FACT SHEET And NPDES WASTEWATER DISCHARGE PERMIT EVALUATION

Transcription

1 FACT SHEET And NPDES WASTEWATER DISCHARGE PERMIT EVALUATION Department of Environmental Quality Northwest Region - Portland Office 2020 SW 4th Ave., Suite 400, Portland, OR Telephone: (0) PERMITTEE: USDA-Forest Service-Columbia River Gorge National Scenic Area 902 Wasco Avenue Suite 200 Hood River, OR 9701 File Number: SOURCE LOCATION: Multnomah Falls Recreation Area SOURCE CONTACT: Daniel Harkenrider Telephone Number: PERMIT WRITER: Lyle Christensen Telephone Number: PROPOSED ACTION: Renewal of a National Pollutant Discharge Elimination System (NPDES) wastewater discharge permit SOURCE CATEGORY: Minor Domestic TREATMENT SYSTEM CLASS: Level II COLLECTION SYSTEM CLASS: N/A PERMIT APPLICATION DATE: August 20, 2002 PERMIT APPLICATION NUMBER: 9819 BACKGROUND Introduction USDA-Forest Service Columbia River Gorge National Scenic Area operates a wastewater treatment facility located in Multnomah Falls Lodge, Oregon. Wastewater is treated and discharged to Columbia River in accordance with National Pollutant Discharge Elimination System (NPDES) Permit number The Permit for the facility was issued on November 28,1997 and will expire on October 1,2002.

2 Page 2 The Department received a renewal application on August 20, A renewal permit is necessary to discharge to state waters pursuant to provisions of Oregon Revised Statutes (ORS) 48B.00 and the Federal Clean Water Act. The Department proposes to renew the permit. Facility Description The Multnomah Falls Lodge was constructed in 192 as a hotel and rest stop along the scenic Columbia River highway. The Columbia River Gorge National Scenic Area operates the current facility as a restaurant, rest area and visitors center for persons passing by on the interstate freeway, driving the historic highway, visiting the falls or out for a hike along the numerous trails within the gorge. See location map below. It is estimated that nearly 2 million visitors come to this site each year. Monitoring and flow records from the wastewater facility indicate a loading rate that equates to about 144 persons each day or about 2,000 per year. This wastewater treatment facility was originally placed into operation in May of Prior to the secondary treatment plant is a 42,000 gallon septic tank that was part of (along with a drain field) the original treatment and disposal facilities for this site. Starting in the mid 1990's improvements to the visitor facilities at this recreation site resulted in the recognized need to accommodate wastewater in the future. Drain field repairs and expansion efforts had been largely unsuccessful due to the increased loadings and physical limitations of the site. The permittee applied for and received a permit to construct a new facility that would include a Columbia River discharge pipe. The major treatment process used is Activated Sludge. The engineer who designed the facility determined the average design dry weather flow. It is the estimated maximum flow during May 1 to October 1 (expressed as a daily average flow), at which the design engineer expects the treatment facility can still consistently meet all effluent limits. For this facility, the average design dry weather flow is 0,000 gallons/day. The measured dry weather flow for May 1 to October 1, since this facility was put in service, is 17,000 gallons/day. Based on the current flows, this facility is at % of organic treatment capacity. Based on the current low flows compared to the design flows, and the lack of recurring effluent violations, no expansion of the facility is needed at this time. The current actual average wet weather flow (November 1 through April 0), for the past two years, is 7000 gallons per day. The peak day flow over the past two years was almost 2,000 gallons. Treated effluent is disinfected using ultraviolet light and then discharged to the Columbia River at river mile 1.9. ' aeudi Vtoinilv-Corp OCT

