Table 6. Number of <strong>Pesticides</strong> with Positive Detections in <strong>Texas</strong> Surface <strong>Water</strong>s, 1984 - 1997Pesticide No. of Samples* No. Above DetectionLimit **% of Samples AboveDetection LimitEndosulfan 70 1 1%Heptachlor Epoxide 153 1
section of a segment was considered as impaired <strong>and</strong> unable to fully support the aquatic life use. In 1996,there were 780 miles of streams <strong>and</strong> rivers which did not meet the aquatic life use. About 55% of thistotal did not meet the aquatic life use due to elevated toxics; however, only two segments did not meet theaquatic life use due to pesticides (diazinon in Medina River <strong>and</strong> Salado Creek). 22 In addition, two lakes --Lake Houston <strong>and</strong> Caddo Lake-- <strong>and</strong> one bay -- Corpus Christi Inner Harbor -- did not meet their aquaticlife use due to elevated toxics in the water. Only Lake Houston was impacted by pesticides; again,diazinon was the problem (Table 8). The Upper San Antonio River has also exceeded the aquatic lifecriteria <strong>for</strong> diazinon at times <strong>and</strong> is on TNRCC’s 1998 303(d) list of impaired water bodies, in partbecause of these elevated levels. 23Table 8. Segments Which Did Not Meet the Aquatic Life Use Due to Elevated Pesticide Levels in Ambient<strong>Water</strong>, Based on 1990-1994 Data from SWQMP StationsSegment Number <strong>Water</strong> Body Type Pollutant1002 Lake Houston Lake Diazinon (C)1903 Medina Creek below Stream Diazinon (A, C)Medina DiversionReservoir1910 Salado Creek Stream Diazinon (A, C)1911 Upper San Antonio RiverDiazinon (A,C)RiverNotes: C=Chronic Criteria; A=Acute Criteria.Source: <strong>Texas</strong> Natural Resource Conservation Commission, Draft State of <strong>Texas</strong> 1998 303(d) List, March 13, 1998<strong>and</strong> <strong>Texas</strong> Natural Resource Conservation Commission, <strong>Texas</strong> Natural Resource Conservation Commission, TheState of <strong>Texas</strong> <strong>Water</strong> <strong>Quality</strong> Inventory -- 1996, Volume 1 (Austin: TNRCC, 1996), 217.Approximately 228 miles of monitored streams <strong>and</strong> rivers did not support their designated fishconsumption use, based on advisories or bans issued by the <strong>Texas</strong> Department of Health. About 170 ofthese miles had fish consumption bans due to high levels of pesticides in fish tissue, mostly chlordane,DDE (a breakdown component of DDT) <strong>and</strong> toxaphene, all of which have banned <strong>for</strong> use, but are highlypersistent in the environment. 24 In addition, four reservoirs were closed to fishing because of the presenceof pesticides or pesticide by-products in fish tissue. A full list can be found in Table 11.For the water quality inventory, TNRCC also reviewed ten years of data (1984-1994) to identify segmentsin which elevated levels of toxics in sediment or fish tissue might be a concern, even if the overall usewas supported. If more than 25% of the samples <strong>for</strong> a chemical were above screening levels, the segmentwas listed as a “segment of concern.” TNRCC identified 50 out of 222 monitored stream <strong>and</strong> riversegments, encompassing 1,028 miles; 31 out of 99 monitored reservoirs; <strong>and</strong> 18 out of 44 monitored baysegments with sediments which contained elevated levels of metals or organics. 25 Ten of these river <strong>and</strong>stream segments <strong>and</strong> two of the reservoirs had elevated levels of pesticides in the sediment (Table 9).22 <strong>Texas</strong> Natural Resource Conservation Commission, The State of <strong>Texas</strong> <strong>Water</strong> <strong>Quality</strong> Inventory -- 1996, Volume 1 (Austin:TNRCC, 1996), p. 217.23 <strong>Texas</strong> Natural Resource Conservation Commission, Draft State of <strong>Texas</strong> 1998 303(d) List, March 13, 1998.24 <strong>Texas</strong> Natural Resource Conservation Commission, The State of <strong>Texas</strong> <strong>Water</strong> <strong>Quality</strong> Inventory -- 1996, Volume 1 (Austin:TNRCC, 1996), 219-221.25 Ibid, 187.10
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