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HomeMy WebLinkAbout9 - Update on Water Quality Studies, Regulations and Permitting CITY OF BOLILDER WATER RESOURCES ADVISORY BOARD AGENDA ITEM MEETING DATE: January 12, 2009 AGENDA TITLE: Update on Water Quality Studies, Regulations and Permitting PRESENTERS: Bret Linenfelser, Water Quality Coordinator Chris Douville, Coordinator of Wastewater Treatment EYECUTIVE SUMMARY: The Water Quality and Environmental Services (WQES) Group and the Wastewater Treatment Group are working jointly on various water quality studies to address curY•ent and future regulations. These regulations affect both the 75~' Street wastewater treatment facility (WWTF) discharge permit and the city of Boulder Municipal Separate Storm Sewer System (MS4) permit. C?ver the past few years the WWTF has experienced sporadic exceedances of copper effluent limits and special studies have been initiated to develop site-specific copper water quality standards for Boulder Creek. In 2008, nitrogen modeling was completed in the Boulder Creek and St. Vrain Creek basins to update the 2003 ammonia total maximum daily load (TMDL). The update addressed new state-wide ammonia water quality standards and a new ammonia model. In January 2008, the 75~' Street WWTF Colorado Discharge Permit System (COPS) discharge permit expired and was administratively extended by the Colorado V4'ater Quality Control Division (Division). A COPS permit renewal application was submitted to the Division in August 2007. Additionally in 2008, WQES staff were actively involved in various Division Work Groups and water quality studies to address new regulatory requirements and water quality standards for temperature, nutrients, bacteria (E. coli), nonylphenol and emerging contaminants. All of these efforts are linked together with the results of special studies and Work Group participation helping to support the 75~' Street WWTF COPS permit renewal process, the city's MS4 stormwater permit, and help the city of Boulder plan for future regulatory impacts. COMMUNITY SUSTAINABILITY ASSESSMENTS AND IMPACTS: Economic: Non-compliance with state or federal regulations and the exceedance of a WWTF effluent limits can result in result in fines up to $27,000 per day, per violation, from the state regulating agency. Future WWTF effluent limit requirements, or stormwater permit requirements, could require additional wastewater and stormwater capital improvements and long-term operation and maintenance costs. To address current and future regulatory requirements, fees for consultants may be required to cover areas of expertise not available through city staff. AGENDA ITEM # 9 PAGE i Environmental: The exceedance of W WTF effluent limits can impact the health of Boulder Creek aquatic life by increasing the concentration of regulated constituents above the regulatory level set to protect aquatic life or human health. Improved water quality can enhance the aquatic community in Boulder Creek. Social: Social benefits to the community can be achieved through continued improvement in water quality and the protection of public and environmental health, which provide improved quality of life. OTHER BOARD AND CO117MISSION FEEDBACK: A water quality study, regulatory and permitting update has not been provided to WRAB members in recent years. General updates on improvements to the city's WWTF and an update on the draft Water Quality Strategic Plan were provided to the WRAB in 2008. PUBLIC' FEEDBACK: None. STAFF RECOMILZENDATION: Staff is looking for comments from WRAB on current water quality projects and firture regulations. ANALYSIS: «'ater Quality Studies Water Quality and Environmental Services and V4~astewater Treatment staff have been working jointly on multiple water quality studies to address current and future regulations and address sporadic non-compliance with WWTF effluent limits and water quality standards. Current water quality studies are summarized below. (1) CoAUer Study Copper discharges from the 75th Street WWTF are regulated through the CDPS permit. Potentially dissolved (PD) copper effluent limits first became effective at the 75th Street WWTF on June 1, 1993 and extended through January 2003, under the previous CDPS permits. Potentially dissolved copper limits were as follows: • Through June 30, 1995: "Report only" for 30-day average and daily maximum • Beginning July 1, 1995: 25.6 ug/L 30-day average; 35.2 ug/L daily maximum Potentially dissolved copper effluent limits continued with the current CDPS permit, which became effective February 1, 2003 and expired January 31, 2008. Potentially dissolved copper effluent limits are as follows: • Through December 31, 2005: 25.6 ug/L 30-day average; 35.2 ug/L daily maximum • Beginning January 1, 2006: 18.0 ug/L 30-day average; 26.0 ug/L daily maximum AGENDA ITEM # 9 PAGE 2 The above mentioned PD effluent limits are based on the old WWTF design capacity of 24.5 million gallons per day (mgd). Based on the current V4~WTF design capacity of 25 mgd, the 18.4 ug/L 30-day average and 26.0 ug/L daily maximum will be further reduced. Based on