Two thirds of the rain gardens installed throughout the city to control stormwater don’t work, according to a new report from City Comptroller Scott Stringer.
An audit of the New York City Department of Environmental Protection (DEP’s) rain gardens found visible maintenance deficiencies at 95 of the 102 rain gardens in Brooklyn, Queens and the Bronx.
Some 66 percent exhibited two or more conditions that DEP’s own maintenance manual states can impede their proper functioning, including sediment buildup, compacted and depleted soil, weeds and overgrown plants.
Just over half were marred by trash, weeds, overgrown grass and missing plants.
And 29 percent had four or more deficient conditions.
Only seven of the 102 sampled rain gardens had no visible deficiencies.
“Seven years after our city was devastated by Superstorm Sandy, we cannot afford to shirk our responsibility to improve its resiliency,” said New York City Comptroller Scott M. Stringer.
“We must use every tool we have to lessen the devastating impacts of future storms. The City built thousands of rain gardens to help control stormwater and protect our waterways, streets, homes, and small businesses, but ouraudit uncovered a dysfunctional maintenance program that wastes taxpayer dollars and puts critical infrastructure at risk. DEP must step up to the plate and properly maintain these vital resources. We cannot win the battle to protect New Yorkers against the next superstorm and keep our waterways clean if we allow these vital resources to fall into disrepair due to neglect.”
As of April 2018, DEP was responsible to manage 2,511 rain gardens that the City had built at an estimated construction cost of just over $100 million.
Rain gardens contain plants and engineered soil that are designed to absorb and infiltrate large amounts of stormwater and reduce the volume of runoff that enters the City’s combined sewer system where it mixes with wastewater from homes and businesses.
Properly maintained rain gardens help control stormwater to minimize sewer overflows from heavy storms that could otherwise pollute the City’s waterbodies.
According to DEP, well-maintained rain gardens also improve streetscapes and street drainage, help purify the air, and reduce temperatures during hot weather.
The audit examined DEP’s maintenance of 102 of the 805 rain gardens that DEP was supposed to fully maintain as of April 2018, following their construction-guaranty periods of up to two years.
In Fiscal Years 2018 and 2019, DEP spent more than $5 million per year to maintain approximately 805 of the 2,511 rain gardens then under its jurisdiction.
DEP currently manages more than 4,000 rain gardens that cost the City an estimated $161 million to build. To keep the City’s rain gardens functioning well and in good appearance, DEP developed a detailed Rain Garden Maintenance Manual. It prescribes nine separate categories of maintenance tasks to be performed once or twice per week at each rain garden.
In sum, the audit found that DEP has not maintained its rain gardens in accordance with its own manual.