Bell, Clifton

Clifton Bell is Brown and Caldwell's Technical Leader for Water Quality. He is recognized nationally for his expertise in Clean Water Act compliance, crafting solutions to complex water quality challenges and fostering consensus among public and private stakeholders. A former hydrologist with the U.S. Geological Survey, Clifton has led water quality management, NPDES, and TMDL projects across the country, from Florida to California. He is especially noted for his expertise in nutrient science and standards development

Titles from this speaker

Re-Evaluating Established TMDLs: Applying True Adaptive Management to Improve Water Quality in High Value Receiving Waters

Abstract

Background : Total maximum daily loads (TMDLs) are sometimes developed with limited datasets and simplistic modeling approaches. Nevertheless, these TMDLs can have large cost implications for regulated entities such as wastewater utilities and municipal separate storm sewer systems (MS4s). After TMDLs are officially approved, they can be difficult to change, and can result in costly MS4 requirements over multiple permit terms. If the original TMDL was poorly formulated, these investments might not result in true environmental benefits. This paper presents a case study of how two Pacific northwest localities (Pierce and Whatcom Counties, WA) engaged regulatory agencies and other stakeholders to reassess data-limited TMDLs and improve approaches to protecting water quality in high value waters.

* Stream Example— Clarks Creek: Clarks Creek is tributary to the Puyallup River to that drains about 13 mi2 of Pierce County and the City of Puyallup (Figure 1). High spring flows allow the stream to support one the region's healthiest populations of salmon and trout. The County has historically harvested aquatic plants in the stream to improve aesthetics and reduce flooding of adjacent properties (Figure 2). Clarks Creek was 303(d)-listed as impaired for low dissolved oxygen (DO) concentrations in 2012, and the Washington Department of Ecology (Ecology) finalized a TMDL in 2014. The TMDL called for large increases in DO in stormwater and groundwater, treatment of large stormwater volumes, increases in riparian shading, a 67-75% reduction in aquatic plants, and an 80% reduction in sediment oxygen demand (SOD). The original TMDL technical analysis (Ecology, 2014) was constrained by data and modeling limitations. In 2015, the County and Ecology agreed Ecology agreed that the TMDL study would be subject to a 5-year reassessment process. The County collected additional hydrologic and water quality, and performed special studies of aquatic plants and sediment characteristics. The County also developed a new modeling framework that included a hydraulic model (HEC-RAS), a watershed model (HSPF), and a receiving water quality model (QUAL2Kw) (Figure 3). A series of model scenarios were run to explore the response of DO in Clarks Creek to various management options, including riparian shading, stormwater treatment, stormwater diversion, and aquatic plant reduction (BC, 2022; Gawel, 2020). Some important new findings include: (1) Under dry weather conditions, DO in the creek is primarily determined by the DO of spring water (~8 mg/L) that is naturally lower than the water quality criterion (10 mg/L). (2) SOD is much lower than assumed in the original TMDL analysis, which leaves less potential room for DO improvement by SOD reduction. (3) The original TMDL's call for large amounts of traditional stormwater treatment would not likely benefit the creek, because DO in the creek is insensitive to the parameters that are normally removed in stormwater BMPs. (4) Conversely, practices that increase the DO of stormwater inflows (e.g., improved reaeration) could improve DO in the creek. (5) Average DO in the creek is actually higher if some aquatic plants remain in the creek. Based on the new data and models, the County is proposing major updates to the original TMDL analysis, including the development of a site-specific water quality criterion that reflects the high spring flows to the creek. The proposed implementation approach continues to emphasize riparian shading and SOD reduction. However, it put less emphasis on traditional stormwater treatment and aquatic plant removal, and more emphasis improved reaeration in stream channels and the stormwater collection system.

* Reservoir Example—Lake Whatcom: Lake Whatcom is an important ecological, recreational, and aesthetic resource and the main water supply for more than 100,000 people in Whatcom County (County) and the City of Bellingham (City) in Washington State (Figure 4). Motivated primarily by declining concentrations of dissolved oxygen (DO), the Ecology developed a TMDL for total phosphorus (TP) (Pickett and Hood, 2014). The TMDL modeling process was limited by relatively few hydrologic and TP data available at that time, and included only a two-year simulation period (2002-2003). In 2019, the City began a process for updating the models to reassess pollutant loading and lake response for the TMDL. The watershed and lake water quality modeling framework were significantly upgraded for the TMDL reassessment, including many more years of data (2002-2015). After calibration, the updated Lake Whatcom water quality model was applied to simulate the DO response of the lake to pollutant reductions (BC, 2023) (Figure 5). The revised modeling indicated a DO deficit of only about 20 percent of that predicted by the original TMDL modeling. The percent of land subject to expensive stormwater retrofits would decrease from 87% under the original TMDL to about 40%. Significance: These case studies demonstrate that some established TMDLs can be successfully reassessed and modified. A TMDL reassessment project requires significant investment in new data and modeling. Such projects must also be pursued in close cooperation with stakeholders including regulatory agencies, citizens, and environmental groups. However, the outcome can be lower implementation costs, improvement environmental protection, or both.

