NEHA April 2024 Journal of Environmental Health

The April 2024 issue of the Journal of Environmental Health (Volume 86, Number 8), published by the National Environmental Health Association.

JOURNAL OF Environmental Health Dedicated to the advancement of the environmental health professional Volume 86, No. 8 April 2024


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JOURNAL OF Environmental Health Dedicated to the advancement of the environmental health professional Volume 86 No 8 ;r5l



Estimating Natural Attenuation of Nitrate and Phosphorus From Onsite Wastewater Treatment Systems....................................................................................................8 A Census of Federal and State Food Codes for Language Involving Reuse and Multiuse Containers ........................................................................................................... 20

Estimating the attenuation of nutrients in groundwater from onsite wastewa- ter treatment systems is di”cult due to the costs and uncertainty associated with


determining site-specific degradation rates, groundwater flow paths, and aquifer hydraulic properties. This month’s cover article, “Estimat- ing Natural Attenuation of Nitrate and Phos- phorus From Onsite Wastewater Treatment Systems,” assesses a new model created within the Montana Department of Environmental Quality to estimate site-specific nutrient fate when more complex methods are not techni- cally or logically feasible. See page 8. Cover images © iStockphoto: StockSolutions

Decoding Training Needs: Exploring Demographic Data to Understand Retail Food Regulatory Workforce Composition and Inform Capacity Building................................ 34

Building Capacity: Building Capacity by Applying the Eisenhower Matrix ................................. 42

Direct From ATSDR: An Update on the All-Hazards Approach for the ATSDR Emergency Management Unit ..................................................................................................... 44 Direct From CDC/Environmental Health Services: EH Nexus: CDC’s Communication Network for Environmental Health Professionals ......................................................................... 48

The Practitioner’s Tool Kit: The Art and Science of Inspection: Part Two ..................................... 50



AAS Davis Calvin Wagner Award........................... 5 Environmental Health and Land Reuse Certificate Program .............................................. 32 Hedgerow Software, US, Inc. .................................. 2 HS GovTech.......................................................... 60 JEH Advertising ....................................................57 NEHA CP-FS Credential ......................................58 NEHA Credentials .................................................. 7 NEHA Endowment Foundation Donors .............. 33 NEHA Job Board................................................... 32 NEHA Membership ................................................ 4 NEHA REHS/RS Study Guide............................... 18 NEHA/AAS Scholarship Fund Donors ................. 19 NEHA-FDA Retail Flexible Funding Model Grant Program ..........................................59 NEHA/NSF Walter F. Snyder Award ....................... 5

Resource Corner........................................................................................................................ 41

Environmental Health Calendar ...............................................................................................58


President’s Message: The Essential Functions of Local and State Environmental Public Health: How Do We Sustain and Rebuild Capacity? ...................................................................... 6

Special Listing ........................................................................................................................... 52

NEHA 2024 AEC....................................................................................................................... 54 NEHA News .............................................................................................................................. 56


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in the next Journal of Environmental Health don’t miss  Examining Food Safety Inspections: Do They Meet the Grade to Protect Public Health?  Impact of Poverty Status on Blood Lead Levels Among Individuals in the United States, 2017–2018  Incorporating Novel Methods Into a Standard Environmental Legionnaires’ Disease Investigation

