Addendum. Use Attainability Analysis for Site Specific Selenium Criteria: Alkali Creek. February 23, 2009

Transcription

1 Addendum Use Attainability Analysis for Site Specific Selenium Criteria: Alkali Creek February 23, 2009 Prepared by MWH Americas, Inc. Prepared for EnCana Oil and Gas (USA) Inc.

2 Page 2 Responses to Comments from the U.S. Fish and Wildlife Service 1. Evaluation of Additional Alternatives The UAA approach is to demonstrate that removal of the discharge would cause more environmental damage to correct than to leave in place. This assumes that the source of pollution (i.e., produced water discharges) cannot be remedied or that the only remedy available is to stop the discharges. Other options that should be considered include: water treatment, phytoremediation, and the use of constructed wetlands to lower selenium concentrations in the produced water. These options have not been evaluated in the UAA. The UAA report should assess the feasibility of these options. A feasibility study of potential water management options for operations in Frenchie Draw would involve evaluations of engineering-related subjects that are outside the scope of the Wyoming Water Quality Regulations, Section 33 (b) (ii) (iii) (WYDEQ, 2007) for a Site Specific Criteria UAA; hence, are not included in this report, which is prepared for review by the permitting agency of WYDEQ. 2. Missing Impoundment Evaluation A large impoundment approximately 6 acres in size is located 400 to 500 feet west of Alkali Creek and approximately 0.75-mile west of sampling location Alkali #2 (Figure 1). This impoundment drains into Alkali Creek and receives water from at least three produced water outfalls as shown on Figure 8 on page 21 of the UAA Report. The approximate coordinates of the impoundment are: N / W. Although the impoundment is not on the main channel of Alkali Creek, it does drain into Alkali Creek and it does appear to receive produced water from active outfalls located upstream. If macroinvertebrates and fish inhabit this impoundment, the potential for selenium bioaccumulation exists especially if inflow and outflow are not sufficient to offset the concentration of selenium, by evaporation. In our view, this presents a data gap in the UAA. Please explain why this impoundment was not included in the selenium assessment. This impoundment was not included in the original aquatics sampling program because the water body does not support populations of fish or macroinvertebrates and is not part of Alkali Creek. This impoundment has most commonly been referred to as Pink Lake. Below is a description Pink Lake and analytical results for recently collected samples of water and sediments. Surface Ownership and Purpose: The land surface where Pink Lake is located is owned by BLM and leased by the TJ Spratt family. The reservoir was built approximately 5 to

3 Page 3 10 years ago. Its intended use is livestock watering. According to Mike Greff, Water Management Supervisor at EnCana, the reservoir has been consistently used primarily for livestock watering for many years. Description: Pink Lake has an estimated surface area of 4 to 5 acres and maximum depth of 15 ft. The primary source of water to Pink Lake is produced water discharges from 3 to 4 produced water discharge outfalls located in Frenchie Draw. Water exits Pink Lake through an outlet leading to Alkali Creek; hence, the water volume is continually replenished and its water quality is not subject to extreme evapoconcentration. The soils at Pink Lake are classified at Youngston-Effington loams. The NRCS description of these soils is as follows: Youngston-Effington loams are very deep, well drained soils with moderately slow permeability that formed in stratified alluvium from mixed sources. This association is on recent alluvial terraces, fans, and fan aprons. Slopes range from 0 to 10 percent. Typical soil textures are fine-loamy, mixed to sandy loams with percent sand in the upper five feet. The association may be associated with a saline lowland physiography. Habitat: The impoundment is located in an area near sage grouse brood habitat and pronghorn fawning and nursing habitat previously surveyed in , but does not support or provide nesting habitat for sage grouse or nursing habitat for pronghorn. Based on photos and brief surveys of the site (Attachment A), the vegetation along the perimeter of the impoundment is marginal, comprised mainly of weedy species and grasses, with sparse shrubs present in a few locations along the banks. The area lacks consistent vegetative characteristics typically utilized by waterfowl for nesting and does not meet nesting requirements for species known to inhabit the area such as Mallard ducks, whom prefer vegetation heights around two feet to conceal nests. Water and Sediment Quality: Sediment and water samples were collected from the impoundment in January 2009 to determine if selenium was accumulating. The sediment and water samples were each composites of two subsamples collected in the vicinity of the outflow structure. The laboratory results indicate that the selenium concentration in the sediments is less than the reporting limit of mg/kg. The total recoverable selenium concentration in the water sample was 28 µg/l, which is similar to concentrations found in Alkali Creek downstream of the discharge points. The analytical data sheets are provided in Attachment B. Based on the results from the field sampling we can conclude that selenium is not accumulating in the sediments or surface water in the impoundment and is safe for the wildlife and domestic animals utilizing the area. 3. Selenium Evaluation This section points out that selenium occurs in many soil types and enters ground and surface waters through natural weathering processes such as erosion, leaching and runoff. The source of selenium in oilfield produced water is probably from deep