historical final effluent PD copper concentrations, the 75th Street WWTF is not able to achieve consistent compliance with the effluent limits. Historical (March 2443 through October 2448) 34-day effluent PD copper concentrations range from 14.2 ug/L to 48.7 ug/L, and the daily maximum has exceeded 57 ug/L. To address non-compliance with the PD copper effluent limits, the City implemented amulti- pronged approach that included an evaluation of the following: ? Current copper control strategies ? Possible non-controllable copper sources ? Potential to develop asite-specific copper chronic water quality standard Copper Control Strate~~_ The city of Boulder implemented multiple copper control strategies to address copper effluent limit non-compliance prior to implementing water quality studies to develop site-specific copper water quality standards. Pretreatment Pro6ram. The City's pretreatment program regulates permitted industrial users through local pollutant limitations, set on a loading basis, for copper and other constituents. Currently, local limits for copper are set to a total maximum allowable industrial loading of 5.36 pounds per day. This loading is allocated to industries based on flow and historical discharge characteristics. Influent copper loadings to the WWTF have remained consistent since 2441. No significant increase or decrease in the total copper annual average loading to the WWTF has been measured based on loadings calculated on a weekly basis. The current City local limits for copper were approved in 2444 and determined that additional reductions (beyond those made in 2444) in copper discharges from regulated industries would be impractical as most facilities are currently regulated at or near instream background concentrations. Corrosion Control Pro6ram. The finished drinking water corrosion control program was evaluated to determine if modifications could be made to address possible leaching from copper pipes. The current program focuses on decreasing the rate of, or preventing, corrosion of copper water pipe through the chemical characteristics of the finished water. A review of recent City studies indicated that copper leaching may only be an issue in newer copper piping in the City, which is minimal in comparison to the City's total copper water piping. It was determined that the current corrosion control program meets City corrosion control goals and objectives, which includes the control of copper leaching through methods such as pH control and chemical addition. Couuer Based Root Control and Public Awareness. Multiple local businesses were contacted to determine what quantities, if any, of copper based root killers were sold on an annual basis in the City. The assessment indicated that accurately quantifying copper based root killer use in the City was difficult since many City residents work and shop outside the City and have the potential to purchase copper based root killer products outside of the City. In addition, some local Boulder businesses have stopped selling AGENDA ITEM # 9 PAGE 3 copper based root killers and now promote alternative root control products that do not contain copper. To address public awareness about the impacts of copper based root killers the City developed a Utility Flyer, which was sent to utility customers in December 2005. The Flyer focused on educating residents and businesses that copper based root control products can cause problems at the wastewater plant and alternative root control methods are available. The City also has a residential and business focused monitoring program for copper (as well as other constituents) that is implemented through the City's Pretreatment program. This program allows the City to identify areas of high copper contributions to the sanitary sewer system and complete further source evaluations if necessary. The results of each of these evaluations indicates that further reductions in copper loading to the W WTP from local permitted industries is not likely, or consistently quantifiable. Some reduction in copper loading may result from heightened public awareness but quantifying and ensuring consistent reductions is difficult. Site-Specific Copper tiVater Quality Standards Development. Based on the limited ability to further and consistently reduce copper contributions to the WV4~TF, the City evaluated the potential to develop site-specific copper standards for Segment 9 of Boulder Creek and development of asite-specific W WTF effluent limit. Two copper water quality studies have been implemented that will reflect the site-specific water quality conditions in Boulder Creek that may mitigate copper toxicity. A work plan for both studies has been presented to the Division and study updates have been provided to the Region 8 Enviromnental Protection Agency (EPA) and Division during 2007 and 2008 Hearings. Biotic Li~and Model. Based on discussions with the Division in 2005 it was determined that use of the Biotic Ligand Model (BLM) was an acceptable method for modifying copper standards and has been applied to other receiving waters in the state. The BLM is a nationally