The Sabine River Authority (SRA) 1998 Summary Report of water quality in the Sabine River Basin reported some water quality concerns identified by the SRA systematic sub-watershed screening program. Concerns for ammonia, ambient toxicity, and rapid bio-assessment; possible concern for orthophosphate; and nonsupport of stream standards for dissolved oxygen, total dissolved solids, and fecal coliform were identified. The design of this study was tailored to examine the specific concerns identified by historic sampling. The Grace Creek Subwatershed is almost entirely urban and non-point runoff is the probable source of the water quality concerns. One set of samples for this study was taken during normal flow conditions to establish ambient or baseline conditions, and a rainfall event sample was taken to evaluate first-flush runoff from different areas of the watershed. Due to periodic toxicity in historic biomonitoring analyses, samples were taken for priority pollutants at all sites during normal and rainfall event flow. These samples were to be submitted for analysis only if biomonitoring indicated toxicity. Benthic macroinvertebrates and fish collections were made once during early summer and again during the late summer index period. Routine field and laboratory parameters, total and dissolved metals in water were collected at all sites. Biomonitoring and rapid bioassessments (RBA’s) were also conducted at each site. Texas Watch volunteers who work for the City of Longview submitted additional data, which are also presented in this report. Rainfall event sampling utilized SRA, and Longview employees to take grab samples during the rain event. Participation and support also came from the TNRCC Region 5 office, the TPWD, and City of Longview employees.

Sampling Methods

The following types of samples were employed at each of the six sites on Grace Creek and its tributary streams.

Ambient Sampling: Dry weather sampling included dissolved oxygen, pH, conductivity, temperature, total dissolved solids, chlorides, sulfates, nutrients, fecal coliform and streptococcal bacteria, total organic carbon, total and dissolved metals, metals in sediment, and stream flow.

Aquatic Life: Ambient toxicity samples were taken at all sites during the rainfall and dry weather sampling events in an effort to clarify the source and identity of toxicity observed in previous samples. In-stream rapid biological assessments of the fish and benthic communities were also done twice at each site, once during early summer and again during the late summer index period.

Priority Pollutants: In an effort to identify the toxic element indicated by biomonitoring, a priority pollutant scan was planned for any samples for which ambient toxicity indicated consistent lethality to laboratory organisms. One sample during the study, a rain event sample, showed lethality during one test and no toxicity during a subsequent test on the same sample. Due to the transient nature of the observed toxicity, priority pollutants were not run in any of the samples collected.

Rainfall Event Sampling: A set of samples were collected during the first flush of one rain event that were analyzed for the same parameter list as for the ambient condition samples.

Texas Watch Data Collection: Several employees with the City of Longview are certified to collect water quality data using the Texas Watch volunteer citizen monitoring kits. The volunteers used a calibrated Hydrolab Minisonde to collect data for Texas Watch. This data is also included to supplement study data.

Sample Locations

Sampling site locations were selected to evaluate different parts of the watershed by sampling most of the major tributaries of Grace Creek and to monitor cumulative downstream conditions with several sites on the main-stem of Grace Creek.

Grace Creek Sampling Sites

SRA ID	Description	TNRCC #	Parameter Set
GC04	Grace Creek at FM 1845	14499	AM, RF, AT, PP*
WCGD	Wade Creek at Garfield Drive	16685	AM, RF, AT, PP*
GC05	Grace Creek 100m upstream of US 80	16686	AM, RF, AT, PP*
GUTH80	Guthrie Creek 100m upstream of US 80	16687	AM, RF, AT, PP*
HCLR	Harris Creek at Lamond Road	16688	AM, RF, AT, PP*
GC06	Grace Creek at North Loop 281	16689	AM, RF, AT, PP*

Parameter Set Codes: AM = Ambient Sampling, RF = Rainfall Event, AT = Ambient Toxicity, PP = Priority Pollutants

* Note: A sample for priority pollutants was collected at each site but was to be submitted for analysis only if toxicity was indicated by the ambient toxicity sample.

Grace Creek Subwatershed Map

Grace Creek at North Loop 281 is the most upstream, site sampled. Four major tributaries with watersheds in northern Longview and partially outside the city limits have their confluence immediately upstream of this site. This watershed includes a large golf course and some street runoff but it has a lot more rural characteristics than the other sites.

Grace Creek 100 m upstream of US 80 is near the midpoint of the city and represents a large portion of the northern half of the watershed. This site is just upstream from the confluence of Guthrie Creek.