3 Page As a recreation facility, this site is most heavily used during the summer months and on weekends. Wide seasonal and daily variations in flows are not unusual for this facility. The secondary treatment plant was sited at the east end of the parking area between the east and west bound freeway lanes. A photo of the plant blower / operations and maintenance building is above. Biosolids Management and Utilization Wastewater derived solids are produced in two areas at this facility. Septic primary solids are produced in the septic tank and have typically been removed twice each year by a licensed septage hauler as necessary. Waste activated sludge produced in the secondary treatment plant are held and concentrated in the aerobic digester. The secondary solids are removed to another facility for further processing as necessary. During peak flow periods, the digester must be pumped several times per month. The receiving treatment facility is responsible for ensuring compliance with the federal biosolids regulations (40 CFR Part 0) and the permit for that facility is the governing authority. This permit requires monthly reporting of the transportation of biosolids to other facilities and the submittal of an annual summary. Inflow and Infiltration (I/T) The collection system for this facility is very small and there are no indications that inflow and/or infiltration are contributing additional flow to the treatment facility. Pretreatment The permittee does not have a formal pretreatment program, nor is one required for this source. Pollutants Discharged The current permit allows USDA-Forest Service Columbia River Gorge National Scenic Area to discharge treated effluent from the wastewater treatment plant year round. The current permit sets limits on the following pollutants: Five-day Biochemical Oxygen Demand (BOD), Total Suspended Solids (TSS) and E. coli bacteria. The discharge is also regulated for ph and removal efficiency for BOD and TSS. The proposed permit will regulate the same pollutants and includes a proposed limit on temperature loading. Outfalls Treated wastewater is discharged to Columbia River. The outfall is located about 700 feet from the treatment plant and extends about 1 feet into the river. At that point the stream is estimated to be 1 to 2 feet deep. The outfall is a single port from the four inch discharge line.

4 Page 4 Receiving Streams/Impact The designated beneficial uses of the receiving stream are: public and private domestic water supply, industrial water supply, irrigation, livestock watering, anadromous fish passage and rearing, salmonid passage and rearing, resident fish and aquatic life, wildlife and hunting, fishing, boating, water contact recreation, aesthetic quality, hydro power and commercial navigation and transportation. The Columbia River is water quality limited (according to the d listings) in this reach for a number of identified parameters. These are Temperature, Total Dissolved Gas, Toxics (including PCBs, Arsenic and Pesticides) and ph. Of these, only temperature and ph will receive further discussion. In addition, the Columbia River is water quality limited for dissolved oxygen in the next adjacent reach. The discharge from this facility does not have a reasonable potential to add or contribute to any of the toxics standards violations observed. Wastewater facilities treating exclusively domestic sewage have not been recognized as a typical source of any toxics. Additionally, this facility is not a source for supersaturation of dissolved gas and will not contribute to the low dissolved oxygen downstream. Dams have been documented as the source of the dissolved gas concern. A review of monitoring results (see Attachment A) shows that this facility discharges very low levels of -day biochemical oxygen demand, which is a key measure of potential influence on stream dissolved oxygen. Temperature The applicable temperature standard for the receiving stream is a maximum of 8 F, based on a seven-day average of maximum daily temperature readings. Stream temperatures are generally rising throughout the State of Oregon and many streams violate the applicable temperature standard in the summer. Point source dischargers are required to help stop and reverse the warming trend. In order to prevent further warming, most discharge permits will identify the maximum allowable thermal discharge. The permit must also prohibit further increases. The streams in this basin are water quality limited for temperature and may not fully support the spawning and rearing of salmonid species. The proposed permit addresses the potential impact of this discharge on stream temperature. The effluent temperature at some times of the year exceed the applicable temperature standard for the receiving stream. The permittee has been monitoring and reporting effluent temperatures since March The highest temperature reported was 7 F. However, the effluent is not expected to exceed 77 F at any time. 77 F is considered to be lethal for salmonids. A Total Maximum Daily Load (TMDL) addressing the water quality limited status for temperature has not yet been approved for the sub-basin. Using conservative assumptions, it was determined that the heat associated with this discharge will not cause a measurable increase of temperature, at the edge of the mixing zone. A "measurable increase" is defined as greater than a 0.2 F increase at the edge of the mixing, factoring in the effluent temperature and dilution at the edge of the mixing zone, and using the

