Ü Miles HSC / BUFFALO BAYOU - SEGMENT 1007 «225. !. Monitoring Station "/ USGS Flow Station ^_ Texas Stream Team

Transcription

1 95 40'0"W HSC / BUFFALO BAYOU - SEGMENT '0"W 95 30'0"W 95 25'0"W 95 20'0"W 95 15'0"W '0"W eek 29 50'0"N 29 55'0"N 29 35'0"N 29 40'0"N 29 45'0"N 4 Watershed Boundary!. Monitoring Station "/ USGS Flow Station ^_ Texas Stream Team # Wastewater Outfall Major Road Waterway Dinner Creek County Boundary City, Town or Place Land Cover (2008) Bare Mission Bend Four Corners Bullhead Bayou Langham Creek High Intensity Developed Low Intensity Developed Open Space Developed Cultivated Grassland/Shrub Forest Woody Wetland Herbaceous Wetland Open Water Number of Outfalls: 145 Total Population ,151, (Proj.) 1,452, (Proj.) 1,686, '0"W Assessment Stations for the Texas Integrated Report Use Impairment ID Bacteria 11128, 11129, 11133, 11135, 11138, 11139, 11140, 11169, 11271, 11283, 11287, 11292, 11296, 11298, 11306, 11309, 15841, 15848, Jersey Village15849, 15850, 15851, 15852, 15853, 15854, , 15859, , 15869, 15873, 15875, 15876, 15877, 16479, 16620, 16649, 16650, 16651, 16652, 16653, 16655, 16656, 16657, 16658, 16659, 16661, 17976, 18362, 18561, 18689, 18690, 18691, 18692, PCBs & Dioxin 11128, , 11271, 11284, 11287, 11292, , 11299, 11300, 11302, 11304, 11306, 15841, 18362, Dissolved Oxygen 16650, 16651, 16657, 16658, Toxicity in Sediment Turkey Creek Turkey Creek Rolling Fork Stafford Sugar Land 95 35'0"W '0"W Missouri City Bellaire HARRIS COUNTY Halls Bayou Ü Miles Area of Impairment Bacteria Kilometers Bacteria, Dissolved Oxygen Bacteria, PCBs & Dioxin, Pesticides in Edible Tissue Bacteria, PCBs & Dioxin, Pesticides in Edible Tissue, Sediment Toxicity PCBs & Dioxin, Pesticides in Edible Tissue Halls Bayou Jacinto City Houston South Houston '0"W Pearland HARDY TOLL RD HARRIS COUNTY BRAZORIA COUNTY 95 20'0"W Hickory Slou gh Galena Park '0"W Location Map Big Gulch 10 Carpenters Bayou «225 D 95 10'0"W 29 45'0"N 29 50'0"N 29 55'0"N 29 35'0"N 29 40'0"N

2 Segment Number: 1007 Name: Houston Ship Channel / Buffalo Bayou Tidal Length: 34.5 miles Watershed Area: 179 square miles Designated Uses: Navigation; Industrial Water Supply Number of Active Monitoring Stations: 59 Texas Stream Team Monitors: 5 Permitted Outfalls: 189 From a point immediately upstream of the confluence with Greens Bayou in Harris County to a point 100 meters (110 yards) upstream of US 59 in Harris County, including tidal portion of tributaries Sub Segment 1007A: Canal C 147 tributary of Sims Bayou Above Tidal (unclassified water body) From the Sims Bayou confluence upstream to a point 0.71 km (0.44 mi) east of Beltway 8. Sub Segment 1007B: Brays Bayou Above Tidal (unclassified water body) From a point 11.5 km (7.1 mi) upstream of confluence with Houston Ship Channel up to SH 6 Sub Segment 1007C: Keegans Bayou Above Tidal (unclassified water body) From the Brays Bayou confluence to the Harris County line Sub Segment 1007D: Sims Bayou Above Tidal (unclassified water body) From 11.0 km (6.8 mi) upstream of the Houston Ship Channel confluence to State Hwy 45 Description: Sub Segment 1007E: Willow Waterhole Bayou Above Tidal (unclassified water body) From the Brays Bayou confluence upstream to South Garden Street Sub Segment 1007F: Berry Bayou Above Tidal (unclassified water body) From a point 2.4 km (1.5 mi) upstream of the Sims Bayou confluence to SH 3 Sub Segment 1007G: Kuhlman Gully Above Tidal (unclassified water body) From Brays Bayou confluence to Atchison, Topeka and Santa Fe Railroad tracks Sub Segment 1007H: Pine Gully Above Tidal (unclassified water body) From the Sims Bayou confluence to 0.11 km (0.07 mi) east of Broadway Street Sub Segment 1007I: Plum Creek Above Tidal (unclassified water body) From the Sims Bayou confluence to Telephone Road in Harris County Sub Segment 1007K: Country Club Bayou Above Tidal (unclassified water body) From the Brays Bayou confluence to a point 0.43 km (0.27 mi) upstream of Polk Street

