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Critical Areas Study Reqd.pdfThe Critical Areas Checklist contained on -ibis form . is to be filled out by any person preparing a Development Permit Application. for the City, of Edmonds, prior to his/her submittal of the application to the City. The purpose of the Checklist is to enable City staff to determine whether any potential Ciftal Area's are,,, or may., -be,present on,thp pubj betpropert `'The inforrhation . .y needed to complete the Checklist should be easily available ftom observations of the site or data available at City Hall (Critical areas inventories, 'maps, or soil survey$). Date Received:— _C1111ty Receipt I . . . . . . . . . . . . . . . . ............ - i L A property owner, or Ms./her authorized representative, must fill out -the checklist, sign :and date it, and submit it to the City. -The Citywill review the checklist, make a precursory site visit and make adete'rm"6n of the subsequent steps necessary to complete a dev6lopm'ent permit application.. Please, subtidVa vicinity,map, along with. the signed copy of this f6nn to assist aty staff m fnding andlocating the speei.fip piece of property 'described on this form. In addition, the .applicant shall include other pertinent Information (e.g. site plan, topography map, etc.) or studies in conjunction with this Checklist to assistant staff in completing their prelimhiary assessment of the site. The undersigned applicant and his/her/its heirs, and assigns, in consideration on the processing of the application agrees to release,, had emnify,,defend and hold the City of Edmonds harmless from any and all damages, including reasonable,. attomey's fees, wising from any action or hi action based in whole or part upon false, misleading, inaccurate or incomplete Information furnished by the applicant, his/her/its agents or employees: By my signature, I certify that the information and exhibits herewith submitted are true and correct to the -best of my knowledge and that Tarn �.uthorlzed to file this application on the behalf of the owner'asilisted below. SIGNATURE Ov APPLICANVAGENT ro PC2 Propeily Owner's Authorizition By my sigripture, I cer* that I have authorized the above Applicant/Agent to apply for the subject land use application, and, grant my pernilssi6n. for the public officials and the staff of the City ofEdmonds enter the subject property for the purposes of inspection and posthIg attendant to this application. SIGNATURE OF Owner/Appli' ant: Rotary Club of.Lynnwood Name PO Box S856 Street Address Lynriwocid WA'36 856 980 City Zip Telephone:._..: _m 6 Ia'7 6 - 77 8 6 Email address-.. 1rrpeirce@,ao1.cout. Applicant Representative. Bo b Settng Name* 371.1 91st Street SE am= Everett WA9*8208 City state zip Telephones. (2G6) 399-4668 �Cmail Address:- bob@rasf_Lt_J[�.nc..c(�:)m Revised on,12118112 1'120 - Crftical*pe�,Y Checklist Page, 00 CA File No: Critical Areas Checklist Site Information (soils/topography/hydrology/vegetation) 1. Site Address/ Location:. 8116 206th Street SW Edmonds WA. 98206. 2.'* Property Tax Account Number: 0 0 614 3 0 0 0 0 3 8.0 8 t 3g®7— 3. Approximate Site Size (acres or square feet): 20,594 Square foot Or 4. Is this site currently developed? r yes; X no. If yes; how is site developed? However sewer is- on the property 5. Describe the general site topography. Check all that apply. Flat: less than 5 -feet elevation change over entire site. X Rolling: slopes on site generally less than 15% (a vertical rise of. 10 -feet over a;horizontal distance of .66 -feet). Hilly: slopes present on site of more than 15% and less than 30% (a vertical rise of 10 -feet over a horizontal distance of 33 to 66 -feet). Steep: grades of greater. than 30% present on site (a vertical rise of 10 -feet over a horizontal distance of less than 33 -feet). Other (please describe): 6. Site contains areas of year-round standing water: NO ; Approx. Depth: 7. Site contains areas of seasonal standing water: NO , ; Approx. Depth What season(s) of the year? 8. Site is in the floodway NO floodplain NO of a water course. 