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TCL > July 2013 Issue > Control of Nutrients in Colorado Surface Waters: Current Status

July 2013       Vol. 42, No. 7       Page  107
Natural Resource and Environmental Law

Control of Nutrients in Colorado Surface Waters: Current Status
by Gabe Racz, Amy L. Woodis

Natural Resource and Environmental Law articles are sponsored by the CBA Environmental Law, Water Law, and Natural Resources and Energy Law Sections. The Sections publish articles of interest on local and international topics.

Coordinating Editors

Melanie Granberg (Environmental), Denver, Gablehouse Calkins & Granberg, LLC—(303) 572-0050,; Kevin Kinnear (Water), Boulder, Porzak Browning & Bushong LLP—(303) 443-6800,; Joel Benson (Natural Resources and Energy), Denver, Davis Graham & Stubbs LLP—(303) 892-7470,

About the Authors


Gabe Racz is a partner at Vranesh and Raisch LLP. He represents local government, industry, and individuals in water quality, water rights, environmental, and eminent domain matters. He is a member of the CBA and the Environmental Law, Water Law, and Real Estate Law Sections, and has been active in the Colorado Water Quality Forum. He has appeared frequently before the Colorado Water Quality Control Commission and in the water courts and district courts. Amy L. Woodis is the Senior Governmental Policy Analyst at the Metro Wastewater Reclamation District in Denver, where she is responsible for water quality standards development activities, including appearances before the Water Quality Control Commission. She is an adjunct faculty member at Regis University’s College of Professional Studies in the Public Administration Program. She is the current Chair of the South Platte Coalition for Urban River Evaluation (SP CURE) and is a member of the CBA Environmental Law Section.

Nutrients (phosphorus and nitrogen) are a leading cause of degraded water quality in surface waters nationwide. There are numerous anthropogenic sources of nutrients, and without controls, over-enrichment can have detrimental impacts on drinking water supplies, sport fisheries, and recreational opportunities. This article summarizes the current status of the nutrient regulatory framework in Colorado and the nutrient reduction strategy adopted by the Water Quality Control Commission in 2012.

Nutrients, as the term implies, are essential to the health of aquatic ecosystems. Nutrients include phosphorus and nitrogen-based compounds, and when present in optimal concentrations, support aquatic organisms such as fish and macroinvertebrates,1 which results in a balanced habitat.

Throughout the United States, excessive nutrients are found in many surface waters, a condition that is called "cultural eutrophication." According to the U.S. Environmental Protection Agency (EPA), nutrient over-enrichment is a leading cause of degraded water quality nationwide.2

When excess nutrients are present in waters, algae and other plant growth is over-stimulated, which can deplete dissolved oxygen, reduce water transparency, and affect the composition of the biological community. Well-publicized examples of cultural eutrophication include the Gulf of Mexico hypoxic (dead) zone and the Chesapeake Bay.3

According to EPA, agricultural activities are the most widespread source of excess nitrogen and phosphorus leading to nutrient over-enrichment in surface waters.4 Other common nutrient sources include municipal wastewater treatment plants; urban storm water runoff; construction activities; and diffuse pollution sources, such as roads, forest runoff, and atmospheric deposition.

Legal and Regulatory Framework for
Controlling Nutrients in Surface Waters

The purpose of the federal Clean Water Act (CWA) is to "restore and maintain the chemical, physical, and biological integrity of the Nation’s waters."5 In Colorado, the Water Quality Control Act (WQCA)6 and implementing regulations adopted by the Water Quality Control Commission (Commission) provide a comprehensive framework to address water pollution through water quality standards, an antidegradation policy, a system for classifying uses of state surface waters, and a process for periodic review.7

Enforceable water quality standards for individual water bodies are adopted by the Commission in basinwide rulemaking hearings that take place on a rotating basis.8 Also, the WQCA allows for the adoption of control regulations, which have been used historically as watershed protection tools to limit the amount of phosphorus discharged to Colorado reservoirs, including Dillon, Chatfield, Bear Creek, and Cherry Creek.9

Water Quality Criteria and Standards

Under the federal CWA, water quality criteria to set allowable pollution levels in surface waters are based solely on risk-based scientific data and information.10 Costs for municipal and industrial facilities to achieve attainment with water quality criteria through installation of water pollution treatment controls are not considered.11

Generally speaking, water quality criteria are developed by EPA and are not enforceable. Instead, so-called "304(a) criteria" are recommendations for states to use in their own water quality standards-setting processes.12 However, if a state does not adopt water quality standards necessary to protect the designated uses of water bodies, the CWA gives EPA the power to take actions, such as objecting to state-issued discharge permits, developing Total Maximum Daily Loads (TMDLs), or developing water quality standards for the state.13

