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HomeMy WebLinkAboutGEO-Tech - BLD Engineering / Geo-tech Reports - 10/29/2021 RECEIVEE", PLANNNG OCT 29 2021 12,c, 615 W. Alder Street GEOTECHNICAL ENGINEERING REPORT FOR THE RETRO-FIT OF AN EXISTING FAILING 47' LONG CONCRETE BULKHEAD for Property Located at 70 Madrona Beach Ln, Union, Mason County, WA 98592 (Parcel #: 32232-54-00013) Prepared for: Robert G. Woolston 5409 91' Ave SE Mercer Island, WA 98040 rwoolstonCc)perkinscole.com Prepared by: MET Engineering, PLLC 1018 E. Wishkah St. Aberdeen, WA 98520-2937 (360) 310-0270 cell (360) 289-0958 bus SMortaLt)aol.com Contact: Steven P. Morta, P.E. Oct. 5, 2021 Oct. 5,2021 Page I of 6 MET Engineering, PLLC To. Robe Woolston Robert G. Owner , 5409 91"Ave SE Mercer Island,WA 98040 1-"oo I sto Wa Perk inscole.com Subject: SHORELINE GEOTECHNICAL ASSESSMENT for Property Located at 70 Madrona Beach Ln,Union,WA 98592, Parcel#:32232-54-00013 Scope of Review and Site Assessment Objectives On Thursday September 23,2021 this geotechnical engineer visited the above site to inspect the existing condition of the concrete bulkhead and also observed major concrete cracking of the neighbor's attached bulkhead to the north. Digital color photographs were taken and have been included with this shoreline geotechnical assessment for documentation purposes. This assessment will focus primarily on the need for retrofitting the existing concrete bulkhead which shows signs of leaning outward and it also appears that the weep holes located at the bottom of the bulkhead are plugged. This would result in increased hydrostatic pressure buildup behind the existing bulkhead. Furthermore,extensive cracking of this concrete bulkhead were observed as seen in the attached color photographs. This geotechnical engineer took pictures of the large cracks in the neighbor's bulkhead which is directly attached to the existing bulkhead at the north end of the property. It is recommended that retrofit work on the leaning bulkhead will need to get started right away since the neighbor's wall appears to be in imminent danger of collapse,especially if there is an adverse combination of high winds and high tide which could place large hydrostatic forces on the bulkhead itself. Site Development The existing bulkhead is currently providing protection for the single story residence especially during an adverse combination of extreme high tides and a storm event where the winds could get as high as 85 mph basic wind with an ultimate wind velocity of 110 mph and 3 second gusts. Also,there are two green 2-foot diameter sewer manhole covers located approximately 15 to 20 feet from the bulkhead. This is another reason for retrofitting the existing bulkhead to not only protect the residence but also the septic tank located between the existing bulkhead and the residence as shown on engineering Sheet 2.0. As mentioned at the beginning of this assessment,the neighboring bulkhead which is connected to the existing bulkhead is severely cracked and could collapse if nothing were done to repair the 3 to 5 inch wide cracks as can be on Sheets 3.0 through 5.0. 1018 E. Wishkah St.. Aberdeen. WA 98520-2937 (360)310-0270 c. (360)289-0958 b. Worta.a aol.com _ _..,. ......_......_...____..._...__...__._. _._._..._�� _.._......_..__..