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HomeMy WebLinkAboutLUA16-000314_Report 1DEPARTMENT OF COMML rY ---------Ren ton 8 AND ECONOMIC DEVELOPMENT DATE: PROJECT NUMBER: PROJECT NAME: PROJECT MANAGER: OWNER: CONTACT: LOCATION: DESCRIPTION: CRITICAL AREA: PLANNING DIVISION CERTIFICATE OF EXEMPTION FROM CRITICAL AREAS REGULATIONS EVALUATION FORM & DECISION June 03, 2016 LUAlG-000314 Children's Institute Tree Removal Critical Areas Exemption Angelea Weihs, Assistant Planner Carrie Fannin, Children's Institute for Learning Differences 2640 Benson Rd S Renton, WA 98055-5192 Ray Robinson, Integrated Site Design, Inc 12743 26th Ave NE Seattle, WA 98125 2640 BENSON RD S The applicant, Children's Institute for Learning Differences, is requesting approval of a Critical Areas Exemption in order to remove 11 hazardous trees and prune 4 trees on the site located at 2640 Benson Road S. The site is within the Residential-8 (R-8) Zone and is 175,111 square feet. The site is presently used as a private school. The site contains sensitive and protected slopes, high landslide hazards, moderate coalmine hazards, and high coalmine hazards within 50 feet of the site. The purpose of the tree removal is to prevent damage by hazardous trees to residents and buildings within and nearby the subject property. The applicant's original proposal was to remove a total of 62 trees on site; however, upon inspection, city arborist Terry Flatley observed that several of the trees identified for removal were not located near any buildings or streets, but in the middle of the woods. The city determined it is unnecessary to remove trees, except where they might pose a danger to adjacent property or street right-of-ways. The applicant revised their proposal to remove 11 trees and prune 4 trees. Terry Flatley concurs with the assessment of these trees and recommends removal. The proposed tree removal has been assessed by a geotechnical engineer, and the report indicates that the tree removal will not have a significant impacts on the slope/critical area stability, provided the root mass and stumps remain, and the tree removal plan include new plantings near trees 1, 2, and 3 (See Exhibit 2). Sensitive and Protected Slopes, High Landslide Hazards, Moderate and High Coal Mine Hazards Page 1 of 3 City of Renton Deportment of Commun it conomic Development Ce . rte of Exemption from Critical Areas Regulations Children's Institute Tree Removal Critical Areas Exemption WA16·000314 EXEMPTION JUSTIFICATION: Renton Municipal Code, Section 4-3-0SOC.3.c.iii. Dangerous Trees: Removal of non-native invasive ground cover or weeds listed by King County Noxious Weed Board or other government agency or dangerous trees, as defined in Chapter 4-11 RMC which have been approved by the City and certified dangerous by a licensed landscape architect, or certified arborist, selection of whom to be approved by the City based on the type of information required. Limited to cutting of dangerous trees; such hazardous trees shall be retained as large woody debris in critical areas and/or associated buffers, where feasible. FINDINGS: The proposed development is consistent with the following findings pursuant to RMC section 4-3-0SOC.2.d: DECISION: CONDITIONS: i. The activity is not prohibited by this or any other provision of the Renton Municipal Code or State or Federal law or regulation; ii. The activity will be conducted using best management practices as specified by industry standards or applicable Federal agencies or scientific principles; iii. Impacts are minimized and, where applicable, disturbed areas are immediately restored; iv. Where water body or buffer disturbance has occurred in accordance with an exemption during construction or other activities, revegetation with native vegetation shall be required; v. If a hazardous material, activity, and/or facility that is exempt pursuant to this Section has a significant or substantial potential to degrade groundwater quality, then the Administrator may require compliance with the Wellhead Protection Area requirements of this Section otherwise relevant to that hazardous material, activity, and/or facility. Such determinations will be based An exemption from the Critical Areas Regulations is hereby Approved with Conditions•. 1. Planting shall be installed per the approved planting plan (Exhibit 2) immediately following tree removal for trees 2 and 3. 2. No tree stumps shall be removed, and all trees shall be retained as large, woody debris on site. Page 2 of 3 City of Renton Department of Communi :conomic Development ( Children's Institute Tree Removal Critical Areas Exemption SIGNATURE & DATE OF DECISION : Jenn/Ye;Henning, Planning Director ~ate of Exemption from Critical Areas Regulations LUA16-000314 June 03, 2016 Date The above land use decision will become final if the decision is not appealed within the 14-day appeal period (RCW 43.21.C.075(3); WAC 197-11-680). APPEALS: An appeal of this administrative land use decision must be filed in writing together with the required fee to the City of Renton Hearing Examiner, City of Renton, 1055 South Grady Way, Renton, WA 98057, on or before 5:00 p.m., on June 17, 2016. RMC 4-8-110 governs appeals to the Hearing Examiner and additional information regarding the appeal process may be obtained from the Renton City Clerk's Office, (425) 430-6510. RECONSIDERATION: Within 14 days of the decision date, any party may request that the decision be reopened by the approval body. The approval body may modify his decision if material evidence not readily discoverable prior to the original decision is found or if he finds there was misrepresentation of fact. After review of the reconsideration request, if the approval body finds sufficient evidence to amend the original decision, there will be no further extension of the appeal period. Any person wishing to take further action must file a formal appeal within the 14-day appeal time frame. EXPIRATION: Five (5) years from the date of decision (date signed). Attachments: Site Plan, Hazard Tree Mitigation Plan Page 3 of 3 [)> [)> Hazard Trees 2 and 3 proposed for removal. See Exhibit 2 for Planting Plan. TREE INVENTORY LEGEND :tf;;,,:.~ TREE PREVIOUSLY REMOVED ~ TREE TO BE RETAINED ~ _.. TREE TO BE REMOVED [)> p-TREE TO BE PRUNED CRITICAL AREA BOUNDARY ,---i 15' CRITICAL AREA BUFFER SETBACK L __ _J ,a AREA TO BE CLEARED -FUTURE BUILDING SITE TREE INVENTORY PLAN SCALE, I" -so' Trees located off-site --·~< '-r~,.--- ' i '·1 ~1 . • ·-·.::_ :.:_ ~ --j I -:,7'c-""-"'"':~"t~;-<:._:. . .t~~~~. ·""'/ ,,_, r· -<':!-d ,;~, ·,1 THE REPORT INCLUDES A TREE Pl.AN AND INVENTORY, WHICH DOCUMENTED THE HAZARD TREE SIZE, SPECIES, CONDITION, RISK RATING, AND RECOMMENDED ACTION. THE TREES ARE IDENTIFIED l=ON SITE WITH METAL TAGS CORRESPONDING TO TREE INVENTORY NUMBERING SYSTEM. ALL TREES APPROVED FOR REMOVAL HAVE A BLUE DOT PAINTED ON THE TRUNK AND APPROVED FOR PRUNING HAVE A BLUE LETIER P PAINTED ON THE TRUNK I MEGRATEDSITEOESIG ~tj 26TH AYF. ME SEATT\.E, WA 91!112:, ?I 2D8.3fll.ll04II ~-CHILDRENS INSTITlrrE 2640 Benson Road S. Rrnton, WA lREE IN"1::NTORY PLAN NOTE: , -. -..;; ~ ; I!•-t/l>° 1 -..,.;il i ' "•,j ;,i io ' t----cq, r-. ~ ··--,} I!\ N I . 1 · 1 , ;o ii -.. -,_,,_~I =, i:i:: I Oo "' " I SEE ARBORlSTS REPORT FOR TREE INVENTORY TABLE ON L 1 0 50 100 SCALE IN FEET 150 ~ ,,..., ... ,. __ l iii.-11-11 i.iiii iiia. "'"'"" ''""""'""'"'"""''°'"'''"" ~ ~· - ~ :c 1-1 1:1::1 1-1 -I ... PLANT LIST ~ Scientific Name Common Name Deciduous T,eea Ac 2 Acer c1rc1nauxn Vine Maple Evergreen Shrubs Vo 8 Vac:imum ovatum E..ergreen Huckleberry Deciduous Shrub Cef 7 Corrus slolonilere "Arciic Fire" Hybnd Redtwig DogMXld Sa 10 Symptnoc•;ius Ground Cover Pm M, 15 200 Polystichurr-munitixn Mahoma l"Elf!ns Saowborry Swortl Fem Low Oregon Gra~ Ml"(IQAJION PLANTING Ground cover MITIGATION PLANTING Shrubs MITIGATION PLANTING Trees PL.ANTING BOUNDARY groundcover under shrubs Sl:i:e 6-8'ht 2-0> 2-Gal 2-Gal 1-Gal 1-Gal S.e_acing Note As shoWn Multi-trunk 3'o.c 3'o.c. 3'o.c 2'o.c 18" o.c. \ Full and symetrical ~--- ----- LANDSCAPE NOTES THIS Pl.AN IS~EDOli THE Bl.l1LDIOO PEA:MITTFIEE RETEITTION ?L,\N DATED JUNE 18, ?('114 W1TH TREE NOTATION PER THE AABOflEAL REPORT DATED DECEMBER 2, 2011iTHE MITIGATION Pl.ANTING IS F!£QUIFlEO RAS!;OON TI-IE GEOTECHNICAl ~ENT ANO AS DELINEATED IN THE GEOT'EC,._IC,t,I. EVALUATION OF fiAZAAll TREE REMOVAL ,iEPQRT DATED MARCM 25TH, 21l11 2. THE P-.:lSEO Pl.l<>ITINGS ME iNT'EtlOED 4S MITIGATION OF TREE REl,UNAI. NID GROUND DIST1JRIIANCE !!£SUL Tl'-IG FROM THE Tll£E REl,IOIIAI. 3. Tl1E PI..ANTIOOS SHOWN ARE REQUIRED MIIED SOLEY ON THE TREE REMOVAL ~. LOCATIONSNIIDQUANTJTIES MAY INCREASE BASED ON THE N;T\.l,\l GROUND OlsnJ-CE. -------- -----~ m >< ::c 1-1 i:,:, 1-1 -I t,J CHILDREN'S INSTITUTE I HAZARD TREE" MITIGATION PLANTING PLAN May 25, 2016 Scale: Y,6 " = 1'-0" ---- ,11, ·~ ,p, --.i -0 8 --.. --.. --.. --.. --.. 16 ~ DEPARTMENT OF COMMUN IT AND ECONOMIC DEVELOPMENT -------Renton® DATE: PROJECT NUMBER: PROJECT NAME: PROJECT MANAGER: OWNER: CONTACT: LOCATION: DESCRIPTION: CRITICAL AREA: PLANNING DIVISION CERTIFICATE OF EXEMPTION FROM CRITICAL AREAS REGULATIONS EVALUATION FORM & DECISION June 03, 2016 LUA16-000314 Children's Institute Tree Removal Critical Areas Exemption Angelea Weihs, Assistant Planner CARRIE FANNIN, CHILDREN'S INSTITUTE FOR LEARNING DIFFERENCES 2640 Benson Rd S Renton, WA 98055-5192 Ray Robinson, Integrated Site Design, Inc 12743 26th Ave NE Seattle, WA 98125 2640 BENSON RD S DATE NAME Jennifer T. Henning Vanessa Dolbee Sabrina Mirante Jennifer Cisneros Angelea Weihs The applicant, Children's Institute for Learning Differences, is requesting approval of a Critical Areas Exemption in order to remove 11 hazardous trees and prune 4 trees on the site located at 2640 Benson Road S. The site is within the Residential-8 (R-8) Zone and is 175,111 square feet. The site is presently used as a private school. The site contains sensitive and protected slopes, high landslide hazards, moderate coalmine hazards, and high coalmine hazards within SO feet of the site. The purpose of the tree removal is to prevent damage by hazardous trees to residents and buildings within and nearby the subject property. The applicant's original proposal was to remove a total of 62 trees on site; however, upon inspection, city arborist Terry Flatley observed that several ofthe trees identified for removal were not located near any buildings or streets, but in the middle of the woods. The city determined it is unnecessary to remove trees, except where they might pose a danger to adjacent property or street right-of-ways. The applicant revised their proposal to remove 11 trees and prune 4 trees. Terry Flatley concurs with the assessment of these trees and recommends removal. The proposed tree removal has been assessed by a geotechnical engineer, and the report indicates that the tree removal will not have a significant impacts on the slope/critical area stability, provided the root mass and stumps remain, and the tree removal plan include new plantings near trees 1, 2, and 3 (See Exhibit 2). Sensitive and Protected Slopes, High Landslide Hazards, Moderate and High Coal Mine Hazards Page 1 of 3 April 28, 2016 Ray Robinson Integrated Site Design, Inc. 12743 26th Avenue NE Seattle, WA 98125 SUBJECT: "On Hold" Notice Community & Economic Development Department C.E. "Chip"Vi ncent, Administrator Children's Institute Tree Removal Critical Areas Exemption LUA16·000314 Dear Mr. Robinson: The Planning Division of the City of Renton accepted the above master application for review on April 11, 2016. During our review, staff has determined that additional information is necessary in order to proceed further. The city arborist, Terry Flatley, has visited the site and reviewed the conditions of the site in relation to the arborist report. Terry Flatley observed that this is a wooded site. Several of the trees identified for removal are not located near any buildings or streets etc., but in the middle of the woods. It is unnecessary to remove trees, except where they might pose a danger to adjacent property or street right of ways. You and your client have expressed concerns for the safety of the children who are using this wooded area as a trail/recreational space. A Critical Areas Exemption is required for trails within geologic hazardous areas. We do not have record of Critical Areas Exemption issued for this purpose. Therefore, the referenced trails are not legally permitted. In order to move forward with this proposal you will need to submit a revised arborist report that identifies targets for trees proposed for removal. Trees that do not pose a danger to adjacent structures or street right of ways shall be retained, and your tree removal plan will need to be revised accordingly. The submitted geotechnical report recommended new plantings around trees 1 through 3. If these trees do pose a danger Renton City Hall • 1055 South Grady Way , Renton, Washington 98057 • rentonwa.gov • to adjacent structures or street ROWs, a planting plan will be required. If these trees do not pose a danger to nearby property/ROWs, the trees will need to be retained and, therefore, no planting plan will be required. In addition, your site plan indicates that you are proposing to remove trees that are not located on your site, but appear to be located on Fred Nelsen Middle School property. The city cannot authorize you to remove these trees without approval from the property owner. Please either remove these trees from the scope of your project, or provide a revised master application form that includes the address, parcel number, contact information, and the notarized signature of the owner (or authorized representative) of the Fred Nelsen school. At this time, your project has been placed "on hold" pending receipt of the requested information. The requested information will need to be submitted before September 1, 2016, so that we may continue the review of the above subject application. Please contact me at (425) 430-7312 lfyou have any questions. Sincerely, Angelea Weihs Assistant Planner cc: Chlldren 1s Institute for Learning Differences/ Owner(s) Ray Robinson/ Applicant City of Renton File LUA16-000314 2 il integrated site design ~ ti ro 12743 26th Av& NE §. Seattle, WA 98125 g P: 206.36::3.9049 I www.J-s-d.com Ms. Weihs, Attn: Angelea Weihs Assistant Planner City of Renton 1055 S. Grady Way Renton, WA 98057 Re: CHILD Letter of Understanding Geologic Risk 2640 Benson Road South Renton, Wa 98055 Date: 04.09.2016 As the applicant and owners representative, I am providing all the documents requested by the City of Renton Planning Department for the proposed removal of trees within the subject property as shown in the Arborists Report. Additionally, and as requested, a Geotechnical Engineer was engaged to assess the site and make recommendations regarding the tree removal as a portion of the site is identified as being within an Environmental Critical Area. Steep slope, Landslide, and Coal Mine Hazards were the specific conditions which the Geotechnical Engineers assessed. The report stated that there would be no measurable adverse impact to the site provided the recommendations were followed during tree removal. Our client and owner of the property, the CHILD institute, has been made aware of the requirements for tree removal and understands and accepts the risk of developing in an unstable area and that they will advise, in writing, any prospective purchasers of the site, or any prospective purchasers of structures or portions of structures on the site, of the unstable potential of the area. Please let me know if this letter is sufficient for compliance with the required letter of understanding. Respectfully, Ray Robinson, RLN ASLA Cc: Carrie Fannin and the Child Board of Directors Print Form · Res~t Form Sa•e Form DEPARTMENT OF COMMUNITY AND ECONOMIC DEVELOPMENT R CITYOF ~ --------enton~ Planning Division LAND USE PERMIT MASTER APPLICATION PROPERTY OWNER($) PROJECT INFORMATION NAME: Children's Institute for Learning Difference PROJECT OR DEVELOPMENT NAME: Children's Institute for Learning Differences PROJECTIADDRESS(S)/LOCATION AND ZIP CODE: ADDRESS: 2640 Benson Road S. 2640 Benson Road S. Renton, WA 98055 CITY: Renton ZIP: 98055 TELEPHONE NUMBER: (206) 232-8680 KING COUNTY ASSESSOR'S ACCOUNT NUMBER($): 2923059102 APPLICANT (if other than owner) NAME: Ray Robinson EXISTING LAND USE(S}: School {private) COMPANY (if applicable): Integrated Site Design, Inc PROPOSED LAND USE(SJ: School (private) EXISTING COMPREHENSIVE PLAN MAP DESIGNATION: ADDRESS: 12743 26th Ave NE PROPOSED COMPREHENSIVE PLAN MAP DESIGNATION CITY: Seattle ZIP: 98125 (if applicable) TELEPHONE NUMBER: (206) 363-9049 EXISTING ZONING: R-8 CONTACT PERSON PROPOSED ZONING (If applicable): NAME: Ray Robinson SITE AREA (in square feet): 175,111 SQUARE FOOTAGE OF PUBLIC ROADWAYS TO BE COMPANY (If applicable): Integrated Site Design, Inc DEDICATED: ADDRESS: 12743 26th Ave NE SQUARE FOOTAGE OF PRIVATE ACCESS EASEMENTS: PROPOSED RESIDENTIAL DENSITY IN UNITS PER NET CITY: Seattle ZIP: 98125 ACRE (If applicable) TELEPHONE NUMBER AND EMAIL ADDRESS: NUMBER OF PROPOSED LOTS (if applicable} (206) 363-9049 r.robinson@i-s-d.com NUMBER OF NEW DWELLING UNITS (If applicable): 1 H :\CED\Data \Forms-Templates\Self-H elp Handouts\Planning\Master App Ilea tion.doc Rev:08/2015 ,···,.,.