In and of themselves nutrients aren’t pollutants; in fact, nitrogen and phosphorus are essential for healthy aquatic ecosystems. Many people associate wastewater treatment plants as the main source, but agriculture and urban runoff are as well. Each contributes to unhealthy nutrient levels in different ways. Although expedient, applying identical regulatory standards to all three isn’t necessarily the most effective way to improve overall water quality.

Wastewater treatment plants have traditionally had “end of pipe” limits for the constituents they discharge — copper and other metals, for example — and have developed technologies to treat for the constituents aided by fairly constant and predictable inflow concentrations and rates. Municipal separate storm sewer systems (MS4s), on the other hand, operate under much different circumstances. Rain and snowmelt occur at different times, intensities, and locations. Not every storm produces measurable runoff and constituent concentrations can vary widely.

In March 2012, the Colorado Water Quality Control Commission approved the recommendations of the state agency charged with establishing stream quality standards — the Water Quality Control Division — by establishing a regulation that took a control-technology approach toward lowering nutrient levels.

The process to develop Colorado’s standards started nearly 10 years ago. Stakeholder groups were formed in 2009 to discuss how best to address the issue. The wastewater community was very active in these groups. As months and meetings wore on, it became clear the state was inclined to treat all dischargers the same: begin by monitoring the discharge, then think about treatment. But although both wastewater effluent and stormwater come out of a pipe, the similarity ends there. When we realized our “product” might be monitored like that of a publicly owned treatment works (POTW), we knew we had to take another approach.

Powerful pooled resources

Luckily, in 2006 most of the state’s stormwater permittees had come together to form the Colorado Stormwater Council (CSC) in 2006. The organization hoped that having a smaller, more-targeted coalition tackle the monitoring issue by explaining the inherent economic differences and implementation impracticalities of treating stormwater like wastewater effluent might positively impact the final rule’s language.

We had good relationships with high-level state managers, so we scheduled separate meetings to emphasize we wanted to be part of the solution process and explain why having every permittee install expensive equipment to gather nutrient data wouldn’t be an effective first step toward achieving nutrient goals. Catching storm events in a monitoring device is very difficult and time-consuming anywhere, but particularly so here. The Front Range, where most of Colorado’s 5 million residents live, averages 15 inches of precipitation annually. Even if sampling events were successful, how would 60-plus different permittees sampling on their own produce meaningful conclusions?

Aurora, Colorado Springs, Denver, and Lakewood have experience with monitoring because it’s been a requirement of Phase I permittees since they were first issued in 1996 and 1997. The cities’ data showed a general improvement in water quality over 15 years, which was encouraging.

However, after spending a year getting a sampling site up and running, Lakewood and Aurora both learned that getting data from five or six storms is a good year. Therefore, permittees would need at least four years — one year after the regulation would have expired — before a meaningful monitoring report would be available.

Adding to the need for another approach was what smaller permittees with limited resources would have to do to prepare a sampling plan, and how all the different sampling plans would come together to produce a meaningful product. The state’s initial nutrient monitoring requirements would cost Lakewood, population 143,000, at least $320,000 annually.

Instead of launching directly into monitoring, we urged regulators to see what could be learned from data that already exist, such as the 15 years’ worth of wet weather monitoring reports as well as data collected by a number of watershed organizations. This well-coordinated and consistent approach, plus the willingness of all parties to listen to and discuss alternatives, produced the nutrient regulation that was finally presented. There was little discussion on the regulation’s stormwater sections and no significant changes were made. The state eliminated monitoring requirements, but each MS4 must:

1. Develop a discharge assessment data report by Oct. 31, 2014. Identify existing information and the need for additional monitoring to be conducted in the future to determine approximate nitrogen and phosphorus contribution to state waters due to discharges.

2. Develop and implement a public education program to reduce water quality impacts associated with nitrogen and phosphorus in stormwater runoff and illicit discharges. Materials or equivalent outreach are to be distributed to targeted sources (e.g., residential, industrial, agricultural, or commercial) that are contributing, or have the potential to contribute, nutrients to state waters.

3. Develop and implement a program to prevent or reduce nitrogen and phosphorus in stormwater runoff associated with municipal operations, if any.

Considering the length of the hearing process (three full days) and the amount of testimony and rebuttal documents generated in the nutrient hearing, having the stormwater issue resolved beforehand shows the power of developing a coalition with a common purpose and pooling resources in a productive manner.

Next steps

Continuing this collaborative approach, the council is working with the regional Urban Drainage and Flood Control District (UDFCD) in Denver to address the state’s desire for a single, statewide data assessment report.

The first challenge is to meet the Oct. 31, 2014, deadline for presenting the data assessment reports, including a data gap analysis. The other is paying for it. We’re collecting data to turn over to a consultant that will prepare the data assessment report. The council and UDFCD are each providing $30,000; additional resource needs will be defined as the consultant selection process is finalized.

Piatt Kemper ( is senior environmental engineer for Aurora Water in Aurora, Colo.; McCarthy ( is water quality manager for the City of Arvada, Colo.; and Searcy ( is stormwater quality coordinator for the City of Lakewood, Colo.