Agmt11 Duke's Root Control, Inc.

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SOUTH BAYSIDE SYSTEM AUTHORITY Memorandum June 11, 2010 To: Root Control File (S: drive S:/Discharges) From: N Domingo, K Kaufman Subj: Razorooter II, Foaming root control The West Bay Sanitary District requested to know the official SBSA policy on the use of Razorooter II as a foaming root control chemical agent in the collection system. Background Razorooter II is a herbicide used as a root control agent. The active ingredient is Diquat Dibromide. It is applied as a foam typically composed of 37.3% active ingredient. Dukes Root Control Inc. is the primary vendor being contracted to perform this service for collection agencies using this form of root control. It replaced Metam - Sodium , also known as Vaporooter II due to Vaporooter's toxicity. The City of Belmont and the San Mateo County DPW are currently using Razorooter II as applied by the Duke's Root Control service. The City of San Carlos may be contracting with Dukes to do a percentage of their system. Discussion The issues of concern to SBSA are: • Since Diquat Dibromide is toxic to aquatic life with published LC50s below 500 mg/L, as a waste it would be considered a hazardous waste. As a waste discharge it would not be allowed into the sanitary sewers since it would be classified as a hazardous waste under Califomia regulations. Used as a root control agent it is not considered a waste and therefore is not regulated as a hazardous waste. • Diquat Dibromide has been tested for toxicity to a wide range of organisms, including the two species SBSA uses for toxicity testing. One study found the 96 hour LC50 for Opossum Shrimp (Americamysis bahia) to be 2 mg/1. Another study found the 96 hour LC50 for Rainbow Trout (Onchorhynchus mykiss) to be 14.8 mg/L. • The specific gravity of the root control solution (37.3 %) is 1.2. It is estimated that each gallon of product contains 3.7 lbs. of active ingredient. To calculate concentration of the active ingredient from a project using this form of root control here at the plant the following example was used: If 10 gallons of the 37.3 % active ingredient solution were used for a root control project in a 24 hour period and the flow during that period was 15 MGD, the average concentration of Diquat Dibromide would be 0.3 mg/1, below the toxic concentration of 2 mg/1. This assumes no removal through the treatment plant. S: \Discharges_ Non - routine & Low VolumelNon Routine DischargeslRoot Control ProductslRazorooter Il.docx printed 2/1/11 2:26 PM