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20150729155400.pdf', ,r- � " .,,;rlyopy RanGEO) I N C O R P O R A T 4 O Geotechnical & Earthquake Engineering Consultants September 18, 2014 File No. 07-055.100 RECEIVED Mr. Van Caryl DEVELOPMENT SERVICES 15701— 75th Place West COUNTER Edmonds, Washington 980264521 Subject: Geotechnical Evaluation Proposed Grading 15701— 75'h Place West, Edmonds, Washington Dear Mr. Caryl: As requested, we are pleased to present this letter summarizing our geotechnical evaluation for the subject lot. This letter presents the results of our evaluation and provides our geotechnical recommendations for the proposed grading planned for the west side of the residence. We previously prepared a letter dated April 11, 2007 providing geotechnical recommendations for the construction of a patio in this same area. The patio was not constructed. In preparing this letter, we met with you on-site to observe the current site conditions, reviewed the proposed grading plans and other improvements, and reviewed background geologic and geotechnical information for the site and vicinity. Our review included published literature regarding the project site, including summary logs of previous borings and test pits in the vicinity of the site maintained by the Washington Department of Natural Resources(Ilttl s: fl l tes w r .'OV/ nr/ ,cola / Fhejn� subsurl , and the North Edmonds Subsidence and Landslide Hazard Area Summary Report, Edmonds, Washington (Landau, 2007). Our services are provided in accordance with the attached General Conditions. 3213 Eastlake Avenue East, Suite B Seattle, WA 98102 (206)262-0370 FAX (206) 262-0374 Mr. Van Caryl Geotechnical Evaluation: 15701— 75th Place West, Edmonds, WA September 18, 2014 PROJECT BACKGROUND The subject site is located at 15701 — 75th Place West in Edmonds, Washington. The site is located in a geologic province known as the Meadowdale Landslide Complex, which is an ancient landslide or paleo-slide. The subject site is situated between 75th Place West and the steep slope that defines the eastern edge of the landslide complex. This area is identified as being within Zone B of the landslide complex (Landau, 2007) which has a potential for large scale slope instability and localized small scale instability. As a result, we understand the City of Edmonds is requesting a geotechnical assessment to evaluate the potential impacts of the proposed improvements to the site stability. PROJECT DESCRIPTION The site contains an existing two story, lightly loaded wood frame residence constructed in 1973. The site and surrounding area slopes down from east to west and the residence is benched into the natural sloping grade, with the lower level comprised of a daylight basement. Plates 1 and 2 provide an overview of the site conditions. At this time it is planned to remodel the interior of the existing residence to create an accessory dwelling unit comprising the lower, daylight basement level of the residence. In order to provide access to the lower unit, it is planned to install a door at the location of a framed window opening on the west side of the residence. The door will require permanently lowering grades on the west side of the residence by excavating to a depth of two feet at the west edge of the residence. The depth of excavation will taper to match existing grade to the west. Approximately 45 cubic yards of soil will be excavated and removed from the site. 07-055.100 15701 -75th Ave W Page 2 PanGEO, Inc. Mr. Van Caryl Geotechnical Evaluation: 15701 — 75th Place West, Edmonds, WA September 18, 2014 Plate 1: View from southwest portion of site toward Plate 2: Area of yard on west side of houe where northeast. Existing residence is in the central portion grades will be lowered. Excavation will extend from of the photo. two feet deep at house tapering to match grade on right side of photo. The excavation and soil exporting is expecting to take one day to complete. A cantilevered second story deck is also planned for the west side of the residence. No new foundations are planned to support the deck. SITE RECONNAISSANCE As part of our study, we returned to the site on September 9, 2014 to conduct a reconnaissance of the site. The existing residence is situated about 90 feet east of the 75th Place West right-of-way, with the basement floor about 15 feet above the grade of 75th Place West. The grade between the residence and the street is terraced; see Plate 1 above, with an approximately 20 foot wide level lawn area immediately west of the residence. At the edge of the lawn is a 10 to 12 foot high slope with a gradient of 50 percent. At the toe of the slope is relatively level gravel parking area at the elevation of 75th Place West. East of the residence is an approximately 20 foot wide level yard area, which is bordered to the east by an approximately 40 foot high slope that ascends to the east at a 50 to 80 percent gradient. 07-055.100 15701 -75th Ave W Page 3 PanGEO, Inc. Mr. Van Caryl Geotechnical Evaluation: 15701— 75th Place West, Edmonds, WA September 18, 2014 In general, the project site and its vicinity are underlain by a sequence of glacial till, advance outwash sand and gravel, and fine-grained silt and clay. The steep topography and the presence of groundwater at the sand/gravel and the underlying silt/clay contact is often the triggering mechanism of past slides. We understand the residence was constructed in 1973. Observations made during our site visit suggest that the site has been stable at least since the residence was built, a period of 41 years. Although one minor crack was observed within the concrete stem wall on the north side of the building, the crack pattern suggests that it was caused by foundation settlement at the northwest building corner, and is not related to slope movement. Although the site appears stable at this time, and has been stable since at least 1973 when the residence was built, the potential for future ground movements cannot be dismissed because of the site geology, site topography, and the history of previous slope failures in the vicinity of the site. DISCUSSION AND RECOMMENDATIONS Because the proposed changes to the residence will result in lowering grades by as much as 2 feet and the soils will be removed from the site, in our opinion the proposed changes should not increase the potential for instability. However, the anticipated volume of soil removal (45 cubic yards) is relatively small, so the proposed grading is not expected to improve the site stability either. In summary, for all practical purposes, it is our opinion that the proposed grading should have no impacts (either positive or negative) on the long term stability of the site. The regrading should be designed such that the finished ground surface slopes away from the top of the west slope; All surface water from new impervious surfaces such as walkways should be collected and carried by way of a tightline to permanent discharge facilities. 07-055.100 15701 -75th Ave W Page 4 PanGEO, Inc. Mr. Van Caryl Geotechnical Evaluation: 15701— 75th Place West, Edmonds, WA September 18, 2014 SEASONAL GRADING RESTRICTION The City of Edmonds imposes a seasonal grading restriction on earthwork in critical areas that extends from October 1 through April 30. As the proposed earthwork will only take one day and is limited to the excavation and exporting of soils, in our opinion the earthwork can take place during the grading restriction period, provided the following mitigation measures are implemented: • The earthwork should be timed to occur during a period when there will be an extended period of predictable, dry weather. In no case should earthwork should be conducted during periods of precipitation. • The soils generated by the excavation should be loaded directly into a truck and exported. In no case should soils be temporarily stockpiled in the work area or at the top of the west slope. • After the grading is completed, the exposed surface should be covered with at least three inches of straw mulch. STATEMENT OF RISK As required by the City of Edmonds, the following Statement of Risk is made: a. Structural Plan Review: The proposed regrading does not include any structural elements. b. Increased Risk: The proposed regrading involves lowering grades in the lawn area west of the residence, reducing the weight at the top of the west slope and reducing driving forces for future instability. As a result, the proposed improvements are not anticipated to increase the risk of slope instability. Provided that proper erosion control measures are implemented during construction and surface water drainage is controlled on a permanent basis, in our opinion that the risk of damage to the property or adjacent properties as a result of the planned improvements will be minimal. However, the word "minimal" does not imply no risk. Development in a landslide or steep slope area always involves some risk. 07-055.100 15701 -75th Ave W Page 5 PanGEO, Inc. Mr. Van Caryl Geotechnical Evaluation: 15701 — 75`h Place West, Edmonds, WA September 18, 2014 c. Probability of slope movements: Based on our subjective judgment, which is in part based on the stability of the site during at least the last 41 years and the setback distance from the street and the bluff fronting Puget Sound, it is our opinion that the probability of ground subsidence at the site is less than about 10% in the next 25 years. However, it should also be noted that the site stability could also be impacted by factors beyond one's control, including extreme weather conditions and off-site construction activities. We trust the information presented herein meets your need at this time. If you have any questions, please do not hesitate to contact our office. Sincerely, PanGEO, Inc. 