3 Sub Segment 1007L: Unnamed Tributary of Brays Bayou (unclassified water body) From the Brays Bayou confluence near Fondren Road to a point 0.37 km (0.60 mi) upstream in Harris County Sub Segment 1007M: Unnamed Non Tidal Tributary of Hunting Bayou (unclassified water body) From the Hunting Bayou confluence to 0,6 km (0.37 mi) upstream of Gellhorn Road Sub Segment 1007N: Unnamed Non Tidal Tributary of Sims Bayou (unclassified water body) From the Sims Bayou confluence, south of Airport Road to 1.1 km (0.68 mi) upstream of SH 288 Sub Segment 1007O: Unnamed Non Tidal Tributary of Buffalo Bayou (unclassified water body) From the Buffalo Bayou confluence to Clinton Drive Sub Segment 1007R: Hunting Bayou Above Tidal (unclassified water body) From the confluence with Hunting Bayou Tidal at IH 10 upstream to Loop 610 East Degree of Impairment and Overall Trends Segment ID Dissolved Oxygen Bacteria Nutrients PCBs/Dioxin Chlorophyll a Other A B C D E F G H I K L M N

4 1007O R S T U V 100 Indicates general improvement Indicates general degradation Numbers indicate percent of segment impaired FY 2011 Active Monitoring Stations Site ID Site Description Frequency Monitoring Entity Parameter Groups Hunting Bayou downstream of IH 10 Nine Times / Year COH / HHS Field, Conventional, Bacteria Hunting Bayou at N Loop East Nine Times / Year COH / HHS Field, Conventional, Bacteria Sims Bayou at Telephone Road / SH 35 Nine Times / Year COH / HHS Field, Conventional, Bacteria Sims Bayou at Cullen Blvd Nine Times / Year COH / HHS Field, Conventional, Bacteria, Chlorophyll a (Qrtrly) Sims Bayou at Hiram Clarke Rd Nine Times / Year COH / HHS Field, Conventional, Bacteria Brays Bayou at Almeda Road Nine Times / Year COH / HHS Field, Conventional, Bacteria Brays Bayou at South Main St Nine Times / Year COH / HHS Field, Conventional, Bacteria, Chlorophyll a (Qrtrly) Brays Bayou at South Gessner Nine Times / Year COH / HHS Field, Conventional, Bacteria Brays/Keegan Bayou at Roark Rd Nine Times / Year COH / HHS Field, Conventional, Bacteria Little Vince Bayou at North Main Street Nine Times / Year COH / HHS Field, Conventional, Bacteria Houston Ship Ch Washburn Tunnel Monthly HCPHES Field, Conventional, Bacteria HSC/Buffalo Bayou near FL 165 Quarterly TCEQ Field, Conventional, Bacteria, Chlorophyll a Houston Ship Channel / Buffalo Bayou at Quarterly TCEQ Field, Conventional, Bacteria, Chlorophyll a confluence with Sims Bayou Houston Ship Channel / Buffalo Bayou in Monthly HCPHES Field, Conventional, Bacteria, Chlorophyll a (Qrtrly) Turning Basin Houston Ship Channel / Buffalo Bayou in Quarterly TCEQ Field, Conventional, Bacteria, Chlorophyll a, Metals Turning Basin Houston Ship Channel / Buffalo Bayou in Twice / Year TCEQ Metals in Sediment Turning Basin Buffalo Bayou at Hirsch Road Quarterly TCEQ Field, Conventional, Bacteria, Chlorophyll a