In Colorado, enforceable water quality standards set specific allowable levels of pollutants in individual water bodies to protect classified uses adopted by the Commission. Uses include protection of aquatic life, recreation, public water supply, and agriculture. Water quality standards can be numeric (for example, the maximum pollutant concentration levels allowed in a water body) or narrative. Narrative standards are commonly called "free from" standards, because they usually describe water body quality as being free from identified negative conditions.14

The primary regulatory tool to reduce the amount of pollutants entering surface waters is a permitting system that allows facilities to release treated wastewater effluent into the environment. Since the CWA was passed in 1972, thousands of discharge permits have been issued nationwide. This control strategy has restricted the amounts of pollutants discharged by municipal and industrial facilities, greatly improving overall water quality and relegating to distant memory times when U.S. waterways were literally on fire.15

National Pollutant Discharge Elimination Permit Program

The CWA and associated federal regulations established the National Pollutant Discharge Elimination System (NPDES) permit program that governs discharges to surface waters.16 Colorado is authorized by EPA to administer the NPDES program, and this function is carried out by the Water Quality Control Division (Division) of the Colorado Department of Public Health and Environment.

NPDES permits for municipal wastewater treatment facilities contain both technology-based17 and water quality-based effluent limitations, which are required when technology-based limitations are not sufficient to meet applicable water quality standards.18 Generally speaking, municipal wastewater treatment facilities use conventional secondary treatment-based systems, such as activated sludge or trickling filters to degrade the biological content of wastewater that is derived from human waste, food waste, soaps, and detergents.19

The need to construct additional treatment processes to remove nutrients has not been universally accepted. Some operators of facilities regulated under the NPDES program have argued that there is a lack of concrete scientific evidence linking nutrient reductions through NPDES permits to actual receiving water quality improvements.20

Federal Nutrient Control Perspective:
A Call to Action

In 1998, EPA outlined a strategy describing how it would develop numeric nutrient water quality criteria and expectations on how states should use that framework to develop enforceable water quality standards for nutrient-related parameters.21 The strategy proposed a two-phase process: (1) EPA would develop numeric "nutrient criteria guidance" values for nitrogen and phosphorous (causal parameters), as well as for chlorophyll a, secchi depth,22 and algal biomass (response variables); and (2) states subsequently would adopt enforceable nutrient standards based on these values.23

EPA proposed developing nutrient 304(a) criteria using a geographic (ecoregional) approach rather than on a national basis, to address differences in climate, elevation, and land uses. The suggested target date for states to adopt enforceable nutrient standards was set at the end of December 2003.24

In January 2001, EPA published a Notice of Ecoregional Nutrient Criteria for Lakes and Reservoirs, Rivers and Streams, and Wetlands (Notice).25 In part, the Notice indicated that the nutrient criteria "are intended to represent water quality conditions that are reflective of those minimally impacted by human activities" (emphasis added).26

Later that year, EPA sent a memorandum to the EPA Regions and states to provide additional guidance on development of nutrient criteria plans, the role of these plans in the adoption of numeric nutrient standards, and EPA’s expectations regarding associated timeframes.27 In the memo, EPA reminded states that if they did not meet expected timetables, the agency could decide to take actions on its own where activities to adopt nutrient standards fell short.28

Despite EPA’s urging through guidance, states were slow to adopt numeric nutrient standards due to the cost of potential upgrades to wastewater treatment facilities and scientific uncertainty between nutrient causal and response variables.29 Instead, most states continued to rely on existing narrative nutrient standards, taking action to reduce nutrient loading from regulated point sources only where water quality impairments were demonstrated.30

In response, in 2007, EPA issued an updated memo, asking its "partners to take bold steps, relying on a combination of science, innovation, and collaboration" to establish numeric water quality standards for nitrogen and phosphorus.31 Subsequently, EPA continued to assess states’ progress toward development of numeric nutrient standards. A Nutrient Innovations Task Group was formed in 2008 to evaluate existing regulatory tools and innovative approaches to address nutrient pollution. The Task Force Report was issued in 2009.32

In March 2011, EPA published a memorandum that "reaffirmed" its commitment to "partnering" with states to reduce nutrient pollution simultaneously with the development of numeric water quality standards.33 Overall, the 2011 memorandum was well received by the regulated community because it appeared to offer flexibility to reduce nutrient pollution over time. However, it is unclear whether EPA will adhere to the spirit of the memorandum or if a more rigid regulatory approach through imposition of stringent effluent limitations at regulated facilities will be the rule rather than the exception.34

Colorado’s Nutrient Regulatory
Development Process

Beginning in 2001, the Division and interested stakeholders embarked on a long-running workgroup process that resulted in a Nutrient Criteria Development Plan for Colorado (Plan).35 The Plan was submitted to EPA Region 8 in 2002 and included separate approaches for rivers/streams and lakes/reservoirs. Because of the state’s experience with reservoirs (for example, those subject to existing control regulations), it was anticipated that assessment of high-priority reservoirs would be a first nutrient evaluation step.36

The Division’s approach to rivers and streams was somewhat less confident. As the 2002 Plan noted, "other [Region 8] states are struggling with many of the same problems and there is no clear consensus on how plans should be developed for rivers and streams."37

The Plan, updated in 2007, stated that for rivers and streams, the Division would investigate the linkage between aquatic life use support and nutrient levels using macroinvertebrate-based data. The Plan indicated that a formal nutrient proposal would be finalized in January 2010, with a rulemaking hearing scheduled for June 2010.38

In February 2010, the Division presented initial rivers and streams nutrient values to stakeholders. The values were less stringent than EPA’s ecoregional criteria but very difficult to achieve at "end of pipe" from a treatment perspective.39 Revised criteria were completed in October 2010, and the revised values generally were relaxed slightly from those proposed by the Division in February. EPA expressed concern that the revised values might not be adequately protective.40

Stakeholder Responses to
the Division’s Nutrient Proposal

During 2010, the regulated community’s concerns regarding the Division’s proposal began to coalesce. Most of those concerns focused on scientific uncertainty underlying the Division’s proposed nutrient values, disagreement over whether nitrogen control was needed at all, and potential compliance costs.

In response, various stakeholder groups began to seek relief through suggested changes to the Division’s proposal, as well as through legislative action. To encourage settlement of disagreements among the various parties, the Commission postponed the nutrient rulemaking hearing date from June 2010 to June 2011.

Revisions to the Division’s Nutrient Proposal

Near the end of 2010, it became apparent that adoption of the Division’s proposed values for phosphorous and nitrogen would be opposed by a large proportion of the regulated community statewide.41 On the other hand, the conservation community42 expressed concern that without rapid approval of enforceable water quality standards and implementation through discharge permit effluent limitations, many surface waters would not achieve protective levels of nutrients for decades.

In an effort to reduce the potential "sticker shock" of having to implement very stringent phosphorus and nitrogen discharge permit effluent limitations to achieve in-stream enforceable nutrient standards, in late 2010 a small group of interested stakeholders developed a separate nutrient reduction strategy based on a new statewide technology-based control regulation.43 This approach would require phosphorus reductions from municipal facilities through mandated discharge permit effluent limitations at levels achievable through conventional biological nutrient removal (BNR) treatment. In contrast, treatment to achieve the Division’s proposed nutrient values in-stream would often require installation of "limit of technology" treatment processes, such as reverse osmosis.44 Subsequently, this control regulation concept was modified and incorporated by the Division into its own proposal.

Postponement of Nutrient Hearing
for Completion of a Cost-Benefit Study

In January 2011, based on stakeholders’ continued concerns over nutrient removal costs, the Commission decided to delay the rulemaking hearing again, this time from June 2011 until March 2012, to accommodate completion of a study of the costs and benefits associated with phosphorus and nitrogen removal at wastewater treatment facilities statewide.45 This study was financed through the Water Resources and Power Development Authority and evaluated three tiers of nutrient removal technologies as well as associated costs and benefits, as shown in the accompanying chart entitled "Nutrient Removal Technologies: Costs and Benefits."46

No matter what level of treatment, the study concluded that costs to reduce phosphorus and nitrogen would be significant. In fact, the majority of these costs would be borne by local municipalities and special districts that provide wastewater service.

Stakeholder Political Initiatives, 2011–12

Colorado has a statutory prohibition against any state regulatory agency enacting any "new state mandate . . . unless the state provides additional moneys . . . to reimburse . . . local government for the costs of such new mandate," unless the mandate is the result of "any requirement of federal law."47 A "federal law" is limited to:

federal action which has the force and effect of law and which either requires the state to take action or . . . will . . . result in the loss of federal funds if state action is not taken (emphasis added).48

Regulated entities dissatisfied with the Division’s nutrient reduction proposal attempted to slow down, stop, or overturn the rulemaking hearing process during 2011 and 2012. These efforts began with House Joint Resolution 11-1025,49 which passed in 2011. The most significant aspect of the Resolution was a request that the Division provide evidence that its proposal complied with Executive Order D 2011-005.50

