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Caption: Un-ionized ammonia, which can be toxic to aquatic life at very low levels, was measured at twelve locations, with varying frequencies, in the Stemple Creek watershed by the North Coast Regional Water Quality Control Board (NCRWQCB) from 1990-1994. The graph shows data collected at five locations (going downstream from left to right) from 1992-1993. The maximum concentration found among all stations and monitoring events was 2.66 mg/L, and the minimum concentration was 0.001 mg/L. The NCRWQCB notes that there were dairy cows in the creek at station SCPVR when samples were taken in March and April, 1993. The reference value represents the maximum NCRWQCB Stemple Creek TMDL threshold (0.025 mg/L) to be met by 2004 whenever and wherever the aquatic habitat is suitable for salmonid migration, rearing, and spawning in the watershed (Salisbury, 1997). See Picture for a map of the stations and Info Links for more information.
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