'M " � Me", 212 �f P0\0 Scott D. Dinkelman Scott D. Dinkelman, LEG Senior Engineering Geologist Attachment: General Conditions Siew L. Tan, P.E. Principal Geotechnical Engineer 07-055.100 15701 -75th Ave W Page 6 PanGEO, Inc. GENERAL CONDITIONS PanGEO, Inc., a Washington Corporation C PanG139% and Client agree to a work assignment in accordance with the attached proposal and cost estimate, and the following general conditions. INTEGRATION The attached proposal together with these General Conditions comprises the entire Agreement between the parties. This Agreement may not be changed without the prior written consent of all parties to the Agreement. There are no terms or conditions that are not expressed in this Agreement. STANDARD OF CARE PanGEO agrees to perform its professional services in accordance with that degree of care and skill ordinarily exercised by similarly qualified geotechnical engineering professionals currently practicing in this area under similar conditions. No warranties or other representations are expressed or implied. CLIENT FURNISHED INFORMATION AND OBLIGATIONS The Client is responsible to provide PanGEO with a description of the property, its location, and the locations of any underground utilities, facilities or structures on or adjacent to the property that could impact our work. PanGEO, its owners, employees, subcontractors and agents will not be responsible for any damage to buried utilities or subterranean structures that are not specifically identified to PanGEO. The Client also must advise PanGEO of the location and nature of any known or suspected hazardous materials that may exist on the property. SITE ACCESSIRIGHT OF ENTRY The Client agrees to advise PanGEO, prior to commencement of our services, of any special requirements for entry, work permits, security clearances, licenses, or any other required permissions. If the property is not owned by the Client, the Client shall obtain permission for right -of - entry for the purpose of performing our services. SURFACE AND SUBSURFACE DISTURBANCE PanGEO will take reasonable precautions to minimize surface and subsurface disturbance of the site. In the normal course of exploratory work some disturbance may occur, and the restoration of any disturbance is not part of this Agreement, unless specifically provided in the scope of services and budget for the work. UNANTICIPATED CONDITIONS OR HAZARDOUS MATERIALS Subsurface conditions at some locations at the site may vary from those encountered at the locations where surveys or explorations are made. Because the interpretations and recommendations of PanGEO are based solely on the information available to PanGEO, limitations on the available information will result in some uncertainty, and, therefore, risk, with respect to the interpretation of geologic and geotechnical conditions, despite the use of due professional care. If conditions different from those described in our report are observed or appear to be present, PanGEO should be retained to provide additional analyses as necessary to evaluate the situation and modify our recommendations as appropriate. The discovery of unanticipated conditions or hazardous materials constitutes a changed condition that may require renegotiation of the scope of services and budget, or termination of services. If unanticipated hazardous materials are encountered, PanGEO may take immediate action to protect health and safety. PanGEO shall notify Client as soon as practically possible should unanticipated hazardous materials be encountered. Client agrees to compensate PanGEO for the additional cost of services necessary to protect the health and safety of the public, PanGEO's employees, or others. INDEMNIFICATION FOR HAZARDOUS MATERIALS AND RELEASE OF POLLUTANTS Client agrees that any hazardous materials, including asbestos, present at the work site, prior to and during the performance of this Agreement were not generated, stored or disposed of by PanGEO. To the fullest extent permitted by law, the Client shall defend, indemnify and hold harmless PanGEO, its owners, employees, subcontractors and agents, from any and all liability, loss, costs, damage or expenses (including attorneys' fees and costs upon trial and appeal) arising out of or in connection with (1) any future pollution -related claims or damages at the site, including potential claims from third parties that may name PanGEO as a defendant, and (2) the performance of any professional services of PanGEO that result in alleged exacerbation of existing environmental pollution or contamination, or result in any newly caused or created pollution or contamination. This indemnification will not apply to claims, damages, losses or expenses which are a result of negligent acts by PanGEO under this Agreement, or which arise from new pollutants introduced solely by PanGEO. REPORTING OF HAZARDOUS SUBSTANCE RELEASES The Client is responsible for reporting releases of hazardous substances when such reports are required by government agencies. The Client agrees to defend and hold PanGEO harmless for government or third party action taken for Client's failure to comply with hazardous substance release reporting requirements. JOB SITE CONDUCT AND SAFETY PanGEO will be responsible for its professional activities on the job site. This will not relieve the Client, Owner, or construction contractors of their obligation to maintain a safe job site. Neither PanGEO's professional activities nor the presence of its employees nor subcontractors shall be construed to imply responsibility for job site safety. 