recognized water quality model used to develop site-specific water effect ratios (WERs) for receiving waters. Calculated WERs are applied as a multiplier to the current receiving water copper water quality standard, such as the current table value standard applied to Segment 9 of Boulder Creek. From August 2005 through December 2006, Boulder Creek water quality samples were collected and analyzed for 11 parameters to support the use of the BLM. A t~'ER was calculated based on the BLM and results were presented to the Division and Colorado Water Quality Control Commission (Commission) in preparation for the June 2007 South Platte Basin Hearing. Prior to the June 2007 Hearing, the Division and the EPA expressed concerns over the application of the BLM in Colorado and requested the city of Boulder, and multiple other entities proposing to use the BLM, consider alternative options for developing asite-specific copper water quality standard, or effluent limit, while the EPA and Division re-evaluate the use of the BLM in Colorado. At the recommendation of the EPA and Division, the city of Boulder, and other entities, agreed to evaluate the development of a copper translator following EPA guidance. The translator could be used in place of the BLM if the EPA and Division do not reconcile AGENDA ITEM # 9 PAGE 4 issues identified with the BL1V1. The city of Boulder agreed to pursue developing a copper translator for the 75th Street WWTF. Upon this agreement, the Commission granted the city a Temporary Modification for copper which allows the 75th Street WWTF to discharge copper under "current conditions" through the end of 2009. Current condition is defined as the current concentration of copper, even if it exceeds the old or proposed effluent limit, so long as the City does not allow substantial additional copper loads to the sanitary sewer system from industry, or other permitted sources. Copper Translator. In August 2007, the City initiated copper monitoring in Boulder Creek to support the development of asite-specific copper translator for the 75th Street WWTF. Samples are collected twice per month in Boulder Creek and the WWTF effluent and analyzed for total copper, dissolved copper and potentially dissolved copper. It is anticipated that copper sampling will continue in to early 2009. To date, the results of the copper translator study indicate that a 1.45 multiplier could possibly be applied to the current, and future, 75th Street WWTF copper effluent limits. This would provide an approximate 45 percent increase in copper effluent limits, both acute and chronic. The Division has indicated that the results of the translator study will be used during the 75th Street W WTF CDPS permit renewal process, ~~vhich is anticipated to occur in 2009. Currently, it is not known what method the City will utilize to develop site-specific copper water quality standards or site-specific effluent limits. In an October 2008 meeting with EPA and the Division, both agencies presented results of revisions to the BLM that were implemented to address concerns with the previous version of the BLM. The City has hired a consultant to evaluate the revised BLM and anticipates preliminary results by March 2009. At that time, the City will evaluate the best option for increasing the allowable concentration of copper discharged from the 75th Street W WTF, either through a BLNI-based site-specific copper standard or a translator-based site-specific copper effluent limit. Either option will meet state and federal requirements for the protection of aquatic life in Boulder Creek from copper discharges. (2) Water Temperature Stud~~ In 2006, the Division proposed changes to statewide water temperature standards. A more restrictive and complex set of temperature standards were adopted by the Commission in the Colorado Basic Standards and Methodologies for Surface Water. The Division will evaluate receiving water temperature data and determine whether discharges, such as treated effluent fiom wastewater treatment facilities, should have a lower effluent temperature to protect aquatic life (recognizing that temperature variations result from natural conditions and irreversible human impacts). Possible implications for Boulder include the need for cooling towers or refrigerated chillers to cool effluent from the 75th Street WWTF. In November 200b, the City initiated the collection of Boulder Creek and 75th Street WWTF effluent temperature data to evaluate compliance with the new temperature water quality standards. Data have been collected at one hour intervals with over 18,000 temperature measurements collected to date. Temperature data are collected at two locations in Boulder Creek, directly upstream of the 75th Street WWTF outfall, and at the end of the chronic mixing AGENDA ITEM # 9 PAGE 5 zone, approximately 234 feet below the outfall. Temperature data are also collected at the WV4~TF effluent outfall. To date, preliminary Boulder Creek temperature data show occasional exceedances of the acute and chronic temperature standards of 28.6 Deg. C. and 26.8 Deg. C., respectively, at the upstream (above the WWTF outfall) site (see Attachment A). On dates where the upstream temperature in Boulder Creek exceeds one of the temperature standards, the standards are met below the WWTF outfall, indicating a cooling effect from the WWTF effluent. Historic temperature data were submitted as part of the CDPS permit renewal effort in 2007 and will be evaluated by the Division as part of the CDPS permit renewal. It is possible that a monitoring only requirement will be in the next CDPS permit if data continue to show compliance with temperature standards. (3) E. tali Bacteria Study In 2006, some segments of Boulder Creek near downtown Boulder were listed on the state's 303(d) list as impaired due to exceeding the Esche~ichia tali (E. cold stream standards. In addition to the 303(d) listing, the Division proposed developing a total maximum daily load (TMDL) for Boulder Creek which would require identification of the E. tali source(s) and develop E. tali load allocations to limit the input of E. tali to Boulder Creek and get Boulder Creek in compliance with the water quality standard of 126 organisms per 100 ml. E. tali is a bacteria used as an indicator of the possible presence of pathogenic (disease-causing) bacteria, viruses, and protozoa from sewage contamination. Since it is difficult, time-consuming, and expensive to test directly for the presence of a large variety of pathogens, water is tested for E. tali instead. However, recent studies have indicated that E. tali may not be a good indicator of pathogens, because a number of strains thrive in the environment of soils and natural waterways, unlike the pathogens they are intended to indicate. The city is currently working with the state to identify the sources of E. tali and other indicators to determine the relative health risk in Boulder Creek. The primary objectives of the study are to: • Determine and minimize the level of human contamination, and thus threat to human health within the urban corridor of Boulder Creek • Identify affected stream segments and sources (e.g. specific stormwater outfalls) • Evaluate the persistence of E. tali within the environment. • Examine the relationship between levels of human contamination (the presence of wastewater constituents) and the persistence of E. tali within the environment. • Develop a practical "matrix" or "toolbox approach" to determine the level of human contamination. AGENDA ITEM # 9 PAGE 6 Possible implications of the E. tali TMDL include: • All permitted dischargers will be asked to incorporate the TMDL requirements into their MS4 permit. • Monitor outfalls and streams. • Identify sources of E. tali and determine the source (location, type -human, animal). • Identify and implement control measures, or Best IVlanagement Practices, to control E. coll. • Meet the numeric E. tali standard of 126/100m1s at the end of all stortnwater outfalls, prior to discharging to Boulder Creek. The E. tali TIVIDL is anticipated to be final in 2009. Water Quality and Environmental Services staff are currently «~orking with the Division and EPA on final TMDL development and implementation. (4) Nitrogen Study As part of the 75th Street WWTF CDPS permit renewal process in 2002, the Division required an ammonia TMDL be completed for Boulder Creek and the St. Vrain Creek basin to address excesses of ammonia. The TMDL was completed in 2003, and ammonia effluent limits were incorporated into the CDPS discharge permit. In 2007 the Commission adopted more restrictive state-wide ammonia water quality standards and implemented a new model to calculate WWTF effluent limits for ammonia. Substantial improvements at the 75th Street W WTF were implemented to prepare for the TMDL-based ammonia standards, and the possible implementation of nitrate and/or total nitrogen effluent limits. Additional Boulder Creek ammonia and nitrogen modeling was completed in 2008, building on the 2003 modeling effort. Results were submitted to the Division in mid 2008. Results of the nitrogen modeling effort indicate that monthly ammonia effluent limits (acute and chronic) are substantially lower than current limits for specific months and require enhanced nitrogen removal at the 75th Street WV4~TF. In anticipation of future nitrate effluent limits, nitrate was also evaluated as part of the 2008 nitrogen modeling. New ammonia effluent limits and potential nitrate effluent limits, should they be implemented, are shown in Attachment B. In early 2009, with assistance from a consultant the City will evaluate the ability of the t?VWTF to meet the new, lower ammonia effluent limits, and possible nitrate effluent limits. (5) Endocrine Disrupting Compound (EDC) Study In 2001, researchers from the CL1 Department of Integrative Physiology and Colorado Division of Wildlife (DOW) began to examine fish in Colorado streams at points upstream and downstream of municipal WWTF effluent discharges in Denver (South Platte River), Colorado Springs (Fountain Creek), and Boulder (Boulder Creek). White suckers (~`atostotnus cornmersoni) were collected by electroshocking, and intersex fish were observed in Boulder Creek