About 50 people gathered outside of The Rotunda near 40th and Walnut to begin a march that would cross the city from “river to river” to protest upstate “fracking,” a process that uses toxic chemical to extract natural gas from shale.

Hundreds more protesters were expected to join in as the march proceeded across the Schuylkill River to Love Park and then on to Penn Treaty Park on the banks of the Delaware River for the annual Shadfest.

The march began with a reading from the Pennsylvania constitution and a brief explanation of the fracking process. The march is an attempt to raise awareness to the damage the process in northcentral Pennsylvania could do to the Delaware River watershed, which helps supply the Philadelphia area with drinking water.

The march was organized, in part, by the group Protecting Our Waters.

Here’s a slideshow from the beginning of the march: