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HomeMy WebLinkAboutGEO2020-00008 - GEO General - 2/5/2020 Ga Q<) Zo - 000 o MASON COUNTY - y COMMUNITY SERVICES ' = x,,r Building,Planning,Environmenhl Health,Community Health Geological Assessment Instructions: This checklist must be submitted with a Geological Assessment and completed, signed, and stamped by the licensed professional(s)who prepared the Geological Assessment for review by Mason County pursuant to the Mason County Resource Ordinance. If an item is found not applicable,the report should explain the basis for the conclusion. Note:Unless specifically documented, this report does not provide compliance to the International Residential Code Sections R403.1.7 for foundations on or adjacent to slopes, Section R403.1.8 for expansive soils or section 1808.7.1 of the International Building Code Section for Foundations on or adjacent to slopes. Applicant/Owner 1,411. /. /�61A' Parcel# /Z 3/���5"Op©of 3 Site Address /U� C�iso,-, 6ouf z-✓cam-(. /J���►I�' _ l�c�if (1) A discussion of geologic conditions in the general vicinity of the proposed development, with geologic unit designation based on referenced maps. Located on page(s) R;- (2) (a)A discussion of the ground water conditions at the site, t:Cal i/ED Located on page(s) / 2- f `f'g F � 05 (b) A discussion of the estimated depth to water, $1$ VV Located on page(s)/9•Z- / P At�+er urPeLa f (c) A discussion of the quantity of surface seepage, Located on page(s) Z (d) A discussion of the upslope geomorphology, I Located on page(s) Z /�3 t- �- y G (e) A discussion of location of upland waterbodies and wetlands. Located on page(s) /Ulm 06-Ve4Y-,w (3) The approximate depth to hard or dense competent soil, e.g. glacial till or outwash sand. Located on page(s) 70g (4) A discussion of any geomorphic expression or past slope instability(presence of hummocky ground or ground cracks, terraced topography indicative of landslide block movement, bowed or arched trees indicating downslope movement, etc.). Located on page(s) :�!, Z 41FI& (5) A discussion of the history of landslicle activity in the vicinity, as available in the referenced maps and records. Located on page(s) �I�P3 (6) An opinion on whether the proposed development is within the landslide hazard area or its associated buffer or setback and the potential for landslide activity at the site in light of the proposed development. Located on page(s) &_ Z if to (7) A recommendation by the preparer whether a Geotechnical Report should be required to further evaluate site conditions and the proposed development of the subject property. Rev.February 2018 Located on page(s)eft 2 ' (8) If the presence of a hazard is determined within 300 feet of the proposed development, then the following are delineated on a geologic map/site map: (a) the area of the proposed development, Located on Map(s) 44-e 71-- �-*- (b) the boundaries of the landslide hazard area (top, both sides, and toe), CFI n�4 z� ,�" .` Located on Map(s) l.� �' ? ,� i> (c) the associated buffers (top, both sides, and toe), Located on Map(s) /f (d) building or other setbacks(top, both sides, and toe). Located on Map(s) (9) A site map drawn to scale showing the property boundaries, scale, north arrow, and the location and nature of existing and proposed development on the site. Located on Map(s) �i a 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. I also certify that the Geological Assessment, dated Z9 ZO and entitled G i � Cico �c „aSozsrc� • .� IP�S��¢.,ce Sim meets all the rk requirements of theJAps*'C0LhAyResource Ordinance, Geologically Hazardous Areas Section, is complete and true, k that the asses 'nen di}fionstrates conclusively that the risks posed by the landslide hazard can be mitigated through the included geotechnical design recommendations, and that all hazards are mitigated in such a manner as to prevent harm to property and public health and safety. (Signature and Stamp) Page 2 of 2 Disclaimer. Mason County does not certify the quality of the work done in this Geological Assessment. W§solve Environmental Project No 20-020 & Geotechnical Inc Peabody Project Geo Recon January 4,2020 Attention: Mr.RJ Peabody RJ realestate@,msn.com 360-340-0000 LIMITED SINGLE FAMILYARESIDENCE A RECONNAISSANCE SITE MASON COUNTY PARCEL NO. 123305000013 NE g�AIR,JWASH GTON� Dear Mr Peabody: 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 geologic conditions wherein Single- Family Residence(SFR)construction will be undertaken, and the