NPDES WASTEWATER DISCHARGE PERMIT EVALUATION
Department of Environmental Quality Eastern Region - Pendleton Office 700 SE Emigrant, Suite 330, Pendleton, OR 97801 Telephone: (541)276-4063
PERMITTEE: Idaho Power Company PO Box 70 Boise, ID 83707 File Number: 41297
SOURCE LOCATION: Snake River, River Mile 247
SOURCE CONTACT:
Peter G. Newton Telephone Number: 208-388-2845
PERMIT WRITER:
Heidi Williams Telephone Number: 541-278-4608
PROPOSED ACTION: Renewal of a National Pollutant Discharge Elimination System (NPDES) wastewater discharge permit
SOURCE CATEGORY: Minor Industrial
TREATMENT SYSTEM CLASS: N/A
COLLECTION SYSTEM CLASS: N/A
PERMIT APPLICATION DATE: January 10, 2000
PERMIT APPLICATION NUMBER: 989663
BACKGROUND
Introduction
Hells Canyon Dam is located in the deepest river gorge in North America, the adjacent ridges being over a mile above the river. A stretch of the river about 32 miles below the dam is designated "wild," with another 34 miles being designated "scenic." Recreational use of the river in this area is extensive.
Idaho Power Company operates the Hells Canyon Dam and power facility located on the Snake River at river mile (RM) 247.0. The middle of the Snake River in this vicinity is the border between Oregon and Idaho. The power plant and its discharges are located on the Oregon side of the dam, thus the Oregon Department of Environmental Quality (Department) permits the wastewater outfalls.
The facility discharges wastewater fromth e generator cooling and powerhouse sump into the Snake River at RM 247.0. The facility's currently permitted total combined flow for the cooling and sump wastewater is 9 million gallons per day (MGD). The wastewater is discharged in accordance with National Pollutant Discharge Elimination System (NPDES) permit number 101287. The facility also discharges sanitary wastewater to a holding tank, which is pumped and the contents hauled off site. The current permit for the facility was issued on Idaho Power Company Evaluation Report Page 2
May 23, 1995, and expired on April 30, 2000. The Department administratively extended their permit until final action on their application, which would be the proposed permit.
This proposed permit and its requirements only pertain to the flow from discharge outfalls 001-005, as described below in section "Outfalls." Water quality criteria targets for the Snake River, which passes through the dam, are not part of this proposed permit. The Snake River - Hells Canyon (SR-HC) Total Maximum Daily Load (TMDL), July 2003, document and 401 hydroelectric certification process address those water quality criteria specific to the river and its passage over the Hells Canyon Dam, exclusive of the wastewater discharges. Waste load allocations derived in the SR-HC TMDL for this facility's wastewater outfalls are addressed in this proposed renewal for the permit.
The Department received a renewal application on January 10,2000. A renewed permit is necessary to discharge to state waters pursuant to provisions of Oregon Revised Statutes (ORS) 468B.050 and the Federal Clean Water Act. The Department proposes to renew the permit for the discharges of the cooling wastewater (001-003), sump wastewater (004), and sanitary wastewater (005).
Facility Description
The dam was constructed in 1967, approximately 23 miles downstream of Oxbow Dam. It houses three generating units with a total nameplate capacity (the maximum ability to generate electricity under ideal conditions) of 391 megawatts. Hells Canyon Dam's power plant switchyard is mounted on the dam's face. It contains the conductors, switches, transformers and other equipment that connect the powerhouse generators with the transmission lines leaving the project. There have been no major plant expansions.
The facility produces non-contact generator cooling water, sump wastewater, and sanitary wastewater.
• The non-contact cooling wastewater is discharged through outfalls 001, 002, and 003 into the Snake River at RM 247.0. The current permit limits the discharge to 7.5 million gallons/day (MGD). The permittee is requesting to increase this flow volume to 9 MGD (see "Anti-degradation" section).
• The facility collects wastewater in the power house sump and discharges through outfall 004 into the Snake River at RM 247.0. The current permit limits the discharge to 1.5 MGD.
• The facility is currently permitted to discharge sanitary wastewater from outfall 005 to the Snake River. Because this discharge to the river was disconnected and eventually replaced by a holding tank, the proposed permit will identify the outfall discharge location as being a holding tank.
Table 1 at the end of this report lists the past flows for discharge outfalls 001-003 and 004.
Outfalls
Wastewater is discharged year-round to the Snake River from four outfalls. Outfalls one through three (001- 003) discharge non-contact cooling wastewater. Outfall four (004) discharges sump wastewater. Outfall five (005) discharges sanitary wastewater to a holding tank.
