A Guest Post by Michael Schmidt, P.E. BCEE

Vice President, CDM Smith

As the panels presented, excess nutrients produce adverse impacts in lakes, streams, and estuaries. Narrative nutrient requirements are being replaced with numeric limits through TMDLs and nutrient criteria such as in Florida. The key for cost-effective public infrastructure is to:

1. Consider the full range of parameters and the entire “pollution pie” across the watershed including air, agricultural and urban stormwater, wastewater, and legacy sediment and groundwater sources with natural watershed contributions. Consider each parameter and the schedules for TMDL implementation.
2. Allow flexibility in the scientific evaluations to determine the appropriate levels of nutrients and limiting nutrients for the highly variable systems across Florida and the US (e.g., crystal clear springs vs. blackwater systems with low DO).
3. Consider and manage the full range of hydrology and potential surface and ground water interactions.
4. Coordinate floodplain management with stream buffers to protect riparian zones and promote natural system flow and load attenuation.
5. Consider a BMP Treatment Train approach founded on low impact, green components to capture and harvest stormwater for irrigation of landscaping (reduced clearing with lot buffers and recess landscape areas for parking lots, roadways, et al).
6. Consider alternative water supply opportunities (direct and indirect recharge).
7. Define the benefits for the costs over a life cycleof at least 20 to 50 years (or 100+) along with:
   1. Potential future emerging issues such as sea level rise and other potential climate changes in rainfall patterns, system recharge, and flow regimes.
   2. Consideration of diminishing returns based on limiting nutrients.
   3. Contingencies for uncertainty based on sensitivity evaluations.
8. Seek synergies and cost savings for implementation with other programs such as:
   1. Flood, erosion, and sediment control,
   2. Transportation,
   3. Wastewater,
   4. Reuse,  
   5. Parks and greenways,
   6. Remediation, and
   7. Restoration.
9. Update your program every 5 to 10 years and and adapt as necessary.

Many thanks to Michael and CDM Smith for their continuing support of FWEA and the IWRC.  Click here to download a copy of Michael Schmidt’s Presentation.

Nutrient Management in Watersheds

There are almost 5,000 nutrient TMDLs in the US with many additional TMDLs still to be completed. Now that state surface water quality numeric nutrient criteria have been finalized for Florida, the number of water segments impaired for nutrients is expected to grow substantially. Nutrient TMDLs will need to be developed for these impaired water segments. US EPA is in a national stormwater rulemaking process with new criteria expected in late 2012 or early 2013. This new rule may expand NPDES MS4 jurisdiction and may require the retrofit of existing development to reduce pollutant loads to impaired surface waters.

There are many different potential point and non-point sources of nutrients in a watershed. It is very important to accurately quantify all sources and magnitudes of nutrients so that an effective solution can be developed and implemented. For example, if a lake is phosphorus limited, and a vast majority of the phosphorus load to the lake is from internal recycling from lake bottom sediment, treating all of the stormwater entering the lake would provide minimal water quality improvement. Millions of dollars could be spent with negligible water quality improvement. In this case sediment removal or chemical inactivation would be required to improve lake water quality.

Monitoring of water flow rates and chemical characteristics is essential to calibrate hydrologic budget volumes and nutrient budget loads developed by modeling or calculation. The larger the number of measurements the greater the confidence in the results. Many watershed nutrient loading studies are completed solely using literature values. This can lead to incorrect results and the expenditure of funds with no water quality improvement.

Most of our rain events (~90%) are one-inch or less in an average rainfall year. To reduce nutrient loads in stormwater runoff and improve surface water quality, we should focus treatment on runoff from common rain events, up to 2 or 3-inches. There is no need to treat the runoff from a 5-, 10- or 25-year storm for water quality improvement. Most of our runoff is produced by directly connected impervious areas, an impervious area connected directly to a closed drainage system. Even in hydrologic “D” soils, runoff from non-directly connected impervious and pervious areas is minimal for common rain events. Disconnecting impervious areas is an excellent and low cost method to reduce the runoff volume from a development.

At present, much of our stormwater runoff is not beneficially used and ultimately is lost to tide. Rainwater and stormwater are resources which should be captured and reused for irrigation, gray water, cooling, etc. Up to 60% of our water use does not require potable quality water. Capturing and reusing stormwater runoff reduces nutrient loads to receiving waters and reduces the demand for potable water.

An integrated watershed approach to nutrient management involves a holistic analysis considering all sources and nutrient loads in a watershed. If only point source reductions are mandated, evaluate alternative non-point source projects or in-water projects (i.e. dredging). Determine which solutions have the lowest life cycle cost per mass of nutrient removed and which are the most environmentally beneficial (reduced GHG emissions). The best option may involve treating point sources to a cost effective level and then adding non-point source projects to achieve the remaining required nutrient reduction. The triple bottom line approach considers economic, environmental and social issues.