Similar to the unfunded mandate statute, the Governor’s Executive Order 005 prohibits any state agency, "to the extent authorized by law," from promulgating any regulation that creates a mandate on local government unless: (1) the mandate is specifically required by federal or state law; (2) the agency consults with local governments; and (3) "the state government provides the funding necessary to pay for the direct costs incurred by local governments in complying with the mandate."51

Because the control regulation included technology-based effluent limitations beyond those required by EPA, some concerned municipalities asserted that it was a mandate not the result of "any requirement of federal law." Also, because the state did not identify funds to reimburse local governments for the costs of implementation, the control regulation itself could be legally viewed as optional for municipalities.52

In the 2012 session, two nutrient-related bills were considered by the legislature. Neither made it to the Governor’s desk.53

March 2012 Nutrient Rulemaking Hearing

Due to the high level of controversy remaining over the Division’s proposal, the hearing was scheduled for three days to accommodate the testimony of more than eighty parties. The hearing represented one of the most contentious in over a decade.

The Commission described its action as a "coordinated strategy" to address current and future nutrient pollution.54 This strategy included two major components. First, the Commission adopted Regulation 85, the "Nutrients Management Control Regulation," the final refinement of the Division’s control regulation strategy. Second, the Commission adopted changes to its "Basic Standards," Regulation 31, to include the Division’s final proposed interim numerical values for total phosphorus, total nitrogen, and chlorophyll a.

Regulation 85: Colorado’s Nutrients
Management Control Regulation

One of the most significant features of Regulation 85 was the inclusion of technology-based effluent limitations to control phosphorus and nitrogen. The Commission’s stated goal in setting these effluent limitations was to balance limits that would result in significant nutrient reductions against considerations including cost and feasibility.55

Effluent limitations. Regulation 85 has different sets of technology-based effluent limitations for existing facilities and new facilities. For existing facilities, the effluent limits are shown in the accompanying chart entitled "Effluent Limitations."56

Who is subject to Regulation 85 effluent limitations and timing. Based partially on information in the Cost-Benefit Study, the Commission limited the immediate applicability of Regulation 85 effluent limitations to the largest domestic wastewater treatment works and select non-domestic facilities that are expected to contribute high concentrations of nutrients, such as dischargers in the food industry.57 It appears that only forty-four facilities will be included, located primarily along the Front Range, although some facilities in Southwestern Colorado and the Colorado River basin also are included.58

The effluent limitations do not apply to smaller domestic facilities (with design flow less than 1 million gallons per day (MGD)) or those owned by disadvantaged communities.59 Implementation of the effluent limitations is delayed until 2022 for facilities that already are subject to nutrient control regulations.60 Implementation also is delayed for domestic facilities smaller than 2 MGD and any existing facility in specified "low priority" watersheds.61

Regulation 85 monitoring and reporting. Regulation 85 requirements to monitor and report data related to nutrients are the most widely applicable parts for regulated facilities. Because the monitoring requirements do not follow the usual practice of requiring monitoring only for constituents listed in the discharge permit, they could catch some dischargers unawares.62

The Regulation 85 monitoring and reporting requirements vary by type of discharger. All domestic dischargers, and all non-domestic dischargers that may have high nutrient concentrations in their effluent, must analyze their effluent samples for total nitrogen and total phosphorus (or the separate components to calculate the total forms of these substances).63 Dischargers that will be subject to Regulation 85 effluent limitations also must sample for total nitrogen, total phosphorus, and stream flow in the receiving water body upstream and downstream of the discharge.64 Dischargers and others may meet the in-stream monitoring requirements through collaborative watershed-based monitoring efforts.65

All Municipal Separate Storm Sewer Systems (MS4s) covered by the state’s general permit for MS4s before March 1, 2012 must submit to the Division an assessment report by October 31, 2014.66 The purpose of the report is to identify existing information and additional monitoring that must be done to determine the approximate contribution of phosphorus and nitrogen from MS4 stormwater discharges.67 In addition, cooling water discharges are required to monitor flow, total phosphorus, total nitrogen, and total inorganic nitrogen.68

Regulation 31 Interim Numeric Nutrient Values

The Commission did not adopt numeric water quality standards for phosphorus or nitrogen in the 2012 hearing. Instead, it adopted interim values for total phosphorus, total nitrogen, and chlorophyll a.69

The adopted rivers and streams interim values to protect aquatic life were: cold water phosphorus – 0.110 mg/L; warm water phosphorus – 0.170 mg/L; cold water nitrogen – 1.25 mg/L; and warm water nitrogen – 2.01 mg/L. The interim values for chlorophyll a include a measure of attached algae in streams and a value for "direct use water supply" lakes to prevent the formation of disinfection by-products resulting from drinking water treatment processes.70

The Commission established these values at levels "that the currently available scientific information indicates would be protective of the corresponding categories of beneficial uses."71 As discussed above, the Cost-Benefit Study estimated that it would cost $23 billion statewide to implement nutrient reductions to achieve the interim values.

