Publication Summary

Ground water monitoring was conducted at a new dairy lagoon in Whatcom County for one year. Monitoring wells were installed and sampled prior to placement of liquid manure, and monthly thereafter; the lagoon was sampled quarterly. Samples were tested for chloride, total dissolved solids, total organic carbon, chemical oxygen demand, total phosphate-P, ammonia-N, nitrite+nitrate-N, and total and fecal coliform bacteria.

Ground water monitoring was conducted at a new dairy lagoon in Whatcom County for one year. Monitoring wells were installed and sampled prior to placement of liquid manure, and monthly thereafter; the lagoon was sampled quarterly. Samples were tested for chloride, total dissolved solids, total organic carbon, chemical oxygen demand, total phosphate-P, ammonia-N, nitrite+nitrate-N, and total and fecal coliform bacteria.

Ground water downgradient of the lagoon showed elevated concentrations for all parameters. With the exception of ammonia-N, concentrations increased to maximum levels and subsequently began to decrease. At the end of the first year of monitoring, concentrations in downgradient wells were still elevated relative to concentrations prior to lagoon use. These observations are consistent with a pulse contamination source followed by leakage at a lower rate. Ground water velocity estimates at the site ranged from 0.8 to 2.1 feet per day based on chlorine travel times. Additional monitoring is recommended to determine if downgradient concentrations decrease to pre-lagoon-use levels and to assure that there are no significant adverse effects on downgradient water-supply wells.