Guthrie Creek 100 m upstream of US 80 is a major tributary of Grace Creek and has the eastern portion of Longview as its watershed. This portion of the city is primarily residential. This site is just upstream of the confluence of Guthrie Creek with Grace Creek.

Harris Creek at Lamond Road is a tributary from the west side of Longview and has its confluence with Grace Creek near US 80. Harris Creek was sampled immediately downstream of Lake Lamond. Land use is largely industrial.

Wade Creek at Garfield Drive has its confluence with Grace Creek about 0.75 km upstream of FM 1845. This intermittent stream receives runoff from a railroad switching station.

Grace Creek at FM 1845 is a historical sampling site and is the most downstream public access to Grace Creek prior to its confluence with the Sabine River.

Stream Flow Data

The design of the study called for normal or low flow sampling and for a first flush rain event sample set. The normal flow sample was collected on 5/23/00 and a rain event was sampled on 11/27/01. There were fourteen days with no rainfall runoff prior to the rain event. The City of Longview recorded 2.27 inches of rain during the night the rainfall event samples were taken. The rain appeared to have covered the entire study area although one site (GC05) had lower flow than was expected. Although the flow was lower than expected, the water level rose 18 inches at this site during the rain event. Several rain event collection methods were considered initially. Using auto-samplers has the advantage of requiring fewer people for sampling and less coordination obstacles in gathering equipment and staff before a storm and intercepting water samples at rising flow. Due to the short-term nature of this study, the large volume of water needed at each site for the desired tests, and security of unattended samplers in an urban setting, the decision was made to sample by hand. The rain event covered the entire watershed, was after at least a week of dry weather, and was heavy enough to provide a significant increase in flow. Water level elevations were measured the day before the rain event to establish pre- and post-rain stream level.

Flow was measured at all sites during the normal flow sample run and again during the rainfall runoff event. In May the highest flow was 27.1 cfs at the most downstream site, Grace Creek at FM 1845 (GC04). During the rain event this site was flowing at 389 cfs. Wade Creek at Garfield Drive (WCGD) was 1.3 cfs during normal flow sampling and up to 43.7 cfs during the rain event. Grace at US 80 (GC05) had about 16 cfs during both sample events. Guthrie Creek at US 80 (GUTH80) was 2.7 cfs during normal flow and up to 133 cfs during the rain event. During the rain event, sites downstream of US 80 would be more typical of the large amount of flow from Guthrie Creek than from Grace Creek above US 80. Grace Creek at North Loop 281 (GC06) had 9.10 cfs during normal flow and 22.9 cfs during the rain event. Harris Creek at Lamond Road (HCLR) had more flow during the normal flow event (2.5 cfs) than during the rain event (0.65 cfs). Due to the dry weather prior to the rain event, Lake Lamond, just upstream of this site, probably absorbed most of the runoff.

Bacteriological and Water Chemistry Data

Much of the water chemistry was predictable as a function of rainfall sampling vs. normal flow. Conductivity was generally low during the rainfall event and higher at normal flow. Dissolved oxygen was generally high in the rain event samples and the water lower. Turbidity was predictably elevated in the rain event samples. Bacteriological values were mostly in the thousands during the rain event and in the hundreds during normal flow.

Bacteriological:

Fecal coliform and streptococcal bacteria have been above stream standards in most historical samples at GC04. Samples taken during this study were typical of historical values although samples taken during normal flow were much lower that the runoff event samples. Harris Creek at Lamond Road (HCLR) bacteriological values were relatively low in both sample events. Wade Creek at Garfield Drive (WCGD) had an unusually large number of coliform bacteria in the normal flow sample. Investigation upstream for a possible source was unsuccessful. The City of Longview took additional fecal coliform samples seven days later and found approximately one thousand CFU/100ml. In the normal flow samples, streptococcal bacteria numbers were less than half of the coliform bacteria at most sites. Low streptococcal to fecal ratios would imply the source of contamination was more likely from human waste than from animal feces.

Dissolved Oxygen:

Historically, dissolved oxygen has occasionally fallen below stream standards at GC04 and some benthic samples indicated possible dissolved oxygen deficits. During this study dissolved oxygen met stream standards at all sites in all but one sample, WCGD, during normal flow. This site also had high fecal coliform at that time. The two lowest values for oxygen during the rain event were at sites with the lowest flow. Benthic and fish communities observed in this study did not indicate serious concerns for dissolved oxygen.