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An open access journal published monthly (except bimonthly in January/ February and July/August) by the National Environmental Health Association (NEHA), 720 S. Colorado Blvd., Suite 105A, Denver, CO 80246-1910. Phone: (303) 802-2200; Internet: E-mail: Volume 86, Number 8. Yearly print subscription rates: $160 (U.S.) and $200 (international). Single print copies: $15, if available. Claims must be filed within 30 days domestic, 90 days foreign, © Copyright 2024, NEHA (no refunds). Opinions and conclusions expressed in articles, columns, and other contributions are those of the authors only and do not reflect the policies or views of NEHA. NEHA and the Journal of Environmental Health are not liable or responsible for the accuracy of, or actions taken on the basis of, any information stated herein. NEHA and the Journal of Environmental Health reserve the right to reject any advertising copy. Advertisers and their agencies will assume liability for the content of all advertisements printed and also assume responsibility for any claims arising therefrom against the publisher. Advertising rates available at The Journal of Environmental Health is indexed by Clarivate, EBSCO (Applied Science & Technology Index), Elsevier (Current Awareness in Biological Sciences), Gale Cengage, and ProQuest. The Journal of Environmental Health is archived by JSTOR ( jenviheal). Full electronic issues from present to 2012 available at All technical manuscripts submitted for publication are subject to peer review. Visit for submission guidelines and instructions for authors. To submit a manuscript, visit Direct all questions to Periodicals postage paid at Denver, Colorado, and additional mailing offices. POSTMASTER: Send address changes to Journal of Environmental Health , 720 S. Colorado Blvd., Suite 105A, Denver, CO 80246-1910.

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Volume 86 • Number 8

Honoring a history of advancing environmental health. Walter F. Snyder was a pioneer in our field and was the cofounder and first executive director of NSF. He embodied outstanding accomplishments, notable contributions, demonstrated capacity, and leadership within environmental health. Do you know someone like that? Nominate them for the Walter F. Snyder Award for outstanding contributions to the advancement of environmental health. This award is cosponsored by NSF and NEHA. Nomination Deadline: May 1, 2024 snyder-award Walter F. Snyder Award

Davis Calvin Wagner Award

Do you know an exceptional diplomate of the American Academy of Sanitarians (AAS) who is a leader who shows professional commitment, outstanding resourcefulness, dedication, and accomplishments in advancing the environmental health profession? Nominate them to be recognized with the AAS Davis Calvin Wagner Sanitarian Award. Nomination deadline: April 15, 2024


April 2024 • Journal of Environmental Health


Open Access


The Essential Functions of Local and State Environmental Public Health: How Do We Sustain and Rebuild Capacity?

Tom Butts, MSc, REHS

L ocal and state environmental health departments are at the front line of detecting and responding to environ- mental health risks. Their responsibilities in- clude surveillance of disease vectors such as mosquitoes and ticks, monitoring water and air quality, regulating waste management, inspecting housing conditions, controlling the spread of zoonotic diseases, and assur- ing food safety. We as environmental health professionals and these departments act as a bridge between scientific research, public policy, and community health. I reflect on the collaboration that existed and benefited communities I worked in when I started as an environmental health spe- cialist after college. There were a couple of resources provided by the state health depart- ment that were invaluable at the time but no longer exist. The first was access to a state analyti- cal chemistry laboratory where, with a phone call, we could drop o a sample of an unknown suspect chemical from an illegal hazardous waste dumping incident. We were met by THE state chemist and in a short time, we would get a call describing the contents of the sample. We could then work with our local fire department, law enforcement, and state hazardous waste agency to find ways to have the responsible parties properly manage that waste or to have the local authority miti- gate the hazard. Over time the free access was changed to a pay-for-your-sample system (the laboratory became cash-funded). Other resources from federal agencies—such as U.S. Environmen- tal Protection Agency on-scene coordinators with the ability to have contractors do the

ing, and Medicine in Washington, DC, it was shared that the U.S. has lost a lot of its capac- ity to track insects (NPR, 2023). According to Erin Staples, a medical epidemiologist with the Centers for Disease Control and Preven- tion, every state in 1927 had an entomolo- gist working to control insect populations and malaria. In 2022, there were just 16 state entomologists, which means that our abil- ity to monitor viruses such as West Nile is sparse. She went on to say, “We’re not getting great information because we haven’t main- tained our infrastructure.” The workshop focused on arboviral threats, which are mosquito-borne and tickborne viruses that can cause harm to humans. Trop- ical diseases that were once considered far away from the U.S. are now creeping into new areas of the U.S. In 2023, the U.S. saw locally transmitted cases of malaria and a skin dis- ease from tropical parasites. A Zika outbreak occurred in Florida and Texas in 2016–2017, and dengue has spread locally in the U.S. every year for more than one decade. The spread of vectors and zoonotic diseases is a growing concern due to climate change and urbanization. Local health departments conduct surveillance for vectorborne diseases such as West Nile virus and Lyme disease, implement control measures such as mosquito abatement, and educate the public about pre- vention. State health departments coordinate these eorts, provide resources, and oer expertise. Limited funding and staŸng chal- lenges can, however, hinder these activities. A lack of focus (and funding) on preven- tion and preparedness puts communities at risk as new threats emerge. It seems we often are in catch-up mode. I also see the siloing

