FAYETTEVILLE — About 50 protesters turned out in Fayetteville to oppose a planned oil pipeline across northern Arkansas.

Opponents said Saturday that the planned Diamond Pipeline is a threat to water, protected species and historic sites.

The planned 440-mile pipeline by Plains All American Pipeline and Valero Energy Corp. would extend from Cushing, Oklahoma, to a Valero refinery in Memphis, Tennessee, and would cross 14 counties in Arkansas and five Arkansas Rivers.

Diamond Pipeline has emphasized the reliability and safety of its pipeline and the company said it will use horizontal drilling to place pipe under water crossings.

The company says it plans to begin construction this year and complete the project during 2017.