ELULS.orgThe Environmental and Land Use Law Section of The Florida Bar
Section Reporter

March 2007

ARTICLES  
     

ELULS.org  Soil and Groundwater Target Levels Tied at the Hip
  Richard Pryor

      

The Soil Cleanup Target Levels (SCTLs) listed in Rule 62-777, FAC, are generally the referenced cleanup goals when dealing with a contaminated property in Florida. The Petroleum Cleanup Rule, the Bownfields Rule, the Dry Cleaning Rule and most recently, the Contaminated Site Cleanup Rule, all refer to these target levels. The SCTL’s are identified for two primary categories: direct exposure and leachability. Direct exposure SCTLs are designed to protect humans from exposure in a residential or commercial setting. There are four subcategories of leachability SCTL’s that are designed to protect: groundwater, fresh surface water bodies, marine surface water bodies and groundwater of poor quality. The leachability criteria that was determined to be protective of groundwater quality is the subcategory that is referred to most often when conducting site assessments and cleanups. In general, soil sampling results have to meet the more stringent of the human exposure criteria and the leachability criteria in order to comply with the SCTLs. If these two primary categories are compared, the direct exposure SCTLs are generally much higher than the leachability SCTLs, often ranging many thousand fold higher. Therefore, the leachability SCTL becomes the defacto cleanup target level. One major exception is arsenic. Generally, the direct exposure SCTL for arsenic is more stringent than the leachability SCTL.

When the contaminants are organics, you may be able to get some relief from compliance with the leachability SCTLs by re-calculating expected leachate concentrations, based on site-specific soil properties. Because of the more complex relationships between inorganics and soil, recalculating a target level for soils impacted with inorganics is not typically an option. Instead, results from a Synthetic Precipitation Leach Procedure (SPLP) analysis can be used as an alternative to the listed leachability concentration for inorganics. The results for the leachate from the SPLP analysis must be below the respective Groundwater Cleanup Target Level (GCTL).

The SPLP analysis is similar to the toxicity characteristic leaching procedure (TCLP), which is used to determine if a waste is hazardous for the toxicity characteristic. Twenty parts of an acidic water (more acidic than that used in a TCLP analysis) are leached through the sample. The leachate concentration is measured in mg/l (ppm) and compared to the GCTL. The method actually provides a 20-fold dilution attenuation factor for metals, like the 20-fold attenuation factor allowed in the alternative leachability equations for organics. If, for example, 100% of the metal content from a 0.2 mg/kg (ppm) sample leached, the leachate concentration would be 0.010 mg/l. Although the relationship between inorganics and soils is complex, the more practical ratio, from experience, appears to be in the range of 100-1000. If a soil’s metals concentration, measured in mg/kg, is greater than 1000 times the GCTL, measured in mg/l, there is a good chance that the results from a SPLP analysis will exceed the GCTL.

An SPLP analysis may be the only option for a number of metals, such as lead, iron, manganese and zinc, to determine whether the leachability SCTLs has been exceeded. For these metals, in particular, the allowable direct exposure SCTL when compared with the GCTL, is relatively high. For a residential use, the ratio for lead is 27,000; for iron, 93,000; for manganese, 70,000; and for zinc, 5,200. Therefore, for a site that is impacted with theses metals, the applicable SCTL will likely be much lower than the direct exposure SCTL, which is typical for most contaminants listed in Rule 62-777, FAC.

Under the rules cited above, the ideal outcome, when conducting a site or cleanup, is that the site meets the criteria for No Further Action without institutional or engineering controls. This is often the only option when dealing with residential property or property that has to meet residential SCTLs, such as public right-of-way, park or playing field. This is when the leachability SCTLs are the most onerous. Although there are provisions in the rules for averaging soil results and comparing those with the direct exposure SCTLs, the rule provides no relief for averaging leachability results. For example, if one soil sample, within a 50 foot soil column, on a 10 acre property is above the leachability target level and the goal is No Further Action without controls, the associated soil may require remediation in order to achieve that goal. According to language of the Contaminated Site Cleanup Rule (Rule 62-780, FAC), the only relief is “[f]or soil that is and has been exposed to the elements (i.e., open ground, not covered by impermeable or semi-permeable cover) and subject to infiltration throughout the entire unsaturated zone for a minimum of two years [and] it has been subsequently demonstrated to the Department by a minimum of one year of groundwater monitoring data that contaminants will not leach into the groundwater at concentrations that exceed the appropriate groundwater CTLs pursuant to paragraph 62-780.680(1)(c), F.A.C., and, if applicable, the appropriate surface water CTLs pursuant to paragraph 62-780.680(1)(d), F.A.C.” But even this option would likely require an institutional control to ensure that soils that exceed leachability target levels are not moved to a more susceptible site.

Soils that exceed the leachability SCTLs may be left in place if institutional and engineering controls are an acceptable option. These soils would to have an impervious cover placed on top of them to protect the soils from infiltration. A deed restriction must to be recorded to ensure the upkeep of the cover and groundwater would have to monitored for at least one year, for potential groundwater exceedances.

Leachability SCTLs are generally a lot lower than the direct exposure SCTLs. The leachability SCTLs, as opposed to the direct exposure SCTLs, often drive the soil assessment and cleanup efforts because of the requirement to cleanup to the most stringent criteria. For a No Further Action without institutional or engineering controls, there are not really any risk based provisions in the cleanup rules that allow soils, which have concentrations above leachability target levels, to remain on site. An institutional control would be required if groundwater was shown to be unimpacted and soils above leachability SCTLs remained on site. If an engineering control was an option, an impermeable cap would have to extend over the entire area that was shown to have soils exceeding the leachability criteria.

Richard Pryor is a Professional Geologist with Environmental Engineering Consultants, Inc. in Tampa, Florida

 

 

ELULS.orgCopyright © 2010, The Environmental and Land Use Law Section of The Florida Bar