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HomeMy WebLinkAboutSR_ERC Report_Cedars_at_the_Highlands_180820.pdfDEPARTMENT OF COMMUNITY AND ECONOMIC DEVELOPMENT ERC REPORT 17-000189 ENVIRONMENTAL REVIEW COMMITTEE REPORT ERC MEETING DATE: August 22, 2017 Project Name: Cedar at the Highlands Preliminary Plat Project Number: LUA17-000189, ECF, PP, MOD, TUP Project Manager: Alex Morganroth, Associate Planner Owner: Gerald C. Smith, 14120 160th Ave SE, Renton, WA 98059 Applicant/Contact: Harbour Homes, LLC, 400 N. 34th ST., Suite 300 Project Location: 14120 160th Ave SE, Renton, WA 98059 Project Summary: The applicant is requesting Preliminary Plat approval and Environmental Threshold Determination (SEPA) for a proposed 13-lot subdivision. The project site is 195,531 square feet (4.49 acres) and is located at 14120 160th Ave SE. The project site is located in the Residential-4 (R-4) zoning designation. The proposed single-family residential lots range in size from 9,000 square feet to 17,565 square feet with an overall proposed density of 3.36 dwellings per acre. The applicant has requested a Temporary Use Permit to allow for two existing outbuildings to remain for a period of five years. The structures are located across proposed Lots 9 and 10. Additional proposed improvements include a 3,195 sq. ft. storm drainage tract (Tract A) in the southeast corner of the site along the unimproved 162nd Ave SE right-of-way (ROW) frontage, a 3,500 sq. ft. tree retention tract (Tract C) along the north property line adjacent to lots 11 and 12, and a 20,246 native growth protection tract (Tract B) in the north-east corner to encompass the proposed 75-foot reduced wetland buffer. The proposed lots would be served by a new public residential access street off of 160th Ave SE and a cul-de-sac would be provided near the eastern end of the property. Proposed lots would be served by sanitary sewer along the new street that would connect to an existing main within 160th Ave SE. Proposed lots would be served by a new water main extending from 160th Ave SE along the new street. Construction of the proposed subdivision infrastructure improvements would result in approximately 5,000 cubic yards of cut and 8,000 cubic yards of fill. A Type Ns stream and Category III wetlands are mapped on the site according to COR maps and a Wetlands Report submitted by the applicant. Slopes on the site generally fall to the southeast across the property at a range of 0-20%. Soils consist of Alderwood gravelly sandy loam (AgC). The applicant has proposed to retain approximately 35 of the 284 significant trees onsite. The applicant has submitted a Technical Information Report, Arborist Report, a Critical Areas Determination and a Geotechnical Engineering Study with the application. Site Area: 195,531 SF (4.49 acres) STAFF RECOMMENDATION: Staff Recommends that the Environmental Review Committee issue a Determination of Non-Significance - Mitigated (DNS-M). City of Renton Department of Community & Economic Development Environmental Review Committee Report CEDARS AT THE HIGHLANDS PRELIMINARY PLAT LUA17-000189, ECF, PP, MOD Report of August 20, 2018 Page 2 of 9 ERC REPORT 17-000189 Project Location Map: PART ONE: PROJECT DESCRIPTION / BACKGROUND The applicant is requesting Preliminary Plat approval and Environmental (SEPA) Review for the subdivision of one parcel totaling 4.49-acres located at 14120 160th Ave SE, within the SE ¼ of Section 14, Township 23 North, Range 5 East, in King County, Washington. (Exhibit 2). The specific parcel number is 1457500110. The project site formerly consisted of two associated shops/out-buildings used by the property owner, and open space. The site is proposed to be subdivided into 13 single-family residential lots, associated road and utility improvements, a storm water tract, a tree retention tract, and a natural growth protection tract. The storm water tract would consist of a storm water vault to treat runoff on the eastern side of the site. The subject site is bordered by single-family homes around all sides of the property. Located to the north of the site is SE 136th St, SE 142nd Pl is to the south, 162nd Ave SE is to the east, and 160th Ave SE is to the west. Table 1. Surrounding Land Use and Zoning Location Comprehensive Land Use Zoning Site Residential Low Density (RLD) Residential-4 Dwelling Units Per Net Acre (R-4) North Residential Low Density (RLD) Residential-4 Dwelling Units Per Net Acre (R-4) South Residential Low Density (RLD) Residential-4 Dwelling Units Per Net Acre (R-4) East Residential Low Density (RLD) Residential-4 Dwelling Units Per Net Acre (R-4) West Residential Low Density (RLD) Residential-4 Dwelling Units Per Net Acre (R-4) The 4.49-acre project site is located within the Residential - 4 (R-4) dwelling units per net acre zoning classification. The net density of the project is 3.66 dwelling units per net acre (14 / 3.83 net acres = 3.66 du/acre) and the 14 lots City of Renton Department of Community & Economic Development Environmental Review Committee Report CEDARS AT THE HIGHLANDS PRELIMINARY PLAT LUA17-000189, ECF, PP, MOD Report of August 20, 2018 Page 3 of 9 ERC REPORT 17-000189 would range in size from 9,001 square feet to 16,694 square feet with an average lot size of 10,154 square feet (Exhibit 2). The property has two (2) existing out-buildings used by the property for storage. The applicant has submitted a Temporary Use Permit to retain the two existing buildings on proposed Lot 9 and Lot 10 for approximately five years – after which time the lots would be developed with two new single-family homes. Access to the site would be provided via a new road (Road A), near the east-west centerline of the site, which would extend from 160th Ave SE to terminate in a cul-de-sac on the eastern end of the site. The section of 162nd Ave SE ROW bordering the proposed site to the east is currently unimproved. A pedestrian pathway is located in the ROW and extends from SE 144th St to the Liberty Gardens subdivision, north-east of the subject site, and transitions from a pedestrian pathway into a paved roadway. The applicant is proposing a 53-foot wide residential access road for Road A. Road A, measured from centerline of 156th Ave SE to the center of the proposed cul-de-sac, measures approximately 525 feet in length. The proposed subdivision would include frontage improvements on 160th Ave SE to add concrete vertical curb, gutter, sidewalk, and planter strip. The applicant has proposed an internal residential access road with a 53-foot ROW that would include concrete vertical curb, gutter, sidewalk, and planter strip, and would culminate in a cul-de-sac with a 90-foot diameter. The applicant has submitted a street modification request for 162th Ave SE proposing no improvements or ROW dedication due to the presence of critical areas, steep topography, and existing pedestrian trail connecting the Liberty Garden subdivision to SE 144th St. The developed site would provide Basic Water Quality treatment in addition to meeting the City’s Matching Forested Conditions for flow control per the 2017 Renton Surface Water Design Manual (RSWDM). Water quality storm volumes are proposed to be treated with a Contech stormfilter and storm detention vault located in the southwest corner of the site. The property includes 284 significant trees comprised of a mixture of native species. The site generally falls to the southeast across the property at a range of 0-20% with a total fall of approximately 10 feet. Soils consist of Alderwood gravelly sandy loam (AgC). According to the Geotechnical Engineering Study prepared by Earth Solutions NW, LLC (Exhibit 10), the native soils encountered at the test pit locations included four to ten inches of topsoil overlying 0.5 to 11 feet of medium dense silty sand with gravel. The findings were consistent with the makeup of glacial till deposits on the western portion of the site and glaciomarine deposit overlain by glacial outwash in the eastern portion of the site. The geotechnical study found that the proposed residential development is feasible from a geotechnical standpoint. According to the Technical Information Report prepared by D.R. Strong Consulting Engineers, the site possesses a moderate to severe susceptibility to erosion activity. PART TWO: ENVIRONMENTAL REVIEW In compliance with RCW 43.21C.240, the following environmental (SEPA) review addresses only those project impacts that are not adequately addressed under existing development standards and environmental regulations. A. Environmental Threshold Recommendation Based on analysis of probable impacts from the proposal, staff recommends that the Responsible Officials: Issue a DNS-M with a 14-day Appeal Period. B. Mitigation Measures 1. Project construction shall comply with the recommendations found in the submitted geotechnical support prepared by Earthworks NW, dated February 23, 2017. C. Exhibits Exhibit 1 ERC Report Exhibit 2 Cedars at the Highlands Preliminary Plat Plan Exhibit 3 Neighborhood Detail Map Exhibit 4 Topographic Map Exhibit 5 Preliminary Landscaping and Tree Retention Plans (Sheets 1-15) City of Renton Department of Community & Economic Development Environmental Review Committee Report CEDARS AT THE HIGHLANDS PRELIMINARY PLAT LUA17-000189, ECF, PP, MOD Report of August 20, 2018 Page 4 of 9 ERC REPORT 17-000189 Exhibit 6 Preliminary Grading Plan Exhibit 7 Preliminary Utility Plan Exhibit 8 Preliminary Drainage Control Plan Exhibit 9 Preliminary Road Profiles Exhibit 10 Geotechnical Engineering Study prepared by Earthworks NW, LLC (dated February 2, 2017) Exhibit 11 Preliminary Technical Information Report prepared DR Strong (dated June 29, 2018) Exhibit 12 Arborist Report prepared by Greenforest Incorporated (dated March 20, 2017). Exhibit 13 Tree Retention Worksheet Exhibit 14 Critical Areas Determination Report prepared by Sewall Wetland Consulting, LLC (dated March 28, 2017) Exhibit 15 Revised Critical Areas Determination Report prepared by Sewall Wetland Consulting (dated October 3, 2017) Exhibit 16 Secondary Review, Wetlands Report prepared by Otak (dated December 6, 2017) Exhibit 17 Technical Memo prepared by Soundview Consultants (dated January 31, 2018) Exhibit 18 Technical Memo 2 prepared by Soundview Consultants (dated April 4, 2018) Exhibit 19 Response Memo prepared by Otak (dated April 16, 2018) Exhibit 20 Wetlands Buffer Mitigation Plan prepared by Soundview Consultants (dated June 20, 2018) Exhibit 21 Traffic Study prepared by TraffEx (dated March 21, 2017) Exhibit 22 Construction Mitigation Description Exhibit 23 Advisory Notes to Applicant D. Environmental Impacts The proposal was circulated and reviewed by various city departments and divisions to determine whether the applicant has adequately identified and addressed environmental impacts anticipated to occur in conjunction with the proposed development. Staff reviewers have identified that the proposal is likely to have the following probable impacts: 1. Earth Impacts: No geo-hazards are mapped on the site. A Geotechnical Engineering Study prepared by Earth Solutions NW, LLC. (dated February 23, 2017; Exhibit 10) was submitted with the project application. In addition, a Geotechnical Infiltration Evaluation prepared by Earth Solutions NW, LLC (dated July 13, 2017; Exhibit 10) was also submitted. The site topography descends gently from the northwest corner to the southeast corner of the site with an estimated total elevation change of 10 feet across the site. The steepest slope identified by the applicant was approximately 20 percent. The study indicated that conventional spread and continuous footings may be utilized across the site, but additional compaction or replacement with structural fill may be required for areas of loose soil on the western portion of the site. The applicant indicates that the estimated quantities for structural fill onsite would be approximately 5,000 cubic yards of cut and 8,000 cubic yards of fill. This grading would be required for the construction of required plat improvements and new single family residences. Temporary erosion and sedimentation control measures would be implemented during construction including, but not limited to, Best Management Practices (BMPs) such as site preparation and grading during the drier summer and early fall months, installing siltation control fencing around the work areas, installing a temporary sedimentation pond prior to beginning earthwork activities, and establishing a quarry spall construction entrances in accordance with City of Renton requirements (Exhibit 21). In January of 2017, a total of five (5) test pits (TP-1 through TP-5) were excavated across the project site with a trackhoe to approximate depths of 11.5 feet below existing site grades. Topsoil and various organics were encountered within the upper 4 to 10 inches of existing grades at the test pit (TP) locations. Conditions underlying the top soil vary depending on test pit locations. In two of the test pits, fill was observed ranging in thickness from 1.5 to 4 feet (TP-2 and TP-5). During the subsurface exploration tests, groundwater seepage was encountered, with especially heavy seepage at TP-5. The study indicates that shallow perched City of Renton Department of Community & Economic Development Environmental Review Committee Report CEDARS AT THE HIGHLANDS PRELIMINARY PLAT LUA17-000189, ECF, PP, MOD Report of August 20, 2018 Page 5 of 9 ERC REPORT 17-000189 groundwater seepage zones should be anticipated within site excavations, particularly during the winter, spring, and early summer months. The report noted that contractors should be prepared to dewater during vault and utility excavations, especially if the work is being completed during the wet season. In the Geotechnical Infiltration Evaluation, Earth Solutions NW LLC evaluated onsite soils for infiltration using the “Pilot Infiltration Testing” at four locations. The Pilot Infiltration Test is an approved infiltration testing procedure per Section C.1.3 of the RSWDM. No infiltration was observed in three out of the four locations. At the fourth location (TP-104, located in the southeast portion of the site) there was limited infiltration however advancing the test pit deeper than the infiltration test depth resulted in an observed confining layer of silt that limits the capacity of the underlying subgrade to infiltrate. The report concluded that the confining soil layer can result in lateral migration of water which can create flooding rated issues on the neighboring properties to the south of the subject site, since they are sited lower in the elevation than the subject property. The report concludes that infiltration of stormwater and low impact development (LID) techniques at the site are infeasible. Per the City of Renton (COR) Maps, the site does not contain landslide hazard potential. According to the geotechnical engineer, the site possesses a low susceptibility to landslide due to shallow site slopes of less than 15%. The provided reports conclude that the construction of the proposed residential development is feasible from a geotechnical standpoint. The proposed residential buildings can be supported on conventional continuous and spread footings bearing on competent native soils, re-compacted native soils, or new structural fill. Based on the soil conditions encountered at the test sites, competent native soils suitable for the support of foundations should be generally encountered at depths of one to three feet below existing grades. Pavement and floor slabs can be similarly supported. The ability to use native soil as structural fill will ultimately depend on its moisture content and the weather conditions at the time of construction. The primary geotechnical considerations submitted in the geotechnical report include foundation support, slab-on-grade subgrade support, installation of vapor barriers, the suitability of using onsite soils as structural fill, and construction of the vault. To mitigate for potential impacts the project proposal could have on the site resulting from project construction, staff recommends as a mitigation measure that the project construction comply with the recommendations found in the submitted geotechnical support prepared by Earthworks NW, dated February 23, 2017 or an update report submitted at a later date. Mitigation Measures: Project construction shall comply with the recommendations found in the submitted geotechnical support prepared by Earthworks NW, dated February 23, 2017 or an update report submitted at a later date. Nexus: SEPA Environmental Review, RMC 4-4-060 Grading, Excavation and Mining Regulations. 2. Water a. Wetlands, Streams, Lakes Impacts: According to the City of Renton COR Maps there are existing wetlands and a Type NS stream on the northeast portion of the site and immediately off-site to the north. A Critical Areas Determination Report prepared by Sewall Wetland Consulting, LLC (dated March 28, 2017; Exhibit 14) with the original application identified the Type NS stream that originates from the parcel to the north, continues across the northeast corner of the subject site, and exits into the unimproved ROW to the east of the site. During review of the report, staff determined that the report did not adequately address the wetlands located to the north (described as Wetlands A in the report) of the project site on parcel #1457500106. These wetlands were identified in a wetlands report completed by the same consultant in 2013 as part of the submittal for Mindy’s Place Short Plat. A revised Critical Areas Study prepared by Sewall (Dated October 3, 2017; Exhibit 15) was submitted at staff’s request. The revised study delineated the off-site wetlands to the north of the site and classified the wetlands as a Category II “depressional” system. The report reiterated the presence of the Type NS stream, requiring a 50 foot buffer, but concluded that no wetlands were located on the project site. After reviewing the new assessment against data in COR maps, staff continued to find inconsistencies between the City of Renton Department of Community & Economic Development Environmental Review Committee Report CEDARS AT THE HIGHLANDS PRELIMINARY PLAT LUA17-000189, ECF, PP, MOD Report of August 20, 2018 Page 6 of 9 ERC REPORT 17-000189 two Critical Area Determinations submitted by the applicant and the study completed in 2012 for Mindy’s Place. Inconsistencies were primarily related to the delineation of wetlands on the project site. Although the Sewall studies showed the wetlands ending at the property line, staff was concerned that the linear system likely followed the path of the Type NS stream and continued SE across the project site and unimproved public ROW. In order to resolve the inconsistency issues and obtain accurate information on the wetlands, Otak was hired as a secondary reviewer of the on-site and off-site wetlands. At the City’s request, Otak submitted a new report (Dated December 6, 2017; Exhibit 16) to staff, which contained findings and analysis based on a November 20, 2017 site visit completed by Otak staff. The report conclude d that the original wetlands categorization of “Wetlands A” on the northeast corner of the site in the report submitted by Sewall Wetland Consulting was calculated incorrectly. Otak recommended multiple revisions to the initial determination, including a re-categorization of Wetlands A from a Category II “depressional” to a Category III “depressional” wetlands system with a habitat score of 4, requiring a 100 foot buffer per RMC 4-3-050. Otak also recommended a re-evaluation of the delineation due to the presense of wetlands onto the project site. In early February of 2018, a technical memo prepared by Soundview Consultants on behalf of the applicant was submitted to staff (Dated January 31, 2018; Exhibit 17). The memorandum served as a rebuttal to the report prepared by Otak in December and concluded that the wetlands should be classified as a Category II “sloped” wetlands system with a habitat score of 4, requiring a 50-foot buffer per RMC 4-3-050. After submitting the report, Soundview Consultants requested a site visit in order to discuss some of the issues in- person. On March 14, 2018, representatives from Otak, Soundview Consultants, the City, and Harbour Homes met and walked the site. After the site visit, Soundview Consultants submitted another technical memo reiterating their support for their original determination (Dated April 4, 2018; Exhibit 18). After receipt of the Soundview memo, Otak submitted a final memorandum maintaining their position on the classification (Dated April 16, 2018; Exhibit 19). Based on the classification of Wetlands A as a Category III wetlands system with a moderate habitat score (4), a 100-foot buffer with a 15 foot structure setback is required per RMC 4-3-050. A 50 foot buffer is required for a Type NS stream per RMC 4-3-050. Due to the location of the stream near the center of the wetlands area, the required 100-foot buffer for the wetlands would meet the buffer requirements of both the wetlands and stream (50 feet). The applicant has proposed a reduced buffer of 75 feet over an area of approximately 15,460 sq. ft. RMC 4- 3-050 gives the administrator the ability to authorize a 25% reduction in the wetlands buffer if certain conditions are met. The buffer in its current state is highly disturbed and includes mowed lawn, junk cars and debris, and a significant amount of Himalayan blackberry. The wetlands report includes a mitigation plan that includes the removal of junk cars and debris, the eventual removal of the existing building encroaching on the buffer, and the installation of native plantings (Exhibit 21). The plan identifies the types of species proposed for planting in the buffer, but does not identify the number of each plant. The applicant will need to submit a revised mitigation plan indicating the number and location of each plant species in the wetland buffer, in addition to a phasing plan for project mitigation to be completed after the removal of the barn. Staff anticipates an interim mitigation plan and a final mitigation plan that would completely restore the buffer at a later date after the barn is removed. Temporary impacts to the wetlands buffer are anticipated due to the construction of the vault directly adjacent to the southern edge of the buffer. The applicant will need to submit an updated study prior to construction permit submittal, addressing the temporary impacts and the methods used to mitigate for them. Native plantings proposed for the buffer would include Sitka spruce, Douglas fir, Western red cedar, and a variety of native shrubs and grasses, including but not limited to Red-twig dogwood, Salal, Salmonberry, Western swordfern, Streamside lupine, and Spike bentgrass. The entire buffer area would be placed in a tract (Tract B) with a Native Growth Protection Easement on top of the entire buffer and wetlands area. The mitigation plan report concludes that the wetland hydrology and water quality function would see significant improvements if the plan is implemented. Due to the degraded state of the existing wetland buffer and anticipated environmental lift, staff is supportive of the buffer reduction, provided the restoration work is City of Renton Department of Community & Economic Development Environmental Review Committee Report CEDARS AT THE HIGHLANDS PRELIMINARY PLAT LUA17-000189, ECF, PP, MOD Report of August 20, 2018 Page 7 of 9 ERC REPORT 17-000189 completed in accordance with a final approved mitigation plan. Provided the project complies with the Critical Areas regulations staff does not anticipate any impacts to the wetlands. Mitigation Measures: Nexus: Not applicable b. Storm Water Impacts: The applicant submitted a Preliminary Technical Information Report (TIR), prepared by DR Strong (dated June 29, 2018; Exhibit 11). Based on the TIR, the project contains greater than 2,000 sq. ft. of new impervious surface and therefore a Full Drainage Review is required pursuant to the 2017 Renton Surface Water Design Manual (RSWDM). All nine core requirements and six special requirements were addressed in the report. Based on the City’s flow control map, the site falls within the Flow Control Duration Standard matching Forested Site Conditions. The project is subject to Basic Water Quality treatment standards in order to satisfy Core Requirement #8. The applicant has proposed a detention vault on the east side of site. The vault would be sized to the City’s Flow Control Standard Level 3 in order to mitigate potential downstream drainage issues. The project site matches the 100-year peak discharge rate to the pre-developed 100-year peak discharge rate. The project is subject to the on-site BMP requirements found in Core Requirement #9. According to the TIR, full dispersion and full infiltration are not feasible on-site BMPs as the minimum design requirements cannot be met. Development Engineering staff believe that basic dispersion may be a viable BMP for some lots within the development. If feasible, basic dispersion should be implemented to the maximum extent feasible which may be more than 10% of the total lot area. It is anticipated that the City’s currently adopted 2017 City of Renton Surface Water Design Manual would mitigate for any potential surface water impacts that could be generated by the project proposal, therefore no further mitigation is recommended at this time. Mitigation Measures: No further mitigation required. Nexus: Not applicable 3. Trees and Vegetation Impacts: The applicant submitted an Arborist Report prepared by Greenforest Incorporated (dated March 20, 2017). The report noted that the property is covered with a weedy and unmaintained understory with a native tree canopy created by the 284 trees located on the site. Several larger trees are located around the project site, including Western red cedars, Douglas firs, and Bigleaf maples (Exhibit 5). The Arborist Report identified 19 landmark trees, 170 significant trees, 85 dangerous trees, and 10 trees within the critical area buffer on the parcel proposed to be developed (Exhibit 12). Approximately 41 of the identified trees were located within the proposed road network. The minimum tree retention requirement is thirty percent (30%) in the R-4 zone. Therefore, the applicant must retain at least 47 trees. After street and critical area deductions, the applicant is proposing to retain 35 trees, or twelve (12) trees less than the amount required by code. Per RMC 4-4-130, a replacement ratio of 12 inches per tree is required for each tree less than the total required to be retained. All retained trees (i.e., protected trees) would be required to be protected during construction pursuant to RMC 4-4-130. The applicant is proposing to replant the subdivision with 48 three-inch caliper trees for a total of 144 caliper inches. Proposed species of trees include Redmond Linden, Western red-cedar, Princeton Elm, Douglas fir, and variety of trees from the Maple family. According the applicants tree planting, the majority of the proposed onsite replacement trees would be used to meet the frontage landscaping and planter strip requirements and includes street trees, front yard trees, and trees near the storm water vault in Tract A. Per RMC 4-4-130, only up to 50% of trees required pursuant to the landscape code may contribute to the replacement tree requirement. Therefore additional trees totaling at least 72 caliper inches must be added in order to meet the tree replacement requirement of 144 inches. A new plat plan layout was received on August 14, 2018 which relocated the vault and adjusted the lots along the south side of the proposed new Road A. City of Renton Department of Community & Economic Development Environmental Review Committee Report CEDARS AT THE HIGHLANDS PRELIMINARY PLAT LUA17-000189, ECF, PP, MOD Report of August 20, 2018 Page 8 of 9 ERC REPORT 17-000189 An updated tree plan was not included in the re-submittal. The updated tree plan will be required to be provided prior to the public hearing and will be reviewed for compliance with the 30% retention standards. The applicant has proposed a 3,500 sq. ft. tree tract (Tract C) to the north of proposed lots 11 and 10. The proposed tract contains two landmark trees and four mature significant trees. Three trees are proposed for retention in the tract including a 58” DBH Western red-cedar, a 31” DBH Western red-cedar, and a 25” DBH Western red-cedar. Three of the six trees were classified by the arborist as dangerous and are proposed for removal. The sixth tree, a 24” DBH Western red-cedar near the eastern edge of the tract is shown as retained in the Arborist Report but is shown as removed in the Tree Retention plan. If healthy, the tree should be retained and the plans should be updated to be consistent. The applicant has proposed to retain all trees in the Critical Area Buffer and install 24 new trees including Sitka spruce, Douglas fir, and Western red cedar. However, due to the update plan received on August 14, 2018, it is anticipated that trees will be removed from the wetland buffer as a result of temporary construction impacts for the installation of the vault. These impacts are required to be mitigated per the City’s critical areas regulations, see section 2.a. Wetlands, Streams, and Lakes, above. An updated planting plan should be submitted and include the exact quantities of each species proposed for the buffer. Where there is insufficient ROW space or no public frontage, street trees are required in the front yard(s). A final detailed landscape plan must be submitted and approved prior to issuance of the street and utility construction permits. Mitigation Measures: No further mitigation required Nexus: Not applicable 4. Transportation Impacts: Primary access to the site would be provided via a new dead-end public street off of 160th Ave SE, as shown in the updated preliminary site plan (Exhibit 2). The new Residential Access Road (Road A) would be approximately 550 feet in length and would terminate at a cul-de-sac on the east side of the property. The applicant is proposing a cross-section that includes a ROW width of 53 feet with 26 feet of pavement, 8 -foot wide landscaped planters, 5-foot wide sidewalks, and 0.5-foot wide curbs. The roadway would provide two (2) 10-foot travel lanes and one (1) 6-foot parking lane. The undergrounding of all utilities is required. 