general condition of the properties near the site. The subject site is located along NE Larson Lake Boulevard, B elfair, Mason County, Washington. The Mason County Parcel Number is 123305000013. The latitude is approximately 47 degrees, 27 minutes, 11.8 seconds north, and the longitude is approximately -122 degrees, 50 minutes 45.6 seconds west. The site is surrounded by residential properties developed with SFRs. The proposed construction site is located in the northeastern portion of the subject property, directly across NE Larson Lake Boulevard from the southern terminus of Captain Kidd Court. Larson Lake Boulevard provides the primary access to the 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 January 2, 2019. Our observations were preceded by a review of local geologic databases,local geology,and area slope evaluations of the immediate vicinity. Soil and Slope Research The following information provides a basis for a general understanding of the subject soils and geologic conditions: --Mason County Codes,particularly section 8.52, defines the subject slopes to the south, east,and west as being in critical areas. By definition,there are landslide and erosion hazards for the subject site. --USDA Soils The United States Department of Agriculture(USDA) Soil Survey of Mason County Area,Washington information indicates the following soil types exist on the project site: Ib: Indianola Loamy Sand 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 mostly accurate. Soils across most of the site were probed with a '/z-inch aluminum-alloy T-Probe. The gravelly sand beneath the forest duff and surficial (largely root-bound) soils showed high density, including those at the base of some open, exposed septic test pits on the site. Soils were described in the field as brown, damp, dense to very dense gravelly sands with cobbles and silt. Sands were fine and medium (USCS GM-SP). These are interpreted in the field as relatively proximal depositional energy sediments, from glacial advance outwash and alluvial processes. Based on &solve Environmental Project No 20-020 & GeotechnicA Inc Peabody Proiect Geo Recon local investigations,the depth of very dense sands is likely to be encountered at approximately three feet below the existing ground surface(bgs). Approximately eight inches of standing water was observed in the bottom of one of the septic test pits(at a depth of approximately 3 feet), and was likely from the recent rains. The standing water also implied impermeability of soils in the relatively deeper subsurface soils,and permeability of nearer-surface soils. The slope on the western margin of the site was measured by Brunton Clinometer and estimated to be between 25 and 32 percent. The slope to the south was measured at between 76 and 84 percent, and the slope to the east was a nearly vertical roadcut for the adjacent driveway. —Other Most of the local sheetflow and stormwater naturally flows down-slope,mostly downdip; southward, and westward,however the permeability of the nearest-surface sands and gravels is considered relatively high, and likely to mitigate serious downslope runoff. It is considered possible that groundwater could be transmitted across the subsurface impermeable strata, although none was observed, and no oxidation of soils was evident. No major cracks or lineations suggesting geologic problems other than the slopes being in proximity to the proposed construction site were observed. No unusual, major, areal geologic issues were noted in observable areas of adjacent properties. Some minor bowing of trees on local slopes suggested some normal soil creep. —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. Conclusions and Recommendations It is Resolve's opinion that some near-surface soils work needs to be undertaken prior to construction of the SFR on the site. The loose forest duff and root-bound topsoils are not considered suitable for construction in their current condition. It is our opinion that near-surface should be over-excavated and developed with structural fill materials, or similar solutions as footing preparation. Moreover, it is our opinion that the SFR should not be c structed near slope margins,and repeated disturbance of areas near the crest of slope should be avoided.1This pertains particularly to the east side,along the driveway cut. It is considered possible that some retention system may be required along the neighboring property margin to the east,where there is an existing adjacent driveway. No