Adoption of the interim values as water quality standards will occur in stages over the next ten to fifteen years. First, from 2012 to 2017, the Commission will consider whether to adopt the interim total phosphorus values as water quality standards for segments in headwaters located upstream of permitted dischargers subject to Regulation 85.72 In addition, starting in 2012, the Commission will consider on a site-specific basis whether to adopt a numeric chlorophyll a standard for any lake designated as a direct use water supply.73

Second, from 2017 to 2022, the Commission will consider whether to adopt the interim total nitrogen values as water quality standards for headwaters segments.74 Finally, after May 31, 2022, the Commission will consider adopting any of the interim values as segment-specific water quality standards for any water body where necessary to protect the assigned use classifications and comply with the WQCA and CWA.75

Although this phased approach is the default schedule for adoption of numeric water quality standards for nutrients, the Commission also retained the authority to adopt enforceable nutrient standards in any circumstance where it is "necessary to address existing or potential nutrient pollution because the provisions of Regulation #85 will not result in adequate control of such pollution."76

Future Nutrient Challenges

Although the March 2012 rulemaking established a path forward for Colorado nutrient reductions, there remains considerable uncertainty regarding: (1) the associated costs of treatment technologies; (2) the timing of adoption of the interim numeric values as enforceable water quality standards; (3) whether point source controls will actually result in improved water quality; and (4) the need for future controls over activities traditionally exempt from the CWA, such as agriculture and water management.

It also is unclear whether EPA will accept this unique approach. If not, the agency can object to NPDES permits for causing or contributing to exceedances of the narrative water quality standard, or it can add water bodies to the 2012 303(d) List as impaired for nutrients, thus triggering the need to develop a TMDL.77

Narrative Standards Issues

In light of the adoption of Regulation 85 and the interim nutrient values in Regulation 31, there remains uncertainty how these provisions affect interpretation and implementation of Colorado’s narrative water quality standards for nutrients. EPA regulations that implement the CWA require states to ensure that discharge permits include effluent limitations to prevent exceedances of narrative water quality standards.78

Where a state has not established numeric water quality standards, effluent limitations may be based on numeric standards proposed by the state, or on criteria established by EPA.79 EPA has expressed concern that states are not complying with the requirement to implement the narrative standards in permits or are not listing water bodies for impairments based on the states’ nutrient narrative water quality standards.80

The Commission stated that it "does not intend that the interim numerical values adopted in section 31.17 would be used as the basis for implementing Colorado’s narrative water quality standards."81 Instead, the Commission stated, "compliance with Regulation #85 will be deemed to be compliance with the narrative standards unless and until the Commission adopts subsequent revisions to Regulation 85 and/or Regulation 31."82

Thus, it appears that the Commission intended a step-wise approach to nutrient reductions—at least for facilities with Regulation 85-mandated discharge permit effluent limitations. However, this does present a conundrum for the numerous other facilities statewide that are not subject to Regulation 85 effluent limitations. In fact, the risks are particularly acute for small and disadvantaged communities. Out of concern for these communities’ ability to pay, the Commission exempted the vast majority of these communities’ discharges from Regulation 85 effluent limitations and delayed implementation of the effluent limitations for the rest.83

Ironically, these communities that are exempted might not gain the protection offered by the Commission’s statement that "compliance with Regulation #85 will be deemed to be compliance with the narrative standards." Without the permit "shield" of mandated effluent limitations, an argument could be made by EPA or third parties that those facilities’ discharges are causing or contributing to exceedances of the narrative nutrient standards.

Impaired Waters Listings

The Commission stated that it did not intend that the interim numerical nutrient values "will be used directly as a basis for identifying impaired waters to include on Colorado’s Section 303(d) List."84 This left open the question of how the interim values could be used indirectly. The Commission did not specify a method for making listing decisions, but requested that the Division address the issue in the Section 303(d) Listing Methodology, a policy document that the Commission planned to modify for listing decisions in 2014.