160th Ave SE is classified as a Residential Access Road. The existing ROW width is approximately 60 feet. To meet the City’s complete street standards, RMC 4-6-060, a minimum ROW width of 53 feet for a Residential Access Road is required. In addition to the travel lanes, a Residential Access Road ROW requires 0.5-foot wide curbs, 8-foot wide landscaped planters, and 5-foot wide sidewalks. Street trees, storm drainage improvements and undergrounding of any overhead utility lines along the frontage of the property would be required along the project frontage. No dedication of ROW would be required along the project side of 160th Ave SE. 162nd Ave SE, an improved right-of-way, is located along the east property line and is classified as a Residential Access Road with approximately 60 feet of ROW. The applicant has submitted a street modification request to allow the existing unimproved street and frontage section to remain. According to the applicant, the modification was requested due to the presence of a stream and wetlands in the unimproved right-of-way. The applicant contends that improving the road would significantly impact the critical areas and buffers and therefore negatively impact the environment. TraffEx has calculated that the project would generate a total of 10 new vehicle trips per hour in the AM peak period and 13 new vehicle trips per hour in the PM peak period (Exhibit 21). The City does not require Traffic Impact Analyses for developments if both new AM and PM peak period vehicle trips are less than 20. Adequate sight distance would be provided at the intersection of the proposed new street and 160th Ave SE. It is not anticipated that the proposed project would adversely impact the City of Renton’s street system subject to the payment of code-required impact fees and the construction of code-required frontage improvements (Exhibit 23). The fee, as determined by the Renton Municipal Code at the time of building permit issuance shall be payable to the City. City of Renton Department of Community & Economic Development Environmental Review Committee Report CEDARS AT THE HIGHLANDS PRELIMINARY PLAT LUA17-000189, ECF, PP, MOD Report of August 20, 2018 Page 9 of 9 ERC REPORT 17-000189 A concurrency recommendation will be provided in the staff report to the Hearing Examiner based upon the test of the citywide Transportation Plan, consideration of growth levels included in the LOS‐tested Transportation Plan, payment of a Transportation Mitigation Fee, and an application of site specific mitigation. The development will have to meet the City of Renton concurrency requirements. Mitigation Measures: No further mitigation required. Nexus: Not applicable 2. Fire & Police Impacts: Police and Fire Prevention staff indicated that sufficient resources exist to furnish services to the proposed development subject to the construction of code-required improvements and the payment of code- required impact fees (Exhibit 23). Mitigation Measures: No further mitigation required. Nexus: Not applicable E. Comments of Reviewing Departments The proposal has been circulated to City Department and Division Reviewers. Where applicable, their comments have been incorporated into the text of this report and/or listed under Exhibit 22 “Advisory Notes to Applicant.” Copies of all Review Comments are contained in the Official File and may be attached to this report. The Environmental Determination 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). Environmental Determination Appeal Process: Appeals of the environmental determination must be filed in writing together with the required fee to: Hearing Examiner, City of Renton, 1055 South Grady Way, Renton, WA 98057, on or before 5:00 p.m. on September 7, 2017. RMC 4-8-110 governs appeals to the Hearing Examiner and additional information regarding the appeal process may be obtained from the City Clerk’s Office, Renton City Hall – 7th Floor, (425) 430-6510. CITY OF RENTON DEPARTMENT OF COMMUNITY AND ECONOMIC DEVELOPMENT STAFF REPORT TO THE ENVIRONMENTAL REVIEW COMMITTEE EXHIBITS Project Name: Cedars at the Highlands Preliminary Plat Project Number: LUA17-000189, ECF, PP, MOD Date of Meeting August 20, 2018 Staff Contact Alex Morganroth Associate Planner Project Contact/Applicant Gerald C. Smith 14120 160th Ave SE Renton, WA 98059 Project Location 14120 160th Ave SE, Renton, WA 98059 The following exhibits are included with the ERC Report: Exhibit 1: Environmental Review Committee (ERC) Report Exhibit 2: Cedars at the Highlands Preliminary Plat Plan Exhibit 3: Neighborhood Detail Map Exhibit 4: Topographic Map Exhibit 5: Preliminary Landscaping Plans and Tree Retention Plans (Sheets 1-15) Exhibit 6: Preliminary Grading Plan Exhibit 7: Preliminary Utility Plan Exhibit 8: Preliminary Drainage Control Plan Exhibit 9: Preliminary Road Profiles Exhibit 10: Geotechnical Engineering Study prepared by Earthworks NW, LLC (dated February 2, 2017) Exhibit 11: Preliminary Technical Information Report prepared DR Strong (dated June 29, 2018) Exhibit 12: Arborist Report prepared by Greenforest Incorporated (dated March 20, 2017). Exhibit 13: Tree Retention Worksheet Exhibit 14: Critical Areas Determination Report prepared by Sewall Wetland Consulting, LLC (dated March 28, 2017) Exhibit 15: Revised Critical Areas Determination Report prepared by Sewall Wetland Consulting (dated October 3, 2017) Exhibit 16: Secondary Review, Wetlands Report prepared by Otak (dated December 6, 2017) Exhibit 17: Technical Memo prepared by Soundview Consultants (dated January 31, 2018) Exhibit 18: Technical Memo 2 prepared by Soundview Consultants (dated April 4, 2018) Exhibit 19: Response Memo prepared by Otak (dated April 16, 2018) Exhibit 20: Wetlands Buffer Mitigation Plan prepared by Soundview Consultants (dated June 20, 2018) Exhibit 21: Traffic Study prepared by TraffEx (dated March 21, 2017) Exhibit 22: Construction Mitigation Description Exhibit 23: Advisory Notes to Applicant 0GRAPHIC SCALE1002004001 INCH = 200 FT.CEDARS AT THE HIGHLANDS14120 160TH AVENUE SERENTON, WASHINGTON 98056CEDARS AT THE HIGHLANDS CEDARS AT THE HIGHLANDS AAANNNNNNN LUA:U:DRS PROJECT NO. 16041A-NNNNNNNNSERISSEFORPINGOERDETSREENGINELA53232 OIETATHSOYSFOTGNIHASWIDEIPL.OCILAZNEIGHBORHOOD DETAIL MAP CEDARS AT THE HIGHLANDS14120 160TH AVENUE SERENTON, WASHINGTON 98059CEDARS AT THE HIGHLANDS CEDARS AT THE HIGHLANDS AAANNNNNNN LUA:U:DRS PROJECT NO. 16041A-NNNNNNNNSERISSEFORPINGOERDETSREENGINELA53232 OIETATHSOYSFOTGNIHASWIDEIPL.OCILAZPRELIMINARY PLAT0GRAPHIC SCALE20'40'80'1 INCH = 40 FT. CEDARS AT THE HIGHLANDS 14120 160TH AVENUE SE RENTON, WASHINGTON 98059 CEDARS AT THE HIGHLANDSCEDARS AT THE HIGHLANDSAAANNNNNNNLUA17-000189U:DRS PROJECT NO. 16041 A-NNNNNNN NSER ISS E FORP I N G O E R DETS REE N G INELA 53232 OIETATHSOY SF OT G NIHASWIDEIPL.O C ILAZPRELIMINARY PLAT 0 GRAPHIC SCALE 15'30'60' 1 INCH = 30 FT. CEDARS AT THE HIGHLANDS 14120 160TH AVENUE SE RENTON, WASHINGTON 98059 CEDARS AT THE HIGHLANDSCEDARS AT THE HIGHLANDSAAANNNNNNNLUA17-000189U:DRS PROJECT NO. 16041 A-NNNNNNN NSER ISS E FORP I N G O E R DETS REE N G INELA 53232 OIETATHSOY SF OT G NIHASWIDEIPL.O C ILAZPRELIMINARY PLAT 0 GRAPHIC SCALE 15'30'60' 1 INCH = 30 FT. CEDARS AT THE HIGHLANDS 14120 160TH AVENUE SE RENTON, WASHINGTON 98059 CEDARS AT THE HIGHLANDSCEDARS AT THE HIGHLANDSAAANNNNNNNLUA17-000189U:DRS PROJECT NO. 16041 A-NNNNNNN NSER ISS E FORP I N G O E R DETS REE N G INELA 53232 OIETATHSOY SF OT G NIHASWIDEIPL.O C ILAZPRELIMINARY PLAT 0 GRAPHIC SCALE 15'30'60' 1 INCH = 30 FT. CEDARS AT THE HIGHLANDS14120 160TH AVENUE SERENTON, WASHINGTON 98059CEDARS AT THE HIGHLANDS CEDARS AT THE HIGHLANDS AAANNNNNNN LUA:U:DRS PROJECT NO. 16041A-NNNNNNNNSERISSEFORPINGOERDETSREENGINELA53232 OIETATHSOYSFOTGNIHASWIDEIPL.OCILAZPRELIMINARY PLAT00HORIZONTALVERTICAL1020401 INCH = 20 FT.2.55101 INCH = 5 FT. EarthSolutionsNWLLC EarthSolutions NW LLC Geotechnical Engineering Geology Environmental Scientists Construction Monitoring 1805 -136th Place N.E.,Suite 201 Bellevue,WA 98005 (425)449-4704 Fax (425)449-4711 www.earthsolutionsnw.com GEOTECHNICAL ENGINEERING STUDY CEDARS AT THE HIGHLANDS 14120 -160th AVENUE SOUTHEAST RENTON,WASHINGTON ES-5048 Drwn. Checked Date Date Proj.No. Plate Earth Solutions NWLLC Geotechnical Engineering,Construction Monitoring EarthSolutionsNWLLC EarthSolutions NW LLC and Environmental Sciences Vicinity Map Cedars at the Highlands Renton,Washington MRS SHA 02/10/2017 Feb.2017 5048 1 NORTH NOTE:This plate may contain areas of color.ESNW cannot be responsible for any subsequent misinterpretation of the information resulting from black &white reproductions of this plate. Reference: King County,Washington Map 657 By The Thomas Guide Rand McNally 32nd Edition SITE Drwn. Checked Date Date Proj.No. Plate Earth Solutions NWLLC Geotechnical Engineering,Construction Monitoring and Environmental Sciences EarthSolutionsNWLLC EarthSolutions NW LLC RETAINING WALL DRAINAGE DETAIL Cedar of the Highlands Renton,Washington MRS SHA 02/13/2017 Feb.2017 5048 3 NOTES: Free Draining Backfill should consist of soil having less than 5 percent fines. Percent passing #4 should be 25 to 75 percent. Sheet Drain may be feasible in lieu of Free Draining Backfill,per ESNW recommendations. Drain Pipe should consist of perforated, rigid PVC Pipe surrounded with 1" Drain Rock. LEGEND: Free Draining Structural Backfill 1 inch Drain Rock 18"Min. Structural Fill Perforated Drain Pipe (Surround In Drain Rock) SCHEMATIC ONLY -NOT TO SCALE NOT A CONSTRUCTION DRAWING Drwn. Checked Date Date Proj.No. Plate Earth Solutions NWLLC Geotechnical Engineering,Construction Monitoring and Environmental Sciences EarthSolutionsNWLLC EarthSolutions NW LLC FOOTING DRAIN DETAIL Slope Perforated Rigid Drain Pipe (Surround with 1"Rock) 18"(Min.) NOTES: Do NOT tie roof downspouts to Footing Drain. Surface Seal to consist of 12"of less permeable,suitable soil.Slope away from building. LEGEND: Surface Seal;native soil or other low permeability material. 1"Drain Rock SCHEMATIC ONLY -NOT TO SCALE NOT A CONSTRUCTION DRAW ING Cedar of the Highlands Renton,Washington MRS SHA 02/13/2017 Feb.2017 5048 4 2018 D. R. STRONG Consulting Engineers Inc. Cedars at the Highlands Technical Information Report Renton, Washington TECHNICAL INFORMATION REPORT for CEDARS AT THE HIGHLANDS PRELIMINARY PLAT 14120 160th Avenue SE, Renton, Washington ___ ____________________________________________________________________________ DRS Project No. 16041 Renton File No. PRE16-000524 Applicant Jamie Walter Harbour Homes, LLC 400 North 34th Street, Suite 300 Seattle, WA 98103 Report Prepared by D. R. STRONG Consulting Engineers, Inc. 620 7th Avenue Kirkland, WA 98033 (425) 827-3063 Report Issue Date June 29, 2018 2018 D. R. STRONG Consulting Engineers Inc. Cedars at the Highlands Technical Information Report Renton, Washington TECHNICAL INFORMATION REPORT CEDARS AT THE HIGHLANDS PLAT TABLE OF CONTENTS SECTION I ...................................................................................................................... 4 Project Overview ......................................................................................................... 4 Predeveloped Site Conditions ..................................................................................... 4 Developed Site Conditions .......................................................................................... 4 SECTION II ................................................................................................................... 16 Conditions and Requirements Summary ................................................................... 16 Conditions of Approval............................................................................................... 18 SECTION III .................................................................................................................. 19 Off-Site Analysis ........................................................................................................ 19 Task 1: Define and Map Study Area ...................................................................... 19 Task 2: Resource Review ...................................................................................... 19 Task 3: Field Inspection ......................................................................................... 28 Task 4: Drainage System Description and Problem Descriptions .......................... 29 Task 5: Mitigation of Existing or Potential Problems .............................................. 30 SECTION IV .................................................................................................................. 36 Flow Control, Low Impact Development (LID) and Water Quality Facility Analysis and Design .................................................................................................. 36 Existing Site Hydrology .......................................................................................... 36 Developed Site Hydrology ...................................................................................... 38 Performance Standards ............................................................................................. 42 Flow Control System ................................................................................................. 43 Water Quality Treatment System ............................................................................... 52 SECTION V ................................................................................................................... 54 Conveyance System Analysis and Design ................................................................ 54 SECTION VI .................................................................................................................. 56 Special Reports and Studies ..................................................................................... 56 SECTION VII ................................................................................................................. 57 Other Permits ............................................................................................................ 57 SECTION VIII ................................................................................................................ 58 CSWPPP Analysis and Design (Part A) .................................................................... 58 SWPPP Plan Design (Part B) .................................................................................... 58 SECTION IX .................................................................................................................. 60 Bond Quantities, Facility Summaries, and Declaration of Covenant .......................... 60 2018 D. R. STRONG Consulting Engineers Inc. Cedars at the Highlands Technical Information Report Renton, Washington SECTION X ................................................................................................................... 61 Operations and Maintenance Manual ........................................................................ 61 APPENDICES ............................................................................................................... 62 Appendix “A” Legal Description ................................................................................. 63 List of Figures Figure 1 TIR Worksheet .................................................................................................. 6 Figure 2 Site Location ................................................................................................... 11 Figure 3 Drainage Basins, Subbasins, and Site Characteristics ................................... 12 Figure 4 Soils ................................................................................................................ 13 Figure 5 City of Renton Topography Map ..................................................................... 20 Figure 6 City of Renton Coal Mine Hazard Areas Map ................................................. 21 Figure 7 City of Renton Flood Hazards Map ................................................................. 22 Figure 8 City of Renton Streams and Wetlands Map .................................................... 23 Figure 9 City of Renton Landslide Hazards Map ........................................................... 24 Figure 10 City of Renton Seismic Hazard Areas Map ................................................... 25 Figure 11 FEMA Map .................................................................................................... 26 Figure 12 King County iMap Drainage Complaints Map................................................ 27 Figure 13 Offsite Analysis Downstream Map ................................................................ 32 Figure 14 Offsite Analysis Downstream Table .............................................................. 33 Figure 15 Predeveloped Area Map ............................................................................... 37 Figure 16 Developed Area Map .................................................................................... 41 Figure 17 Detention & Water Quality Facility Details ..................................................... 53 2018 D. R. STRONG Consulting Engineers Inc. Page 4 Cedars at the Highlands Level One Downstream Analysis Renton, Washington SECTION I PROJECT OVERVIEW The Project is the proposed subdivision of one existing parcel zoned R-4 into 13 single- family residential lots, per the City of Renton’s (City) subdivision process. The Project is located at 14120 160th Avenue SE, Renton, Washington (Site) also known as Tax Parcel Number 145750-0110. The Project will meet the drainage requirements of the 2017 City of Renton Surface Water Design Manual (CORSWDM). PREDEVELOPED SITE CONDITIONS The total existing Site area is approximately 195,531 s.f. (4.49 acres). The Site is currently developed with a workshop, one shed and gravel driveways. The remainder of the Site is undeveloped forest covered with dense brush. An upstream tributary flows onto the Site on the western property line. This upstream flow is conveyed through a series of privately maintained channels and pipes to the southeasterly section of the Site where it is conveyed in a southerly direction by a swale. Project frontage on 160th Avenue SE drains onto the site; contributing to the upstream tributary area. The predeveloped site consists of a shallow grade to the southeast and is contained within one Threshold Discharge Area (TDA). There exists an unnamed Type Ns stream and category III wetland in the northeast corner of the Site. A natural ridge divides the Site into two distinct Natural Drainage Areas, NDA 1 and NDA 2. Runoff from NDA 1 is collected by the unnamed Type Ns stream and wetland and is conveyed in an easterly direction. NDA 2 results from runoff sheet flowing in a southeasterly direction and being collected by a swale located offsite. The two downstream paths convey stormwater in a southerly direction and converge in an existing detention pond within 1000’ downstream of the Site. This detention pond discharges into an existing conveyance system in SE 144th Street which then crosses underneath 154th Place SE where it outlets to Stewart Creek, a Class 3 stream. Stewart Creek outlets to Cedar River approximately 6,000 feet from the Site. DEVELOPED SITE CONDITIONS The applicant is seeking approval to subdivide 4.49 acres into 13 single–family residential lots (Project), with lot sizes ranging from approximately 9,000 s.f. to 16,911 s.f. The existing workshop on site will remain and will occupy one of the thirteen proposed lots under a 5-year temporary use permit. The proposed retained structure will account for approximately 8,400 s.f. of impervious area. After 5 years, this structure will be demolished and new single-family residences will be constructed. Therefore, the lots containing the existing structures will be modeled assuming build -out conditions per Renton Municipal Code zoning designations. The project is required to meet the City’s Flow Control Duration Standard – Matching Forested Conditions and Basic Water Quality treatment. However, the project will meet the City’s Flood Problem Flow Control Standard due to the existing downstream flooding problem within the drainage basin tributary to the SE 144 th Street storm system. This standard matches the developed Site flow durations to the flow durations of pre - 2018 D. R. STRONG Consulting Engineers Inc. Page 5 Cedars at the Highlands Level One Downstream Analysis Renton, Washington developed rates for forested (historical) site conditions from 50% of the 2-year peak flow up to the full 50-year peak flow. Also, developed peak discharge rates shall not exceed predeveloped peak discharge rates for the 2-,10-, and 100-year return periods. The Flood Problem Flow Control Standard and Basic Water Quality requirement will be met through the use of a detention vault preceding a StormFilter. The proposed impervious surface areas are as follows: half street frontage improvements consisting of a 5’ sidewalk along 160th AVE SE, Road A, the 13 new single-family residences and associated driveways, the existing structure to remain, and Tract A, the storm water detention facility, will generate approximately 87,641 s.f. of impervious area (2.012 acres). A area of non-target impervious surface along the north side of 160th AVE SE will be collected by the proposed detention facility. The facility has been designed with this area being proposed as a mitigation trade area. This area will be traded for a portion of the frontage that will not be collected by the proposed stormwater vault. Proposed Site landcover and surfaces are shown in Figure 16, Developed Site Conditions. (See Section IV). The Project proposes to combine runoff from NDA 2 and the target frontage into one detention system and discharge to the existing swale that is the natural discharge location for NDA 2. The Project is proposing to build a bypass conveyance system that will direct any pre-existing upstream runoff to its natural discharge location. Per Section 1.2.9.2.1 Small Lot BMP Requirements of the CORSWDM (Manual), projects are required to mitigate for impervious surfaces by use of Flow Control Best Management Practices (BMP’s). The Project’s lots fall within the requirements for small lots, as all lots are under 22,000 square feet. This requires all lots under 11,000 square feet to apply flow control BMPs to mitigate impervious areas equal to 10% of the total lot area. Lots 8 and 9 are required to mitigate impervious area equal to 20% of their total lot area due to lot areas greater than 11,000 square feet. The soils investigation summarized by the project geotechnical report are confined to the upper layers (up to 12 feet deep) of Site soils. The report indicates the presence of glacial till and glaciomarine deposits not conducive to infiltration. It is the recommendation of the geotechnical engineer to investigate alternative means of stormwater management. With limited native growth areas and negligible infiltration rates, the Project is proposing to utilize a combination of reduced impervious surface credits and basic dispersion to meet the small lot BMP requirements. (See Section IV). 2018 D. R. STRONG Consulting Engineers Inc. Page 6 Cedars at the Highlands Level One Downstream Analysis Renton, Washington FIGURE 1 TIR WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Part 2 PROJECT LOCATION AND DESCRIPTION Project Owner: Gerald Smith Phone: Address: 14120 160th Ave SE, Renton WA 98059 Project Engineer: Yoshio L. Piediscalzi, P.E. Company: D. R. STRONG Consulting Engineers Inc. Phone: (425) 827-3063 Project Name: Cedars at the Highlands City Permit#: PRE16-00524 Location: Township: 23 North Range: 05 East Section: 29 Site Address: 14120 160th Ave SE, Renton, WA 98059 Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS Landuse Services Subdivision / Short Subdivision / UPD Building Services: M/F / Commercial / SFR Clearing and Grading Right-of-Way Other: DFW HPA Shoreline Mngmt COE 404 Structural DOE Dam Safety Rockery/Vault FEMA Floodplain ESA Section 7 COE Wetlands Other: Part 5 PLAN AND REPORT INFORMATION Technical Information Report Type of Drainage Review (circle): Date (include revision dates): July 2, 2018 Date of Final: Site Improvement Plan (Engr. Plans) Type (circle one): Full / Modified / : Small Site Date (include revision dates): Date of Final: Part 6 SWDM ADJUSTMENT APPROVALS Type (circle one): Standard / Blanket Description: (include conditions in TIR Section 2) _____________________________________________________________________________________ _____________________________________________________________________________________ ____________________________________________________________________________________ Date of Approval: ☒ Full ☐ Targeted ☐ Simplified ☐ Large Project ☐ Directed 2018 D. R. STRONG Consulting Engineers Inc. Page 7 Cedars at the Highlands Level One Downstream Analysis Renton, Washington Part 7 MONITORING REQUIREMENTS Monitoring Required: Yes / No Start Date: TBD Completion Date Describe: Monitor discharge location during construction. Re: SWDM Adjustment No. _____________ Part 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan: Renton Comprehensive Plan Special District Overlays: N/A Drainage Basin: Lower Cedar River Drainage Basin Stormwater Requirements: Flow Control Duration Standard – Matching Forested and Basic WQ treatment Part 9 ONSITE AND ADJACENT SENSITIVE AREAS River/ Stream: Type Ns Stream Lake Wetlands Category III Closed Depression Floodplain Other Steep Slope Erosion Hazard Landslide Hazard Coal Mine Hazard Seismic Hazard Habitat Protection Part 10 SOILS Soil Type AgC Slopes 8-15% Erosion Potential Moderate to Severe High Groundwater Table Sole Source Aquifer other Seeps/Springs Additional Sheets Attached 2018 D. R. STRONG Consulting Engineers Inc. Page 8 Cedars at the Highlands Level One Downstream Analysis Renton, Washington Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE Core Requirement #2 – Offsite Analysis SEPA Sensitive/Critical Areas _______ LID Infeasibility Additional Sheet Attached LIMITATION / SITE CONSTRAINT Part 12 TIR SUMMARY SHEET Threshold Discharge Area: Site comprised of one TDA (name or description) Core Requirements (all 8 apply) Discharge of Natural Location Yes Number of Natural Discharge Locations: 2 Offsite Analysis Level: 1 / 2 / 3 dated: 01/25/2017 Flow Control Standard: Matching Forested (incl. facility summary sheet) or Exemption Number: __________________ On-site BMPS: Reduced Impervious Surface Credit and Basic Dispersion Conveyance System Spill containment located at: TBD Erosion and Sediment Control / CSWPP/CESCL/ESC Site Supervisor: TBD Construction Stormwater Pollution Contact Phone: TBD Prevention After Hours Phone: TBD Maintenance and Operation Responsibility: Private / Public If Private, Maintenance Log Required: Yes / No Financial Guarantees and Provided: Yes / No Liability Water Quality Type: Basic / Sens Lake / Enhanced Basic / Bog (include facility summary sheet) or exemption No. Landscape Management Plan: Yes / No Special Requirements (as applicable) Area Specific Drainage Type: CDA / SDO / MDP / BP / LMP / Shared / None Requirements Name: Floodplain/Floodway Delineation Type: Major / Minor / Exemption / None 100-year Base Flood Elevation (or range): Datum: Flood Protection Facilities Describe: N/A Source Control Describe Landuse: (comm. / industrial landuse) Describe any structural controls: Oil Control High-use Site: Yes / No 2018 D. R. STRONG Consulting Engineers Inc. Page 9 Cedars at the Highlands Level One Downstream Analysis Renton, Washington Treatment BMP: Maintenance Agreement: Yes / No with whom? Other Drainage Structures Describe: Runoff will be collected and conveyed to the detention vault located in Tract A. The proposed vault will be immediately followed by a Stormfilter to achieve water quality standards. Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION Clearing Limits Cover Measures Perimeter Protection Traffic Area Stabilization Sediment Retention Surface Water Collection Dewatering Control Dust control Flow Control Control Pollutants Protect Existing and Proposed BMPs/Facilities Maintain Protective BMPs / Manage Project MINIMUM ESC REQUIREMENTS AFTER CONSTRUCTION Stabilize Exposed Surfaces Remove and Restore Temporary ESC Facilities Clean and Remove All Silt and Debris, Ensure Operations of Permanent BMPs/Facilities, restore operation of BMPs/Facilities as necessary Flag Limits of sensitive areas and open space Preservation areas Other 2018 D. R. STRONG Consulting Engineers Inc. Page 10 Cedars at the Highlands Level One Downstream Analysis Renton, Washington Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch Flow Control Type/Description Water Quality Type/Description Detention Infiltration Regional Facility Shared Facility On-site BMPs Other Detention Vault Reduced Impervious Surface Credit and Basic Dispersion __________________ Vegetated Flowpath Wetpool Filtration Oil Control Spill Control On-site BMPs Other _________________ Contech StormFilter See flow control Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS Drainage Easement Covenant Native Growth Protection Covenant Tract Other: Sanitary Sewer Easement Cast in Place Vault Retaining Wall Rockery > 4’ High Structural on Steep Slope Other: Part 17 SIGNATURE OF PROFESSIONAL ENGINEER I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attached Technical Information Report. To the best of my knowledge the information provided here is accurate. Signed/Date 2018 D. R. STRONG Consulting Engineers Inc. Page 11 Cedars at the Highlands Level One Downstream Analysis Renton, Washington FIGURE 2 SITE LOCATION Site 2018 D. R. STRONG Consulting Engineers Inc. Page 12 Cedars at the Highlands Level One Downstream Analysis Renton, Washington FIGURE 3 DRAINAGE BASINS, SUBBASINS, AND SITE CHARACTERISTICS 0 GRAPHIC SCALE 906030 1 INCH = 60 FT. 2018 D. R. STRONG Consulting Engineers Inc. Page 13 Cedars at the Highlands Level One Downstream Analysis Renton, Washington FIGURE 4 SOILS 2018 D. R. STRONG Consulting Engineers Inc. Page 14 Cedars at the Highlands Level One Downstream Analysis Renton, Washington King County Area, Washington AgC—Alderwood gravelly sandy loam, 8 to 15 percent slopes a) Map Unit Setting  National map unit symbol: 2t626  Elevation: 50 to 800 feet  Mean annual precipitation: 20 to 60 inches  Mean annual air temperature: 46 to 52 degrees F  Frost-free period: 160 to 240 days  Farmland classification: Prime farmland if irrigated b) Map Unit Composition  Alderwood and similar soils: 85 percent  Minor components: 15 percent  Estimates are based on observations, descriptions, and transects of the mapunit. c) Description of Alderwood (1) Setting  Landform: Ridges, hills  Landform position (two-dimensional): Shoulder  Landform position (three-dimensional): Nose slope, talf  Down-slope shape: Linear, convex  Across-slope shape: Convex  Parent material: Glacial drift and/or glacial outwash over dense glaciomarine deposits (2) Typical profile  A - 0 to 7 inches: gravelly sandy loam  Bw1 - 7 to 21 inches: very gravelly sandy loam  Bw2 - 21 to 30 inches: very gravelly sandy loam  Bg - 30 to 35 inches: very gravelly sandy loam  2Cd1 - 35 to 43 inches: very gravelly sandy loam  2Cd2 - 43 to 59 inches: very gravelly sandy loam (3) Properties and qualities  Slope: 8 to 15 percent  Depth to restrictive feature: 20 to 39 inches to densic material  Natural drainage class: Moderately well drained  Capacity of the most limiting layer to transmit water (Ksat): Very low to moderately low (0.00 to 0.06 in/hr)  Depth to water table: About 18 to 37 inches  Frequency of flooding: None  Frequency of ponding: None  Available water storage in profile: Very low (about 2.7 inches) (4) Interpretive groups  Land capability classification (irrigated): None specified  Land capability classification (nonirrigated): 4s  Hydrologic Soil Group: B  Other vegetative classification: Limited Depth Soils (G002XN302WA), Limited Depth Soils (G002XS301WA), Limited Depth Soils (G002XF303WA)  Hydric soil rating: No 2018 D. R. STRONG Consulting Engineers Inc. Page 15 Cedars at the Highlands Level One Downstream Analysis Renton, Washington d) Minor Components (1) Everett  Percent of map unit: 5 percent  Landform: Eskers, kames, moraines  Landform position (two-dimensional): Shoulder, footslope  Landform position (three-dimensional): Crest, base slope  Down-slope shape: Convex  Across-slope shape: Convex  Hydric soil rating: No (2) Indianola  Percent of map unit: 5 percent  Landform: Eskers, kames, terraces  Landform position (three-dimensional): Tread  Down-slope shape: Linear  Across-slope shape: Linear  Hydric soil rating: No (3) Shalcar  Percent of map unit: 3 percent  Landform: Depressions  Landform position (three-dimensional): Dip  Down-slope shape: Concave  Across-slope shape: Concave  Hydric soil rating: Yes (4) Norma  Percent of map unit: 2 percent  Landform: Depressions, drainageways  Landform position (three-dimensional): Dip  Down-slope shape: Concave, linear  Across-slope shape: Concave  Hydric soil rating: Yes 2018 D. R. STRONG Consulting Engineers Inc. Page 16 Cedars at the Highlands Level One Downstream Analysis Renton, Washington SECTION II CONDITIONS AND REQUIREMENTS SUMMARY The Project must comply with the following Core and Special Requirements:  C.R. #1 – Discharge at the Natural Location: Existing drainage patterns discharge from the Site at two locations. The two downstream paths converge within ¼ mile, maintaining one TDA. Natural discharge point 1 is an unnamed Type Ns Stream and category III wetland located in the northeast section of the Site. This stream and wetland will be enclosed in a Sensitive Area Tract. Natural discharge point 2 is along the southern property line, where stormwater is collected by a swale and conveyed to the south and east . Discharge from the detention facility will be directed to the existing swale located to the south and east of the Site , thus maintaining discharge at the natural locations.  C.R. #2 – Offsite Analysis: Analysis is included in Section III. The Analysis describes the Site’s runoff patterns in detail.  C.R. #3 – Flow Control: The Project is required to adhere to Flow Control Duration Standard – Matching Forested site conditions. However, the project will meet the City’s Flood Problem Flow Control Standard due to the existing downstream flooding problem within the drainage basin tributary to the SE 144th Street storm system. One detention vault will provide flow control as required for the new and replaced impervious and pervious surfaces. The Site is required to “match the flow duration of pre-developed rates for forested (historic) site conditions over the range of flows extending from 50% of 2 -year up to the full 50-year flow and match peaks for the 2-, 10-, and 100-year returm periods,” (2017 CORSWDM, Sec. 1.2.3.1). A detention vault will accommodate this requirement.  C.R. #4 – Conveyance System: New pipe systems are required to be designed with sufficient capacity to convey and contain (with minimum 6-inches of freeboard) the 25-year peak flow, assuming developed conditions for onsite tributary areas and existing conditions for any offsite tributary areas. Pipe system structures may overtop for runoff events that exceed the 25 -year design capacity, provided the overflow from a 100-year runoff event does not create or aggravate a “severe flooding problem” or “severe erosion problem” as defined in C.R. #2. Any overflow occurring onsite for runoff events up to and including the 100 -year event must discharge at the natural location for the project site. In residential subdivisions, such overflow must be contained within an onsite drainage easement, tract, covenant or public right-of-way. The proposed conveyance system will be analyzed using the KCBW program to determine if the proposed conveyance system is capable of conveying the 100-year peak storm storm without overtopping any structures or channels. This analysis will be done at the time of engineering submittal.  C.R. #5 – Erosion and Sediment Control: The Project will provide the seven minimum ESC measures. A temporary erosion and sedimentation control plan will be presented as part of the engineering construction plan set. 2018 D. R. STRONG Consulting Engineers Inc. Page 17 Cedars at the Highlands Level One Downstream Analysis Renton, Washington  C.R. #6 – Maintenance and Operations: Maintenance of the proposed storm drainage facilities will be the responsibility of the City. An Operation and Maintenance Manual will be included in Section X at the time of construction plan preparation.  C.R. #7 – Financial Guarantees: Prior to commencing construction, the Applicant must post a drainage facilities restoration and site stabilization financial guarantee. For any constructed or modified drainage facilities to be maintained and operated by the City, the Applicant must: 1) Post a drainage defect and maintenance financial guarantee for a period of two years, and 2) Maintain the drainage facilities during the two-year period following posting of the drainage defect and maintenance financial guarantee.  C.R. #8 – Water Quality: The Project is required to provide basic water quality treatment. A Stormfilter immediately following the detention vault will accommodate this requirement.  C.R. #9 – On-Site BMPs: The Project is required to provide on-site BMPs to mitigate the impacts of storm and surface water runoff generated by new impervious surface, new pervious surface, existing impervious surfaces, and replaced impervious surface targeted for mitigation. It has been determined, using the order of preference outlined in Section 1.2.9.2.1 of the CORSWDM that basic dispersion and reduced impervious surfaces are the most feasible options to meet the on-site BMP requirements. Full dispersion is not feasible due to the amount of native growth that is being retained on the Site. Required native growth areas and flowpath lengths could not be met. Per the geotechnical infiltration evaluation letter dated July 13th, 2017, it has been recommended that due to the existing soil conditions, any level of stormwater infiltration feasibility is negligible. The requirements for full infiltration, limited infiltration, rain gardens, bioretention, and permeable pavement all necessitate the recommendation of infiltration from a geotechnical engineer.  S.R. #1 – Other Adopted Area-Specific Requirements: Not applicable for this Project.  S.R. #2 – Flood Hazard Area Delineation: There is no flood hazard areas on the Site, therefore S.R. #2 is not applicable for this project.  S.R. #3 – Flood Protection Facilities: Not applicable for this Project.  S.R. #4 – Source Control: Not applicable for this Project.  S.R. #5 – Oil Control: Not applicable for this Project.  S.R. #6 – Aquifer Protection Area: Site not located within zones 1 and 2, therefore not applicable for this Project. 2018 D. R. STRONG Consulting Engineers Inc. Page 18 Cedars at the Highlands Level One Downstream Analysis Renton, Washington CONDITIONS OF APPROVAL Cedars at the Highlands PRE16-000524 TBD 2018 D. R. STRONG Consulting Engineers Inc. Page 19 Cedars at the Highlands Level One Downstream Analysis Renton, Washington SECTION III OFF-SITE ANALYSIS LEVEL ONE DOWNSTREAM ANALYSIS TASK 1: DEFINE AND MAP STUDY AREA This Offsite Analysis was prepared in accordance with Core Requirement #2, Section 1.2.2 of the 2017 City of Renton Surface Water Design Manual (CORSWDM). The Site is located at 14120 160th Avenue SE, Renton, Washington. The Project is the subdivision of one parcel into thirteen single-family lots. See Figures 5 through 12 for maps of the study area. TASK 2: RESOURCE REVIEW  Adopted Basin Plans: King County Department of Permitting and Environmental Review (DPER) and Department of Natural Resources and Parks (DNRP) Lower Cedar River Basin Plan Summary  Finalized Drainage Studies: Alpine Nursery TIR.  Basin Reconnaissance Summary Reports: Cedar River Current and Future Conditions Report (April 1993).  Comprehensive Plans: Renton’s Comprehensive Plan, adopted on June 22, 2015, effective July 1, 2015.  Floodplain/Floodway (FEMA) Map: No floodplains exist on site, See Figure 11.  Other Offsite Analysis Reports: Mindy’s Place Critical Area Mitigation Plan  Sensitive Areas Map Folios, City of Renton GIS: See Figures 6-10. The City’s GIS system shows a wetland on Site. There is a category III wetland located in the northeast corner of the Site.  DNRP Drainage Complaints and Studies: Per King County Water and Land Resources Division, there are two complaints within the downstream paths, within approximately one mile from the Site within the last 10 years. See Figure 12.  USDA King County Soils Survey: See Figure 4  King County Wetlands Inventory: No wetlands were identified via King County Wetland Inventory. See Figure 8.  Migrating River Studies: None are applicable to this Site.  King County Designated Water Quality Problems: Per the Washington State Water Quality Assessment 303(d)/305(b) Integrated Report current as of 2012, there are no water quality problems within 1 mile downstream of the Site. 2018 D. R. STRONG Consulting Engineers Inc. Page 20 Cedars at the Highlands Level One Downstream Analysis Renton, Washington FIGURE 5 CITY OF RENTON TOPOGRAPHY MAP Site 2018 D. R. STRONG Consulting Engineers Inc. Page 21 Cedars at the Highlands Level One Downstream Analysis Renton, Washington FIGURE 6 CITY OF RENTON COAL MINE HAZARD AREAS MAP Site 2018 D. R. STRONG Consulting Engineers Inc. Page 22 Cedars at the Highlands Level One Downstream Analysis Renton, Washington FIGURE 7 CITY OF RENTON FLOOD HAZARDS MAP Site 2018 D. R. STRONG Consulting Engineers Inc. Page 23 Cedars at the Highlands Level One Downstream Analysis Renton, Washington FIGURE 8 CITY OF RENTON STREAMS AND WETLANDS MAP Site 2018 D. R. STRONG Consulting Engineers Inc. Page 24 Cedars at the Highlands Level One Downstream Analysis Renton, Washington FIGURE 9 CITY OF RENTON LANDSLIDE HAZARDS MAP Site 2018 D. R. STRONG Consulting Engineers Inc. Page 25 Cedars at the Highlands Level One Downstream Analysis Renton, Washington FIGURE 10 CITY OF RENTON SEISMIC HAZARD AREAS MAP Site 2018 D. R. STRONG Consulting Engineers Inc. Page 26 Cedars at the Highlands Level One Downstream Analysis Renton, Washington FIGURE 11 FEMA MAP Site (Approximate) 2018 D. R. STRONG Consulting Engineers Inc. Page 27 Cedars at the Highlands Level One Downstream Analysis Renton, Washington FIGURE 12 KING COUNTY IMAP DRAINAGE COMPLAINTS MAP Location Complaint Year Description A X 2007 Letter regarding private channel. A C 2008 Water flows even w/ no rain lately. Inv found contractor working in Evendell pond. Still under DDES. A FCR 2007 No site visit needed. Discussed concerns about existing & proposed storm systems. Site A A 2018 D. R. STRONG Consulting Engineers Inc. Page 28 Cedars at the Highlands Level One Downstream Analysis Renton, Washington TASK 3: FIELD INSPECTION UPSTREAM TRIBUTARY AREA Upon evaluation of the upstream area through examining COR topographic map (see Figure 5) and by conducting field reconnaissance on January 25th, 2017, there is a moderate upstream tributary area draining onto the Site in two locations. The first is the existing Type Ns stream flowing through the northeast area of the Site. This area is located in a critical areas tract to remain undisturbed and does not impact nor is it impacted by the developable area of the Project. The second upstream runoff location is the frontage swale on 160th Ave SE. This swale collects runoff from northern parcels and drains onto the Site. This stormwater sheet and channel flows through the Site and discharges near the southeast of the Site. The proposal includes a bypass line that will convey the stormwater draining onto the site from the frontage swale to its natural discharge point located in the southeast of the Site. The parcels to the south and east sheet flow to the south, away from the Site. GENERAL ONSITE AND OFFSITE DRAINAGE DESCRIPTIONS The Site is sloped to the east at slope s ranging from 0-20 percent. A ridge exists in the northeastern portion of the Site, resulting in two distinct Natural Drainage Area’s (NDA’s), which converge within ¼ mile. Therefore, the Site is encompassed within a single Threshold Discharge Area (TDA). NDA 1 is a tributary area to a Type Ns Stream and category III wetland which flows through the northeast corner of the Site. This unnamed stream flows through adjacent parcels to the east before discharging into a retention pond south of the Site where runoff converges with NDA 2. This stream and tributary area will remain undisturbed NDA 2 contains the majority of the Site’s stormwater runoff. The Site’s stormwater sheet flows in a southeasterly direction before being collected by a private stormwate r CPP that conveys runoff to a swale located off property at the southeast corner of the Site. This swale conveys runoff to a detention pond which discharges to the existing conveyance system located in SE 144th Street. Runoff continues west through the conveyance system in SE 144th Street and then crosses underneath 154th Place SE where it outlets to Stewart Creek, a Class 3 stream. Stewart Creek outlets to Cedar River approximately 6,000 feet from the Site. 2018 D. R. STRONG Consulting Engineers Inc. Page 29 Cedars at the Highlands Level One Downstream Analysis Renton, Washington TASK 4: DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS DRAINAGE SYSTEM DESCRIPTION The downstream analysis is further illustrated and detailed in the Dow nstream Map Figure 13 and Downstream Table Figure 14. The drainage area is located within the Lower Cedar River Drainage Basin. The drainage area was evaluated by reviewing available resources described in Task 2, and by conducting a field reconnaissance on January 25th, 2017 under overcast conditions. DOWNSTREAM PATH NDA 1 “A1” is a Natural Discharge Area (NDA) for the Site. It is located along the eastern property line (±0). From Point “A1” to Point “B1”, runoff continues to flow east as channel flow via an unnamed Type Ns Stream. Moderate flow was observed (±0’-927’). Point “B1” is the inlet of an 18” diameter CMP culvert. (±927’). From Point “B1” to Point “C1”, runoff is conveyed in a southwesterly direction as pipe flow via an 18” CMP culvert. Moderate flow was observed (±927’-960’). Point “C1” is the outlet of a 18” CMP culvert. Moderate flow was observed (±960’). Point “C1” is the convergence point of NDA 1 and NDA 2. DOWNSTREAM PATH NDA 2 Point “A2” is a NDA for the Site. It is channel flow located on the southern property line. (±0). From Point “A2” to Point “B2”, runoff is conveyed easterly as channel flow via a 3’ tall and 2’ wide swale. Moderate flow observed (±0’-60’). Point “B2” is the inlet of a 24” diameter CPP. Moderate flow observed. (±60’). From Point “B2” to Point “C2”, runoff is conveyed in an easterly direction as pipe flow via 24” CPP. Moderate flow was observed (±60’-142’). Point “C2” is the outlet of a 24” diameter CPP. Moderate flow observed. (±142’). From Point “C2” to Point “D2”, runoff is conveyed in a southerly direction as channel flow via a 6’ tall and 4’ wide swale. Moderate flow was observed. (±142’-269’). Point “D2” is the inlet of a 48” diameter CMP. Moderate flow observed. (±269’). From Point “D2” to Point “E2”, runoff is conveyed in a southerly direction as pipe flow via a 48” diameter CMP. Moderate flow was observed (±269’-277’). Point “E2” is the outlet of a 48” diameter CMP. Moderate flow observed. (±277’). From Point “E2” to Point “F2”, runoff is conveyed in a southerly direction as channel flow via a 9’ tall and 6’ wide swale. Moderate flow was observed (±277’-507’). Point “F2” is the inlet of a 18” diameter CPP. Moderate flow was observed. (±507’). 2018 D. R. STRONG Consulting Engineers Inc. Page 30 Cedars at the Highlands Level One Downstream Analysis Renton, Washington From Point “F2” to Point “G2”, runoff is conveyed in a southerly direction as pipe flow via a 18” diameter CPP culvert. Moderate flow was observed (±507’-515’). Point “G2” is the outlet of a 18” CPP. Moderate flow was observed. (±515’). From Point “G2” to Point “H2”, runoff is conveyed in a southerly direction as channel flow via a 1’ tall and 2’ wide channel. Moderate flow was observed (±515’-663’). Point “H2” is an existing detention pond. (±663’). From Point “H2” to Point “I2”, runoff is conveyed in a southerly direction as surface flow via an existing detention pond. Standing water was observed (±663’-779’). Point “I2”, is the inlet of a 18” CMP. Moderate flow was observed. (±779’). From Point “I2” to Point “J2”, runoff is conveyed in a southerly direction as pipe flow via a 18” diameter CMP. Moderate flow was observed. (±779’-839’). Point “J2” is a Type 1 catch basin. COR Facility ID No. 144177. (±839’). From Point “J2” to Point “K2”, runoff is conveyed in a westerly direction as pipe flow via an 18” CMP. Moderate flow was observed. (±839’-949’). Point “K2” is a Type 1 catch basin. COR Facility ID No. 501597. CB contained inlet protection from neighboring construction activities. Flow direction was confirmed via construction projects TIR and COR Maps. (±949’). From Point “K2” to Point “L2”, runoff is conveyed in a westerly direction via an 18” CMP. (±949’-1,232’). Point “L2” is a Type 1 catch basin. COR Facility ID No. 501598. CB contained inlet protection from neighboring construction activities. Flow direction was confirmed via construction projects TIR and COR Maps. (±1,232’). From Point “L2” to “M2”, runoff is conveyed in a westerly direction via an 18” CMP. (±1,232’-1,486’) Point “M2” is a Type 1 catch basin. COR Facility ID No. 501599. CB contained inlet protection from neighboring construction activities. Flow direction was confirmed via construction projects TIR and COR Maps. (±1,486’). This is the end of field investigation. TASK 5: MITIGATION OF EXISTING OR POTENTIAL PROBLEMS A review of the King County Water and Land Resources Division – Drainage Services Section Documented Drainage Complaints within one mile of the downstream flow paths revealed three complaints within the last ten years that have since been closed. These complaints can be seen in Figure 12. Several drainage complaints exist within the downstream path but are not within the last ten years and are no t applicable for Level One Downstream Analysis. 2018 D. R. STRONG Consulting Engineers Inc. Page 31 Cedars at the Highlands Level One Downstream Analysis Renton, Washington Complaint Parcel Number Summary Recurring Type Required Mitigation 2007-0244 7253700130 Letter regarding a private channel. Yes 1 None 2008-0339 7253700130 Water flows even w/ no rain lately. Inv found contractor working in Evendell pond. Still under DDES. No 1 Complaint has been closed. None 2007-0726 7253700130 No site visit needed. Discussed concerns about existing & proposed storm systems. Yes Related to complaint 2007- 0244 1 None Evaluation of these complaints concludes that all drainage complaints from this parcel are regarding the privately maintained channel that is the NDL of the proposed Site. Per Table 1.2.3.A, Summary of Flow Control Performance Criteria Acceptable for Impact Mitigation, the project will meet the City’s Flood Problem Flow Control Standard due to the existing downstream flooding problem within the drainage basin tributary to the SE 144th Street storm system. In addition to the increase flow control, the improvements proposed by the Project will mitigate the conveyance system nuisance problem by replacing all existing conveyance systems with a system of catch basins and pipes conforming to Core Requirement 4, Conveyance Analysis. The project should not create any problems as specified in Section 1.2.2.1 of the Manual and therefore is not required to provide Drainage Problem Impact Mitigation subject to the requirements of Section 1.2.2.2. A detention vault will provide flow control and basic water quality requirements will be met through the use of a Contech Stormfilter. During construction, standard sediment and erosion control methods will be utilized. This will include the use of a stabilized construction entrance, perimeter silt fencing, and other necessary measures to minimize soil erosion during construction. 2018 D. R. STRONG Consulting Engineers Inc. Page 32 Cedars at the Highlands Level One Downstream Analysis Renton, Washington FIGURE 13 OFFSITE ANALYSIS DOWNSTREAM MAP GRAPHIC SCALE 0 100 200 400 1 INCH = 200 FT. 2018 D. R. STRONG Consulting Engineers Inc. Page 33 Cedars at the Highlands Level One Downstream Analysis Renton, Washington FIGURE 14 OFFSITE ANALYSIS DOWNSTREAM TABLE DOWNSTREAM PATH NDA 1 Symbol Drainage Component Type, Name, and Size Drainage Component Description Slope Distance From site Discharge Existing Problems Potential Problems Observations of field inspector resource reviewer, or resident See map Type: sheet flow, swale, Stream, channel, pipe, Pond; Size: diameter Surface area drainage basin, vegetation, cover, depth, type of sensitive area, volume % 1/4 mile = 1,320 feet Constrictions, under capacity, ponding, overtopping, flooding, habitat or organism destruction, scouring, bank sloughing, sedimentation, incision, other erosion Tributary area, likelihood of problem, overflow pathways, potential impacts. A1 Natural discharge area Runoff exits at the NDA along the eastern property line of the Site. 0’ None Observed None Anticipated Moderate flow observed A1-B1 East and south Stream Unnamed Type Ns Stream None Observed None Anticipated Moderate flow observed. Majority of stream not investigated due to being located on private property B1 Pipe inlet 18” CMP Culvert 927’ None Observed None Anticipated Moderate flow observed B1-C1 Westerly pipe flow 18” CMP Culvert None Observed None Anticipated Moderate flow observed C1 Pipe outlet 18” CMP Culvert ±960’ None Observed None Anticipated Moderate flow observed. This is the convergence point of NDA 1 and NDA 2. 2018 D. R. STRONG Consulting Engineers Inc. Page 34 Cedars at the Highlands Level One Downstream Analysis Renton, Washington DOWNSTREAM PATH NDA 2 Symbol Drainage Component Type, Name, and Size Drainage Component Description Slope Distance From site Discharge Existing Problems Potential Problems Observations of field inspector resource reviewer, or resident See map Type: sheet flow, swale, Stream, channel, pipe, Pond; Size: diameter Surface area drainage basin, vegetation, cover, depth, type of sensitive area, volume % 1/4 mile = 1,320 feet Constrictions, under capacity, ponding, overtopping, flooding, habitat or organism destruction, scouring, bank sloughing, sedimentation, incision, other erosion Tributary area, likelihood of problem, overflow pathways, potential impacts. A2 Natural discharge area – Channel Runoff exits Site across the southern property line as easterly channel flow 0’ None Observed None Anticipated Moderate flow observed A2-B2 Easterly channel flow 3’ tall 2’ wide channel. None Observed None Anticipated Moderate flow observed B2 Pipe inlet 24” diameter CPP 60’ None Observed None Anticipated Moderate flow observed B2-C2 Easterly pipe flow 24” diameter CPP None Observed None Anticipated Moderate flow observed C2 Pipe outlet 24” diameter CPP ±142’ None Observed None Anticipated Moderate flow observed C2-D2 Southerly channel flow 6’ tall, 4’ wide swale None Observed None Anticipated Moderate flow observed D2 Pipe inlet 48” diameter CMP ±269’ None Observed None Anticipated Moderate flow observed D2-E2 Southerly pipe flow 48” diameter CMP None Observed None Anticipated Moderate flow observed E2 Pipe outlet 48” diameter CMP ±277’ None Observed None Anticipated Moderate flow observed E2-F2 Southerly channel flow 9’ tall, 6’ wide swale None Observed None Anticipated Moderate flow observed F2 Pipe inlet 18” diameter CPP ±507’ None Observed None Anticipated Moderate flow observed F2-G2 Southerly pipe flow 18” diameter CPP None Observed None Anticipated Moderate flow observed G2 Pipe outlet 18” diameter CPP ±515’ None Observed None Anticipated Moderate flow observed G2-H2 Southerly channel flow 1’ tall, 2’ wide channel None Observed None Anticipated Moderate flow observed 2018 D. R. STRONG Consulting Engineers Inc. Page 35 Cedars at the Highlands Level One Downstream Analysis Renton, Washington H2 Detention pond Existing detention pond ±663’ None Observed None Anticipated Moderate flow observed H2-I2 Southerly surface flow Existing detention pond None Observed None Anticipated Standing Water I2 Pipe inlet 18” CMP ±779 None Observed None Anticipated Moderate flow observed I2-J2 Southerly pipe flow 18” CMP None Observed None Anticipated Moderate flow observed J2 Type 1 CB. COR Facility No. 144177 18” CMP inlet from North, 18” CMP Inlet from East, 18” CMP outlet to West. ±839’ None Observed None Anticipated Moderate flow observed J2-K2 Westerly pipe flow 18” CMP None Observed None Anticipated Moderate flow observed K2 Type 1 CB. COR Facility No. 501597 Not field observable. ±949’ None Observed None Anticipated CB contains inlet protection from nearby construction activity. Flow direction confirmed via construction project’s TIR and COR Maps. K2-L2 Westerly pipe flow None Observed None Anticipated Moderate flow observed L2 Type 1 CB. COR Facility No. 501598 Not field observable. ±1,232’ None Observed None Anticipated CB contains inlet protection from nearby construction activity. Flow direction confirmed via construction project’s TIR and COR Maps. L2-M2 Westerly pipe flow None Observed None Anticipated M2 Type 1 CB. COR Facility No. 501599 Not field observable. ±1,486’ None Observed None Anticipated CB contains inlet protection from nearby construction activity. Flow direction confirmed via construction project’s TIR and COR Maps. End of field investigation. 