groundwater seepage was observed across the site,and the test pit ponding was discussed above. It is possible that a perched groundwater lens may be encountered at two to four feet beneath the construction area. The types of soils that were observed suggest that liquefaction is unlikely on the site. Best Management Practices (BMPs) regarding erosion control should be adhered to as construction proceeds on the subject site. If BMPs are followed and the subject slope on the footings are appropriately prepared, it is our opinion that construction and supporting elements proposed for the site will not adversely affect local slope conditions. Common practice suggests that drainage should be established behind walls facing slopes and around footings. Resolve should be contacted for inspection and recommendations regarding soils when excavations are being undertaken. 4?r3olve Environmental Project No 20-020 & Geotechnical,Inc Peabody Project Geo Recon Native plants may possibly be planted on slopes or in the immediate vicinity of the site for mitigation purposes. The following table depicts some recommended plants should such mitigation be desired: Table 1: Su ested Slope Mitigation Plants and Approximate Coverages Native Plantings Sizing Min.Spacing #of Plants S .ft.Coverage Ocean Spray (Holodiscus 1 gallon 5 feet 3 plants 30 discolor) Sala] (Gaultheria 1 gallon 5 feet 5 plants 50 shallon) Red-Flowering Current(Ribes 1 gallon 5 feet 5 plants 45 San ineum Thimbleberry (Rubus 1 gallon 5 feet 4 plants 36 arviflorus) Snowberry (Symphoricarpos 1 gallon 5 feet 5 plants 50 albus Nootka Rose 1 gallon 5 feet 3 plants 27 (Rosa Nutkana The above-listed plants may or may not be utilized or be selected by the client,however they have been shown in the past to be adequate cover for disturbed areas. Resolve does not retain a certified biologist of botanist, and provides these as suggestions only. It is noted that a full-scale Geotechnical Engineering Investigation could be necessary for the project if retaining systems are to be installed. If appropriate buffers from crests of slope are maintained, it is Resolve's opinion that construction may be able to proceed as shown in the site plan. A forty-foot buffer from the southern, steeper slope is recommended,and rigorous foundation depths may be require or t e east side driveway cut. It appears that only some additional clearing and grubbing will be required for the site. As with all construction projects in the region, standard erosion control BMP's should be employed during excavation. A Geological Assessment Submittal Form for the proposed construction project is attached to this Geo Recon Report. 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. WPSolve Environmental Project No 20-020 & Geotechnical,Inc Peabody-Proiect Geo Recon 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. t t'' Ronald P.Nance, P.G. Senior Geologist and Environmental Professional WA License No.2533 .., ` }rK ,ems•. Legend r * i. Larson Lake Blvd Site Vicinity Map �'+" :'.,,_ • Anchor r ;• NE Captain Kidd Ct +� M P.";✓fM y W� ', '!• +'"� ,�� •y�'�:,...� �1r" ,dA`�': s ��4',s� ""'�• `4� Y��m� rr ��,,, s ?rya ;OR A7*1 /'�Ct', s► ;wt,,,•ni ,.� :�•'- � ;�" y��� .,, �M r,�1j'^ . A �,.,� �;' �.,�,.��•rt► ''t 1 .y,�'+�`{►`r .� � .•, ..� � � w � iry�: r �""' r�� +' ll� ^R`-� �� p�. «+ r a I Ot ^ i •+� ` 1.: 1�;� o it �� .. _. � r ^ � � ��+ '�: �+��A�tl' {.i6 { ;, ,,�, ... ��. � ..+�=, � �''""�"'+ �.� `� .-.""•era' ����� '° s•.�a�°°"`• �.r �,r ., � c_1 . y - .!{ram. l"' _ ��r. �� �� � tt!'2 !'y. •.,�dr,."rM ..• . �\yyr�, «� �`� � !� , + , 1.+� � ,�� ' .,py � \ r�•1�' ` �, t.; � ,� {•�f�� ��'.y ,rye}��"'x�'�,M ., a trl�� ,, „ •r y if w .. • � .E //e .:w a. .M ��:.. ,1e'� �' - ?• � � 'r`a,1� r' .�I ♦' �� e r a�� tY r N%'.,� .r i��'�" = r FA riw Figure 1 : PROJECT: Resolve Environmental Vicinity Map Limited Geological Reconnaissance & Geotechnical, Inc. Mason County Parcel No. 1233050000013 Larson Lake Boulevard (sso)ese-leas Project No. 20-020 Belfair, Washington N resolveeg@comcast.net Date: January, 2020 Prepared for: Mr. RJ Peabody asolve Environmental & Geotechnical Inc USDA INFORMATION Soil Map—Mason County,Washington (Larson Lake Blvd Site Soils Map) 6115W 511580 511 60D 5116M 511640 511660 51168D 51170D 511I pa CG R M . r r 7-1 R ,, oft .. IAW- Soil Mah may i�t 5e,v.a1'id at th! 5 ale. } 47°27TN 511900 511520 511540 5iloX 51162D 5116=0 511660 511720 3 3 Map Scale:1:1,090 if printed on A landscape(11"x 8.5')sheet Meters I� N 0 15 30 60 90 