2320 RAILWAY AVE INTERWEST CONSTRUCTION INC 2023-02-02

I INTERWEST—EVERE7T CONTRACTOR'S YARD SITE IMPROVEMENTS Sitts& Hill Engineers, Inc. OPERATION AND MAINTENANCE MANUAL Job Number 18,831 I I I I 111 I I I I I I I I I Section 1 — Purpose The purpose of this manual is to provide guidelines for maintaining the permanent on-site storm drainage system constructed as a part of the Interwest — Everett Contractor's Yard Site Improvements project in Everett, Washington. Storm facilities include: o Type 2 Catch Basins o Storm Drain Piping o (2) Oil/Water Separators o (1)Stormfilter Vault o (1) Wet Pond o (1) pH sparging system Each portion of the system has to be maintained in good working condition for the system to function properly. Operations and Maintenance will be the responsibility of the Owner, Interwest Construction Company. A copy of this Operation and Maintenance Manual shall be retained on-site or within reasonable access to the site and shall be transferred with the property to any new owner. A log of maintenance activities that indicate what actions were taken shall be kept and be available for inspection by the City of Everett upon request. Section 2— Permanent Facilities Description The proposed drainage system has been designed to provide treatment of runoff prior to discharge to the City storm system in Railway Avenue. Onsite conveyance will be provided by the proposed storm piping and catch basins. Oil treatment will be provided by the oil/water separators and basic treatment will be provided by the Stormfilter vault and wet pond. Further treatment of the stormwater for high pH levels will be accomplished with a CO2 sparging system located immediately downstream of the wet pond and upstream of the outfall. Section 3— Discussion of Maintenance Any buildup of sediment, debris, vegetation, or trash that impedes the designed conveyance system may cause problems. As a result, care must be taken to keep drainage facilities clean. A "vactor" truck, or other approved means, should be used to clean the on-site catch basins. Deposits on paved surfaces should be swept or mechanically removed in order to prevent sediment or debris from entering the drainage system. Sediment removed must be disposed of at an approved site. The stormwater sparging system will require frequent maintenance to ensure that the sensors and CO2 diffusers are not fouled, and that the CO2 tanks are re-filled as needed. Calibration of the sparging system will also be required immediately upon completion of construction, to adjust the dispensation rates of CO2 suitable for treatment of the runoff. The oil/water separators, Stormfilter vault, and wet pond should be maintained according to the DOE checklists presented below. Following the DOE checklists are the manufacturer's inspection and maintenance requirements for Stormfilter vaults. SITTS& HILL ENGINEERS, INC. 1 TACOMA, WASHINGTON