The Future of Stormwater

Posted on June 16, 2013 by Beth Chesson, CPESC, CPSWQ

In 2010, EPA reached a settlement with the Chesapeake Bay Foundation and others to develop additional components of a comprehensive suite of strong regulatory actions that EPA has initiated or pledged to take to restore water quality in the Chesapeake Bay and its tributaries.  These actions include a more robust application of stormwater quality requirements to all new development, regardless of thresholds set in the Phase 1 and 2 stormwater requirements.

An initial deadline to propose the new comprehensive stormwater rule was set for April 10, 2012.  However, EPA has negotiated several extensions to the deadline (the last deadline was June 10, 2013), and EPA now anticipates a December 2013 date for the draft rule.  The rule will apply to all areas – not just large and medium sized municipalities, where Phase 1 and 2 stormwater programs are currently in place.

It is EPA’s goal to incentivize redevelopment in urban built-out areas over new development in undeveloped areas, and this rule is expected to reinforce that goal.  Stormwater runoff treatment standards are expected to be more restrictive for greenfield development than redevelopment of urban areas.  The treatment standard for greenfield development is most likely to mirror the current Phase 2 stormwater treatment requirement to infiltrate the 80th, 85th or 90th percentile storm event, which is around one inch for many areas, depending on a region’s typical rainfall. Lesser stormwater runoff treatment requirements will be required in redeveloped urban areas to reduce urban sprawl.  This new rule has been dubbed “Phase 2 lite”.

EPA has also been considering whether to expand the Stormwater Phase 2 programs to encompass areas likely to develop – not just already developed areas.  In keeping with a watershed focus, EPA is also considering applying the rule on a watershed basis.  The question is not if the stormwater rule will be promulgated; it is how and where it will be applied.

So, what does all of this mean to you?  Our approach to development will have to change.  We will be incorporating stormwater infiltration practices into our development plans for new development and redevelopment.  The success of infiltration practices relies on subsurface conditions at a site, correct design, correct construction techniques, and long term maintenance.  Developers will need to engage designers with expertise in soils, vegetation, hydrology and construction techniques so these practices work properly.  An infiltration practice can fail quickly if correct construction techniques are not followed during construction, so it is likely that the design professional will be required to oversee construction. And then the infiltration practice owner (developer or property owner) will be required to maintain these structures perpetually. To reduce the long term burden of monitoring and maintaining structural infiltration practices, our future designs will need to address stormwater as an asset and incorporate its reuse into the overall design for irrigation needs and other non-potable uses. 

Additional information on the EPA Stormwater rule is available on EPA’s website.  If you have questions regarding the implications of these stormwater rules, please feel free to contact Beth Chesson of CEC’s Nashville office at (800) 763-2326.

Filed under: Civil/Site, Cultural Resources, Ecological Services, Environmental, Waste Management, Water Resources | Tagged: , | Leave a Comment »

Navigating Muddy Waters – New Effluent Limitation Guidelines Will Impact 21,000 Construction Sites Annually

Posted on January 19, 2010 by Beth Chesson, CPESC, CPSWQ

On November 23, 2009, EPA released the final Construction & Development Effluent Limit Guidelines (C&D ELG).  The final C&D ELG will impact all construction sites disturbing more than one acre by imposing non-numeric effluent limitations.  More importantly, the C&D ELG will impose numeric effluent limits for the first time on all construction disturbing more than 10 acres within approximately 4 years.  Most construction sites will need to use Passive Treatment Systems (PTS) to achieve those limits rather than the typical erosion and sediment control measures currently in use.  EPA estimates as many as 21,000 construction sites annually would need to meet those numeric limit standards.

 In the past, sediment control practices have generally been designed based upon a rule of thumb.  Many states rely on 1800 ft3/acre of drainage (or disturbed acre), which doesn’t take into consideration the discharge quality.  In fact, a sediment control measure can have an 80% settling efficiency and still produce a turbid (muddy) discharge.  With this in mind, EPA has been struggling since early 2000 to establish a C&D ELG, with prodding from environmental groups. 

 In November 2008, EPA published a draft C&D ELG that set the ELG (turbidity) at 13 Nephelometric Turbidity Units (NTUs) for sites that disturbed 30 acres or more, were located in areas of the country with high rainfall intensity, and located on soils that had at least 10% clay.  That incredibly low turbidity limit (13 NTUs) severely limited the stormwater treatment options to Active Treatment Systems (ATS) that, simply put, look and function like small waste water treatment plants.  EPA requested public comment on the draft rule and requested additional data on the cost benefit analysis, treatment feasibility, and other components.  Concerns mounted as those affected began questioning the draft rule, particularly the feasibility of achieving the 13 NTU discharge standard. 

 EPA published the final C&D ELG in November 2009 with major revisions based on the comments received.  EPA chose to greatly simplify the rule and increase the numeric standard.  Below is a summary of the final rule: 

  • All construction projects must install best practicable control technologies.
  • Sediment basins and other impoundments must be dewatered from the surface.
  • The ELG has been set at 280 NTUs.  This limit is a daily maximum average, based upon sampling for storms up to the 2 yr, 24 hr storm.  Discharges from storm events greater than the 2 yr, 24 hr are not required to meet the ELG.
  • Discharges from construction sites must meet an effluent limitation guideline as follows:
    • Within 18 months of the effective date of the rule (August 2011), sites disturbing 20 acres or more must meet the ELG.
    • Within 4 years of the effective date of the rule, sites disturbing 10 acres or more must meet the ELG.
    • For both scenarios above, the size limitations apply to “larger common plans of development” like subdivisions with multiple small lots.

 Each state will need to marry the final C&D ELG with their existing monitoring plans, which will be a huge task.  Additionally, EPA has noted that as each state’s construction stormwater permit comes up for renewal, these requirements must be inserted.  EPA is the permitting authority in four states.  Their general permit is due to expire in June 2011 and will be reissued with the ELG requirements in it at that time.  Interestingly, North Carolina’s permit was in the midst of renewal when the ELG rule was finalized, and EPA only allowed their permit to be renewed for 18 months (through August 2011).  After that date, the reissued permit must include the ELG requirements.

 As indicated earlier in this blog, PTS will generally be required to meet the numeric standard of 280 NTUs.  A PTS incorporates a flocculant with a standard construction site practice.  An example of a PTS is a jute-lined ditch that has been impregnated with polyacrylamide (PAM).   Design components that must be considered include mixing zones and settling zones.  At this point, we don’t have design tools that dictate the amount flocculant to be used on a site.  Flocculants and soils must be matched (not every flocculant works on every soil), and the applications tweaked in the field for peak performance.  Then the flocculant must be reapplied after rain events.

You can expect to have the ELG requirements inserted into the permit language if your state’s permit expires before August 2011.  If, however, your permit was reissued before the rule was finalized and without the ELG language in it, EPA could administratively open the permit to have the language inserted into it.  I suspect that between June 2011 (when EPA’s Construction General Stormwater permit expires) and August 2011 (the deadline to begin implementing the ELG) some permits may be administratively opened.  That option is certainly possible.

 If you have any questions about the C&D ELG, how it may impact an upcoming project, and how you can meet the numeric standard, contact Beth Chesson, CPESC, CPSWQ at bchesson@cecinc.com or 615-333-7797.

Filed under: Civil/Site, Waste Management, Water Resources | Tagged: , , | Leave a Comment »

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