Advocates working to keep the Del Mar Horsepark open for equestrian shows, a riding school and other activities released a report Friday that indicates the park’s water issues originate outside the property.

Testing lab ALS Group USA Corp. of Irvine examined water samples taken during seasonal rains Dec. 28 upstream and downstream from the horse park. The upstream samples showed significantly higher amounts of coliforms, pollutants that come from human and animal waste.