The capacity and authority of local and state environmental public

health agencies in the U.S. have faced challenges and reductions.

dirty work—became a regularly used resource. This change was probably a net positive in terms of risk mitigation from an incident, but it changed local–state relationships and roles. The other resource that was indispens- able early in my career was access to a state entomologist. This fountain of knowledge was also accessible with a quick phone call and saved countless hours of research when confronted with bug-related challenges large or small. This resource was key as West Nile virus spread across the county in the early 2000s. That capacity gradually slipped away as the entomologist retired and the role became a smaller and smaller part-time responsibility and less accessible. I was not surprised but was disappointed just the same when I listened to an NPR story about the ever-shrinking number of state entomologists and the lack of focus on prevention and pre- paredness (NPR, 2023). During a 2-day workshop held at the National Academies of Sciences, Engineer-


Volume 86 • Number 8

of functions into disease control units or divisions as a reduction in capacity versus maintaining that operational knowledge in a broader group that includes environmen- tal health specialists. Further, there are other areas where there are great opportunities for improvement but obstacles exist in taking appropriate action. Water pollution poses a significant risk to public health through contaminants like lead, industrial chemicals, and agricultural runo. Local departments are often responsible for regular water quality testing and enforcement of regulations to ensure safe drinking water. State agencies develop broader water quality standards and oversee local compliance but face funding and stang challenges. Other factors that complicate assuring safe water include aging infrastructure, emerging con- taminants, and balancing industrial and agri- cultural interests with public health. The capacity developed during the COVID- 19 pandemic to identify and respond might not be sustainable without ongoing funding (e.g., federal, state, local). Rapid urbanization and global travel pose challenges in control- ling pathogen spread, necessitating more robust surveillance and response systems. The eectiveness of local and state envi- ronmental health departments is often con- strained by limited resources, stang, and funding. Climate change exacerbates many environmental health issues, requiring adap- tive strategies and more resources. Further-

more, the need for intersectoral collaboration is critical, as environmental health is inter- twined with sectors like housing, urban plan- ning, and agriculture. The capacity and authority of local and state environmental public health agencies in the U.S. have faced challenges and reductions, particularly in responding to vector control issues, air quality, water quality, food safety, and nuisance conditions. Here are several key trends and examples that are of concern: • Workforce development and organiza- tional competencies: Many state public health agencies have identified workforce development as a critical area, focusing on training, education, recruitment, reten- tion, and rebuilding clinical and laboratory capacity. Additionally, organizational com- petencies—including funding strategies, resource management, and leadership— are priority areas for a majority of states. Are there opportunities to elevate environ- mental health practice as well? • Legal and policy challenges: These chal- lenges can take a variety of forms. Arizona, Florida, Georgia, Indiana, Kansas, Mon- tana, Ohio, and Texas have implemented policies that limit public health authority. These limitations include restrictions on quarantine, stripping local health depart- ments of emergency response authority, prohibiting vaccination requirements at state universities and hospitals, and shifting power to legislatures. Legal challenges in

states like California, Kentucky, Louisiana, and Virginia have also arisen, particularly around restrictions on religious gatherings and public health recommendations. These trends and examples illustrate the complex challenges facing local and state environmental public health agencies in the U.S. They reflect a combination of workforce, legal, policy, and funding issues, all of which impact the ability of these agencies to eec- tively respond to public health needs. On the brighter side of things, the inclu- sion of environmental health themes in improvement plans for local and state health departments across the U.S. reflects a grow- ing awareness of the essential role the envi- ronment plays in public health. By address- ing environmental factors, these plans aim to create healthier communities and a more sustainable future. I hope there are opportu- nities for environmental health practitioners to have active roles in this work.