The facility produces non-contact generator cooling wastewater. Water is used to cool the air which cools the generators, the turbine bearing heat exchanger, and the oil for the generator thrust bearings. The generators have an enclosed ventilation system. The air is circulated through air coolers. Water flowing through these coolers absorbs heat from the circulating air. The generator thrust bearing assembly is enclosed in an oil pot Idaho Power Company Evaluation Report Page 3 for bearing lubrication. The oil is kept at a safe operating temperature by water flowing through a finned cooling coil placed circumferentially around the oil pot. The non-contact cooling wastewater is discharged through outfalls 001, 002, and 003 into the Snake River at RM 247.0. The wastewater is discharged below the surface into the tailrace at an average rate of approximately 6.8 MGD (see Table 1, outfalls 001-003).
The facility also produces wastewater from lubrication of the turbine packing glands and from leakage of the dam's construction joints. The average wastewater produced is approximately 0.58 MGD (see Table 1, outfall 004). This wastewater is collected in the power house sump and discharged through outfall 004 into the Snake River at RM 247.0. This discharge is located on the east end of the walkway, which runs along the face of the dam.
The current permit lists Outfall 005 as discharging domestic wastewater to the Snake River. During the term of the current permit, the permittee installed incinerator toilets and removed this river discharge outfall. After some time, the permittee discovered that the incinerator toilets did not function properly. Thus, they were eliminated and replaced by a holding tank, which is pumped approximately every two weeks. This domestic wastewater is transported off site to a lagoon and land application site in Idaho, which is owned by Idaho Power Company.
Anti-degradation
The permittee is requesting an increase in flow for outfalls 001-003. The current permit allows a discharge of 7.5 MGD for the three non-contact cooling water outfalls combined. The permittee is requesting this volume be increased to 9 MGD (3 MGD per outfall). Due to the increase in flows requested for the outfalls, the requirement for an anti-degradation review was addressed. An anti-degradation review is needed if a facility increases its flow, which in turn, may increase parameters discharged. The parameters this facility's proposed permit requires to be monitored in discharge outfalls 001-003 are flow, temperature, oil and grease. The discharge for outfall 004 will remain the same at 1.5 MGD, thus is not addressed in this section. The sanitary wastewater (outfall 005) now discharges to a holding tank, therefore, will also not be addressed in this section.
If the increased discharge is allowed, the facility would discharge a total of 10.5 MGD, which equates to about 16 cfs. The Snake River's 7Q10 flow at the dam is approximately 5,780 cfs. The wastewater discharge flow is about 0.3%) of the river's lowest flow.
Beneficial uses must not be affected by the increase in pollutants resulting from the increased discharge. The designated beneficial uses for the Snake River are listed below in the section titled "Receiving Streams/Impact." Due to the very high dilution occurring (0.3%> wastewater flow versus river flow), an increase in pollutants in the wastewater, due to an increase in flow of 1.5 MGD, would be considered negligible in relation to the receiving water's flow. Thus, due to the nature of this specific situation where it is known that a 1.5 MGD increase in flow will cause no measurable increase in pollutants in the receiving stream, and thus have no effect on the designated beneficial uses, an anti-degradation review will not be required of the permittee.
In December, 2003, the Environmental Quality Commission adopted revisions to OAR 340-041. The new and revised rules were evaluated and compared with the SR-HC TMDL requirements. The report was adjusted to accommodate the revised rules where appropriate. Idaho Power Company Evaluation Report Page 4
Pollutants Discharged
The current permit allows Idaho Power Company to discharge wastewater year-round and sets limits on the following pollutants: temperature, oil and grease, and pH.
The proposed permit will limit the same pollutants. It will also include a new waste load allocation (WLA) for TSS for outfall 004 and a revision of the temperature limit.
Receiving Streams/Impact
Oregon's designated beneficial uses of the Snake River are: public and private domestic water supply, industrial water supply, irrigation, livestock watering, salmonid spawning and rearing, resident fish and aquatic life, wildlife and hunting, fishing, boating, water contact recreation, aesthetic quality, hydro power, anadromous fish passage, and commercial navigation and transportation.