9. Site contains a creek or an area where water flows across the grounds surface? Flows are year®round? NO Flows are seasonal? NO (What time of year? ). 10. Site is primarily: forested Yes ; meadow ; shrubs ; mixed urban landscaped (lawn, shrubs etc) 11. Obvious wetland is present on site: NO 1. 2. 3, Plan Check dumber, if app oc Site is Zoned? SC8 mapped soil type(s)? ' -__- For City'Staff Use ...... 4, Critical Areas inventory or C.A. map indicates Critical Area on site? 5: Site within designated earth subsidence landslide hazard area? .SITE DETEI INA'TION PDYREQULREP, WAIVER Revised on 12/18/12 P20 - Critical Areas Checklist Page 2 oft rhe. 1 Sy" CITY OF EDMONDS 121 5th Avenue North, Edmonds WA 98020 Phone: 4.25.771.0220 • Fax: 425.771.0221 ® Web: www.bdmondswa.gov DEVELOPMENT SERVICES DEPARTMENT ® PLANNING DIVISION C,ritical Areas Reconnaissancei.Report Site i i During review and inspection of the subject site, it was found that the site may contain (or be adjacent to) critical areas, including Geologically Hazardous Areas (Erosion Hazard Area), pursuant to Chapters 23.40.and 23.80 of the Edmonds Community Development Code (ECDC). Cited sections of the Edmonds Community Development Code (ECDC) can be found on the City of Edmonds website at www.edmondswa.gov. The northern portion of the site slopes down (from near the end of the private drive) to the south. Portions of this slope are between 20 percent and 25 percent, according to City UDAR data. According to information from the US Natural Resources Conservation Service, soils at the site include Alderwood Gravely sandyloam(8-15 percent slopes). Due to the steepness of the slope and the type.of.scail, the site.contains and/or is: adjacentto slopes that are considered Erosion Hazard Areas (over 15 percent slope). Ile 'ActivitiesProposals Certain activities are allowed in or near critical area buffers as specified in ECDC 23.40.220. Similarly, certain development proposals may be exempt from Critical Areas requirements (ECDC 23.40.230). if you have any questions about whether your proposed development qualifies as an allowed or exempt activity, please contact a Planner for more information. This review applies to the entire subject parcel. Depending on the location and project proposed relative to the identified critical areas, certain studies and reports may be required. Please contact the Planning Division at 425.771.0220 if and when you have a specific development proposal for this site in order to discuss the various permits that will be required. Please note that tree removal on sites containing critical areas may first require a tree cutting permit, and the illegal removal of trees may result in penalties and steep fines (ECDC 18.45.070, ordinance #3528). Kevin Garrett, AICP, Planner May 13, 2014 Name, Title Signature Date Page 13 Inc. 1890 May 14, 2014 CITY OF EDMONDSDAVE EARLING MAYOR 121 5th AVENUE NORTH a EDMONDS, WA 98020 ® (425) 771-0220 ® fax (425) 771-0221 www.edmondswa.gov DEVELOPMENT SERVICES DEPARTMENT Rotary Club of Lynnwood PO Box 5856 Lynnwood, WA 98036-5856 Subject: Determination regarding Critical Areas Checklist: CRA20140043 Dear Applicant: - Enclosed please find a copy of the Critical Areas Checklist you submitted. The `DETERMINATION" reached by the City is located on the reverse side of the form (bottom of page). IT IS VERY IMPORTANT FOR YOU TO RETAIN A COPY OF THIS CRITICAL AREAS "D ETERMI NATION"• YOUR �� Please'examine this Determination for additional requirements. You may need to submit additional information such as an Environmental Checklist or Critical Areas Study. The Determination for the Critical Areas Checklist you submitted is a site-specific determination, not a project -specific determination. YOU MUST SUBMIT A_COPY OF THE CRITICAL AREAS CHECKLIST and DETERMINATION WITH Permit applications include the following: Building