__ Oct. 5,2021 MET Engineering, PLLC Page 2 of 6 Surface and Subsurface Water Conditions Regarding the subsurface water conditions, it did appear that the weep holes located near the bottom of the concrete bulkhead appeared to be plugged. This has the potential of increasing the hydrostatic buildup behind the wall which may also be contributing to the outward lean on the bulkhead. There did not appear to be any evidence of current or past standing water on the landward side of the existing bulkhead due to the free draining Alderwood granular sandy loam soils. Assessment of Site Vegetation The existing vegetation on the landward side of the concrete bulkhead consists primarily of landscaped lawn with little to no indigenous vegetation present until one gets closer to the driveway located on the back(west side)of the house. Most of the area of around the single-story residence has been landscaped. Assessment of Regional and Site Geology as well as Geomorphology The geological unit for this area has been identified as a Qad, i.e., a Quanternary till outwash, and glaciolacustrine sediments locally includes loess,talus,and lacustrine deposits. On the uphill side of the main highway (SR-108),the hill side begins to steepen in some places and there have been some significant slides along this main highway. But, fortunately,the topographical layout on the landward side of the bulkhead is essentially level and flat. The primary reason the concrete bulkhead is currently leaning approximately 5 inches toward the water, is more than likely due to the hydrostatic pressure buildup since the weep holes at the bottom of the wall appear to be Plugged, It is to be understood, that water is actually quite heavy at 62.4 lbs/cubic foot. Furthermore,it appears, also, that the bulkhead footings may have been undersized to begin with. It is important that the retrofitted bulkhead located behind the existing bulkhead, be well drained from the top of the wall down to the base of the new bulkhead. As just mentioned above, the area on the landward side of the bulkhead is mostly level and flat. The Alderwood gravelly sandy loam soils extend at least 5'to 7'down behind the bulkhead seawall with glacial till type soils located below the top five to seven feet of soil. Also, as mentioned previously,the slopes on the uphill side of SR-108 can steepen quite rapidly and slides have been recorded on the west side of SR-108 especially after periods of continuous rainfall where the soils have become soft and saturated. Wave action from Hood Canal have resulted in some scouring at base of the bulkhead which in some places has exposed the bulkhead footing which could eventually result in more outward leaning and potentially eventual collapse of the bulkhead within the next 3 years if nothing was done. It also has been known that bulkheads have a tendency to redirect the force of the wave in 1018 E. Wislikah St., Aberdeen. WA 98520-2937 (360)310-0270 c, (360)289-0958 b, S�lorta a aol.cum Oct. 5,2021 Page 3 of 6 MET Engineering, PLLC a lateral direction and not necessarily absorb any wave force. However, it is important that this existing bulkhead gets retrofitted with essentially another reinforced concrete bulkhead behind it to provide greater protection of the residence with a preliminary retrofit design shown on Sheet 2.0. It is also known that due to the phenomenon of global warming, that adverse combinations of high winds and unusually high tidal events,that this can potentially increase the wave force and could compromise the integrity of the wall. This is another reason why the new retrofitted bulkhead needs to be constructed right away primarily to protect the residence. There is the possibility that if nothing was currently done,that the existing concrete bulkhead could collapse within the next 3-years. Evaluation of Erosion and/or Flooding Issues The existing concrete bulkhead has provided protection for the single family residence for at least 40 or more years and that more exposure of the undersized bulkhead footing is becoming more evident. This has resulted in the concrete bulkhead leaning outward toward the water several