If the state were to make narrative-standard listing decisions based on a comparison of phosphorus or nitrogen data against the interim values, even "indirectly," there could be serious ramifications for dischargers. For existing discharges, federal and state regulations require effluent limitations to be calculated to achieve water quality standards, including narrative standards.85 In situations where a water body is on a state’s 303(d) List because of nutrients, stringent effluent limitations may be calculated to attain the narrative standard, even if a TMDL has not yet been completed.86

For new discharges, federal regulations prohibit discharges that "will cause or contribute to the violation of water quality standards," including narrative standards.87 Federal courts have interpreted this regulation strictly to prohibit discharges to impaired segments until restrictive conditions are met that would require completion of a TMDL.88 One way to avoid this prohibition is for the permitting agency to set effluent limitations for new discharges to 303(d) listed segments equal to the numeric water quality standards. However, effluent limitations set using the interim values would be squarely inconsistent with the Commission’s intent in adopting the nutrient interim values, expressed in the Regulation 31 and 85 Statements of Basis and Purpose.

Although discussions involving the Division and stakeholders regarding the 2014 303(d) Listing Methodology began in 2012, consensus regarding the Commission’s intent regarding the effect of Regulation 85 on attainment of narrative nutrient standards could not be reached. In fact, this issue will remain unresolved for the 2014 303(d) listing cycle. Because of resource constraints and demands from other program areas administered by the Division, the state will not prepare a 2014 list.89

Options for More Reasonable Effluent Limitations

Dischargers have options available to mitigate the risk of future unachievable or infeasible water quality-based effluent limitations for nutrients. However, substantial data collection, study, and modeling will be required if dischargers hope to successfully navigate these challenges.

Colorado has a history of adopting site-specific water quality standards. For example, if a water body has nutrient concentrations higher than the interim values, a discharger may propose standards based on the existing quality. Such "ambient quality-based standards" require evidence that the existing quality is caused by natural or "irreversible human-induced" conditions, and that the existing quality is "adequate to protect classified uses."90

Similarly, a discharger may be able to provide technical support for achievable effluent limitations based on site-specific conditions. Modeling based on the fate and transport of nutrients may result in relaxed effluent limitations, particularly for nitrogen, which naturally attenuates in water bodies.91

Recently, the Commission adopted provisions that allow for "discharger-specific variances."92 Variances are temporary water quality actions by the Commission that authorize a discharge to exceed water quality-based effluent limitations based on a finding that meeting the standards would be infeasible. Variances will require a comprehensive alternatives analysis to demonstrate that meeting the standard would be technologically or economically infeasible or would cause more environmental harm than allowing the discharge to occur.93 Discharger-specific variance guidance is still being developed.94

The common theme of all of these options is the need to obtain and evaluate comprehensive and scientifically defensible water quality data. In some parts of the state, existing data collection coordination efforts are in place to make the process more efficient.95

Concerns for Water Management
and Water Transfer Activities

Challenges to water management and water transfer activities may be possible in the future. Common water management practices, particularly with respect to reservoirs, can affect loading of nutrients to water bodies and influence aquatic life and other classified uses.96 Also, transfers of water from one water body to another necessarily move the nutrients along with the water.97

The Commission has the authority to control nonpoint pollution sources through control regulations.98 This authority includes limited authority to regulate agricultural nonpoint sources if the Commission finds that incentive, grant, and cooperative programs are inadequate and regulation of agricultural nonpoint sources is necessary to meet state law or the CWA.99

In Regulation 85, the Commission stated it will consider nonpoint source prohibitions or precautionary measures if voluntary load reductions from nonpoint sources are not effective in managing nutrients by May 1, 2022.100 However, the Commission is prohibited from adopting regulations that cause material injury to water rights.101


Colorado has taken significant steps to protect its surface waters from the effects of cultural eutrophication. The two-part strategy—implementation of a control regulation to address nutrient loadings from the largest regulated point sources, coupled with future adoption of enforceable water quality standards for nitrogen, phosphorus, and chlorophyll a—puts Colorado at the forefront of states taking tangible steps to improve overall water quality.

On the other hand, the financial burden for complete implementation may be considerable, costing in excess of $23 billion. Identification of more cost-effective solutions, based on evaluation of surface water quality data and impacts on classified uses, should be explored by affected municipalities and special districts. Moreover, nutrient contributions from activities not currently regulated under the CWA, such as those associated with agriculture and water management, are likely to be characterized to help ensure that all nutrient sources are accounted for and reduced as determined by regulations adopted by the Commission.


1. Examples of aquatic macroinvertebrates include larval forms of insects, clams, snails, and worms.

2. See EPA-820-S-12-002 (Dec. 2012).

3. An overview of hypoxia can be found at

4. See EPA-840-R-98-001 (Feb. 1998).

5. 33 USC § 1251(a).

