing bulkhead. The irregular shape of the logs, and the voids associated with the soft armoring,will absorb most of the wave energy(tidal and boat traffic)thereby reducing the potential for erosion to the site and adjacent properties. The large wood should be anchored by using cable or chains attached to buried deadman anchors(ecology blocks)or to helical or manta ray type anchors. We do recommend using occasional placement of individual rocks near the end of each log in order to hold the logs in place. A typical detail for a soft armor bulkhead is attached as Figures 7a and 7b. It is our opinion that large woody debris and placement rock, if properly installed, should mitigate against the active erosion. While the soft armoring will be an effective method of addressing the active and ongoing erosion,this system will not fully eliminate or stop tidal and wave energy from impacting the site. LIMITATIONS We have prepared this report for use by Port of Grapeview, Soundview Consultants, and other members of the design and construction team, for use in the design of a portion of this project. The data used in preparing this report and this report should be provided to prospective contractors for their bidding or estimating purposes only. Our report, conclusions and interpretations are based on data from others and limited site reconnaissance, and should not be construed as a warranty of the subsurface conditions. Variations in subsurface conditions across the site are possible and may also occur with time. A contingency for unanticipated conditions should be included in the budget and schedule. Sufficient monitoring,testing and consultation should be provided by our firm during construction to confirm that the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes should the conditions revealed during the work differ from those GEORESOURCES PortofGrapeview.GrapeviewLoopRd.RGu September 28,2018 page 1 5 anticipated, and to evaluate whether earthwork and foundation installation activities comply with contract plans and specifications. The scope of our services does not include services related to environmental remediation and construction safety precautions. Our recommendations are not intended to direct the contractor's methods, techniques, sequences or procedures, except as specifically described in our report for consideration in design. Within the limitations of scope, schedule and budget, our services have been executed in accordance with generally accepted practices in this area at the time this report was prepared. No other conditions, express or implied,should be understood. We have appreciated the opportunity to be of service to you on this project. If you have any questions or comments, please do not hesitate to call at your earliest convenience. Respectfully submitted, GeoResources, LLC Jordan Kovash, GIT Staff Geologist in Training e°{ Wash�� Engineering Geologist ` �� 3�72�rp 5~ �iC 925 �5 ceased Ge°\° . ��sed Ge°�°121��tY Seth Mattos KEITH SCOTT SCHEMBS Seth T. Mattos, LG Keith S. Schembs, LEG Associates Principal J LK:STM:KSS/j Ik,kss Doc ID:PortofGrapeview.GrapeviewLoopRd.RG Attachments: Figure 1:Site Location Map Figure 2:Site Vicinity Figure 3:NRCS Soils Map Figure 4:Geology Map Figure 5:Coastal Zone Atlas Figures 6a-6d:Oblique Aerial Photos Figure 7a:Soft Shore Stabilization Site Plan Figure 7b:Soft Shore Stabilization Detail Figures 8a-8c:Site Photographs GEORESOURCES Ni►3oz- f 1 t - i 1 t t 1 I I Grapeview s � le J� a41 ♦ j E8 , r t Approximate Site Location Map created from Mason County Public GIS (https://gis.co.mason.wa.us/mason/) Ir +(F S Not to Scale Site Location Map Proposed Soft Armor and Shoreline Mitigation xxx Loop RoadGEORESOURCES Mason County, Washington earth science & geotechnical engineering PN: 1 21 0551 63003 5007 Pacific Hwy E.,Suite 16 1 Fife,WA 98424 1253.896.1011 1 www.8eoresources.rocks Doc ID:PortofGrapeview.GrapeviewLoopRd.F September 2018 Figure 1 l N r t. , ak AL x a' •101111 i . t{ 1 Approximate Site Location Map