-,~~y I, PROJECT INFOR)IAAT.-IO_N_~(,c_o_n_ti_nu_e_d~I) _______ -, ,-. PROJECT VALUE: NUMBER OF EXISTING DWELLING UNITS (if applicable): ! \., I SQUARE FOOTAGE OF PROPOSED RESIDENTIAL IS THE SITE LOCATED IN ANY TYPE OF BUILDINGS (if applicable}: \_. ( f ENVIRONMENTALLY CRITICAL AREA, PLEASE INCLUDE SQUARE FOOTAGE (if applicable): SQUARE FOOTAGE OF EXISTING RESIDENTIAL BUILDINGS TO REMAIN (if applicable): CJ AQUIFlER PROTECTION AREA ONE SQUARE FOOTAGE OF PROPOSED NON-RESIDENTIAL CJ AQUIFIER PROTECTION AREA TWO >-· • \· ~ \. ~- ~- t BUILDINGS (if applicable): o SQUARE FOOTAGE OF EXISTING NON-RESIDENTIAL BUILDINGS TO REMAIN (if applicable): 10,899 NET FLOOR AREA ON NON-RESIDENTIAL BUILDINGS (if applicable}: NUMBER OF EMPLOYEES TO BE EMPLOYED BY THE NEW PROJECT (if applicable}: -·--------·· ····-·---····--·-- CJ FLOOD HAZARD AREA sq. ft CJ GEOLOGIC HAZARD sq. ft. CJ HABITAT CONSERVATION sq. ft. CJ SHORELINE STREAMS & LAKES sq. ft. CJ WETLANDS sq. ft. LEGAL DESCRIPTION OF PROPERTY (Attach leaal description on separate sheet with the followina Information included) SITUATE IN THE NW QUARTER OF SECTION~. TOWNSHIP~. RANGE _s_, IN THE CITY · OF RENTON, KING COUNTY, WASHINGTON AFFIDAVIT OF OWNERSHIP I, (Print Name/s) declare under penalty of perjury und~ laws of 1ha S!Ble of Washington that I am (please check one) the current owner of the property involved in U,is application or L.l!S,I the authorized representative to act for a corporation (please attach proof of autholization) and that the foregoing statements and answe1'$ herein ·ned and th · tion herewith er In all respects true and correct to tne best of my knowledge and belief. ~-/'7-1 Date Signature of OWner/Representative Date COUNTY OF KING I cerofy that I know or have oatiofactory evidence that l'.'.?a rr/e Noa, ·a, signed this Instrument and acknowledge it to be his/her/their free and voluntary act for the uses and purpose mentioned in tna Instrument Dated -- Not11y Public S1111 ot W11hlngton ,fl<ifLI, L ~ Notary Public in and for the tateof Washington Notary {Print): . DIANE L HUTTON Mr At1Paintmtt11 Explm Nov 18, 2017 My appointment expires: -"-/.,_/,_/;.,_..g"'},."''.;:M""..,_J._.7._ ________ _ ~--... _ .. _ ...... _ ............. _ ... _,....( 2 H :\CED\Data \Forms-T emplates\Se If-Help Handouts\P!anning\Ma:ster Appll cation.doc Rev:08/2015 ' ) CRITICAL AREAS EXEMPTION Applicant Name Ray Robinson Parcel Number (FOR SEPA EXEMPT ACTIVITIES) Planning Division 1055 South Grady Way-Renton, WA 98057 Phone: 425-430-7200 Fax: 425-430-7231 Project Name Children's Institute Project Address Phone Number 206 363 9049 2923059102 2640 Benson Road 5, Renton, WA 98055 Brief Description of Project Per recommendations in the attached arborist's report, 62 dead and dying hazard trees are required to be removed and 1 is to remain and pruned to remove dead wood. The City has identified that a portion of the site contains sensitive and protected slopes, high landslide hazards, moderate coalmine hazards, and high coalmine hazards within SO feet of the site. The site has been assessed by a geotechnical engineer and the report indicates the required action of tree removal, provided the root mass and stumps remain, will not be an impact to slope stability or any coal mine related elements. All work is to prevent damage to residents and buildings within the subject property and neighboring properties by hazard trees. Type of Critical Area IZI Work Occurs in Buffer Steep Slope Work Occurs in Critical Area PURPOSE: Exempt activities provided with a letter of exemption from the Development Services Administrator may intrude into a critical area or required buffer (Subject to any conditions or requirements provided by the Administrator). APPLICABILITY OF EXEMPTIONS: The following is a general list of activities that may be exempt from the critical areas regulations. More specific descriptions of the activities are contained in the Critical Areas Regulations. Some of the listed activities may not be exempt in certain critical areas. The Planning Division will evaluate you request according to the City of Renton Critical Areas Regulations in RMC 4-3- 0SOC, J, L, and N. I AM REQUESTING A CRITICAL AREAS EXEMPTION FOR ONE OR MORE OF THE FOLLOWING ACTIVITIES: D Conservation, Enhancement, and Related Activities: • Conservation or preservation of soil, water, vegetation, fish, and other wildlife • Enhancement activities as defined in chapter 4-11 RMC D; • Any critical area, buffer restoration, or other mitigation activities that have been approved by the City D Research and Site Investigation: • Nondestructive education and research • Site investigative work necessary for land use application submittals such as surveys, soil logs, etc. F:\Projects\Commercial\Wangerin Architects\Childrens lnstitute\3 Permit\3 Critical Areas Exemption\PDFs-Completed Forms\2016-03-15\0ld\Critical Areas Exemption Short Form (2016-03-15),docx D Agricultural, Harvesting, and Vegetation Management: • Harvesting wild foods • Existing/Ongoing agricultural activities 1 • Removal of dead, terminally diseased, damaged, or dangerous ground cover or hazardous trees which have been certified as such by a forester, registered landscape architect, or certified arborist D Surface Water Alteration: • New surface water discharges provided the discharge meets the requirements of the Storm and Surface Water Drainage Regulations 1 2 3 • New or modified regional storm water facilities 12 3 • Flood hazard reduction 1 3 4 6 D Roads, Parks, Public and Private Utilities: • Relocation of Existing Utilities out of Critical Area and Buffer • Maintenance, operation, and repair of existing parks, trails, roads, facilities, and utilities 12 • Installation, construction, replacement, or operation of utilities, traffic control, and walkways within existing improved right-if-way or easement 1 2 • Modification of existing utilities and streets by 10% or less 1 2 5 • Management and essential tree removal for public or private utilities, roads and public parks 1 D Wetland Disturbance, Modification, and Removal: • Any activity in small Category 3 wetlands 1 2 3 4 5 • Temporary disturbances of a wetland due to construction activities that do not include permanent filling 1 2 3 5 D Maintenance and Construction for Existing Uses and Facilities: • Remodeling, replacing, or removing existing structures 1 2 • Normal and routine maintenance and repair of any existing public or private uses and facilities where no alteration of the critical area and required buffer or additional fill materials will be placed 1 2 • Construction activity connected with an existing single family residence or garage, provided that no portion of the new work occurs closer to the critical area or required buffers than the existing structure and/or the developed area of the site 12 • Existing activities which have not been changed, expanded or altered provided they comply with the applicable requirements of chapter 4-10 RMC 1 l2S'.J Emergency Activities: • Removal of trees or ground cover by a City department, agency, public, or private utility in an emergency situation • Public interest emergency use, storage, and handling of hazardous materials by governmental organizations in an Aquifer Protection Area F:\Projects\Commercial\Wangerin Architects\Childrens lnstitute\3 Permit\3 Critical Areas Exemption\PDFs -completed forms and\2016-03-15\Critical Areas Exemption Short Form (2016-03-15).docx ADDITIONAL PERMITS: Additional permits from other agencies may be required. It is the applicant's responsibility to obtain these other approvals. Information regarding these other requirements may be found at http://apps.ecy.wa.gov/opas/ F:\Projects\Commercial\Wangerin Architects\Childrens lnstitute\3 Permit\3 Critical Areas Exemption\PDFs -completed forms and\2016-03-15\Critical Areas Exemption Short Form (2016-03-15).docx I, the undersigned, declare under penalty of perjury under the laws of the State of Washington, that to the best of my knowledge the above information 1s true and complete. Applicant Signature: ~ _., Date: March 15th 2016 D Exemption Granted C.E. "Chip" Vincent, Planning Director Planning Division Conditions of Approval 'Exemption does not apply in Aquifer Protection Areas 'Exemption does not apply in Flood Hazard Areas 'Exemption does not apply in Geologic Hazard Areas 'Exemption does not apply in Habitat Conservation Areas 'Exemption does not apply in Streams and Lakes: Class 2 to 4 6Exemption does not apply in Wetlands D Exemption Denied Date F:\Pl"Ojects\Commercial\Wangerin Arcllitects\Childrens !nstitutt=:\3 PE"nn1t\3 Cr1trcal Areas Exernption\PDFs -completed forms and\2016-03-15\Cntical Areas Exemption Short Fann (2016-03-15).docx DEPARTMENT OF COMMUNITY AND ECONOMIC DEVELOPMENT Renton0 WAIVER OF SUBMITTAL REQUIREMENTS FOR LAND USE APPLICATIONS Planning Division 1055 South Grady Way-Renton, WA 98057 Phone: 425-430-7200 I www.rentonwa.gov LAND USE PERMIT SUBMITIAL REQUIREMENTS: WAIVED MODIFIED BY: BY: Arborist Report 4 Biological Assessment, /L5 Calculations, Colored Maps for Display , -·· Construction Mitigation Description i•••• Deed of Right-of-Way Dedication, I -~----·- Density Worksheet, .•. Drainage Control Plan 2 ( b,,. " . " Drainage Report 2 Elevations, Architectural,_, Environmental Checklist, Existing Covenants (Recorded Copy) 1 •••• Existing Easements (Recorded Copy) """' Flood Hazard Data, 1~s Floor Plans"""' Geotechnical Report 2 ANDl ' Grading Elevations & Plan, Conceptual, r I'< .. \. JC',. Grading Elevations & Plan, Detailed 2 I Habitat Data Report 4 Improvement Deferral , Irrigation Plan, COMMENTS: PROJECT NAME: Cl-\-! L]) Sc.J,,.= l Un±. frreos fixa,w.p. DATE: '). /,2.,, I I b t I 1 H :\CE D\Da ta \Fofm s-T em plates\Self-H etp H andouts\Plann!ng\ Wa Ivers ub mi tta:lrects, docx Rev; 08/2015 LAND USE PERMIT SUBMITTAL REQUIREMENTS: WAIVED MODIFIED COMMENTS: BY: BY: King County Assessor's Map Indicating Site 4 Landscape Plan, Conceptual• Landscape Plan, Detailed, Legal Description, Letter of Understanding of Geological Risk, Map of Existing Site Conditions, Master Application Fonn, Monument Cards (one per monument), Neighborhood Detail Map, Overall Plat Plan , Parking, Lot Coverage & Landscaping Analysis 4 Plan Reductions (PMTs), Post Office Approval , Plat Name Reservation , I Plat Plan 4 Preapplication Meeting Summary, I'.:-~ Public Works Approval Letter, Rehabilitation Plan , Screening Detail, Shoreline Tracking Worksheet• Site Plan ""°, Stream or Lake Study, Standard, f:;::. ~ Stream or Lake Study, Supplemental 4 Stream or Lake Mitigation Plan 4 - Street Profiles , ntle Report or Plat Certificate 1AND4 Topography Map, Traffic Study 2 Tree Cutting/Land Clearing Plan , Urban Design Regulations Analysis, Utilities Plan, Generalized 2 Wetlands Mitigation Plan, Final , Wetlands Mitigation Plan, Preliminary, H: \C£0\Data \forms-T em plates\Se lf-H elp Handouts \Plannlng\ W a Ive rs ubmittalreq5.doo; Res:08/2015 LAND USE PERMIT SUBMl1TAL REQUIREMENTS: Wetlands Report/Delineation 4 Wireless: Applicant Agreement Statement,•••• Inventory of Existing Sites ,..0 , Lease Aoreement, Draft'•""' Mao of Existing Site Conditions 2 "'"' Map of View Area••••• Photoslmulations >•••• This Requirement may be waived by: 1. Property Services 2 Development Engineering Plan Review 3 Building 4 Planning WAIVED MODIFIED BY: BY: !CS - ' 3 H: \CE D\Data \Fotms• rem plates \Self wHel p H andou ts\Plannlng\ Wa iversubm Itta !req~. dDcx COMMENTS: Rev: 08/2015 GEOTECHNICAL EVALUATION OF HAZARD TREE REMOVAL PLAN Children's Institute for Learning Differences 2640 Benson Road South Renton, Washington Project No. 1601.01 March 25, 2016 Prepared for: Children's Institute for Learning Differences Prepared by: ZGA Zipper Geo Associates, LLC Geotechnical and Environmental Consultants 19023 35th Avenue West, Suite D Lynnwood, WA 98036 Zipper Geo Associa_ s, LLC Geotechnical and Environmental Consulting Children's Institute for Learning Differences 2640 Benson Road South Renton, Washington 98055 Attention: Ms. Carrie Fannin Project Number 1601.01 March 25, 2016 Subject: Geotechnical Evaluation of Hazard Tree Removal Plan Children's Institute for Learning Differences 2640 Benson Road South Renton, Washington 98055 Dear Ms. Fannin, In accordance with your request and written authorization, Zipper Geo Associates, LLC (ZGA) has completed the subsurface exploration and geotechnical evaluation of the Hazard Tree Removal Plan prepared by others for the Children's Institute for Learning Differences (CHILD) campus located at 2640 Benson Road South in Renton, Washington. This report presents the findings of our site reconnaissance and subsurface exploration, and our geotechnical recommendations for the project. Our work was completed in general accordance with our Proposal for Geotechnical Engineering Se,vices (Proposal No. P16151) dated March 4, 2016. We appreciate the opportunity to be of service to you on this project. If you have any questions concerning this report, or if we may be of further service, please contact us. Sincerely, Zipper Geo Associates LLC James P. Georgis, L.E.G. Principal Copies: Addressee ( 1 ) Ray Robinson with Integrated Site Design, Inc. (1) 19023 36"' Avenue West, Suite D Lynnwood, WA 98036 Thomas A. Jones, P.E. Principal (425) 582-9928 TABLE OF CONTENTS INTRODUCTION ....................................................................................................................... 