Dams are unusual among permitted facilities in that they physically are a barrier in the river. Thus a variety of impacts occur, such as blockage offish passage, increases in total dissolved gas due to spilling, temperature and flow fluctuations, etc. Although these results of the dam affect water quality of the river downstream, habitat upstream and downstream, etc., this proposed permit only addresses wastewater outfalls 001-004. As stated earlier, mainstem Snake River water quality criteria targets derived in the SR-HC TMDL are not regulated through the NPDES permit, thus are not part of this proposed permit.
Other items of note include the designation of the Hells Canyon Dam as having anadromous fish passage (RM 260-188). This only occurs with the use of a trapping system at the dam for collection of anadromous fish for hatchery stocks and upstream "put and take" fisheries. Also, despite the designation of commercial navigation and transportation as a beneficial use from RM 260 to 188, there are no shipping locks at the dam to accommodate through passage.
Threatened and Endangered Species (T&E)
The threatened and endangered fish in the Snake River are:
• Threatened - spring and summer Chinook salmon, fall Chinook salmon, and Steelhead. Bull trout are not listed for the Snake River, although they are winter residents of the mainstem Snake River (RM 272.5- 188), because they spawn and rear in the tributaries.
• Endangered - Sockeye salmon. This anadromous fish is listed for the Snake River, but not in the SR-HC reach. Due to its migration habits, the fish are listed fromth e Columbia River to the Salmon River, which enters the Snake River about 60 miles downstream fromth e Hells Canyon Dam. pH
The parameter pH measures the hydrogen ion activity in water. Acidity increases as the pH falls from 7 to 0, alkalinity increases as pH rises from 7 to 14, and pH 7 is neutral. A pH range of 7 to 9 units was established as a target in order to support designated aquatic life beneficial uses within the TMDL reach. The salmonid rearing/cold water aquatic life beneficial use designation and the associated pH targets apply to the mainstem Snake River (RM 409-188) year-round. Idaho Power Company Evaluation Report Page 5 pH can be altered by industrial or municipal wastes, ammonia production when organic matter decomposes, agricultural runoff, or excessive algal growth. In this reach, pH is buffered by sodium, calcium, and magnesium salts dissolved and/or eroded from the landscape. Therefore, when pH changes occur, they are usually small.
The proposed permit limits pH to the range 6.0 to 9.0. Within the Permittee's mixing zone, the water quality standard for pH does not have to be met. It is the Department's belief that mixing with ambient water within the mixing zone will ensure that the pH at the edge of the mixing zone meets the standard, and the Department considers the proposed permit limits to be protective of the water quality standard.
Total Suspended Solids (TSS)
Total suspended solids consist of those particles held in suspension. TSS can negatively affect aquatic life by interfering with feeding behavior, damaging gills, reducing available food, reducing growth rates, smothering eggs and fry in the substrate, and damaging habitat.
TSS is a concern, because all fish life stages are listed as designated beneficial uses in the SR-HC reach. The year-round target for the entire reach is for TSS to be less than 80 mg TSS/L for acute events lasting no more than fourteen days and less than or equal to 50 mg TSS/L. The Hells Canyon Dam's outfall 004 was given a waste load allocation for TSS of 50 mg TSS/L (monthly average) and will include an allowance for background TSS. Outfalls 001-003 are considered to only discharge quantities similar to background TSS, thus no limit will be applied to them.
The July, 2003, SR-HC TMDL lists a waste load allocation of 0.25 lbs/day for the Hells Canyon Dam. This was determined to be a misprint, since the document also states that: "In cases where existing NPDES permits do not identify limits for total suspended solids (or an appropriate equivalent measure), limits will be established at no greater than 50 mg/L applied on a monthly average." The current permit does not list TSS, therefore the limit will be established as 50 mg/l.
Mercury
Elevated levels of mercury can adversely affect the aquatic biota and consumers offish, including humans. Air deposition, mining activities, and natural geologic materials are considered the primary sources of mercury in the SR-HC reach. This entire reach is listed as water quality limited for mercury.
Total recoverable water column mercury of less than 0.012 ug/L is the target for meeting water quality criteria. The maximum fish tissue mercury concentration protective for human health is 0.35 mg/kg wet weight. These targets apply year-round for the entire reach.
This is not a WLA for the wastewater discharge, rather a target applied to the Snake River. This parameter will be addressed in a future TMDL (2006), due to lack of data at this time. Sediment controls and fish consumption advisories are the current methods used to deal with mercury. If it is determined that the wastewater discharge requires a WLA for mercury, then the permit will be reopened to add the limit.
