Per the City of Rockville:
Property Owners Can Help Reduce Pollution and Flooding
Rainfall that lands on conventional lawns, roofs, patios, walkways, and driveways rapidly accumulates into runoff. This runoff collects pollutants like pet waste, fertilizers, pesticides, car fluids, and trash before entering storm drains and being carried to local streams and the Chesapeake Bay. Stormwater runoff not only impacts the health of our local waterways, but can cause drainage issues around your home or yard and increase the chances of flooding for your downstream neighbors.
Private property owners can play an important role in reducing pollution and flooding, and creating wildlife habitat by installing small-scale stormwater projects.
Single-family homeowners and nonprofits, including religious institutions, private schools, homeowners associations and condominium associations, can receive up to a lifetime maximum of $2,500 in rebates for the approved projects below.