The Sabine River Authority 1998 Summary Report of water quality in the Sabine River Basin reported some water quality concerns identified by the Sabine River Authority (SRA) systematic subwatershed-screening program. Concerns for ammonia, and non-support of stream standards for dissolved oxygen, total dissolved solids, and chloride were identified. The design of this study was tailored to examine these specific concerns identified by historic sampling. The Hawkins Creek subwatershed is mostly rural, but has significant numbers of suburban housing developments and widespread oil and gas leases. Hawkins Creek has been subject to periodic oil and saltwater spills. Concerns for chlorides and total dissolved solids may indicate impact from oilfield runoff and periodic spills, while low dissolved oxygen and elevated levels of ammonia would be more likely associated with population developments or products of natural decay of organic material. For this study, one set of samples was taken during normal flow conditions to help establish ambient conditions. A rainfall event sample was planned, but delayed due to logistics of long-term deployment of auto-samplers and the volume of water required for the different analyses desired. Manual sample collection was planned as an alternative to auto-samplers. Reduced funding forced a termination of this study before the rainfall event sampling could be completed.

Sampling for benthic macroinvertebrates and fish was completed. Sampling collections were made twice, once during early summer and again during the late summer index period. Routine field and laboratory parameters, total and dissolved metals in water, and biomonitoring and rapid bio-assessment (RBA) were collected at all sites.

Sampling Methods

The following types of samples were collected at each of the six sites on Hawkins Creek.

Ambient Sampling: Normal flow sampling included dissolved oxygen, pH, conductivity, temperature, total dissolved solids, chlorides, sulfates, nutrients, E. coli, total organic carbon, total and dissolved metals in water, metals in sediment, and stream flow.

Aquatic Life: Ambient toxicity samples were taken during the normal flow sample event and in-stream rapid biological assessments of the fish and benthic macroinvertebrate communities were performed twice at each site, once during early summer and again during the late summer index period.

Priority Pollutants: A priority pollutant scan was planned for any samples for which ambient toxicity indicated consistent lethality to laboratory organisms. No confirmed toxicity was observed and therefore priority pollutants were not analyzed for any of the samples collected during this study.

Sampling Locations

Locations for sampling sites were selected to evaluate upstream to downstream trends and to separate possible influences from several regions of the sub-watershed. Most of the tributaries to Hawkins Creek are intermittent and so only main stem sites were selected.

Hawkins Creek Sampling Sites

SRA ID	Description	TNRCC #	Parameter Set
HWK2206	Hawkins Creek at FM2206	10383	AM, AT, PP*, RBA
HWKWR	Hawkins Creek at Whatley Road	10384	AM, AT, PP*, RBA
HWK2605	Hawkins Creek at FM2605	15487	AM, AT, PP*, RBA
HWK2275	Hawkins Creek at FM2275	16683	AM, AT, PP*, RBA
HWK1844	Hawkins Creek at FM1844	16684	AM, AT, PP*, RBA

Parameter Set Codes: AM = Ambient Sampling, AT = Ambient Toxicity, PP = Priority Pollutants, RBA = Rapid Biological Assessment.

A priority pollutant scan was done on selected sites only if ambient toxicity indicated lethality.

Hawkins Creek at FM2206 is the furthermost downstream site representing most of the watershed before its confluence with the Sabine River. This location is where most historical data from Hawkins Creek has been collected. The City of White Oak has its treated wastewater effluent outfall about two stream-miles upstream from this site.

Hawkins Creek at Whatley Road was selected to show any differences in water quality after the confluence of Glendale Creek. Glendale Creek has been affected by several oil spills in the past.

Hawkins Creek at FM2605 is about 100 meters downstream of a major unnamed tributary.

Hawkins Creek at FM2275 represents the upper 1/3 of the watershed, including a number of fairly small tributaries from oilfield and residential areas.

Hawkins Creek at FM1844 is the most upstream site. This location usually has a small year-round flow and there are some saltwater injection wells in its northeastern reaches. Bridge construction at FM1844 during this study caused some sedimentation downstream of the bridge so most sampling was done upstream. Some evidence of a past oil spill was seen at this location.

Stream Flow Data

The normal flow sample set was collected on 7/16/02. The most recent rain event was a light rain during the sample event. Another rain event had occurred three days previous. Flows measured at all sites during the normal flow sample run ranged from 3.6cfs at HWK2275 to 8cfs at HWK2605.

Water Quality Data

Water chemistry data was mostly routine and normal. Some parameters were influenced by recent runoff. A light rain fell during this sample run and there was a rain, probably in excess of ½-inch, three days previous. In spite of recent rains, flow was 8cfs or less at all sites. Use of this data as a first flush rain event was considered but at least seven days of dry weather was required prior to a first flush rain event sample. Probably as a result of recent runoff, all of the E. coli samples taken during this sample event exceeded stream standards. E. coli was highest at the most upstream site, HWK1844, and lowest at the most downstream site. The Hawkins Creek sub-watershed has not historically had bacteriological concerns. Turbidity was 122NTU at the most upstream site and ranged from the 20’s to 40’s at the other sites. Specific conductance was generally highest at the upstream sites and lower downstream. The pH was essentially the same at all sites but the trend was for increasing pH from upstream to downstream. Nutrients were below screening guidelines at all sites. Nitrate/nitrite was elevated at the most downstream site. There was no known wastewater plant upset at the City of White Oak upstream so the source of elevated nitrate/nitrite is unknown. Orthophosphate was less than 0.04mg/l at all sites. Sulfate was less than stream standards at all sites. Sulfate was highest at the most upstream and downstream sites and lower in the middle. Chloride and TDS followed conductivity trends and was higher at the three most upstream sites and lower at the two downstream sites. Chloride exceeded stream standards at the three upstream sites. Total hardness was a little higher at the more upstream sites. Alkalinity was 20mg/l at most sites and <10mg/l at HWK2275.