2018 D. R. STRONG Consulting Engineers Inc. Page 36 Cedars at the Highlands Technical Information Report Renton, Washington SECTION IV FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID) AND WATER QUALITY FACILITY ANALYSIS AND DESIGN EXISTING SITE HYDROLOGY Western Washington Hydrology Model (WWHM) 2012 was used to model runoff from the Site. The Site falls within the City’s Flow Control Duration Standard – Matching Forested area. However, the project will meet the City’s Flood Problem Flow Control Standard due to the existing downstream flooding problem within the drainage basin tributary to the SE 144th Street storm system. The Site was modeled as predeveloped forested condtions for target surfaces (see Figure 15). Per Table 3.2.2.A of the 2017 CORSWDM the Soil group for Alderwood is modeled as “Till.” The Project currently proposes to retain one existing structure on site under a 5-year temporary use permit. The temporary use permit is with the assumption that in 5 years, this structure will be removed and replaced with single family residences. Therefo re, the existing site hydrology will be modeled as “Till Forest” in order to account for the future removal of the existing structure. Results of the WWHM analysis are included in this section. Modeling Input for the Pre-developed Site PREDEVELOPED LAND USE Name : Basin 1 Bypass: No GroundWater: No Pervious Land Use acre C, Forest, Flat 4.109 Pervious Total 4.109 Impervious Land Use acre Impervious Total 0 Basin Total 4.109 Modeling Results Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.1605 5 year 0.2646 10 year 0.3437 25 year 0.4541 50 year 0.5437 100 year 0.6393 2018 D. R. STRONG Consulting Engineers Inc. Page 37 Cedars at the Highlands Technical Information Report Renton, Washington FIGURE 15 PREDEVELOPED AREA MAP GRAPHIC SCALE 0 30 60 120 1 INCH = 60 FT. 2018 D. R. STRONG Consulting Engineers Inc. Page 38 Cedars at the Highlands Technical Information Report Renton, Washington DEVELOPED SITE HYDROLOGY Soil Type The soil types are unchanged from predeveloped conditions. Land Cover WWHM was used to model the developed peak runoff from the Site. The portions of the Site within the developable area tributary to the proposed detention facility were modeled as “Till Grass”, and “Impervious” as appropriate. In order to accurately model the developed site hydrology, considerations were made for individual lots. Due to the existing structure occupying Lot 9, it has been modeled with the maximum impervious allowed per zoning code (R-4, 50%). All other lots have been modeled utilizing the proposed small lot BMP requirements; reduced impervious surface credit and basic dispersion. Lot impervious area restrictions vary from 400 to 700 square feet less than the minimum assumed impervious coverage of 4,000 square feet as defined in section 3.2.2.1 of the CORSWDM (Manual). Results of the WWHM analysis are included in this section. 2018 D. R. STRONG Consulting Engineers Inc. Page 39 Cedars at the Highlands Technical Information Report Renton, Washington Area Breakdown Lot Area Disturbed LOT Area Undist Imp by Zoning BMP Reqd Minimum 4,000 s.f. Imp Reduced Imp Basic Dispersion BMP Credit total impervious pervious impervious pervious 1 9,830 0 4,915 983 4,000 3,300 700 1,400 9,830 0 0 3,300 6,530 2 9,001 0 4,501 900 4,000 3,400 700 1,300 9,001 0 0 3,400 5,601 3 9,000 0 4,500 900 4,000 3,400 700 1,300 9,000 0 0 3,400 5,600 4 9,001 0 4,501 900 4,000 3,400 700 1,300 9,001 0 0 3,400 5,601 5 9,005 0 4,503 901 4,000 3,400 700 1,300 9,005 0 0 3,400 5,605 6 9,002 0 4,501 900 4,000 3,400 700 1,300 9,002 0 0 3,400 5,602 7 9,279 0 4,640 928 4,000 3,600 700 1,100 9,279 0 0 3,600 5,679 8 12,832 0 6,416 2,566 4,000 3,600 700 1,100 12,832 0 0 3,600 9,232 9 16,911 0 8,456 3,382 4,000 0 16,911 0 0 8,456 8,456 10 9,398 0 4,699 940 4,000 3,400 700 1,300 9,398 0 0 3,400 5,998 11 9,101 0 4,551 910 4,000 3,400 700 1,300 9,101 0 0 3,400 5,701 12 9,474 0 4,737 947 4,000 3,300 1,400 2,100 9,474 0 0 3,300 6,174 13 9,047 0 4,524 905 4,000 3,400 700 1,300 9,047 0 0 3,400 5,647 Total Lots 130,881 0 65,441 16,062 52,000 41,000 9,100 16,100 130,881 0 0 49,456 81,426 TRACT A 10,037 0 10,037 0 0 7,026 3,011 TRACT B 20,248 20,248 0 0 0 0 0 TRACT C 3,500 3500 0 0 0 0 0 Total Tracts 33,785 23,748 10,037 0 0 7,026 3,011 Total Lots & Tracts 164,666 140,918 0 0 56,481 84,437 ROW On Site ROW 30,866 0 30,866 0 0 25,000 5,866 Frontage ROW 5,253 0 5,253 0 0 4,202 1,051 Target Area - Bypass 1,957 0 1,957 0 0 1,957 0 Non-Target - Trade 1,957 0 1,957 0 0 1,957 0 Total ROW 38,076 38,076 0 0 31,159 6,917 BYPASS LOT TO DETENTIONBMP 2018 D. R. STRONG Consulting Engineers Inc. Page 40 Cedars at the Highlands Technical Information Report Renton, Washington Modeling Input MITIGATED LAND USE Name : RDIN Bypass: No GroundWater: No Pervious Land Use acre C, Lawn, Flat 2.097 Pervious Total 2.097 Impervious Land Use acre ROADS FLAT 0.715 ROOF TOPS FLAT 1.09 DRIVEWAYS FLAT 0.207 Impervious Total 2.012 Basin Total 4.109 Modeling Results Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 1.1574 5 year 1.5532 10 year 1.8349 25 year 2.2140 50 year 2.5135 100 year 2.8282 ___________________________________________________________________ 2018 D. R. STRONG Consulting Engineers Inc. Page 41 Cedars at the Highlands Technical Information Report Renton, Washington FIGURE 16 DEVELOPED AREA MAP GRAPHIC SCALE 0 30 60 120 1 INCH = 60 FT. 2018 D. R. STRONG Consulting Engineers Inc. Page 42 Cedars at the Highlands Technical Information Report Renton, Washington PERFORMANCE STANDARDS The Site is required to adhere to Flow Control Duration Standard – Matching Forested site conditions of the existing site. However, the project will meet the City’s Flood Problem Flow Control Standard due to the existing downstream flooding problem within the drainage basin tributary to the SE 144th Street storm system. A detention vault preceding a Stormfilter will provide flow control and basic water quality treatment. The Project is required to “match the flow duration of pre-developed rates for forested (historic) site conditions over the range of flows extending from 50% of 2-year up to the full 50-year flow and matches peaks for the 2 -, 10-, and 100-year return periods.” (CORSWDM, Sec. 1.2.3.1). Detention vault and Stormfilter details will be provided at the time of final engineering. Per Section 1.2.9.1 of the CORSWDM, the project is required to supplement the flow mitigation provided by required flow control facilities by use of Best Management Practices (BMPs). Section 1.2.9.2 outlines individual lot BMP requirements and the preferred BMPs to be utilized to achieve flow mitigation. Lots that are 11,000 s.f. or less are required to mitigate 10% of the total lot size of impervious area, and lots that are greater than 11,000 s.f. are required to mitigate impervious area equal to 20% of the total lot size. Small lot BMPs were determined by the BMP requirements outlin ed in Section 1.2.9.2.1 of the CORSWDM. As required by the CORSWDM, small lot BMP requirements were analyzed in the order of preference listed in section 1.2.9.2.1. 1. Full Dispersion: There is an insufficient amount of native growth in order to utilize full dispersion. The required undisturbed area and flowpath lengths result in full dispersion for any of the lots to be infeasible. 2. Full Infiltration: Per geotechnical infiltration evaluation, the existing soil on the Site makes full infiltration infeasible. The full geotechnical report has been submitted in conjunction with the preliminary application. 3. Limited Infiltration: Per geotechnical infiltration evaluation, the existing soil on the Site makes any form of infiltration infeasible. The full geotechnical report has been submitted in conjunction with the preliminary application. 4. Rain Gardens: Per geotechnical evaluation, the existing soil on the Site makes any form of infiltration infeasible. The full geotechnical report has been submitted in conjunction with the preliminary application. 5. Bioretention: Per geotechnical evaluation, the existing soil on the Site makes any form of infiltration infeasible. 6. Permeable Pavement: Per geotechnical evaluation, the existing soil on the Site makes any form of infiltration infeasible. 7. Basic Dispersion: A combination of restricted impervious area and basic dispersion via splash blocks is being proposed in order to meet the BMP requirements of small lots. Per the CORSWDM, any lots utilizing Basic Dispersion require a supplemental BMP to be implemented to achieve compliance. In addition to splash blocks, the Project is proposing to implement Reduced Impervious Surface Credits to meet flow control BMP requirements. The amount of reduced impervious surface per lot varies; the Area Breakdown table included in this section shows individual requirements for each lot. 2018 D. R. STRONG Consulting Engineers Inc. Page 43 Cedars at the Highlands Technical Information Report Renton, Washington FLOW CONTROL SYSTEM The Project will utilize an detention facility designed to control site runoff. The Western Washington Hydrology Modeling (WWHM) software was used to size the facility. The detention vault design information is shown here. WWHM2012 PROJECT REPORT ___________________________________________________________________ Project Name: Preliminary Vault Site Name: Cedars Site Address: 14120 160th Ave SE City : Renton Report Date: 7/2/2018 Gage : Seatac Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 1.17 Version Date: 2016/11/18 Version : 4.2.13 ___________________________________________________________________ Low Flow Threshold for POC 1 : 50 Percent of the 2 Year ___________________________________________________________________ High Flow Threshold for POC 1: 50 year ___________________________________________________________________ PREDEVELOPED LAND USE Name : PREDEV Bypass: No GroundWater: No Pervious Land Use acre C, Forest, Flat 4.109 Pervious Total 4.109 Impervious Land Use acre Impervious Total 0 Basin Total 4.109 __________________________________________________________________ Element Flows To: Surface Interflow Groundwater ___________________________________________________________________ MITIGATED LAND USE Name : RDIN Bypass: No 2018 D. R. STRONG Consulting Engineers Inc. Page 44 Cedars at the Highlands Technical Information Report Renton, Washington GroundWater: No Pervious Land Use acre C, Lawn, Flat 2.097 Pervious Total 2.097 Impervious Land Use acre ROADS FLAT 0.715 ROOF TOPS FLAT 1.09 DRIVEWAYS FLAT 0.207 Impervious Total 2.012 Basin Total 4.109 ___________________________________________________________________ Element Flows To: Surface Interflow Groundwater Vault 1 Vault 1 ___________________________________________________________________ Name : Vault 1 Width : 71.2373251505034 ft. Length : 71.2373251505034 ft. Depth: 12 ft. Discharge Structure Riser Height: 11 ft. Riser Diameter: 18 in. Orifice 1 Diameter: 1.11 in. Elevation: 0 ft. Orifice 2 Diameter: 1.96 in. Elevation: 7.787 ft. Orifice 3 Diameter: 1.19 in. Elevation: 8.7 ft. Element Flows To: Outlet 1 Outlet 2 ___________________________________________________________________ Vault Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs) 0.0000 0.116 0.000 0.000 0.000 0.1333 0.116 0.015 0.012 0.000 0.2667 0.116 0.031 0.017 0.000 0.4000 0.116 0.046 0.021 0.000 0.5333 0.116 0.062 0.024 0.000 0.6667 0.116 0.077 0.027 0.000 0.8000 0.116 0.093 0.029 0.000 0.9333 0.116 0.108 0.032 0.000 1.0667 0.116 0.124 0.034 0.000 1.2000 0.116 0.139 0.036 0.000 1.3333 0.116 0.155 0.038 0.000 1.4667 0.116 0.170 0.040 0.000 1.6000 0.116 0.186 0.042 0.000 1.7333 0.116 0.201 0.044 0.000 1.8667 0.116 0.217 0.045 0.000 2.0000 0.116 0.233 0.047 0.000 2.1333 0.116 0.248 0.048 0.000 2.2667 0.116 0.264 0.050 0.000 2.4000 0.116 0.279 0.051 0.000 2018 D. R. STRONG Consulting Engineers Inc. Page 45 Cedars at the Highlands Technical Information Report Renton, Washington 2.5333 0.116 0.295 0.053 0.000 2.6667 0.116 0.310 0.054 0.000 2.8000 0.116 0.326 0.055 0.000 2.9333 0.116 0.341 0.057 0.000 3.0667 0.116 0.357 0.058 0.000 3.2000 0.116 0.372 0.059 0.000 3.3333 0.116 0.388 0.061 0.000 3.4667 0.116 0.403 0.062 0.000 3.6000 0.116 0.419 0.063 0.000 3.7333 0.116 0.434 0.064 0.000 3.8667 0.116 0.450 0.065 0.000 4.0000 0.116 0.466 0.066 0.000 4.1333 0.116 0.481 0.068 0.000 4.2667 0.116 0.497 0.069 0.000 4.4000 0.116 0.512 0.070 0.000 4.5333 0.116 0.528 0.071 0.000 4.6667 0.116 0.543 0.072 0.000 4.8000 0.116 0.559 0.073 0.000 4.9333 0.116 0.574 0.074 0.000 5.0667 0.116 0.590 0.075 0.000 5.2000 0.116 0.605 0.076 0.000 5.3333 0.116 0.621 0.077 0.000 5.4667 0.116 0.636 0.078 0.000 5.6000 0.116 0.652 0.079 0.000 5.7333 0.116 0.667 0.080 0.000 5.8667 0.116 0.683 0.081 0.000 6.0000 0.116 0.699 0.081 0.000 6.1333 0.116 0.714 0.082 0.000 6.2667 0.116 0.730 0.083 0.000 6.4000 0.116 0.745 0.084 0.000 6.5333 0.116 0.761 0.085 0.000 6.6667 0.116 0.776 0.086 0.000 6.8000 0.116 0.792 0.087 0.000 6.9333 0.116 0.807 0.088 0.000 7.0667 0.116 0.823 0.088 0.000 7.2000 0.116 0.838 0.089 0.000 7.3333 0.116 0.854 0.090 0.000 7.4667 0.116 0.869 0.091 0.000 7.6000 0.116 0.885 0.092 0.000 7.7333 0.116 0.900 0.093 0.000 7.8667 0.116 0.916 0.123 0.000 8.0000 0.116 0.932 0.142 0.000 8.1333 0.116 0.947 0.156 0.000 8.2667 0.116 0.963 0.168 0.000 8.4000 0.116 0.978 0.178 0.000 8.5333 0.116 0.994 0.187 0.000 8.6667 0.116 1.009 0.196 0.000 8.8000 0.116 1.025 0.216 0.000 8.9333 0.116 1.040 0.230 0.000 9.0667 0.116 1.056 0.241 0.000 9.2000 0.116 1.071 0.252 0.000 9.3333 0.116 1.087 0.262 0.000 9.4667 0.116 1.102 0.271 0.000 9.6000 0.116 1.118 0.280 0.000 9.7333 0.116 1.133 0.288 0.000 9.8667 0.116 1.149 0.296 0.000 10.000 0.116 1.165 0.304 0.000 10.133 0.116 1.180 0.312 0.000 2018 D. R. STRONG Consulting Engineers Inc. Page 46 Cedars at the Highlands Technical Information Report Renton, Washington 10.267 0.116 1.196 0.319 0.000 10.400 0.116 1.211 0.326 0.000 10.533 0.116 1.227 0.333 0.000 10.667 0.116 1.242 0.340 0.000 10.800 0.116 1.258 0.346 0.000 10.933 0.116 1.273 0.352 0.000 11.067 0.116 1.289 0.632 0.000 11.200 0.116 1.304 1.769 0.000 11.333 0.116 1.320 3.253 0.000 11.467 0.116 1.335 4.703 0.000 11.600 0.116 1.351 5.784 0.000 11.733 0.116 1.366 6.402 0.000 11.867 0.116 1.382 6.991 0.000 12.000 0.116 1.398 7.486 0.000 12.133 0.116 1.413 7.949 0.000 12.267 0.000 0.000 8.386 0.000 ___________________________________________________________________ ___________________________________________________________________ ANALYSIS RESULTS Stream Protection Duration ___________________________________________________________________ Predeveloped Landuse Totals for POC #1 Total Pervious Area:4.109 Total Impervious Area:0 ___________________________________________________________________ Mitigated Landuse Totals for POC #1 Total Pervious Area:2.097 Total Impervious Area:2.012 ___________________________________________________________________ Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.16052 5 year 0.264644 10 year 0.343685 25 year 0.454147 50 year 0.543731 100 year 0.639312 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.093008 5 year 0.150518 10 year 0.200863 25 year 0.28129 50 year 0.355414 100 year 0.443565 ___________________________________________________________________ Stream Protection Duration Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.196 0.067 2018 D. R. STRONG Consulting Engineers Inc. Page 47 Cedars at the Highlands Technical Information Report Renton, Washington 1950 0.229 0.086 1951 0.330 0.286 1952 0.111 0.060 1953 0.093 0.075 1954 0.135 0.078 1955 0.208 0.077 1956 0.170 0.090 1957 0.153 0.078 1958 0.156 0.082 1959 0.132 0.069 1960 0.256 0.233 1961 0.128 0.086 1962 0.087 0.059 1963 0.125 0.079 1964 0.157 0.080 1965 0.117 0.091 1966 0.104 0.074 1967 0.244 0.082 1968 0.143 0.075 1969 0.138 0.071 1970 0.116 0.075 1971 0.146 0.082 1972 0.252 0.209 1973 0.119 0.090 1974 0.134 0.082 1975 0.191 0.073 1976 0.136 0.079 1977 0.047 0.061 1978 0.114 0.084 1979 0.071 0.057 1980 0.359 0.252 1981 0.105 0.076 1982 0.249 0.145 1983 0.171 0.081 1984 0.108 0.065 1985 0.063 0.068 1986 0.268 0.090 1987 0.247 0.173 1988 0.106 0.066 1989 0.066 0.066 1990 0.688 0.258 1991 0.310 0.206 1992 0.129 0.085 1993 0.125 0.064 1994 0.051 0.056 1995 0.167 0.085 1996 0.392 0.293 1997 0.310 0.274 1998 0.110 0.065 1999 0.428 0.190 2000 0.120 0.084 2001 0.031 0.051 2002 0.167 0.114 2003 0.229 0.074 2004 0.265 0.276 2005 0.174 0.080 2006 0.180 0.090 2007 0.508 0.457 2018 D. R. STRONG Consulting Engineers Inc. Page 48 Cedars at the Highlands Technical Information Report Renton, Washington 2008 0.540 0.295 2009 0.243 0.092 ___________________________________________________________________ Stream Protection Duration Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.6875 0.4568 2 0.5404 0.2948 3 0.5084 0.2925 4 0.4282 0.2861 5 0.3920 0.2764 6 0.3592 0.2743 7 0.3300 0.2575 8 0.3099 0.2515 9 0.3095 0.2330 10 0.2684 0.2092 11 0.2649 0.2061 12 0.2562 0.1898 13 0.2521 0.1726 14 0.2494 0.1450 15 0.2466 0.1144 16 0.2439 0.0915 17 0.2433 0.0906 18 0.2294 0.0904 19 0.2285 0.0904 20 0.2083 0.0902 21 0.1965 0.0900 22 0.1912 0.0857 23 0.1803 0.0857 24 0.1740 0.0854 25 0.1713 0.0846 26 0.1697 0.0841 27 0.1668 0.0836 28 0.1667 0.0821 29 0.1572 0.0819 30 0.1555 0.0818 31 0.1533 0.0816 32 0.1463 0.0813 33 0.1426 0.0799 34 0.1376 0.0796 35 0.1361 0.0791 36 0.1350 0.0790 37 0.1341 0.0781 38 0.1321 0.0780 39 0.1293 0.0771 40 0.1281 0.0760 41 0.1254 0.0754 42 0.1250 0.0752 43 0.1196 0.0746 44 0.1191 0.0736 45 0.1171 0.0736 46 0.1155 0.0735 47 0.1142 0.0711 48 0.1106 0.0685 49 0.1104 0.0684 50 0.1082 0.0672 51 0.1060 0.0663 2018 D. R. STRONG Consulting Engineers Inc. Page 49 Cedars at the Highlands Technical Information Report Renton, Washington 52 0.1047 0.0658 53 0.1040 0.0652 54 0.0932 0.0647 55 0.0869 0.0645 56 0.0711 0.0608 57 0.0663 0.0604 58 0.0634 0.0589 59 0.0510 0.0574 60 0.0469 0.0559 61 0.0311 0.0514 ___________________________________________________________________ Stream Protection Duration POC #1 The Facility PASSED The Facility PASSED. Flow(cfs) Predev Mit Percentage Pass/Fail 0.0803 18576 16074 86 Pass 0.0849 16523 11182 67 Pass 0.0896 14540 6564 45 Pass 0.0943 12776 3287 25 Pass 0.0990 11462 3161 27 Pass 0.1037 10059 3048 30 Pass 0.1083 8915 2941 32 Pass 0.1130 7843 2832 36 Pass 0.1177 7142 2742 38 Pass 0.1224 6340 2659 41 Pass 0.1271 5683 2541 44 Pass 0.1318 5251 2453 46 Pass 0.1364 4738 2355 49 Pass 0.1411 4291 2246 52 Pass 0.1458 3970 2117 53 Pass 0.1505 3559 1995 56 Pass 0.1552 3195 1889 59 Pass 0.1598 2920 1794 61 Pass 0.1645 2627 1699 64 Pass 0.1692 2363 1605 67 Pass 0.1739 2175 1512 69 Pass 0.1786 1975 1406 71 Pass 0.1833 1804 1270 70 Pass 0.1879 1694 1148 67 Pass 0.1926 1532 1052 68 Pass 0.1973 1352 950 70 Pass 0.2020 1245 906 72 Pass 0.2067 1141 845 74 Pass 0.2113 1047 795 75 Pass 0.2160 970 760 78 Pass 0.2207 916 728 79 Pass 0.2254 843 687 81 Pass 0.2301 766 644 84 Pass 0.2348 715 587 82 Pass 0.2394 639 543 84 Pass 0.2441 572 494 86 Pass 0.2488 496 456 91 Pass 0.2535 432 410 94 Pass 0.2582 378 355 93 Pass 2018 D. R. STRONG Consulting Engineers Inc. Page 50 Cedars at the Highlands Technical Information Report Renton, Washington 0.2628 344 327 95 Pass 0.2675 312 277 88 Pass 0.2722 271 226 83 Pass 0.2769 245 186 75 Pass 0.2816 202 164 81 Pass 0.2862 172 132 76 Pass 0.2909 151 116 76 Pass 0.2956 125 86 68 Pass 0.3003 110 79 71 Pass 0.3050 97 73 75 Pass 0.3097 85 67 78 Pass 0.3143 71 62 87 Pass 0.3190 61 56 91 Pass 0.3237 55 53 96 Pass 0.3284 45 47 104 Pass 0.3331 40 43 107 Pass 0.3377 37 39 105 Pass 0.3424 35 33 94 Pass 0.3471 29 21 72 Pass 0.3518 25 16 64 Pass 0.3565 22 12 54 Pass 0.3612 17 11 64 Pass 0.3658 15 11 73 Pass 0.3705 12 10 83 Pass 0.3752 9 9 100 Pass 0.3799 9 9 100 Pass 0.3846 8 7 87 Pass 0.3892 8 6 75 Pass 0.3939 7 6 85 Pass 0.3986 7 5 71 Pass 0.4033 7 5 71 Pass 0.4080 7 5 71 Pass 0.4126 7 4 57 Pass 0.4173 7 4 57 Pass 0.4220 7 4 57 Pass 0.4267 6 3 50 Pass 0.4314 5 3 60 Pass 0.4361 5 3 60 Pass 0.4407 5 3 60 Pass 0.4454 4 3 75 Pass 0.4501 4 1 25 Pass 0.4548 4 1 25 Pass 0.4595 4 0 0 Pass 0.4641 4 0 0 Pass 0.4688 4 0 0 Pass 0.4735 4 0 0 Pass 0.4782 4 0 0 Pass 0.4829 4 0 0 Pass 0.4876 4 0 0 Pass 0.4922 3 0 0 Pass 0.4969 3 0 0 Pass 0.5016 3 0 0 Pass 0.5063 3 0 0 Pass 0.5110 2 0 0 Pass 0.5156 2 0 0 Pass 0.5203 2 0 0 Pass 0.5250 2 0 0 Pass 0.5297 2 0 0 Pass 2018 D. R. STRONG Consulting Engineers Inc. Page 51 Cedars at the Highlands Technical Information Report Renton, Washington 0.5344 2 0 0 Pass 0.5390 2 0 0 Pass 0.5437 1 0 0 Pass _____________________________________________________ ___________________________________________________________________ Water Quality BMP Flow and Volume for POC #1 On-line facility volume: 0.3704 acre-feet On-line facility target flow: 0.384 cfs. Adjusted for 15 min: 0.384 cfs. Off-line facility target flow: 0.2131 cfs. Adjusted for 15 min: 0.2131 cfs. ___________________________________________________________________ LID Report LID Technique Used for Total Volumn Volumn Infiltration Cumulative Percent Water Quality Percent Comment Treatment? Needs Through Volumn Volumn Volumn Water Quality Treatment Facility (ac-ft.) Infiltration Infiltrated Treated (ac-ft) (ac-ft) Credit Vault 1 POC N 546.68 N 0.00 Total Volume Infiltrated 546.68 0.00 0.00 0.00 0.00 0% No Treat. Credit Compliance with LID Standard 8 Duration Analysis Result = Failed ___________________________________________________________________ POC #2 was not reported because POC must exist in both scenarios and both scenarios must have been run. POC #3 was not reported because POC must exist in both scenarios and both scenarios must have been run. POC #4 was not reported because POC must exist in both scenarios and both scenarios must have been run.Perlnd and Implnd Changes No changes have been made. ___________________________________________________________________ This program and accompanying documentation are provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2018; All Rights Reserved. 2018 D. R. STRONG Consulting Engineers Inc. Page 52 Cedars at the Highlands Technical Information Report Renton, Washington WATER QUALITY TREATMENT SYSTEM The Project is required to adhere to the City of Renton’s Basic Water Quality treatment criteria. A Stormfilter immediately following the proposed detention vault in Tract A is proposed to accommodate this requirement. This information will be completed at the time of engineering. 2018 D. R. STRONG Consulting Engineers Inc. Page 53 Cedars at the Highlands Technical Information Report Renton, Washington FIGURE 17 DETENTION & WATER QUALITY FACILITY DETAILS (To be completed at time of final engineering) 2018 D. R. STRONG Consulting Engineers Inc. Page 54 Cedars at the Highlands Technical Information Report Renton, Washington SECTION V CONVEYANCE SYSTEM AN ALYSIS AND DESIGN Per Core Requirement #4 of the KCSWDM, the conveyance system must be analyzed and designed for the existing tributary and developed onsite runoff. Pipe systems shall be designed to convey the 25-year storm with a minimum of 6-inches of freeboard between the design water surface and structure grate. Any overflow from the 100-year design storm must not create or aggravate a severe flooding problem . The Rational Method will be used to calculate the Q-Ratio for each pipe node. A conveyance system consisting primarily of pipes and catch basins will be designed for the Project. Onsite runoff will be collected by the multiple catch basins. Pipes are typically six-inch to twelve-inch diameter LCPE material. 2018 D. R. STRONG Consulting Engineers Inc. Page 55 Cedars at the Highlands Technical Information Report Renton, Washington BACKWATER ANALYSIS (To be completed at time of final engineering) 2018 D. R. STRONG Consulting Engineers Inc. Page 56 Cedars at the Highlands Technical Information Report Renton, Washington SECTION VI SPECIAL REPORTS AND STUDIES The following report and studies have been provided with this submittal. Critical Areas Study: Sewell Wetland Consulting, Inc. – July 6, 2016 Subsurface Exploration and Geotechnical Engineering Report: Earth Solutions NW LLC – February 23, 2017 Geotechnical Infiltration Evaluation: Earth Solutions NW LLC – July 13, 2017 Arborist Report: Greenforest, Inc – March 20, 2016 Trip Generation Letter Report: Traffex – January 19, 2017 Conceptual Wetland Buffer Reduction and Enhancement Plan: Soundview Consultants – June 28, 2018 2018 D. R. STRONG Consulting Engineers Inc. Page 57 Cedars at the Highlands Technical Information Report Renton, Washington SECTION VII OTHER PERMITS  Request modification from RMC 4-6-060. Specifically, the half-street frontage improvements required for 162nd AVE SE. 2018 D. R. STRONG Consulting Engineers Inc. Page 58 Cedars at the Highlands Technical Information Report Renton, Washington SECTION VIII CSWPPP ANALYSIS AND DESIGN (PART A) The Erosion and Sedimentation Control Design will meet the seven minimum King County requirements: 1. Areas to remain undisturbed shall be delineated with a high visibility plastic fence prior to any site clearing or grading. 2. Site disturbed areas shall be covered with mulch and seeded, as appropriate, for temporary or permanent measures. 3. Perimeter protection shall consist of a silt fence down slope of any disturbed areas or stockpiles. 4. A stabilized construction entrance will be located at the point of ingress/egress (i.e. onsite access road). 5. The detention vault will act as a sediment pond for sediment retention. Perimeter silt fences will provide sediment retention within the bypass areas. 6. Surface water from disturbed areas will sheet flow to the sediment pond for treatment. 7. Dust control shall be provided by spraying exposed soils with water until wet. This is required when exposed soils are dry to the point that wind transport is possible which would impact roadways, drainage ways, surface waters, or neighboring residences. SWPPP PLAN DESIGN (PART B) Construction activities that could contribute pollutants to surface and storm water include the following, with applicable BMP’s listed for each item: 1. Storage and use of chemicals: Utilize source control, and soil erosion and sedimentation control practices, such as using only recommended amounts of chemical materials applied in the proper manner; neutralizing concrete wash water, and disposing of excess concrete material only in areas prepared for concrete placement, or return to batch plant; disposing of wash -up waters from water-based paints in sanitary sewer; disposing of wastes from oil -based paints, solvents, thinners, and mineral spirits only through a licensed waste management firm, or treatment, storage, and disposal (TSD) facility. 2. Material delivery and storage: Locate temporary storage areas away from vehicular traffic, near the construction entrance, and away from storm drains. Material Safety Data Sheets (MSDS) should be supplied for all materials stored, and chemicals kept in their original labeled containers. Maintenance, fueling, and repair of heavy equipment and vehicles shall be conducted using spill prevention and control measures. Contaminated surfaces shall be cleaned immediately following any spill incident. Provide cover, containment, and protection from vandalism for all chemicals, liquid products, petroleum products, and other potentially hazardous materials. 