New homes built in Manteca may soon have a new feature — rain barrels and cisterns.

But instead of being required due to the drought, the need for them is being driven by a federal edict that essentially requires roughly 85 percent of all storm water to be retained on site within a developed parcel whether it is a commercial enterprise or a part of a residential subdivision.

The Environmental Protection Agency has identified urban storm run-off as the biggest source of pollution for America’s waterways.

And while the rule will apply to all new projects after July 1 save those already at a specific point in the approval process, “redevelopment” of existing parcels may also fall under the requirements in certain circumstances. For example, the parking  lot being completely redone from the ground up at Grant and Yosemite avenues in downtown Manteca would have had to contain 85 percent of the storm water on site had it been done six months from now. If it had simply been a resurfacing of the lot, however, the new run-off rules would not have been triggered.

The need to comply with the federal National Pollution Discharge Elimination System permit administered by the EPA brought builders developers, environmentalists and engineers Thursday to a workshop at the Manteca Transit station.

Manteca along with Lathrop, Tracy, Lodi, Patterson and San Joaquin County are working to develop run-off standards to provide consistent guidance in implementing the requirements.

The workshop was designed to receive input from stakeholders in order to fashion design regulations to meet state-mandated requirements.

The permit zeros in on projects creating additional impervious surfaces — roof tops, streets, sidewalks, parking lots, and such — to reduce run-off from not just storms but landscape irrigation as well.

One likely scenario for parking lots is the elimination of continuous curbing between asphalt and landscaped areas. An example is what the city put in place last year on the southeast corner of Woodward Park for the parking lot near the storm retention basin. There are notches in curbing along travel lanes while raised concrete curbing has been placed with “wheel stops” to allow storm water to flow into landscape areas where it ultimately will infiltrate into the ground.

One solution likely to become prevalent is the use of vegetated swales or small “valleys” to capture runoff from streets and large areas such as parking lots. And while many swales that exist today are planted in grass, that isn’t likely to happen for several reasons. They include the permit requirements frown heavily on using pesticides and any chemicals in storm run-off areas to reduce pollution. The guidelines also want water use conserved at times there isn’t storm run-off.

That would mean such swales would most likely have trees and native shrubs.

Other possible measures that could be taken include:

• using porous pavement such as those that allow small squares of grass to grow between pavers for driveways and patios.

• tree planting and preservation.

• putting roofs over large waste bin enclosures, outdoor material storage areas as well as fueling facilities.