Florida DEP Workshops on Numeric Nutrient Criteria for Estuaries and Coastal Waterbodies

On April 15, 2013, the Florida Department of Environmental Protection (FDEP) held its first of three workshops to discuss proposed numeric nutrient criteria (NNC) for regional estuaries and statewide coastal waterbodies.  The first workshop was held in West Palm Beach, with subsequent workshops held in Jacksonville (April 16) and Tallahassee (April 17).  The estuaries discussed at the West Palm Beach workshop included the Loxahatchee River and Lake Worth Lagoon.  In Jacksonville, FDEP discussed the estuaries of the Halifax River, the Guana/Tolomato/Matanzas (GTM) Rivers, and the Nassau River. In Tallahassee, FDEP discussed the estuaries covering the Suwannee River, Waccasassa River, and Withlacoochee River, and the Springs Coast (Crystal River to Anclote River).

Summary of Rulemaking

Daryll Joyner started the workshop by providing a background of the NNC rulemaking effort.  He gave a brief history of the NNC criteria development by the U.S. Environmental Protection Agency (EPA) and the FDEP.  Daryll also described the proposed rule changes through this current rulemaking.  For estuaries, the proposed rule will set numeric limits for phosphorus (TP) and nitrogen (TN), as well as chlorophyll-a.  For the state’s coastal waters, FDEP is proposing numeric limits for chlorophyll-a only.  Mr. Joyner explained that there was not sufficient data to establish NNC for TN and TP in the coastal waters.  Daryll also explained that satellite imagery was being utilized to determine current chlorophyll

Importantly, the new rules will revoke a section of Rule 62-302.531(9), which Daryll referred to as the “poison pill”.  That section provided that the FDEP rules would not go into effect until EPA: 1) approves the FDEP rules, 2) formally rescinds the EPA criteria, and 3) expressly states that the FDEP NNC satisfies the 2009 EPA determination letter that prompted the EPA rulemaking.

Daryll stated that, pursuant to the federal court Consent Decree, the FDEP rules must be approved, with state legislative ratification, by September 30, 2013.

Comments to the published draft technical support documents for the estuaries must be submitted by May 1, 2013.  The Florida Environmental Regulatory Commission (ERC) will be briefed on the proposed rules at its May 16, 2013, meeting.

Generally, the comments made to Mr. Joyner concerned the appropriateness of setting chlorophyll-a criteria for coastal waterbodies when it is known that chlorophyll-a is not an indication of nutrient over-enrichment.  According to the comments, the chlorophyll-a criteria will not improve the water quality of the coastal water segments.

Biological Targets

Russ Frydenburg presented the issue of biological targets for the NNC.  Mr. Frydenburg described that the FDEP utilized a reference condition approach, based on the weight of evidence.  FDEP looked back to water quality data as far back as 1970, and utilized EPA data on submerged aquatic vegetation coverage and water depth data from the 1940s.  Based on this data, and looking at future years, FDEP established numeric limits. The criteria was established by focusing of three primary conditions:

  • Low Dissolved Oxygen – minimum allowable 4.0 mg/L or 42% saturation
  • Reduced water clarity – 20% seagrass bed depth light penetration using Secchi disk at deep edge of seagrass bed
  • Chlorophyll-a – < 20ug/L in 90% of yearly observations

However, Mr. Frydenburg acknowledged that certain water body IDs (WBIDs) were not nutrient responsive, and requested feedback and additional data on these segments.

Statistical Approach

Next, Ken Weaver went over the statistical approach utilized in development of the NNC.  He explained that the approach utilized was approved by the Florida ERC, the Administrative Law Judge in the rule challenge to the freshwater NNC, and the EPA.  If there existing nine or more years of data on a particular waterbody segment, then the numeric criteria was set at the 80% prediction limit for success.  If there was less than nine years of data, then the 90% prediction limits was utilized based on the individual sample limits.

Comments to Mr. Weaver were focused on the issue of salinity changes and that the data points failed to address operational issues related to canal and system water management.  Salinity changes occur on an hourly or daily basis, and the data points fail to reflect this. Further, the commenters stated the baseline condition assumption were already impaired, and the error of doing so.

Coastal Criteria

Russ Frydenburg presented the coastal NNC, which only proposed criteria for chlorophyll-a.  First, the FDEP utilized three sets of data sources – chlorophyll-a field observations, satellite remote sensing data, and K. brevis data to flag bloom events. The various models confirmed that satellite remote sensing assessments can accurately measure chlorophyll-a in waterbodies.  Utilizing the computer models and data points, FDEP set NNC for coastal waterbodies so as to not results in a single exceedance in a three-year period.

The criteria can be found on page 27 of EPA’s documents here.

The comments again focused on the appropriateness of utilizing chlorophyll-a when it is not a responsive variable for nutrient issues.  Mr. Frydenburg responded that this was an interim proposal and more studies would be undertaken to analyze the issue of TN and TP specifically in coastal segments.

Also, it was raised as an issue of whether it is appropriate to set criteria for the Atlantic Ocean when a significant majority of the data points were from the Gulf of Mexico.  Russ responded that the water currents bring the ocean water into the Gulf, but that FDEP would accept additional data and revise the criteria if needed.

Loxahatchee River and Lake Worth Lagoon Estuaries

Kara Cox presented the estuary NNC for the Loxahatchee River and Lake Worth Lagoon.  In the Loxahatchee River, the estuary was broken up into three segments – the lower segment, which is the marine segment; the open water segment, which includes the north and southwest forks of the river, and the upper segment, which includes the northwest fork.  For the Lake Worth Lagoon, the north, central and south segments were similar to those proposed by EPA, but with minor modifications. The north segment has the Flagler Memorial Bridge as its southern boundary

Ms. Cox explained that FDEP conducted a statistical analysis of the TN, TP, and chlorophyll-a data associated with the reference conditions period, and established criteria for TN, TP, and chlorophyll a.  The NNC were established utilizing the biological targets described above.

Comments again were focused on whether the assumed baseline was already impaired. Also, public comment questioned the effectiveness of the NNC when the canals that discharge into the estuaries have water quality issues.

The following represents the NNC for the Lake Worth Lagoon and Loxahatchee River estuaries:

Upper Lake Worth Lagoon

  • TP (mg/L) 0.038
  • TN (mg/L) 0.54
  • Chl a (µg/) 7.6 (10% of samples exceedance)

Central Lake Worth Lagoon

  • TP (mg/L) 0.098
  • TN (mg/L) 1.88
  • Chl a (µg/) (corrected) 10.1

Southern Lake Worth Lagoon

  • TP (mg/L) 0.061
  • TN (mg/L) 0.61
  • Chl a (µg/) (corrected) 10.8

Lower Loxahatchee

  • TP (mg/L) 0.023
  • TN (mg/L) 0.65
  • Chl a (µg/) (corrected) 2.1

Middle Loxahatchee

  • TP (mg/L) 0.046
  • TN (mg/L) 0.94
  • Chl a (µg/) (uncorrected) 5.2

Upper Loxahatchee

  • TP (mg/L) 0.075
  • TN (mg/L) 1.26
  • Chl a (µg/) (uncorrected) 7.1

Information concerning the NNC proposed for the remaining estuaries can be found through the links below:

Halifax River 

GTM Rivers

Nassau River 

Suwannee Sound, Waccasassa River, and Withlacoochee River

Springs Coast

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Filed under Florida DEP, Numeric Nutrient Criteria, Rulemaking, U.S. EPA, Water Quality

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