inches and could be just a matter of time before this seawall structure fails completely. It is to be noted that there's was also signs of major 3 to 5 inch wide cracks along the adjacent bulkhead on the north side of the north property line which also showed signs of settling due to the gradual soil erosion at the base of the retaining wall. Structural Consequences if No Action Is Taken to Retrofit the Existing Bulkhead Due to the gradual soil erosion and undermining of the existing bulkhead footing, this has resulted in several inches of outward leaning of the seawall toward the canal side. Significant concrete cracks observed within the face of the bulkhead wall also are signs of potential seawall collapse within the next three years if nothing were done to retrofit the existing concrete bulkhead. Furthermore, the potential failure of the adjacent bulkhead directly to the north could have catastrophic consequence to the existing bulkhead. If collapse should occur of the neighbor's bulkhead,the residential structure located approximately 35-feet back from the seawall would be in danger including its occupants. Also,if there should be an adverse combination of severe storm events and extremely high tides,this could result in significant hydrostatic forces as well as severe wave forces acting on the bulkhead that could result in potential failure of the seawall. Alternative"Soft" Approaches to Retrofit the Failing Bulkhead Other soft approaches such as a gravel berm or stacking of logs would not work in this case since the concrete bulkhead has been in its present location for over 40 years or more,and that replacing this structure with"soft"alternative would not be feasible. 1018 L. WWishkah St., Aberdeen, WA 98520-2937 (360)310-0270 c. (360)289-0958 b, Worm u`aol.com ..... ......................_.....__......—.__.................................._ ............._........ .......................___................ Oct. 5,2021 -5r 20 Page 4 of 6 :MET Engineering, PLLC Retrofit Bulkhead Work is the Minimum Size Necessary It is planned that an interior retrofitted reinforced concrete bulkhead will be constructed directly behind the existing bulkhead to minimize any adverse effects to any shoreline ecological functions. As a result,there will be no retrofit work on the water side of the existing bulkhead thus,preserving the shellfish and marine life along the existing shoreline. Upslope Geomorphology,Upslope Water bodies,Wetlands,Groundwater, Seepage There was no evidence of any upland water bodies or wetlands and was relatively flat and level with no groundwater or seepage flowing toward the existing bulkhead that will be retrofitted since it is currently leaning several inches in the waterward direction. Depth to Hard or Competent Soils The approximate depth to hard till type soils is located at least 7 feet below the top of the existing seawall. However, due to relatively small footing (approximately 2 to 3' wide by —1 foot deep) the wall is currently leaning outward even though it is resting on hard,competent soils. Also,since the weep holes appear to be plugged water behind the seawall will tend to saturate the soils behind it and due to hydrostatic pressure buildup will have a tendency to increase the soil density,i.e.,the weight behind the wall. Any Evidence of Slope Instability in the general area There were no signs of slope movement such as curve tree trunks. All the tree trunks growing on the relatively shallow face of the slope were growing near vertical indicating long term slope stability. There were no signs recent or past slides in the area that would have generated escarpments, i.e.,near vertical steep bare areas on the slope face. None were encountered. History of Landslides