This paper presents a case study of how a Pacific northwest jurisdiction (Pierce County WA) engaged with its state regulatory agency (Dept. of Ecology) and its tribal partner (Puyallup Tribe) to reassess a data-limited TMDL to help improve the County's strategy for reattaining water quality standards in a high value salmonid bearing stream. The modeling framework was updated based on a full year (Oct 2019- Sep 2020) of intensive data collection.

SpeakerBell, Clifton

Presentation time

14:30:00

14:50:00

Session time

13:30:00

15:00:00

SessionNavigating Nutrient Dynamics: Modeling for Water Quality Excellence

Session number217

Session locationRoom 256

TopicNutrients, Stormwater and Green Infrastructure, Watershed Management, Water Quality, and Groundwater

Author(s)

Bell, Clifton, Milne, Michael, Cervarich, Amory, Hagan, Tim

Author(s)C. Bell1, M. Milne2, A. Cervarich3, T. Hagan4

Author affiliation(s)1Brown and Caldwell, VA, 2Brown and Caldwell, WA, 3Brown and Caldwell, 4Pierce County Surface Water Management

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159483

Volume / Issue

Content sourceWEFTEC

Word count17

Description: Water Quality Sleuthing: Applying Multiple Methods to Identify Pollutant Sources in...

Water Quality Sleuthing: Applying Multiple Methods to Identify Pollutant Sources in Urban Streams

Abstract

Introduction
Urban streams are impacted by a wide range of hydrologic stresses and pollutant sources. Localities that seek to maintain water quality standards in local streams, must identify pollution sources or causes of degradation. Although this can be readily accomplished for many streams, other water bodies, especially in urban settings, present unusual water quality patterns or have pollutants of unknown origin. This paper describes how a combination of traditional and modern methods was applied to understand pollutant sources and improvement opportunities in two urban streams The City of Durham (NC) identified water quality issues on two streams through water quality monitoring. Sandy Creek Tributary A receives stormwater runoff from highly impervious commercial area (Figure 1), and had unusually low dissolved oxygen concentrations, detected during routine ambient monitoring (City of Durham, 2017). Warren Creek drains mixed land uses and had elevated concentrations of metals and polycyclic aromatic hydrocarbons (PAHs) in sediments (AECOM, 2018). The City's existing pollution investigation methods, available data and mapping information did not point to obvious sources/causes of these effects. The City initiated a more detailed investigation in 2020, with goal of identifying both pollutant sources and potential improvement projects. ###Methods
The project team applied multiple methods to identify causes of low dissolved oxygen in Sandy Creek Tributary A. The study began in fall 2020 with evaluation of the stream channel and flow conditions, which documented the extent and nature of urban hydrologic impacts. Additional water quality sampling was performed to detect indicators of potential sources (e.g., wastewater) and characterize spatial variability in water quality within the stream. In fall 2021, the team visually inspected and sampled portions of the stormwater sewer system to identify illicit discharges. This effort included microbial source tracking with the HF183 human marker. A thermal imaging survey was conducted in the stream to identify potential seeps of low-oxygen groundwater to the stream. For Warren Creek, the project team performed additional sampling of metals and PAHs in sediments and water. Sampling locations were designated to provide additional insights into the spatial distribution of these constituents, including whether they demonstrated a hotspot versus distributed pattern. Risk assessments were performed to determine if the observed concentrations were of concern to human or ecological health.
Results
The field investigations revealed several pollutant sources in the upper drainage area of Sandy Creek Tributary A, including a sewer leak, a broken water pipe, and a leaking dumpster (Figure 2). The sewer leak was noteworthy because traditional wastewater indicators (e.g., ammonia, CBOD5) were either low or only slightly elevated in the stream, but the leak was confirmed by both visual inspection and extremely high levels of the HF183 human marker. The effects of these pollutant sources were exacerbated by urban hydrologic impacts on the stream. These included rip rap dams and debris blockages that created stagnant conditions during dry weather periods (Figure 3). Water quality sampling and the thermal imaging survey confirmed that the stream receives inputs of low-oxygen groundwater that help maintain low-dissolved conditions for several thousand feet of stream length (Figure 4). The Warren Creek investigation revealed that metals and PAH concentrations were relatively low at most locations. Although some concentrations exceeded screening levels, the more detailed risk assessments concluded that they were not of concern to human or ecological health. The array of PAHs by molecular weight was similar at all sites, which pointed toward a regional or distributed source rather than hot spots or remediable sources.
Recommended Improvement Projects
Based on the results of the investigation, recommended improvement projects to increase dissolved oxygen levels in Sandy Creek Tributary A included: (1) fixing the identified pollutant sources in the stormwater system, such as the sewer and water line break; (2) in-stream hydrologic improvements to increase stream velocity and aeration; and (3) continued application of MS4 control measures. It was specifically recommended to prioritize the watershed for illicit discharge detection and elimination. Because the Warren Creek contaminants were at relatively low levels and not associated with specific hot spots, the team recommended monitored natural attenuation in combination with MS4 control measures such as good housekeeping, public education, and management of construction site runoff.
Summary and Conclusions
Ambient water quality monitoring networks are useful for characterizing status and trends in local water quality. But more in-depth investigations are needed to accurately characterize pollutant sources and identify effective improvement projects. Traditional ambient water quality sampling methods can be limited because the typical indicators of pollutant sources might be diluted or rapidly attenuated. For example, in this study, ambient concentrations of CBOD5 and ammonia were not high enough to conclusively identify sewage as a pollutant source in Sandy Creek Tributary A. Visual inspection and microbial source tracking were required to identify this important and fixable pollutant source. The study also emphasized the need to understand urban stream hydrology when diagnosing water quality problems. Although pollutants exert oxygen demand, the ability of urban streams to reaerate themselves is an important factor in the stream oxygen budget (Blaszczak and others, 2019). Shallow groundwater tends to be low in dissolved oxygen, and so surface water â€“ groundwater interactions can influence in-stream oxygen concentrations (Harvey and others, 2013). Thermal imaging represents an innovative method for identifying groundwater seeps to streams. This method is most effective in streams that receive groundwater inputs as discrete seeps or springs rather than as highly diffuse inputs.