Feet 0 5D 100 200 300 A Map projection:Web Mercator Comer coordinates:WG584 Edge tics:UTM Zone 1ON WGS84 Natural Resources Web Soil Survey 1/2/2020 r Conservation Service National Cooperative Soil Survey Page 1 of 3 Soil Map—Mason County,Washington (Larson Lake Blvd Site Soils Map) MAP LEGEND MAP INFORMATION Area of Interest(AOI) Spoil Area The soil surveys that comprise your AOI were mapped at 1:31,700. Area of Interest(AOI) Stony Spot Soils Very Stony Spot Warning:Soil Map may not be valid at this scale. Soil Map Unit Polygons Enlargement of maps beyond the scale of mapping can cause Wet Spot 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 l3 Soil Map Unit Points contrasting soils that could have been shown at a more detailed Special Line Features scale. Special Point Features Blowout Water Features Streams and Canals Please rely on the bar scale on each map sheet for map Borrow Pit measurements. Transportation Clay Spot Rails Source of Map: Natural Resources Conservation Service i-+-+ Web Soil Survey URL: Closed Depression Interstate Highways Coordinate System: Web Mercator(EPSG:3857) W Gravel Pit US Routes Maps from the Web Soil Survey are based on the Web Mercator projection,which preserves direction and shape but distorts Gravelly Spot Major Roads distance and area.A projection that preserves area,such as the Landfill Local Roads Albers equal-area conic projection,should be used if more accurate calculations of distance or area are required. Lava Flow Background Aerial Photography This product is generated from the USDA-NRCS certified data as Marsh or swamp of the version date(s)listed below. Mine or QuarrySoil Survey Area: Mason County,Washington Survey Area Data: Version 15,Sep 16,2019 Miscellaneous Water Perennial Water Soil map units are labeled(as space allows)for map scales 1:50,000 or larger. Rock Outcrop Date(s)aerial images were photographed: Apr 1,2016—Sep 27, Saline Spot 2016 Sandy Spot The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background Severely Eroded Spot =y imagery displayed on these maps.As a result,some minor Sinkhole shifting of map unit boundaries may be evident. Slide or Slip Sodic Spot Web Soil Survey 1/2/2020 USD:\ Natural Resources Page 2 of 3 Conservation Service National Cooperative Soil Survey Soil Map—Mason County,Washington Larson Lake Blvd Site Soils Map Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI Ee Everett gravelly loamy sand,5 1.6 26.6% to 15 percent slopes lb Indianola loamy sand,5 to 15 4.3 73.4% percent slopes Totals for Area of Interest 5.9 _ _ 100.0% usi)•% Natural Resources Web Soil Survey 1/22020 Conservation Service National Cooperative Soil Survey Page 3 of 3 d Site Soils Blvd La ke v Map Unit Description: Indianola loamy sand,5 to 15 percent slopes—Mason County, Larson Description Washington Mason County, Washington lb—Indianola loamy sand, 5 to 15 percent slopes Map Unit Setting National map unit symbol: 2t635 Elevation: 0 to 980 feet Mean annual precipitation: 30 to 81 inches Mean annual air temperature: 48 to 50 degrees F Frost-free period. 170 to 210 days Farmland classification: Prime farmland if irrigated Map Unit composition Indianola and similar soils: 85 percent Minor components: 15 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Indianola Setting Landform: Eskers, kames, terraces Landform position (three-dimensional): Riser Down-slope shape: Linear Across-slope shape: Linear Parent material: Sandy glacial outwash Typical profile Oi-0 to 1 inches: slightly decomposed plant material A- 1 to 6 inches: loamy sand Bwl -6 to 17 inches: loamy sand Bw2- 17 to 27 inches: sand BC-27 to 37 inches: sand C-37 to 60 inches: sand Properties and qualities Slope: 5 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 to very high (5,95 to 99.90 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: Low(about 3.9 inches) Interpretive groups Land capability classification (irrigated): 4e Land capability classification (nonirrigated): 4s Hydrologic Soil Group: A Forage suitability group: Droughty Soils(G002XN402WA), Droughty Soils(G002XS401 WA) Web Soil Survey 1/2/2020 Natural Resources Page 1 of 2 conservation Service National Cooperative Soil Survey Larson Lake Blvd Site Soils Map Unit Description: Indianola loamy sand,5 to 15 percent slopes—Mason County, Description Washington Hydric soil rating: No Minor Components Alderwood Percent of map unit: 8 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 Everett Percent of map unit: 5 percent Landform: Karnes, eskers, moraines