Modesto Storm Drain System

Storm drains provide a vital service in every community. They remove rainwater from the streets via underground pipe systems and send it directly to nearby rivers, catch basins, or the water table below. The City of Modesto has a variety of storm drain styles throughout the community, connected to approximately 14,000 catch basins.

Keeping the drains clean and free from hazardous contamination is critical! Water is a necessity of life, and we must work together to keep it clean for everyone’s good health. Please report polluters by calling 209-577-6200 whenever you see someone illegally dumping into a storm drain.

How to Protect Your Rockwell

Rockwells make up more than two-thirds of the City's storm drain system. They are designed to drain untreated stormwater runoff by letting it percolate directly into the groundwater. Hazardous materials such as engine degreasers, used oil, antifreeze, and paint are often found in them.

  • Steam clean your car’s engine at a professional car wash, not in your driveway.
  • Clean spills or drips with absorbent material such as cat litter or sand instead of hosing it into the street.
  • Recycle your used oil at a nearby Certified Collection Center or by Curbside Collection
  • Dispose of antifreeze and other hazardous materials at the Household Hazardous Waste Collection Facility. It’s free!
  • Rinse your latex paint, brushes, rollers, and pans in the sink, not in your driveway.
  • Be careful not to wash your garden pesticides into the gutter or down the storm drain.
  1. Rockwells
  2. Positive Storm Drains
  3. Retention Basins

A rockwell storm drain is a deep hole filled with rocks that is connected to a catch basin. Rockwells range in depth from 20 to 75 feet and allow untreated stormwater to slowly seep into the ground to rejuvenate our drinking water.

It may take as long as 40 hours after a heavy rain for the ground to absorb all the water. When a heavy downpour occurs, the result may be standing water and flooded streets.

Rockwells make up more than two-thirds of the City’s storm drain system. There are approximately 10,500 rockwells in Modesto. Please protect our drinking water for generations to come by keeping all contaminants out of the rockwells in your area.