DEP Releases Eye-Opening Reports on Green Infrastructure Progress and Challenges

Last month, DEP submitted two important reports to the state on its green infrastructure program.  These reflect significant progress – and significant challenges – over the program’s first 5 years.

Since 2010, DEP has invested over $250 million in GI projects, which now capture the first inch of runoff from 437 acres of impervious area.  However, DEP fell short of its 2015 targets for GI construction.  To catch up and meet its higher targets for 2020, DEP needs to increase its rate of GI implementation to nearly 6 times what it has been in the last 5 years.

See below for more highlights and links to the full reports.


DEP’s “Green Infrastructure Contingency Plan,” includes these key findings and proposals:

  • Through 2015, DEP spent $259 million on green infrastructure (GI) projects, which is much more than the minimum amount ($187 M ) they promised to spend in that time frame.
  • DEP now has a total of 3,830 individual GI “assets” constructed, under contract, or out for bid.  The vast majority of these are “right of way bioswales” (which DEP now calls “rain gardens”).  The number of assets grew very rapidly from 2014-2015.
  • However, DEP achieved only 40% the target amount of impervious area managed with GI:  437 acres actually constructed, under contract, or out for bid, as compared to the 1,181 acres target in DEP’s 2012 consent order.  DEP identified a number of challenges to GI implementation in the right-of-way and on public properties, relating to technical constraints encountered on potential GI sites.
  • Despite the challenges of GI in the right-of-way that DEP identified, the only approach DEP proposed to make up the shortfall is to do more GI in the right-of-way in 8 sewersheds, to be completed by the end of 2020.  This proposal is subject to NYS DEC’s review and approval.
  • To meet its targets for 2020, DEP needs to speed up the rate of GI implementation from 2016-2020 to nearly 6 times what it has been in the last 5 years. The target for the year 2020 is to manage 3,150  impervious acres with GI.
  • Looking ahead, DEP questions whether it’s worth doing any GI in Open Waters/East River sewersheds, since DEP says those water bodies already meet water quality standards based on 30-day average levels of fecal coliform, but not based on EPA’s most current, science-based standards that measure enterococcus bacteria.

The “Green Infrastructure Performance Metrics Report” presents DEP’s projections of CSO reductions that will be achieved with GI.  It also includes a “Monitoring Strategy and Protocols Report” as an appendix.  Key points include:

  • DEP’s reports high performance for GI in the right of way. DEP projects that using bioswales to manage 1.5% of impervious area in the combined sewer areas would achieve a 2.4% CSO volume reduction.  (1.5% is the 2015 target that was not reached.)  Put another way, this amounts to 1 gallon of CSO reduced for every 2 gallons of stormwater capture, and 0.4 million gallons of CSO reduced annually per acre of impervious area managed with GI.
  • However, for projects built over the next 15 years, DEP expects less CSO reduction per gallon of stormwater capture. DEP expects that future projects will have “a much greater share of detention based GI projects, assuming that the Program will need to diversify to include different GI technologies in the future.”  Detention refers to projects such as “blue roofs” and underground vaults, which temporarily hold and then slowly release polluted runoff into the sewer system.  DEP  says that these are less effective at CSO reduction per gallon of runoff captured, and they typically do not include any vegetation.
  • DEP outlined a GI monitoring strategy aimed at measuring performance, improving designs, refining maintenance standards, and improving stormwater rules for new development and incentive programs for GI retrofits on private property.  The monitoring strategy was peer-reviewed by academic experts.  It also states DEP’s intent to measure “co-benefits” of GI, with an initial focus on urban heat island mitigation and increases in pollinator species like birds and insects.

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