Reference NPR. (2023, December 15). The U.S. is un- prepared for the growing threat of mosquito- and tick-borne viruses . sections/health-shots/2023/12/15/1219 478835/arboviruses-mosquito-tick-borne- viruses-tropical-disease

Stand out in the crowd. Show the world you are the environmental health expert you know you are with a credential. You might even earn more or get promoted.


April 2024 • our9-l o2 9@5ro9me9>-l e-l>4


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Estimating Natural Attenuation of Nitrate and Phosphorus From Onsite Wastewater Treatment Systems

Eric Regensburger, MS Water Quality Planning Bureau Montana Department of Environmental Quality

tion can be complex, require significant data collection, or use average values that do not account for site-specific conditions. Quanti- fying the contributions of OWTS nutrients to groundwater and surface water is important for many facets of environmental and human health protection. To facilitate the implementation of state water quality standards, a quantitative tool to estimate nutrient loading from OWTS to surface waters was developed. The Method for Estimating Attenuation of Nutrients from Septic Systems (MEANSS) was created within the Montana Department of Environmental Quality primarily for use in OWTS permit- ting, nutrient trading, and for total maximum daily load development. MEANSS provides an option to estimate site-specific nutrient fate when more complex methods are not technically or logistically feasible.

b=>r-/> Estimating the attenuation of nutrients (e.g., nitro- gen, phosphorus) in groundwater from onsite wastewater treatment sys- tems (OWTS) is dicult due to the costs and uncertainty associated with determining site-specific degradation rates, groundwater flow paths, and aquifer hydraulic properties. Some available methods allow users to specify natural degradation rates for nutrients from OWTS but provide inadequate guidance on how to determine those rates. Other methods use a mechanistic approach with numerous variables and equations that are known to a‚ect nutrient attenuation but are necessarily complex and dicult to use for assessing hundreds or thousands of septic systems, as is often needed for regulatory applications. A spreadsheet analysis, the Method for Estimating Attenuation of Nutrients from Septic Systems (MEANSS), has been developed within the Montana De- partment of Environmental Quality to provide a relatively simple method of estimation with minimal data requirements. MEANSS is an empirical method designed to estimate the load of nutrients that will migrate to groundwater and surface water from OWTS sources. MEANSS provided comparable esti- mates of nitrogen and ortho-phosphorus attenuation below and downgradi- ent of OWTS when evaluated against several field studies, a GIS-based nitro- gen loading model, a mechanistic model, and a watershed model. Keywords: wastewater, nitrogen attenuation, phosphorus attenuation, septic system, nutrients


Development MEANSS was developed to meet three cri- teria: 1) to be easy to understand and use, 2) to use accessible and existing informa- tion, and 3) to use site-specific information that incorporates factors known to control natural attenuation of nutrients. MEANSS uses steady-state conditions as a simplify- ing condition; it does not account for the lag time needed for the treated wastewater from an OWTS to migrate into the groundwater and eventually into surface water. Another simplifying condition is that all the treated wastewater is assumed to enter the user-spec- ified receiving surface water; thus, there is no factor included for wastewater loads that do not discharge to the surface water due to local groundwater and surface water interac- tions. The user can, however, easily incorpo-

Introduction In 1990, approximately 25% of the U.S. popu- lation used onsite wastewater systems (com- monly known as septic systems) to dispose of household wastewater; 1990 was the last year this information was collected by the U.S. Census Bureau (2021). In Montana, usage was 37.5%. The nutrients discharged from onsite wastewater treatment systems (OWTS) can create both groundwater and

surface water pollution that aˆects both human health and aquatic life (Dubrovsky et al., 2010). Determining the amount of these nutrients (nitrogen and phosphorus) dis- charged from OWTS that eventually impact groundwater and surface water is diŒcult for many reasons, but primarily the diŒculty is due to the complex site-specific reactions that control natural attenuation of both nutrients. Existing methods to estimate that attenua-