in the Referenced Maps It is to be noted that this geotechnical engineer has observed a number of slides along the north side of SR-108 due to the nearly 2:1 (horizontal to vertical) slopes along this side of the road. Fortunately, Madrona Beach Lane where the existing bulkhead is located is at least a couple hundred feet from SR-108 where the steep slides are located. Detailed Site Plan and Detailed Cross-section A detailed site plan and a typical bulkhead wall cross-section is shown on engineering Sheet 2.0. This site plan also shows the proposed preliminary retrofit of the existing bulkhead where all the work is done on the landward side and none on the waterward side of the bulkhead. It is also to be noted that C.G. Structural Engineers will be providing the final analysis and design for the 1018 E. Wishkah St., Aberdeen. WA 98520-2937 (360)310-0270 c. (360)289-0958 b. SMorta'i aol.com Oct. 5,2021 Page 5 of 6 MET Engineering, PLLC retrofitted concrete bulkhead. The retrofit design in this Shoreline Geotechnical Assessment is to be considered only Preliminary. Conclusions and Recommendations 1. It is the conclusion of this geotechnical engineer that the existing concrete bulkhead needs to be retrofitted right away, i.e., reinforced with another bulkhead constructed just on the landward side of the current bulkhead. This way there will be little to no loss of ecological functions along the adjacent Hood Canal shoreline. 2. If nothing were done to retrofit the existing bulkhead, there is the potential of failure, i.e., collapse within the next 3-years that would then endanger the residence and its occupants located behind,the landward side of the bulkhead. 3. Furthermore, the attached neighbor's bulkhead is definitely in the process of failing and that when this occurs, this seawall collapse could also adversely affect the Woolston bulkhead as well causing it to collapse as well. Major cracking at least 5" wide or more and settlement were observed on the neighbor's seawall and appears that it is just a matter of time before the neighbor's bulkhead fails. 4. Two septic manhole covers were observed located approximately 15 to 20' from the bulkhead and if the bulkhead should fail,then the septic tank would eventually fail as well. This would adversely affect the water quality of Hood Canal due to the septage that could potentially originate from the damaged septic tanks due to seawall failure. This shoreline geotechnical assessment has been prepared per standard accepted engineering practice and that this report is only to be used for this site. Should there be any unforeseen conditions during construction such as a change in plans or adverse weather conditions, this geotechnical engineer shall be contacted immediately at (360) 310-0270 to resolve any site prep related issues that may arise. The call will then be followed by an e-mail so that it will be documented with a date and time when any changes have been made at this site. Any questions or comments regarding this shoreline geotechnical assessment can be addressed by contacting this geotechnical engineer directly at(360) 310-0270 or by e-mail at S N i,_,,. I xoni. Respectfully Submitted, p Ito y O Steven P. Morta,P.E. °,�� �F 0758�� (360) 310-0270 s`r�ONAt 1018 E. Wishkah St., Aberdeen, WA 98520-2937 (360)310-0270 c. (360) 289-0958 b, Sklorta a aol.com 7 120 Oct. 5,2021 Page 6 of 6 MET Engineering, PLLC References: 1. Online Websoil Survey prepared by the Natural Resources Conservation Service,USDA. 2. littps:.'.geolotz\12ortal.dnr.wa.Wv was referenced for the applicable geologic unit. 1018 E. Wishkah St.. Aberdeen, WA 98520-2937 (360)310-0270 c, (3)60) 289-0958 b, 9vlorta a aol.com .................. .................................. ...........