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CITY OF EVERETT SPECIAL PROVISIONS <br /> <br />Beverly Lake Water Quality Retrofit Division 7 – STORM, SEWER, WATER August 2023 <br />WO No. - UPUP3745 SP – 194 <br />Pedestrian Guard shall be per Section 8-27 of these specifications. <br /> <br /> <br />Internal Components <br /> <br />All system components including engineered biofiltration media, underdrain <br />stone, PVC underdrain piping, and mulch must be included as part of the <br />bioretention system and shall be provided by the manufacturer, except as noted <br />herein. <br /> <br />Engineered biofiltration media shall consist of both organic and inorganic <br />components. Stormwater shall be directed to flow vertically through the media <br />profile, saturating the full media profile without downstream flow control. The <br />media shall meet the following parameters: <br /> <br />1. Engineered biofiltration media minimum treatment flow rate shall be <br />140”/hr. <br />2. The system shall be designed to ensure that high flow events shall bypass <br />the engineered biofiltration media preventing erosion and resuspension of <br />pollutants. <br />3. The system shall remove a minimum of 85% Total Suspended Solids <br />(TSS). <br />4. The system shall remove a minimum of 62% Total Phosphorus (TP). <br />5. The system shall remove a minimum of 34% Total Nitrogen (TN). <br /> <br /> <br />Underdrain stone shall be of size and shape to provide adequate bridging <br />between the media and stone for the prevention of migration of fine particles. <br /> <br />Underdrain stone must also be able to convey the design flow rate of the system <br />without restriction and be approved for use in the Filterra Bioscape Bioretention <br />System by the manufacturer. <br /> <br />PVC Underdrain Piping shall be SDR35 with perforation pattern designed to <br />convey system design flow rate without restriction. <br /> <br /> <br />Mulch shall be double shredded wood or bark mulch approved for use with the <br />Filterra Bioscape Bioretention System by the manufacturer. <br /> <br />Vegetation shall be provided by the contractor and comply with the type required <br />by the site plans and shall be alive and free of obvious signs of disease. Plant <br />materials shall be in accordance with Section 9-14.7 and manufacturer’s <br />requirements. Plants shall be minimum 1-gallon size. <br /> <br />Concrete inlet shall be provided by the Contractor and shall conform to COE <br />Standard Drawing 4-01. <br /> <br />Beehive grate shall be provided by the Contractor and shall be East Jordan <br />7750O Grate (Product #00775063) or approved equivalent. <br /> <br />Aluminum access ladder shall be a permanently affixed ladder and shall attach to <br />the structure wall at at least three elevations, including top and bottom. The <br />ladder shall be rated for exterior use and shall have a load capacity of at least