07-055.100 15701 -75th Ave W Page A-1 PanGEO, Inc. SAMPLE RETENTION AND DISPOSAL Non -hazardous samples will be discarded 30 days after they are obtained unless prior arrangements are made to store or deliver the samples. Samples containing hazardous materials that are regulated under federal, state, or local environmental laws will be returned to the site. INSTRUMENTS OF SERVICE Reports, field data, laboratory data, analyses, calculations, estimates, designs and other documents prepared by PanGEO as instruments of service shall remain the property of PanGEO. PanGEO will retain pertinent records relating to the services performed for a period of ten years following submission of the report. Copies of the instruments of service will be made available to the Client on request at a reasonable fee. Reuse of any instruments of service by the Client on extensions of this project or on other projects without PanGEO's written permissions will be at the Client's sole risk. Client agrees to defend, indemnify and hold harmless PanGEO from claims, damages and expenses arising out of such reuse. BILLING AND PAYMENT Billing for services will be submitted upon completion of the geotechnical engineering report. A service charge of one and one-half percent (1.51/o) per month will be added to unpaid accounts due over 60 days. Expenses incurred in preparation and/or foreclosure of any lien or collecting delinquent amounts including, but not limited to attorneys' fees, costs at trial and appeal and charges for PanGEO's staff time shall be paid in addition to the delinquent amount. TERMINATION OF SERVICES This Agreement may be terminated by either party upon at least seven (7) days written notice in the event of substantial failure by the other party to perform in accordance with the terms and conditions through no fault of the terminating party. Such termination shall not be effective if that substantial failure has been remedied before expiration of the period specified in the written notice. In the event that the Client requests early termination of our services, PanGEO reserves the right to complete such analyses and records as are necessary to place its files in order and complete a report on the services performed to date. Charges for these termination activities shall be in addition to all charges incurred up to the date of termination. INSURANCE PanGEO maintains Workers' Compensation and Employer's Liability Insurance as required by state laws. PanGEO also maintains comprehensive general, auto, professional and environmental liability insurance, certificates of which are available upon request. LIMIT OF LIABILITY General Liability: In the performance of this Agreement and subject to the limits, terms and conditions of property damage and public liability coverage, PanGEO agrees to indemnify and hold Client harmless from PanGEO's proportional share of liability resulting from its negligence and any breech of contract compared to that of other persons or entities which results in damage to the Client. PanGEO shall not be responsible for any loss, damage, or liability beyond the amounts, limits, coverage or conditions of its insurance coverage on the date the claim is made. PanGEO shall not be responsible for Client's negligence nor the negligence of third parties. Profawsional Liability: In consideration of relative opportunities for financial reward from this project for the parties to this Agreement, Client agrees that the maximum aggregate amount of its recovery from PanGEO or its employees due to any and all claims of professional negligence and breach of contract arising out of any incident shall be limited to $50,000 or the amount of PanGEO's fees for the services provided under this Agreement, whichever is less, unless a higher limit with commensurate compensation is specifically negotiated. CONSEQUENTIAL DAMAGES PanGEO shall not be liable for consequential damages, including loss of use or loss of profits, or indirect damages, regardless of whether such claim is based upon alleged breach of contract, willful misconduct, strict liability, breach of warranty or negligent act, error or omission, whether professional or nonprofessional. DISPUTES Any dispute, controversy or claim arising out of or relating to this Agreement, or breach thereof, shall be mediated. The law of the State of Washington will govern the validity and execution of this Agreement and the disposition of any claims related to this Agreement. The prevailing party in any dispute or litigation concerning this Agreement will be entitled to recover reasonable attorneys' fees and costs incurred at trial and appeal, including staff time, court costs, attorneys' fees, and other claim -related expenses. ASSIGNMENTS Neither the Client nor PanGEO may delegate, assign, sublet or transfer the duties, interests or responsibilities set forth in this agreement without the written consent of the other party. SURVIVAL These terns and conditions shall survive the completion of the services under the Agreement and the termination of the Agreement for any cause SEVERABILITY The Client and PanGEO have entered into this Agreement of their own free will, to communicate to one another mutual understandings and responsibilities. Any element of the Agreement later held to violate a law or regulation shall be deemed void, and remaining provisions shall continue in force. Client and PanGEO shall in good faith attempt to replace any invalid or unenforceable provision with one that is valid and enforceable, and which comes as close as possible to expressing the intent of the original provision. 07-055.100 15701 -75th Ave W Page A-2 PanGEO, Inc.