Management and maintenance of earthen manure structures: Implications and opportunities for water quality protection

Concern about potential water quality impacts of earthen manure storage structures and lagoons has resulted in increased technical design oversight, but relatively little attention has been paid to management and maintenance requirements. A detailed on-site survey was used to obtain information about management and maintenance practices at 33 earthen structures containing liquid and slurry manures in Iowa. Fifty-five percent experienced minor spills during manure unloading, 27% showed erosion of compacted clay liners caused by agitation or manure inflow, 24% showed evidence of animal burrows in berms, 12% experienced plugging or freezing of gravity flow inlet pipes, 6% had tree growth in berms, and 6% had inadequate freeboard at the time of the interview. These factors, singly or in combination, were reported or observed at 76% of facilities surveyed, while 9% experienced major spills since construction. Nineteen technical and educational publications were also examined and gaps in coverage of related management and maintenance topics were identified. Several technical, educational, and policy opportunities are discussed that may reduce risks to water quality- associated with the operation of earthen manure structures.