5 11298 Hunting Bayou at Federal Road Nine Times / Year COH / HHS Field, Conventional, Bacteria Vince Bayou at HSC confluence Quarterly TCEQ Field, Conventional, Bacteria, Chlorophyll a, Metals Vince Bayou at HSC confluence Twice / Year TCEQ Metals in Sediment Vince Bayou at North Richey St Quarterly TCEQ Field, Conventional, Bacteria, Chlorophyll a Sims Bayou Tidal at Lawndale Nine Times / Year COH / HHS Field, Conventional, Bacteria, Chlorophyll a (Qrtrly) Sims Bayou Tidal at Lawndale Quarterly TCEQ Field, Conventional, Bacteria, Chlorophyll a Sims Bayou at Galveston Road Nine Times / Year COH / HHS Field, Conventional, Bacteria Brays Bayou Tidal at 75th St Nine Times / Year COH / HHS Field, Conventional, Bacteria, Chlorophyll a (Qrtrly) Brays Bayou Tidal at 75th St Quarterly TCEQ Field, Conventional, Bacteria, Chlorophyll a Brays Bayou at Scott St Nine Times / Year COH / HHS Field, Conventional, Bacteria Buffalo Bayou Tidal at Jensen Nine Times / Year COH / HHS Field, Conventional, Bacteria Brays Bayou at SH 6 Nine Times / Year COH / HHS Field, Conventional, Bacteria Brays Bayou at Dairy Ashford Nine Times / Year COH / HHS Field, Conventional, Bacteria Brays Bayou at Wilcrest Drive Nine Times / Year COH / HHS Field, Conventional, Bacteria Brays Bayou at Beechnut Street Nine Times / Year COH / HHS Field, Conventional, Bacteria Brays Bayou at Hillcroft St Nine Times / Year COH / HHS Field, Conventional, Bacteria Brays Bayou at S Rice Avenue Nine Times / Year COH / HHS Field, Conventional, Bacteria Brays Bayou at Stella Link Rd Nine Times / Year COH / HHS Field, Conventional, Bacteria Brays Bayou at Greenbriar St Nine Times / Year COH / HHS Field, Conventional, Bacteria Hunting Bayou at Jensen Drive Nine Times / Year COH / HHS Field, Conventional, Bacteria Hunting Bayou at Cavalcade St Nine Times / Year COH / HHS Field, Conventional, Bacteria Hunting Bayou at Cavalcade St Five Times/ Year COH/ HHS Flow, 24 Hour DO Hunting Bayou at Lockwood Dr Nine Times / Year COH / HHS Field, Conventional, Bacteria Sims Bayou at Almeda Road Nine Times / Year COH / HHS Field, Conventional, Bacteria Sims Bayou at M L King Jr Blvd Nine Times / Year COH / HHS Field, Conventional, Bacteria Sims Bayou at Swallow Street Nine Times / Year COH / HHS Field, Conventional, Bacteria Brays Bayou at South Wayside Nine Times / Year COH / HHS Field, Conventional, Bacteria HSC/Buffalo Bayou at Mayo Shell Rd Monthly HCPHES Field, Conventional, Bacteria Trib Of Buffalo Bayou at Clinton Nine Times / Year COH / HHS Field, Conventional, Bacteria Trib Of Buffalo Bayou at Clinton Five Times/ Year COH/ HHS Flow, 24 Hour DO Country Club Bayou at Wayside Nine Times / Year COH / HHS Field, Conventional, Bacteria Country Club Bayou at Hughes Nine Times / Year COH / HHS Field, Conventional, Bacteria Country Club Bayou at Hughes Five Times / Year COH/ HHS Flow, 24 Hour DO