1 SITE DESCRIPTION .................................................................................................................. 1 PROJECT UNDERSTANDING .................................................................................................. 1 SITE RECONNAISSANCE. ........................................................................................................ 2 Southeast Tree Removal Area ............................................................................................... 2 Northeast Tree Removal Area ................................................................................................ 3 Northwest Tree Removal Area ............................................................................................... 4 Central Playground Slope Tree Removal Area ....................................................................... 4 SUBSURFACE CONDITIONS ................................................................................................... 4 Published Geologic Mapping .................................................................................................. 4 Soil Conditions ....................................................................................................................... 5 Groundwater Conditions ......................................................................................................... 6 Historic Coal Mine Maps ......................................................................................................... 6 CONCLUSIONS AND RECOMMENDATIONS ........................................................................... 7 General .................................................................................................................................. 7 Geologic Hazard ECA Considerations .................................................................................... 7 Tree Stump and Root System Retention ................................................................................ 8 Planting Recommendations .................................................................................................... 9 Temporary Erosion Control Considerations ........................................................................... 10 Retention of Woody Material ................................................................................................. 10 Off-Site Tree Removal Considerations .................................................................................. 10 General Steep Slope Considerations ..................................................................................... 10 CLOSURE ................................................................................................................................ 11 FIGURES PREPARED BY ZGA Figure 1 -Vicinity Map Figure 2 -Site and Exploration Plan FIGURES PREPARED BY OTHERS Tree Inventory Plan, Sheet L 1.1 Tree Inventory Table, Sheet L 1.2 APPENDICES Appendix A -Subsurface Exploration Procedures and Logs GEOTECHNICAL EVALUATION OF HAZARD TREE REMOVAL PLAN CHILDREN'S INSTITUTE FOR LEARNING DIFFERENCES 2640 BENSON ROAD SOUTH RENTON, WASHINGTON Project No. 1601.01 March 25, 2016 INTRODUCTION This report documents the surface and subsurface conditions encountered at the site and our geotechnical evaluation of the Hazard Tree Removal Plan prepared by others for the Children's Institute for Learning Differences (CHILD) campus located at 2640 Benson Road South in Renton, Washington. The project description, site conditions, and our geotechnical conclusions and recommendations are presented in the text of this report. Supporting data including detailed exploration logs, field exploration procedures, and other supporting information are presented as appendices. Our geotechnical scope of services for the project included a document review, site reconnaissance, subsurface evaluation, geotechnical analysis, and preparation of this report. The subsurface evaluation consisted of completing four hand auger explorations (designated HA-1 through HA-4) located near proposed tree removal areas and steep slopes. The hand auger explorations extended approximately 3Y:. to 6 feet below the existing ground surface. SITE DESCRIPTION The site is located at 2640 Benson Road South in Renton, Washington. The CHILD facility is located in the south-central portion of the site and includes campus buildings and a perimeter access drive with a parking lot on the east side of the facility. The northern portion of the site is undeveloped and includes mixed evergreen and deciduous trees with a moderately well- developed understory of brush and groundcover. The site is bounded to the north by a multi- family residential development, to the south by South 27,,, Street, to the east Benson Road South, and to the west by a middle school. The approximate site location is shown on the enclosed Vicinity Map, Figure 1. Existing site features, site topography, and nearby features are shown on the enclosed Site and Exploration Plan, Figure 2. PROJECT UNDERSTANDING The site is mapped by the City of Renton as containing Coal Mine Hazard, Steep Slope Hazard, and Landslide Hazard Environmental Critical Areas (ECAs). We understand that the City has requested a geotechnical evaluation of the Hazard Tree Removal Plan be completed to assess the risk to regulated Geologic Hazard ECAs and their associated buffers, as defined in Part 4-3- 050-G-5 of the City of Renton Municipal Code (RMC) that may result from the planned tree removal and provide recommendations to mitigate identified risks. Our understanding of the project is primarily based on a review of the following documents and discussions with Integrated Site Design and representatives for CHILD. Zipper Geo Ass, ates, LLC Children's Institute for Learning Differences Project No. 1601.01 March 25, 2016 • Tree Risk Assessment, CHILD, 2640 Benson Road South, Renton, Washington, prepared by Greenforest Incorporated Consulting Arborist, dated December 2, 2015. • Children's Institute, 2640 Benson Road South, Renton WA, Tree Inventory Plan, Sheet L 1.1, prepared by Integrated Site Design, dated March 24, 2016. • Children's Institute, 2640 Benson Road South, Renton WA, Tree Inventory Table, Sheet L 1.2, prepared by Integrated Site Design, dated March 24, 2016. Based on our review of the referenced documents, it appears that the hazard tree removal plan includes the pruning and removal of trees located within the CHILD property, and to a lesser extent, the removal of trees from the adjacent property to the east. A summary of the planned tree removal is presented below. On-Site Hazard Tree Removal: The plan identifies fifty-two trees on the site that have been rated by Greenforest Incorporated as having a moderate to high risk rating. Fifty of these trees are listed for removal and two are listed for pruning or deadwood removal. Of the fifty-two identified trees, forty-six trees are maple, five trees are cottonwood, and one tree is alpine fir. About thirty six of the fifty-two trees are located within ECA areas or their buffers as shown on Plan Sheet L 1.1 Off-Site Hazard Tree Removal: The plan identifies eleven trees east of the mapped site property line that have been rated by Greenforest Incorporated as having a moderate to high risk rating and listed for removal. Off the eleven identified trees, two trees are maple, eight trees are willow, and one tree is cherry. About ten of the eleven trees are located within ECA areas or their buffers as shown on Plan Sheet L 1.1 Copies of the Tree Inventory Plan and Tree Inventory Table (Plan Sheets L 1.1 and 1.2) are enclosed with this report without modification to assist in report interpretation. SITE RECONNAISSANCE We completed a reconnaissance of the property and immediate vicinity during a site visit completed on March 16, 2016. The purpose of the reconnaissance was to identify surficial features of site conditions such as the presence or absence of groundwater seepage, the presence or absence of surface erosion, indications of past slope instability, indications of past land use, the type and extent of existing vegetation, the location of trees identified for removal, and other site features that may be affected by the planned tree removal. The enclosed Site and Exploration Plan, Figure 2, shows the approximate location of some of the observed site features. A summary of our site observations is presented below. Southeast Tree Removal Area About 10 trees are listed for removal in this area. The trees are located within a west-facing, off- site slope that extends down to a relatively new rockery wall constructed just within the property Page 2 Zipper Geo Associate .LC Children's Institute for Leaming Differences Project No. 1601.01 March 25, 2016 line. Based on the topographic site plan, the slope inclination above the rockery ranges from about 23 to 44 percent (13 to 23 degrees). The rockery appears to be in good condition, ranges from about 4 to 6 feet tall, includes a drainage zone of quarry spall backfill, and appears to include a perforated drain pipe. In addition to the listed trees, slope vegetation includes dense Laurel bushes, blackbeny, fern, ivy, blue star creeper, and grasses. We did not observe any obvious indications of past slope movement or distress. Surficial erosion was slight and limited to several foot paths. We did not observe any obvious indications of groundwater seepage from the exposed slope surface. However, the rockery drain pipe daylights at the north end of the wall and we observed about Y. to 1 gpm discharge from this pipe at the time of our site visit. The discharge flowed down a roadside ditch to a dispersion area in the northwest portion of the site. The approximate rockery groundwater discharge location and subsequent down-gradient surface water flow is shown on Figure 2. Northeast Tree Removal Area For the purposes of this report, the northeast tree removal area includes the central steep slope area located in the northern portion of the site and the gently sloping bench located between the central steep slope area and the east property line. The north-central, west-facing slope has inclinations ranging from about 23 to 44 percent (13 to 23 degrees). In addition to the trees listed for removal, slope vegetation includes mixed evergreen and deciduous trees which were considered by the arborist to be of low risk and are not listed for removal, blackbeny, fern, ivy, and grasses. Areas between vegetation were typically mantled by several inches of forest duff. We did not observe any obvious indications of past slope movement or distress. Surficial erosion was slight and limited to several foot paths. We did not observe any obvious indications of groundwater seepage from the exposed slope surface. We observed what appears to be a lobe of fill soils extending into the slope area from the eastern bench area. The fill appeared to be relatively old and may have been associating with mass grading for the CHILD development. The approximate location of the fill is shown on Figure 2. The bench area located between the north-central steep slope and the east property line slopes gently west with inclinations ranging from about 5 to 12 percent (3 to 8 degrees). We estimate that about 60 to 70 percent on the bench is surfaced with wood chips. The remainder of the area consists of soil with scattered ferns and grass. We did not observe any obvious indications of past slope movement or distress associate with the bench or adjacent slopes. Surficial erosion was slight and limited to several foot paths. We observed slight surface water flow in the northern portion of the bench area. The flow appeared to be originating from a spring located near the top of the steep off-site slope which extends up to the adjacent middle school play field. We visually estimated a flow rate on the order of Y. gallon per minute at the time of our evaluation. The spring had incised a small drainage feature about two feet wide and one foot deep into the surface of the off-site slope. Surface water from the spring was infiltrating into the bench soils at the time of our evaluation and was not running down the north-central steep slope. The approximate location of the spring and down-gradient surface water flow is shown on Figure 2 Page3 Zipper Geo Ass ates. LLC Children's Institute for Learning Differences Project No. 1601 .01 March 25, 2016 Northwest Tree Removal Area For the purposed of this report, the northwest tree removal area includes the north-central gently sloping bench area located in the northern portion of the site and the steep slope area located between the north-central gently sloping bench area and the west property line. The north-central bench area slopes gently west with inclinations ranging from about 1 O to 17 percent (6 to 10 degrees). In addition to the trees listed for removal, vegetation includes mixed evergreen and deciduous trees which were considered by the arborist to be of low risk and are not listed for removal, blackberry, fern, ivy, and grasses. Areas between vegetation were typically mantled by several inches of forest duff. We did not observe any obvious indications of past slope movement or distress. Surficial erosion was slight and limited to several foot paths. We did not observe any obvious indications of groundwater seepage. The west-facing slope located between the north-central bench and the west property line has typical inclinations ranging from about 30 to 56 percent (17 to 30 degrees). An isolated section of slope adjacent to the sidewalk has an inclination of about 100 percent (45 degrees) with a maximum slope height of about 6 feet, and appears to be the result of a cut completed to construct the sidewalk. In addition to the trees listed for removal, slope vegetation includes mixed evergreen and deciduous trees which were considered by the arborist to be of low risk and are not listed for removal, blackberry, fem, ivy, and grasses. Areas between vegetation were typically mantled by several inches of forest duff. We did not observe any obvious indications of past slope movement or distress. Surficial erosion was slight and limited to several foot paths. We did not observe any obvious indications of groundwater seepage, but standing water was present in two drainage ditches located near the west property line at the time of our evaluation Central Playground Slope Tree Removal Area A steep west-facing slope is located near the middle of the site between the playground and the main parking lot. Slope inclinations range from about 42 to 80 percent (23 to 39 degrees). Slope vegetation primarily consists of ivy and blackberry brush, with scattered patches of grass in the southern portions of the slope and several deciduous trees. In general, the trees located on the slope exhibited pistol-butted growth pattern (bent trunks near the ground surface) which is indicative of slope creep. We did not observe indications of deep-seated slope movement or shallow sloughing. Surficial erosion was slight and limited to non-vegetated portions of the slope. We