Permits Conditional Use Permits Subdivisions Variances Applications to the ADB" Land Use Applications Any other development permit applications. Thank you, Planning Secretary C: Bob Setting *Architectural Design Board Enclosure C:kUsers\Ross\Documents\LFNDA1CRITICAL AREAS CHECKLIST.doc ® Incorporated August 11, 1890 Sister City - Hekinan, Japan HU & ASSOCIATES, INC. Geotechnical Engineering Engineering Geology Earth science May 20, 201.4. Mr. Robert Setting Rotary Club of"Lynnwood 24005 — 74"' Avenue West Edmonds, WA 98020 Dear Mr.Setting: RECEIVED SubJect: Geotectmical Investigation Onsite Storillwater Disposal N(W 0 (1) 2014 Two Single -Family Residcn.c(-.,s DEVELOPMENI SE110 ' "ES 81 xx ---- 206"' Street SW lit li N I Ei R E(Jujonds, Washington L,&A Job No, 14 043 1N,rR0Ducr10N We understand that the development of two single- ramily residences is proposed by the Rotary Club of Lynnwood for the subJect property located at (fic above address in Fdmonds,. Washington. The development is to be accessed by extending (fic south end of an existing paved driveway off'86"' Street SW southward to the pro ' ject site, we also till dcrstand Haat onsite disposal of storm runoff collected over impervious sur laces of tile development is considered for these residences. At your request, we have completed a geotechnical investigation for file propose(I development. The pl-Wr)0se of this investigation is to characterize the SUbsurface conditions ofthe proJect site and present, our geotechnical recommendations of onsite 19213 Kenlake Place NE - Kennoore, Washington 98028 Phone (425) 483-9,134 - Fax (4-25) 486-2746 May 20, 2014 Two Residences — Rotary Club of Lynnwood L&A Job No. 14-043 Page 2 stormwater disposal for this development project. Presented in this report are our findings of the surface conditions and our recommendations of onsite storinwater disposal for the development. Our proposed scope of services for the geotechnical investigation comprises specifically the following. 1. Review geologic and soil conditions at and in the vicinity of the subject project site based on a published geologic map. 2. Explore subsurface conditions with backhoe test pits on the site to depths where an infiltratable soil stratum is encountered or to the maximum depth (about 10 feet) capable by the backhoe used in test pit excavation, whichever occurs first. 3. Conduct two in-situ infiltration tests in accordance with the procedure outlined in Appendix C — Approved Methods for Obtaining Design Infiltration Rates of the City of Edmonds Stormwater Code. 4. Prepare a written report to present our findings, conclusions, and recommendations. A geotechnical staff from our office was on site to direct the subsurface exploration program, examine the soil and geologic conditions encountered, and maintain logs of the test pits. May 20, 2014 Two Residences — Rotary Club of Lynnwood L&A Job No. 14-043 Page 3 The general location of the project site is shown on Plate I — Vicinity Map. It is situated on a gentle, westerly declining plain. As shown on Plate 2, the project site is an irregularly-shaped parcel of land, elongated in the north -south direction. It lies off the south end of a long, private, joint -use, paved driveway, and is adjoined by residential developments to its south, east and west. Within the site, the ground generally slopes down southward from its north end and westward from its cast side at about 20% to 25% grade for about 6 to 8 feet of drop, then trends from there westerly very gently. . The site is currently vacant with only a couple of storage sheds on it. It is dotted by tall mature evergreen trees with few younger deciduous trees mixed in between. The site is partly clear and graded, with a dirt driveway constructed of fill entering at its northwest corner. 