6 16652 Willow Waterhole at McDermed Dr Nine Times / Year COH / HHS Field, Conventional, Bacteria Kuhlman Gully at Brock St Nine Times / Year COH / HHS Field, Conventional, Bacteria Trib of Brays Bayou at Dumfries Nine Times / Year COH / HHS Field, Conventional, Bacteria Trib of Sims Bayou at Dulcimer Nine Times / Year COH / HHS Field, Conventional, Bacteria Sims Bayou S Branch at Tiffany Nine Times / Year COH / HHS Field, Conventional, Bacteria Unnamed Tributary of Hunting Bayou Nine Times / Year COH / HHS Field, Conventional, Bacteria immediately upstream of John Ralston Road Plum Creek at Old Galveston Rd Nine Times / Year COH / HHS Field, Conventional, Bacteria Pine Gully at Old Galveston Rd Nine Times / Year COH / HHS Field, Conventional, Bacteria Berry Bayou at Ahrens Drive Nine Times / Year COH / HHS Field, Conventional, Bacteria Berry Bayou at South Richey Nine Times / Year COH / HHS Field, Conventional, Bacteria Sims Bayou at S Post Oak Rd Nine Times / Year COH / HHS Field, Conventional, Bacteria Hunting Bayou at Market St Quarterly TCEQ Field, Conventional, Bacteria, Chlorophyll a Trib Hunting Bayou at Minden Nine Times / Year COH / HHS Field, Conventional, Bacteria Bintliff Ditch at Bissonnet St Nine Times / Year COH / HHS Field, Conventional, Bacteria Mimosa Ditch at Newcastle Dr Nine Times / Year COH / HHS Field, Conventional, Bacteria Poor Farm Ditch at N Braeswood Nine Times / Year COH / HHS Field, Conventional, Bacteria Keegan's Bayou at Synott Road Nine Times / Year COH / HHS Field, Conventional, Bacteria Segment 1007 Standards Screening Levels Temperature ( C): 35 Ammonia (mg/l): 0.46 Dissolved Oxygen (24 Hr Average) (mg/l): 1.0 Nitrate N (mg/l): 1.10 Dissolved Oxygen (Absolute Minima) (mg/l): 1.0 Orthophosphate Phosphorus (mg/l): 0.46 ph (standard units): Total Phosphorus (mg/l): 0.66 Enterococci (MPN/100mL) (30 day geometric mean> 10 samples): 168 Chlorophyll a (µg/l): 21 Enterococci (MPN/100mL) (>10 samples in 30 day geo. mean, single sample max): 500 Enterococci (MPN/100mL) (< 10 samples in 30 day geo. mean, 10% samples max): 500

7 Water Quality Issues Summary Issue 2008 Assessment Draft 2010 Assessment Affected Area Possible Causes/Influences / Concerns Voiced by Stakeholders Possible Solutions / Actions To Be Taken Elevated Levels of Bacteria causing impairment for contact recreation and general use I I Entire segment except 1007D_04 for contact recreation use and 1007_01 for general use WWTP non compliance, overflows, collection system by passes Small, privately run WWTP Developments with septic tanks Rapid urbanization and increased impervious cover Constructed storm water controls failing Direct and dry weather discharges Waste haulers illegal discharges/improper disposal Improper or no pet waste disposal Animal waste from hobby farms and riding stables Increase monitoring requirements for selfreporting Impose new or stricter bacteria limits than those designated by TCEQ Require all systems to develop and implement a utility asset management program and protect against power outages at lift stations or provide alternative power supplies during outages Regionalize wastewater treatment to minimize number of small package plants and reduce OSSF dependency Require larger partials of land in developments platted to use OSSFs More public education regarding OSSF operations and maintenance More public education regarding pet waste disposal Improve storm water controls in new developments by adding bacteria reduction measures Improve compliance and enforcement of existing storm water quality permits to minimize contaminated runoff Improve construction oversight to minimize TSS discharges to waterways Implement stream fencing and alternative water supplies to keep livestock out of or away from waterways Promote and implement Water Quality