-.......................................... ............. Go gle Maps 70 Madrona Beach Ln PtIOCS CAA'Af- 4ie Map data 02021 Google 70 Madrona Beach Ln Union,WA 98592 0 (A) �o; .� a Directions Save Nearby Send to your Share phone • 9W39+X6 Union,Washington .......... ................- ................................ ............... ...............1-1-1.1-1----................ ............ .................................................................................................... i Zv PARCEL MAP FOR 70 EAST MADRONA BEACH LN, UNION, WA 9859Z #: 32232-54-00013 ennpon 322325400017 ONA.BEAC�i 1A BEACH LN 1 3223254$OOY34iE MADRONA BEACH LN 322325WO016 j 120E MADRONA BEACH LN 1fK)E PA-DU EtEA,:V31.N 80 E MADRONA BEACH LN S • 322325400014 } 321400030 70 E MADRONA BEACH L • 3 223 25 400013 69.E'MADRONA BEACH LN •322325400012 50 E PA�AIC��BEACH LN 40 E MADRONA BEACH LN • 322325400010 i ------------------ p 30 E MAD RIzA BSA4i UUMN PARCEL,MAP Prepared by: MET Engineering,PLLC,1018 E.VVIshkah St,Aberdeen,WA 98520-2937 (360)310-0270 cell,(360)289-0958 bus, SMorta@aol com Prepared for.Robert G.Wootaton Sep.27,2021 Site Visit on Thu.9-23-2021 SHEET 1.0 /%o - -sue hL �:1� 1 :.�tF • A � Area of Interest(AOI) Soil Data Explorer Download Solis Data Shopping Cart(Free) Printable Vers{en Add to Shopping Cart] 1.'k._-1 i JI' =1110 41=.1 '3 fi j AiAkL i 40* .Ain k _ Waming:Soil Map may not be valid at this scale. J t Printable Version; neporc—map unit uescripaon 11120 Mason County,Washington(WA645) Mason County,Washington �-c—t Mason County, Washington (WA645) Ac—Alderwood gravelly sandy loam,15 Map Map Unit setting Unit Map Unit Name in percen National map unit symbol:2tb27 of AOI of AOI Elevation.,0 to 1,000 feet Mean annual precipitation:25 to 60 inches c Alderwood gravelly 0.6 57.9% Mean annual air temperature:46 to 52 degrees F sandy loam, 15 to Frost-free period:160 to 240 days 30 percent slopes Farmland classification.,Farmland of statewide importance Totals or Air of 1.1 100.0e/o Map Unit Composition Interest Atderwood and similar soils:85 percent Minor components: 15 percent FOIA i Accessibility Statement I Privacy f Estimates are based on observations,descriptions,and transects of the mapunit. Description of Alderwood Setting Landform:Ridges,hills Landform position(two-dimensional):Backsiope 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 awl-7 to 21 Inches:very gravelly sandy loam awl-21 to 30 inches:very gravelly sandy loam ag-30 to 35 inches:very gravelly sandy loam 2Cdl-35 to 43 inches:very gravelly sandy loam 1Cd2-43 to 59 inches:very gravelly sandy loam Properties and qualities Slope: IS to 30 percent Depth to restrictive feature:20 to 39 inches to densic material 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 supply,0 to 60Inches.,Very law(about 2.7 inches) Interpretive groups Land capability classification(irrigated):None specified Land capability classification(nonirrigated):4e Hydrologic Soil Group:B Forage suitability group:Limited Depth Soils(0002XN302WA), Limited Depth Soils(GO02XS301WA),Limited Depth Soils (GO02XF303 WA) Other vegetative classification:Limited Depth Soils(GO02XN302WA), Limited Depth Soils(G002XS301WA),Limited Depth Soils (GO02XF303 WA) Hydric soil rating:No Minor Components Everett Percent of map unit:5 percent Landform. Karnes,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 Shaker 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 position(three-dimensional):Dip Down-slope shape:Concave,linear Across-slope shape:Concave Hydric soil rating:Yes PRELIMINARYRETRO-FIT BULKHEAD DETAIL FOR 70 EAST MADRONA BEACH LN 12 UNION, WA 98592, Parcel#: 32232-54-00013 20 RESIDENCE V=10 FT SEPTIC TANK t I 0' 2' 4' 68' 10' 12' 