0""IM13''K11117"i �21 M The Geologic Mar) of the Edmonds East and Part of the Edmonds West Quadrangles Washington, by James P. Minard, published by U. S. Geological Survey in 1983, was referenced for the geologic and soil conditions at the residence site. According to this publication, the surficial soil unit at and in the vicinity of the project site is mapped as a Vashon Till (Qv1) deposits. LILT & ASSOCIATES, INC. May 20, 2014 Two Residences — Rotary Club of Lynnwood L&A Job No. 14-043 Page 4 The geology of the Puget Sound Lowland has been modified by the advance and retreat of several glaciers in the past and subsequent deposits and erosion. The latest glacier advanced to the Puget Sound Lowland is referred to as the Vashon Stade of the Fraser Glaciation, which has occurred during the later stages of the Pleistocene Epoch and retreated from the region some 12,500 years ago. The deposits of the Vashon till soil unit were plowed directly under glacial ice during the most recent glacial period as the glacier advanced over an eroded, irregular surface of older formations and sediments. This soil unit is composed of a mixture of unsorted clay, silt, sand, gravel, and scattered cobbles and boulders. The Vashon till soil over the top two to three feet is normally weathered to a medium -dense state, and is moderately permeable and compressible. The underlying fresh till soil, commonly referred to as "hard pan", is very dense and weakly cemented. The fresh till soil possesses a compressive strength comparable to that of low-grade concrete and can remain stable on steep natural slopes or man -make cuts for a long period. It can provide excellent foundation support with little or no settlement. The fresh till deposits are of extremely low permeability and would be only allow ston-nwater to seep through very slowly. SOIL CONDITION Subsurface conditions of the project site were explored with four test pits. These test pits were excavated on May 13, 2014, with a rubber -tracked backhoe, to depths from 6.0 to 8.0 feet. The approximate locations of the test pits are shown on Plate 2 - Site and May 20, 2014 Two Residences — Rotary Club of Lynnwood L&A Job No. 14-043 Page 5 Exploration Location Plan. The test pits were located with either a tape measure or by visual reference to existing topographic features in the field and on the topographic survey map, and their locations should be considered only as accurate to the measuring method used. A geotechnical staff from our office was present during subsurface exploration, examined the soil and geologic conditions encountered, and completed logs of the test pits. Soil samples obtained from each soil layer in the test pits were visually classified in general accordance with United Soil Classification System, a copy of which is presented on Plate 3. Detailed descriptions of soil layers encountered during site exploration are presented in test pit logs on Plates 4 and 5. Loose fill of 10 inches and 2.0 feet thick were encountered by Test Pits I and 4, respectively, located on the west side and near the southwest corner of the site. The fill is underlain by a layer of relic topsoil about 1.5 to 1.7 feet thick. Test Pits 2 and 3 encountered about 10 inches of topsoil mantling the site. Under the topsoil and relic topsoil to about 4.0 to 5.5 feet deep is layer or layers of weathered soil of loose to medium -dense,, silty fine sand, with various amount of gravel and occasional cobble. The weathered soil is underlain to the depths explored by a Vashon till deposit of light -gray, very -dense, cemented, gravelly, silty fine sand with occasional cobble. May 20, 2014 Two Residences — Rotary Club of Lynnwood L&A Job No. 14-043 Page 6 Groundwater was not encountered by any of the four test pits excavated on the site. The very -dense, cemented, fresh till deposit underlying the site at shallow depth is of extremely low permeability and would only allow storinwater to seep through very slowly. In the wet winter season, stonnwater infiltrating into the more permeable surficial soils would perch on the till deposit. The amount of and the depth to the near -surface perched