did not observe any obvious indications of groundwater seepage. SUBSURFACE CONDITIONS Published Geologic Mapping We assessed the geologic setting of the site and surrounding vicinity by reviewing The Geologic Map of the Renton Quadrangle, King County, Washington, U.S. Geological Survey Map GQ-405, Page4 Zipper Geo AssoclateALc Children's Institute for Leaming Differences Project No. 1601.01 March 25, 2016 1965. The geologic map indicates the site and immediate vicinity are mantled by Quaternary Ground Moraine deposits (Qg1). This deposit is described as thin glacial ablation till over lodgment till deposited by the Vashon Stade of the Frasier glaciation. The lodgment till is further described as a compact, unsorted mixture of sand, silt, clay, and gravel, commonly termed "hardpan". The ablation till is described as being compositionally similar to lodgment till, but much less dense. Tertiary age Renton Formation deposits are mapped about Y. mile to the northeast of the site. The Renton formation is described as arkosic sandstone, mudstone, and shale with several beds of coal. The Renton Formation has an extensive history of surface and subsurface coal mining. Stratigraphic information presented in the referenced geologic map indicates that Renton Formation deposits underlie the surficial glacial deposits at an unspecified depth. Soil Conditions The subsurface exploration for this project included four hand auger explorations (HA-1 through HA-4) located near proposed tree removal areas and steep site slopes. The hand auger explorations extended approximately 3Y. to 6 feet below the existing ground surface. The approximate exploration locations are shown on the enclosed Site and Exploration Plan, Figure 2. Soils were visually classified in general accordance with the Unified Soil Classification System. Detailed, descriptive logs of the subsurface explorations and the procedures utilized in the subsurface exploration program are presented in Appendix A. Generalized descriptions of subsurface soil conditions observed at the exploration locations are presented below. The stratification and horizontal extent of the soil types observed in our explorations may vary between explorations. Stratification boundaries on the exploration logs represent the approximate depth of changes in soil types, although the transition between materials may have been gradual. Please refer to the hand auger logs in Appendix A for a more detailed description of the conditions encountered at the exploration locations. Hand augers HA-1 and HA-2 were completed in the northern portion of the site. In general, the explorations encountered about 7 to 10 inches of loose, organic-rich silty sand interpreted as topsoil. Below the topsoil, loose to medium dense silty sand with some gravel was encountered to a depth of about 2% to 3 feet and is interpreted as weathered glacial till. Dense, silty sand with some gravel, interpreted as unweathered glacial till, was encountered below the weathered horizon and extended to the total depth explored of 3Y. feet below existing grade. Hand augers HA-3 and HA-4 were completed in the west-central and central portions of the site, respectively. These explorations encountered about 12 inches of loose organic-rich silty sand topsoil over primarily granular deposits interpreted as glacial outwash. In hand auger HA-3, the outwash consisted of medium dense sand with some gravel and silt which extended to the total depth explored of 3.5 feet below existing grade. In hand auger HA-4, the outwash consisted of medium dense fine Pages Zipper Geo Ass• 11tes, LLC Children's Institute for Learning Differences Project No. 1601.01 March 25, 2016 to medium sand with some silt which extended to the total depth explored of 6 feet below existing grade. Groundwater Conditions Slight groundwater seepage was observed in hand auger HA-2. Groundwater seepage was not observed in the other hand auger explorations. The groundwater observed in HA-2 is interpreted to represent water perched above lower permeability glacial till soils encountered at a depth of 3 feet. Given the relatively low permeability of the glacial till soils encountered in the northern portion of the site, perched groundwater may develop above the till or within sandy zones within the till during periods of extended wet weather. Perched groundwater may also develop above lower permeability layers within the glacial outwash deposits, which are often stratified. These observations represent groundwater conditions at the time of the field exploration. Groundwater conditions should be expected to fluctuate due to changes in season, precipitation patterns, site utilization, on-site or off-site irrigation activities, and other on-and off-site factors. Historic Coal Mine Maps As part of our site evaluation, we completed a review of historic coal mine maps available from the Washington State Department of Natural Resources. Based on our review, it appears that the site is underlain by portions of the Sunbeam Mine and Renton Mine. A summary of our historic coal mine map review relative to these mines is presented below. Sunbeam Mine: The Sunbeam Mine was operated by the Renton Coal Company from 1922 to 1929. The Sunbeam portal (or mine entrance) is mapped about 2/3 of a mile north-northwest of the CHILD site and has a reported main "water level" gangway elevation of about 68 feet. The mine chutes appear to have extended up and to the south-southwest of the main gangway (away from the CHILD site) along a coal seam inclined or dipping to the north-northeast at an angle of about 65 degrees from horizontal. Based on the mapped data, it appears that the Sunbeam mine workings are primarily west of the CHILD site, with the eastern end of the mine underlying a portion of Benson Road South and the southwestern portion of the CHILD site. Given a site ground surface elevation of about 400 feet, it appears that those portions of the mine workings located below or near the CHILD site are on the order of 200 to 300 feet below the ground surface. The City of Renton has mapped the mine workings west-southwest of the site (west of Benson Road South) as having a moderate to high risk, and the workings mapped below the CHILD site as having a moderate risk. Renton Mine: The Renton Mine was operated by the Seattle Electric Company in 1919 and the Renton Coal Company from 1920 to 1955. It appears that the Renton Mine 61" Gangway South and associated workings extended below the CHILD site. The historic maps do not include explicit information regarding the elevation of the workings in this area. However, the workings appear to be an extension of the generally north-northeast dipping coal seam worked in the Sunbeam Mine. Page 6 Zipper Geo Assoclate1 .LC Children's Institute for Learning Differences Project No. 1601.01 March 25, 2016 Based on the elevation of the Sunbeam main water level gangway and the indicated strata dip angle and orientation, it appears that the Renton Mine workings in the vicinity of the site are likely greater than 300 feet below the ground surface. The City of Renton has mapped the Renton Mine workings at the project site and nearby vicinity as having a moderate risk. CONCLUSIONS AND RECOMMENDATIONS General Based on the results of our site reconnaissance, document review, subsurface exploration, and geotechnical analysis, it is our opinion that the proposed tree removal plan is feasible from a geotechnical perspective. Provided that the conditions and recommendations contained within this report and the provisions of the Renton Municipal Code (RMC) are satisfied, it is our opinion that the proposed Hazard Tree Removal Plan will not increase the potential for soil movement and the risk of damage to existing structures, the site, and to adjacent properties from soil instability will not be increased. The following sections provide a discussion regarding City of Renton regulated ECAs and recommendations to reduce risks associated with the tree removal plan. Geologic Hazard ECA Considerations The site is mapped by the City of Renton as containing Coal Mine Hazard, Steep Slope Hazard, and Landslide Hazard Environmental Critical Areas (ECAs). We understand that the City has requested a geotechnical evaluation of the Hazard Tree Removal Plan to assess the risk to regulated Geologic Hazard ECAs and their associated buffers, as defined in Part 4-3-050-G-5 of the City of Renton Municipal Code (RMC) that may result from the planned tree removal and provide recommendations to mitigate identified risks. Part 4-3-050-C-3 of the RMC indicates that the removal of dangerous trees which have been approved by the City and certified dangerous by a licensed landscape architect or certified arborist is exempt from RMC ECA restrictions and may be permitted by the City. The following sections present our evaluation of Coal Mine Hazard, Steep Slope Hazard, and Landslide Hazard ECA's relative to the Hazard Tree Removal Plan. Coal Mine Hazard Areas: Coal Mine Hazard Areas include areas with known subsurface coal mine workings. The site is mapped within a Medium Coal Mine Hazard Risk Area and slightly northeast of a High Coal Mine Hazard Risk Area. Our review of historic coal mine maps for the site vicinity (Renton Mine and Sunbeam Mine) indicate mine workings depths in excess of 200 feet. Based on our document review and site observations, it is our opinion that the site are consistent with the criteria for a Medium Coal Mine Hazard Risk Area. Steep Slope Hazard Areas: The City of Renton maps portions of the site as Steep Slope Hazard Areas. The City mapped hazard areas are primarily located along the eastern property line, within the northern, undeveloped, wooded portion of the site, and the slope area between the main school building and the playground area. The enclosed Tree Inventory Plan, Sheet L 1.1 identifies Steep Page? Zipper Geo Ass1 ates. LLC Children's Institute for Learning Differences Project No. 1601.01 March 25, 2016 Slope Hazard Areas and an associated 15 foot wide buffer based on site topography. Based on our document review and site reconnaissance, it is our opinion that the critical areas and associated buffers presented on Sheet L 1.1 are in general accordance with RMC Steep Slope Hazard Area criteria. Landslide Hazard Areas: The City of Renton ECA maps generally identify the central and western portions of the northern, undeveloped, wooded area and the slope between the playground and the school facility as High Landslide Hazard Areas, although the City mapped hazard areas to not appear to correlate well to the site specific topography presented on Sheet L 1.1. This may be due to the City's use of a more regional topographic database to identify hazard area. The RMC defines a high landslide hazard area as an area with slopes greater than 40 percent, and areas with slopes between fifteen and forty percent and underlain by soils consisting largely of silt and clay. Based on our document review and subsurface explorations, it is our opinion that site slopes exceeding forty percent are consistent with the RMC criteria for Landslide Hazard Areas. These areas are generally identified on the Tree Inventory Plan, sheet 1.1. Risk Evaluation Summary: Based on mapped mine working depths in excess of 200 feet below existing grade, it is our opinion that the Hazard Tree Removal Plan will have no measurable adverse impact on the Coal Mine Hazard and will not increase the risk of coal mine induced damage to the subject site or adjacent properties. Provided that the conditions and recommendations contained within this report and the provisions of the Renton Municipal Code (RMC) are satisfied, it is our opinion that the proposed Hazard Tree Removal Plan will not increase the potential for soil movement and the risk of damage to existing structures, the site, and to adjacent properties from soil instability will not be increased. Tree Stump and Root System Retention Tree root systems provide erosion protection and bio-reinforcement for slope soils, thereby increasing the strength of the soil mass and reducing the risk of slope instability. However, the weight of the tree can increase the forces tending to drive slope instability and the rocking action of the root mass during high winds can result in loosening of the slope soils, resulting in a reduction in slope stability, particularly for large, heavy trees located on or near the crest of steep slopes. There is some debate in the scientific community regarding the relative contributions of these different factors to slope stability, but the general consensus appears to be that under most conditions the presence of trees (in particular the bio-reinforcement they provide) results in a net improvement to slope stability. Based on our review of the Tree Inventory Table, it appears that about 61 of the 63 trees listed for removal or pruning consist of cottonwood, maple, or willow. These tree species often survive cutting by generating new growth from the stump, often referred to as stump sprouting. Stump sprouts provide nourishment for maintenance of the root system while greatly reducing the negative impact of tree weight and wind driven soil loosening. We therefore recommend that the trees planned for removal be cut off near the ground surface and that the stumps and root masses Page 8 Zipper Geo AssoclateALc Children's Institute for Learning Differences Project No. 1601.01 March 25, 2016 be left in place within the Steep Slope Hazard Areas and associated buffers identified on Sheet L 1.1. We anticipate that there may be some benefit to potential utilization of the site by removing stumps from the gently sloping bench areas located in the northern portion of the site. In our opinion, the removal of stumps within the bench areas is feasible from a geotechnical perspective without adversely affecting the site slopes. An 8-inch diameter alpine fir (tree #4) is listed for removal from a grass lawn area near the perimeter access drive. In our opinion, the stump of this tree may also be removed to facilitate landscape maintenance without adversely affecting the site slopes. Planting Recommendations Some portion of the cut trees may not develop stump sprouts or may not receive adequate nutrients from the sprouts to prevent decay of the root mass over time. Based on our evaluation of the site conditions, it is our opinion that the decay of the root systems associated with trees 1 through 3 located near the top of the steep central slope adjacent to the playground could result in a reduction in the stability of the slope near the removed trees relative to shallow surficial sliding. In our experience, it typically takes about 3 to 5 years to realize a significant reduction in the bio- reinforcement provided by a tree that does not survive cutting. As a precautionary measure, we recommend that the Hazard Tree Removal Plan include new plantings near trees 1 through 3. We recommend that native woody shrubs or small trees be considered to reduce the need for watering and keep the weight and wind loading characteristics of the new growth to reasonable levels as it matures. The following table provides some plant species that could be considered to reduce the potential for erosion and increase resistance to shallow surficial sloughing. The information presented below is a relatively small sampling of plant species discussed in the 1993 publication Slope Stabilization and Erosion Control using Vegetation, produced by the Washington State Department of Ecology (Publication 93-30). The table below is by no means intended to be comprehensive or restrictive relative to the selection of appropriate plantings. POTENTIAL PLANT SELECTION GUIDE Plant Name Form& Habit Mature Rooting Recommended Size Characteristics Spacing Snowberry Evergreen shrub; Height: 4' Fibrous, (Symphoricarpos Albus) spreads by runners to Spread: 3' Shallow depth. 