Special Protections Meet Real Data: Quandaries for Compliance
In 2012 the California State Water Board adopted Special Protections to ensure the protection of marine biological resources in coastal areas designated as Areas of Special Biological Significance by enforcing the prohibition against discharges of waste. These were designated in the 1970s, mostly without consideration of ambient water quality. The Special Protections established the compliance threshold in ocean waters at ASBS stormwater discharges at the 85th percentile of all reference receiving water samples collected at the mouths of streams that do not have water quality impairments and that have human development on <5% of their watershed area. Determination of exceedances requires higher ASBS receiving water values compared to the 85th percentile threshold, storm receiving water values being greater than pre-storm values. If corrective actions do not eliminate exceedances of the 85th percentile threshold, ASBS receiving water concentrations must be reduced below California Ocean Plan Instantaneous Maximum concentrations.
The Central California Regional ASBS Monitoring Program has sampled storms over a 2-year period. Data from the first year (2013–2014) were analyzed with a variety of statistical and graphical methods to explore their implications for determining exceedances under the Special Protections. The following questions were specifically addressed:
1) Are there spatial patterns in contaminants or exceedances among reference sites or ASBS discharges?
2) How do exceedances compare to reference values?
3) Are exceedances caused by regulated stormwater discharges?
Results of these analyses suggested conditions outside the control of stormwater dischargers, which will make it difficult to meet requirements of the Special Protections, such as:
1) There were differences among sites in ambient concentrations of constituents exceeding the 85th percentile threshold, which appear to be related to natural phenomena.
2) There were frequent exceedances of 85th percentile thresholds in pre-storm samples that suggest some ASBS might never comply with the 85th percentile threshold.
3) There were cases of exceedances for contaminants whose concentrations in ASBS storm receiving water samples fall within the range of concentrations at reference sites and for which storm runoff does not appear to be a significant source. Moreover, there were exceedances observed in ASBS storm receiving water for constituents whose concentrations did not differ significantly between ASBS and reference samples.
4) Differences in receiving water concentrations of several constituents were significantly correlated with estimated stormwater loads, but many were not.
5) Compliance requirements that are based upon Ocean Plan water quality objectives are not universally applicable because not all constituents that are required by the Special Protections have applicable objectives.
6) Limited access to some reference sites during large storms has potentially reduced the ranges of reference values for calculation of 85th percentile thresholds.
7) High detection limits of some constituents related to sampling methods resulted in automatic exceedances for any detection in ASBS storm receiving waters.
Notwithstanding the issues described above, data from 2013–2014 suggest the following conclusions:
1) Some ASBS have higher rates of exceedances than others for constituents that are most clearly associated with human activities.
2) Geological processes could be responsible for increased concentrations of most trace metals in ASBS storm receiving waters.
3) Incidents of toxicity in ASBS discharges with corresponding toxicity in storm receiving waters deserve further attention to ensure remediation.