6. CRS §§ 25-8-101 et seq.

7. Colorado water quality regulations are available at www.colorado.

8. CRS § 25-8-204.

9. CRS § 25-8-205.

10. 33 USC § 1313(c).

11. In contrast, CRS § 25-8-102(5) indicates, in part, that Colorado’s water quality program consider economic, environmental, public health, and energy impacts.

12. 33 USC § 1314(a).

13. 33 USC §§ 1313(c) and (d) and 1342(d).

14. Regulation No. 31 (5 CCR 1002-31) § 31.11(1).

15. The 1969 Cuyahoga River fire in Cleveland, although brief, has been acknowledged as a turning point in the national movement toward environmental protection.

16. See 33 USC § 1342; 40 CFR §§ 122 and 123.

17. 33 USC § 1311(b).

18. 33 USC § 1312.

19. 33 USC § 1314(d); 40 CFR Part 133.

20. See, e.g., EPA Environmental Appeals Board, In the Matter of Town of Newmarket Wastewater Treatment Plant (filed Dec. 14, 2012).

21. See EPA-822-R-98-002 (June 1998).

22. Secchi depth measures water clarity.

23. EPA-822-R-98-002, supra note 21 at 5.

24. Id. at 6.

25. See 66 Fed. Reg. 1671 (Jan. 9, 2001).

26. Id. The applicable EPA 304(a) ecoregional criteria were: cold water total phosphorus = 0.006 mg/L; cold water total nitrogen = 0.09 mg/L; warm water total phosphorus = 0.025 to 0.09 mg/L; and warm water total nitrogen = 0.45 to 0.84 mg/L.

27. See Grubbs, "Memorandum: Development and Adoption of Nutrient Criteria into Water Quality Standards" (Nov. 14, 2001), available at

28. Id. at 3.

29. See, e.g., EPA Science Advisory Board, Review of Empirical Approaches for Nutrient Criteria Derivation, EPA-SAB-10-006 (April 27, 2010).

30. Examples include excessive algal growth and/or fish kills. See, e.g., Letter from EPA Office of Water to Florida Department of Environmental Protection (Jan. 14, 2009), available at

31. "Nutrient Pollution and Numeric Water Quality Standards—May 2007 Update Memo," available at

32. See State-EPA Nutrient Innovations Task Group, "An Urgent Call to Action: Report of the State-EPA Nutrient Innovations Task Group" (Aug. 2009), available at

33. Stoner, "Memorandum: Working in Partnership with States to Address Phosphorus and Nitrogen Pollution through Use of a Framework for State Nutrient Reductions" (March 16, 2011), available at

34. For example, EPA potentially could challenge discharge permits on the basis that facilities’ discharges are causing or contributing to violations of the narrative standard for nutrients.

35. The Nutrient Criteria Development Plan for Colorado (Plan) is available online at

36. The high-priority lakes and reservoirs included Barr Lake, Fruitgrowers Reservoir, Prewitt Reservoir, Grand Lake, and Island Lake.

37. Plan, supra note 35 at 1.

38. "2007 Progress Report and Update to the Colorado Nutrient Criteria Development Plan" at 1 (Oct. 2007).

39. The Division’s proposed (Feb. 9, 2010) rivers and streams values for aquatic life use protection were as follows: cold water total phosphorus = 0.090 mg/L; cold water total nitrogen = 0.824 mg/L; warm water total phosphorus = 0.135 mg/L; and warm water total nitrogen = 1.316 mg/L.

40. The Division’s October 13, 2010 rivers and streams values to protect aquatic life were as follows: cold water total phosphorus = 0.11 mg/L; cold water total nitrogen = 0.40 mg/L; warm water total phosphorus = 0.16 mg/L; and warm water total nitrogen = 2.0 mg/L.

41. A consortium of regulated wastewater treatment, stormwater entities, and others formed the Colorado Nutrient Coalition, the primary purposes of which were to ask for a scientific peer review of the Division’s proposal and to educate members of the Colorado legislature on nutrient-related issues.

42. The conservation community included the Colorado Environmental Coalition, Colorado Trout Unlimited, High Country Citizens’ Alliance, and San Juan Citizens Alliance.

43. Biggs and Woodis, "Memorandum: Draft Total Phosphorous Implementation Concept (For Discussion Only)" (Oct. 7, 2010), available at

44. In addition to great expense, reverse osmosis consumes approximately 15% of the wastewater treated and produces considerable hazardous waste.