14' 16' 18' 20' 2'dia.MANHOLE I W NORTH COVERS w ;35'FROM O z I BULKHEAD I z0 ! ADD 3 BUTRESS WALLS FOR X S I-4 E o LONG TERM BULKHEAD STABILITY ._ rp 10 01 5' 5' S' o S r----� r----� r----� ID p! ' B t 7 m MAJOR -----L-1 ----- -'-----�-1 '- ----------L_1 ,:__ BREAK IN I L---=-- --------- ------------ ---- --=------------ ` RETAINING ORDINARY HIGH WATER MA (0 WM)@ BASE OF S WALL 47-0" B ADD 1-FOOT THICK x 7'HIGH REINFORCED CONCRETE RETRO-FIT WALL w/#5 REBAR @ 12"O.C.EA WAY 3 COMPUTE OVER-TURNING MOMENT,WO): F=(1/2)(Ca)(RHO)(H"2) N where Ca=Coefficient of Active Earth Pressure ___-___ _ (1 -Sin Phi)/(1 +Sin Phi) where Phi = Internal Friction angle ofAlderwood ADD THREE REINFORCED N gravelly sand loam soils=23 Begs o BUTRESS WALLS As then Ca=(1 -Sin 23)I(1 +Sin 23)=0.438 ice, , --SHOWN ABOVE wJ 1'THICK r- FOOTINGS,#5 REBAR 12" '' ` O.C.EA WAY Q�MHHW Rho=soil density=127 Ibs/cu.ft. H =8 feet iv F=(1/2)(0.438)(127)(8' '2)=1,780 Ibs/lin.ft. then: M(0)=F x(113)H=1,780 x(1/3)(8')=4,750 ft-Ibs/lin.ft. TYPICAL CROSS-SECTION&B: COMPUTE RESISTING MOMENT,M(R),FROM 3 BUTRESS WALLS: WITH BUTRESS WALL DETAIL M(R)=Weight of the three Butress Walls x Moment Arm =[{[(6'x8'x1')+(5'x8'x1')Ix(150pcf)x3)x6'/47']+ {[(3'x 1')(2)+(7'x 1')]x 150 pcf X 151 =[5,060+2,900)=7,960>4,750 ft-lbs (OKAY) COMPUTE FACTOR OF SAFETY FS: FS=7,96014,750=1.68>1.60 (OKAPI RETRO-FIT RETAINING WALL DETAIL Prepared by: MET Engineering,PLLC,1018 E.Wshkah St Aberdeen,VA 98520.2937 (360)310-0270 cep,(360)28"958 bus, Sf lona@ad com Prepared for:Robert G.Woo/stop Od 4 2021 1 e Isit On Thu. - SHEET 2.0 _ .................. ... ...... .... ._._._.._ ................... ......_... �3 AERIAL VIEW FOR 70 EAST MADRONA BEACH LN, UNION, WA 98592, #: 32232-54-00013 NORTH WS— sE a, JA Pb r� 7 � M .r � • .�* � ter,^ EXISTING 47'LONG BULKHEAD AERIAL VIEW i Prepared by: MET Engineering,PLLC,1018 E.Wishkah St,Aberdeen,WA 98520-2937 (360)31M270 cell,(360)289-0958 bus, SMorta@aoi com Prepared for:Robert G.Woolston Sep.30,2021 ite sit on u. 2021 $MEET 2.0 A from 1 to 2:30 pm Jul MAJOR CRACK IN BULKHEAD ON NORTH SIDE OF NORTH PROPERTY LINE Z� EMMINENT BULKHEAD FAILURE CAN BE SEEN HERE WHICH COULD POTENTIALLY CAUSE SERIOUS DAMAGE TO THE WOOLSTON CONCRETE BULKHEAD THAT IS DIRECTLY ATTACHED TO IT IF NOTHING WERE DONE TO RETROFIT THE EXISTING BULKHEAD. (CRACKS ARE 3 TO 5"WIDE IN SOME PLACES.) ti MAJOR CRACK IN BULKHEAD ON NORTH Prepared by: MET Engineering,PLLC,1018 E.V+hshkah St,Aberdeen,WA 98520-2937 SIDE OF NORTH PROPERTY LINE (360)310-0270 cell,(360)289-0958 bus, Shona@aoi com Prepared for.Robert G.WooWon Sep_30,2021 Site Visit on Thu.9-23-2021 SHEET 3.0 from 1:00 to 2:30 m 3 TO 5" DROP IN CRACKED BULKHEAD ON NORTH SIDE OF NORTH PROPERTY LINE IT APPEARS THAT THE NEIGHBOR'S BULKHEAD HAS ALSO SETTLED SEVERAL INCHES AS INDICATED BY THE SIZE OF THE GAP WHERE DAYLIGHT CAN BE SEEN THROUGH THE CRACK. NO REBAR REINFORCEMENT CAN BE SEEN WITHIN THE NEIGHBOR'S CONCRETE BULKHEAD _ r A . f z y■ p�� II�^li kwA E 3 TO 5 INCHES OF BULKHEAD SETTLEMENT Prepared by: MET Engineering,PLLC,1018 E.Wishkah St,Aberdeen,WA98520-2937 HAS TAKEN PLACE. (360)310-0270 cen,(360)289-0958 bus, Shtorta@aol com Prepared for.Robert G.Woolsfon Sep 23,2021 Site Visit on Thu.9-23-2021 SHEET4.0 from 1:00 to 2:30 pm MAJOR CRACK IS LESS THAN 10'AWAY FROM THE WOOLSTON'S BULKHEAD v THIS SHOWS HOW CLOSE THE NEIGHBORS' FAILING BULHEAD IS TO THE WOOLSTON'S BULKHEAD. THIS IS THE MAIN REASON FOR RETROFITTING THE WOOLSTON BULKHEAD AS SOON AS POSSIBLE, I.E.,TO PROTECT, MOST IMPORTANTLY,THE RESIDENCEAND ITS OCCUPANTS. f r II i r r r r ,r f. 1 }-;' q :r s y H ti MAJOR BULKHEAD CRACK IS WITHIN A FEW FEET Prepared by: MET Engineering,PLLC,1018 E.Wshkah St,Aberdeen,WA 98520-2937 TO THE NORTH PROPERTY LINE (360)310.0270 cell,(360)28"958 bus, SMorta@aol com i Prepared for.Robert G.Woolston Sep 23 2021 Site Visit on Thu. 9-23-2021 SHEET 5.0 from 1:00 to 2:30 pm I CRACKS AND RUSTS 1S VISIBLE ON THE WOOLSTON BULKHEAD 7 2p HORIZONTAL AND VERTICAL CONCRETE CRACKS CAN BE SEEN THAT EXTEND THROUGHOUT THE ENTIRE BULKHEAD RETAINING WALL. IT IS RECOMMENDED THAT THIS WALL GETS RETROFITTED RIGHT AWAY TO KEEP IT FROM FAILING COMPLETELY ESP.DURING AN ADVERSE COMBINATION OF A MAJOR HIGH TIDE AND AN EXTREME STORM EVENT. +Z x, "V e' � 4 z„ t. ti r t�.