Bacteriological

E. coli exceeded stream standards at all sites during this sample event. E. coli was highest at the most upstream site, HWK1844, and lowest at the most downstream site. Possible sources in this upstream region include pastureland immediately upstream of this site and a home near the site. There was not any evidence of a severe problem from a failed septic system, such as lush vegetation or thick algal growth. The pastureland did not appear to be heavily grazed. This site also had a very high turbidity. Turbidity and E. coli were closely correlated for all sites.

Dissolved Oxygen

Dissolved oxygen was well above the minimum required by stream standards at all sites and indicated high water quality.

Specific Conductance

Specific conductance was elevated in the upper three sites and fairly normal downstream. There is only about a mile between HWK2605 and HWKWR and flow at both sites was almost the same, but the conductivity at HWKWR was less than half the conductivity at the upstream site.

Total Dissolved Solids (TDS)

Total dissolved solids are calculated from the specific conductance values and so the same trends are followed. Stream standards have not been established for Hawkins Creek, but the standard is 400 mg/l for Segment 0505 Sabine River Above Toledo Bend Reservoir. The three upstream sites exceeded that value.

pH

The pH was within limits of the stream standards for Reach 5 of the Sabine River. Samples ranged from 6.21 to 6.72.

Nitrate & Nitrite

Nutrient screening guidelines recommend nitrate & nitrite should be less than 3.50mg/L in streams and rivers. The value at HWK2206 was elevated considerably above other sites, but was still less than screening guidelines. The White Oak WWTP effluent is a possible source, but no upsets were reported at the plant.

Orthophosphate

Orthophosphate was less than 0.04mg/l at all sites. For the purposes of graphing data, one-half of the detection limit was used in place of less-than values.

Sulfates

Stream standards for sulfates have not been established for Hawkins Creek so the standard for the Segment 0505 Sabine River Above Toledo Bend is used as a reference. The standard is an annual average of 75 mg/l and all sites fell below this value.

Chlorides

Stream standards for chlorides have not been established for Hawkins Creek. The standard is an annual average of 175 mg/l for Segment 0505 Sabine River Above Toledo Bend. Chlorides slightly exceeded this value two sites, but were well under stream standard limits for the two downstream sites

Hardness

Total hardness ranged between 48 and 64 mg/l. Hardness is an important factor in calculating the toxic limits of some metals. Components of hardness are believed to compete with metals for binding sites on cell membranes. Levels of metals sampled were below levels thought to be toxic to aquatic life.

Alkalinity

Alkalinity was 20mg/l at most sites. Alkalinity is considered to be representative of good pH buffering capacity.

Turbidity

Turbidity was 122 NTU at the most upstream site and ranged from the 20’s to 40’s at the other sites. The stream is quite shallow at this location and surface water is closely associated with bottom sediments. There are a few horses in the pasture upstream of the site and some erosion of stream banks at access points.

Dissolved Metals in Water Data

Results from samples for dissolved metals in water are not within ranges thought to cause chronic or acute toxicity.

Metal (µg/l)	HWK 1844	HWK 2275	HWK 2605	HWK WR	HWK 2206
Arsenic	<5	<5	<5	<5	<5
Barium	190	329	284	138	138
Cadmium	<0.1	<0.1	<0.1	<0.1	<0.1
Chromium	<5	<5	<5	<5	<5
Copper	<1	<1	<1	<1	2
Lead	<1	<1	<1	1	<1
Nickel	<5	<5	<5	<5	<5
Silver	<0.5	<0.5	<0.5	<0.5	<0.5
Zinc	11	12	<5	<5	<5
Mercury (sediment)	<0.1	<0.1	<0.1	<0.1	<0.1
Selenium	<2	<2	<2	<2	<2

Ambient Toxicity Data

Ambient toxicity samples taken at the most downstream site during past years (1995 and 1996) indicated some concern for toxicity problems. For this study, samples from the most downstream three sites had lethality for Pimephales, but no toxicity for Ceriodaphnia. The lethality in the Pimephales appeared to be the result of a fungal infection and toxicity could not be confirmed. The Ceriodaphnia are more sensitive to almost every toxin, which would indicate not toxicity was present.

Site	TNRCC#	Date Tested	Ceriodaphnia dubia		Pimephales promelas
Historical Data Review
HWK2206	10383	2/14/1995		Sublethality	No toxicity
HWK2206	10383	5/16/1995		Sublethality	No toxicity
HWK2206	10383	8/1/1995		No toxicity	No toxicity
HWK2206	10383	11/7/1995