Nutrients/Nuisance Algae
Excessive nutrients, particularly nitrogen and phosphorus, can result in direct effects such as increasing nuisance algae and periphyton growth, or in indirect effects such as lowering DO, increasing methylmercury production, elevating pH, creating cyanotoxins from cyanobacteria production, increasing trihalomethane production, and increasing maintenance of domestic water supplies. Cyanobacteria tend to increase where low nitrogen Idaho Power Company Evaluation Report Page 6 concentrations inhibit the growth of other species and have been seen to dominate in the SR-HC system. Phosphorus appears to be the excess nutrient in these aquatic environments, and its sources include certain rock types, fertilizers, and sewage and septic wastes. To be protective of beneficial uses, the chlorophyll a target for the entire reach from May to September was set at 14 ug/L mean growing season limit and phosphorus was set at 0.07 mg total phosphorus/L.
This is not a WLA for the wastewater discharge, rather a target applied to the Snake River. The dam's wastewater discharge is not a source of phosphorus. Appropriate best management practices and source control were listed in the SR-HC TMDL as ways to control phosphorus from Hells Canyon Dam. Thus, no limit for phosphorus will be added to this permit.
Temperature
Stream temperatures are generally rising throughout the state and many streams violate applicable temperature criteria during the summer season. As a result, point source dischargers are required to address thermal discharges, in addition to chemical and biological discharges. Many discharge permits, including the proposed permit, identify maximum allowable discharge temperatures. Because streams in the SR-HC sub-basin are among those that are water quality limited for temperature, the Departments of Environmental Quality from Oregon and Idaho prepared the SR-HC TMDL document. In the process, the Department calculated WLAs for the permittee and other point source dischargers in the sub-basin.
Hells Canyon Dam is the only permitted point source discharger to the downstream segment of the Snake River (RM 247-188) that is listed in the SR-HC TMDL. In the TMDL, the mainstem Snake River is designated to have salmonid spawning (RM 247-188) and rearing (RM 409-188). Since adoption of the Snake River TMDL, OAR 340-041 was revised, further identifying fish use designations for the river. According to OAR 340-041-0151, Figure 151A, the Snake River's fish use designation is migration corridor, which means that the seven-day-average maximum temperature of the Creek may not exceed 20° C (68° F).
The TMDL states that salmonid spawning occurs from October 23rd to April 15th and is required to have a water temperature target of less than or equal to 48 °F (9 °C) daily average and 55 °F (12.8 °C) daily maximum (when and where salmonid spawning occurs), if and when the site potential is less than 48 °F (9 °C) daily average and 55 °F (12.8 °C) daily maximum. If and when the site potential is greater than 48 °F (9 °C) daily average and 55 °F (12.8 °C) daily maximum, the target is no more than a 0.25 °F (0.14 °C) increase from anthropogenic sources. Also, OAR 340-041-0151, Figure 15 IB, shows that the designated salmon and steelhead spawning use period is October 23 through April 15, in which time the seven-day-average maximum temperature of the Creek may not exceed 13.0° C (55.4° F).
Cold water aquatic life and salmonid rearing requires water temperatures of 64 °F (17.8 °C) (expressed in terms of a 7-day average maximum temperature) if and when the site potential is less than 64 °F (17.8 °C). If and when the site potential is greater than 64 °F (17.8 °C), the target is no more than a 0.25 °F (0.14 °C) increase from anthropogenic sources. This target applies year-round, with the critical time period being from June through September.
When aquatic species listed under the Endangered Species Act are present and if a temperature increase would impair the biological integrity of the Threatened and Endangered population, then the target is no greater than 0.25 °F (0.14 °C) increase from anthropogenic sources. In accordance with 340-04l-0028(12)(b)(B), waste load and load allocations will restrict all NPDES point sources and nonpoint sources to a cumulative increase Idaho Power Company Evaluation Report Page 7 of no greater than 0.3° C (0.5° F) above the applicable criteria after mixing in the water body and at the point of maximum impact.
The current permit includes a limit for temperature not to exceed background plus 10 °F for outfalls 001-003. The effects of temperature in the current mixing zone were evaluated using CORMIX-GI 4.2. The inputs included modeling the outfalls as a multi-port diffuser to represent discharges 001-004, using river flow data from the DEQ website, and running a scenario for the water quality temperature criteria of 13 °C for spawning season and 18 °C for the rearing and migration season. The results indicate that mixing occurs rapidly due to the volume of the receiving water. Near the edge of the mixing zone (at 100 feet downstream of the discharges), the temperature is estimated to be 18.06 °C and 13.10 °C, thus meeting the requirement of a no measurable increase of 0.14 °C for the rearing and spawning seasons, respectively.