�'+Y�: - r Y��cif R./ �'� "Y 'l i ,-✓ ,. CRACKS AND RUST CAN BE SEEN ON Prepared by: MET Engineering,PLLC,1018 E.VMshkah St,Aberdeen,WA 98520-2937 THE WOOLSTON BULKHEAD (360)310-0270 cell,(360)289-0958 bus, Worta@aol com Prepared for.Robert G.Woolston Sep.23 =1 Site Visit on Thu.9-23-2021 SHEET 6.0 from 1:00 to 2:30 pm GEOLOGICAL UNIT for Property Located at 70 Madrona Beach Ln, Union, WA 98592 Parcel #: 32232-54-00013 Feature InformaWn GEOLOGIC UNIT LABEL Cad oad GEOLOGIC_UNiT_DESC:Ouaternary It ouivsash and oMcicIA,ustrtne sediments Iocatty!ncfudes Iaess,talus.and IaWSI ina deposits GEOLOGIC_UNIT POLY_500K_ID:7952 GEOLOGIC—AGE:Cuatem" :Pleistocene; LIIHOLOGY:Pleistocene cominentai giaciat drift Cr<o:nftnAli?aa^rts:.a7len-A'�'r�. GEOLOGICAL UNIT(Qad,Quantenary till,OutwaSh) j Prepared by: MET Engineering,PLLC,1018 E.Wishkah St,Aberdeen,WA 98520-2937 (360)310-0270 cell,(3W)289-0958 bus, SMorta@aol corn Prepared for: Rabett G.Wooiston Site Visit on Thu..9-23-2021 SHEET 7.0 Sep.25,2021 from 1:00 to 2:30 1 9/2 0 MASON COUNTY COMMUNITY SERVICES Shoreline Stabilization lkilklmg.Planning.Emrfonmental Health,(mmunity Health Note:This checklist must be submitted with a Shoreline Geotechnical Assessment and completed, signed, and stamped by the licensed professionals)who prepared it for review pursuant to the Mason County Shoreline Master Program. If an item is found not applicable, the Assessment should explain the basis for the conclusion. MCC 17.50.340 B.2. New structural stabilization measures shall not be allowed except as follows: a. To protect existing primary structures: i. New or enlarged structural shoreline stabilization measures for an existing primary structure, including residences,shall not be allowed unless there is conclusive evidence documented by a Shoreline Geotechnical Assessment*that the structure is in danger from shoreline erosion caused by tidal action, currents,waves, or sea level rise. Normal sloughing, erosion of steep bluffs, or shoreline erosion itself,without a scientific or geotechnical analysis, is not demonstration of need. The geotechnical assessment shall evaluate on-site drainage issues and address drainage problems away from the shoreline edge before considering structural shoreline stabilization. ii. The erosion control structure will not result in a net loss of shoreline ecological functions. This shall be demonstrated in a Habitat Management Plan as required in MCC 8.S2.170(1). iii. Primary structure means the structure or the only access associated with the principal use of the property that cannot feasibly be relocated. It may also include single family residential appurtenant structures that cannot feasibly be relocated. Applicant/Owner �%OfRT 6. WBOlS71_01V Parcel # 3Z23 2 -sq- e)o©!, Site Address '70 MA DAP"A 6)BACU Lew /JAuta�l_ W/-) 9c '<5 C Items to be included in assessment Located on Page(s): Scope of review,including landowner concerns and site assessment objectives. Discussion of site development,including the location and setback of important primary and appurtenant structures,roads and utilities. Assessment of relevant wetlands and surface water drainage and control systems. Assessment of site vegetation,including species and communities present. 