| Water Body Name: | Arroyo Las Positas |
| Water Body ID: | CAR2043008020010905115005 |
| Water Body Type: | River & Stream |
Lines of Evidence (LOEs) for Decision ID 7578 |
| LOE ID: | 4810 |
| Pollutant: | Low Dissolved Oxygen |
| LOE Subgroup: | Pollutant-Water |
| Matrix: | Water |
| Fraction: | None |
| Beneficial Use: | Warm Freshwater Habitat |
| Aquatic Life Use: | Wildlife Habitat |
| Number of Samples: | 9 |
| Number of Exceedances: | 4 |
| Data and Information Type: | PHYSICAL/CHEMICAL MONITORING |
| Data Used to Assess Water Quality: | Data used to evaluate dissolved oxygen were collected by SWAMP in 2002. In 4 out of 9 deployments, minimum dissolved oxygen levels fell below the objective of 5 mg/L. Minimum values were nearly anoxic (0.56 mg/L) at one site in the summer season. Low dissolved oxygen concentrations generally occurred during the night and early morning hours.
Continuous depressed levels of dissolved oxygen (< 5.0 mg/L) lasted from over 5 hours (dry season, downstream location) to 12 hours and 45 minutes (dry season, Altamont Creek upstream of confluence with Arroyo Las Positas). Dissolved oxygen levels fell below 5 mg/L during one additional deployment in the upstream section of Arroyo Las Positas. The longest duration of suppressed oxygen levels lasted for over 12 hours and the patterns of dissolved oxygen concentrations at this location followed closely that of Altamont Creek. Although these measurements support the listing decision and indicate that dissolved oxygen levels are the cause of the impairment, they cannot be used directly because of the marginal (by +/- 0.4%) exceedance of the quality assurance requirements. |
| Data Reference: | Water Quality Monitoring and Bioassessment in Nine San Francisco Bay Region Watersheds: Walker Creek, Lagunitas Creek, San Leandro Creek, Wildcat Creek/San Pablo Creek, Suisun Creek, Arroyo Las Positas, Pescadero Creek/Butano Creek, San Gregorio Creek, and Stevens Creek/Permanente Creek. Oakland, CA: Surface Water Ambient Monitoring Program, San Francisco Bay Regional Water Quality Control Board |
| Water Quality Objective/Criterion: | The numeric water quality objective for dissolved oxygen is 5.0 mg/L minimum for waters designated as warm freshwater habitat. The median dissolved oxygen concentration for any three consecutive months shall not be less than 80 percent of the dissolved oxygen content at saturation. |
| Objective/Criterion Reference: | San Francisco Bay Basin (Region 2) Water Quality Control Plan (Basin Plan) |
| Evaluation Guideline: | |
| Guideline Reference: | |
| Spatial Representation: | Dissolved oxygen was measured at five sites. Three of these sites were located on the mainstem of Arroyo Las Positas, while one site each was located on Altamont Creek and Arroyo Seco, two major tributaries. The lowest dissolved oxygen levels were measured at site ALP105 on Altamont Creek. Low dissolved oxygen levels also occurred in the mainstem of Arroyo Las Positas during the summer season. |
| Temporal Representation: | The SWAMP Program performed continuous monitoring of dissolved oxygen at 15 minute intervals for periods of 1-2 weeks in each of three different seasons: winter (March 2002; 3 sites, 1 site meeting quality assurance requirements), spring (April 2002; 5 sites, 4 sites meeting quality assurance requirements), and summer (late June and late July 2002; 5 sites, 4 sites meeting quality assurance requirements). |
| Environmental Conditions: | Arroyo Las Positas flows west through the eastern Livermore valley before its confluence with Arroyo Mocho in eastern Pleasanton. The lower and middle sections of Arroyo Las Positas and Altamont Creek flow through the northern portion of the city of Livermore, a city of 82,000 people. The upper watershed is primarily used for cattle grazing. The lowest and highest dissolved oxygen levels were measured in a section of Altamont Creek that contained very high amounts of benthic algae and was located downstream of a golf course and small eutrophic pond. The main stem of Arroyo Las Positas is almost completely devoid of riparian vegetation as a result of extensive channel alteration and incision. |
| QAPP Information: | All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB 2002). |
| QAPP Information Reference(s): | Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version) |
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| LOE ID: | 4811 |
| Pollutant: | Dissolved oxygen saturation |
| LOE Subgroup: | Pollutant-Water |
| Matrix: | Water |
| Fraction: | None |
| Beneficial Use: | Warm Freshwater Habitat |
| Aquatic Life Use: | Wildlife Habitat |
| Number of Samples: | 9 |
| Number of Exceedances: | 5 |
| Data and Information Type: | PHYSICAL/CHEMICAL MONITORING |
| Data Used to Assess Water Quality: | Data used to evaluate dissolved oxygen was collected by SWAMP. Supersaturated dissolved oxygen levels greater than 200% were observed in 5 out of 9 deployments, including a maximum value of 395%, indicating tremendous oxygen production by algae (eutrophication). Supersatured conditions always occurred during the daylight hours. The maximum diurnal range in dissolved oxygen was greater than 30 mg/L, higher than any values ever reported in the literature (Kent et al. 2005). |
| Data Reference: | Water Quality Monitoring and Bioassessment in Nine San Francisco Bay Region Watersheds: Walker Creek, Lagunitas Creek, San Leandro Creek, Wildcat Creek/San Pablo Creek, Suisun Creek, Arroyo Las Positas, Pescadero Creek/Butano Creek, San Gregorio Creek, and Stevens Creek/Permanente Creek. Oakland, CA: Surface Water Ambient Monitoring Program, San Francisco Bay Regional Water Quality Control Board |
| Algal productivity and nitrate assimilation in an effluent dominated concrete lined stream. Journal of the American Water Resources Association: 41: 1109-1128 | |
| Water Quality Objective/Criterion: | All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. |
| Objective/Criterion Reference: | San Francisco Bay Basin (Region 2) Water Quality Control Plan (Basin Plan) |
| Evaluation Guideline: | Dissolved oxygen supersaturation above 200 percent results in mortality of fish due to gill and skin lesions from gas bubble disease (Woodbury 1942, Renfro 1963, Weitkamp and Katz 1980). |
| Guideline Reference: | A sudden mortality of fishes acoompanying a supersaturation of oxygen in Lake Waubesa, Wisconsin. Trans. Am. Fish. Soc. 71: 112-117 |
| A review of dissolved gas supersaturation literature. Trans. Am. Fish. Soc. 109:659-702 | |
| Gas-bubble mortality of fishes in Galveston Bay, Texas. Trans. Am. Fish Soc. 92:320-322 | |
| Spatial Representation: | Dissolved oxygen was measured at five sites. Three of these sites were located on the mainstem of Arroyo Las Positas, while one site each was located on the major tributary. The highest dissolved oxygen levels were measured at site ALP105 on Altamont Creek, a major tributary to Arroyo Las Positas. |
| Temporal Representation: | The SWAMP Program performed continuous monitoring of dissolved oxygen at 15 minute intervals for periods of 1-2 weeks in each of three different seasons: winter (March 2002; 3 sites, 1 site meeting quality assurance requirements), spring (April 2002; 5 sites, 4 sites meeting quality assurance requirements), and summer (late June and late July 2002; 5 sites, 4 sites meeting quality assurance requirements). |
| Environmental Conditions: | Arroyo Las Positas flows west through the eastern Livermore valley before its confluence with Arroyo Mocho in eastern Pleasanton. The lower and middle sections of Arroyo Las Positas and Altamont Creek flow through the northern portion of the city of Livermore, a city of 82,000 people. The upper watershed is primarily used for cattle grazing. The lowest and highest dissolved oxygen levels were measured in a section of Altamont Creek that contained very high amounts of benthic algae and was located downstream of a golf course and small eutrophic pond. The main stem of Arroyo Las Positas is almost completely devoid of riparian vegetation as a result of extensive channel alteration and incision. |
| QAPP Information: | All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB 2002). |
| QAPP Information Reference(s): | Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version) |
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| LOE ID: | 4813 |
| Pollutant: | Benthic-Macroinvertebrate Bioassessments |
| LOE Subgroup: | Population/Community Degradation |
| Matrix: | -N/A |
| Fraction: | None |
| Beneficial Use: | Warm Freshwater Habitat |
| Aquatic Life Use: | Wildlife Habitat |
| Number of Samples: | 7 |
| Number of Exceedances: | 7 |
| Data and Information Type: | Benthic macroinvertebrate surveys |
| Data Used to Assess Water Quality: | Benthic macroinvertebrates were sampled from 7 sites in the Arroyo Las Positas watershed in April 2001 by the SWAMP program. Benthic macroinvertebrate assemblage metrics were well outside the range of scores for minimally disturbed reference sites. Taxa richness scores at all 7 sampled sites in the Arroyo Las Positas watershed ranged from 11 to 16 taxa, whereas taxa richness values at reference sites ranged from 28 to 59. No taxa that are sensitive to pollution were present in any of the samples, indicating that pollution has resulted in significant alterations of community ecology. |
| Data Reference: | Water Quality Monitoring and Bioassessment in Nine San Francisco Bay Region Watersheds: Walker Creek, Lagunitas Creek, San Leandro Creek, Wildcat Creek/San Pablo Creek, Suisun Creek, Arroyo Las Positas, Pescadero Creek/Butano Creek, San Gregorio Creek, and Stevens Creek/Permanente Creek. Oakland, CA: Surface Water Ambient Monitoring Program, San Francisco Bay Regional Water Quality Control Board |
| Water Quality Objective/Criterion: | All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors. |
| Objective/Criterion Reference: | San Francisco Bay Basin (Region 2) Water Quality Control Plan (Basin Plan) |
| Evaluation Guideline: | Benthic macroinvertebrate assemblage metric scores that are outside the range of scores for minimally disturbed reference sites indicate significant alterations in community ecology. Taxa richness values at reference sites sampled by the SWAMP program between 2001 and 2003 ranged from 28 to 59. |
