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COMMERCIAL COMPOSTING WATER QUALITY PERMIT DEVELOPMENT 2.3.1 Compost Leachate A variety of factors affect the nutrient or other constituent concentrations in compost leachate (compost feedstock type, compost method, carbon to nitrogen[C:N] ratio,climate, decomposition rate, and stability of compost).Based on these factors,compost leachate can potentially have high concentrations of organic compounds,nutrients, and salts (E&A Environmental Consultants,Inc.,January 2000).One of the primary concerns with compost leachate is the infiltration of nitrate into the groundwater.Studies have shown that composting of high-nutrient compost feedstocks(e.g.,manure) to transform them into less soluble forms,can result in elevated nitrates in groundwater near the subject facility.A number of studies have been performed on the compost leachate generated at different types of composting facilities.Table 2-2 shows reported concentrations of nutrients in the compost leachate of two different compost feedstocks. As shown in the table, compost leachate composition can be extremely variable.These results demonstrate that the nutrient- rich manure compost had the greatest concentrations of nutrients in its compost leachate stream.Of all the nutrients that were tested,nitrate-nitrogen was found in the greatest concentrations. TABLE 2-2 Reported Concentrations of Nutrients in Compost Leachate Total Ammonia-Nitrogen Nitrate-Nitrogen Total Ortho-Phosphorus Compost Nitrogen(N) (NH4-N) (NO3-N) Phosphorus(P) (Ortho-P) Feedstock (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) Type Yard Debrisa NA 5.1-10.5 3.6-5.8 NA NA Yard Debris NA 0.44 0.96 0.07 NA (average of 16 samples)b Manure` NA 0.58-34.3 1.84-120 NA 17.0-26.0 Manure 57 NA 8 9 NA Notes: a.The site was on a clay pad. Compost leachate was collected below the windrow.No specific mention of additional BMPs.(Governo et.al,October 2003) b. No specific mention of composting method used,additional BMPs,or whether compost leachate was from the raw compost feedstocks,composting piles,or finished piles. (EPA, May 1994) c.The site was on a geomembrane over soil. No specific mention of composting method used, additional BMPs,or whether compost leachate was from the raw compost feedstocks, composting piles,or finished piles. (Governo et. al, October 2003) d.The site was on a concrete paving stone. No specific mention of composting method used,additional BMPs,or whether compost leachate was from the raw compost feedstocks,composting piles, or finished piles. (Governo et. al, October 2003) Table 2-3 shows reported concentrations of compost leachate from a leaf composting facility in Croton Point,New York. Concentrations are compared with the benchmarks from the 1200-Z and 1200-COLS NPDES Permits.Benchmarks are not available for all of the constituents.Lead,phosphorus, and biochemical oxygen demand (BOD) all exceeded the 1200-COLS benchmarks. No constituents exceeded the 1200-Z benchmarks. PDX/041320015.DOC 7