22 Assessment of regional/site geology,including relevant rock/soil unit descriptions,geologic history and stratigraphic correlation. Assessment of regional/site geomorphology,including the influence of wave or tidal processes in controlling sediment transport and the evolution of the site's landform. Include assessment of 2 the drift cell sediment budget and local beach conditions. May 2018 zv/2o Evaluation of erosion and/or flooding issues,including assessment of causes,and rates or timeframes associated with each issue.Include evaluation of how historic shoreline modifications near the site may have impacted patterns of erosion. Evaluation of the amount of time until primary structures or major utilities will be damaged by wave or tidal action,based on evidence of erosion rates,a slope stability analysis or other g eotechnical considerations if no action is taken on the site. Discussion of alternative approaches to reduce risk from erosion on the site,including the use of nonstructural measures such as drainage and vegetation,and soft shoreline techniques such as gravel berms,large woody debris,or other measures. Explain why these techniques would be 3 infeasible or insufficient to reduce the threat from erosion. Discussion describing the proposed shoreline stabilization is the minimum size necessary, placed as far landward as possible and will not result in a net loss of shoreline ecological functions. A site map drawn to scale which identifies property boundaries,scale, north arrow and the location of proposed development,geologic features and ordinary high water mark(OHWM).All 1 6,c 7- .0 development setbacks should be delineated and marked. �K I Cross-section(s),identified on site map,showing both horizontal and vertical scales,and identifying important features such as: MHHW and OHWM,top and bottom of bluff,location of ��/�Fr2 upland structures and utilities,and geologic units where relevant. l Supplementary photographs. 4 rr r-01 1, ',EVE y f.M 0P7A hereby certify under penalty of perjury that I am a civil engineer licensed in the State of Washington with specialized knowledge of geotechnical/geological engineering or a geologist or engineering geologist licensed in the State of Washington with special knowledge of the local conditions.1 also certify that the Geotechnical Assessment,dated 10—s �Z j OC—r and entitled WAS VI�OrRBt.�NE �>`O't"�Gl�,rtlLtdL .��.f:Jpi�j1J� meetsallthe r o9 requirements of the Mason County Shoreline Master Program,Shoreline Stabilization Section(MCC 17.50.340),and is complete and true. 30758 � ssIONALG (Signature and Stamp) •MCC17.50.020 Definitions:Shoreline Geotechnical Assessment. A scientific study or evaluation conducted by a qualified expert that includes a description of the ground and surface hydrology and geology,the affected land form and its susceptibility to mass wasting,erosion,and other geologic hazards or processes,conclusions and recommendations regarding the effect of the proposed development on geologic conditions,the adequacy of the site to be developed,the impacts of the proposed development, alternative approaches to the proposed development,and measures to mitigate potential site-specific and cumulative geological and hydrological impacts of the proposed development,including the potential adverse impacts to adjacent and down-current properties. Geotechnical assessments shall conform to accepted technical standards and must be prepared by qualified professional engineers or geologists who have professional expertise about the regional and local shoreline geology and processes. Page 2 of 2 Disclaimer.Mason County does not certify the quality of the work done in this Geotechnical Assessment.