8 Low Dissolved Oxygen Concentrations Elevated Nutrients I I 1007_ H_ I_ K_ O_ R_04 C C Entire Segment Excessive nutrients and organic matter from WWTP effluent, sanitary sewer overflows, malfunctioning OSSFs, illegal disposal of grease trap waste, biodegradable solid waste such as grass clippings and pet waste Excessive nutrients and organic matter from agricultural production and related activities Vegetative canopy removed High temperatures discharges from industrial WWTPs WWTP effluent, sanitary sewer overflows, and malfunctioning OSSFs Agricultural runoff from row crops, fallow fields pastures, and animal operations Fertilizer runoff from urbanized properties such as landscaped areas, residential lawns, and sport fields Management Plans for individual agricultural properties Protect or install vegetative buffers along waterways Improve compliance and enforcement of existing storm water quality permits Improve operation and maintenance of existing WWTP and collection systems Regionalize wastewater treatment to minimize number of small package plants and reduce OSSFs dependency More public education regarding pet waste disposal More public education regarding disposal of household fats, oils, and grease More stringent OSSF maintenance and education Create and implement Water Quality Management Plans for individual agricultural properties Install and/or maintain riparian buffer areas between agricultural fields and waterways Conserve or plant canopy trees and habitat along waterways to maintain/create shade to cool water. Work with drainage districts and agencies to change practices of clear cutting waterways protect Monitor phosphorus levels at WWTFs to determine if controls are needed. Implement YardWise and Watersmart landscape practices Create and implement Water Quality Management Plans for individual agricultural properties

9 Dioxin/PCBs and pesticides found in edible tissue (Chlordane, dieldrin, and Heptachlor) Elevated Heavy Metals Iron in sediment I I 1007 Waste pit located along the San Jacinto River immediately upstream of I 10 bridge is now a National Priority List Superfund site managed by EPA Concentrated deposits outside boundaries of the waste pits Unknown industrial or urban sources Spill of pesticides in urbanized areas Spills from chemical manufacturing processes/ storage and transport along the channel Legacy pollutant in sediment C 1007_ _05 Dissolution from natural deposits Discharges from domestic, agricultural or industrial sources. Build up in pipelines, pressure tanks, water heaters and water softeners from industrial point sources Particles deposition and resuspension processes due to dredging processes or tidal movements Install and/or maintain riparian buffer areas between agricultural fields and waterways Encourage EPA and responsible parties to work together to remediate Superfund site Remove or contain contamination from locations already identified Encourage additional testing to locate all unknown sources/deposits Increase monitoring and enforcement efforts to identify and control industrial point sources Encourage additional testing to locate all unknown sources/deposits Segment Discussion Watershed Characteristics: This very urbanized watershed includes 14 miles of the Houston Ship Channel (HSC) but more than 70 miles of tidal and non tidal tributary streams. The Houston Ship Channel (HSC) is lined by heavy industrial complexes located in the City of Pasadena, Galena Park, Houston, and unincorporated Harris County. Numerous permitted wastewater and storm water discharges are located throughout the watershed. The HSC supports heavy boat and barge traffic from Greens Bayou upstream to the turning basin on a continual basis. The Cities of Pasadena and South Houston are drained primarily by Vince Bayou, Little Vince Bayou and Berry Bayou, while the two largest tributaries Sims and Brays Bayous drain the City of Houston and a host of smaller cities and unincorporated communities to the west. About half of the watershed supports low intensity residential and commercial development while the rest is a

