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HomeMy WebLinkAboutPN_CR Outfall Project Narrative_v1City of Renton Project No: 27-4030 Project Narrative City of Renton: Cedar River Outfall Culvert Repair Project Page 1 of 4 Project Name: Cedar River Outfall Culvert Repair and Rehabilitation Contract: TBD City Project No: 27-4030 Department: Surface Water Utility Project Manager: Chester Bennett Date Updated: 6/5/2023 Project Narrative Project Objective This project will repair defects in stormwater culvert pipes that pass under the left (west) and right (east) banks of the Cedar River Levee between the Logan Ave Bridge and the mouth of the Cedar River at Lake Washington. These repairs will increase the life of the existing culverts, improve the structural integrity and likelihood of failure, and thus prevent potential material loss from the earthen embankments and floodwalls that comprise the levee system. These efforts will meet maintenance and safety requirements for the levee system and continue to provide protection from the 100-year storm event for properties and infrastructure along the Cedar River Levee Section 205. Summary The defects in the culverts were identified during camera / video inspections performed in 2022 with Closed Circuit Television (CCTV) equipment by the City of Renton and confirmed and reviewed by the United States Army Corps of Engineers (USACE). In total seven (7) culverts are proposed for repair and rehabilitation. Six (6) of the culverts are located along the left bank (west bank). One (1) culvert is located along the right bank (east bank). The culverts convey surface stormwater from the surrounding roadways, parking lots, and vegetated park areas within the drainage basin along the lower 1.25 miles of the Cedar River. Details of the culverts are as follows: The average culvert length is 66 feet and ranges from 20 to 165 feet. The existing host pipe diameters range from 12 inches to 24 inches. Host pipe material consists of Reinforced Concrete Pipe (RCP) and Corrugated Metal Pipe (CMP). All culverts have backflow / check valves at the downstream end that were installed in 2016. The defects at each location are isolated to one run of pipe between an upstream drainage structure and the downstream pipe end outfall to the Cedar River. The defects range from offset and separated joints, cracks, and small to medium sized holes. According to the USACE inspection report all defects in the culverts proposed for repair were assigned a rating of “Minimally Acceptable”. City of Renton Project No: 27-4030 Project Narrative City of Renton: Cedar River Outfall Culvert Repair Project Page 2 of 4 The City of Renton is proposing repairs and rehabilitation using a Cured-In-Place-Pipe (CIPP) repair method. This will allow for trenchless construction and no disturbance to the levee prism and minimal or zero earthwork and excavation requirements upstream and downstream of each culvert. No new structures will be installed or constructed. This is a repair and maintenance activity related to the stormwater conveyance system and to maintain the Cedar River Levee System. The specifications and project documents stipulate no toxins, effluent, or material with properties (hot water included) that are harmful to aquatic life and habitat shall be discharged or allowed to enter the stormwater system, surface water bodies, or surrounding waters and areas. Access will be taken from the landside at all locations. Access will be available by public right of way or from the City of Renton Airport property at Locations #1 - #6. At Location #7 a temporary construction and access easement will be needed for two parcels adjacent to the work site. Access will be needed from the Renton School District on parcel number 0723059085. An easement will also be needed from Boeing for access to the upstream structure and a work area on parcel number 0723059001. In some locations the water surface elevation of the Cedar River may be above or at the invert of the culverts proposed for repair. The CIPP repair method requires open and clear access free of water at the downstream end of the pipe. Due to fluctuations in the water surface elevation the project may need to install stormwater diversion structures or cofferdams to allow for access and successfully installation of the CIPP liner. Project Timeline June 26th – Construction Contract Advertisement July 6th – Construction Contract Award July 24th – Start Construction August 31st – End Construction Project Details Roles: 1. Design documents, plans, specifications, and exhibit to be performed by City of Renton Staff a. Project Manager - Chester Bennett, PE Consultants: 1. None. Permitting Requirements 1. Hydraulic Project Approval 2. Shoreline Exemption Permit 3. SEPA Categorical Exemption for maintenance activity City of Renton Project No: 27-4030 Project Narrative City of Renton: Cedar River Outfall Culvert Repair Project Page 3 of 4 Background The Cedar River levees were designed by the USACE in the mid-1990s, and their construction began in April 1999. In December 2000, the flood control was complete. The Cedar River levees are part of the Cedar River Section 205 Flood Damage Reduction project, constructed in cooperation with the USACE. The levees are located on the lower 1.25 miles of the Cedar River and extend from Williams Avenue N to the mouth of the Cedar River at Lake Washington. The Cedar River 205 project protects portions of downtown Renton, The Boeing Company’s 737 plant, and the Renton Municipal airport from the 100-year flood. At the time of completion of the levees in December of 2000 the obligations for operation and maintenance were transferred to the City of Renton. The USACE started certification of this levee system in 2004 which allows for adjacent areas (listed above) to be mapped as outside of the FEMA 100-year floodplain critical area. However, in July of 2012 the USACE informed the City that the certification previously issued by the USACE would expire in August 2013. The City of Renton participates in annual inspections of the Cedar River Levee Section 205 with the USACE to identify concerns and activities to maintain the current certification and qualification for the USACE PL84-99 program. Additionally, the City is responsible for managing the necessary certification of the levee system to keep current FEMA floodplain mapping unchanged. Maintenance and inspections ensure compliance with FEMA accreditation to offer sufficient protection to keep the areas in the lower 1.25 miles of the Cedar River outside of the 100-year floodplain. Project Work – Completed Plans and Exhibits Technical exhibits and GIS maps have been prepared and finalized which show: The culverts that require repair and their lengths and diameter The general vicinity and location of the culverts. Recent site visit photos for all reasonably accessible culverts upstream and downstream inverts. Access routes to the locations. Approximate areas anticipated to be used that will facilitate CIPP repairs. Specials, Specifications, & Engineers Estimate Specials for the project have been reviewed and prepared to specify the repair method as well as products, submittals, and environmental risks and mitigation for the work. Project Work – Current and Ongoing Temporary Construction Easement (TCE) Agreements TCE negotiations with Renton School District and The Boeing Company are currently in progress. Draft agreements have been reviewed by City of Renton Legal and sent to both entities. They are in Boeing’s and RSD’s court for comment and review. The proposed easement on the RSD City of Renton Project No: 27-4030 Project Narrative City of Renton: Cedar River Outfall Culvert Repair Project Page 4 of 4 parcel will provide the best access with the least amount of disruption to public access and City or Renton Parks properties. The easement on the Boeing parcel is required to complete the repair of the culvert as the upstream drainage structure is completely located on the Boeing property and is collecting and conveying only Boeing stormwater runoff. Permitting Shoreline Exemption permit will be submitted to the City of Renton CED Planning division by the Public Works Surface Water department and will include acknowledgement of a categorical exemption from SEPA requirements as the project is considered maintenance on existing infrastructure.