This study attempts to provide relative magnitudes of average and marginal costs of off-site sediment-related costs in Oregon's Willamette Valley. Water treatment; road, river channel, and dam maintenance; and hydroelectric generation are examined. Road maintenance and water treatment are nonnegligible average cost items. These costs should not be interpreted as justification for erosion control as marginal cost estimates for water treatment indicate the controls on the margin would yield roughly one-third the average cost.