Volume 86 • Number 8

tional) treatment (Heatwole & McCray, 2007; Howarth et al., 2002; Montana Department of Environmental Quality, 2015; Morgan & Everett, 2005; Morgan et al., 2007; Toor et al., 2020). As nitrate is the primary form of OWTS nitrogen that impacts groundwater and surface water, MEANSS is designed to estimate the denitrification rate after waste- water has been treated and discharged from the drainfield. While there could be some minor denitrification (approximately 10%) immediately below a properly operating drainfield (Costa et al., 2002; Lowe, 2007; Rosen et al., 2006), denitrification primarily occurs after the treated wastewater migrates away from the drainfield. For denitrification to occur beyond the drainfield, a suitable environment must exist. The necessary factors include: 1) tem- perature near or above 10 ºC; 2) an adequate carbon source that serves as food for the bacteria (available carbon is related to the soil organic matter content); 3) an anoxic environment with an oxygen range of <1–2 mg/L; and 4) the correct bacteria to utilize the oxygen atoms in the nitrate compound. A riparian zone with shallow groundwater is the most common natural environment that has these conditions (Gilliam, 1994; Gold & Sims, 2000; Harden & Spruill, 2008; McDowell et al., 2005; Rosenblatt et al., 2001). Although a literature review did not provide any specific lower limit of carbon concentration below which denitrification does not occur, an adequate carbon source is cited as the most common limiting factor for denitrification (Gold & Sims, 2000; Kobus & Kinzelbach, 1989; Rivett et al., 2008). Due to this finding, MEANSS accounts for the carbon limiting factor using site-specific soil characteristics. As fine-grained soils are more likely to con- tain two of the conditions necessary for deni- trification—anoxic conditions and carbon— they typically provide better denitrification conditions than coarse-grained soils (Briar & Dutton, 2000; Mueller et al., 1995; Tesoriero & Voss, 1997; Umari et al., 1993). Ander- son (1998) used results from several studies to show a Pearson correlation coecient ( r ) of .91 between denitrification rates and soil organic content. Another study by Ricker et al. (1994) used this relationship to estimate the amount of denitrification beneath drain- fields as 15% for sandy soils and 25% for finer


Plan View Schematic of the Method for Estimating Attenuation of Nutrients From Septic Systems (MEANSS) Parameters


30.5 m

Hydrologic Soil Group B

100 m

Hydrologic Soil Group C (>15% CaCO 3 )


Not to scale

Note. CaCO 3 = calcium carbonate.

rate such a factor into the results of MEANSS in areas where information on the groundwa- ter and surface water interaction is available. Also, groundwater dilution eects on concen- trations are not accounted for because total loads reaching surface waters are sucient for most applications. Separate groundwater dilution calculations can be used in conjunc- tion with MEANSS to estimate groundwater concentrations.

temperature climates than Montana, however, the nitrogen attenuation values might need to be adjusted and validated for use in MEANSS. The factors that aect the natural attenuation of nitrogen and phosphorus are described here to provide the basis for MEANSS. Nitrogen Attenuation Factors Nitrogen in raw domestic wastewater that is discharged to a septic tank is in the form of ammonia primarily (Lowe et al., 2010). Dis- posal of untreated wastewater in a properly constructed and sized drainfield typically will provide sucient oxygen and naturally occurring bacteria to convert the ammonia to nitrite and then quickly to nitrate. Conven- tional OWTS are not designed to complete the final step of nitrogen treatment—denitri- fication—which is the conversion of nitrate to nitrogen gas. Studies and water quality regulations com- monly assume that most or all the ammonia in the raw wastewater is converted to nitrate after septic tank and drainfield (conven-

Factors Controlling Nutrient Attenuation

Although many variables control the natu- ral attenuation of nitrogen and phosphorus that are discharged from OWTS, the variables that control attenuation the most—based on a search of the literature—were used in MEANSS (i.e., soil type, soil calcium car- bonate [CaCO 3 ] content, and distance to surface water). MEANSS was developed and validated for cold climates similar to Mon- tana (Supplemental Figure 1, jeh-supplementals). In significantly dierent