The City of Durham (NC) performed investigations of water and sediment quality issues in two streams. Multiple investigative methods showed that Sandy Creek Tributary A dissolved oxygen was affected by both external pollutant sources and urban hydrologic impacts. In Warren Creek, risk assessments showed that PAH and metals concentrations were not of concern to human or ecological health. Recommended projects included eliminating pollution, hydrologic improvements, and MS4 control measures.

SpeakerBell, Clifton

Presentation time

14:00:00

14:25:00

Session time

13:30:00

15:00:00

TopicIntermediate Level, Research and Innovation, Stormwater and Green Infrastructure, Watershed Management, Water Quality, and Groundwater, Wet Weather

Author(s)

Bell, Clifton

Author(s)Clifton F. Bell1; Tamara Sorell2; John V. Loperfido3</sup

Author affiliation(s)Brown and Caldwell, Richmond, VA1; Brown and Caldwell, Brookline, NH2; Public Works Department, City of Durham, NC3

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2022

DOI10.2175/193864718825158621

Volume / Issue

Content sourceWEFTEC

Word count14

Description: Watershed Science Improves Environmental and Regulatory Outcomes: A Case Study with...

Watershed Science Improves Environmental and Regulatory Outcomes: A Case Study with Phosphorus in the Midwest

Abstract

The City of Rochester operates a 24-MGD wastewater treatment plant (WWTP) that discharges to the South Fork of the Zumbro River in southeastern Minnesota. Although the WWTP has removed phosphorus for decades, preliminary modeling suggested the waste load allocation would need to be cut by more than 50% to achieve lake and river eutrophication standards. The city worked with the Minnesota Pollution Control Agency (MPCA) and other partners to evaluate the underlying watershed science and determine what was necessary to protect designated uses. The project involved three major components:
- development of a site-specific phosphorus criterion for Lake Zumbro;
- recalibration and adjustment of the watershed model to improve simulation of phosphorus sources and transport; and
- development of equitable point and nonpoint source implementation scenarios. The outcome was a modest reduction from the current waste load allocation, which will require that the city maintain its excellent long-term performance with phosphorus removal. However, this represents a much more favorable and affordable regulatory outcome than initially proposed and will give the city much-needed flexibility in the nature and timing of future plant improvements.

The City of Rochester operates a 24-MGD wastewater treatment plant that discharges to the Zumbro River in southeastern Minnesota. The City faced the possibility of deep cuts in its phosphorus allocations driven by Minnesota’s lake and river eutrophication standards. The City had questions about whether this costly reduction in allocation was necessary to protect beneficial uses of river and lake. This presentation will describe how the City worked with the Minnesota Pollution Control Agency (MPCA) and other partners to evaluate the underlying science and achieve an environmentally-protective and affordable outcome.

SpeakerBell, Clifton

Presentation time

13:52:00

14:14:00

Session time

13:30:00

15:00:00

SessionLess Nutrient Loading and Phos-For-Us

Session number311

TopicNutrients, Policy and Regulation, Watershed Management, Water Quality, and Groundwater

Author(s)

Clifton Bell