| Guideline Reference: | Water Quality Monitoring and Bioassessment in Nine San Francisco Bay Region Watersheds: Walker Creek, Lagunitas Creek, San Leandro Creek, Wildcat Creek/San Pablo Creek, Suisun Creek, Arroyo Las Positas, Pescadero Creek/Butano Creek, San Gregorio Creek, and Stevens Creek/Permanente Creek. Oakland, CA: Surface Water Ambient Monitoring Program, San Francisco Bay Regional Water Quality Control Board |
| Spatial Representation: | Benthic macroinvertebrates were sampled from 7 sites throughout the watershed. Five sites were sampled on the main stem of Arroyo Las Positas, and 2 sites were sampled on Altamont Creek, the major perennial tributary of Arroyo Las Positas. |
| Temporal Representation: | Benthic macroinvertebrates were sampled once in April, 2001. |
| Environmental Conditions: | Arroyo Las Positas flows west through the eastern Livermore valley before its confluence with Arroyo Mocho in eastern Pleasanton. The lower and middle sections of Arroyo Las Positas and Altamont Creek flow through the northern portion of the city of Livermore, a city of 82,000 people. The upper watershed is primarily used for cattle grazing. The main stem of Arroyo Las Positas is almost completely devoid of riparian vegetation as a result of extensive channel alteration and incision. |
| QAPP Information: | All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB 2002). |
| QAPP Information Reference(s): | Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version) |
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| LOE ID: | 4812 |
| Pollutant: | Nitrate |
| LOE Subgroup: | Pollutant-Water |
| Matrix: | Water |
| Fraction: | Dissolved |
| Beneficial Use: | Warm Freshwater Habitat |
| Aquatic Life Use: | Wildlife Habitat |
| Number of Samples: | 8 |
| Number of Exceedances: | 8 |
| Data and Information Type: | PHYSICAL/CHEMICAL MONITORING |
| Data Used to Assess Water Quality: | Eight out of 8 nitrate samples had concentrations greater than 0.5 mg/L. Eight out of 8 nitrate samples also had concentrations greater than 2.0 mg/L. The highest concentrations (8.04 mg/L and 6.52 mg/L) occurred at the same site (ALP110; Arroyo Las Positas, just upstream of Altamont Creek) in January and April 2002, and were among the highest nitrate concentrations measured by SWAMP in the SF Bay Region. |
| Data Reference: | Water Quality Monitoring and Bioassessment in Nine San Francisco Bay Region Watersheds: Walker Creek, Lagunitas Creek, San Leandro Creek, Wildcat Creek/San Pablo Creek, Suisun Creek, Arroyo Las Positas, Pescadero Creek/Butano Creek, San Gregorio Creek, and Stevens Creek/Permanente Creek. Oakland, CA: Surface Water Ambient Monitoring Program, San Francisco Bay Regional Water Quality Control Board |
| Water Quality Objective/Criterion: | Waters shall not contain biostimulatory substances in concentrations that promote aquatic growths to the extent that such growths cause nuisance or adversely affect beneficial uses
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. |
| Objective/Criterion Reference: | San Francisco Bay Basin (Region 2) Water Quality Control Plan (Basin Plan) |
| Evaluation Guideline: | 1. Total nitrogen levels greater than 0.5 mg/L can result in large masses of nuisance algae unless other factors limit algae growth (Bowie et al. 1985; Biggs 2000). Since nitrate is one component of total nitrogen in water, nitrate levels should also be less than 0.5 mg/L.
2. Nitrate (NO3-N) concentrations above 2.0 mg/L can cause toxicity in a variety of freshwater organisms (Camargo et al. 2005). |
| Guideline Reference: | Eutrophication of streams and rivers: dissolved nutrient-chlorophyll relationships for benthic algae. J. N. Am. Benthol. Soc. 19:17-31 |
| Rates, Constant, and Kinetics Formulations in Surface Water Quality Modeling, 2nd Edition. EPA/600/3-85/040. USEPA Environmental Research Laboratory, Athens, GA | |
| Nitrate toxicity to aquatic animals: a review with new data for freshwater invertebrates. Chemosphere 58:1255-67 | |
| Spatial Representation: | Nitrate was sampled at four sites in the watershed, including two main stem sites and two sites on Altamont Creek, an important tributary. |
| Temporal Representation: | Water samples were collected for nitrate analyses during three sampling events. The same four sites were sampled during each sampling event. Data are evaluated from the January 2002 and April 2002 sampling events only. Laboratory methods used on samples collected during September 2001 did not meet quality assurance requirements, so this data has not been considered. |
| Environmental Conditions: | Arroyo Las Positas flows west through the eastern Livermore valley before its confluence with Arroyo Mocho in eastern Pleasanton. The lower and middle sections of Arroyo Las Positas and Altamont Creek flow through the northern portion of the city of Livermore, a city of 82,000 people. The upper watershed is primarily used for cattle grazing. The main stem of Arroyo Las Positas is almost completely devoid of riparian vegetation as a result of extensive channel alteration and incision. |
| QAPP Information: | All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB 2002). |
| QAPP Information Reference(s): | Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version) |