Blue Mountain Construction Group, LLC 11/19/2024

CITY OF EVERETT SPECIAL PROVISIONS 3rd Ave Water Quality Facility Division 7 – STORM, SEWER, WATER September 12, 2024 WO No. – UP 3775 SP – 179 The Pretreatment Unit shall be capable of treating the design flow specified without prematurely bypassing flows via an internal bypass or external flow splitter. The Pretreatment Unit shall be designed with a sump chamber for storage of captured sediments and other captured pollutants. Hydraulics: The Pretreatment Unit shall convey the flow from the peak storm event of the drainage network, in accordance with required hydraulic upstream conditions as defined by the Engineer. If a substitute treatment unit is proposed, supporting documentation shall be submitted that demonstrates equal or better upstream hydraulic conditions compared to the device specified. This documentation shall include a hydraulic gradeline for the upstream and downstream system and headloss though the treatment unit during the 100-year storm. This documentation shall be signed and sealed by a Professional Engineer registered in the State of Washington. All costs associated with preparing and certifying this documentation shall be born solely by the Contractor. The Pretreatment Unit shall include internal orifice controls to allow the water quality treatment rate of 2.2 cfs (cubic feet per second) through the system without reaching an elevation of 508.9 feet in the upstream stormwater structure, which would divert flow around the Water Quality Treatment Facility. The internal orifice controls shall limit flows rates at higher flow rates to acceptable flow rates to the Water Quality Treatment Facility. Water Quality Treatment Facility Provide a manufacturer’s certificate of compliance in accordance with Section 1- 06.3 demonstrating that the proposed product complies with the following requirements: The Water Quality Treatment Facility shall has approved General Use Level Designation (GULD) for “Basic, Metals, Phosphorus, and Oil Treatment” from the Washington Department of Ecology. The Water Quality Treatment Facility shall be sized in accordance with the GULD approved design requirements for the minimum water quality flow rate or 2.2 cfs before bypassing flows through the overflow beehive grate with a peak flow rate of 7.0 cfs as shown in the Plans and specified herein. Exterior dimensions shall fit within the designed footprint of the facility. Hydraulics: The water quality treatment structure shall treat the flow from the water quality storm event as discharged from the upstream structures and in accordance with required hydraulic conditions. Flows shall be distributed evenly across the top of the water quality treatment media as shown in the Plans. Diablo Nine Bark shrubs shall be four plants per row with two rows at 12 foot spacing within rows per Medium Strub layout for 4.C in Appendix L. Shrubs shall be planted at a 4ft minimum distance from the perimeter walls and drainage structures, bubblers and cleanouts.