Master Plan Development - City of Boca Raton

City of Boca Raton Regulatory Information SummaryMS4 NPDES Permit ProgramAs described in Rule 62-303, F.A.C., water quality sample values in exceedence of the applicable WQStandards are the primary tool for the assessment of water body impairments.Values exceeding the WQ Standard for pH are those less than 6.5 or greater than 8.5. Exceedence of theStandard for dissolved oxygen occurs at all values below 5.0 mg/L. Turbidity exceedences occur at allvalues above 29.0 nephelometric turbidity units (“NTU”). Background turbidity is conservativelyassumed to be zero. The WQ Standard exceedence limits for fecal coliform and arsenic are 800 cfu/100mL and 0.05 mg/L, respectively. This WQ Standard for arsenic applies only to Class I and Class IIIfreshwater systems. There is no WQ Standard for arsenic in marine systems.For Class I and Class III freshwater, exceedence limits for heavy metals (cadmium, copper, lead, andzinc) are based on a logarithmic function of the total hardness. In cases where a total hardness was notmeasured or was below the limits of detection, an exceedence limit was not calculated. For marinewaters, the limits for heavy metals are constant and do not depend on the total hardness. Cadmium,copper, lead, and zinc exceed the surface WQ Standards at values above 0.0093 mg/L, 0.0029 mg/L,0.0056 mg/L, and 0.086 mg/L respectively in marine waters.Exceedence limits for chlorophyll-a (corrected for pheophytin) are determined by the annual mean of thesamples taken at a given site, per the Impaired Waters Rule. In freshwater systems, the required annualmean is exceeded if the average of all sample values is greater than 20 mg/m 3 . In marine systems,exceedences occur when the average value of all sampling events is greater than 11.0 mg/m 3 . In lieu ofnumeric limits for nutrients, chlorophyll-a measurements are used as an indicator of elevated nitrogen anphosphorous levels.Copper limits are related to total hardness in freshwater systems but are constant in marine systems.Limits for copper in freshwater systems typically vary within the range of 0.015 to 0.025 mg/L, an orderof magnitude greater than that allowed by the 0.0029 mg/L limit applied to marine systems. Copperlevels which may remain relatively constant from west to east in the freshwater watersheds will result in agreater occurrence of exceedences in the marine watershed due to the freshwater inflows to the marinewatersheds and discrepancy in the value of the limits on which the determination of impairment is based.Review of the water quality monitoring results from previous years has revealed that the highestoccurrence of exceedences appears for the following five parameters:Dissolved Oxygen (w/ temperature)Total NitrogenTotal PhosphorusChlorophyll-a (corrected for pheophytin)CopperL:\boca\bocaswmp\A6016.02\Final Task 2 Report - 1-07-08\r01acjh.docPage 16MOCK•ROOS