4 Page 4 seleniferous geologic formations such as marine Cretaceous shale. According to well information from the Wyoming Oil and Gas Conservation Commission, the Fort Union formation is one of the target formations in the Frenchie Draw field. The Fort Union formation is a potentially seleniferous formation (Case and Cannia 1988). It is unlikely that the leaching of selenium from surficial material would reach the formation water in the oil reservoir. This section should clarify that the selenium in the produced water is likely from deep geologic formations and not from the soils. Water quality data directly from the outfalls, if available, should be included in the UAA report to show the amount of selenium discharged into Alkali Creek. We agree that the elevated levels of selenium occurring in the surface water of the outfalls and Alkali Creek are primarily a result of the produced water discharges. However, selenium concentrations in background areas of Badwater Creek upstream of its confluence with Alkali Creek and Bridger Creek upstream of its confluence with Badwater Creek also commonly exceed water quality criterion of 5 μg/l. Selenium concentrations in surface water samples collected from Badwater Creek upstream of the confluence ranged from 1 to 20 μg/l, and 2 to 11 μg/l for Bridger Creek upstream of its confluence with Badwater Creek. In addition, the highest selenium concentrations found in stream sediments and soils also occurred in these same background areas of Bridger Creek and Badwater Creek. These results indicate that selenium occurs naturally throughout the watersheds in surficial sediments, soils, and water. 4. Fish Sampling: The date of the first fish survey should be inserted in the last sentence of the paragraph. Although notable numbers of plains killifish were observed in Alkali Creek on August 26, the UAA report does not specify how far upstream from the confluence with Badwater Creek these fish were observed. Page 9 of Appendix C (WLS Wildlife Report Badwater Creek) states that fish were collected on August 26 at 10m, 100m, and 300m below the Alkali Creek confluence with Badwater Creek as a matter of interest after finding substantial numbers of killifish in Alkali Creek proper. It is unclear why killifish were not collected in Alkali Creek confluence with Badwater Creek. Table 4 of Appendix C, page 10, shows that killifish were collected from Alkali Creek 100m (328 ft) above the confluence with Badwater Creek that killifish further upstream in Alkali Creek were not collected for selenium analysis. The table shows that the uppermost aquatic sampling site for fish (Aquatic #7) was located approximately 8 to 9 stream miles downstream from the water sampling location Alkali 3 and 12 to 14 stream miles down from Alkali 2. Waterborne selenium concentrations at Alkali 2 and Alkali 3 exceeded 2µg/L over 90 percent of the time and exceeded 5 µg/l over 80 percent of the time. Water samples from Lower Alkali Creek (near Aquatic #7) and Badwater Creek exceeded 5 µg/l 50 and 56 percent of the time, respectively. Statistical analysis of the waterborne selenium data shows a significant difference between selenium concentrations in sampling stations Alkali 2 and 3 and the

5 Page 5 downstream locations (Kruskal-Wallis, p 0.001). Please discuss why fish were not collected from Alkali Creek upstream, of sampling station Aquatic #7 given that notable numbers of plains killifish were observed in Alkali Creek on August 26 and the significant difference in selenium in Alkali Creek and the downstream sampling locations. Attempts to collect fish samples from both Alkali Creek and Badwater Creek were conducted on two separate sampling dates in July 2008 and August Although it is not directly stated in the WLS report, the entire reach of Alkali Creek (AC9 to the confluence with Badwater) was included in sampling effort. On the first sampling date, no fish were found along the entire reach of Alkali Creek, therefore it was not possible to collect sample upstream of the confluence with Badwater Creek. On the second date, notable numbers of plains killifish were observed in lower Alkali Creek near the confluence with Badwater and samples were collected at approximately 100 m upstream of the confluence where these fish were present. It was not possible to collect samples in upper Alkali Creek (above AC3) on either date because fish were not present. 5. Conditions of Site Specific Selenium Criteria: A site specific selenium criterion of 50 µg/l is proposed in the UAA report. The UAA report does not provide selenium data from the outfalls to show if the existing produced water discharges will meet the proposed 50 µg/l criterion. Please clarify if the proposed criterion will apply to the outfalls or if the criterion will be applied downstream from the outfalls where dilution may be a factor. Please discuss measures that will be implemented if the discharges exceed the proposed criterion of 50 µg/l? The implementation of the proposed selenium criterion and conditions for monitoring and reporting will be based on provisions provided by WYDEQ to EnCana. These conditions will specify how instances of exceedance of the selenium criterion will be handled. References Cited: WYDEQ, Wyoming Department of Environmental Quality Chapter 1: Wyoming Surface Water Quality Standards Implementation Policies for Antidegradation, Mixing Zones, Turbidity and Use Attainability Analysis 2007.

6 Page 6 Attachment A Pink Lake looking southeast across main body of the lake. Pink Lake Dam and outfall structure looking east \

7 Page 7 Pink Lake typical shrubs and grassland

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