groundwater may fluctuate seasonally depending on precipitation, vegetation cover, site utilization, etc. It may dry up completely during the dryer summer months and accumulate and rise in the wet winter months. Landslide Hazard The site is generally gently sloped with local moderately steep slopes and is underlain at shallow depth by a very -dense till deposit. This deposit is of very -high shear strength and is highly resistant against slope failure. Therefore, the potential for deep-seated landslides to occur on the site should be minimal. Erosion Hazard The surficial fill, topsoil, and weathered soil are of low resistance against erosion, while the underlying very -dense till deposit is highly resistive against erosion. The weak surficial soils over the steeper portion of the site may be eroded if they are devoid of vegetation cover and saturated. Prolonged erosion may result in surficial mudslides in the May 20, 2014 Two Residences — Rotary Club of Lynnwood L&A Job No. 14-043 Page 7 steeper portion of the site. To mitigate such erosion hazard, vegetation outside of construction limits should be preserved and maintained. Unpaved exposed finished ground within the site resulted from construction activities should be re -seeded and re - vegetated as soon as possible. Concentrated storrawater should not be discharged uncontrolled onto the ground within or adjacent to the site. Stormwater over impervious Ii surfaces, such as roofs and paved driveway, should be captured by an underground drain line system connected to roof downspouts or by catch basins installed in the paved driveway. Water collected by these drain line systems should be tightlined to discharge into a storm sewer or suitable stormwater disposal facilities, such as infiltration trenches. The Puget Sound region is in an active seismic zone. The site is moderately steep to very gently sloped and is underlain at shallow depth by very -dense till deposits of very -high shear strength. Therefore, the potential for seismic hazards, such as landslides, liquefaction, lateral soil spreading, to occur on the site should be minimal. The proposed residences, however, should be designed for seismic forces induced by strong earthquakes. Based on the soil conditions encountered by the test pits, it is our opinion that Seismic Use Group I and id Site Class D should be used in the seismic design of the proposed residences in accordance with the 2009 International Building Code (IBC), ZZHI;11� '111� I i May 20, 2014 Two Residences — Rotary Club of Lynnwood L&A Job No. 14-043 Page 8 The site is underlain at shallow depth by very -dense cemented till soil. The installation in the gently -sloped, southwestern portion of the site should not have an adverse impact on site stability provided the recommendations in this report are fully implemented and observed. Based on the two in-situ infiltration tests conducted in the weathered soil underlying the site, infiltration trenches may be used to dispose storinwater collected over impervious surfaces of the development. 0 11301IL111,11 In-situ Infiltration Tests We performed two in-situ infiltration tests on May 13, 2014, on the gently -sloped southwest portion of the project site. The locations of the infiltration tests, IT- I and IT -2, are shown on Plate 2. The sizes of test pits were 5 ft - 10 in by 5 ft - 7 in by 2 ft - 8 in deep for IT- I and 5 ft - I in by 5 ft - 3 in by 2 ft - 9 in deep for TT -2. The soil at bottom of both infiltration test pits was a deposit of light -brown to light -gray, medium -dense, silty fine sand with trace gravel. Groundwater was not encountered by the infiltration test pits. The two in-situ infiltration tests were conducted in accordance with the procedure outlined in Appendix C — Approved Methods for Obtaining Design Infiltration Rates of the City of Edmonds Stormwater Code. The test pits were filled with water for hours initially until the amount of water infiltrating into bottom of the pits reached