below the 75th Street WWTF, but not at upstream reference sites. In subsequent samplings researchers observed intersex fish at the sites below effluent discharges but never at upstream reference sites. In addition, sex ratios downstream were skewed toward females. In AGENDA ITEM # 9 PAGE 7 Boulder Creek below the 7th Street WWTF discharge, sex ratios for white suckers were skewed toward females almost 5:1 while numbers were fairly equal upstream of the WWTF. Additional effects on the ovaries and testes of fish at the sites downstream of effluent discharges suggest reduced reproductive competency compared to fish at the reference sites. In order to further explore the relationship between the endocrine-activity of the 75th Street WV4~TF effluent and the reproductive disruption observed in downstream white suckers, experiments were conducted by CU where fish were exposed to the WWTF effluent under controlled conditions. A fish exposure mobile (FEM) was designed in a mobile trailer (provided by DOW), and deployed at the 75t~' Street WWTF to conduct exposures of fish to effluent and Boulder Creek reference water. Adult male fish exposed to 75th Street WWTF effluent were rapidly feminized and demasculinized consistent with exposure to exogenous estrogenic wastewater contaminants. Effluent-exposed males exhibited reductions in the expression of secondary sexual characteristics, gonadal sperm abundance, and elevated plasma concentrations of the yolk-precursor protein vitellogenin. Chemical analyses of the W WTP effluent and Boulder Creek water indicated the presence of a number of estrogenic compounds downstream of the W WTP as well as in the effluent itself. A 50 consecutive day study was conducted by CU in late 2008 and the results should be available in mid 2009. Pharmaceutical Take-Back Day. In addition to human waste that goes to the WWTF, the disposal of pharmaceuticals is also a source of EDCs and other emerging contaminants, and has the potential to be controlled at the source. Nationally, it is common practice that excess pharmaceuticals are dumped down the drain, which occurs both in the home and in businesses. In addition, impacts have been identified from the use of personal care products (PCPs) that make their way down the drain either during use or disposal of excess product. In October 2008, Water Quality and Environmental Services staff, in conjunction with Partners for a Clean Enviromnent (PACE), organized a pharmaceutical Take-Back Day at the Boulder Community Hospital Foothills Campus. During the one day event approximately 300 people dropped off excess pharmaceuticals and 300 pounds of pharmaceuticals were collected and properly disposed of. The City plans on having additional take-back events, including 2009. (6) Nonylphenol Study. In 2006, EPA published final aquatic-life chronic criteria for nonylphenol, an organic compound that is a product of industrial synthesis, particularly in making detergents. The EPA freshwater chronic criteria is 6.6 ug/L and an acute criteria is 28.0 ug/L. As part of the 2007 Commission Hearing on Consideration of Revisions to Statewide Qrganic Chemical Standards in the Basic Standards and Methodologies for Surface T~ater, Regulation #31 and in the Basic Standards for Groundwater, Regulation #41, as hell as Other Proposed Revisions to Regulation #41, the Commission adopted the EPA nonylphenol criteria. As part of the Commission hearing process, meeting these standards was deferred through 2009 to allow dischargers time to evaluate the following: approvable analytical procedures for measuring nonlyphenol and its parent compounds; sources of nonylphenol; the ability to limit nonylphenol sources; and, measures of the level of nonylphenol in Wy~4'TF effluent to determine the ability to comply with the adopted criteria. The city of Boulder is in the process of collecting data on nonylphenol and its parent compounds to characterize sources. The City has been an AGENDA ITEM # 9 PAGE 8 active participant with other Colorado dischargers on developing an approval analytical method for nonylphenol and characterizing nonylphenol sources. Currently, the Metro Wastewater Reclamation Facility laboratory is leading the effort to develop an approvable nonylphenol analytical method. These efforts will need to continue through 2009. (7) Nutrient Standards Study. In 2002 the Division released their Nutrient Criteria Development Plan for the development and implementation of nutrient criteria in Colorado. Over the past six years the Division has been working towards developing nutrient criteria for nitrogen, phosphorus and chlorophyll a. Algae, measured as chlorophyll a, has been identified as the primary indicator for evaluating the health of lakes and reservoirs. The Division is also evaluating the relationship between chlorophyll a and nitrogen and phosphorus concentrations. If impairment due to elevated chlorophyll a levels is identified some level of control for nitrogen and/or phosphorus contributions, from point and non-point sources, will be required by the Division. For streams and rivers, the Division is focusing on