A new State Pollutant Discharge Elimination System (“SPDES”) General Permit For Stormwater Discharges From Construction Activity took effect on January 29, 2015. The New York State Department of Environmental Conservation’s (“DEC”) new General Permit, GP-0-15-002, replaces the prior version, GP-0-10-001. It applies to construction projects that disturb an acre or more, with lower thresholds applying in certain critical environmental areas, including the New York City Water Supply Watershed. While it carries over many of the former version’s requirements, the new General Permit changes requirements for erosion and sediment controls employed during construction, revises post-construction controls for new impervious surfaces, and provides substantial new flexibility for “redevelopment activities.”

To bring its new General Permit into line with an analogous federal permit and recent related regulations, DEC’s new General Permit adopts federal guidelines for the selection, design, and implementation of erosion and sediment control measures to be used during construction. Consistent with these guidelines, the new General Permit, rather than employing numeric limits, contains technology-based effluent limits that require an owner or operator of a construction activity to “minimize” pollutant discharge during construction through the use of control measures that are “technologically available and economically achievable (BAT) and practicable (BPT) in light of best industry practice.” DEC has determined that compliance with its New York State Standards & Specifications for Erosion & Sediment Control (the “Blue Book”), which will soon be updated, satisfies the federal guidelines.

For post-construction stormwater control measures, the new General Permit reflects DEC’s concurrent update to its New York State Stormwater Design Manual. The Design Manual provides details on how to size, design, select, and locate stormwater management practices at a development site in order to comply with the General Permit’s stormwater performance standards; it is effectively the centerpiece of DEC’s construction stormwater General Permit program.

One important change to the Design Manual relates to management of runoff from newly-created impervious surfaces. The 2015 Design Manual increases documentation requirements for the owner or operator of a construction activity who cannot comply with certain stormwater management standards. For example, the Design Manual continues to require an owner or operator to capture or treat 90% of the runoff from project-created impervious surfaces that arises from an average one-year storm event (called the “water quality volume”) by using “green” stormwater management practices that reduce runoff (such as infiltration basins or green roofs). The 2015 Design Manual, however, now requires that when the owner or operator cannot achieve adequate runoff reduction, it must discuss each green stormwater technique that it considered and rejected, demonstrating how each was technologically impossible or created a cost wholly disproportionate to its environmental benefit.

At the same time, the new General Permit and the updated Design Manual add new flexibility for what were formerly called “redevelopment projects.” Projects that disturb and reconstruct existing impervious area are now called “redevelopment activity.” The 2015 Design Manual allows an owner or operator of a redevelopment activity to reduce less than the otherwise-required water quality volume, without having to demonstrate that physical constraints prevent further reductions. Moreover, the 2015 Manual, as adopted by the General Permit, now allows redevelopment activity criteria to apply when an owner or operator redevelops impervious surfaces that were removed within the last five years.

How DEC will ultimately apply the new General Permit and Design Manual in practice remains to be seen. And a challenge to the new General Permit by environmental groups opposed to the flexibility afforded to redevelopment activity is still possible. For more information about DEC’s new General Permit or other stormwater-related issues, contact Michael Bogin.