a steady state May 20, 2014 Two Residences — Rotary Club of Lynnwood L&A Job No. 14-043 Page 9 (i.e., the volume of water infiltrating into the ground through bottom of the pits was about the same as volume of water discharged into the pits while water in the pits was kept at a constant level). Clear tap water was used in the tests. The infiltration rates into the test pits was then determined by the constant head method with the volumes of water discharged into the pits measured with a flow meter attached to the hose conveying water from the faucet into the pits for a period of 30 minutes. The volumes of water discharged into the test pits during the 30 -minute period were measured in U.S. gallons. The volumes of water were then converted into cubic feet and divided by the bottom areas of the test pits to derive the infiltration rate in inches per hour (iph) for each infiltration test. A correction factor of 4.0 is used to come up with the design infiltration rate of the target soil layer. The results of the infiltration tests are presented as follows: * With a correction factor of 4.0. Volume of Water Elapsed Infiltration Design Test Test Pit Discharged into Test Pit Time Rate Infiltration Bottom No. Gallons Cubic Feet Hour iph Rate, iph Area 5'-10" x IT -1 58.00 6.59 0.5 4.86 1.22 51-71f 51-111 x 5'- H 51.00 5.80 0.5 5.21 1.30 j Y * With a correction factor of 4.0. May 20, 2014 Two Residences — Rotary Club of Lynnwood L&A Job No. 14-043 Page 10 Design Infiltration Rate 'The design infiltration rates of the weathered soil of silty fine sand with trace gravel, determined from the in-situ infiltration test results, with a correction factor of 4.0. to be 1.22 and 1.30 iph for IT -1 and IT -2, respectively. We recommend a design infiltration rate not to exceed 1.20 iph be used for design of the infiltration trenches to be constructed in the southwest portion of the site, near the locations of ITA and IT -2, for onsite storrnwater disposal. Emu The infiltration trenches should be installed in the vicinity of Infiltration Test IT- I and IT - 2, and should be set back at least 5 feet from property lines, 8 feet from nearby building foundations or utility trenches, and 20 feet from the top of steep slopes of 40% grade or more. The trenches should be about 3 feet deep and cut at least 6 inches into the underlying weathered soil. The soil unit at bottom of infiltration trenches should be verified by a geotechnical engineer. The stability of the trench cut banks should also be verified by a geotechnical engineer during excavation. Cut banks more than 4 feet deep should be no steeper than IHAV to maintain stability and to prevent sloughing into bottom of the trenches and contaminate the target soils. For safety, trenches should be shored by trench blocks for vertical cut banks are more 4 feet deep. The infiltration trenches should be at least 24 inches wide. The side walls of the trenches should be lined with a layer of non -woven filter fabric, such as MIRAFI 140NS. The May 20, 2014 Two Residences — Rotary Club of Lynnwood L&A Job No. 14-043 Page 11 trenches are then filled with clean washed 3/4 to 1-1/2 inch gravel or crushed rock to within about 10 inches of the finish grade. The dispersion pipes should be constructed of 4 -inch rigid PVC pipes and laid level in the gravel or crushed rock filled trenches at about 16 inches below the top of trenches. The top of the gravel or crushed rock fill should also be covered with the filter fabric liner. The remaining trenches should then be backfilled with compacted onsite clean soils. The gravel or crushed rock fill should be placed in lifts no more than 10 inches thick in loose state, with each lift compacted to a non - yielding state with a vibratory mechanical compactor. Stormwater captured over paved driveway should be routed into a catch basin equipped with an oil -water separator before being released into the infiltration trenches. The subject site is underlain at shallow depth by very -dense till deposits. These basal soils are of high shear strength and the site should be quite stable. Proper and adequate erosion mitigation and surface and groundwater drainage control are key to maintain site stability during and after completion of construction. Construction of the infiltration trenches should be in compliance with the recommendations in this report. 