5 Page applicable stream temperature standard. The assumptions used were that the flow mixes with 10 cubic feet per second of the river flow (approximately 1/10000 of the 7Q10), the effluent flow is 0,000 gallons per day (about 0.0 cfs), effluent temperature is 7 F and the stream temperature is 8 F. A simple mass balance would anticipate a temperature increase of 0.02 F which is less than 0.2 F. Groundwater There are no known groundwater issues at this site. The drainfield will only be used as a temporary measure should the treatment facility have difficulty meeting the effluent discharge limitations of their permit. Stormwater Stormwater is not addressed in this permit. General NPDES permits for stormwater are not required for facilities with a design flow of less than 1 MGD. Permit History The need for this NPDES permit became apparent as increased flows and expanded operations at this recreation site led to regular problems with the large onsite system's drainfield. The remote location of this facility and regular heavy use by tourists, made it an important resource to maintain in service. An anti-degradation review must be made for the NPDES permit renewal. The proposed permit incorporates permit limits to maintain water quality standards and a temperature management plan as necessary. The proposed permit does not allow for an increase in mass load limits from the previous permit. Compliance History This facility was last inspected November 20, 2000 and was found to be operating in compliance. 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 and all inspection reports for the same period were reviewed. The only violations of the permit that were documented occurred during the initial startup of the facility. Since the startup period no further compliance issues have been noted. Therefore, this facility is considered to be operating in compliance with the current permit.

6 Page PERMIT DISCUSSION Face Page The permittee is authorized to construct, install, modify, or operate a wastewater collection, treatment, control and disposal system. Permits discharge of treated effluent to the Columbia River within limits set by Schedule A and the following schedules. All other discharges are prohibited. Schedule A - Waste Discharge limitations BOD and TSS concentration and mass limits Based on the Sandy Basin minimum design criteria, wastewater treatment resulting in a monthly average effluent concentration of 20 mg/l for BOD and TSS must be provided from July 1 - November 0. From December 1 - June 0, a minimum of secondary treatment or equivalent control is required. Secondary treatment for this facility is defined as monthly average concentration limit of 0 mg/l for BOD and 0 mg/l for TSS. The Department is proposing concentration limits at least as stringent as the basin minimum design criteria. The proposed monthly average summer BOD concentration limit is 20 mg/l with a weekly average limit of 0 mg/l. The proposed monthly average summer TSS concentration limit is 20 mg/l with a weekly average limit of 0 mg/l. The proposed monthly average winter BOD concentration limit is 0 mg/l with a weekly average limit of 4 mg/l. The proposed monthly average winter TSS concentration limit is 0 mg/l with a weekly average limit of 4 mg/l. The summer mass limits for biochemical oxygen demand (BOD) and suspended solids (TSS) are based on the design average dry weather flow (ADWF) of.0 MGD and the monthly average BOD and TSS concentration limits of 20 mg/l and 20 mg/l, respectively. The winter mass load limits for the facility are based on the design ADWF of.0 MGD and the monthly average BOD or TSS concentration limits of 0 mg/l and 0 mg/l, respectively. The limits are in accordance with OAR (9)(e). All mass load limitations are rounded to two significant figures. BOD, and TSS The limits are: (1) July 1 - November 0; Parameter BOD, TSS Average : Effluent Concei ltrations Monthly Weekly 20 mg/l 0 mg/l 20 mg/l 0 mg/l Monthly Average lb/day Weekly Average lb/day 8 8 Daily Maximum Lbs 10 10