2'+ form thicket Sala! Evergreen shrub; Height: 3' Fibrous, (Gaultheria Sha/Ion) spreads by runners to Spread: 3' Shallow depth. 2'+ form thicket Evergreen Huckleberry Evergreen shrub; does Height: 6' Fibrous, 3'+ Oemleria Cerasiformisl not spread Spread: 3' Shallow depth. Ocean Spray Deciduous shrub; does Height: 10'+ Fibrous, (Holodiscus Discolor) not always spread Spread: 6' Moderate depth. 4'+ aaaressivelv Page9 Zipper Geo Ass ates. LLC Children's Institute for Leaming Differences Project No. 1601.01 March 25, 2016 Vine Maple Deciduous shrub; does (Acer Circinatum) not always spread annressivelv Hooker Willow Deciduous shrub; does (Salix Hookeriana) not spread • Height: 15'+ Fibrous, Spread: 10' Moderate depth. 8'+ Height: 20'+ Fibrous, 3'+ Soread: 15' Moderate deoth. Reference: Slope Stabilization and Erosion Control using Vegetation, Washington State Department of Ecolnav Publication 93-30, 1993. Temporary Erosion Control Considerations We anticipate that the tree removal process will likely result in disturbance of the ground surface and a temporary increase in the potential for erosion. We therefore recommend that the tree removal service utilize means and methods intended to minimize ground disturbance. In addition, we recommend that soils exposed within Steep Slope Hazard Areas and their buffers be covered with a temporary erosion control material, such as sterile straw or arborist mulch. Retention of Woody Material In our opinion it appears geotechnically feasible to retain much of the woody debris generated from the hazard tree removal as habitat enhancement within wooded portions of the site. However, based on our evaluation, we recommend that woody material greater than 6-inches in diameter be removed from the following areas as the weight of the material could adversely affect steep slopes or the performance of existing drainage features. • The drainage features near Benson Road South and adjacent steep slopes identified on Figure 2. • The steep slope located between the playground and the school facility and the 15-foot wide buffer above this steep slope area. Off-Site Tree Removal Considerations The Hazard Tree Removal Plan appears to include the removal of 11 trees located beyond (east of) the subject property. We recommend that all agreements and/or permits that may be needed to complete off site work be coordinated with the adjacent property owner and the City before beginning work. General Steep Slope Considerations Owners of properties containing or adjacent to steep slopes should recognize that soil loss or downslope displacement from steep slopes is a naturally occurring mass wasting process, and that some soil loss from steep slopes should be expected over time, particularly in response to episodic severe storm events. The conclusions and recommendations presented in this report are intended to allow for the removal of hazard trees while maintaining the existing stability of the site slopes. The findings presented in this report should not be interpreted as indicating that the site steep slopes will be stable under all possible future conditions. Page 10 Zipper Geo AssoclateA.Lc Children's Institute for Learning Differences Project No. 1601.01 March 25, 2016 CLOSURE The analysis and recommendations presented in this report are based, in part, on the explorations completed for this study. The number, location, and depth of the explorations were completed within the constraints of budget and site access so as to yield the information to formulate our recommendations. This report has been prepared for the exclusive use of The Children's Institute for Learning Differences, Integrated Site Design, and their agents, for specific application to this project and has been prepared in accordance with generally accepted geotechnical engineering practices. No warranties, express or implied, are intended or made. Site safety is the responsibility of others. In the event that changes in the nature, design, or location of the tree removal as outlined in this report are planned, the conclusions and recommendations contained in this report shall not be considered valid unless Zipper Geo Associates, LLC reviews the changes and either verifies or modifies the conclusions of this report in writing. Page 11 REFERENCE: GOOGLE EARTH 2016 . NOT TO SCALE CHILDREN'S INSTITUTE FOR LEARN ING DIFFERENCES 2640 Benson Road South Ren ton, Washington VICINITY MAP DATE: March 2016 Job No. 1601.01 Zipper Geo Associates, LLC FIGURE 1 19023 36th Ave. W.,Suite D Lynnwood, WA SH T. 1 of 1 GROUNDWATER SEEPAGE NE.AA FENCE LINE W •=• TREE PREVIOUSLY REMOVED ~TREE.1998 ~ TREE TO BE RETAINED -TREE TO BE REMOVED D CRITICAL AREA BOUNDARY ,--, 15' CRJTJCAL AREA BUFFER SETBACK AREA TO BE CLEARED FUTURE BUILDING SITE TREE INVENTORY PLA N SCA LE: 1" = so· ·-, ~ ~ -,~ ~ i.:::_ CONSULTING ARBORISTS FOR THE CHILO INSTITUTE DATED DECEMBER 2. 201S. THE REPORT INCLUDED A GENERAL PLAN ANO TREE lNVENTORY. WH1CH DOCUMENTED THE HAZARD TREE S IZE. SPECIES. CONDITION. RISK RATING. ANO RECOMMENDED ACTION. THE TREES HAVE BEEN IDENTIFIED ON SITE ANO TAGGED BY NUMBER WHICH CORRESPONDS WITH THE TREE INVENTORY. ALL TREES THAT THE ARBORIST SURVEYED ANO TAGGED IN THE FIELD ARE RECOMMENDED FOR REMOVAL. I ...... ~ .. ..-"' tV'32ffiA\( C 10ins. ~-2S ~--Dll1.~c:OIII CHILORENS INSTITUTE 26~0 Benson Rood S. Renton WA TRE( JNl,{Nl0RY Pl.AN NOTE , SEE ARBOR1srs REPORT FOR TREE INVENTORY TABLE ON L 1·2 0 ~50 100 SCALE IN FEET LEGEND S HA-1 ,Y --- 150 I "'°" ~,!!! HAND A UGER NU MBER A ND APPROXIMA TE LOCATION APPROXIMA TE LOCA TION OF GROUNDWATER SEEPAGE APPROXIMA TE LOCA TIO N OF S URFACE WATER FLOW CHILDREN'S INSTITUTE FOR LEARNING DIFERENCES 264-0 Benson Road South Renton. Washington SITE AND EXPLORATION PLAN DATE: March 2()16 Job No. 1601.01 Zipper Geo Assoc/1fH , UC FIGURE 19023 36th Ave. W .. Su,te D 2 Lynnwood, WA SHT.1 ol 1 ~ ,nng TREE PREVIOUSLY REMOVED ~TREE#1998 ~ TREE TO BE RETAINED ~ TREE TO BE REMOVED ~ CRITICAL AREA BOUNDARY r---, L __ _J Wf?d~ ~gr~ 15' CRITICAL AREA BUFFER SETBACK AREA TO BE CLEARED FUTURE BUILDING SITE E) TREE INVENTORY PLAN SCALE: 1" -50' THE REPORT INCLUDED A GENERAL PLAN AND TREE INVENTORY, WHICH DOCUMENTED THE HAZARD TREE SIZE, SPECIES, CONDITION, RISK RATING, AND RECOMMENDED ACTION. THE TREES HAVE BEEN IDENTIFIED ON SITE AND TAGGED BY NUMBER WHICH CORRESPONDS WITH THE TREE INVENTORY. ALL TREES THAT THE ARBORIST SURVEYED AND TAGGED IN THE FIELD ARE RECOMMENDED FOR REMOVAL. 1,-Dm-k 1m.J :.lll Ml:IIE Eml.t .. 11115 , ......... _ Mh' 1111• SCID CHILDRENS lNSlTTUTE 2640 Benson Rood S. Renton1 WA TREE INVENTORY PLAN EXIS~NG BUii.DiNG NDll.39' Hf. FiRST l'UI. D.£V, 4\J.8' BSIIT. Fl.It. EllV. '403.&' NOTE: ) SEE ARBORIST'S REPORT FOR TREE INVENTORY TABLE ON L 1-2 0 50 100 SCALE IN FEET 150 ""l ,1]12-ff-1~-- -1 - ,._ ·201311 LI.I ~ ,, I i I N N N . . . f • • • • i i I I APPENDIX A FIELD EXPLORATION PROCEDURES AND LOGS FIELD EXPLORATION PROCEDURES Field Exploration Description Our field exploration for this project included four hand auger explorations completed on March 16, 2016. The approximate exploration locations are presented on the enclosed Site and Exploration Plan, Figure 2. Exploration locations were determined in the field by measuring distances from existing site features with a fiberglass tape relative to a 23 January 2014 Tree Inventory Plan prepared by Integrated Site Design. The vertical datum is not known. Ground surface elevations at the explorations interpolated from topographic lines presented on the referend plan. As such, the exploration locations and elevations should be considered accurate only to the degree implied by the means and methods to establish them. The following sections describe our procedures associated with the explorations. Descriptive logs of the explorations are enclosed in this appendix. Hand Auger Procedures An engineering geologist from our firm advanced a 3.5-inch diameter auger by hand, continuously observing the soil cuttings as they were retrieved. Representative portions of the soils retrieved were placed in moisture tight containers and returned to our laboratory for further visual classification and testing. The enclosed hand auger logs indicate the vertical sequence of soils and materials encountered in each exploration, based primarily on our field classifications and supported by our subsequent laboratory testing. Where a soil contact was observed to be gradational or undulating, our logs indicate the average contact depth. Our logs also indicate the approximate depths of any sidewall caving or groundwater seepage observed in the explorations, as well as all sample numbers and sampling locations. 71 PPER GEO ASSOCIATF-LLC 19023 36m Avenue West, Suite D, Lynnwood. Washin 8036 HAND AUGER HA-I Project: Children's Institute Location: See Site And Exploration Plan, Figure 2 Project No: 1601.01 Approximate Ground Elevation: 382 Feet Date Excavated: 03-16-2016 Depth Material Description Sample Ne %M Testing (ft) Loose, moist to wet, dark brown, silty SAND, with roots and fine organic material (Topsoil) _________________________________ 1 Loose to mediwn dense, moist grading to wet, mottled brown, silty SAND, some gravel, moderate iron oxide staining (Weathered Glacial Till) S-1@1.5' 2 ----------------------------------------------------- 3 Dense, moist, gray to gray-brown, silty SAND, some gravel, slight iron oxide staining (Glacial Till) Hand Auger completed at 3.3 feet on 3/16/20 l 6. 4 No groundwater seepage observed at time of exploration. No caving observed. 5 6 7 8 9 10 11 12 Note: Ne is the Dynamic Cone Penctrometer blow count per ASTM Special Publication #399. HAND AUGER HA-2 Project: Children's Institute Location: See Site And Exploration Plan, Figure 2 Project No: 1601.01 Approximate Ground Elevation; 366 Feet Date Excavated: 03-16-2016 Depth Material Description Sample Ne %M Testing (ft) Loose, moist to wet, dark brown, silty SAND, with roots and fine organic material (Topsoil) 1 ~----------------------------------------------------- Loose to medium dense, moist to wet, mottled gray-brown, silty SAND, some gravel, moderate iron oxide staining 2 (Weathered Glacial Till) 3 ----------------------------------------------------- Dense, moist, gray, silty SAND, some gravel (Glacial Till) 4 Hand Auger completed at 3.5 feet on 3/16/2016. Very slight perched groundwater seepage observed at 3 feet at time of exploration. No caving observed. 5 6 7 8 9 10 11 12 Note: Ne is the Dynamic Cone Penetrometer blow count per ASTM Special Publication #399. 71 PPER GEO ASSOCIAT,-, LLC 19023 3611,. Avenue West, Suite D, Lynnwood, Washin 8036 HAND AUGER HA-3 Project: Children's Institute Location: See Site And Exploration Plan, Figure 2 Project No: 1601.01 Approximate Ground Elevation: 3 7 4 Feet Date Excavated: 03-16-2016 Depth Material Description Sample Ne 0/oM Testing (ft) Loose, moist to wet, dark brown, silty SAND, with roots and fine organic material (Topsoil) I ----------------------------------------------------- Mediwn dense, moist, gray-brown SAND, some silt and gravel (Weathered Glacial Outwash) S-1@1.5' 2 3 4 Hand Auger completed at 3.5 feet on 3/16/2016. No groundwater seepage observed at time of exploration. Slight caving observed below 12 inches. 5 6 7 8 9 10 11 12 Note: Ne is the Dynamic Cone Peoetromcter blow count per ASTM Special Publication #399. ZIPPr-GEO ASSOCIATES, LL"" 19023 .venue West, Suite D, Lynnwood. Washington 98036 HAND AUGER HA-4 Project: Children's Institute Location: See Site And Exploration Plan, Figure 2 Project No: 1601.01 Approximate Ground Elevation: 398 Feet Date Excavated: 03-16-2016 Depth Material Description Sample Ne o/eM Testing (ft) Loose, moist to wet, dark brown, silty SAND, with roots and fine organic material (Topsoil) 1 ----------------------------------------------------- Medium dense, moist, gray-brown, fine to medium SAND, some silt (Weathered Glacial Outwash) 2 S-1@2' 3 4 5 6 Hand Auger completed at 6 feet on 3/16/2016. 7 No groundwater seepage observed at time of exploration. No caving observed. 8 9 10 11 12 Note: Ne is the Dynamic Cone Penetrometer blow count per ASTM Special Publication #399. • GEOTECHNICAL EVALUATION OF HAZARD TREE REMOVAL PLAN Children's Institute for Learning Differences 2640 Benson Road South Renton, Washington Project No. 1601.01 March 25, 2016 Prepared for: Children's Institute for Learning Differences Prepared by: ZGA Zipper Geo Associates, LLC Geotechnical and Environmental Consultants 19023 36 1h Avenue West, Suite D Lynnwood, WA 98036 Zipper Geo Associates. LLC Geotechnical and Environmental Consulting Children's Institute for Learning Differences 2640 Benson Road South Renton, Washington 98055 Attention: Ms. Carrie Fannin Project Number 1601.01 March 25, 2016 Subject: Geotechnical Evaluation of Hazard Tree Removal Plan Children's Institute for Learning Differences 2640 Benson Road South Renton, Washington 98055 Dear Ms. Fannin, In accordance with your request and written authorization, Zipper Geo Associates, LLC (ZGA) has completed the subsurface exploration and geotechnical evaluation of the Hazard Tree Removal Plan prepared by others for the Children's Institute for Learning Differences (CHILD) campus located at 2640 Benson Road South in Renton, Washington. This report presents the findings of our site reconnaissance and subsurface exploration, and our geotechnical recommendations for the project. Our work was completed in general accordance with our Proposal for Geotechnica/ Engineering Services (Proposal No. P16151) dated March 4, 2016. We appreciate the opportunity to be of service to you on this project. If you have any questions concerning this report, or if we may be of further service, please contact us. Sincerely, Zipper Geo Associates LLC James P. Georgis, L.E.G. Principal Copies: Addressee (1) Ray Robinson with Integrated Site Design, Inc. (1) 19023 36th Avenue West, Suite D Lynnwood, WA 98036 Thomas A. Jones, P.E. Principal (425) 582-9928 • TABLE OF CONTENTS INTRODUCTION ....................................................................................................................... 1 SITE DESCRIPTION .................................................................................................................. 1 PROJECT UNDERSTANDING .................................................................................................. 1 SITE RECONNAISSANCE ......................................................................................................... 2 Southeast Tree Removal Area ............................................................................................... 2 Northeast Tree Removal Area ................................................................................................ 