'f1iis report has been prepared for the specific application to this project for the exclusive use by Rotary Club of Lynnwood and its associates, representatives, consultants and contractors. We recommend that this report, in its entirety, be included in the project LIU & ASSOCIATES, INC. May 20, 2014 Two Residences — Rotary Club of Lynnwood L&A Job No. 14-043 Page 12 contract documents for the information of the prospective contractors for their estimating and bidding purposes and for compliance with the recornmendations in this report during construction. The conclusions and interpretations in this report, however, should not be construed as a warranty of the subsurface conditions. The scope of this investigation does not include services related to construction safety precautions and our recommendations are not intended to direct the contractor's methods, techniques, sequences or procedures, except as specifically described in this report for design considerations. Geotechnical construction of the subject project should be monitored and inspected by a geotechnical engineer to assure compliance with the recommendations in this report. Our recommendations and conclusions are based on the geologic and soil conditions encountered in the test pits, results of our infiltration tests, and our experience and engineering judgment. The conclusions and recommendations are professional opinions derived in a manner consistent with the level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area. No warranty, expressed or implied, is made. The actual subsurface conditions of the site may vary from those encountered by the test pits. The nature and extent of such variations may not become evident until construction starts. If variations appear then, we should be retained to re-evaluate the recornmendations of this report, and to verify or modify them in writing prior to proceeding further with the construction of the proposed development. May 20, 2014. ,rwo Residences — Rotary Club of Lynnwood L&A Job No. 14-043 Page 13 CLOSURE We are pleased to be oll'service to you on this pro.ject, Please -reel h°ee to contact Lis if you have any questions regarding this report or need further consultation. 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ST ; Et��9 ST 220TH ', ; '�`:_s r A'" °i _� a , sw w . , s Q , nl � R 22IST r 0 BIR ii f31R(Hi PL z I s r 2231F0- P1 Z RD _ €s VICINITY MAP LILT & ASSOCIATES, INC® TWO SINGLE-FAMILY RESIDENCES 01 XX - 206TH STREET SW Geotechnical Engineering •Engineering Geology • Earth Science EDMONDS, WASHINGTON JOB NO, 14-043 DATE 5/16/2014 1 PLATE 1 I r"i t8' I I ( wt„o-cao-ca�cm I I I I a I I 71 I I � 4 I i 1 \ APPURTENNtT PRIVATE FUAO PER A. F.'N0. 7RM28028 (MAINTENANCE AGREPIEN UNUER AF. NO. 9 70 2 2 4 0690) 1 �Ya(N u �: pr tta. Oi vG'#.A veil Hi I 3904 N % EnAucaxa msn*.�cn l A r iv, na mra.zefn3a S 97r3ri-w X01 !NZ11F.S11 EGRESS \U U I' U L A- - SAA R 1 Saco--"--� 0041,4000000500 N 8917'30• ,fly377.40' - ®.507 $4`i ti I� i ti I T"T y - s-sszs M N Q� •Y.� -.r 595820 :V 0 � O as i7 ry 004 4 C) ICC�-73_, , f i tip w _ •� •c»i saw \ i l �v •�. 1 OG'}i40 OGO-007-7 �. 