Texas Watch Volunteer Monitoring Dissolved Oxygen

The City of Longview has several employees who have monitored Grace Creek at FM 1845 as a part of their Texas Watch volunteer monitoring program. This data is presented here to compliment other data collected during this study. The monitoring program detected a wastewater leak on 9/16/97. Programs such as this provide the city with more water quality data and early detection of any wastewater leaks that may occur.

Specific Conductance:

Specific conductance ranged from a low of 75 µMhos/cm at Wade Creek during the rain event to a high of 418 µMhos/cm at the same site during normal flow. These values are typical of normal water quality in the Sabine Basin.

Total Dissolved Solids (TDS):

Total dissolved solids are calculated as a percentage of specific conductance so the same trends are followed. Stream standards have not been established for Grace Creek but the standard is 400 mg/l for the Sabine River Above Toledo Bend Reservoir. All samples were below that value. A review of historical data at GC04 does not indicate any concerns for TDS.

pH:

The pH was within limits for typical stream standards for all samples, ranging from 6.24 to 7.66. pH has ranged from 6.6 and 7.1 in historical sampling of GC04.

Nitrate/Nitrite:

Guidance for screening nitrate/nitrite indicates values should fall below 3.50 mg/L. Historical data and study data indicate no concern for nitrate/nitrite. The highest level seen in this study was 0.67 mg/L at WCGD and 0.27 mg/L or less in other samples. The sample at WCGD also had elevated conductivity, bacteria, and lower dissolved oxygen.

Ammonia:

The screening level for ammonia nitrogen in freshwater streams is 0.16 mg/L. Historical samples from GC04 indicate concerns for ammonia. All but one historical value at GC04 has been above this level. The normal flow samples from GC04 and WCGD had elevated ammonia nitrogen with 0.29 and 0.94 mg/L respectively. CG05 and Guth80 were just under the screening level. Ammonia was not analyzed in the rain event sample.

Orthophosphate:

There have been no historical concerns for orthophosphate at GC04. Orthophosphate was less than detection limits (0.05 mg/L) 1 mg/L in all normal flow samples and less than the screening level (0.90 mg/L) in all of the rain event samples. The highest level was in Guthrie Creek (0.16 mg/L) and next highest at the most upstream Grace Creek site.

Sulfates:

Stream standards for sulfates haven’t been established for Grace Creek so the standard for the Sabine River Above Toledo Bend is used as a reference. The standard is 75 mg/L and all sites fell below this value. WCGD had the highest level with 64.5 mg/L in the normal flow sample. Historical levels at GC04 have ranged from 8.0-29.4 mg/L.

Chlorides:

Stream standards for chlorides haven’t been established for Grace Creek. The standard is 175 mg/L for the Sabine River Above Toledo Bend. Chlorides were generally higher during normal flow but well under typical stream standards. Historical values have ranged from <1.5-82 mg/L.

Hardness:

Historical hardness values at GC04 range from 32 to 92 mg/L. In this study, total hardness ranged between 28 and 88 mg/L at all but one site. Normal flow samples were generally higher than wet weather samples. WCGD was significantly higher than other sites with 136 mg/L. Although this level of hardness does not present a water quality problem, the value is unusual for the region and is indicative of an impact at this site.

Alkalinity:

Historical alkalinity at GC04 ranges from 12-80 mg/L. In this study, alkalinity was only analyzed in normal flow samples and values fell within the historical range. WCGD was significantly higher than other sites with 79 mg/L. Alkalinity is considered to be representative of good pH buffering capacity but the value at WCGD is unusual and may be indicative of an impact at this site.

Turbidity:

Historical turbidity values from GC04 range from 15.4 to 118 NTU. In this study, turbidity ranged from 7.1-37.5 NTU in dry weather samples and most rainfall event samples were at least 100 NTU. WCGD was very clear during the normal flow event. HCLR was quite clear during the rainfall event. This site is immediately downstream from Lake Lamond. GC05 had lower than expected flow during the rain event and turbidity was also relatively low.

Dissolved Metals in Water Data

Dissolved metals in water were analyzed in samples collected during the rainfall runoff event. The results were within acceptable levels for water of high quality.

Metal (µg/L)	GC04	WCGD	GC05	Guth80	HCLR	GC06
Arsenic	<2.33	<2.33	<2.33	<2.33	<2.33	<2.33
Barium	97.0	39.6	164	86.4	128	137
Cadmium	<1.08	<1.08	<1.08	<1.08	<1.08	<1.08
Chromium	<2.71	<2.71	<2.71	<2.71	<2.71	<2.71
Copper	1.5	1.6	<1.00	1.0	<1.00