2018 D. R. STRONG Consulting Engineers Inc. Page 59 Cedars at the Highlands Technical Information Report Renton, Washington 3. Building demolition: Protect stormwater drainage system from sediment -laden runoff and loose particles. To the extent possible, use dikes, berms, or other methods to protect overland discharge paths from runoff. Street gutter, sidewalks, driveways, and other paved surfaces in the immediate area of demolition must be swept daily to collect and properly dispose of loose debris and garbage. Spray the minimum amount of water to help control windblown fine particles such as concrete, dust, and paint chips. Avoid excessive spraying so that runoff from the site does not occur, yet dust control is achieved. Oils must never be used for dust control. 4. Sawcutting: Slurry and cuttings shall be vacuumed during the activity to prevent migration offsite and must not remain on permanent concrete or asphalt paving overnight. Collected slurry and cuttings shall be disposed of in a manner that does not violate ground water or surface water quality standards. The complete CSWPPP to be completed at final engineering. 2018 D. R. STRONG Consulting Engineers Inc. Page 60 Cedars at the Highlands Technical Information Report Renton, Washington SECTION IX BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT 1. Bond Quantity Worksheet – will be submitted at final engineering 2. The Stormwater Facility Summary Sheet is included in this section. Lower Cedar RiverLower Cedar River14.1092.01287,64187,641087,641 Cedars at the Highlands14120 160th Avenue SE, Renton, WashingtonLower Cedar RiversLower Cedar River2.012100%TBDVault1.111.961.191155.716TBDTract A3 2018 D. R. STRONG Consulting Engineers Inc. Page 61 Cedars at the Highlands Technical Information Report Renton, Washington SECTION X OPERATIONS AND MAINTENANCE MANUAL The Home Owners Association will be responsible for maintenance of several private catch basins on various lots as depicted on the plans. Maintenance guidelines set forth in the 2017 CORSWDM are to be included at time of engineering. All other drainage elements are to be publicly maintained. 2018 D. R. STRONG Consulting Engineers Inc. Page 62 Cedars at the Highlands Technical Information Report Renton, Washington APPENDICES 2018 D. R. STRONG Consulting Engineers Inc. Page 63 Cedars at the Highlands Technical Information Report Renton, Washington APPENDIX “A” LEGAL DESCRIPTION LOT 6, BLOCK 3, CEDAR PARK FIVE ACRE TRACTS, ACCORDING TO PLAT THEREOF RECORDED IN VOLUME 15 OF PLATS, PAGE 91, RECORDS OF KING COUNTY, WASHINGTON. Greenforest Incorporated C o n s u l t i n g A r b o r i s t 4547 South Lucile Street, Seattle, WA 98118 Tel. 206-723-0656 TO: Chris Burrus Harbour Homes, LLC 1441 North 34th Street, Suite 200 Seattle WA 98103 REFERENCE: Arborist Report, Cedars at the Highlands SITE ADDRESS: 14120 160th Ave SE, Renton, WA 98059 DATE: March 20, 2017 PREPARED BY: Favero Greenforest, ISA Certified Arborist # PN -0143A ISA Tree Risk Assessment Qualified ASCA Registered Consulting Arborist® #379 You contacted me and contracted my services as a consulting arborist. My assignment is to inspect and assess the regulated trees at the above referenced site. I received a topographic survey from DR Strong, and I visited the site 2/10/2017 and inspected the trees, which are the subject of this report. The following table summarizes the tree quantities and categories inventoried in this report. Significant, Landmark and Dangerous categories are defined by municipal code. Landmark Trees On Site 19 Significant Trees On Site 170 Dangerous Trees On Site 85 Trees Within Sensitive Area 10 Total Trees On Site 284 Other Offsite Trees 24 Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 2 of 28 Greenforest Registered Consulting Arborist The site is 4.5 acres covered in native tree canopy. The understory is weedy and unmanaged. The roots and trunks of several trees are injured from mechanical equipment. Nearly thirty percent of the onsite trees have significant defects or visible decline, and are considered Dangerous by City code. LIMITATIONS AND USE OF THIS REPORT This tree report establishes, via the most practical means available, the existing conditions of the trees on the subject property. Ratings for health and structure, as well as any recommendations are valid only through the development and construction process. This report is based solely on what is readily visible and observable, without any invasive means. There are several conditions that can affect a tree’s condition that may be pre-existing and unable to be ascertained with a visual-only analysis. No attempt was made to determine the presence of hidden or concealed conditions which may contribute to the risk or failure potential of trees on the site. These conditions include root and stem (trunk) rot, internal cracks, structural defects or construction damage to roots, which may be hidden beneath the soil. Additionally, construction and post-construction circumstances can cause a relatively rapid deterioration of a tree’s condition. TREE INSPECTION I visually inspected each tree from the ground. I performed a Level 1 risk assessment.1 This is the standard assessment for populations of trees near specified targets, conducted in order to identify obvious defects or specified conditions such as a pre- development inventory. This is a limited visual assessment focuses on identifying trees with imminent and/or probable likelihood of failure, and/or other visible conditions that will affect tree retention. I recorded tree species and size (DBH). I estimated the average dripline of each tree. I rated the condition of each tree, both health and structure. A tree’s structure is distinct from its health. This inspection identifies what is visible with both. High-risk trees can appear healthy in that they can have a dense, green canopy. This may occur when there is sufficient sapwood or adventitious roots present to maintain tree health, but inadequate strength for structural support. 1 Companion publication to the ANSI A300 Part 9: Tree Shrub and Other woody Plant Management – Standard Practices, Tree Risk Assessment. 2011. ISA. Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 3 of 28 Greenforest Registered Consulting Arborist On the other hand, trees in poor health may or may not be structurally stable. For example, tree decline due to root disease is likely to cause the tree to be structurally unstable, while decline due to drought or insect attack may not. One way that tree health and structure are linked is that healthy trees are more capable of compensating for structural defects. A healthy tree can develop adaptive growth that adds strength to parts weakened by decay, cracks, and wounds. This report identifies unhealthy trees based on existing health conditions and tree structure, and specifies which trees are most suitable for preservation.2 The trees are not tagged and considerable effort was made to match the trees on the site with those on the survey. The attached tree inventory contains the following information on each tree. Retained Tree identifies the trees proposed for retention. Retention Priority shows the results of an analysis of retained trees according to priority of tree retention requirements specified in RMC §4-4-130H.1.b. Proposed for Removal identifies trees proposed for removal, and the reason for the necessary removal (diseased, or proposed site improvements- PSI). Tree number as shown on the attached site exhibit. DBH Stem (trunk) diameter in inches 4.5 feet from grade. Tree Category as defined by municipal code. TREE: A woody perennial usually having one dominant trunk, or, for certain species, a multi-stemmed trunk system, with a potential minimum height of ten feet (10') at maturity. Any trees listed on the Complete King County Weed List shall not qualify as a tree. Dangerous: Any tree that has been certified, in a written report, as dead, terminally diseased, damaged, or otherwise dangerous to persons or property by a licensed landscape architect, or certified arborist. Landmark: A tree with a caliper of thirty inches (30") or greater. (Average multiple stems and report single integer) 2 Companion publication to the ANSI A300 Part 5: Tree Shrub and Other woody Plant Maintenance – Standard Practices, Managing Trees During Construction. 2008. ISA. Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 4 of 28 Greenforest Registered Consulting Arborist Significant: A tree with a caliper of at least six inches (6"), or an alder or cottonwood tree with a caliper of at least eight inches (8"). Trees qualified as dangerous shall not be considered significant. Trees planted within the most recent ten (10) years shall qualify as significant trees, regardless of the actual caliper. Tree Species Common name. Dripline Average branch extension in feet as radius from the trunk. Health & Structure Rating ‘1’ indicates no visible health-related problems or structural defects; ‘2’ indicates minor visible problems or defects that may require attention or maintenance if the tree is retained, and/or the tree should only remain as a grove tree, and not stand alone; and ‘3’ indicates significant visible problems or defects and tree removal is recommended. Visible Defects Obvious structural defects or diseases visible at time of inspection, including: Asymmetric canopy– the tree has an asymmetric canopy from space and light competition from adjacent trees. Branch dieback - Mature branches in canopy are dying/dead. Bow in trunk – a trunk lean characterized by the top of the tree leaning over. (Common with edge trees) Crack – separation of wood fibers and predisposed to failure. Deadwood – Large and/or multiple dead branches throughout canopy. Decay – process of wood degradation by microorganisms resulting in weak and defective structure. Diseased – foliage and trunk/stems are diseased. Dogleg in trunk – trunk with a bow or defective bend (90°) in trunk often half way of further up the trunk. Double leader – the tree has multiple stem attachments, which may require maintenance or monitoring over time. Heave – the soil is heaving on one side of the tree from previous root/soil failure. Kretzschmaria – the tree is infected with a wood-decaying fungus as evidenced by conks growing on the base of the tree. Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 5 of 28 Greenforest Registered Consulting Arborist Multiple leaders - the tree has multiple stem attachments, which may lead to tree failure and require maintenance or monitoring over time. Previous failure – Tree trunk previously broken and defective. Self-corrected lean - Self-corrected leans and sweeps are characterized by a leaning lower trunk and a top that is more upright. Slender – tree lacks adequate trunk taper to stand lone. Stilts – tree grew atop a stump or nurselog, and has an elevated rootcrown. Stumpsprout- Tree previously cut at grade with multiple stems and potentially weak attachments. Suppressed – tree crowded by larger adjacent trees, with defective structure and/or low vigor. Retain tree only as a grove tree, not stand-alone. Sweep – tree leans away from adjacent trees. Characterized by a leaning lower trunk and a top that is more upright. Thinning Canopy – low foliage density may indicate stress, or early infection/declining health. Tree House – wooden structures fastened to trunk. Topped – the tree is previously topped and has poor structure and/or stem decay. Tree leans – Trunk has significant lean from vertical. Trunk decay - Wood decay is visible in the trunk. Woodpecker injury – the trunk is riddled with woodpecker holes. Wound/decay base of trunk - Open wound with visible decay in trunk. Location identifies if tree is within a building lot, Right-of-way, or sensitive area. Data for 24 offsite trees are also inventoried in a separate attachment. LIMITS OF DISTURBANCE FOR RETAINED TREES Limits of Disturbance (LOD) are calculated for all proposed retained significant trees. They are listed below as radii in feet from the trunk for the four cardinal sides of each tree. They are determined using rootplate 3 and trunk diameter,4,5 and ISA Best Management Practices.6 These are the minimum distances from the trees for any soil 3 Coder, Kim D. 2005. Tree Biomechanics Series. University of Georgia School of Forest Resources. 4 Smiley, E. Thomas, Ph. D. Assessing the Failure Potential of Tree Roots, Shade Tree Technical Report. Bartlett Tree Research Laboratories. 5 Fite, Kelby and E. Thomas Smiley. 2009. Managing Trees During construction; Part Two. Arborist News. ISA. 6 Companion publication to the ANSI A300 Series, Part 5: Managing Trees During Construction. 2008. ISA. Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 6 of 28 Greenforest Registered Consulting Arborist disturbance, and represent the area to be protected during construction. These LOD are malleable and may be adjusted further during the design and construction process. The following table lists the LOD of each retained tree. Table No. 1 – LOD as Radii In Feet From Tree Trunk for Proposed Retained Trees. Tree No. DBH Species DL Limits of Disturbance North East South West 12 21” Douglas-fir 16’ PL DL 10’ DL 5330 29” Douglas-fir 16’ DL DL PL DL 5331 8” Douglas-fir 12’ DL DL PL DL 5332 14” Douglas-fir 12’ DL DL PL DL 5333 28” Douglas-fir 16’ DL DL PL DL 5389 18” Western red-cedar 12’ PL DL 9’ DL 5404 10” Red alder 8’ DL DL PL DL 5453 10” Red alder 14’ DL DL DL DL 5469 25” Western red-cedar 14’ DL DL DL DL 5470 31” Western red-cedar 14’ PL DL DL DL 5471 58” Western red-cedar 18’ PL DL DL DL 5472 19” Douglas-fir 16’ DL DL 8’ DL 5473 11” Western red-cedar 10’ DL DL 6’ DL 5484 16” Douglas-fir 16’ DL DL 7’ DL 5485 45” Bigleaf maple 25’ DL DL 12’ DL 5486 45” Western red-cedar 18’ 20’ DL 20’ 15’ 5496 8” Western red-cedar 10’ PL DL 4’ DL 5524 10” Douglas-fir 14’ DL DL PL DL 5525 26” Douglas-fir 16’ DL DL PL DL 5526 11” Douglas-fir 12’ DL DL PL DL 5533 9” Douglas-fir 10’ DL DL PL DL 5534 9” Douglas-fir 10’ DL DL PL DL 5535 6” Douglas-fir 8’ DL DL PL DL 5536 22” Douglas-fir 14’ DL DL PL DL 5537 29” Douglas-fir 16’ 12’ DL PL DL 5570 13” Bigleaf maple 14’ DL DL PL DL 5571 9” Red alder 12’ 10’ 12 PL DL 5601 14” Bigleaf maple 16’ 7’ 9’ 7’ 9’ 5605 26” Bigleaf maple 20’ DL DL 11 12’ 5660 46” Western red-cedar 18’ DL DL 14 14’ 5694 25” Douglas-fir 18’ PL DL DL 14’ Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 7 of 28 Greenforest Registered Consulting Arborist Tree No. DBH Species DL Limits of Disturbance North East South West 5695 25” Douglas-fir 18’ PL DL DL 14’ 5696 32” Western red-cedar 16’ PL DL DL 14’ 5699 8” Red alder 10’ PL DL DL DL 5700 29” Black cottonwood 18’ PL DL DL DL 5701 14” Red alder 14’ PL DL DL DL 5703 10” Red alder 14’ PL DL DL DL 5704 21” Red alder 16’ PL DL DL DL 5705 10” Red alder 12’ PL DL DL DL 5706 10” Red alder 14’ PL DL DL DL 5708 10” Red alder 14’ PL DL DL DL 5709 8” Red alder 12’ PL DL DL DL 5710 8” Red alder 10’ PL DL DL DL 5711 10” Red alder 12’ PL DL DL DL 5712 24” Western red-cedar 14’ PL DL DL DL (PL=property line, DL = dripline) (DBH for multiple-trunked trees are reported as the quadratic mean diameter.) IMPACT OF NECESSARY TREE REMOVAL TO THE REMAINING TREES The proposed retained trees border both north and south project boundaries, as well as the sensitive area at the northeast corner. Most retained trees stand in contiguous formation with each other. Trees along the north and south boundaries have canopies contiguous with, or are protected by existing trees on the abutting parcels. The necessary tree removal should have negligible to no impact on the retained trees. SUPPLEMENTAL TREES The use of supplemental trees is still in the design phase. The suggested location and species, as well as planting and maintenance specifications, shall be addressed under separate cover. AN ANALYSIS OF TREE RETENTION PRIORITY REQUIREMENTS7 Retention priority for each proposed retained tree is provided in the attached tree inventory. 7 RMC. §4-4-130H.1.b Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 8 of 28 Greenforest Registered Consulting Arborist TREE PROTECTION MEASURES DURING CONSTRUCTION8 Protective fencing and required signage shall be installed prior to any site clearing and/or demolition. Fencing may be temporarily adjusted during the removal of trees adjacent to those retained. For development applications, protection measures must be in accordance with the tree protection standards as outlined in RMC 4-4-130.H.9, (and as excerpted below): §H.9. Protection Measures During Construction: Protection measures in this subsection shall apply for all trees that are to be retained. All of the following tree protection measures shall apply: a. Construction Storage Prohibited: The applicant may not fill, excavate, stack or store any equipment, dispose of any materials, supplies or fluids, operate any equipment, install impervious surfaces, or compact the earth in any way within the area defined by the drip line of any tree to be retained. b. Fenced Protection Area Required: Prior to development activities, the applicant shall erect and maintain six-foot (6') high chain link temporary construction fencing around the drip lines of all retained trees or at a distance surrounding the tree equal to one and one-quarter feet (1.25') for every one inch (1") of trunk caliper, whichever is greater, or along the perimeter of a tree protection tract. Placards shall be placed on fencing every fifty feet (50') indicating the words, “NO TRESPASSING – Protected Trees,” or on each side of the fencing if less than fifty feet (50'). Site access to individually protected trees or groups of trees shall be fenced and signed. Individual trees shall be fenced on four (4) sides. In addition, the applicant shall provide supervision whenever equipment or trucks are moving near trees. c. Protection from Grade Changes: If the grade level adjoining to a tree to be retained is to be raised, the applicant shall construct a dry rock wall or rock well around the tree. The diameter of this wall or well must be equal to the tree’s drip line. d. Impervious Surfaces Prohibited within the Drip Line: The applicant may not install impervious surface material within the area defined by the drip line of any tree to be retained. e. Restrictions on Grading within the Drip Lines of Retained Trees: The grade level around any tree to be retained may not be lowered within the greater of the following areas: (i) the area defined by the drip line of the tree, or (ii) an area around the tree equal to one and one-half feet (1-1/2') in diameter for each one inch (1") of tree caliper. A larger tree protection zone based 8 RMC. Excerpted from §4-4-130H9. Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 9 of 28 Greenforest Registered Consulting Arborist on tree size, species, soil, or other conditions may be required. (Ord. 5676, 12-3-2012) f. Mulch Layer Required: All areas within the required fencing shall be covered completely and evenly with a minimum of three inches (3") of bark mulch prior to installation of the protective fencing. Exceptions may be approved if the mulch will adversely affect protected ground cover plants. (Ord. 5676, 12-3-2012) g. Monitoring Required during Construction: The applicant shall retain a certified arborist or licensed landscape architect to ensure trees are protected from development activities and/or to prune branches and roots, fertilize, and water as appropriate for any trees and ground cover that are to be retained. Attachments: 1. Assumptions and Limiting Conditions 2. Certificate of Performance 3. Significant Tree Inventory 4. Offsite Trees 5. Tree Cutting and Land Clearing Plan Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 10 of 28 Greenforest Registered Consulting Arborist Attachment No. 1 - Assumptions & Limiting Conditions 1) A field examination of the site was made 2/10/2017. My observations and conclusions are as of that date. 2) Care has been taken to obtain all information from reliable sources. All data has been verified insofar as possible; however, the consultant/arborist can neither guarantee nor be responsible for the accuracy of information provided by others. 3) Unless stated other wise: 1) information contained in this report covers only those trees that were examined and reflects the condition of those trees at the time of inspection; and 2) the inspection is limited to visual examination of the subject trees without dissection, excavation, probing, or coring. There is no warranty or guarantee, expressed or implied that problems or deficiencies of the subject tree may not arise in the future. 4) The consultant/appraiser shall not be required to give testimony or to attend court by reason of this report unless subsequent contractual arrangements are made. 5) Loss or alteration of any part of this report invalidates the entire report. 6) Unless required by law otherwise, possession of this report or a copy thereof does not imply right of publication or use for any purpose by any other than the person to whom it is addressed, without the prior expressed written or verbal consent of the consultant/appraiser. 7) Construction activities can impact trees in unpredictable ways. All retained trees should be inspected at the completion of construction, and regularly thereafter as part of ongoing maintenance. 8) All trees possess the risk of failure. Trees can fail at any time, with or without obvious defects, and with or without applied stress. Any treatments performed to abate current defects do not eliminate said defects, nor does it provide any guarantee against failure. Sometimes trees fail because they are trees. 9) The consultant does not assume any liability for the subject tree and does not represent the transfer of such for any risks associated with the tree from the landowner to the consultant. Risk management is solely the responsibility of the landowner. Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 11 of 28 Greenforest Registered Consulting Arborist Attachment No. 2 - Certification of Performance I, Favero Greenforest, certify that: • I have personally inspected the trees and the property referred to in this report and have stated my findings accurately. • I have no current or prospective interest in the vegetation or the property that is the subject of this report and have no personal interest or bias with respect to the parties involved. • The analysis, opinion, and conclusions stated herein are my own and are based on current scientific procedures and facts. • My analysis, opinion, and conclusions were developed and this report has been prepared according to commonly accepted arboricultural practices. • No one provided significant professional assistance to me, except as indicated within the report. • My compensation is not contingent upon the reporting of a predetermined conclusion that favors the cause of the client of any other party nor upon the results of the assessment, the attainment of stipulated results, or the occurrence of any subsequent events. I further certify that I am a member in good standing of International Society of Arboriculture (ISA), and the ISA PNW Chapter, I am an ISA Certified Arborist (#PN- 0143A) and am Tree Risk Assessment Qualified, and am a Registered Consulting Arborist® (#379) with American Society of Consulting Arborists. I have worked as an independent consulting arborist since 1989. Signed: GREENFOREST, Inc. By Favero Greenforest, M. S. Date: March 20, 2017 Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 12 of 28 Greenforest Registered Consulting Arborist Attachment No. 3 – Significant Tree Inventory Retained Tree Retention Priority Proposed for Removal Tree No. DBH Category Species Dripline Health Structure Visible Defects Location PSI 1 14 Significant Douglas-fir 10 1 1 Lot PSI 2 18 Significant Douglas-fir 14 1 1 Lot Decay 3 8 Dangerous Red alder 10 3 3 Lean, decay Lot Decay 4 8 Dangerous Red alder 10 3 3 Lean, decay Lot PSI 5 6 Significant Douglas-fir 8 2 1 Suppressed Lot PSI 6 12 Significant Douglas-fir 10 1 2 Asymmetric Lot PSI 7 6 Significant Douglas-fir 8 2 1 Suppressed Lot PSI 8 8 Significant Western red-cedar 10 1 1 Lot Sensitive Area 9 8,14 Significant Bigleaf maple 14 1 3 Decay Sensitive Decay 10 16 Significant Red alder 16 2 3 Lean, decay Lot Decay 11 9 Dangerous Red alder 12 1 3 Decay Lot RETAIN 1.ii 12 21 Significant Douglas-fir 16 1 1 Lot Decay 13 10,10,10 Dangerous Red alder 10 1 3 Previous failure, dead trunk, tree house Lot Decay 14 13 Dangerous Red alder 8 3 3 Trunk decay, decline, branch failure Lot Sensitive Area 5104 10,12 Significant Bigleaf maple 14 1 2 Slender Sensitive Sensitive Area 5105 32 Landmark Douglas-fir 16 1 1 Sensitive Sensitive Area 5115 36 Landmark Western red-cedar 18 1 1 Sensitive Sensitive Area 5116 11 Significant Red alder 12 1 2 Slender Sensitive Sensitive Area 5122 16,18,24 Dangerous Bigleaf maple 20 1 3 Deadwood, decay Sensitive Sensitive Area 5131 24,24 Dangerous Bigleaf maple 30 3 3 Kretzschmaria fungus Sensitive Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 13 of 28 Greenforest Registered Consulting Arborist Retained Tree Retention Priority Proposed for Removal Tree No. DBH Category Species Dripline Health Structure Visible Defects Location PSI 5284 20 Significant Douglas-fir 16 1 1 Lot PSI 5285 16 Significant Douglas-fir 16 1 2 Asymmetric Lot Unhealthy 5286 8 Dangerous Red alder 10 2 3 Suppressed, decline Lot PSI 5287 10 Significant Douglas-fir 10 1 2 Slender Lot Decline 5288 14 Dangerous Red alder 10 3 3 Decline, deadwood, lean Lot PSI 5289 13 Significant Douglas-fir 10 1 2 Double leader Lot PSI 5290 20 Significant Douglas-fir 16 1 1 Lot PSI 5291 18 Significant Douglas-fir 16 1 2 Double leader ROW PSI 5292 20 Significant Douglas-fir 14 1 1 ROW PSI 5294 24 Significant Douglas-fir 16 1 1 ROW PSI 5295 7 Significant Western red-cedar 10 1 1 ROW PSI 5296 10 Significant Black cottonwood 10 2 1 Dogleg ROW Failure 5297 8,12,14 Dangerous Black cottonwood 16 1 3 Previous failure, multiple leader ROW PSI 5298 10 Significant Black cottonwood 12 1 1 ROW PSI 5299 9 Significant Black cottonwood 10 1 1 ROW PSI 5300 12 Significant Douglas-fir 10 2 1 Thin canopy ROW Decline 5301 8 Dangerous Douglas-fir 12 3 3 Decline, failure Lot Unhealthy 5302 8 Dangerous Black cottonwood 10 2 3 Decline, slender, trunk wound Lot Unhealthy 5303 16 Dangerous Douglas-fir 10 3 1 Decline, trunk wound Lot Decay 5304 10 Dangerous Red alder 12 1 3 Suppressed, lean, ivy, decay Lot Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 14 of 28 Greenforest Registered Consulting Arborist Retained Tree Retention Priority Proposed for Removal Tree No. DBH Category Species Dripline Health Structure Visible Defects Location PSI 5305 27 Significant Douglas-fir 16 2 2 Thin canopy, asymmetric, trunk wound Lot PSI 5306 11 Significant Douglas-fir 6 2 1 Suppressed Lot PSI 5307 20 Significant Douglas-fir 14 1 2 Asymmetric Lot PSI 5308 14 Significant Red alder 16 2 1 Deadwood Lot PSI 5309 20 Significant Douglas-fir 14 1 2 Asymmetric Lot PSI 5310 24 Significant Douglas-fir 16 1 2 Asymmetric Lot RETAIN 1.ii 5330 29 Significant Douglas-fir 16 1 1 Lot RETAIN 1.ii 5331 8 Significant Douglas-fir 12 1 2 Asymmetric Lot RETAIN 1.ii 5332 14 Significant Douglas-fir 12 1 2 Suppressed Lot RETAIN 1.ii 5333 28 Significant Douglas-fir 16 1 1 Lot PSI 5337 32 Landmark Black cottonwood 30 1 1 Lot PSI 5341 18 Significant Western red-cedar 16 1 1 Lot PSI 5345 20 Significant Douglas-fir 14 1 2 Asymmetric Lot PSI 5346 20 Significant Douglas-fir 14 1 2 Asymmetric Lot PSI 5347 10 Significant Douglas-fir 10 1 1 Lot PSI 5348 7 Significant Douglas-fir 6 2 1 Suppressed Lot PSI 5349 8 Significant Douglas-fir 10 1 1 Lot PSI 5351 11 Significant Douglas-fir 10 2 2 Suppressed Lot PSI 5352 28 Significant Black cottonwood 18 1 1 Lot PSI 5353 14 Significant Douglas-fir 12 1 1 Lot PSI 5354 10,25 Significant Douglas-fir 16 1 2 Asymmetric, Lot Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 15 of 28 Greenforest Registered Consulting Arborist Retained Tree Retention Priority Proposed for Removal Tree No. DBH Category Species Dripline Health Structure Visible Defects Location deadwood PSI 5355 7 Significant Douglas-fir 4 2 1 Suppressed Lot PSI 5356 22 Significant Douglas-fir 14 1 1 Lot PSI 5357 8 Significant Douglas-fir 12 2 1 Suppressed Lot Decay 5358 9 Dangerous Red alder 14 1 3 Trunk injury, decay Lot Failure 5359 8 Dangerous Red alder 10 2 3 Decline, trunk failure Lot Decay 5361 9 Dangerous Douglas-fir 3 3 3 Previous failure, trunk decay, nearly dead Lot PSI 5363 16 Significant Black cottonwood 14 1 2 Double leader ROW PSI 5364 10 Significant Black cottonwood 12 1 1 ROW PSI 5365 8 Significant Black cottonwood 10 1 2 Asymmetric ROW PSI 5366 14 Significant Black cottonwood 16 1 1 ROW PSI 5367 10 Significant Black cottonwood 12 1 2 Asymmetric, slender Lot Decay 5368 20,28 Dangerous Western red-cedar 3 3 3 Decline, decay, nearly dead Lot Decline 5369 28 Dangerous Western red-cedar 10 3 3 Decline, nearly dead Lot PSI 5372 20 Significant Black cottonwood 16 1 