 A copy of Jeff’s presentation can be viewed by clicking the following link: Jeff Herr’s Presentation

Many thanks to Jeff Herr and Brown & Caldwell for their continuing support of FWEA and the IWRC.

Justin Gregory followed Dr. Pitt’s presentation with a presentation on Jones Edmunds’ experiences with implementing green stormwater infrastructure or low impact development (LID) stormwater practices in Florida.  His presentation focused on the following aspects of LID implementation:

• Regulatory – The Sarasota County LID manual was used as an example of how a regulatory framework can be established to promote LID in the state and provide the reasonable assurance that practices will meet state stormwater standards through average-annual performance-based design requirements.
• Monitoring – A swale monitoring study, which showed how effective swales could be as a green stormwater practices, was used as an example of how monitoring the performance of LID under Florida conditions is an important part of understanding how effective LID can be as a stormwater practice.  
• Design and installation – An example of how the successful design and installation of green stormwater practices in a retrofit situations can help achieve TMDL and BMAP goals was shown.   
• Paradigm changes – Finally, Justin summarized the importance of continuing to evaluate our stormwater management paradigms and gave some examples of current paradigms that may need to be changed.

A highlight of Justin’s presentation was his use of prezi, an alternative to Power Point, which encourages a less linear approach to presentations. A copy of Justin’s presentation can be viewed at the following link: http://prezi.com/fgpd2vzm5zds/implementing-lid-in-florida/?auth_key=dd238ec04b7abbdf717e187ff9a31c97ce56f84a

Many thanks to Justin Gregory and Jones Edmunds for their continuing support of FWEA and the IWRC.

Dr. Pitt spoke on failure modes of green infrastructure.  Here is a link to Robert Pitt’s Presentation.  His national perspective is extremely timely as Florida considers a new stormwater rule that could potentially impact the types and distribution of the stormwater infrastructure that we design, construct, and maintain.   In general, we know that stormwater infrastructure may become more localized and maintenance programs will need to improve and become more sophisticated (yet remain cost-effective!).  He made several important points during his talk.  Here are a few considerations for green stormwater infrastructure that Dr. Pitt raised:

• For Florida, salt loading could potentially impact infiltration flow rate capacity in coastal areas.
• Modeling and design considerations will increase significantly.  Long term simulation needs to be completed to ensure capacity, among other considerations.  Are our models prepared for this reality?
• Contact times will need to be carefully considered.  Short circuiting can occur if projects are not properly designed.

Please take our poll (below) to let us know what you think is the most pressing issue related to the new stormwater rule and green stormwater infrastructure.  We’ll continue this dialogue next post with comments prompted by Justin Gregory’s Presentation.  Many thanks to Dr. Pitt for his timely and informative presentation.  Please subscribe to the FWEA blog to receive notification when the next speaker synopsis is posted.

Panelists include: Dr. Robert Pitt (University of Alabama), Akin Owosina (SFWMD), Jim Hunt (City of Orlando), Jeff Herr (Brown & Caldwell),  and Mike Schmidt (CDM)

You can register for the conference by clicking HERE or visit our official conference page by clicking HERE.

Dr. Pitt received a Distinguished Service Citation from the University of Wisconsin, was a member of the project team that received a first place national award for a combined sewer project from the Water Environment Federation, and has received several outstanding teacher and volunteer service awards. He is a registered Engineer and a Board Certified Environmental Engineer of the American Academy of Environmental Engineers and a Diplomate, American Academy of Water Resources Engineers. He has also served on numerous professional committees in the U.S. and abroad, including:

• National Research Council, National Academy of Science, Committee on Reducing Stormwater Discharge Contributions to Water Pollution. 2006 – 2009.
• U.S. Environmental Protection Agency, Science Advisory Board, Homeland Security Advisory Committee. 2005 – present.
• Monash University, Melbourne, Australia, Chair, External Review Team for Facility for Advancing Water Biofiltration. 2007.
• California Water Resources Board, Setting Numeric Limits for Stormwater Discharges. 2005 – 2006.
• State of Washington, Office of Salmon Recovery, Independent Science Panel, 2003 – 2004.
• US EPA, Experts Panel for the 2003 Report to Congress on Combined Sewer Overflows and Sanitary Sewer Overflows, Public Health Effects. 2002 – 2003.

Please plan to join us for the conference and hear more from Dr. Pitt.  You can register for the conference by clicking HERE or visit our official conference page by clicking HERE.