10 mixture of high intensity development, grasslands and pockets of forested areas. Not all areas are serviced by sanitary sewer despite the numerous wastewater collection and treatment systems located throughout the watershed. Water Quality Issues: None of the four uses designated to Houston Ship Channel/Buffalo Bayou Tidal aquatic, recreation, fish consumption, and general is fully supported. All the Assessment Units (AU) located on the classified portion of the channel are listed as impaired for fish consumption due to high levels of dioxin/pcbs and other toxic chemicals present in pesticides (Chlordane, Dieldrin, and Heptachlor). Due to the high levels found in this segment, the Texas Department of State Health Services has issued a Limited Consumption Fish Advisory for this water body. The impairment for this designated use in listed in both the Draft 2010 Texas Integrated Report (IR) and the 2008 IR. None of the tributaries to 1007 support their designated recreation use because of elevated level of bacteria. E. coli levels exceeded the geometric mean criteria (126 MPN/100mL) reporting values from MPN/100mL to MPN/100mL. Additionally, more of the 50% of the samples at each site exceeded the single grab criteria of 394 MPN/100mL. E. coli was listed as a cause of impairment in the 2008 report as well. Levels of Dissolved Oxygen (DO) lower than the standard for DO grab minimum (1.0 mg/ml) were a cause of impairment for the AUs 1007H_01, 1007I_01, 1007K_01, 1007O_01 and 1007R_01. In these AUs, more of the 18% of samples evaluated were below the standard. The AUs 1007K_01 and 1007O_01 were listed as well in the 2008 report as impaired because their depressed DO level. DO levels lower than the standards for screening level and grab screening level in the AU 1007G_01, 1007H_01, 1007I_01, 1007K_01, 1007M_01, 1007N_01, 1007O_01, 1007R_02, and 1007R_04 were listed as cause of concern in both Draft 2010 and 2008 IRs. Additionally, two AUs (1007_01, and 1007_05) were listed as a concern in the 2010 Draft IR due to high levels of iron. 100% of the samples evaluated at those AUs exceeded the screening standard level. Four nutrients Ammonia nitrogen (ammonia), nitrate nitrogen (nitrate), orthophosphate phosphorous (OP) and total phosphorous (TP) were found to be higher than the screening level in 13 out of 33 AUs. Among the four nutrients, ammonia was the most common cause of concern; more than 32% of the samples taken these AUs exceeded the screening level of 0.46mg/L. From the 13 AUs listed in the 2010 Draft IR, only one (1007D_02) was listed in the 2008 IR. Special Studies/Projects: This segment has been included in three TMDL projects: the Houston Metro TMDL for bacteria, the Houston Ship Channel and Upper Galveston Bay TMDL for PCBs in fish tissue and the Houston Ship Channel TMDL for Dioxin. This segment is part of the geographic area for the Bacteria Implementation Plan, which is currently being finalized. For more information, please refer to the detailed discussions located at the beginning of the water quality section of the 2011 Basin Summary Report regarding dioxin and PCB contamination and the BIG. Trends: A succinct, unambiguous summary of trends in the tidal section of the Houston Ship Channel / Buffalo Bayou tidal watershed is difficult to produce, due to the variety of point and non point sources of pollutants, as well as the sheer number of monitoring stations within the watershed. Trends identified through regression analysis of pooled data from all stations in the watershed, even when differentiating between classified and unclassified portions, are meaningful only where supported by the station level data. However, this approach provides a useful entry point to a more detailed examination of trends within the watershed. Analysis of station level data revealed trends in each of the parameters selected for analysis at one or more stations, but this discussion will focus on water