created from Mason County Public GIS(https://gis.co.mason.wa.us/mason/) cn S Not to Scale Site Vicinity Map Proposed Soft Armor and Shoreline Mitigation xxx Grapeview Loop Road GEORESOURCES � Mason County, Washington PN: 121055163003 earth science & geotechnical engineering 5007 Pacific Hwy E.,Suite 16 1 Fife,WA 98424 1 253.696.1011 I www.6eoresources.rocks Doc ID:PortofGrapeview.GrapeviewLoopRd.F September 2018 Figure 2 % _J f 4 �y s� y f E �fi Approximate iite Location Map created from Web Soil Survey(http://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx) Soil Soil Name Parent Material Slopes Erosion Hydrologic Type Hazard Soils Group Ab Alderwood gravelly Glacial drift and/or glacial outwash over dense g to 15 Moderate B sandy loam glaciomarine deposits to Severe Bellingham silty None to Be clay loam Alluvium. Lacustrine deposits and loess 0 to 3 slight C/D IW+IE 5 Not to Scale NRCS Soils Map ►— Proposed Soft Armor and Shoreline Mitigation xxx Grapeview Loop Road GEORESOURCES Mason County, Washington PN: 121055163003 earth science & geotechnical engineering 5007 Pacific Hwy E.,Suite 16 1 Fife,WA 98424 1253.996.1011 1 www.georesources.rocks Doc ID:PortofGrapeview.GrapeviewLoopRd.F September 2018 Figure 3 f f o i Soo .All a •• 2. 1 d 1 a• r Approximate Site Location An excerpt from Geologic Map of the Vaughn 7.5-minute Quadrangle, Pierce and Mason Counties, Washington by Robert L., Logan,and Timothy J.Walsh December 2007. Qgt Vashon till <k S Not to Scale USGS Geologic Map Proposed Soft Armor and Shoreline Mitigation xxx Grapeview Loop Road GEORESOURCES 'I Mason County, Washington PN: 121055163003 earth science & geotechnical engineering 5007 Pacific Hwy E.,Suite 16 1 Fife,WA98424 1253.896.1011 I www.georesources.racks Doc ID.PortofGrapeview.GrapeviewLoopRd.F September 2018 Figure 4 e Opp Case Inlet Approximate Site Location Map created from Washington State Coastal Atlas(https://fortress.wa.gov/ecy/coastalatlas/tools/Map.aspx) Slope stability A Drift cells g Stable %1 Divergence zone Intermediate .—.+► Left to right Modified %�- No appreciable drift Unstable "►Right to left y Unstable(old slide) .-4- Undefined Unstable (recent slide) 1� 5 Not to Scale Coastal Zone Atlas Proposed Soft Armor and Shoreline Mitigation GEORESOURCES xxx Grapeview Loop Road Mason County, Washington earth science & geotechnical engineering PN: 121055163003 5007 Pacific Hwy E.,SuIte 16 I Fife,WA 90424 1253.896.1011 I www.`eoresources.rocks Doc ID:PortofGrapeview.GrapeviewLoopRd.F September 2018 Figure 5 4 a r - 1 r ,_ v { Approximate Site Location Photo obtained from Washington State Coastal Atlas (https://fortress.wa.gov/ecy/coastalatlas/tools/Map.aspx) 1� 5 Not to Scale Oblique Aerial Shoreline Photograph - 2016 Proposed Soft Armor and Shoreline Mitigation GEORESOURCES xxx Grapeview Loop Road Mason County, Washington earth science & geotechnical engineering PN: 1 21 0551 63003 5007 Pacific Hwy E.,Suite 16 I Fife,WA 98424 1253.816.1011 I www.8eoresources.rocks Doc ID:PortofGrapeview.GrapeviewLoopRd.F September 2018 Figure 6a 11. 1: F � F, ti . r. a i F r{ l 9 ' to C n i F. t Sf ; 4 y � _ 1 Approximate Site Location Photo obtained from Washington State Coastal Atlas (https://fortress.wa.gov/ecy/coastalatlas/tools/Map.aspx) S Not to Scale Oblique Aerial Shoreline Photograph - 2006 Proposed Soft Armor and Shoreline Mitigation GEORESOURCES xxx Grapeview Loop Road Mason County, Washington earth science & geotechnical engineering PN: 121055163003 5007 Pacific Hwy E.,SuIte 16 I FIfe,WA 99424 1253.896.1011 i www.jeoresources.rocks Doc ID:PortofGrapeview.GrapeviewLoopRd.F September 2018 TFigure 6b 4W- -- R ..