WA ST Dept of Ecology Biosolids 9/8/2022

City of Everett, Public Works Department, Water Pollution Control Facility BIOSOLIDS SAMPLING & ANALYSIS PLAN 3 b. Solids Management at the WPCF The WPCF has traditionally managed its biosolids program using a combination of contracted services and City staff. The City contracts the removal and disposal of biosolids annually from AC2, Oxidation Pond, or Recirculation Channel on a rotating basis. Solids dredged from AC2 and the Recirculation Channel are expected to meet Class B standards and are land applied. However, legacy solids from the Oxidation Pond are historically higher than Table 3 Pollutant Concentration Limits (WAC 173-308-160) in lead and are disposed of in a Subtitle D landfill (see Table 1). Table 1 - Allowable Biosolids Pollutants and Loading Rates (Derived from Biosolids Pollutant Limit WAC) Pollutant WAC 173-308-160 Table 1 Ceiling Concentration Limits WAC 173-308-160 Table 2 Cumulative Pollutant Loading Rates WAC 173-308-160 Table 3 Pollutant Concentration Limits Arsenic 75 mg/kg 41 kg/ha 41 mg/kg Cadmium 85 mg/kg 39 kg/ha 39 mg/kg Copper 4300 mg/kg 1500 kg/ha 1500 mg/kg Lead 840 mg/kg 300 kg/ha 300 mg/kg Mercury 57 mg/kg 17 kg/ha 17 mg/kg Molybdenum 75 mg/kg Not applicable Not applicable Nickel 420 mg/kg 420 kg/ha 420 mg/kg Selenium 100 mg/kg 100 kg/ha 100 mg/kg Zinc 7500 mg/kg 2000 kg/ha 2000 mg/kg (Reproduced from the General Permit) In 2019, the City of Everett (COE) purchased a site called Marshland located in southeastern Everett for the purpose of land application. However, since Everett uses a bid process to select its final disposal site for biosolids, the application sites vary from year to year. Marshland is leased by Snohomish Valley Farms; they bid on hauling and applying biosolids to the City property. Soil sampling at Marshland is taken by the Industrial Pretreatment group every spring and after crop cutting in years biosolids were applied to the site. For more information on Marshland sampling, see Section 4. a. Hydrographic surveys of the lagoons created by City staff assist in tracking of the quantity and distribution of biosolids prior to and after contract dredging. Plant operations staff use a Garmin device to take depth data and a sludge judge to take density samples from a boat on the lagoons. The CAD division then uses that data to produce hydrographic surveys as in Appendix F. Surveys of the AC2, Oxidation Pond, and Recirculation Channel are taken in September of each year, and after an area is dredged.