The top court highlighted the catastrophic impact on water bodies, groundwater and agricultural lands, which has led to economic hardship for farmers and posed significant public health risks.

Portland's sewer system combines sewage and runoff into the same pipes. Sometimes heavy rains cause those pipes to overflow. But a sewer overhaul 14 years ago has drastically reduced this pollution.

The Supreme Court held that polluters remain liable to compensate victims and restore the environment until the damage is undone ...