3 Northwest Tree Removal Area ............................................................................................... 4 Central Playground Slope Tree Removal Area ....................................................................... 4 SUBSURFACE CONDITIONS ................................................................................................... 4 Published Geologic Mapping .................................................................................................. 4 Soil Conditions ....................................................................................................................... 5 Groundwater Conditions ......................................................................................................... 6 Historic Coal Mine Maps ......................................................................................................... 6 CONCLUSIONS AND RECOMMENDATIONS ........................................................................... 7 General .................................................................................................................................. 7 Geologic Hazard ECA Considerations .................................................................................... 7 Tree Stump and Root System Retention ................................................................................ 8 Planting Recommendations .................................................................................................... 9 Temporary Erosion Control Considerations ........................................................................... 10 Retention of Woody Material ................................................................................................. 10 Off-Site Tree Removal Considerations .................................................................................. 10 General Steep Slope Considerations ..................................................................................... 10 CLOSURE ................................................................................................................................ 11 FIGURES PREPARED BY ZGA Figure 1 -Vicinity Map Figure 2 -Site and Exploration Plan FIGURES PREPARED BY OTHERS Tree Inventory Plan, Sheet L 1.1 Tree Inventory Table, Sheet L 1.2 APPENDICES Appendix A -Subsurface Exploration Procedures and Logs GEOTECHNICAL EVALUATION OF HAZARD TREE REMOVAL PLAN CHILDREN'S INSTITUTE FOR LEARNING DIFFERENCES 2640 BENSON ROAD SOUTH RENTON, WASHINGTON Project No. 1601.01 March 25, 2016 INTRODUCTION This report documents the surface and subsurface conditions encountered at the site and our geotechnical evaluation of the Hazard Tree Removal Plan prepared by others for the Children's Institute for Leaming Differences (CHILD) campus located at 2640 Benson Road South in Renton, Washington. The project description, site conditions, and our geotechnical conclusions and recommendations are presented in the text of this report. Supporting data including detailed exploration logs, field exploration procedures, and other supporting information are presented as appendices. Our geotechnical scope of services for the project included a document review, site reconnaissance, subsurface evaluation, geotechnical analysis, and preparation of this report. The subsurface evaluation consisted of completing four hand auger explorations (designated HA-1 through HA-4) located near proposed tree removal areas and steep slopes. The hand auger explorations extended approximately 3Y. to 6 feet below the existing ground surface. SITE DESCRIPTION The site is located at 2640 Benson Road South in Renton, Washington. The CHILD facility is located in the south-central portion of the site and includes campus buildings and a perimeter access drive with a parking lot on the east side of the facility. The northern portion of the site is undeveloped and includes mixed evergreen and deciduous trees with a moderately well- developed understory of brush and groundcover. The site is bounded to the north by a multi- family residential development, to the south by South 27'" Street, to the east Benson Road South, and to the west by a middle school. The approximate site location is shown on the enclosed Vicinity Map, Figure 1. Existing site features, site topography, and nearby features are shown on the enclosed Site and Exploration Plan, Figure 2. PROJECT UNDERSTANDING The site is mapped by the City of Renton as containing Coal Mine Hazard, Steep Slope Hazard, and Landslide Hazard Environmental Critical Areas (ECAs). We understand that the City has requested a geotechnical evaluation of the Hazard Tree Removal Plan be completed to assess the risk to regulated Geologic Hazard ECAs and their associated buffers, as defined in Part 4-3- 050-G-5 of the City of Renton Municipal Code (RMC) that may result from the planned tree removal and provide recommendations to mitigate identified risks. Our understanding of the project is primarily based on a review of the following documents and discussions with Integrated Site Design and representatives for CHILD. Zipper Geo Associates. LLC Children's Institute for Learning Differences Project No. 1601.01 March 25, 2016 • Tree Risk Assessment, CHILD, 2640 Benson Road South, Renton, Washington, prepared by Greenforest Incorporated Consulting Arborist, dated December 2, 2015. • Children's Institute, 2640 Benson Road South, Renton WA, Tree Inventory Plan, Sheet L 1.1, prepared by Integrated Site Design, dated March 24, 2016. • Children's Institute, 2640 Benson Road South, Renton WA, Tree Inventory Table, Sheet L 1.2, prepared by Integrated Site Design, dated March 24, 2016. Based on our review of the referenced documents, it appears that the hazard tree removal plan includes the pruning and removal of trees located within the CHILD property, and to a lesser extent, the removal of trees from the adjacent property to the east. A summary of the planned tree removal is presented below. On-Site Hazard Tree Removal: The plan identifies fifty-two trees on the site that have been rated by Greenforest Incorporated as having a moderate to high risk rating. Fifty of these trees are listed for removal and two are listed for pruning or deadwood removal. Of the fifty-two identified trees, forty-six trees are maple, five trees are cottonwood, and one tree is alpine fir. About thirty six of the fifty-two trees are located within ECA areas or their buffers as shown on Plan Sheet L 1.1 Off-Site Hazard Tree Removal: The plan identifies eleven trees east of the mapped site property line that have been rated by Greenforest Incorporated as having a moderate to high risk rating and listed for removal. Off the eleven identified trees, two trees are maple, eight trees are willow, and one tree is cherry. About ten of the eleven trees are located within ECA areas or their buffers as shown on Plan Sheet L 1.1 Copies of the Tree Inventory Plan and Tree Inventory Table (Plan Sheets L 1.1 and 1.2) are enclosed with this report without modification to assist in report interpretation. SITE RECONNAISSANCE We completed a reconnaissance of the property and immediate vicinity during a site visit completed on March 16, 2016. The purpose of the reconnaissance was to identify surficial features of site conditions such as the presence or absence of groundwater seepage, the presence or absence of surface erosion, indications of past slope instability, indications of past land use, the type and extent of existing vegetation, the location of trees identified for removal, and other site features that may be affected by the planned tree removal. The enclosed Site and Exploration Plan, Figure 2, shows the approximate location of some of the observed site features. A summary of our site observations is presented below. Southeast Tree Removal Area About 10 trees are listed for removal in this area. The trees are located within a west-facing, off- site slope that extends down to a relatively new rockery wall constructed just within the property Page2 Zipper Geo Associates. LLC Children's Institute for Learning Differences Project No. 1601.01 March 25, 2016 line. Based on the topographic site plan, the slope inclination above the rockery ranges from about 23 to 44 percent (13 to 23 degrees). The rockery appears to be in good condition, ranges from about 4 to 6 feet tall, includes a drainage zone of quarry spall backfill, and appears to include a perforated drain pipe. In addition to the listed trees, slope vegetation includes dense Laurel bushes, blackberry, fern, ivy, blue star creeper, and grasses. We did not observe any obvious indications of past slope movement or distress. Surficial erosion was slight and limited to several foot paths. We did not observe any obvious indications of groundwater seepage from the exposed slope surface. However, the rockery drain pipe daylights at the north end of the wall and we observed about Y. to 1 gpm discharge from this pipe at the time of our site visit. The discharge flowed down a roadside ditch to a dispersion area in the northwest portion of the site. The approximate rockery groundwater discharge location and subsequent down-gradient surface water flow is shown on Figure 2. Northeast Tree Removal Area For the purposes of this report, the northeast tree removal area includes the central steep slope area located in the northern portion of the site and the gently sloping bench located between the central steep slope area and the east property line. The north-central, west-facing slope has inclinations ranging from about 23 to 44 percent (13 to 23 degrees). In addition to the trees listed for removal, slope vegetation includes mixed evergreen and deciduous trees which were considered by the arborist to be of low risk and are not listed for removal, blackberry, fern, ivy, and grasses. Areas between vegetation were typically mantled by several inches of forest duff. We did not observe any obvious indications of past slope movement or distress. Surficial erosion was slight and limited to several foot paths. We did not observe any obvious indications of groundwater seepage from the exposed slope surface. We observed what appears to be a lobe of fill soils extending into the slope area from the eastern bench area. The fill appeared to be relatively old and may have been associating with mass grading for the CHILD development. The approximate location of the fill is shown on Figure 2. The bench area located between the north-central steep slope and the east property line slopes gently west with inclinations ranging from about 5 to 12 percent (3 to 8 degrees). We estimate that about 60 to 70 percent on the bench is surfaced with wood chips. The remainder of the area consists of soil with scattered ferns and grass. We did not observe any obvious indications of past slope movement or distress associate with the bench or adjacent slopes. Surficial erosion was slight and limited to several foot paths. We observed slight surface water flow in the northern portion of the bench area. The flow appeared to be originating from a spring located near the top of the steep off-site slope which extends up to the adjacent middle school play field. We visually estimated a flow rate on the order of Y. gallon per minute at the time of our evaluation. The spring had incised a small drainage feature about two feet wide and one foot deep into the surface of the off-site slope. Surface water from the spring was infiltrating into the bench soils at the time of our evaluation and was not running down the north-central steep slope. The approximate location of the spring and down-gradient surface water flow is shown on Figure 2 Page 3 Zipper Geo Associates. LLC Children's Institute for Learning Differences Project No. 1601.01 March 25, 2016 Northwest Tree Removal Area For the purposed of this report, the northwest tree removal area includes the north-central gently sloping bench area located in the northern portion of the site and the steep slope area located between the north-central gently sloping bench area and the west property line. The north-central bench area slopes gently west with inclinations ranging from about 1 O to 17 percent (6 to 10 degrees). In addition to the trees listed for removal, vegetation includes mixed evergreen and deciduous trees which were considered by the arborist to be of low risk and are not listed for removal, blackberry, fem, ivy, and grasses. Areas between vegetation were typically mantled by several inches of forest duff. We did not observe any obvious indications of past slope movement or distress. Surficial erosion was slight and limited to several foot paths. We did not observe any obvious indications of groundwater seepage. The west-facing slope located between the north-central bench and the west property line has typical inclinations ranging from about 30 to 56 percent (17 to 30 degrees). An isolated section of slope adjacent to the sidewalk has an inclination of about 100 percent (45 degrees) with a maximum slope height of about 6 feet, and appears to be the result of a cut completed to construct the sidewalk. In addition to the trees listed for removal, slope vegetation includes mixed evergreen and deciduous trees which were considered by the arborist to be of low risk and are not listed for removal, blackberry, fern, ivy, and grasses. Areas between vegetation were typically mantled by several inches of forest duff. We did not observe any obvious indications of past slope movement or distress. Surficial erosion was slight and limited to several foot paths. We did not observe any obvious indications of groundwater seepage, but standing water was present in two drainage ditches located near the west property line at the time of our evaluation Central Playground Slope Tree Removal Area A steep west-facing slope is located near the middle of the site between the playground and the main parking lot. Slope inclinations range from about 42 to 80 percent (23 to 39 degrees). Slope vegetation primarily consists of ivy and blackberry brush, with scattered patches of grass in the southern portions of the slope and several deciduous trees. In general, the trees located on the slope exhibited pistol-butted growth pattern (bent trunks near the ground surface) which is indicative of slope creep. We did not observe indications of deep-seated slope movement or shallow sloughing. Surficial erosion was slight and limited to non-vegetated portions of the slope. We did not observe any obvious indications of groundwater seepage. SUBSURFACE CONDITIONS Published Geologic Mapping We assessed the geologic setting of the site and surrounding vicinity by reviewing The Geologic Map of the Renton Quadrangle, King County, Washington, U.S. Geological Survey Map GQ-405, Page4 Zipper Geo Associates. LLC Children's Institute for Learning Differences Project No. 1601.01 March 25, 2016 1965. The geologic map indicates the site and immediate vicinity are mantled by Quaternary Ground Moraine deposits (091). This deposit is described as thin glacial ablation till over lodgment till deposited by the Vashon Stade of the Frasier glaciation. The lodgment till is further described as a compact, unsorted mixture of sand, sill, clay, and gravel, commonly termed "hardpan". The