1 Lot PSI 5373 34 Landmark Black cottonwood 20 1 1 Lot PSI 5374 24,36 Landmark Black cottonwood 20 1 2 Double leader Lot PSI 5375 18 Significant Black cottonwood 10 2 1 Suppressed Lot Decay 5376 21 Dangerous Black cottonwood 16 1 3 Trunk injury, decay Lot Decay 5377 16 Dangerous Black cottonwood 14 1 3 Rootcrown injury, decay Lot Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 16 of 28 Greenforest Registered Consulting Arborist Retained Tree Retention Priority Proposed for Removal Tree No. DBH Category Species Dripline Health Structure Visible Defects Location Decay 5378 22 Dangerous Black cottonwood 14 1 3 Rootcrown injury, decay Lot Decay 5379 22 Dangerous Black cottonwood 14 1 3 Rootcrown injury, decay Lot PSI 5380 38 Landmark Western red-cedar 16 1 1 Lot PSI 5381 26 Significant Western red-cedar 16 1 2 Rootcrown injury Lot Failure 5382 18 Dangerous Bigleaf maple 14 1 3 Asymmetric, sweep, previous failure Lot PSI 5384 37 Landmark Western red-cedar 16 1 2 Multiple leader, rootcrown injury Lot PSI 5385 40 Landmark Western red-cedar 16 1 2 Multiple leader, rootcrown injury Lot Decay 5386 29 Dangerous Western red-cedar 14 1 3 Trunk injury, decay Lot Unhealthy 5387 8, 14 Dangerous Bigleaf maple 16 3 2 Double leader, suppressed Lot PSI 5388 35 Landmark Western red-cedar 16 1 1 Lot RETAIN 2.ii 5389 18 Significant Western red-cedar 12 1 2 Asymmetric Lot Decay 5394 12 Dangerous Douglas-fir 10 1 3 Slender, trunk decay Lot PSI 5398 9 Significant Douglas-fir 10 2 2 Suppressed, trunk decay Lot RETAIN 2.ii 5404 10 Significant Red alder 8 2 2 Decline, slender Lot PSI 5405 18 Significant Douglas-fir 16 1 1 Lot PSI 5406 16 Significant Douglas-fir 14 1 1 Lot Decline 5407 12 Dangerous Bigleaf maple 8 3 3 Decline, disease, decay Lot Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 17 of 28 Greenforest Registered Consulting Arborist Retained Tree Retention Priority Proposed for Removal Tree No. DBH Category Species Dripline Health Structure Visible Defects Location Decay 5411 7 Dangerous Bigleaf maple 3 3 Decline, previous failure, decay Lot Decay 5429 22 Significant Black cottonwood 13 1 3 Rootcrown injury Lot PSI 5430 20 Significant Black cottonwood 14 1 1 ROW PSI 5431 22 Significant Black cottonwood 16 1 1 ROW PSI 5432 10 Significant Black cottonwood 8 1 2 Suppressed ROW Decay 5433 6 Dangerous Bigleaf maple 8 3 3 Disease, decay ROW Decay 5435 10 Dangerous Black cottonwood 12 1 3 Trunk injury ROW PSI 5436 10,14,18 Significant Black cottonwood 18 1 2 Multiple leader ROW Decay 5438 14 Dangerous Black cottonwood 12 1 3 Suppressed, trunk injury Lot PSI 5439 19 Significant Black cottonwood 16 1 1 Lot PSI 5440 14 Significant Black cottonwood 12 1 2 Slender Lot Injured 5441 32 Dangerous Black cottonwood 18 1 3 Trunk fracture Lot PSI 5442 28 Significant Black cottonwood 20 1 1 Lot Decay 5443 12 Dangerous Red alder 10 3 3 Decline, decay Lot Unhealthy 5444 14 Dangerous Western red-cedar 10 3 2 Decline, suppressed Lot Unhealthy 5445 18 Dangerous Western red-cedar 10 3 2 Decline, suppressed Lot Unhealthy 5446 11 Dangerous Western red-cedar 10 3 2 Decline, suppressed Lot PSI 5447 14 Significant Western red-cedar 12 1 2 Asymmetric Lot PSI 5448 11 Significant Western red-cedar 6 2 2 Suppressed, girdled Lot PSI 5449 21 Significant Western red-cedar 14 1 1 Lot PSI 5450 16 Significant Western red-cedar 14 1 2 Asymmetric Lot Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 18 of 28 Greenforest Registered Consulting Arborist Retained Tree Retention Priority Proposed for Removal Tree No. DBH Category Species Dripline Health Structure Visible Defects Location PSI 5451 6 Significant Western red-cedar 6 2 2 Suppressed, on stilts Lot RETAIN 1.ii 5453 10 Significant Red alder 14 1 2 Slender Lot Injured 5454 12 Dangerous Western red-cedar 10 2 3 Thin canopy, asymmetric, woodpecker Lot PSI 5455 16 Significant Red alder 14 1 1 Lot PSI 5456 20 Significant Western red-cedar 16 1 2 Asymmetric Lot Unhealthy 5458 11 Dangerous Western red-cedar 8 3 2 Nearly dead, sweep Lot PSI 5459 26 Significant Douglas-fir 18 1 2 Self correcting lean Lot Unhealthy 5460 10 Dangerous Western red-cedar 8 2 3 Suppressed, asymmetric, woodpecker Lot Failure 5461 8 Dangerous Western red-cedar 8 1 3 Trunk failure Lot PSI 5462 14 Significant Red alder 14 1 2 Asymmetric, root lifted Lot PSI 5463 10 Significant Western red-cedar 12 2 2 Suppressed, asymmetric, woodpecker Lot PSI 5464 16 Significant Western red-cedar 12 2 1 Suppressed, growth obstruction Lot PSI 5464.5 16 Significant Douglas-fir 12 1 2 Growth obstruction Lot PSI 5465 11 Significant Western red-cedar 10 1 2 Asymmetric, growth obstruction Lot PSI 5465.5 18 Significant Douglas-fir 14 1 2 Dogleg Lot PSI 5466 10 Significant Western red-cedar 6 2 1 Suppressed Lot Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 19 of 28 Greenforest Registered Consulting Arborist Retained Tree Retention Priority Proposed for Removal Tree No. DBH Category Species Dripline Health Structure Visible Defects Location Leaning 5467 10 Dangerous Red alder 14 1 3 Slender, lean Lot Leaning 5468 10 Dangerous Red alder 14 1 3 Slender, lean Lot RETAIN 1.ii 5469 25 Significant Western red-cedar 14 1 2 Asymmetric Lot RETAIN 1.ii 5470 31 Landmark Western red-cedar 14 1 1 Lot RETAIN 1.ii 5471 58 Landmark Western red-cedar 18 1 2 Double leader Lot RETAIN 1.ii 5472 19 Significant Douglas-fir 16 1 2 Slender Lot RETAIN 1.ii 5473 11 Significant Western red-cedar 10 2 1 Suppressed Lot PSI 5475 10 Significant Western red-cedar 6 2 2 Suppressed, on stilts Lot PSI 5476 12 Significant Western red-cedar 10 1 2 Asymmetric Lot PSI 5477 7 Significant Western red-cedar 6 1 2 Asymmetric Lot PSI 5478 29 Significant Western red-cedar 16 1 2 Asymmetric, sweep Lot PSI 5479 27 Significant Western red-cedar 16 1 1 Lot PSI 5480 6 Significant Western red-cedar 8 1 2 Suppressed, sweep Lot Failure 5481 11 Dangerous Red alder 16 1 3 Asymmetric, heave Lot PSI 5482 10 Significant Western red-cedar 10 1 2 Sweep, asymmetric Lot Decay 5483 12 Dangerous Western red-cedar 10 1 3 Soil heave, previous failure Lot RETAIN 1.ii 5484 16 Significant Douglas-fir 16 2 2 Suppressed Lot RETAIN 1.ii 5485 45 Landmark Bigleaf maple 25 1 2 Double leader Lot RETAIN 1.ii 5486 45 Landmark Western red-cedar 18 1 1 Lot PSI 5487 38 Landmark Western red-cedar 16 1 2 Asymmetric Lot PSI 5488 38 Landmark Western red-cedar 16 1 2 Asymmetric Lot Failure 5489 10 Dangerous Red alder 10 2 3 Decline, previous Lot Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 20 of 28 Greenforest Registered Consulting Arborist Retained Tree Retention Priority Proposed for Removal Tree No. DBH Category Species Dripline Health Structure Visible Defects Location failure Failure 5490 11 Dangerous Red alder 8 3 3 Decline, failure Lot Decay 5491 8 Dangerous Red alder 10 1 3 Previous failure Lot Decay 5492 11 Dangerous Black cottonwood 14 1 3 Slender, crack Lot PSI 5493 16 Significant Western red-cedar 8 1 2 Asymmetric, rootcrown injury Lot PSI 5494 33 Landmark Western red-cedar 16 1 1 Lot PSI 5495 40 Landmark Western red-cedar 16 1 1 Lot RETAIN 2.ii 5496 8 Significant Western red-cedar 10 1 1 Lot Decay 5498 20 Dangerous Douglas-fir 16 1 3 Root severed ROW Decay 5499 15 Dangerous Douglas-fir 12 1 3 Root severed ROW Decay 5500 8 Dangerous Red alder 14 1 3 Asymmetric, trunk decay, root severed ROW Decay 5501 10 Dangerous Red alder 8 1 3 Lean, slender ROW Decay 5502 18 Dangerous Western red-cedar 12 1 3 Root severed Lot Decay 5503 14, 12 Dangerous Apple 10 3 3 Disease, previous failure Lot Decay 5504 8,10 Dangerous Red alder 10 3 3 Decline, suppressed, double leader ROW PSI 5505 20 Significant Douglas-fir 16 2 1 Thin canopy ROW Decay 5506 6 Dangerous Douglas-fir 8 1 3 Suppressed, trunk decay ROW PSI 5507 21 Significant Douglas-fir 14 1 1 ROW PSI 5508 14 Significant Douglas-fir 16 1 1 ROW Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 21 of 28 Greenforest Registered Consulting Arborist Retained Tree Retention Priority Proposed for Removal Tree No. DBH Category Species Dripline Health Structure Visible Defects Location PSI 5509 11 Significant Black cottonwood 14 1 2 Slender Lot Decay 5510 22 Dangerous Black cottonwood 16 1 3 Trunk wound Lot PSI 5511 10 Significant Red alder 14 1 2 Trunk decay Lot PSI 5512 9 Significant Douglas-fir 8 2 1 Thin canopy Lot PSI 5513 10 Significant Douglas-fir 14 1 2 Asymmetric Lot PSI 5514 21 Significant Douglas-fir 14 2 1 Thin canopy Lot PSI 5516 18,20 Significant Douglas-fir 18 1 2 Double leader Lot PSI 5517 10 Significant Douglas-fir 6 2 2 Suppressed, asymmetric Lot PSI 5518 27 Significant Douglas-fir 18 1 2 Asymmetric Lot PSI 5519 28 Significant Douglas-fir 18 1 1 Lot PSI 5521 14 Significant Black cottonwood 16 1 1 Lot PSI 5522 9 Significant Douglas-fir 6 2 1 Suppressed Lot PSI 5523 25 Significant Douglas-fir 16 1 1 Lot RETAIN 1.ii 5524 10 Significant Douglas-fir 14 1 2 Asymmetric Lot RETAIN 1.ii 5525 26 Significant Douglas-fir 16 1 1 Lot RETAIN 1.ii 5526 11 Significant Douglas-fir 12 1 2 Dogleg Lot Failure 5528 10 Dangerous Red alder 12 3 3 Decline, previous failure Lot Decay 5531 8 Dangerous Red alder 6 3 3 Decline, slender Lot PSI 5532 28,28 Significant Douglas-fir 18 1 2 Double leader Lot RETAIN 1.ii 5533 9 Significant Douglas-fir 10 1 2 Asymmetric, topped Lot RETAIN 1.ii 5534 9 Significant Douglas-fir 10 1 2 Asymmetric, topped Lot Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 22 of 28 Greenforest Registered Consulting Arborist Retained Tree Retention Priority Proposed for Removal Tree No. DBH Category Species Dripline Health Structure Visible Defects Location RETAIN 1.ii 5535 6 Significant Douglas-fir 8 2 2 Suppressed, asymmetric Lot RETAIN 1.ii 5536 22 Significant Douglas-fir 14 1 2 Asymmetric Lot RETAIN 1.ii 5537 16,24 Significant Douglas-fir 16 1 2 Double leader Lot Unhealthy 5538 10 Dangerous Red alder 16 3 2 Decline, decay Lot PSI 5539 18 Significant Black cottonwood 20 1 1 Lot PSI 5541 27 Significant Douglas-fir 18 1 1 Lot PSI 5542 14 Significant Douglas-fir 12 1 1 Lot PSI 5543 9 Significant Douglas-fir 10 1 2 Double leader Lot Failure 5544 8,8,10 Dangerous Red alder 12 3 3 Decline, failure Lot PSI 5545 16 Significant Douglas-fir 14 1 1 Lot Failure 5546 8,8 Dangerous Apple 0 3 3 Split asunder Lot PSI 5547 11 Significant Douglas-fir 10 1 1 ROW Decay 5548 8 Dangerous Red alder 6 3 3 Decline, decay Lot PSI 5549 12 Significant Douglas-fir 12 1 2 Asymmetric Lot PSI 5550 22 Significant Douglas-fir 16 1 1 Lot PSI 5551 14 Significant Black cottonwood 16 1 1 ROW PSI 5552 16,18 Significant Black cottonwood 20 1 2 Double leader ROW PSI 5553 12 Significant Bigleaf maple 14 1 1 ROW PSI 5554 14,20 Significant Black cottonwood 16 1 2 Small leader is dead Lot PSI 5555 16 Significant Black cottonwood 14 1 2 Dogleg, failure Lot PSI 5556 9 Significant Black cottonwood 12 1 2 Suppressed Lot Decay 5557 10 Dangerous Black cottonwood 12 1 3 Suppressed ROW Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 23 of 28 Greenforest Registered Consulting Arborist Retained Tree Retention Priority Proposed for Removal Tree No. DBH Category Species Dripline Health Structure Visible Defects Location PSI 5558 18 Significant Black cottonwood 16 1 2 Asymmetric ROW Decay 5559 16, 20 Dangerous Black cottonwood 25 1 3 Double leader, failure ROW PSI 5560 22,24 Significant Black cottonwood 18 1 2 Double leader Lot PSI 5561 22 Significant Black cottonwood 20 1 1 ROW Decay 5562 25 Dangerous Black cottonwood 20 1 3 Trunk decay ROW PSI 5563 12 Significant Black cottonwood 14 1 2 Asymmetric ROW PSI 5564 20, 24 Significant Black cottonwood 25 1 2 Double leader ROW PSI 5565 16,18 Significant Black cottonwood 18 1 2 Dogleg, double leader Lot PSI 5566 18 Significant Black cottonwood 18 1 1 Lot PSI 5567 22 Significant Black cottonwood 25 1 2 Previous failure, double leader ROW Decay 5568 20 Dangerous Black cottonwood 14 2 3 Decline, decay Lot Decay 5569 12 Dangerous Red alder 14 2 3 Decline, decay Lot RETAIN 1.ii 5570 8,10 Significant Bigleaf maple 14 2 1 Disease Lot RETAIN 1.ii 5571 9 Significant Red alder 12 1 2 Lean Lot Unhealthy 5572 10 Dangerous Red alder 10 3 2 Disease, lean Lot Decay 5575 12 Dangerous Red alder 10 2 3 Decline, decay Lot Decay 5576 10 Dangerous Red alder 12 2 3 Decline, decay Lot Decay 5578 10,10 Dangerous Red alder 12 3 3 Decline, decay Lot PSI 5579 22 Significant Bigleaf maple 18 1 1 Lot Decay 5580 10,10 Dangerous Red alder 14 3 3 Decline, decay Lot Decay 5600 10 Dangerous Apple 8 3 3 Decline, decay Lot RETAIN 1.ii 5601 14 Significant Bigleaf maple 16 1 1 Lot Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 24 of 28 Greenforest Registered Consulting Arborist Retained Tree Retention Priority Proposed for Removal Tree No. DBH Category Species Dripline Health Structure Visible Defects Location PSI 5603 11 Significant Red alder 12 1 2 Slender Lot Decay 5604 10 Dangerous Red alder 12 3 3 Decline, decay Lot RETAIN 1.ii 5605 26 Significant Bigleaf maple 20 1 2 Deadwood Lot PSI 5606 11 Significant Red alder 14 1 1 Lot PSI 5607 44 Landmark Douglas-fir 20 1 1 Lot PSI 5608 16 Significant Douglas-fir 14 1 2 Asymmetric Lot PSI 5609 8 Significant Red alder 10 1 2 Sweep Lot Decay 5610 11 Dangerous Red alder 12 1 3 Trunk decay Lot Decay 5611 8 Dangerous Red alder 10 1 3 Failure, lean Lot PSI 5612 14 Significant Douglas-fir 12 1 2 Double leader Lot Decay 5613 10 Dangerous Red alder 12 1 3 Previous failure Lot Decay 5614 8,8,10,10 Dangerous Red alder 16 2 3 Decline, decay Lot PSI 5616 20 Significant Douglas-fir 16 1 1 Lot PSI 5617 9 Significant Bigleaf maple 16 1 2 Sweep Lot PSI 5621 8,10 Significant Red alder 10 1 1 Lot PSI 5622 11 Significant Red alder 14 1 2 Asymmetric Lot Decay 5624 30,30,36 Dangerous Bigleaf maple 35 1 3 Decay Lot RETAIN 1.iv 5660 46 Landmark Western red-cedar 18 1 1 Lot Sensitive Area 5661 38 Landmark Western red-cedar 18 1 1 Sensitive Sensitive Area 5662 34 Landmark Western red-cedar 18 1 2 Asymmetric Sensitive Sensitive Area 5663 33 Landmark Western red-cedar 14 1 1 Sensitive PSI 5664 17 Significant Douglas-fir 16 1 1 Lot Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 25 of 28 Greenforest Registered Consulting Arborist Retained Tree Retention Priority Proposed for Removal Tree No. DBH Category Species Dripline Health Structure Visible Defects Location Decay 5666 10,10 Dangerous Red alder 12 2 3 Decline, decay Lot PSI 5667 12 Significant Red alder 10 2 1 Decline ROW Decay 5668 10 Dangerous Red alder 8 3 3 Decline, decay ROW Unhealthy 5669 8 Dangerous Red alder 10 3 1 Decline ROW Decay 5692 10,10,12, 12,14,14, 14 Dangerous Bigleaf maple 25 1 3 Trunk decay stumpsprout Lot PSI 5693 34 Landmark Douglas-fir 18 1 1 Lot RETAIN 1.ii 5694 25 Significant Douglas-fir 18 1 2 Asymmetric Lot RETAIN 1.ii 5695 25 Significant Douglas-fir 18 1 2 Asymmetric Lot RETAIN 1.ii 5696 32 Landmark Western red-cedar 16 1 2 Asymmetric, seam in trunk Lot Decay 5698 10,10 Dangerous Red alder 14 1 3 Double leader, lean, rootcrown decay Lot RETAIN 1.ii 5699 8 Significant Red alder 10 1 2 Slender Lot RETAIN 1.ii 5700 29 Significant Black cottonwood 18 1 1 Lot RETAIN 1.ii 5701 10,10 Significant Red alder 14 1 2 Decline Lot RETAIN 1.ii 5703 10 Significant Red alder 14 1 2 Asymmetric Lot RETAIN 1.ii 5704 9,10,11,1 2 Significant Red alder 16 1 2 Deadwood Lot RETAIN 1.ii 5705 10 Significant Red alder 12 1 1 Lot RETAIN 1.ii 5706 10 Significant Red alder 14 1 1 Lot Decay 5707 10 Dangerous Red alder 12 2 3 Decline, decay Lot RETAIN 1.ii 5708 10 Significant Red alder 14 2 1 Decline Lot Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 26 of 28 Greenforest Registered Consulting Arborist Retained Tree Retention Priority Proposed for Removal Tree No. DBH Category Species Dripline Health Structure Visible Defects Location RETAIN 1.ii 5709 8 Significant Red alder 12 1 2 Asymmetric Lot RETAIN 1.ii 5710 8 Significant Red alder 10 1 2 Slender Lot RETAIN 1.ii 5711 10 Significant Red alder 12 1 1 Lot RETAIN 1.ii 5712 24 Significant Western red-cedar 14 1 1 Lot DBH – diameter 4.5 feet from grade. Dripline – radius in feet from trunk. PSI – proposed site improvements. Chris Burrus, Harbour Homes, LLC RE: Arborist Report, Cedars at the Highlands, 14120 160th Ave SE, Renton, WA 98059 March 20, 2017 Page 27 of 28 Greenforest Registered Consulting Arborist Attachment No. 4 – Offsite Trees Tree No. Category DBH Species Dripline Health Structure Visible Defects 5283 Significant 28 Cottonwood 18 1 1 5293 Significant 12 Cottonwood 14 1 1 5311 Significant 22 Fir 16 1 2 Asymmetric 5312 Significant 12 Fir 6 1 2 Suppressed 5313 Significant 18 Fir 14 1 2 Asymmetric 5314 Significant 28 Fir 16 1 1 5315 Significant 22 Cedar 12 1 1 5338 Dangerous 35 Cedar 12 3 3 Decline, nearly dead 5339 Dangerous 20,35 Maple 25 2 3 Deadwood, decline, decay 5342 Significant 22,28 Cedar 16 1 2 Double leader 5390 Significant 27 Cedar 12 1 2 Multiple leader 5529 Dangerous 7 Fir 8 2 3 Suppressed, topped 5618 Dangerous 8 Alder 14 3 3 Decline, decay, lean 5619 0 3 3 Dead 5620 Significant 20 Fir 16 1 1 5623 Dangerous 58 Cedar 18 1 3 Decay, failure of attachment, large wound on trunk 5625 Significant 6 Cedar 8 1 1 5626 Landmark 33 Cedar 16 2 1 Chlorotic foliage 5627 Significant 8 Cedar 8 1 1 5628 Significant 11 Cedar 10 1 1 5629 Significant 12 Cedar 14 1 2 Asymmetric, double leader 5630 Landmark 32 Cedar 16 2 1 Thin foliage, chlorosis 5631 Significant 11 Cedar 12 1 2 Asymmetric, sweep 5697 Landmark 36 Cedar 18 1 2 Asymmetric CEDARS AT THE HIGHLANDS14120 160TH AVENUE SERENTON, WASHINGTON 98059CEDARS AT THE HIGHLANDS CEDARS AT THE HIGHLANDS AAANNNNNNN LUA:U:DRS PROJECT NO. 16041A-NNNNNNNNS ERISSEFORPINGOERDETSREENG I NELA53232 OI ET A T H SOY SFOTGNIHASWIDEIPL.OCILAZPRELIMINARY PLAT0GRAPHIC SCALE15'30'60'1 INCH = 30 FT. DEPARTMENT OF COMMUNITY AND ECONOMIC DEVELOPMENT TREE RETENTION WORKSHEET Planning Division 1055 South Grady Way-Renton, WA 98057 Phone: 425-430-7200 | www.rentonwa.gov 1.Total number of trees over 6” diameter 1, or alder or cottonwood trees at least 8” in diameter on project site trees 2.Deductions: Certain trees are excluded from the retention calculation: Trees that are dangerous 2 trees Trees in proposed public streets trees Trees in proposed private access easements/tracts trees Trees in critical areas3 and buffers trees Total number of excluded trees: trees 3.Subtract line 2 from line 1:trees 4.Next, to determine the number of trees that must be retained 4, multiply line 3 by: 0.3 in zones RC, R-1, R-4, R-6 or R-8 0.2 in all other residential zones 0.1 in all commercial and industrial zones trees 5.List the number of 6” in diameter, or alder or cottonwood trees over 8” in diameter that you are proposing5 to retain4:trees 6.Subtract line 5 from line 4 for trees to be replaced: (if line 6 is zero or less, stop here. No replacement trees are required) trees 7.Multiply line 6 by 12” for number of required replacement inches:inches 8.Proposed size of trees to meet additional planting requirement: (Minimum 2” caliper trees required for replacement, otherwise enter 0)inches per tree 9.Divide line 7 by line 8 for number of replacement trees 6: (If remainder is .5 or greater, round up to the next whole number) trees 1 Measured at 4.5’ above grade. 2 A tree certified, in a written report, as dead, terminally diseased, damaged, or otherwise dangerous to persons or property by a licensed landscape architect, or certified arborist, and approved by the City. 3 Critical areas, such as wetlands, streams, floodplains and protected slopes, are defined in RMC 4-3-050. 4 Count only those trees to be retained outside of critical areas and buffers. 5 The City may require modification of the tree retention plan to ensure retention of the maximum number of trees per RMC 4-4-130H7a. 6 When the required number of protected trees cannot be retained, replacement trees, with at least a two-inch (2") caliper or an evergreen at least six feet (6') tall, shall be planted. See RMC 4-4-130.H.1.e.(ii) for prohibited types of replacement trees. 1 H:\CED\Data\Forms-Templates\Self-Help Handouts\Planning\Tree Retention Worksheet.docx 08/2015 Exhibit 13 Minimum Tree Density A minimum tree density shall be maintained on each residentially zoned lot (exempting single-family dwellings in R-10 and R-14). The tree density may consist of existing trees, replacement trees, or a combination. Detached single-family development 7: Two (2) significant trees 8 for every five thousand (5,000) sq. ft. of lot area. For example, a lot with 9,600 square feet and a detached single-family house is required to have four (4) significant trees or their equivalent in caliper inches (one or more trees with a combined diameter of 24”). This is determined with the following formula: Multi-family development (attached dwellings): Four (4) significant trees8 for every five thousand (5,000) sq. ft. of lot area. Example Tree Density Table: Lot Lot size Min significant trees required New Trees Retained Trees Compliant 1 5,000 2 2 @ 2” caliper 0 Yes 2 10,000 4 0 1 tree (24 caliper inches) Yes 3 15,000 6 2 @ 2” caliper 1 Maple – 15 caliper inches 1 Fir – 9 caliper inches. Yes 7 Lots developed with detached dwellings in the R-10 and R-14 zoned are exempt from maintaining a minimum number of significant trees onsite, however they are not exempt from the annual tree removal limits. 8 Or the gross equivalent of caliper inches provided by one (1) or more trees. 2 H:\CED\Data\Forms-Templates\Self-Help Handouts\Planning\Tree Retention Worksheet.docx 08/2015 March 28, 2017 Jamie Waltier Harbour Homes 400 North 34th Street, Suite 300 Seattle, WA 98103 RE: Critical Areas Study – “Cedars at the Highlands” Parcel #45750- 0106 City of Renton, Washington SWC Job#16-152 1.0 INTRODUCTION This report describes our observations jurisdictional wetlands on or within 100’ of the 4.50 acre property known as “Cedars at the Highlands” (Parcel #145750-0110), located off 160th Avenue SE, in the City of Renton, Washington (the “site”). Above: Vicinity Map Sewall Wetland Consulting, Inc. PO Box 880 Phone: 253-859-0515 Fall City, WA 98024 Harbour – Madison/#16-152 Sewall Wetland Consulting, Inc. March 28, 2017 Page 2 The site, located in the SE quarter of Section 14, Township 23 North, Range 5 East of the W.M., includes a forested area disturbed by past use as a dirt bike track and storage area under the tree canopy, as well as a large shop building with associated gravel driveway and parking areas. The area is abutted by single family parcels to the north and south, and a new road being constructed along the east. The west side of the site abuts 160th Avenue SE. 2.0 METHODOLOGY Ed Sewall of Sewall Wetland Consulting, Inc. inspected the site in March of 2016. The site was reviewed using methodology described in the Washington State Wetlands Identification Manual (WADOE, March 1997). This is the methodology currently recognized by the City of Renton and the State of Washington for wetland determinations and delineations. The site was also reviewed using the methodology described in the Corps of Engineers Wetlands Delineation Manual (Environmental Laboratory, 1987), and the Western Mountains, Valleys and Coast region Supplement (Version 2.0 ) dated June 24, 2010, as required by the US Army Corps of Engineers. Soil colors were ident ified using the 1990 Edited and Revised Edition of the Munsell Soil Color Charts (Kollmorgen Instruments Corp. 1990). The Washington State Wetlands Identification and Delineation Manual and the Corps of Engineers Wetlands Delineation Manual both requires the use of the three-parameter approach in identifying and delineating wetlands. A wetland should support a predominance of hydrophytic vegetation, have hydric soils and display wetland hydrology. To be considered hydrophytic vegetation, over 50% of the dominant species in an area must have an indicator status of facultative (FAC), facultative wetland (FACW), or obligate wetland (OBL), according to the National List of Plant Species That Occur in Wetlands: Northwest (Region 9) (Reed, 1988). A hydric soil is "a soil that is saturated, flooded, or ponded long enough during the growing season to develop anaerobic conditions in the upper part". Anaerobic conditions are indicated in the field by soils with low chromas (2 or less), as determined by using the Munsell Soil Color Charts; iron oxide mottles; hydrogen sulfide odor and other indicators. Generally, wetland hydrology is defined by inundation or saturation to Harbour – Madison/#16-152 Sewall Wetland Consulting, Inc. March 28, 2017 Page 3 the surface for a consecutive period of 12.5% or greater of the growing season. Areas that contain indicators of wetland hydrology between 5%- 12.5% of the growing season may or may not be wetlands depending upon other indicators. Field indicators include visual observation of soil inundation, saturation, oxidized rhizospheres, water marks on trees or other fixed objects, drift lines, etc. Under normal circumstances, indicators of all three parameters will be present in wetland areas. 3.0 OBSERVATIONS 3.1 Existing Site Documentation Prior to visiting the site a review of several natural resourc e inventory maps was conducted. Resources reviewed included the NRCS Soils Survey, the National Wetlands Inventory, and the WDNR Fpars Water Typing Maps. 3.1.1 NRCS Online Soil Mapper Soil Survey The site is mapped as containing Alderwood gravelly sandy loam (Map unit AgC). Alderwood soils are not considered "hydric" or wetland soils according to the publication Hydric Soils of the United States (USDA NTCHS Pub No.1491, 1991). Above: NRCS Soil map of the site. Harbour – Madison/#16-152 Sewall Wetland Consulting, Inc. March 28, 2017 Page 4 3.1.2 National Wetlands Inventory According to the National Wetlands Inventory for the site, there are no wetlands on or near the site. National Wetlands Inventory map 3.1.3 WDFW Priority Habitats A review of the WDFW Priority Habitat map covering the site revealed no priority habitats or species within 1,000’ of the site. Above: WDFW Priority Habitat Map of the site. Harbour – Madison/#16-152 Sewall Wetland Consulting, Inc. March 28, 2017 Page 5 3.1.4 WDNR Fpars Water Type Mapping According to the WDNR Water Type Map for the site, there are no mapped streams or waters on the site. Above: WDNR Fpars Water Type Map 3.1.5 City of Renton Stream Map The City of Renton Stream map has no streams mapped on or near the site. The closest streams are several Class 4 streams mapped approximately 4,000’ east of the site. Above: City of Renton Stream Map Harbour – Madison/#16-152 Sewall Wetland Consulting, Inc. March 28, 2017 Page 6 3.1.6 Mindys Place Wetland Study Sewall wetland Consulting conducted a study of the parcel immediately to the north of the site referred to as Mindy’s Place. This site was found to what at the time under old Code was classified as a Class 4 water with an associated 35’ buffer. This stream exited the Mindy’s Place site at its southeast corner and continued onto the site. 3.2 Field Observations 3.2.1 Uplands As previously described, the site contains a gravel driveway accessing a large shop building on the site. There is also a small outbuilding east of the site, as well as large gravel parking areas, as well as scattered vehicles. The western portion of the site contains an open canopy forested area with 20-30 year old cottonwood trees with a sparse to bare understory. Scattered patches of Himalayan blackberry, indian plum, hazelnut, vine maple and stinging nettle are also present throughout the site. This area has been significantly disturbed in the past and most soil pits excavated within this area revealed a mix of fill and natural soils mixed. The drainage ditch along the east side of 160th drains through a culvert passing through the site to the east. Soil pits excavated in the upland areas revealed disturbed gravelly loam as well as a high chroma, dry gravelly loam soil. 3.2.2 Wetlands No areas meeting wetland criteria were found on the site. 3.2.3 Waters As previously stated, a small ephemeral stream channel passes through the northeast corner of the site. The ordinary high water mark of this stream was flagged with white and blue flagging labeled OHWMW1-W6. As defined in RMC 4.50.G7.a, this stream best meets the criteria of a Type Ns water due to its intermittent flow and lack of fish use. Harbour – Madison/#16-152 Sewall Wetland Consulting, Inc. March 28, 2017 Page 7 Per Renton Code section 4.50.G.2, Type Ns streams have a 50’ buffer measured from the OHWM as well as a 15’ BSBL measured from the edge of the buffer to any structure. 4.0 Proposed Project The proposed project is the construction of a 14 lot plat with associated infrastructure. No impacts to the Type Ns stream or its buffer are proposed. If you have any questions regarding this report, please call us at (253) 859-0515 or at esewall@sewallwc.com . Sincerely, Sewall Wetland Consulting, Inc. Ed Sewall Senior Wetlands Ecologist PWS #212 REFERENCES Cowardin, L., V. Carter, F. Golet, and E. LaRoe. 