Landform position (two-dimensional): Shoulder, footslope Landform position (three-dimensional): Crest, base slope Down-slope shape: Convex Across-slope shape: Convex Hydric soil rating: No 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 Data Source Information Soil Survey Area: Mason County, Washington Survey Area Data: Version 15, Sep 16, 2019 Web Soil Survey 1/2/2020 i SIM Natural Resources Page 2 of 2 �6 conservation Service National Cooperative Soil Survey SL#1 0-60" Sand Loam SL#2 6-60" Sand Loam SL#3 0-28" Sand Loam 28" Mottled fine sand (Area apparently cut) m M r- NE Larson Blvd � o 0 57.56' e1+12 N o 45 � e1+14' II w *' Z o \ 10' DW Three Bedroom Home 100%Reserve s m 0,O Z re) 5' XSL#3 34' i No Build o 100%Reserve o -- ._ 60' 1 of --�. avity ------ -` D-Box - � o� v - el 0' 75.38 Corner -f�/'d 'el 0' Mddct�d c GEO1-02-0 -Mog Mason County Review Checklist For a Geological Assessment Instructions: This checklist is intended to assist Staff in the review of a Geological Assessment. The Assessment is reviewed for completeness with respect to the Resource Ordinance. If an item is found to be not applicable, the report should explain the basis for the conclusion. The Assessment is also reviewed for clarity and consistency. If the drawings, discussion, or recommendations are not understandable,they should be clarified. If they do not appear internally consistent or consistent with the application or observations on site, this needs to be corrected or explained. If resolution is not achieved with the author, staff should refer the case to the Planning Manager or Director. Applicant's Name: Permit#: 0 -Uo Parcel#'s: SQ- OV01 Date(s)of the Document(s) reviewed:OZ DZ� 1. A discussion of geologic conditions in the general vicinity of the proposed development, with geologic unit designation based on referenced maps. OK? ✓ Comment: 2. (a) A discussion of the ground water conditions at the site, OK? ✓ Comment: (b) A discussion of the estimated depth to water, OK?_,Z Comment: (c) A discussion of the quantity of surface seepage, OK? ✓_Comment: (d) A discussion of the upslope geomorphology, OK? I/" —Comment: (e) A discussion of location of upland waterbodies and wetlands. OK? ✓ Comment: 3. The approximate depth to hard or dense competent soil, e.g. glacial till or outwash sand. OK? ✓ Comment: 4. A discussion of any geomorphic expression of past slope instability(presence of hummocky ground or ground cracks, terraced topography indicative of landslide block movement, bowed or arched trees indicating downslope movement, etc.). OK? ✓ Comment: 5. A discussion of the history of landslide activity in the vicinity, as available in the referenced maps and records. OK? ✓ Comment: 6, An opinion on whether the proposed development is within the landslide hazard area or its associated buffer or setback and the potential for landslide activity at the site in light of the proposed development. . OK? ✓ Comment: 7. A recommendation by the prepare whether a Geotechnical Report should be required to further evaluate site conditions and the proposed development of the subject property. OK? V Comment: 8. If the presence of a hazard is determined within 300 feet of the proposed development, then the following are delineated on a geologic map/site map: Page 1 of 2 Form Effective June 2008 (a) the area of the proposed development, OK?�—Comment: (b) the boundaries of the landslide hazard area(top, both sides, and toe), OK? `/ Comment: -(c) the associated buffers (top, both sides, and toe) OK? Comment: (d) building or of er setbacks(top, both sides, and toe). OK? Comment: 9. A site map drawn to scale showing the property boundaries, scale, north arrow, and the location and nature of existing and prop d development on the site. OK? Comment: Are the Documents signed and stamped? Q.-GJ By whom? type:License#: ZrJ��— Lic nse YN 7 FIRST REVIEW pproved ❑ Need more info. If not approved, what is the next action/recommendation for further action? v I `e- V Reviewed by ' , on 7i 2 Time spent in review: SECOND REVIEW/UPDATE ❑ Approved ❑ Need more info. If not approved, what is the next action/recommendation for further action? Reviewed by , on . Time spent in second review: THIRD REVIEW/UPDATE ❑ Approved ❑ Need more info. If not approved, what is the next action/recommendation for further action? Reviewed by , on . Time spent in third review: Disclaimer. Mason County does not certify the quality of the work done in this Geological Assessment Page 2 of 2 Form Effective June 2008