The current temperature limit, which does not allow the discharge temperature to exceed background plus 10 °F (5.5 °C), will be further refined to include a temperature limit of 55 °F (12.8 °C) when the background river temperature is 45 °F (7.2 °C) or less. When the background river temperature is higher than 45 °F (7.2 °C), then the discharge temperature may not exceed background by more than 10 °F (5.5 °C).
Groundwater
Based on the Department's current information, this facility has a low potential for adversely impacting groundwater quality. Therefore, Schedule D of the proposed permit states that no groundwater evaluations will be required during this permit cycle.
Permit History
This section summarizes the Department's permit actions that have occurred to date.
Effective Date Action
November 23, 1987 Permit issuance. The permit was for a dam constructed in 1967. The wastewater was permitted to discharge from 5 outfalls: 001-003 for cooling wastewater, 004 for sump wastewater, and 005 for sanitary wastewater. Expiration date: November 30, 1992.
May 23, 1995 Permit renewal. Permitted discharges remained unchanged from the previous permit. For the sanitary wastewater discharge, mass load limits were included. Expiration date: April 30, 2000.
January 10, 2000 Permit renewal. The sanitary wastewater discharge outfall (005) will be changed in the proposed permit from discharging to the river to discharging to a holding tank. The Snake River TMDL was completed and the Oregon 303(d) listed pollutants for RM 260-188 are temperature and mercury. The application requested an increase in the wastewater discharge flows. An Anti-degradation Review was not required, because there will be no measurable increase in pollutants discharged to the receiving stream (see Anti-degradation section). A new waste load allocation will be added to the permit for TSS and temperature. Idaho Power Company Evaluation Report Page 8
Compliance History
This facility was last inspected on August 5, 2003. Installation of a holding tank without prior plan approval was the only violation noted during the inspection. The monitoring reports for this facility were reviewed for the period since the current permit was issued, including any actions taken relating to effluent violations. The permit compliance conditions were reviewed along with all inspection reports for the same period. Based on this review, the following violations have been documented at this facility during the term of the current permit.
Date of Violation Type of Enforcement Action Description of Violation October 1,2000 Notice of noncompliance (ERP-01-022) Total flows exceeded permit limit. The permittee attempted to reduce the flows to meet the permit limits. August 13, 2003 Notice of noncompliance (ERP-03-057) Flow, temperature, pH, & fecal exceedences; incomplete and late DMR submittals; no DMRs submitted; holding tank plans not approved. The permittee satisfactorily addressed the violations in there corrective action plan, which was a response to the notice of noncompliance.
PERMIT DISCUSSION
Face Page
The permittee is authorized to construct, install, modify, or operate a wastewater collection, treatment, control and disposal system. The facility is permitted to discharge wastewater to the Snake River within limits set by Schedule A and the following schedules. All other discharges are prohibited.
Schedule A - Waste Discharge limitations
Flow
Flow has been increased for outfalls 001-003 to from 7.5 MGD to 9 MGD. Outfall 004 remains the same at 1.5 MGD. Outfall 005 discharges to a holding tank.
Temperature
As established above, based on the results from the CORMIX-GI 4.2 mixing zone model, the discharge should cause no measurable increase above the water quality standard. As proposed above, the current temperature limit will be refined to include a temperature limit plus the current limit where the discharge temperature is not to exceed background plus 10 °F (5.5 °C). The proposed temperature limit will be the following:
• not exceed 55 °F (12.8 °C) when the background river temperature is 45 °F (7.2 °C) or lower, or Idaho Power Company Evaluation Report Page 9
• if the background river temperature is higher than 45 °F (7.2 °C), the temperature of the discharge will be limited to an increase of no more than 10 °F (5.5 °C) above the background river.
The latter part of the limit is similar to the current permit limit which requires the wastewater to meet but not to exceed the background temperature of the river plus 10 °F (5.5 °C). The former part of the limit, specifying that the effluent discharge may not exceed 55 °F (12.8 °C), varies from this limit. This added limit is not considered degradation, because the temperature standard for spawning is 55 °F (12.8 °C).
This temperature limit will only be applied to outfalls 001-003 (as in the current permit) since the contribution of heat mainly occurs from the non-contact cooling wastewater.