7 Page? (2) December 1 - June 0: j Average Effluent Concentrations Parameter Monthly Weekly BOD TSS J 0 mg/l 1 0 mg/l 4 mg/l 4 mg/l Monthly Average lb/day 8 8 Weekly Average lb/day Daily Maximum Lbs 1 1 Calcula tions: (1) Summer BOD (a) (b) (c).0 MGD x 8.4 #/gal x 20 mg/l monthly avg. = lbs/day lbs/day monthly avg. x 1. = 8 lbs/day weekly avg. lbs/day monthly avg. x 2.0 = 10 lbs/day daily max. (2) Summer TSS (a) (b) (c).0 MGD x 8.4 #/gal x 20 mg/l monthly avg. = lbs/day lbs/day monthly avg. x 1. = 8 lbs/day weekly avg. lbs/day monthly avg. x 2.0 = 10 lbs/day daily max. () Winter BOD (a) (b) (c).0 MGD x 8.4 #/gal x 0 mg/l monthly avg. = 8 lbs/day 8 lbs/day monthly avg. x 1. = 11 lbs/day weekly avg. 8 lbs/day monthly avg. x 2.0 = 1 lbs/day daily max. (4) Winter TSS (a) (b) (c).0 MGD x 8.4 #/gal x 0 mg/l monthly avg. = 8 lbs/day 8 lbs/day monthly avg. x 1. = 11 lbs/day weekly avg. 8 lbs/day monthly avg, x 2.0 = 1 lbs/day daily max. A review of recent monitoring data (see Attachment A) indicates the City should generally be able to comply with the permit limits. No changes from the previous permit are proposed. BOD and TSS Percent Removal Efficiency A minimum level of percent removal for BOD and TSS for municipal dischargers is required by the Code of Federal Regulations (CFR) secondary treatment standards (40 CFR, Part 1). An 8 percent removal efficiency limit is included in the proposed permit to comply with federal

8 Page 8 requirements. An examination of the DMR data indicates the permittee will have little difficulty meeting the limit with the current facilities. ph The Sandy Basin Water Quality Standard for ph is found in OAR l-048(2)(d). The allowed range is 7.0 to 8. in the Columbia River. The proposed permit limits ph to the range.0 to 9.0. This limit is based on Federal wastewater treatment guidelines for sewage treatment facilities, and is applied to the majority of NPDES permittees in the state. Within the permittee's mixing zone, the water quality standard for ph does not have to be met. It is the Department's experience that mixing and buffering 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. It is also anticipated that with the minimal nutrient additions to the stream from this facility, it is unlikely that Multnomah Falls Lodge STP will cause or contribute to eutrophication which could influence the observed ph in the receiving stream. Bacteria The proposed permit limits are based on an E. coli standard approved in January 199. The proposed limits are a monthly geometric mean of 12 E. coli per 100 ml, with no single sample exceeding 40 E. coli per 100 ml. The new bacteria standard allows that if a single sample exceeds 40 E coli per 100 ml, then the permittee may take five consecutive re-samples. If the log mean of the five re-samples is less than or equal to 12, a violation is not triggered. The resampling must be taken at four hour intervals beginning within 28 hours after the original sample was taken. The proposed effluent limits are achievable through proper operation and maintenance. Disinfection The treatment facility uses ultra-violet light to disinfect the treated wastewater. No chlorine or chlorine compounds may be used for disinfection purposes and no chlorine residual will be allowed in the effluent due to chlorine used for maintenance purposes. The UV disinfection process must be monitored on a daily basis for transmittance and UV intensity. Temperature A thermal load limit for the effluent is proposed. It is based on the maximum thermal discharge that is expected to occur during the summer, with the existing design flow and effluent temperatures. The thermal load limit was calculated using the average dry weather design flow and the degrees Fahrenheit that the maximum expected weekly average of daily maximum effluent temperature exceeds the applicable stream temperature standard, as follows:

9 Page 9.0 DADWF (MGD) x 1,000,000 x 8.4 #/gallon x (7.0 maximum effluent temperature in F - 8 applicable standard in F) = 1,71, BTUs/day Mixing Zone and Zone of Immediate Dilution OAR (4) allows the Department to designate a portion of the receiving stream to serve a zone of dilution for treated wastewaters and receiving waters to mix. Within the mixing zone, the Department may suspend all or part of the water quality standards, or set less restrictive standards provided a number of conditions defined within the rule are met. The rule also allows the Department to designate a Zone of Immediate Dilution (ZID) on a case-by-case basis. The allowable mixing zone is that portion of the Columbia River within fifty (0) feet of the discharge. The Department believes that the beneficial uses of the receiving stream will not be affected by this discharge outside this mixing zone and that the defined mixing zone meets the criteria in the rule. A ZID (where acute toxicity may occur) is not defined or considered necessary for this facility. Emergency Overflows There are no designed emergency overflow points in the treatment and disposal system. The facility can discharge to the abandoned drainfield if effluent cannot meet stream discharge requirements. 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. The permittee is required to have a laboratory Quality Assurance/Quality Control program. The Department recognizes that some tests do not accurately reflect the performance of a treatment facility due to quality assurance/quality control problems. These tests should not be considered when evaluating the compliance of the facility with the permit limitations. Thus, the Department is also proposing to include in the opening paragraph of Schedule B a statement recognizing that some test results may be inaccurate, invalid, do not adequately represent the facility's performance and should not be used in calculations required by the permit. Monitoring for E. coli must be performed in accordance with one of the methods approved by the Department. The UV disinfection process must be monitored on a daily basis for transmittance and UV intensity. Daily monitoring of influent and effluent flow is required in this permit. In addition, calibration of the flow meter is required on a regular basis.

10 Page 10 Temperature monitoring of the effluent is required. In addition, the permittee will be required to calculate the weekly average temperature of the effluent and the weekly thermal load discharged. Monitoring may be waived for certain months after two full years of monitoring are completed, provided the following condition is met: No single daily effluent temperature in that month for the past two years has exceeded the applicable stream temperature criteria. The streams in this basin are water quality limited for temperature and may not fully support the spawning and rearing of salmonid species. This discharge has a reasonable potential to contribute heat to the water quality limited sections. Therefore, the Department is proposing to include stream monitoring for temperature. A monitoring sites should be located just upstream of the point of discharge. If a continuous monitor is installed for the stream monitoring, then the device must be audited (field checked for accuracy of temperature readings) in June and September, and visually checked each month to insure that the device is still in place, and still submerged. An annual report summarizing the weekly averages of the maximum daily temperature readings is required for the temperature data, for the effluent and the stream monitoring site. Monitoring may be waived for some months after two full years of monitoring, providing that no weekly effluent values exceed the applicable stream temperature criteria for that month. Discharge monitoring reports must be submitted to the Department monthly by the 1th day of the following month. The monitoring reports need to identify the principal operators designated by the Permittee to supervise the treatment and collection systems. The reports must also include records concerning application of biosolids and all applicable equipment breakdowns and bypassing. Schedule B of the permit includes the requirement for the submittal of annual reports. The condition has standard language requiring an annual report on transporting sludge to another facility. Schedule C - Compliance Conditions The proposed permit includes no compliance conditions with compliance deadlines. Schedule D - Special Conditions The proposed permit includes four special conditions. The requirements include: A temperature management plan has been written for this facility. Schedule D includes a permit condition requiring the permittee to implement the provisions of the approved Temperature Management Plan. The Department has included a limit on thermal load in Schedule A that identifies the currently permitted amount of thermal energy over and above the temperature standard that may be discharged. The Department is proposing to include a prohibition against increasing thermal discharges beyond the currently permitted amount. That prohibition can be found in Schedule D.

11 Page 11 The permittee must have the facilities supervised by personnel certified by the Department in the operation of treatment and/or collection systems. Schedule D includes a condition requiring the development and implementation of a contingency plan for the prevention and handling of spills and unplanned discharges. Schedule F - General Conditions The General conditions include sections containing permit language specified as Standard Conditions, Operation and Maintenance of Pollution Controls, Monitoring and Records, Reporting Requirements and Definitions.

12 Multnomah Falls Lodge STP Prepared by Lyle Christensen 11/4/2002 Attachment A month/vear Influent flow temperature BOD TSS max dav averaae max averaae Effluent temperature BOD TSS" max dav Averaae Sep-02 Aug-02 Jul-02 Jun-02 May-02 Apr-02 Mar-02 Feb-02 Jan-02 Dec-01 Nov-01 Oct-Ot Sep-01 Aug-01 Jul-01 Jun-01 May-01 Apr-01 Mar-01 Feb-01 Jan-01 Dec-00 Nov-00 Oct-00 Sep-00 Aug-00 Jul-00 Jun