-ram a• A:. Approximate Site Location Photo obtained from Washington State Coastal Atlas (https://fortress.wa.gov/ecy/coastalatlas/tools/Map.aspx) tX 5 Not to Scale Oblique Aerial Shoreline Photograph - 2000 Proposed Soft Armor and Shoreline Mitigation GEORESOURCES xxx Grapeview Loop Road Mason County, Washington earth science & geotechnical engineering PN: 1 21 0551 63003 5007 Pacific Hwy E.,Suite 16 I fife,WA 96124(2S3.896.1011 I www.6eoresources.rocks Doc ID:PortofGrapeview.GrapeviewLoopRd.F September 2018 Figure 6c Approximate Site Location Photo obtained from Washington State Coastal Atlas(https://fortress.wa.gov/ecy/coastalatlas/tools/Map.aspx) t� 5 Not to Scale Oblique Aerial Shoreline Photograph - 1992 Proposed Soft Armor and Shoreline Mitigation GEORESOURCES xxx Grapeview Loop Road Mason County, Washington earth science & geotechnical engineering PN: 121055163003 S007 Pacific Hwy E.,Suite 16 1 File,WA 98424 1 253.896.1011 I www.georesources.rocks Doc ID:PortofGrapeview.GrapeviewLoopRd.F September 2018 Figure 6d EXISTING EXISTING CONCRETE CONCRETE BULKHEAD BULKHEAD APPROX.EXTENT OF REGRADED SHORELINE APPROX.EXTENT TO BLEND INTO EXISTING OF ERODING SLOPE/ BURY BOULDER WITH UPLAND TERRACE(SEE / SHORELINE SCOUR APPROX.ALIGNMENT OF CROSS-SECTION SHEET 8) CHAIN MIN.3 FEET TO DYSFUNCTIONAL ANCHOR LOGS(TYP.) TIMBER PILE BULKHEAD ` Jr PROVIDE 7-X WIDTH ANCHOR 3 TO 4 IA,) / EXISTING TIMBER PILE GRAVEL PATH TO BEACH LOGS O MIN.DIA) (1 f TO BE REMOVED- WITH D BOULDERS TO APPROX-34 ABOVE SUBSTRATE, BURIED BOULDERS O APPROX.10 BELOW SUBSTRATE PLANT SHORELINE EMBED BOULDERS 38"TO 42"DIA. WITH NATIVE SPECIES TO DEPTH OF 1 FOOT OR I HEIGHT, / (SEE CROSS-SECTION / (1 OR 2 PER LOG) ON SHEET 8&PLANT / LIST ON SHEET 9) APPROX.OHW / APPROX_OHW APPROX.MHHW / APPROX.MHHW REGRADE ERODED SLOPE APP X. 1418 ELEV. TO MAX.2:1 SLOPE / ° GRADE SLOPE(AFTER PILES)_o I REMOVAL OF BULKHEAD AND SLOPEEXISTING BEACH GRADE TO OHW PACIIIFIC / BURY BOULDER WITH CHAIN OYSTERBED j l+ TO ANCHOR LOG OW.)SEE / / b CROSS-SECTION ON SHEET 8 EXISTING / EXISTING 7/ft/ / CONCRETE / CONCRETE BULKHEAD gU( (EAp / EXISTING SHORELINE CONDITIONS PROPOSED SHORELINE STABILIZATION AND MITIGATION NOTES: Soft Shore Stabilization Site Plan Site Plan provided by Soundview Consultants,LLC t Proposed Shoreline Stabilization Not to Scale NORTH G E O R E S O U RC E S xxx-Grapeview Loop Road Mason County,Washington earth science&geotechnical engineering PN:121055163003 S002 ewllt H,L.Sidle 16 1 611e,WA 51026 1 253.896.1011 1—.1eerwewtef.ret6f Doc ID:PortofGrapeview.GrapeviewLoopRd.SP December 2018 Figure 7a APPROX.14' 2V EXISTING is, ERODED SLOPE APPROX.LOCATION AND UPLAND OF PREVIOUS PILE NATIVE 18, BULKHEAD AND SHORELINE UPLAND _ �'--_� IUPLANDPLANTS LOGS WITH I\ JUTE MAT SLOPE is ROOTWADS / ROUNDING I OCCASIONAL / AT GRADE 1 SLOP RE-GRADE SLOPE TRANSITION I EMBEDDED BOULDER 6: � (MAX 2:7 SLOPE) 15• 36"TO 42"DIM- 0 OR 2 PER LWD) 11 F t HwBURIED BOULDER u-1e WITH DRILLED HOLE GALV-STEEL CHAIN j FOR ANCHORING (OR SUBSTITUTE APPROVED CHAIN(TOP OF T MIN. 13' BY PROJECT BIOLOGIST) BOULDER 3'BELOW SUFFICIENT TO SECURE BEACH GRADE) I LOAD OF LOG PULTNUNARY EXISTING INFOTION ONLY I SLOPE iI I NOT FOR CONSTRUCTION 1 I CROSS-SECTION-MITIGATION AREA 2 SHORELJINE STABELIZATION Elevation/Section provided by Soundview Consultants, LLC S Not to Scale Soft Shore Stabilization Detail �- Proposed Soft Armor and Shoreline Mitigation xxx Grapeview Loop Road GEORESOURCES Mason County, Washington PN: 121055163003 earth science & geotechnical engineering 5007 Pacific Hwy E.,Suite 16 1 Fife,WA 98424 1253.896.1011 1 www.seoresources.rocks Doc ID:PortofGrapeview.GrapeviewLoopRd.F December 2018 Figure 7b ' �',�'z7,••;; ;h 4..0 . Photo - Sept 20, 2018 Looking north along failing bulkhead from south property line. S Not to Scale Site Photographs Proposed Soft Armor and Shoreline Mitigation GEORESOURCES xxx Grapeview Loop Road Mason County, Washington earth science & geotechnical engineering PN: 121055163003 5007 Pacific Hwy E.,Suite 16 I Fite.WA 96024 1253.E96.1011 I www.Storesources.rocks Doc ID:PortofGrapeview.G rap eviewLoop Rd.F September 2018 Figure 8a x �IIrwr`! 1 Looking • bulkhead Site Photographs MasonProposed Soft Armor and Shoreline Mitigation xxx Grapeview Loop Road GEORESOURCES • Washington earth science & • ' 121055163003 ►� K �'C/ � +- � •rig � - °1,. oroMILDIR m .,• •Lo .•• .•• ••••• •• •• 1