controlling nitrogen and/or phosphorus contributions based on the health of the aquatic community, specifically macroinvertebrates. This process looks at the relationship between nutrient concentrations and macroinvertebrate populations and diversity. In 2008, the City began working with Timberline Aquatics, who has been the City's consultant for the collection and identification of macroim~ertebrates in Boulder Creek for the last 8 years. Timberline Aquatics is evaluating the potential effects of nutrients (nitrogen and phosphorus} on the aquatic community in Boulder Creek and formatting data to fit the Divisions proposed methodology to determine expected conditions and identify possible impairments to the aquatic community. Based on fall 2008 macroinvertebrate sampling below the 75t~' Street W WTF Timberline Aquatics identified an improvement in macroinvertebrate populations and an increase in intolerant species, which indicates improved water quality in Boulder Creek. The Division will propose state-wide nutrient criteria to the Water Quality Control Commission at the 2010 Basic Standards Hearing. Nutrient criteria development Work Group meetings will continue through 2009 and into early 2010 in preparation for the Hearing. The city of Boulder is actively participating in the Work Group meetings and will need to decide in late 2009 whether there is a need to testify at the 2010 Basic Standards Hearing. CDPS Permit Renewal C?n January 31, 2008, the 75~' Street WWTF CDPS permit expired and was administratively extended by the Division. As required by the Division, CDPS permit renewal applications are due to the Division 180 days prior to permit expiration. The city completed the CDPS permit renewal application and submitted it to the Division on August 1, 2007. As part of the permit renewal process, Water Quality and Environmental Services and Wastewater Treatment staff worked with the consulting firm Brown and Caldwell to develop Preliminary Effluent Limits and identify any potential concerns early in the permitting process. Beyond lower ammonia limits, and the potential for nitrate effluent limits, the remaining limits should be achievable with the current WWTF activated sludge treatment process. AGENDA ITEM # 9 PAGE 9 Based on discussions with Division staff, the 75th Street WWTF CDPS permit should he renewed in 2009. The Division recognizes that the city is working on multiple water quality studies and there are Hearings scheduled in 2009 and 2010, and both will influence the next V4'WTF CDPS permit. The Division has stated they will incorporate results from completed studies, and for studies still underway, a compliance schedule will be implemented in the permit to allow sufficient time to complete studies and incorporate any changes that may come out of the 2009 South Platte Basin Hearing and 2010 Basic Standards Hearing. REC"ONINIENDATION: Staff recommended that the City remain proactive in attending Division regulatory Work Groups and performing water quality studies to support the CDPS permit renewal and adequately prepare for future regulations. Staff will be selective in determining where resources should be spent and take into consideration required staff time and budget limitations. ATTACHMENTS: Attachment A: Boulder Creek and WWTF Effluent Temperature Data Attachment B: Comparison of City of Boulder 75th Street Wastewater Treatment Ammonia Effluent Limits and Potential New Ammonia and Nitrate Effluent Limits Based on 2005 Nitrogen Modeling AGENDA ITEM # 9 PAGE 10 Attachment A Boulder Creek and W{NTF Effluent Temperature Data 35.0 30.0 . . . . . . . . . . . . . - 25.0 ~ ~ , ~ zo.o ~ 9 ~ ~ti Upstream V ~ i I1~~~ ; , Outfall 15.0 ~1 ~ ~ ~y i Downstream ~ ~ - -Chronic +y i - -Acute 10.0 - - - JJ~II ~ - - i! 5.0 - 0.0 m n n n n n ti n n n n n r- m m m m m m m m m m m m 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 N N N N N N N N N N N N N N N N N N N N N N N N N -5.0 N N M ~ t0 m i~ m m O N N M ~ trf m h- m OY O N AGENDA ITEM # 9 PAGE 11 Attachment B Comparison of City of Boulder 75a` Street ~Vastewatei• Tzeatment Ammonia Effluent Limits and Potential New Ammonia and Nitrate Effluent Limits Based on 200$ Nitrogen 117odelingi Permit and Constituent Month and Effluent Limit, m~/L Jan Feb March April May June July Aug Sep Qct Nov Dec Current CDPS Fermit Ammonia Acute (Daily Maximum} NA NA NA NA NA NA NA NA NA NA NA NA Chronic (30-day 18.5 10.9 5.3 9.7 11.3 23.5 19.5 15.1 15.1 15.1 21.6 24.8 Average} Potential Future CDPS Permit Aim©nia Acute (Daily Maximum) 4.8 2.8 3.3 2.9 8.8 3.8 2.1 1.9 2.2 4.4 8.9 7.8 Chronic (30-day 4.8 2.8* 3.1 2.7 3.3 3.3 2.1 * 1.9~ 2.2~ 4.0 4.8 5.2 Average} Nitrate Acute {Daily Maximum} 23.1 24.8 25.0 25.0 25.0 25.0 25.0 25.0 25.0 25.0 24.4 25.0 NA: Not applicable. Current monitoring only requirement. Acute limit is less than chronic limit so chronic limit is set equal to the acute limit. 1 The potential ammonia limits and nitrogen modeling report by Dr. Bill Lewis dated Apri128, 2008 have been submitted and reviewed by the Colorado Water Quality Control Division and are pending final approval. AGENDA ITEM # 9 PAGE 12