11 quality parameters that are associated with impairments and concerns listed in the 2010 Draft IR. The most common water quality problem in the Houston Galveston region is exceedance of bacteria water quality standards. Thirty one of the 33 assessment units in this watershed were listed in the 2010 IR as either impaired for bacteria or of concern (1007_02). Enterococci are the indicator bacteria in most of the assessment units in the classified portion of the water body. Significant trends were found when data from stations in this portion of the watershed were pooled and at five of the fifteen monitoring stations. In all cases, enterococci are trending downward over time although exceedances of the water quality standard remain frequent and have hovered near fifty percent the past three years. A plot of the annual geometric mean for all data from stations located in the classified section of the segment appears below. A similar downward trend in single sample results was seen at seven of the 15 stations a in portion of the segment. Regression of the annual geometric mean of the year, which is less sensitive to extreme values, at the station level suggested statistically significant downward trends at four of the stations. A significant downward trend for E. coli density was found at station in assessment unit 1107_04 through analysis of both single sample results and annual geometric means. However, it is unknown why E. coli was selected as the indicator bacterium in the middle reaches of a tidal segment, and inferences based on this trend should be made with caution. Review of the segment and assessment unit descriptions suggests that should be placed in an assessment unit farther upstream than 1007_04, which might explain the selection of E. coli as the indicator bacterium. E. coli is the indicator bacterium for seven stations in the un classified region of the segment, and the analysis of pooled geometric means did not suggest an overall trend. A plot of individual E. coli results for station follows. The indicator for all unclassified areas is E. coli and it is trending downward at 20 of 44 stations. The analysis revealed no statistically significant upward trends for either bacterium. It should be noted that unusually high bacteria densities were reported at many stations in 2002 and these may have introduced a bias in trend analysis based on the natural logs of individual sample results. Nutrients (nitrogen and phosphorus in various forms) are a concern in watersheds throughout the state as they are associated with algae blooms that threaten aquatic life and human health. Chlorophyll a can be considered one indicator of the impact of excessive nutrient loading in waterways. The concentration of chlorophyll a in the watershed is trending higher in both classified and unclassified waterways in the segment. Samples are collected at nine stations in the classified portion of the watershed and regression analysis revealed a statistically significant upward trend at six of them. In several cases, most of the data is at or below the detection level and recent higher values may have biased the regression. Statistically significant trends for nutrient concentrations were found at only one of these six stations. However, the absence of a trend does not indicate the absence of a problem and excursions of nutrient screening levels for nitratenitrogen and total phosphorus (TP) range between 20% and 90% of all samples collected at these six stations over the period of record. Conversely, the existence of a trend does not necessarily indicate a problem. The chlorophyll a screening level has rarely been exceeded in this watershed despite the high nutrient loading. It is plausible that high nutrient levels nourish the bacterial population in the watershed but it is unlikely that algae can thrive in the Houston Ship Channel and the nutrients may be facilitating algal growth in the bays. It has been suggested that the reduction of freshwater inflows into the bays is accompanied by a reduced supply of nutrients posing a threat to estuarine ecosystems. Plots of chlorophyll a concentrations at station 11292, located in the most upstream assessment unit, along with plots of the nitrate nitrogen and TP concentrations in a sample collected at the same time appear below. Upstreamdownstream box plots show that some of the highest nutrient levels in the dataset were reported from stations in the downstream portions of the segment in a heavily industrialized reach. It is likely that industrial sources (chemical storage, manufacturing, and so forth) contribute disproportionately to nutrient loads in

12 this watershed. The analysis suggested the existence of trends in dissolved oxygen (DO) concentration in most of the assessment units located in unclassified portions of the waterway and at stations in three of the seven assessment units in the classified channel. With the exception of two trends in unclassified units, all trends suggest increasing DO concentrations over time. One of the two stations exhibiting a downward DO trend is located in an assessment unit that is not currently listed as impaired (1007B_02). A plot of DO over time at this station follows. Analysis of the annual median of pooled ph data suggest that ph is trending upward in the watershed. When all data are combined, the trend does not seem dramatic but is more significant when examined at the station level. Statistically significant trends were found for 44 of the 61 stations in the dataset and all but one reveal a positive trend. A plot of data from station follows as an example. The analysis of annual medians for pooled data suggests that total dissolved and suspended solids are declining in both the classified and unclassified regions of the watershed. Graphs illustrating this trend in classified waters appear below. Recommendations: Complete and implement the plan to address bacteria sources through the BIG. Address the various concerns found in this segment summary through stakeholder participation. Continue collecting water quality data to support actions associated with watershed protection plan development and future modeling. Work with local partner and contract labs to lower detection limits for nutrients

13

14

15

16

17

18

19

20

21

22