TSS
The Permittee was assigned a WLA in the July 2003 SR-HC TMDL of 0.25 lb TSS/day (monthly average). As stated earlier, this was determined to be in error. The WLA assigned to the Hells Canyon Dam outfall 004 should be 50 mg TSS/L applied on a monthly average as discussed in the TMDL in section 4.0.5.6 Load Allocations. This section states that existing NPDES permits that do not identify limits for TSS, which includes the Hells Canyon Dam, shall have limits established at no greater than 50 mg/L applied on a monthly average. Therefore, the proposed permit includes the WLA of 50 mg TSS/L (monthly average) as a discharge limitation for the sump wastewater. This limit will apply as long as the reservoir (background) TSS concentration does not exceed this limit. If the background concentration is higher than the permit limit, then the background concentration will be the limit for that month when the sump sample was taken.
Oil and Grease
The permit limits the facility's discharge of oil and grease to 10 mg/l. No changes to this limit are proposed. pH
The current permit limits pH to a range of 6.0-9.0. This limit will apply when the reservoir (background) pH is within the range established by the permit limit. If the background pH is higher than the permit range, then the background pH will be the limit for that month when the sump sample was taken.
Mixing Zone and Zone of Immediate Dilution
The allowable mixing zone is that portion of the Snake River contained within a radius extending one hundred (100) feet from each point of discharge. The current mixing zone was reevaluated as a result of the new requirements in OAR 340-041. The modeling program Cormix-GI 4.2 was used to determine if the changing temperature standards affected the mixing zone.
The proposed permitted flow is 10.5 MGD, which is about 16 cfs, and the river's 7Q10 flow through the dam is approximately 5780 cfs. The proposed wastewater flow is approximately 0.3 percent of the 7Q10 river flow. Using Cormix-GI 4.2 mixing zone modeling program and this discharge and river information, the results indicate that, at the edge of the mixing zone, adequate dilution occurs for the temperature standards to be met (see temperature discussion above).
The Department believes that the beneficial uses of the receiving stream will not be affected by the discharge and this mixing zone, and that the defined mixing zone meets the criteria in the rule. Idaho Power Company Evaluation Report Page 10
Schedule B - Minimum Monitoring and Reporting Requirements
In 1988, the Department developed a monitoring matrix for commonly monitored parameters. Proposed monitoring frequencies for all parameters are based on this matrix and, in some cases, may have changed from the current permit. The proposed monitoring frequencies for all parameters correspond to those of facilities of similar size and complexity in the state.
Monthly monitoring of effluent flow and pH is required in the proposed permit. This frequency remains unchanged from the current permit. These parameters will be monitored at all the outfalls discharging to the river.
Quarterly monitoring of oil and grease is required in the proposed permit. This frequency remains unchanged from the current permit.
Annual calibration of flow and oil and grease monitoring devices will be required.
Temperature monitoring is being increased from monthly to daily to provide for greater protection of the threatened and endangered species.
Quarterly monitoring of TSS is being added to outfall 004.
Discharge monitoring reports must be submitted to the Department quarterly by the 15th day of the following month. The reports must also include all applicable equipment breakdowns.
Schedule D - Special Conditions
The proposed permit includes nine special conditions. The requirements include:
The Permittee must obtain approval prior to making changes to the current wastewater facilities.
The development and implementation of a contingency plan for the prevention and handling of spills and unplanned discharges is required.
The Permittee must have the facilities supervised by an environmental supervisor.
The Permittee must notify the Department of malfunctions in accordance with the General Conditions.
The Permittee shall not be required to perform a hydrogeologic characterization or groundwater monitoring as long as the facility is operated in accordance with the permit and there are no adverse groundwater quality impacts.
The permittee must contract with an Oregon licensed sewage disposal service to pump the holding tank. The permittee shall maintain on site a contract with the sewage disposal service for pumping of the holding tank.
The permittee shall notify the Department if they contract with a new sewage disposal service for pumping of the holding tank.
The permit will be reopened if conditions warrant. Idaho Power Company Evaluation Report Page 11
Table 1
Hells Canyon Dam 2003 Flows (MGD)
Outfall 001-003 004 6.260 0.747 7.820 0.792 6.750 0.498 7.100 0.420 7.890 0.575 5.140 1.220 5.880 0.521 7.580 0.449 4.790 0.422 8.030 0.359 6.010 0.731 7.740 0.477 4.780 0.317 6.030 0.688 7.740 0.489 7.890 0.526 8.000 0.353 7.730 0.317 5.820 1.240 6.550 1.480 6.600 0.257 6.800 0.331 6.400 0.758 7.400 0.633 7.960 0.180 8.080 0.355 4.300 0.597 Average Flow (MGD) 6.780 0.583