12XOR Sq Ft i r � J�x / y / 8918'20' SITE AND EXPLORATION LOCATION PLAN LIU & ASSOCIATES, INC. TWO SINGLE-FAMILY RESIDENCES 81XX - 206TH STREET SW Geotechnical Engineering - Engineering Geology • Earth Science EDMONDS, WASHINGTON UNIFIED SOIL CLASSIFICATION SYSTEM MAJOR DIVISIONS GROUP GROUP NAME SYMBOL GRAVEL CLEAN GW WELL -GRADED GRAVEL, FINE TO COARSE GRAVEL COARSE- MORE THAN 50% OF GRAVEL GP 1 POORLY -GRADED GRAVEL GRAINED COARSE FRACTION GRAVEL WITH GM SILTY GRAVEL SOILS RETAINED ON NO, 4 SIEVE FINES GC::: CLAYEY GRAVEL SAND CLEAN SW WELL -GRADED SAND, FINE TO COARSE SAND MORE THAN 50% MORE THAN 50% OF SAND SP POORLY -GRADED SAND RETAINED ON THE COARSE FRACTION SAND WITH SM SILTY SAND NO. 200 SIEVE PASSING NO. 4 SIEVE FINES SC CLAYEY SAND FINE- SILT AND CLAY INORGANIC ML SILT GRAINED LIQUID LIMIT CL CLAY SOILS LESS THAN 50% ORGANIC OL ORGANIC SILT, ORGANIC CLAY MORE THAN 50% SILTY AND CLAY INORGANIC MH SILT OF HIGH PLASTICITY, ELASTIC SILT PASSING ON THE LIQUID LIMIT CH CLAY OF HIGH PLASTICITY, FAT CLAY NO. 200 SIEVE 50% OR MORE ORGANIC OH ORGANIC SILT, ORGANIC SILT HIGHLY ORGANIC SOILS PT PEAT AND OTHER HIGHLY ORGANIC SOILS NOTES: SOIL MOISTURE MODIFIERS: 1. FIELD CLASSIFICATION IS BASED ON VISUAL EXAMINATION DRY - ABSENCE OF MOISTURE, DUSTY, DRY TO OF SOIL IN GENERAL ACCORDANCE WITH ASTM D2488-83, THE TOUCH 2. SOIL CLASSIFICATION USING LABORATORY TESTS IS BASED SLIGHTLY MOIST - TRACE MOISTURE, NOT DUSTY ON ASTM D2487-83. MOIST - DAMP, BUT NO VISIBLE WATER 3. DESCRIPTIONS OF SOIL DENSITY OR CONSISTENCY ARE VERY MOIST - VERY DAMP, MOISTURE FELT TO THE TOUCH BASED ON INTERPRETATION OF BLOW -COUNT DATA, VISUAL WET - VISIBLE FREE WATER OR SATURATED, APPEARANCE OF SOILS, AND/OR TEST DATA. USUALLY SOIL IS OBTAINED FROM BELOW WATER TABLE LIU & ASSOCIATES, INC. UNIFIED SOIL CLASSIFICATION SYSTEM Geotechnical Engineering Engineering Geology - Earth Science PLATE 3 LIU & ASSOCIATES, INC. Geotechnical Engineering Engineering Geology August 18, 2014 Mr. Robert Setting Rotary Club of Lynnwood 24005 — '74`x' Avenue West Edmonds, WA 98020 Dear Mr. Setting: Subject: Footing Drain Discharge Two Single -Family Residences 8 1 xx — 206'h Street SW Edmonds, Washington L&A Job No. 14-043 Earth Science We previously performed a geotechnical investigation of onsite storrnwater disposal for the subject project, with our findings of the subsurface conditions of the site and our geotechnical recommendations presented in our report titled "Geotechnical Investigation, Onsite Stormwater Disposal, Two Single -Family Residences, 81xx — 206"' Street SW, Edmonds, Washington," dated May 20, 2014. The subsurface conditions of the site were explored by four backhoe test pits excavated trom. 6.0 to 8.0 feet deep. Very -dense, cemented, glacial till deposit was encountered by these test pits at depths froth 4.0 to 5.6 feet below existing ground surface. The till deposit was overlain by layers of topsoil, loose to medium -dense silty fine sand, and slightly silty fine -to -coarse sand soils. Groundwater was not encountered by any of the four test pits excavated on the site. 19213 Kenlake Place NE - Kenmore, Washington 980 Phone (425) 483-9134 - Fax (425) 486-21 August 18, 201.4 Two Residences -- Rotary Club of 1-yraiwood L&A Job No. 14-043 Page 2 Based on the subsurface condition encountered by the test pits, it is our opinion that the amount of groundwater, if any, to be collected into looting drains of the proposed residences will be insignificant. Therefore, it is our opinion that fbotilig drains discharged into drywells will be adequate and acceptable to dispose water in footing drains. Drywells should be set back at least 5 F( --,et from property lines and 8 Leet from mtjaceritl building Foundations. Drymells should be constructed of minimuni 3 -foot by 3 -Riot deep round or square pits. The pit walls Should be lined with a layer oft -ton -woven filter Eabric, such as Mirafi HONS. The pits should then bc- filled with 1-112 to 3 -Inch, (,,,]call, washed gravel to within about 9 to 10 inches offinish grade. 'The lop of the gravel fill ShOL11d also be covered with the same filter -fabric liner and topped with (.]call soil to the finish grade. Footing drains should be tightlined at mininium 7.5% grade to discharge into dry -wells. Please contact LIS if you have qLICStiOnS. Yours very truly, 1AU & ASSOCIATES, INC. Jrya (Ju ian) Liu, Ph.D., P.E. Consulting Geolechnical l",righ-Leer 1A -U & ASSOCIATES, INC.