45. Regulation No. 85 (5 CCR 1002-85) § 85.15.I.

46. See Cost-Benefit Study of the Impacts of Potential Nutrient Controls for Colorado Point Source Discharges (Sept. 20, 2011), available at

47. CRS § 29-1-304.5.

48. Id.

49. HJR 11-1025, by Rep. Looper from the 19th House District.

50. Executive Order D 2011-005, available at

51. Id.

52. CRS § 29-1-304.5(1).

53. HB 12-1161; SB 12-017.

54. Regulation No. 31 (5 CCR 1002-31) § 31.50.I.

55. Regulation No. 85 (5 CCR 1002-85) § 85.15.III.

56. Id. at § 85.5(1)(a)(iii).

57. Id. at § 85.15.I.

58. Facilities subject to Regulation 85 effluent limitations on their next permit renewal include the following: Pueblo; Security Sanitation District; Widefield; Tri-Lakes; Colorado Springs (two facilities); Glenwood Hot Springs; Glenwood Springs; Eagle River (Vail, Avon, and Edwards); Aspen; Snowmass; Fruita; Mesa County/Grand Junction; Centennial; Littleton/Englewood; MillerCoors; Superior; Lafayette; St. Vrain; Louisville; Longmont; Boulder; Loveland; Carestream; Boxelder; Windsor; Swift; S. Fort Collins; Fort Collins (Drake and Mulberry); Greeley; Metro Wastewater; Aurora; Northglenn; Westminster; Broomfield; Swift Beef; Fort Lupton; Brighton; South Adams; Durango; and Pagosa.

59. Regulation No. 85 (5 CCR 1002-85) § 85.5(1)(a)(i).

60. Id. at § 85.5(1)(a)(ii).

61. Id.

62. Id. at § 85.6.

63. Id at § 85.6(2)(a) and (b)(i).

64. Id. at § 85.6(2)(b)(ii).

65. Id.

66. Id. at § 85.6(3)(c).

67. Id. at § 85.6(3)(b).

68. Id. at § 85.6(2)(a).

69. Regulation No. 31 (5 CCR 1002-31) § 31.17.

70. Id. at § 31.50.II.

71. Id. at § 31.50.I.

72. Id. at § 31.17(e)(i).

73. Id. at § 31.17(e)(ii).

74. Id. at § 31.17(f).

75. Id. at § 31.17(g).

76. Id. at § 31.17(e)(iii).

77. Under § 303(d) of the CWA, states must develop lists of "impaired waters" every two years. In Colorado, these are included in Regulation 93, 5 CCR 1002-93.

78. 40 CFR § 122.44(d).

79. 40 CFR § 122.44(d)(vi).

80. See, e.g., Letter from EPA Region 5 to the Illinois EPA (Jan. 21, 2011), available at

81. Regulation No. 31 (5 CCR 1002-31) § 31.50.VII.

82. Id.

83. Regulation No. 85 (5 CCR 1002-85) § 85(1)(a).

84. Regulation No. 31 (5 CCR 1002-31) § 31.50.VI (emphasis added).

85. 40 CFR §§ 122.4(d) and 122.44(d); Reg. 31.14(4).

86. Upper Blackstone Water Pollution Abatement Dist. v. U.S. EPA, 690 F.3d 9 (1st Cir., Aug. 3, 2012), reh’g denied Sept. 25, 2012, cert. denied May 13, 2013.

87. 40 CFR § 122.4(i).

88. See Friends of Pinto Creek v. U.S. EPA, 504 F.3d 1007 (9th Cir. 2007).

89. Summary of Proceedings, Water Quality Control Commission meeting of December 10, 2012, available at

90. Regulation No. 31 (5 CCR 1002-31) § 31.7(1)(b)(ii).

91. See, e.g., Alexander et al., "Effect of Stream Channel Size on the Delivery of Nitrogen to the Gulf of Mexico," 403 Nature 758 (Feb. 17, 2000).

92. Regulation No. 31 (5 CCR 1002-31) § 31.7(4).

93. Id. at § 31.7(4)(a).

94. A hearing is scheduled for October 2013 to consider the guidance.

95. For example, cooperative urban South Platte monitoring efforts are described at

96. For example, a Total Maximum Daily Load to address nutrient-related pH exceedances in Barr Lake has been developed and is available at

97. See South Florida Water Mgmt. Dist. v. Miccosukee Tribe of Indians, 541 U.S. 95 (2004).

98. CRS § 25-8-205(1)(c).

99. CRS § 25-8-205(5).

100. Regulation No. 85 (5 CCR 1002-85) § 85.5(5)(c)(iii).

101. CRS §§ 25-8-104(1) and -205(5).

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