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HomeMy WebLinkAboutM_Delivery Memorandum_181018_v1 k:\project\32900\32978\projectdocs\reports\delivery memorandum 2018-10-18.docx Technical Memorandum To: Angelea Weihs, City of Renton From: Anna Ly, PE Lori McFarland, PE Jeff Grey, MS, PWS Greg Laird, PE Tom Early, PLA Copies: Kevin O’Brien, PhD Date: October 18, 2018 Subject: May Creek Trail Extension — Delivery Memorandum Project No.: 32978 The following delivery memorandum documents the design criteria, decisions, assumptions and calculations. The trail is designed to a 30% level and was prepared consistent with the WSDOT Plans Preparation Manual and the Standard Specifications, 2018 edition. The May Creek Trail Extension project is a proposed continuation of the existing May Creek Trail located on the west side of I-405 and north of May Creek and will extend underneath I-405 to the east, to the edge of pavement at Jones Avenue NE. The trail is approximately 815', 270' of which will fall under WSDOT right of way (ROW). The trail will be constructed by WSDOT as a component of the I-405 widening project. Page 2 May Creek Trail Extension — Delivery Memorandum October 18, 2018 k:\project\32900\32978\projectdocs\reports\delivery memorandum 2018-10-18.docx The proposed trail will be a soft surface trail and designated for pedestrian-use only as originally proposed in the Trails and Bicycle Master Plan, and follows the WSDOT-provided alignment within the WSDOT ROW (electronic files dated April 20, 2018) and a conceptual plan provided by WSDOT dated November 13, 2017. The design and concept were adapted and incorporated into our 30% design plans. The portion of trail on City of Renton property will be 6-foot wide, generally following existing elevations and loosely paralleling the alignment of May Creek. The portion of trail in the WSDOT ROW will be 8-foot wide and located to the south of the proposed bridge abutment. A chain link fence Type 4 per WSDOT standard plans, is proposed along the south side of the trail alignment within the WSDOT ROW. Design Criteria The May Creek Trail Extension has been designed per applicable standards presented in the attached Design Criteria memorandum. 30% Plans The following plan sheets have been prepared and are attached: Cover Sheet and Site Plan Existing Conditions TESC Plan Trail Horizontal Alignment Control Plan Trail Grading Plan Trail Vertical Profile Tree Retention / Land Clearing Plan Mitigation Planting Plan Mitigation Planting Schedule and Details Temporary Irrigation Plan Temporary Irrigation Details Cost Estimate The preliminary cost estimate is $138,000. The estimate is based on historical unit prices from similar projects, other current cost data, and cost data from WSDOT’s unit bid analysis database. The breakdown of the standard items is included in the attached Preliminary Construction Cost Estimate. Tree Worksheets A completed City of Renton Tree Retention Worksheet is in the attachments. Arborist Report The site has been evaluated by a certified arborist and the findings are presented in the attached Arborist Report. Per the report, two black locust trees are recommended for removal, and the other trees on-site are recommended for retention. Drainage Memorandum A drainage memorandum has been prepared consistent with the 2017 City of Renton Surface Water Design Manual and is included in the attachments. It is assumed that the Project will have a Targeted Drainage Review since it is located in/or adjacent to a flood hazard area. No stormwater management facility or conveyance is anticipated. Page 3 May Creek Trail Extension — Delivery Memorandum October 18, 2018 k:\project\32900\32978\projectdocs\reports\delivery memorandum 2018-10-18.docx Trail and Buffer Restoration The May Creek Trail Extension Project is entirely located within the 200' buffer of May Creek and avoids the wetland and wetland buffer north of May Creek and east of I-405. This wetland is identified as Wetland 7.2R in WSDOT’s Wetland and Stream Assessment Report (January 2018), and the boundaries were confirmed by Otak staff in June 2018. To offset conversion of approximately 3,660 SF (0.1 acre) of vegetated stream buffer for the trail extension, the project includes enhancing the 200-foot wide stream buffer along the trail east of I-405 by removing invasive plants and restoring the native riparian vegetation community between May Creek and Wetland 7.2R. The Wetland 7.2R buffer partially overlaps with the stream buffer. A dense thicket of Himalayan blackberry extends from May Creek north to Wetland 7.2R with patches of Japanese knotweed and reed canarygrass in the understory near May Creek. Proposed buffer enhancement actions include removing the invasive plants, supplemental planting in the existing understory to increase native plant diversity and restoring native forest habitat. For shoreline compliance in achieving no net loss of functions, the enhancement of approximately 1/3 acres of existing buffer is proposed to offset the conversion of 3,660 SF of low-functioning buffer to achieve an overall functional lift in the shoreline regulated area. Attachments Design Criteria Memorandum 30% Plans Preliminary Construction Cost Estimate Tree Retention Worksheet Arborist Report Drainage Memorandum SEPA Environmental Checklist Land Use Permit Master Application Shoreline Permit Application Report, including Critical Areas Review Buffer Mitigation and Monitoring Plan Biological and Habitat Assessment