Despite assurances from water quality experts that treated waste water from the Stringfellow Acid Pits will be safe, the Orange County Sanitation Districts joint board has decided to divert all effluent from the dump cleanup project in Riverside away from local ground water supplies and out to sea. In the process, much of the other industrial waste now being dumped into the main Santa Ana River sewage line--waste that experts say can be far more toxic than the treated Stringfellow water--also will be diverted from the underground water supply. The Stringfellow water, contaminated with toxic heavy metals and organic compounds, will be pumped from the ground beneath the dump site in Pyrite Canyon, near Glen Avon. It will first be treated at an on-site plant that is nearing completion. It will then be put into the Santa Ana River sewer line, where it will be mingled with industrial waste.