1979. Classification of Wetlands and Deepwater Habitats of the United States. U.S. Fish and Wildlife Service, FWS/OBS-79-31, Washington, D. C. Daubenmire, R. 1959. A canopy-coverage method of vegetational analysis. Northwest Science 33:43-64. Diers, R. and J.L. Anderson. 1984. Development of Soil Mottling. Soil Survey Horizons, Winter 1984, pg 9-15. Environmental Laboratory. 1987. Corps of Engineers Wetlands Delineation Manual, Technical Report Y-87-1. U. S. Army Corps of Engineers Waterways Experiment Station, Vicksburg, Mississippi. Hitchcock, C. and A. Cronquist. 1976. Flora of the Pacific Northwest. University of Washington Press, Seattle, Washington. Munsell Color. 1988. Munsell Soil Color Charts. Kollmorgen Instruments Corp., Baltimore, Maryland. National Technical Committee for Hydric Soils. 1991. Hydric Soils of the United States. USDA Misc. Publ. No. 1491. Reed, P., Jr. 1988. National List of Plant Species that Occur in Wetlands: Northwest (Region 9). 1988. U. S. Fish and Wildlife Service, Inland Freshwater Ecology Section, St. Petersburg, Florida. Reed, P.B. Jr. 1993. 1993 Supplement to the list of plant species that occur in wetlands: Northwest (Region 9). USFWS supplement to Biol. Rpt. 88(26.9) May 1988. CEDARS AT THE HIGHLANDS14120 160TH AVENUE SERENTON, WASHINGTON 98059CEDARS AT THE HIGHLANDS CEDARS AT THE HIGHLANDS AAANNNNNNN LUA:U:DRS PROJECT NO. 16041A-NNNNNNNNS ERISSEFORPINGOERDETSREENG I NELA53232 OI ET A T H SOY SFOTGNIHASWIDEIPL.OCILAZPRELIMINARY PLAT0GRAPHIC SCALE20'40'80'1 INCH = 40 FT. PfojectfStte: Applicant/Owner: Investigators): WETLAND DETERMINATION DATA FORM — Western Mountains, Valleys, and Coast Region fNA«J.)'s<^- 75^SM.i/< City/County: ~F-UJ'h>-J Sampling Date: *3—^ State; U/A Sampling Point: «P P Landform (hilfslope, terrace, etc.):. Subregion (LRR): Soil Map Unit Name: Lat:. Section, Township, Range; , Local relief (concave, convex, none);. . Long: NWI classificatipn: . _ Slope (%):. Datum: No (If no, explain in Remarks.) No Are climatic / bydrologic conditions on the site typical for this time of year? Yes Are Vegetation , Soil or Hydrology. , significantly disturbed? Are 'Normal Circumstances" present? Yes. _ Are Vegetation , Soil , or Hydrology. naturally problematic? (If needed, explain any answers in Remarks.) SUMMARY OF FINDINGS - Attach site map showing sampling point locations, transects, important features, etc. HvdrophyircVegefatteh Present? Yes. No / HvdrieSoil Presents Yes:. No . '.A Is the Sampled Area / within aWetJand? Yes No .'\i\fetoH-M^at69V;)^es^rSr?' Yes No P.emarks: VEGETATION - Use scientific names of plants, Absolute Dominant Indicator Tree Stratum (Plot size: ) % Cover Species? Status Dominance Test worksheet: Number of Dominant Species / That Are OBL. FACW. or FAC: ' (A) Dominance Test worksheet: Number of Dominant Species / That Are OBL. FACW. or FAC: ' (A) 2, Total Number of Dominant Species Across All Strata: ~-) (B) 3. Total Number of Dominant Species Across All Strata: ~-) (B) 4. Percent of Dominant Species -s, That Are OBL. FACW. or FAC: •> 5 fA/B) - Total Cover Percent of Dominant Species -s, That Are OBL. FACW. or FAC: •> 5 fA/B) Saplirw/Shrub Stratum (Plot size: ) Prevalence Index worksheet: Total % Cover of: Multiply bv: Prevalence Index worksheet: Total % Cover of: Multiply bv: 3. OBL. species X i^ 4. FACW species X2 = 5. FAC species x 3 = =Total Cover FACU species. x 4 = Herb Stratum (Plot size: 1 UPLsoedes x5 = 1. Column Totals: (A) (B) 2. Prevalence index = B/A = 3. Prevalence index = B/A = 4. Hydrophytic Vegetation indicators; , ; Dominance Test is >50% , Prevalence Index ts =S3.01 Morphological Adaptations1 (Provide supporting data in Remarks or on a separate sheet) Wetland Non-Vascular Plants1 Problematic Hydrophytic Vegetation1 (Explain) ^Indicators of hydric soil and v/etland hydrology must be present, unless disturbed or problematic. 5. Hydrophytic Vegetation indicators; , ; Dominance Test is >50% , Prevalence Index ts =S3.01 Morphological Adaptations1 (Provide supporting data in Remarks or on a separate sheet) Wetland Non-Vascular Plants1 Problematic Hydrophytic Vegetation1 (Explain) ^Indicators of hydric soil and v/etland hydrology must be present, unless disturbed or problematic. 6. Hydrophytic Vegetation indicators; , ; Dominance Test is >50% , Prevalence Index ts =S3.01 Morphological Adaptations1 (Provide supporting data in Remarks or on a separate sheet) Wetland Non-Vascular Plants1 Problematic Hydrophytic Vegetation1 (Explain) ^Indicators of hydric soil and v/etland hydrology must be present, unless disturbed or problematic. 7. Hydrophytic Vegetation indicators; , ; Dominance Test is >50% , Prevalence Index ts =S3.01 Morphological Adaptations1 (Provide supporting data in Remarks or on a separate sheet) Wetland Non-Vascular Plants1 Problematic Hydrophytic Vegetation1 (Explain) ^Indicators of hydric soil and v/etland hydrology must be present, unless disturbed or problematic. 8. Hydrophytic Vegetation indicators; , ; Dominance Test is >50% , Prevalence Index ts =S3.01 Morphological Adaptations1 (Provide supporting data in Remarks or on a separate sheet) Wetland Non-Vascular Plants1 Problematic Hydrophytic Vegetation1 (Explain) ^Indicators of hydric soil and v/etland hydrology must be present, unless disturbed or problematic. 9. Hydrophytic Vegetation indicators; , ; Dominance Test is >50% , Prevalence Index ts =S3.01 Morphological Adaptations1 (Provide supporting data in Remarks or on a separate sheet) Wetland Non-Vascular Plants1 Problematic Hydrophytic Vegetation1 (Explain) ^Indicators of hydric soil and v/etland hydrology must be present, unless disturbed or problematic. 10. Hydrophytic Vegetation indicators; , ; Dominance Test is >50% , Prevalence Index ts =S3.01 Morphological Adaptations1 (Provide supporting data in Remarks or on a separate sheet) Wetland Non-Vascular Plants1 Problematic Hydrophytic Vegetation1 (Explain) ^Indicators of hydric soil and v/etland hydrology must be present, unless disturbed or problematic. 11. Hydrophytic Vegetation indicators; , ; Dominance Test is >50% , Prevalence Index ts =S3.01 Morphological Adaptations1 (Provide supporting data in Remarks or on a separate sheet) Wetland Non-Vascular Plants1 Problematic Hydrophytic Vegetation1 (Explain) ^Indicators of hydric soil and v/etland hydrology must be present, unless disturbed or problematic. Hydrophytic Vegetation indicators; , ; Dominance Test is >50% , Prevalence Index ts =S3.01 Morphological Adaptations1 (Provide supporting data in Remarks or on a separate sheet) Wetland Non-Vascular Plants1 Problematic Hydrophytic Vegetation1 (Explain) ^Indicators of hydric soil and v/etland hydrology must be present, unless disturbed or problematic. — Total Cover Woodv Vine Stratum (Plot size: ) Hydrophytic Vegetation 1. .... Hydrophytic Vegetation 2. Hydrophytic Vegetation •= Totai Cover % Bare Ground in Herb Stratum Present? Yes No Remarks: " fa ^ fc^c^ej ^^el^sA^ US Army Corps of Engineers Western Mountains, Valleys, and Coast - Interim Version SOIL Sampling Point, Profile Description: (Describe to trie depth needed to document the Indicator or confirm the absence of indicators.) Depth . Matrix Redox Features finches) Color (moist) Color (rooisfl Type1 to? . Texture Remarks 'Type: C=Concentration, D=Depietion, RW-Reduced Matrix. CS=Covefed or Coated Sand Grains. 'Location: PL=Pore Lining. M=Matrix. Hydric Soil indicators: (Applicable t&ali LRRs, unless otherwise noted.) Histcsol(A1) . Histlc Epipedon (A2) Black Hisfic (A3) Hydiogen Sulfide (A4) Depleted Below Dark Surface (All) , Thick Dark Surface (A12). , Sandy Mucky Mineral (S1) Sandy Gleyed Matrix (S4) Sandy Redox (S5) Stripped Matrix (S6) Loamy Mucky Mineral (F1) (except MLRA1) Loamy Gleyed Matrix (F2) Depleted Matrix (F3) _ , Redox Dark Surface (F6) Depleted Dark Surface (F7) Redox Depressions (F8) indicators for Problematic Hydric Soils': 2cmMuok(A10) , Red Parent Materia} (TF2) Other (Expiate in Remarks) 'indicators of hydrophytic vegetation arid wetland hydrology must be present, unless disturbed or problematic. Restrictive Layer (if present): Type: , Depth (inches):. Hydric Soil Present? Yes. Ho Remarks: HYDROLOGY Wetland Hydrology Indicators: Primary Indicators (minimum of one required: check all that apply),. Surface Water (Ai) , High Water Table (A2) Saturation (A3) Water Marks (B1) Sediment Deposits (B2) : Drift Deposits (B3) Algal Mat or Crust (84) , Iron Deposits (B5) Surface Soil Cracks (B6) Inundation Visible on Aerial Imagery (B7) , Sparsely Vegetated Concave Surface (B8) Water-Stained Leaves (B9) (except MLRA 1, 2, 4A, and 4B) Salt Crust (B11) Aquatic Invertebrates (B13) Hydrogen Sulfide Odor (C1) Oxidized Rhtzospheres along Living Roots (C3) Presence of Reduced Iron (C4) Recent Iron Reduction in Tilled Soils (C6) Stunted or Stressed Plants (01) (LRR A) Other (Explain in Remarks) Secondary Indicators (2 or more required) _ Water-Stained Leaves (B9) (MLRA 1, 2, 4A, and 4B) . Drainage Patterns (B10) Dry-Season Water Table (C2) . Saturation Visible on Aerial Imagery. (C9) Geomorphic Position (D2) __ Shallow Aquiiard (D3) FAC-NeutraITest(05) , Raised Ant Mounds (D6) (LRR A) , Frost-Heave Hummocks (D7) Field Observations: Surface Water Present? Yes L Water Table Present? Yes. Saturation Present? Yes _ (includes capillary fringe) /bvo% (inches): No, No ' ydeptli (inches):. No A Depth (inches):. Wetland Hydrology Present? Yes. No Describe Recorded Data (stream gauge, monitoring well, aerial photos, previous inspections), if'available: Remarks: US Army Corps of Engineers Western Mountains, Valleys, and Coast — Interim Version WETtAMO DETERMINATION DATA FORM - Western Mountains* Valleys, and Coast Region Protect/Site: /M-^l'S«~ lZc%tAiS{ City/County: "Rw"f&~> Sampttno Date: "8^^"^^ _____ State: U'A Sampling Point: j> P^L- Ax AppBcani/Owner:„ investigators}: __ Lancfform (hSslope, terrace, etP.);. Subreotortfj-RR}:. tat: Section, Township, Range: , Local refef (concave, convex, none): Long:_ _ Siope (%}:. Datum; Soft Map Unit Name: NWl classification: Are ctimafJc / hydrotogie conditions on the site typical for this time of year? Yes Are Vegetation Soil, _ or Hydrology. signiftcanfly disturbed? Are Vegetation _____ Soil , or Hydrology naturaily problematic? No (if no. explain in Remarks.) Are'NormalCircumstances*present? Yes. (if needed, expiate any answers in Remarks,) SUMMARY OF FINDINGS - Attach site map^showing sampling point locations, transects, important features^ etc. Hydrophytic Vegetation Present? Hydric Soif Present? Yes. Wetland Hydrology Present? Yes. No. No is the Sarapfed Area within a Wetland? Yes No. Remarks: VEGETATION - Use scientific names of plants. Absolute Dominant indicator Tree Stratum (Plot size: ) % Cover Species? State Dominance Test worksheet: Number of Dominant Species , That Are OBL. FACW. or FAC: 1 (A) Dominance Test worksheet: Number of Dominant Species , That Are OBL. FACW. or FAC: 1 (A) 2. Totai Number of Dominant / Species Across AH Strata: ' (B) 3. Totai Number of Dominant / Species Across AH Strata: ' (B) 4. Percent of Dominant Specfes That Are OBL. FACW. or FAC: / o L> (Am ~ Total Cover Percent of Dominant Specfes That Are OBL. FACW. or FAC: / o L> (Am SaDimo/Shrub Stratum {Plotsfee: ) 1. Prevalence Index worksheet: Totat % Cover of: MuMpfybv: 2. ... Prevalence Index worksheet: Totat % Cover of: MuMpfybv: 3. OBL soecies x 1 = 4. FACW species x2 = 5. FAC soecies X 3 =• = Total Cover FACU soecies x4 = Herb Stratum (Piotsize: "> UPL soectes x 5 a 1. Column Totals: (AV (B) 2. Prevalence index = B/A = 3. . Prevalence index = B/A = 4. HydropHytte vegetation Indicators: c,eorrtinartceTest is>S0% Prevalence Index is sS.O* Mwpftoiogtcal Adaptations1 (Provide supporting data in Remarks or on a separate sheet) Wetland Non-Vascular Plants' Probiemalic Hydrophytic Vegetation' (Explain) ''indicators of hydric soH and wetiand hydrology must be present, unless disturbed or probleraaie. 5. HydropHytte vegetation Indicators: c,eorrtinartceTest is>S0% Prevalence Index is sS.O* Mwpftoiogtcal Adaptations1 (Provide supporting data in Remarks or on a separate sheet) Wetland Non-Vascular Plants' Probiemalic Hydrophytic Vegetation' (Explain) ''indicators of hydric soH and wetiand hydrology must be present, unless disturbed or probleraaie. 6. HydropHytte vegetation Indicators: c,eorrtinartceTest is>S0% Prevalence Index is sS.O* Mwpftoiogtcal Adaptations1 (Provide supporting data in Remarks or on a separate sheet) Wetland Non-Vascular Plants' Probiemalic Hydrophytic Vegetation' (Explain) ''indicators of hydric soH and wetiand hydrology must be present, unless disturbed or probleraaie. 7. HydropHytte vegetation Indicators: c,eorrtinartceTest is>S0% Prevalence Index is sS.O* Mwpftoiogtcal Adaptations1 (Provide supporting data in Remarks or on a separate sheet) Wetland Non-Vascular Plants' Probiemalic Hydrophytic Vegetation' (Explain) ''indicators of hydric soH and wetiand hydrology must be present, unless disturbed or probleraaie. 8. HydropHytte vegetation Indicators: c,eorrtinartceTest is>S0% Prevalence Index is sS.O* Mwpftoiogtcal Adaptations1 (Provide supporting data in Remarks or on a separate sheet) Wetland Non-Vascular Plants' Probiemalic Hydrophytic Vegetation' (Explain) ''indicators of hydric soH and wetiand hydrology must be present, unless disturbed or probleraaie. 9. HydropHytte vegetation Indicators: c,eorrtinartceTest is>S0% Prevalence Index is sS.O* Mwpftoiogtcal Adaptations1 (Provide supporting data in Remarks or on a separate sheet) Wetland Non-Vascular Plants' Probiemalic Hydrophytic Vegetation' (Explain) ''indicators of hydric soH and wetiand hydrology must be present, unless disturbed or probleraaie. 10. HydropHytte vegetation Indicators: c,eorrtinartceTest is>S0% Prevalence Index is sS.O* Mwpftoiogtcal Adaptations1 (Provide supporting data in Remarks or on a separate sheet) Wetland Non-Vascular Plants' Probiemalic Hydrophytic Vegetation' (Explain) ''indicators of hydric soH and wetiand hydrology must be present, unless disturbed or probleraaie. 11. HydropHytte vegetation Indicators: c,eorrtinartceTest is>S0% Prevalence Index is sS.O* Mwpftoiogtcal Adaptations1 (Provide supporting data in Remarks or on a separate sheet) Wetland Non-Vascular Plants' Probiemalic Hydrophytic Vegetation' (Explain) ''indicators of hydric soH and wetiand hydrology must be present, unless disturbed or probleraaie. HydropHytte vegetation Indicators: c,eorrtinartceTest is>S0% Prevalence Index is sS.O* Mwpftoiogtcal Adaptations1 (Provide supporting data in Remarks or on a separate sheet) Wetland Non-Vascular Plants' Probiemalic Hydrophytic Vegetation' (Explain) ''indicators of hydric soH and wetiand hydrology must be present, unless disturbed or probleraaie. = Totat Cover Woodv Vine Stratum (Piotsize: \ Hydrophytic / Vegetation 1. Hydrophytic / Vegetation 2. Hydrophytic / Vegetation -TotafCover % Bare Ground in Herb Stratum Present? Yes _ No Remarks* US Army Corps of Engineers Western Mountains, Vatteys, and Coast - interim Versfoh SOIL Sampling Point. Profile Description: {Describe to the depth needed to document the indicator or confirm the absence of indicators.} Depth , Matrix : Redox Features (inches) Color (moist) % Color (moist) % '. type1 toca \ Texture Remarks Mc 3 fa ^Type: OConcerttration. 0=Oeptetipn. RM^Rediiced Matrix, (^-Covered or Coated Sand Grains, ^Location: PL=Pore Lining, ^gMatrix. Indicators for Problematic HydWe Soils'; 2cmMuck(AtO) Red Parent Materia! (TF2) , Other (Explain in Remarks) 'indicators of hydrophytic vegetation and wetland hydrology must be present, unless disturbed or problematic. Hydric SoH Indicators: (Applicable to at! LRRs, unless otherwise noted.) Histoso!(A1) . Histte Epipedon (A2) Black Histic (A3) . Hydrogen Suffide (A4) Oepteted Bejow Dark Surface (A11) Thick Dark Surface (At 2) Sandy Mucky Mineral (S1) Sandy Gleyed Matrix (S4) Sandy Redox (S5) Stripped Matrix {56) Loamy Mucky Mineral (F1) (except MLRA t) Loamy Gleyed Matrix (F2) Depleted Matrix <F3) .. Redox Dark Surface (F6) , Depleted Dark Surface (F7) Redox Depressions (F8) Restrictive Layer (If presstti): Type:, , Oeoth finches); Hydrie Soil Present? Yes No Remarks: HYDROLOGY Wetland HydroJooy Indicators: Primary lndicatctfs,(rntnirnum of one required: check all fflat apply), Surface Water (A1) High Water Table (A2) Saturation (A3) Wafer Marks {S1) . Sediment Deposits (B2) Drift Oeposits (B3) „ Algal Mat or Crust (B4) iron Deposits (85) Surface Soft Cracks (B6) Inundation Visible on Aerial Imagery (B7) Sparsely Vegetated Concave Surface (88) Water-Stained Leaves (B9) (except MLRA -f,2,4A,and4B) Saft Crust (B11) Aquatic Invertebrates {B13) Hydrogen Suide Odor (C1) Oxidized Rnlzospheres along Living Roots (C3) Presence of Reduced Iron (C4) Recent Iron Reduction in Tilled Soils (€6) Stunted or Stressed Plants (D1) (LRR A) Other (Explain in Remarks) J- Secondary indicators (2 or more required) Water-Stained Leaves <B9) (MLRA 1, % 4A,and4B) _ Drainage Patterns (B10) Dry-Season Water Table (C2) . Saturation Visible on Aerial Imagery (CS) Geomofphic Position(D2) __ Shallow Aq«itard(D3) _ FAC-NeutralTest(D5} Raised Ant Mounds (OS) (LRR A) Frost-Heave Hummocks (D7) Field Observations: t/j Surface Water Present? Yes No /Depth (inches): Water Table Present? Yes No /•Depth finches'): Saturafion Present? Yes No Depth (inches): Wettand Hydroloav Present? Yes Mo (includes caplary fringe) Describe Recorded Data (stream gauge, monitoring well, aerial photos, previous inspections), if available: Remarks: US Army Corps of engineers Western Mountains, Valleys, and Coast — Interim Version October 3, 2017 Jamie Waltier Harbour Homes 400 North 34th Street, Suite 300 Seattle, WA 98103 RE: Revised Critical Areas Study – “Cedars at the Highlands” Parcel #45750-0106 City of Renton, Washington SWC Job#16-152 1.0 INTRODUCTION This report describes our observations jurisdictional wetlands on or within 100’ of the 4.50 acre property known as “Cedars at the Highlands” (Parcel #145750-0110), located off 160th Avenue SE, in the City of Renton, Washington (the “site”). Above: Vicinity Map Sewall Wetland Consulting, Inc. PO Box 880 Phone: 253-859-0515 Fall City, WA 98024 Harbour – Madison/#16-152 Sewall Wetland Consulting, Inc. October 3, 2017 Page 2 The site, located in the SE quarter of Section 14, Township 23 North, Range 5 East of the W.M., includes a forested area disturbed by past use as a dirt bike track and storage area under the tree canopy, as well as a large shop building with associated gravel driveway and parking areas. The area is abutted by single family parcels to the no rth and south, and a new road being constructed along the east. The west side of the site abuts 160th Avenue SE. 2.0 METHODOLOGY Ed Sewall of Sewall Wetland Consulting, Inc. inspected the site in March of 2016. The site was reviewed using methodology described in the Washington State Wetlands Identification Manual (WADOE, March 1997). This is the methodology currently recognized by the City of Renton and the State of Washington for wetland determinations and delineations. The site was also reviewed using the methodology described in the Corps of Engineers Wetlands Delineation Manual (Environmental Laboratory, 1987), and the Western Mountains, Valleys and Coast region Supplement (Version 2.0 ) dated June 24, 2010, as required by the US Army Corps of Engineers. Soil colors were identified using the 1990 Edited and Revised Edition of the Munsell Soil Color Charts (Kollmorgen Instruments Corp. 1990). The Washington State Wetlands Identification and Delineation Manual and the Corps of Engineers Wetlands Delineation Manual both requires the use of the three-parameter approach in identifying and delineating wetlands. A wetland should support a predominance of hydrophytic vegetation, have hydric soils and display wetland hydrology. To be considered hydrophytic vegetation, over 50% of the dominant species in an area must have an indicator status of facultative (FAC), facultative wetland (FACW), or obligate wetland (OBL), according to the National List of Plant Species That Occur in Wetlands: Northwest (Region 9) (Reed, 1988). A hydric soil is "a soil that is saturated, flooded, or ponded long enough during the growing season to develop anaerobic conditions in the upper part". Anaerobic conditions are indicated in the field by soils with low chromas (2 or less), as determined by using the Munsell Soil Color Charts; iron oxide mottles; hydrogen sulfide odor and other indicators. Generally, wetland hydrology is defined by inundation or saturation to Harbour – Madison/#16-152 Sewall Wetland Consulting, Inc. October 3, 2017 Page 3 the surface for a consecutive period of 12.5% or greater of the growing season. Areas that contain indicators of wetland hydrology between 5%- 12.5% of the growing season may or may not be wetlands depending upon other indicators. Field indicators include visual observation of soil inundation, saturation, oxidized rhizospheres, water marks on trees or other fixed objects, drift lines, etc. Under normal circumstances, indicators of all three parameters will be present in wetland areas. 3.0 OBSERVATIONS 3.1 Existing Site Documentation Prior to visiting the site a review of several natural resource inventory maps was conducted. Resources reviewed included the NRCS Soils Survey, the National Wetlands Inventory, and the WDNR Fpars Water Typing Maps. 3.1.1 NRCS Online Soil Mapper Soil Survey The site is mapped as containing Alderwood gravelly sandy loam (Map unit AgC). Alderwood soils are not considered "hydric" or wetland soils according to the publication Hydric Soils of the United States (USDA NTCHS Pub No.1491, 1991). Above: NRCS Soil map of the site. Harbour – Madison/#16-152 Sewall Wetland Consulting, Inc. October 3, 2017 Page 4 3.1.2 National Wetlands Inventory According to the National Wetlands Inventory for the site, there are no wetlands on or near the site. National Wetlands Inventory map 3.1.3 WDFW Priority Habitats A review of the WDFW Priority Habitat map covering the site revealed no priority habitats or species within 1,000’ of the site. Above: WDFW Priority Habitat Map of the site. Harbour – Madison/#16-152 Sewall Wetland Consulting, Inc. October 3, 2017 Page 5 3.1.4 WDNR Fpars Water Type Mapping According to the WDNR Water Type Map for the site, there are no mapped streams or waters on the site. Above: WDNR Fpars Water Type Map 3.1.5 City of Renton Stream Map The City of Renton Stream map has no streams mapped on or near the site. The closest streams are several Class 4 streams mapped approximately 4,000’ east of the site. Harbour – Madison/#16-152 Sewall Wetland Consulting, Inc. October 3, 2017 Page 6 Above: City of Renton Stream Map 3.1.6 Mindys Place Wetland Study Sewall wetland Consulting conducted a study of the parcel immediately to the north of the site referred to as Mindy’s Place. This site was found to what at the time under old Code was classified as a Class 4 water with an associated 35’ buffer. This stream exited the Mindy’s Place site at its southeast corner and continued onto the site. The Mindy’s Place site also included a disturbed forested wetland that was classified as a Class 2 wetland with an associated 50’ buffer. 3.2 Field Observations 3.2.1 Uplands As previously described, the site contains a gravel driveway accessing a large shop building on the site. There is also a small outbuilding east of the site, as well as large gravel parking areas, as w ell as scattered vehicles. The western portion of the site contains an open canopy forested area with 20-30 year old cottonwood trees with a sparse to bare understory. Scattered patches of Himalayan blackberry, indian plum, hazelnut, vine maple and stinging nettle are also present throughout the site. This area has been significantly disturbed in the past and most soil pits excavated within this area revealed a mix of fill and natural soils mixed. The drainage ditch along the east side of 160th drains through a culvert passing through the site to the east. Soil pits excavated in the upland areas revealed disturbed gravelly loam as well as a high chroma, dry gravelly loam soil. 3.2.2 Wetlands No areas meeting wetland criteria were found on the site. Off-site Wetlands The Mindy’s Place site to the north contains a disturbed forested wetland that was classified as a Class 2 wetland using the old wetland rating system which was based primarily on the fact the wetland was located near the headwater of a drainage and had minimal disturbance. Harbour – Madison/#16-152 Sewall Wetland Consulting, Inc. October 3, 2017 Page 7 The definition of a Class 2 wetland under the old Code was based mostly on landscape location and general Character. The definition was as follows; ii. Category 2: Category 2 wetlands are wetlands which meet one or more of the following criteria: (a) Wetlands that are not Category 1 or 3 wetlands; and/or (b) Wetlands that have heron rookeries or osprey nests, but are not Category 1 wetlands; and/or (c) Wetlands of any size located at the headwaters of a watercourse, i.e., a wetland with a perennial or seasonal outflow channel, but with no defined influent channel, but are not Category 1 wetlands; and/or (d) Wetlands having minimum existing evidence of human-related physical alteration such as diking, ditching or channelization; and/or Prior to the platting process, the wetland edge was delineated on this site initially to determine the edge of a clearing violation that occurred on the west side of the wetland that occurred prior to 2012. The west side of the wetland had been cleared and graded and the intermittent stream was piped through the site. The restoration included removing the small pipe and regrading of a channel which connects to the channel on the Cedars property. Since no work was to be done or proposed easterly of the wetland and stream edge, the eastern edge of the wetland was only approximated. As part of our review we have refined and depicted accurately where this wetland edge is along the north edge of the Cedars site. We have also re- rated the wetland using the 2014 WADOE Wetland Rating System. Using the function based 2014 Wetland Rating System for Western Washington, and rating the wetland as a depressional wetland, the wetland received a total score of 14 points with 4 points for habitat (see attached rating form). This indicates a Category IV wetland. Based upon the table in RMC 4-3-050 (see page 8), Category IV wetlands have a 50’ buffer as well as a 15’ BSBL for structures. Harbour – Madison/#16-152 Sewall Wetland Consulting, Inc. October 3, 2017 Page 8 3.2.3 Waters As previously stated, a small ephemeral stream channel passes through the northeast corner of the site. The ordinary high water mark of this stream was flagged with white and blue flagging labeled OHWMW1-W6. As defined in RMC 4.50.G7.a, this stream best meets the criteria of a Type Ns water due to its intermittent flow and lack of fish use. Per Renton Code section 4.50.G.2, Type Ns streams have a 50’ buffer measured from the OHWM as well as a 15’ BSBL measured from the edge of the buffer to any structure. Harbour – Madison/#16-152 Sewall Wetland Consulting, Inc. October 3, 2017 Page 9 4.0 Proposed Project The proposed project is the construction of a 14 lot plat with associated infrastructure. No impacts to the Type Ns stream or its buffer are proposed. If you have any questions regarding this report, please call us at (253) 859-0515 or at esewall@sewallwc.com . Sincerely, Sewall Wetland Consulting, Inc. Ed Sewall Senior Wetlands Ecologist PWS #212 REFERENCES Cowardin, L., V. Carter, F. Golet, and E. LaRoe. 1979. Classification of Wetlands and Deepwater Habitats of the United States. U.S. Fish and Wildlife Service, FWS/OBS-79-31, Washington, D. C. Daubenmire, R. 1959. A canopy-coverage method of vegetational analysis. Northwest Science 33:43-64. Diers, R. and J.L. Anderson. 1984. Development of Soil Mottling. Soil Survey Horizons, Winter 1984, pg 9-15. Environmental Laboratory. 1987. Corps of Engineers Wetlands Delineation Manual, Technical Report Y-87-1. U. S. Army Corps of Engineers Waterways Experiment Station, Vicksburg, Mississippi. Hitchcock, C. and A. Cronquist. 1976. Flora of the Pacific Northwest. University of Washington Press, Seattle, Washington. Munsell Color. 1988. Munsell Soil Color Charts. Kollmorgen Instruments Corp., Baltimore, Maryland. National Technical Committee for Hydric Soils. 1991. Hydric Soils of the United States. USDA Misc. Publ. No. 1491. Reed, P., Jr. 1988. National List of Plant Species that Occur in Wetlands: Northwest (Region 9). 1988. U. S. Fish and Wildlife Service, Inland Freshwater Ecology Section, St. Petersburg, Florida. Reed, P.B. Jr. 1993. 1993 Supplement to the list of plant species that occur in wetlands: Northwest (Region 9). USFWS supplement to Biol. Rpt. 88(26.9) May 1988. CEDARS AT THE HIGHLANDS14120 160TH AVENUE SERENTON, WASHINGTON 98059CEDARS AT THE HIGHLANDS CEDARS AT THE HIGHLANDS AAANNNNNNN LUA17-000189 U:DRS PROJECT NO. 16041A-NNNNNNNNS ERISSEFORPINGOERDETSREENG I NELA53232 OI ET A T H SOY SFOTGNIHASWIDEIPL.OCILAZPRELIMINARY PLAT0GRAPHIC SCALE20'40'80'1 INCH = 40 FT. Wetland name or number RATING SUMMARY - Western Washington Name of wetland (or ID It): UJttf~i) A" Date of site visit: C?