ablation till is described as being compositionally similar to lodgment till, but much less dense. Tertiary age Renton Formation deposits are mapped about Y. mile to the northeast of the site. The Renton formation is described as arkosic sandstone, mudstone, and shale with several beds of coal. The Renton Formation has an extensive history of surface and subsurface coal mining. Stratigraphic information presented in the referenced geologic map indicates that Renton Formation deposits underlie the surficial glacial deposits at an unspecified depth. Soil Conditions The subsurface exploration for this project included four hand auger explorations (HA-1 through HA-4) located near proposed tree removal areas and steep site slopes. The hand auger explorations extended approximately 3Y. to 6 feet below the existing ground surface. The approximate exploration locations are shown on the enclosed Site and Exploration Plan, Figure 2. Soils were visually classified in general accordance with the Unified Soil Classification System. Detailed, descriptive logs of the subsurface explorations and the procedures utilized in the subsurface exploration program are presented in Appendix A. Generalized descriptions of subsurface soil conditions observed at the exploration locations are presented below. The stratification and horizontal extent of the soil types observed in our explorations may vary between explorations. Stratification boundaries on the exploration logs represent the approximate depth of changes in soil types, although the transition between materials may have been gradual. Please refer to the hand auger logs in Appendix A for a more detailed description of the conditions encountered at the exploration locations. Hand augers HA-1 and HA-2 were completed in the northern portion of the site. In general, the explorations encountered about 7 to 10 inches of loose, organic-rich silty sand interpreted as topsoil. Below the topsoil, loose to medium dense silty sand with some gravel was encountered to a depth of about 2Y. lo 3 feet and is interpreted as weathered glacial till. Dense, silty sand with some gravel, interpreted as unweathered glacial till, was encountered below the weathered horizon and extended to the total depth explored of 3Y. feet below existing grade. Hand augers HA-3 and HA-4 were completed in the west-central and central portions of the site, respectively. These explorations encountered about 12 inches of loose organic-rich silty sand topsoil over primarily granular deposits interpreted as glacial outwash. In hand auger HA-3, the outwash consisted of medium dense sand with some gravel and silt which extended to the total depth explored of 3.5 feet below existing grade. In hand auger HA-4, the oulwash consisted of medium dense fine Page5 Zipper Geo Associates. LLC Children's Institute for Learning Differences Project No. 1601.01 March 25, 2016 to medium sand with some silt which extended to the total depth explored of 6 feet below existing grade. Groundwater Conditions Slight groundwater seepage was observed in hand auger HA-2. Groundwater seepage was not observed in the other hand auger explorations. The groundwater observed in HA-2 is interpreted to represent water perched above lower permeability glacial till soils encountered at a depth of 3 feet. Given the relatively low permeability of the glacial till soils encountered in the northern portion of the site, perched groundwater may develop above the till or within sandy zones within the till during periods of extended wet weather. Perched groundwater may also develop above lower permeability layers within the glacial outwash deposits, which are often stratified. These observations represent groundwater conditions at the time of the field exploration. Groundwater conditions should be expected to fluctuate due to changes in season, precipitation patterns, site utilization, on-site or off-site irrigation activities, and other on-and off-site factors. Historic Coal Mine Maps As part of our site evaluation, we completed a review of historic coal mine maps available from the Washington State Department of Natural Resources. Based on our review, it appears that the site is underlain by portions of the Sunbeam Mine and Renton Mine. A summary of our historic coal mine map review relative to these mines is presented below. Sunbeam Mine: The Sunbeam Mine was operated by the Renton Coal Company from 1922 to 1929. The Sunbeam portal (or mine entrance) is mapped about 2/3 of a mile north-northwest of the CHILD site and has a reported main "water level" gangway elevation of about 68 feet. The mine chutes appear to have extended up and to the south-southwest of the main gangway (away from the CHILD site) along a coal seam inclined or dipping to the north-northeast at an angle of about 65 degrees from horizontal. Based on the mapped data, it appears that the Sunbeam mine workings are primarily west of the CHILD site, with the eastern end of the mine underlying a portion of Benson Road South and the southwestern portion of the CH I LD site. Given a site ground surface elevation of about 400 feet, it appears that those portions of the mine workings located below or near the CHILD site are on the order of 200 to 300 feet below the ground surface. The City of Renton has mapped the mine workings west-southwest of the site (west of Benson Road South) as having a moderate to high risk, and the workings mapped below the CHILD site as having a moderate risk. Renton Mine: The Renton Mine was operated by the Seattle Electric Company in 1919 and the Renton Coal Company from 1920 to 1955. It appears that the Renton Mine 6th Gangway South and associated workings extended below the CHILD site. The historic maps do not include explicit information regarding the elevation of the workings in this area. However, the workings appear to be an extension of the generally north-northeast dipping coal seam worked in the Sunbeam Mine. Page6 Zipper Geo Associates, LLC Children's Institute for Learning Differences Project No. 1601.01 March 25, 2016 Based on the elevation of the Sunbeam main water level gangway and the indicated strata dip angle and orientation, it appears that the Renton Mine workings in the vicinity of the site are likely greater than 300 feet below the ground surface. The City of Renton has mapped the Renton Mine workings at the project site and nearby vicinity as having a moderate risk. CONCLUSIONS AND RECOMMENDATIONS General Based on the results of our site reconnaissance, document review, subsurface exploration, and geotechnical analysis, it is our opinion that the proposed tree removal plan is feasible from a geotechnical perspective. Provided that the conditions and recommendations contained within this report and the provisions of the Renton Municipal Code (RMC) are satisfied, it is our opinion that the proposed Hazard Tree Removal Plan will not increase the potential for soil movement and the risk of damage to existing structures, the site, and to adjacent properties from soil instability will not be increased. The following sections provide a discussion regarding City of Renton regulated ECAs and recommendations to reduce risks associated with the tree removal plan. Geologlc Hazard ECA Considerations The site is mapped by the City of Renton as containing Coal Mine Hazard, Steep Slope Hazard, and Landslide Hazard Environmental Critical Areas (ECAs). We understand that the City has requested a geotechnical evaluation of the Hazard Tree Removal Plan to assess the risk to regulated Geologic Hazard ECAs and their associated buffers, as defined in Part 4-3-050-G-5 of the City of Renton Municipal Code (RMC) that may result from the planned tree removal and provide recommendations to mitigate identified risks. Part 4-3-050-C-3 of the RMC indicates that the removal of dangerous trees which have been approved by the City and certified dangerous by a licensed landscape architect or certified arborist is exempt from RMC ECA restrictions and may be permitted by the City. The following sections present our evaluation of Coal Mine Hazard, Steep Slope Hazard, and Landslide Hazard ECA's relative to the Hazard Tree Removal Plan. Coal Mine Hazard Areas: Coal Mine Hazard Areas include areas with known subsurface coal mine workings. The site is mapped within a Medium Coal Mine Hazard Risk Area and slightly northeast of a High Coal Mine Hazard Risk Area. Our review of historic coal mine maps for the site vicinity (Renton Mine and Sunbeam Mine) indicate mine workings depths in excess of 200 feet. Based on our document review and site observations, it is our opinion that the site are consistent with the criteria for a Medium Coal Mine Hazard Risk Area. Steep Slope Hazard Areas: The City of Renton maps portions of the site as Steep Slope Hazard Areas. The City mapped hazard areas are primarily located along the eastern property line, within the northern, undeveloped, wooded portion of the site, and the slope area between the main school building and the playground area. The enclosed Tree Inventory Plan, Sheet L 1.1 identifies Steep Page7 Zipper Geo Associates, LLC Children's Institute for Learning Differences Project No. 1601.01 March 25, 2016 Slope Hazard Areas and an associated 15 foot wide buffer based on site topography. Based on our document review and site reconnaissance, it is our opinion that the critical areas and associated buffers presented on Sheet L 1.1 are in general accordance with RMC Steep Slope Hazard Area criteria. Landslide Hazard Areas: The City of Renton ECA maps generally identify the central and western portions of the northern, undeveloped, wooded area and the slope between the playground and the school facility as High Landslide Hazard Areas, although the City mapped hazard areas to not appear to correlate well to the site specific topography presented on Sheet L 1.1. This may be due to the City's use of a more regional topographic database to identify hazard area. The RMC defines a high landslide hazard area as an area with slopes greater than 40 percent, and areas with slopes between fifteen and forty percent and underlain by soils consisting largely of silt and clay. Based on our document review and subsurface explorations, it is our opinion that site slopes exceeding forty percent are consistent with the RMC criteria for Landslide Hazard Areas. These areas are generally identified on the Tree Inventory Plan, sheet 1.1. Risk Evaluation Summary: Based on mapped mine working depths in excess of 200 feet below existing grade, it is our opinion that the Hazard Tree Removal Plan will have no measurable adverse impact on the Coal Mine Hazard and will not increase the risk of coal mine induced damage to the subject site or adjacent properties. Provided that the conditions and recommendations contained within this report and the provisions of the Renton Municipal Code (RMC) are satisfied, it is our opinion that the proposed Hazard Tree Removal Plan will not increase the potential for soil movement and the risk of damage to existing structures, the site, and to adjacent properties from soil instability will not be increased. Tree Stump and Root System Retention Tree root systems provide erosion protection and bio-reinforcement for slope soils, thereby increasing the strength of the soil mass and reducing the risk of slope instability. However, the weight of the tree can increase the forces tending to drive slope instability and the rocking action of the root mass during high winds can result in loosening of the slope soils, resulting in a reduction in slope stability, particularly for large, heavy trees located on or near the crest of steep slopes. There is some debate in the scientific community regarding the relative contributions of these different factors to slope stability, but the general consensus appears to be that under most conditions the presence of trees (in particular the bio-reinforcement they provide) results in a net improvement to slope stability. Based on our review of the Tree Inventory Table, it appears that about 61 of the 63 trees listed for removal or pruning consist of cottonwood, maple, or willow. These tree species often survive cutting by generating new growth from the stump, often referred to as stump sprouting. Stump sprouts provide nourishment for maintenance of the root system while greatly reducing the negative impact of tree weight and wind driven soil loosening. We therefore recommend that the trees planned for removal be cut off near the ground surface and that the stumps and root masses Page 8 Zipper Geo Associates, LLC Children's Institute for Leaming Differences Project No. 1601.01 March 25, 2016 be left In place within the Steep Slope Hazard Areas and associated buffers identified on Sheet L 1.1. We anticipate that there may be some benefit to potential utilization of the site by removing stumps from the gently sloping bench areas located in the northern portion of the site. In our opinion, the removal of stumps within the bench areas is feasible from a geotechnical perspective without adversely affecting the site slopes. An 8-inch diameter alpine fir (tree #4) is listed for removal from a grass lawn area near the perimeter access drive. In our opinion, the stump of this tree may also be removed to facilitate landscape maintenance without adversely affecting the site slopes. Planting Recommendations Some portion of the cut trees may not develop stump sprouts or may not receive adequate nutrients from the sprouts to prevent decay of the root mass over time. Based on our evaluation of the site conditions, it is our opinion that the decay of the root systems associated with trees 1 through 3 located near the top of the steep central slope adjacent to the playground could result in a reduction in the stability of the slope near the removed trees relative to shallow surficial sliding. In our experience, it typically takes about 3 to 5 years to realize a significant reduction in the bio- reinforcement provided by a tree that does not survive cutting. As a precautionary measure, we recommend that the Hazard Tree Removal Plan include new plantings near trees 1 through 3. We recommend that native woody shrubs or small trees be considered to reduce the need for watering and keep the weight and wind loading characteristics of the new growth to reasonable levels as it matures. The following table provides some plant species that could be considered to reduce the potential for erosion and increase resistance to shallow surficial sloughing. The information presented below is a relatively small sampling of plant species discussed in the 1993 publication Slope Stabilization and Erosion Control using Vegetation, produced by the Washington State Department of Ecology (Publication 93-30). The table below is by no means intended to be comprehensive or restrictive relative to the selection of appropriate plantings. POTENTIAL PLANT SELECTION GUIDE Plant Name Form&Habit Mature Rooting Recommended Size Characteristics Spacing Snowberry Evergreen shrub; Height: 4' Fibrous, (Symphoricarpos Albus) spreads by runners to Spread: 3' Shallow depth. 2'+ form thicket Salal Evergreen shrub; Height: 3' Fibrous, (Gaultheria Sha/Ion) spreads by runners to Spread: 3' Shallow depth. 