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Sumas-Blaine Aquifer Nitrate Contamination Summary

Publication number Date Published
12-03-026June 2012
VIEW NOW Sumas-Blaine Aquifer Nitrate Contamination Summary (Number of pages: 57) (Publication Size: 7110KB)

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Author(s) Carey, B. and R. Cummings
Description This report summarizes groundwater nitrate data collected over 30 years from the Sumas-Blaine Aquifer, a transboundary aquifer in northwestern Washington. Data compiled from studies by the USGS and the Department of Ecology indicate that 29% of 515 wells sampled have exceeded the 10 mg/L-nitrogen maximum contaminant level for nitrate, and 14% of the total have exceeded 20 mg/L-nitrogen. The report also summarizes physical and land use characteristics that make the aquifer especially vulnerable to nitrate contamination, including shallow depth-to-water and intensive agricultural production. The report also summarizes results of studies conducted by the Department of Ecology to evaluate impacts of dairy management practices on groundwater. Recommendations are listed for actions to reduce nitrate contamination in the aquifer, and information is provided for private well owners on testing their water for nitrate.

On February 12, 2013, the following substantive changes were made to this report:

On page 19, the chart showed the estimated contribution of nitrogen from dairy lagoons as 0.2%. We changed the number to 1.2%.

On page 20, we replaced the paragraph beneath “Dairy lagoons” with the following:
The estimate of nitrogen from dairy lagoons assumes that 110 dairies with addresses over the SBA have a lagoon with the same assumptions used in Cox and Kahle (6): an average surface area of 30,000 square feet that leaks 1 mm/day and has an ammonia concentration of 840 mg/L. These assumptions result in the following estimate for lagoon leakage:

(110 dairies) x (1,880 lb N leached/dairy-year) = 206,800 lb N/year

Although the total estimate for lagoon leakage, 206,800 lb N/year is a small percentage of the total input of nitrogen to the land overlying the entire aquifer (1.2%), lagoons may have significant localized impacts on groundwater nitrate depending on how they are constructed and managed.

On page 35, we changed the hyperlink for reference 51 to:

On page 55, we made the following corrections to Appendix D:
Changed the number for nitrogen loading by dairy lagoons from 36,100 lb/year to 206,800 lb/year.
Changed footnote 4 to: “Assumes that all dairies over the SBA have a lagoon with leakage as estimated in (6) such that:
(110 dairies) x (1,880 lb N leached/dairy-year) = 206,800 lb N/year"
Changed the following in the “Mean % of total” column:
Manure applied to crops - from 66 to 65
Atmospheric deposition - from 2.2 to 2.3
Dairy lagoons - from 0.2 to 1.2
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Nitrogen Dynamics at a Manured Grass Field Overlying the Sumas-Blaine Aquifer in Whatcom County

Focus on Groundwater Quality in Whatcom County