-/^( 7 Rated by <=^(. ^c*t~»-ti Trained by Ecology? "''Yes No Date of training HGM Class used for rating ^><"j>r*+i 1 Wetland has multiple HGM classes? Y N NOTE: Form is not complete without the figures requested (figures can be combined). Source of base anrial photo/map OVERALL WETLAND CATEGORY 4^f(based on functions or special characteristics ) 1. Category of wetland based on FUNCTIONS Category I -Total score = 23-27 _Category II - Total score =20-22 Category III - Total score =16-19 _Category IV - Total score = 9-15 \S Ca FUNCTION Improving Water Quality Hydrologk Habitat Circle the appropriate ratings Site Potential H M (£> H M 0> H M Q Landscape Potential H <&> L fry L H M TP Value H M iy H L H ^) L TOTAL Score Based on Ratings H 6 i 2. Category based on SPECIAL CHARACTERISTICS of wetland Score for each function based on three ratings (order of ratings is not important) 9 = H,H,H 8 = H,H,M H,H,L H,M,M H,M,L M,M,M H,L,L M,M,L M,L,L L,L,L CHARACTERISTIC CATEGORY Estuarlne 1 II Wetland of High Conservation Value 1 Bog 1 Mature Forest 1 Old Growth Forest 1 Coastal Lagoon 1 II Interdunal 1 II III/Kf None of the above Wetland Rating System for Western WA: 2014 Update Rating Form - Effective January 1,2015 1 Wetland name or number Maps and figures required to answer questions correctly for Western Washington Depressions! Wetlands Map of: • To answer questions: Figure* • Cowardin plant classes D 1.3, H 1.1, H 1.4 Hydroperiods D 1.4, H 1.2 Location of outlet [can be added to map of hydroperiods} D 1.1, D 4.1 Boundary of area within 150 ft of the wetland (can be added to another figure) D 2.2, D 5.2 Map of the contributing basin D 4.3, D 5.3 1 km Polygon: Area that extends 1 km from entire wetland edge - including H 2.1. H 2.2. H 2.3 polygons tor accessible naDitat ana undisturbed nabitat Screen capture of map of 303(d) listed waters in basin (from Ecology website) D 3.1, D 3.2 Screen capture of list of TMDLs for WRIA in which unit is found (from web) D3.3 Riverine Wetlands ManoT: To answer questions: figure* Cowardin plant classes H 1.1, H 1.4 Hydroperiods H1.2 Ponded depressions Rl.l Boundary of area within 150 ft of the wetland (can be added to another figure) R2.4 Plant cover of trees, shrubs, and herbaceous plants R 1.2, R 4.2 Width of unit vs. width of stream (can be added to another figure) R4.1 Map of the contributing basin R 2.2, R 2.3, R 5.2 1 km Polygon: Area that extends 1 km from entire wetland edge - including polygons for accessible habitat and undisturbed habitat H 2.1, H 2.2, H 2.3 Screen capture of map of 303(d) listed waters in basin (from Ecology website) R3.1 Screen capture of list of TMDLs for WRIA in which unit is found (from web) R 3.2, R 3.3 Lake Fringe Wetlands meek -.. To answer questions: Figure* Cowardin plant classes Ll.l, L 4.1, H 1.1, H 1.4 Plant cover of trees, shrubs, and herbaceous plants L1.2 Boundary of area within 150 ft of the wetland (con be added to another figure) L2.2 1 km Polygon: Area that extends 1 km from entire wetland edge - including polygons for accessible habitat and undisturbed habitat H 2.1, H 2.2, H 2.3 Screen capture of map of 303(d) listed waters in basin (from Ecology website) L 3.1, L 3.2 Screen capture of list of TMDLs for WRIA in which unit is found (from web) L3.3 Slooe Wetlands Map of: To answer questions: Figure* Cowardin plant classes H 1.1, H 1.4 Hydroperiods H1.2 Plant cover of dense trees, shrubs, and herbaceous plants S 1.3 Plant cover of dense, rigid trees, shrubs, and herbaceous plants icon be added to figure above) S4.1 Boundary of 150 ft buffer (can be added to another figure) S 2.1, S 5.1 1 km Polygon: Area that extends 1 km from entire wetland edge - including polygons for accessible habitat and undisturbed habitat H 2.1, H 2.2, H 2.3 Screen capture of map of 303(d) listed waters in basin (from Ecology website) S 3.1, S 3.2 Screen capture of list of TMDLs for WRIA in which unit is found (from web) S3.3 Wedand Rating System for Western WA: 2014 Update Rating Form - Effective January 1,2015 2 Wetland name or number HGM Classification of Wetlands in Western Washington For questions 1-7, the criteria described must apply to the entire unit being rated. If the hydrologic criteria listed in each question do not apply to the entire unit being rated, you probably have a unit with multiple HGM classes. In this case, identify which hydrologic criteria in questions 1-7 apply, and go to Question 8. 1. Are the water levels in the entire unit usually controlled by tides except during floods? (^N0^jotc£2 ' YES - the wetland class is Tidal Fringe - go to 1.1 1.1 Is the salinity of the water during periods of annual low flow below 0.5 ppt (parts per thousand)? NO - Saltwater Tidal Fringe (Estuarine) YES - Freshwater Tidal Fringe If your wetland can be classified as a Freshwater Tidal Fringe use the forms for Riverine wetlands. If it is Saltwater Tidal Fringe it is an Estuarine wetland and is not scored. This method cannot be used to score functions for estuarine wetlands. 2. The entire wetland unit is flat and precipitation is the only source (>90%) of water to it. Groundwater and surface water runoff are NOT sources of water to the unit. YES - The wetland class is Flats \fyourwetland can be classified as a Fiats wetland, use the form for Depressionalwetlands. Does the entire wetland unit meet all of the following criteria? The vegetated part of the wetland is on the shores of a body of permanent open water (without any plants on the surface at any time of the year) at least 20 ac (8 ha) in size; At least 30% of the open water area is deeper than 6.6 ft (2 m). YES - The wetland class is Lake Fringe (Lacustrine Fringe) Does the entire wetland unit meet all of the following criteria? _i/j3»e wetland is on a slope (slope can be very gradual), J_The water flows through the wetland in one direction (unidirectional) and usually comes from seeps. It may flow subsurface, as sheetflow, or in a swale without distinct banks, gter leaves the wetland without being impounded. NO - go toy YES - The wetland class is Slope NOTE: Surface water does not pond in these type of wetlands except occasionally in very small and shallow depressions or behind hummocks (depressions are usually <3 ft diameter and less than 1 ft deep). Does the entire wetland unit meet all of the following criteria? The unit is in a valley, or stream channel, where it gets inundated by overbank flooding from that stream or river, The overbank flooding occurs at least once every 2 years. Wetland Rating System for Western WA: 2014 Update Rating Form - Effective January 1,2015 3 Wetland name or number NQ^gate^ YES - The wetland class is Riverine NOTE: The Riverine unit can contain depressions that are filled with water when the river is not flooding 6. Is the entire wetland unit in a topographic depression in which water ponds, or is saturated to the surface, at some time during the year? This means that any outlet, if present, is higher than the interior of the wetland. NO - go to 7 Is the entire wetland unit located in a very flat area with no obvious depression and no overbank flooding? The unit does not pond surface water more than a few inches. The unit seems to be maintained by high groundwater In the area. The wetland may be ditched, but has no obvious natural-outlet. NO-goto8 YES - The wetland class is Depressional 8. Your wetland unit seems to be difficult to classify and probably contains several different HGM classes. For example, seeps at the base of a slope may grade into a riverine floodplain, or a small stream within a Depressional wetland has a zone of flooding along its sides. GO BACK AND IDENTIFY WHICH OF THE HYDROLOGIC REGIMES DESCRIBED IN QUESTIONS 1-7 APPLY TO DIFFERENT AREAS IN THE UNIT (make a rough sketch to help you decide). Use the following table to identify the appropriate class to use for the rating system if you have several HGM classes present within the wetland unit being scored. NOTE: Use this table only if the class that is recommended in the second column represents 10% or more of the total area of the wetland unit being rated. If the area of the HGM class listed in column 2 is less than 10% of the unit; classify the wetland using the class that represents more than 90% of the total area. HGM classes within the wetland unit being rated HGM class to use in rating Slope + Riverine Riverine Slope + Depressional Depressional Slope + Lake Fringe Lake Fringe Depressional + Riverine along stream within boundary of depression Depressional Depressional + Lake Fringe Depressional Riverine + Lake Fringe Riverine Salt Water Tidal Fringe and any other class of freshwater wetland Treat as ESTUARINE If you are still unable to determine which of the above criteria apply to your wetland, or if you have more than 2 HGM classes within a wetland boundary, classify the wetland as Depressional for the rating. Wetland Rating System for Western WA: 2014 Update Rating Form - Effective January 1,2015 4 Wetland name or number DEPRESSIONAL AND FIATS WETLANDS Hydrologic Functions ~ Indicators that the site functions to reduce flooding and stream degradation D 4.0. Does the site have the potential to reduce flooding and erosion? D 4.1. Characteristics of surface water outflows from the wetland: Wetland is a depression or flat depression with no surface water leaving it (no outlet) points = 4 Wetland has an intermittently flowing stream or ditch, OR highly constricted permanently flowing outletpojsfcj^i ' Wetland is a flat depression (QUESTION 7 on key), whose outlet is a permanently flowing ditch points = 1 Wetland has an unconstricted, or slightly constricted, surface outlet that is permanently flowing points - 0 D 4.2. Depth of storage during wqt periods: Estimate the height of ponding above the bottom of the outlet. For wetlands with no outlet, measure from the surface of permanent water or if dry, the deepest part. Mirk* of ponding are 3 ft or mora «bow tho aurfaoa or bottom of outlet points - 7 = Marks of ponding between 2 ft to < 3 ft from surface or bottom of outlet Marks are at least 0.5 ft to < 2 ft from surface or bottom of outlet The wetland is a "headwater" wetland Wetland is flat but has small depressions on the surface that trap water Marks of ponding less than 0.5 ft (6 in) points = 5 points = 3 points = 3 pointsj=_l^ o D 4.3. Contribution of the wetland to storage in the watershed: Estimate the ratio of the area of upstream basin contributing surface water to the wetland to the area of the wetland unit itself. The area of the basin is less than 10 times the area of the unit points = 5 The area of the basin is 10 to 100 times the area of the unit points ~ 3 The area of the basin is more than 100 times the area of the unit oc[nts^fE--2 Entire wetland is in the Flats class points = 5 Total for D 4 ^ Rating of Site Potential If score is: 12-16 = H 6-11 = M a L Add the points in the boxes above Record the rating on the first page D 5.0. Does the landscape have the potential to support hydrologic functions of the site? D 5.1. Does the wetland receive stormwater discharges? ^Yes^l^JJo = 0 i D 5.2. Is >10% of the area within 150 ft of the wetland in land uses that generate excess runoff? CYes =1^6 ~ 0 D 5.3. Is more than 25% of the contributing basin of the wetland covered with intensive human land uses (residential at >1 residence/ac, urban, commercial, agriculture, etc.)? C"Ves^£ No = 0 l Total for D 5 Add the points in the boxes above Record the rating on the first page D 6.0. Are the hydrologic functions provided by the site valuable to society? D 6.1. The unit is in a landscape that has flooding problems. Choose the description that best matches conditions around the wetland unit being rated. Do not add points. Choose the highest score if more than one condition is met. The wetland captures surface water that would otherwise flow down-gradient into areas where flooding has damaged human or natural resources (e.g., houses or salmon redds): • Flooding occurs in a sub-basin that is immediately down-gradient of unit. points = 2 • Surface flooding problems are in a sub-basin farther down-gradient. points = 1 Flooding from groundwater is an issue in the sub-basin. petrKS = The existing or potential outflow from the wetland is so constrained by human or natural conditions thaTthe water stored by the wetland cannot reach areas that flood. Explain why points = 0 There are no problems with flooding downstream of the wetland. points = 0 D 6.2. Has the site been identified as important for flood storage or flood conveyance in a regional flood controljilan? Yes=2 hfoVqV Total for D 6 Rating of Value If score is: 2-4 = H Add the points in the boxes above i Record the rating on the first page Wetland name or number DEPRESSIONAL AND PUTS WETLANDS Water Quality Functions - indicators that the site functions to improve water quality D 1.0. Does the site have the potential to improve water quality? D 1.1. Characteristics of surface water outflows from the wetland: Wetland is a depression or flat depression (QUESTION 7 on key) with no surface water leaving it (no outlet). points = 3 Wetland has an intermittently flowing stream or ditch, OR highly constricted permanently flowing outlet. Wetland has an unconstricted, or slightly constricted, surface outlet that is permanently flowing points = 1 Wetland is a flat depression (QUESTION 7 on key), whose outlet is a permanently flowing ditch. points = 1 n1 7 yhf top j« *^tom i-he surface for duff laver) is true day or true organic (uit NRCSdifinitianihYei^ 4 Mo==£= D 1.3. Characteristics and distribution pf persistent plants (Emergent, Scrub-shrub, and/or Forested Cowardin classes): Wetland has persistent, ungrazed, plants > 95% of area npintx Wetland has persistent, ungrazed, plants > % of area (points =Jj) Wetland has persistent, ungrazed plants > Vio of area points = 1 Wetland has persistent, ungrazed plants <Vio of area points - 0 D 1.4. Characteristics of seasonal ponding or inundation: This is the area that is ponded for at least 2 months. See description in manual. Area seasonally ponded is > H total area of wetland Area seasonally ponded is > K total area of wetland Area seasonally ponded is < % total area of wetland points = 4 points = 2 Cpoints==j^3 Total for D1 ^ Add the points in the boxes above ^0-5 = L Record the rating on the first page Rating of Site Potential If score is: 12-16 = H 6-11 = M D 2.0. Does the landscape have the potential to support the water quality function of the site? D 2.1. Does the wetland unit receive stormwater discharges? f^Ves = l^Jo = 0 D 2.2. Is > 10% of the area within 150 ft of the wetland in land uses that generate pollutants? (Yes =T^No = 0 D 2.3. Are there septic systems within 250 ft of the wetland? Yes=l No = 0 0 2.4. Are there other sources of pollutants coming into the wetland that are not listed in questions D 2.1-D 2.3? Source Yes - 1 (io = 0^2 €> Total for 0 2 Add the points in the boxes above 2-Rating of Landscape Potential If score is: 3 or 4 = H _0 = L Record the rating on the first page D 3.0. Is the water quality improvement provided by the site valuable to society? D 3.1. Does the wetland discharge directly (i.e., within 1 mi) to a stream, river, lake, or marine water that is on the 303(d) list? Yes=l foc^O^ © D 3.2. Is the wetland in a basin or sub-basin where an aquatic resource is on the 303(d) list? Yes = 1 (TJo = oj? o D 3.3. Has the site been identified in a watershed or local plan as important for maintaining water quality (ansperYES if there is a TMDL for the basin in which the unit is found)? Yes = 2 Ng^jp^ Total for D 3 y Add the points in the boxes above o Rating of Value Ifscoreis: 2-4 = H 1 = M '0 = 1 Record the rating on the first page Wetland Rating System for Western WA: 2014 Update Rating Form - Effective January 1,2015 Wetland Rating System for Western WA: 2014 Update Rating Form - Effective January 1,2015 6 Wetland name or number _ Wetland name or number _ HABITAT FUNCTIONS These questions apply to wetlands of all HGM classes. Indicators that site functions to provide important habitat H 1.0. Does the site have the potential to provide habitat? H 1.1. Structure of plant community: Indicators are Cowardin classes and strata within the Forested class. Check the Cowardin plant classes in the wetland. Up to 10 patches may be combined for each doss to meet the threshold of% oc or more than 10% of the unit if it is smaller than 2.5 ac. Add the number of structures checked. Aquatic bed 4 structures or more: points = 4 __ Emergent 3 structures: points = 2 .Scrub-shrub (areas where shrubs have > 30% cover) 2 structures: point{^£) Crested (areas where trees have > 30% cover) 1 structure: points = 0 —^yfaf u ftii I mi w fWfriw/ dm< Umh if: = _The Forested class has 3 out of 5 strata (canopy, sub-canopy, shrubs, herbaceous, moss/ground-cover) that each cover 20% within the Forested polygon H 1.2. Hydroperiods Check the types of water regimes (hydroperiods) present within the wetland. The water regime has to cover more than 10% of the wetland or % ac to count [see text for descriptions of hydroperiods). , Permanently flooded or inundated 4 or more types present: points = 3 [^Seasonally flooded or inundated 3 types present: points * 2 Occasionally flooded or inundated 2 types present: points Saturated only 1 type present: points = 0 Permanently flowing stream or river in, or adjacent to, the wetland <S Seasonally flowing stream in, or adjacent to, the wetland lake Fringe wetland 2 points Freshwater tidal wetland 2 points H 1.3. Richness of plant species Count the number of plant species in the wetland that cover at least 10 ft2. Different patches of the same species can be combined to meet the size threshold and you do not have to name the species. Do not include Eurasian milfoil, reed canarygrass, purple loosestrife, Canadian thistle If you counted: > 19 species points = 2_ 5 -19 species (^nts^p < 5 species points = 0 H 1.4. interspersion of habitats Decide from the diagrams below whether interspersion among Cowardin plants classes (described in H 1.1), or the classes and unvegetated areas (can include open water or mudflats) is high, moderate, low, or none. If you have four or more plan t classes or three classes and open water, the rating is always high. Low ~ 1 point Moderate = 2 points All three diagrams in this row are HIGH ~ 3points Wetland Rating System for Western WA: 2014 Update Rating Form - Effective January 1,2015 H 1.5. Special habitat features: Check^he habitat features that are present in the wetland. The number of checks is the number of points. ^Large, downed, woody debris within the wetland (> 4 in diameter and 6 ft long). •"Standing snags (dbh > 4 in) within the wetland Undercut banks are present for at least 6.6 ft (2 m) and/or overhanging plants extends at least 3.3 ft (1 m) over a stream (or ditch) in, or contiguous with the wetland, for at least 33 ft (10 m) Stable steep banks of fine material that might be used by beaver or muskrat for denning (> 30 degree slope) OR signs of recent beaver activity are present (cut shrubs or trees that have not yet weathered where wood is exposed) At least % ac of ttiin-stemmed persistent plants or woody branches are present in areas that are permanently or seasonally inundated (structures for egg-laying by amphibians) Invasive plants cover less than 25% of the wetland area in every stratum of plants (see H 1.1 for list of strata) Total for H 1 Add the points in the boxes above Rating of Site Potential If score is: 15-18 = H 7-14 = M ^0-6 = 1 Record the rating on the first page H 2.0. Does the landscape have the potential to support the habitat functions of the site? H 2.1. Accessible habitat (include only habitat that directly abuts wetland unit}. ^ Calculate: %T % undisturbed habitat? « + f{% moderate and low intensitv land uses)/2v'i>= % If total accessible habitat is: >'/, (33.3%) of 1 km Polygon points = 3 20-33% of 1 km Polygon points = 2 10-19%of 1 km Polygon dSiffls=i^-< 10% of 1 km Polygon points = 0 H 2.2. Undisturbed habitat in 1 km Polygon around the wetland. Calculate: /> % undisturbed habitat^* + f(% moderate and low intensity land uses)/21/^ = Z-" % Undisturbed habitat > 50% of Polygon points = 3 Undisturbed habitat 10-50% and in 1-3 patches points = 2 Undisturbed habitat 10-50% and > 3 patches ^--points = 1*) Undisturbed habitat < 10% of 1 km Polygon points = 0 \ H 2.3. Land use intensity in 1 km Polygon: If > 50% of 1 km Polygon is high intensity land use r~ points -|-2^> S 50% of 1 km Polygon is high intensity poffifs^O -z_ Total for H 2 _ Add the points in the boxes above o Rating of Landscape Potential If score is: 4-6 a H 1-3 = M Record the rating on the first page H 3.0. Is the habitat provided by the site valuable to society? H 3.1. Does the site provide habitat for species valued in laws, regulations, or policies? Choose only the highest score that applies to the wetland being rated. Site meets ANY of the following criteria: points = 2 — It has 3 or more priority habitats within 100 m (see next page) — It provides habitat for Threatened or Endangered species (any plant or animal on the state or federal lists) — It is mapped as a location for an individual WDFW priority species — It is a Wetland of High Conservation Value as determined by the Department of Natural Resources — It has been categorized as an important habitat site in a local or regional comprehensive plan, in a Shoreline Master Plan, or in a watershed plan Site has 1 or 2 priority habitats (listed on next page Site does not meet any of the criteriajrfiove Rating of Value If score is: 2 = H eriajrfiov points = 0 Record the rating on the first page Wetland Rating System for Western WA: 2014 Update Rating Form - Effective January 1,2015 Wetland name or number CATEGORIZATION BASED ON SPECIAL CHARACTERISTICS Wetland Type Check off any criteria that apply to the wetland. Circle the category when the appropriate criteria are met SC 1.0. Estuarine wetlands Does the wetland meet the following criteria for Estuarine wetlands? —- The dominant water regime is tidal, — Vegetated, and — With a salinity greater than 0.5 ppt Yes-Go toSCl.l I SC 1.1. is the wetland within a National Wildlife Refuge, National Park, National Estuary Reserve, Natural Area Preserve, State Park or Educational, Environmental, or Scientific Reserve designated under WAC 332-30-151? Category SC 1.2. is the wetland unit at least 1 ac in size and meets at least two of the following three conditions? —The wetland is relatively undisturbed (has no diking, ditching, filling, cultivation, grazing, and has less than 10% cover of non-native plant species. (If non-native species are Spartina, see page 25) —At least % of the landward edge of the wetland has a 100 ft buffer of shrub, forest, or un-grazed orun-mowed grassland. —The wetland has at least two of the following features: tidal channels, depressions with open water, or contiguous freshwater wetlands. Yes = Category I No = Category II SC2.0. Wetlands of High Conservation Value (WHCV) SC 2.1. Has the WA Department of Natural Resources updated their website to include the list of Wetlands of High Conservation Value? Yes - Go to SC 2.2 No - Go to SC 2,3 SC 2.2. is the wetland listed on the WDNR database as a Wetland of High Conservation Value? Yes = Category I SC 2.3. Is the wetland in a Section/Township/Range that contains a Natural Heritage wetland? h.ttp.;//yywwXdnr.wa.go^ Yes - Contact WNHP/WDNR and go to SC 2.4 No = Not a WHCV SC 2.4. Has WDNR identified the wetland within the S/T/R as a Wetland of High Conservation Value and listed it on their website? Yes a Category I No = Not a WHCV SC 3.0. Bogs Does the wetland (or any part of the unit) meet both the criteria for soils and vegetation in bogs? Use the key below. If you answer YES you will still need to rate the wetland based on its functions. SC 3.1. Does an area within the wetland unit have organic soil horizons, either peats or mucks, that compose 16 iruor more of the first 32 in of the soil profile? Yes - Go to SC 3.3 Nfti-Gq foSCA-r SC 3.2. Does an area within the wetland unit have organic soils, either peats or mucks, that are less than 16 in deep over bedrock, or an impermeable hardpan such as clay or volcanic ash, or that are floating on top of pond? Yes - Go to SC 3.3 (^flo^lsnot a b( SC 3.3. Does an area with peats or mucks have more than 70% cover of mosses at ground level, Al cover of plant species listed in Table 4? Yes = Is a Category I bog No - Go to SC 3.4 NOTE: If you are uncertain about the extent of mosses in the understory, you may substitute that criterion by measuring the pH of the water that seeps into a hole dug at least 16 in deep. If the pH is less than 5.0 and the plant species in Table 4 are present, the wetland is a bog. SC 3.4. Is an area with peats or mucks forested (> 30% cover) with Sitka spruce, subalpine fir, western red cedar, western hemlock, lodgepole pine, quaking aspen, Engetmann spruce, or western white pine, AND any of the species (or combination of species) listed in Table 4 provide more than 30% of the cover under the canopy? Yes - Is a Category I bog No = Is not a bog Wetland name or number WDFW Priority Habitats Priority habitats listed hv WDFW (see complete descriptions of WDFW priority habitats, and the counties in which they can be found, In: Washington Department of Fish and Wildlife. 2008. Priority Habitat and Species List. Olympia, Washington. 177 pp. http://wdfw.wa.gov/publicatlons/00165/wdfw00165.pdf or access the list from here: http://wdrw.wa.gov/conservatlnn/phs/llst/) Count how many of the following priority habitats are within 330 ft (100 m) of the wetland unit: NOTE: This question is independent of the land use between the wetland unit and the priority habitat — Aspen Stands: Pure or mixed stands of aspen greater than lac (0.4 ha). — Biodiversity Areas and Corridors: Areas of habitat that are relatively Important to various species of native fish and wildlife (full descriptions in WDFW PHSreport). — Herbaceous Balds: Variable size patches of grass and forbs on shallow soils over bedrock. — Old-growth/Mature forests: Old-growth west of Cascade crest - Stands of at least 2 tree species, forming a multl-layered canopy with occasional small openings; with at least 8 trees/ac (20 trees/ha }> 32 In [81 cm) dtah or > 200 years of age. Mature forests - Stands with average diameters exceeding 21 In (53 cm) dbh; crown cover may be less than 100%; decay, decadence, numbers of snags, and quantity of large downed material Is generally less than that found in old-growth; 80-200 years old west of the Cascade crest. — Oregon White Oak: Woodland stands of pure oak or oak/conifer associations where canopy coverage of the oak component is Important [full descriptions in WDFW PHS report p. 1SB - see web link above). <r — Riparian: The area adjacent to aquatic systems with flowing water that contains elements of both aquatic and terrestrial ecosystems which mutually Influence each other. — Westside Prairies: Herbaceous, non-forested plant communities that can either take the form of a dry prairie or a wet prairie [full descriptions in WDFW PHS report p. 161 -see web link above). y — Instream: The combination of physical, biological, and chemical processes and conditions that interact to provide functional life history requirements for instream fish and wildlife resources. — Nearshore: Relatively undisturbed nearshore habitats. These include Coastal Nearshore, Open Coast Nearshore, and Puget Sound Nearshore. [full descriptions of habitats and the definition of relatively undisturbed are in WDFW report -see web link on previous page). — Caves: A naturally occurring cavity, recess, void, or system of interconnected passages under the earth in soils, rock, ice, or other geological formations and is large enough to contain a human. — Cliffs: Greater than 25 ft (7.6 m) high and occurring below 5000 ft elevation. — Talus: Homogenous areas of rock rubble ranging in average size 0.5 - 6.5 ft (0.15 - 2.0 m), composed of basalt, andeslte, and/or sedimentary rock, Including riprap slides and mine tailings. May be associated with cliffs. — Snags and Logs: Trees are considered snags if they are dead or dying and exhibit sufficient decay characteristics to enable cavity excavation/use by wildlife. Priority snags have a diameter at breast height of > 20 In (51 cm) In western Washington and are > 65 ft (2 m) In height Priority logs are > 12 In (30 cm) in diameter at the largest end, and > 20 ft (6 m) long. Note: All vegetated wetlands are by definition a priority habitat but are not included In this list because they are addressed elsewhere. Wetland Rating System for Western WA: 2014 Update Rating Form - Effective January 1,2015 15 Wetland Rating System for Western WA; 2014 Update Rating Form - Effective January 1, 2015 16