2'+ form thicket Evergreen Huckleberry Evergreen shrub; does Height: 6' Fibrous, 3'+ Oemleria Cerasiformis) not spread Spread: 3' Shallow depth. Ocean Spray Deciduous shrub; does Height: 10'+ Fibrous, (Holodiscus Discolor) not always spread Spread: 6' Moderate depth. 4'+ annressivelv Page9 Zipper Geo Associates. LLC Children's Institute for Learning Differences Project No. 1601.01 March 25, 2016 Vine Maple Deciduous shrub; does (Acer Circinatum) not always spread annressivelv Hooker Willow Deciduous shrub; does /Salix Hookerianal not soread Height: 15'+ Fibrous, Spread; 10' Moderate depth. 8'+ Height: 20'+ Fibrous, 3'+ Soread: 15' Moderate deoth. Reference: Slope Stabilization and Erosion Control using Vegetation, Washington State Department of Ecolonu Publication 93-30, 1993. Temporary Erosion Control Considerations We anticipate that the tree removal process will likely result in disturbance of the ground surface and a temporary increase in the potential for erosion. We therefore recommend that the tree removal service utilize means and methods intended to minimize ground disturbance. In addition, we recommend that soils exposed within Steep Slope Hazard Areas and their buffers be covered with a temporary erosion control material, such as sterile straw or arborist mulch. Retention of Woody Material In our opinion it appears geotechnically feasible to retain much of the woody debris generated from the hazard tree removal as habitat enhancement within wooded portions of the site. However, based on our evaluation, we recommend that woody material greater than 6-inches in diameter be removed from the following areas as the weight of the material could adversely affect steep slopes or the performance of existing drainage features. • The drainage features near Benson Road South and adjacent sleep slopes identified on Figure 2. • The steep slope located between the playground and the school facility and the 15-foot wide buffer above this steep slope area. Off-Site Tree Removal Considerations The Hazard Tree Removal Plan appears to include the removal of 11 trees located beyond (east of) the subject property. We recommend that all agreements and/or permits that may be needed to complete off site work be coordinated with the adjacent property owner and the City before beginning work. General Steep Slope Considerations Owners of properties containing or adjacent to steep slopes should recognize that soil loss or downslope displacement from steep slopes is a naturally occurring mass wasting process, and that some soil loss from steep slopes should be expected over time, particularly in response to episodic severe storm events. The conclusions and recommendations presented in this report are intended to allow for the removal of hazard trees while maintaining the existing stability of the site slopes. The findings presented in this report should not be interpreted as indicating that the site steep slopes will be stable under all possible future conditions. Page 10 Zipper Geo Associates. LLC Children's Institute for Leaming Differences Project No. 1601.01 March 25, 2016 CLOSURE The analysis and recommendations presented in this report are based, in part, on the explorations completed for this study. The number, location, and depth of the explorations were completed within the constraints of budget and site access so as to yield the infonnation to formulate our recommendations. This report has been prepared for the exclusive use of The Children's Institute for Learning Differences, Integrated Site Design, and their agents, for specific application to this project and has been prepared in accordance with generally accepted geotechnical engineering practices. No warranties, express or implied, are intended or made. Site safety is the responsibility of others. In the event that changes in the nature, design, or location of the tree removal as outlined in this report are planned, the conclusions and recommendations contained in this report shall not be considered valid unless Zipper Geo Associates, LLC reviews the changes and either verifies or modifies the conclusions of this report in writing. Page 11 REFERENCE: GOOGLE EARTH 2016. NOT TO SCALE CH ILDREN'S INSTITUTE FOR LEARN ING DIFFERENCES 2640 Benson Road South Renton , Washington 1----------~ VICINITY MAP DATE: March 2016 Job No . 1601.0 1 Zipper Geo Associates, LLC FIGURE 1 19023 36th Ave. W.,Suite D Lynnwood, WA SH T. 1 of 1 J e-_ ,,-CROUNOWATER SEEPAGE _, NEAR FENCE LINE -- W •=• TREE PREYIOUSL Y REMOVED ~TREEi/1998 ~ TREE TO BE RETAINED ®ii~· TREE TO BE REMOVED D CRITICAL AREA B OUNDARY ,-----i L __ _J 15' CRITICAL AREA BUFFER SETBACK AREA TO BE CLEARED FUTURE BUILDING SITE TREE INVENTORY PLAN SCALE: 1" ~ 50' ,-" 2015. THE REPORT INCLUDED A GENERAL Pl.AN A.ND TREE INVENTORY. WHICH DOCUMENTED THE HAZARD TREE SIZE. SPECIES. CONDITION. RISK RAT ING. AND RECOMMENDED ACTION THE TREES HAVE BEEN IDENTIFIED ON SITE ANO TAGGED BY NUMBER WHICH CORRESPONDS WITH THE TREE INVENTORY ALL TREES THAT THE ARSORIST SURVEYED ANO T AGGEO IN THE FIELD ARE RECOMMENDED FOR REMOVAL I ._ .... .._ .. tOOJfllA'CIC 3UrU••1S ",,,.,.,_ 8'UC91191ia~HJXW CHILDRENS INSTITUTE 2640 Benson Rood S. Renton, WA TRE( IH'-'tNTORT PL.AN t' .. ,~....__-' , .... • f ~:-;· NOTE: SEE ARBORISTS REPORT FOR TREE INVENTORY TABLE ON L 1-2 0 ~50 100 SCALE IN FEET LEGEND S HA-1 ,-· 150 I " .... .!!:,Jll HAND AUGER NUMBER AND APPROXIMATE LOCATION APPROXIMATE LOCATION OF GROUNDWATER SEEPAGE APPROXIMATE LOCATION OF SURFACE WATER FL OW CtillDREN'S INSTITUTE FOO LEARNING OlFERENCES :IB40 Benson Road Sooth __ Reotoo. Washington SITE AND EXPLORATION PLAN DATE Mardi 2016 Job No. 1601.01 z:=~:1::0~·.·;i~;tc FIGURE 2 Lynnwood. WA SHT 1 of 1 ~ ,--L. . •--:::C·~~\?,o•."•,,, •. _TREE INVENTORY LEGEND -~~~ . ~ TREE PREVIOUSLY REMOVED -'t-\S~)' I ~--:, TREE#1998 • ''} .1\ \ (/1..__ 7 r---~ TREETOBERETAINEO ~i,...Jf__L \ '~~~--..,_-:="-'*~' ~-TREE TO BE REMOVED CRITICAL AREA BOUNDARY ~~::;.~\~ \4. -"1-4-~~ ~ ~~::~\--~ THE TREES ON THIS PLAN SHOWN AS TO BE REMOVED ARE BASED ON AN ~ ARBOREAL ASSESSMENT REPORT PREPARED BY GREENFOREST CONSUL TING ARBORISTS FOR THE CHILD INSTITUTE DATED DECEMBER 2, 2015. THE REPORT INCLUDED A GENERAL PLAN AND TREE INVENTORY, WHICH NOTE: DOCUMENTED THE HAZARD TREE SIZE, SPECIES, CONDITION, RISK RATING, SEEARBORIST'S REPORT FOR TREE INVENTORY TABLE ON L 1-2 ANO RECOMMENDED ACTION. THE TREES HAVE BEEN IDENTIFIED ON SITE 15' CRITICAL AREA BUFFER SETBACK AREA TO BE CLEARED FUTURE BUILDING SITE E) Jc~~E,..'~~f.NTORY PLAN AND TAGGED BY NUMBER WHICH CORRESPONDS WITH THE TREE INVENTORY O 50 100 All TREES THAT THEARBORIST SURVEYED AND TAGGED IN THE FIELD ARE RECOMMENDED FOR REMOVAL. 1-~n-,~ CHILDRENS INSTITUTE 1:ma .... •'j[ 111: 2640 Benson Road S. iunr. • NUS Rentan, WA , ....... ·-~~··, ~.._H.all lREE INVENTORY PLAN SCALE IN FEET 150 _,,..,,,.,,1-- -- " ... ·2ou11 .. Ll.1 Greenforest @ Registered Consulting Arborist C:.rrle hnr*I.~ Dlred!N"•OIILD RE: Trtt Risk i1messn1ent _,..., Pap,9o'12 Att.chmtn1 No. -4 Tree~ T-.... . .. llemrili,,1111:111111 ,_ ... -~ -hit Mo!Jt' "-·'--tc,J.rl . .. "'· ... '. . -·-Part Most .• .., .. ... "'" --"""' """ ' ,. --,_ ... ,-......... " • """ ....... ....... ... ' " -""'"" ......... ,~ ...... ... ' , .. , ---,;,rmufti -" ......... " • -• w= --..._ ... " • • ""' --......... • • " , ..... ...... ... .._ ... ., " ........ ....... ......... Doublo, ..... lndulled s .... -.... •• · or ·-· • IIN!m1 . ..... ... " • ----~tree ~deadl&" n ., ~dleltatk n -~ ........... ..._L ~-----SI ··ormultl..i.stams --"'m _,ll ~,10 ~---w ---'--1-• incksln1nml< orffl\lRl•lffl'l'ls " --.. • ""' ----• 512: 5 crxlcslntnnl or multi .... st.ms " ......... " • ""' --........... • cno:b rn tNlll w-.. ~ ---" " • ---·----" .. •• ~-~_lnuunk .... .... " ......... " • Mr" ----~ --n """" .. 01ldailnw il!ormuit;:.--::-stllffll·-" ---.. 1411uo • -or mull!·"" stems -.. _ ... 12 '411& -·· u, ..... " ........... .. .. ,, • w-1 ---~ ~---u IU&-}4 ... -· wm• ·-" ........... .. u -USt.ii--·--~ --" .... • wm, ..~ " --.. DKay.~falh ..... Tll,ll'lk-undl. deblck, " u ""M ....... " ......... ~ " .. ~ ·---·-,----" u -.. --" Relll-tl'M GModtmll lilnpl Cllfb, .. .. ... --......... d«ay, pre/lolls Wure. .. ,. .. c.-blntrllnk --...... .. " " ...... -........ ·-. ........ ~--1818-10 .. , .. ormu~stitna -- •u Smd stem dnd, top af Prullelltll'1!ffl0d .. ' Cl'lckslntnm s w -.......... " --$1·-'· orm-~e mm, ·-6"stem1nd " '"" "'"" l'ffll!oosfallu111 ,w -' ......... .. 1" 16 M --ormultl..a..~, " ---T-·-... necoo,w,.-lded ... "'" .. --'-1: Most ••-k,to Fall --"""' ... .-,_ ,_ ... ..,.--~ ll«Q1¥ikiMkd ............... .... ... --"''" ""'" u ,,110-1• ····'· -~-SI 'ormu-· · ffi!ffl5 . ......... .. ,•10-1• ... -.. m•• -""" .._ ... --· Crad.s In trwnk, decay, ---" 10,U,14 ... --M -··orm-···-.......... " . " ... -SI · or mufti-'-sterru ,.~ .. _ ... Cl'te:b ln In.ink, decl!V, $twnp$l)rtlllt.deay, " . ,. . .. -_Sl!P or mu_. stems -. .. _ ... ---... cncb In trunl<. ck-e,y, ·-"' •••u ·-· -Sl""leormultl""'itl!ITIS ·---" W.12" ...... 51--·-ormu~·-~ .. _ ... --· ··--·· OKbln trunk, dKl,y, 51-~-Of----·~ sterm ·-. -.-" "" ,anu .... d«lne --" .... • ........ ·~~-..-mulll""'!!tl!ms ,-.. _ .... " s• 10-u -w -........ --Stumpi;prout,. decay, " • ------........ .......... -·-_!' "' ------· .__tf!!_ " . ,, • ·-··--·-ounultl"'t! stems ·-. ......... " ... -• or mull: •= .... .... .. _ .... ---" ,. WT""' ' w ·--.......... ..... --" u, ..... ' mm --.. _ ... " 1.;1·~ 12 -1 ••· luwmultl"""sttms ,-......... --· --· "' '''6-14 .. -,.._ SI ·ormu-···mms ,--·-... --'-· . " IS 6-14 .... _ ... _ ' w--....... ......... " '"' 10-U -ormu ··---" ... .,., .... .......,,., ' wm, -........ .......... ... -·-" ... ,. ..... Pl'Nllusflillure ' M--·-· --" uu I=, 1-· • ormu"'•lestems. --.. _ ... I "'"'""""' " 14114 M ,. -· SI -··ormulll"'"'stam' ··-.. _ ... " •. CHILDRENS INSTilUTE 1 1:1-1 --201lll 1-w-~ 100-IMII 2640 Benson Rood S. :Dn.t. •mm Renton WA Ll.2 ........ .. .-..... TREE lN'IENTOR'i' TA81...E --. ---~- APPENDIX A FIELD EXPLORATION PROCEDURES AND LOGS FIELD EXPLORATION PROCEDURES Field Exploration Description Our field exploration for this project included four hand auger explorations completed on March 16, 2016. The approximate exploration locations are presented on the enclosed Site and Exploration Plan, Figure 2. Exploration locations were determined in the field by measuring distances from existing site features with a fiberglass tape relative to a 23 January 2014 Tree Inventory Plan prepared by Integrated Site Design. The vertical datum is not known. Ground surface elevations at the explorations interpolated from topographic lines presented on the referend plan. As such, the exploration locations and elevations should be considered accurate only to the degree implied by the means and methods to establish them. The following sections describe our procedures associated with the explorations. Descriptive logs of the explorations are enclosed in this appendix. Hand Auger Procedures An engineering geologist from our firm advanced a 3.5-inch diameter auger by hand, continuously observing the soil cuttings as they were retrieved. Representative portions of the soils retrieved were placed in moisture tight containers and returned to our laboratory for further visual classification and testing. The enclosed hand auger logs indicate the vertical sequence of soils and materials encountered in each exploration, based primarily on our field classifications and supported by our subsequent laboratory testing. Where a soil contact was observed to be gradational or undulating, our logs indicate the average contact depth. Our logs also indicate the approximate depths of any sidewall caving or groundwater seepage observed in the explorations, as well as all sample numbers and sampling locations. PPER GEO ASSOCIATI , LLC 19023 36& Avenue West, Suite D, Lynnwood., Washington 98036 HAND AUGER HA-1 Project: Children's Institute Location: See Site And Exploration Plan, Figure 2 Project No: 1601.01 Approximate Ground Elevation: 3 82 Feel Date Excavated: 03-16-2016 Depth Material Description Sample Ne o/oM Testing (ft) Loose, moist to wet, dark brown, silty SAND, with roots and fine organic material (Topsoil) ----------------------------------------------------- I Loose to medium dense, moist grading to wet, mottled brown, silty SAND, some gravel, moderate iron oxide staining (Weathered Glacial Till) S-1@1.5' 2 ----------------------------------------------------- 3 Dense, moist, gray to gray-brown, silty SAND, some gravel, slight iron oxide staining (Glacial Till) Hand Auger completed at 3.3 feet on 3/16/2016. 4 No groundwater seepage observed at time of exploration. No caving observed. 5 6 7 8 9 10 II 12 Note: Ne is the Dynamic Cone Penetrometer blow count per ASTM Special Publication #399. ZIPPI GEO ASSOCIATES, LL 19023 36-Avenue West, Suite D, Lynnwood, Washington 98036 HAND AUGER HA-2 Project: Children's Institute Location: See Site And Exploration Plan, Figure 2 Project No: 1601.01 Approximate Ground Elevation: 366 Feet Date Excavated: 03-16-2016 Depth Material Description Sample Ne %M Testing (ft) Loose, moist to wet, dark brown, silty SAND, with roots and fine organic material (Topsoil) I ----------------------------------------------------- Loose to mediwn dense, moist to wet, mottled gray-brown, silty SAND, some gravel, moderate iron oxide staining 2 (Weathered Glacial Till) 3 ----------------------------------------------------- Dense, moist, gray, silty SAND, some gravel (Glacial Till) 4 Hand Auger completed at 3.5 feet on 3/16/2016. Very slight perched groundwater seepage observed at 3 feet at time of exploration. No caving observed. 5 6 7 8 9 10 11 12 Note: Ne is the Dynamic Cone Penetrometer blow count per ASTM Special Publication #399. PPER GEO ASSOCIATI , LLC 19023 361h Avenue West, Suite D, Lynnwood, Washington 98036 HAND AUGER HA-3 Project: Children's Institute Location: See Site And Exploration Plan, Figure 2 Project No: 1601.01 Approximate Ground Elevation: 374 Feet Date Excavated: 03-16-2016 Depth Material Description Sample Ne %M Testing (ft) Loose, moist to wet, dark brown, silty SAND, with roots and fine organic material (Topsoil) I ----------------------------------------------------- Medium dense, moist, gray-brown SAND, some silt and gravel (Weathered Glacial Outwash) S-1@1.5' 2 3 4 Hand Auger completed at 3.5 feet on 3/16/2016. No groundwater seepage observed at time of exploration. Slight caving observed below 12 inches. 5 6 7 8 9 10 11 12 Note: Ne is the Dynamic Cone Penetrometer blow count per ASTM Special Publication #399. ZIPPr GEO ASSOCIATES, LL 19023 36m Avenue West, Suite D, Lynnwood, Washington 98036 HAND AUGER HA-4 Project: Children's Institute Location: See Site And Exploration Plan, Figure 2 Project No: 1601.01 Approximate Ground Elevation: 398 Feet Date Excavated: 03-16-2016 Depth Material Description Sample Ne o/eM Testing (ft) Loose, moist to wet, dark brown, silty SAND, with roots and fine organic material (Topsoil) I -----------------------------------------------------Mediwn dense, moist, gray-brown, fine to mediwn SAND, some silt (Weathered Glacial Outwash) 2 S-1@2' 3 4 5 6 Hand Auger completed at 6 feet on 3/16/2016. 7 No groundwater seepage observed at time of exploration. No caving observed. 8 9 10 11 12 Note: Ne is the Dynamic Cone Penetrometer blow count per ASTM Special Publication #399.