April 2024 • Journal of Environmental Health


soils. Both Long (1995) and Roeder (2008) used soil types to estimate total nitrogen reductions from OWTS discharges. The hydrologic soil group (HSG), as defined by the Natural Resources Conserva- tion Service (NRCS, 2019), is divided into four groups (A, B, C, and D) and is used in MEANSS to account for soil-related anoxic conditions and the relative amount of carbon in soils. Although NRCS uses additional cri- teria for the HSG designation, the amount of clay is an important part of the designation and generally uses the following criteria: • Group A soils have <10% clay materials. • Group B soils have 10–20% clay materials. • Group C soils have 20–40% clay materials. • Group D soils have >40% clay materials. Soils with higher clay content tend to have more carbon and thus can provide an envi- ronment that is better for denitrification. Clay soils also have lower permeability rates and lower porosity, which slows the wastewa- ter migration rate and allows more time for denitrification to occur. As such, MEANSS uses the HSG to estimate the relative amount of clay and carbon in the soil and correlates increased denitrification rates to higher soil clay content. Travel time in the environment (primar- ily in groundwater) is another factor that has been correlated to denitrification. Because nitrate persists in the environment, it has more time to encounter conditions conducive to denitrification (Kroeger et al., 2006). In MEANSS, however, distance is used instead of travel time because it is easier to measure dis- tances than the three parameters that control groundwater travel time: hydraulic gradient, hydraulic conductivity, and e™ective porosity. Increased distances from surface water also allow for deeper groundwater flow, which increases the chances of encountering anoxic conditions that are conducive to denitrifica- tion (Dubrovsky et al., 2010). Review of the existing literature presented in this article provided three factors that are used in MEANSS to estimate denitrification: 1) the predominant HSG beneath the drain- field, 2) the predominant HSG in the riparian zone of the receiving surface water, and 3) the distance between the drainfield and the receiving surface water. The nitrogen reduc- tion values applied to these characteristics are presented in the Parameters subsection within the Methods section.


Nitrate Attenuation Factors for Onsite Wastewater Treatment System Discharges to Soil

% Nitrate Reduction *

Scoring Category 1

Scoring Category 2

Scoring Category 3

Hydrologic Soil Group at Drainfield

Hydrologic Soil Group Within 30.5 m of Surface Water

Distance to Surface Water (m)





10 20 30 50

30.6–152.5 152.6–1,525 1,526–6,100



*The total nitrate reduction is the sum of the individual reductions for Category 1 + Category 2 + Category 3. For example, a drainfield in a hydrologic group C soil (20% reduction) that drains to a surface water with hydrologic soil group B riparian soil (20% reduction) and is 100 m from the surface water (10% reduction) would reduce its nitrate load to the surface water by 50% from the original load discharged from the drainfield (Figure 1).

in each soil type. The relation between soil CaCO 3 and phosphorus adsorption is valid for soils with typical pH values. In some soils that have unusually high pH values (typi- cally >8), however, phosphorus adsorption is higher in calcareous soils than similar soils with more neutral pH values (Buckman & Brady, 1972). When these high-pH soil con- ditions exist, the MEANSS user can adjust and increase the amount of attenuation in the analysis for the calcareous soils. Using a similar logic as described for nitrate, distance is used as a criterion for phosphorus attenuation. For the same dis- tance, however, a larger amount of reduc- tion is applied to phosphorus than nitrate in MEANSS. Phosphorus is treated di™er- ently because wastewater plumes with high phosphorus concentrations are less mobile than nitrogen, have been found to extend a relatively short distance from the source, and create high concentrations of phosphorus in soils immediately below drainfields with low levels beyond that location (Gold & Sims, 2000; Lombardo, 2006; Makepeace & Mlad- enich, 1996; Reneau et al., 1989; Robertson et al., 1998). Riparian areas, where anaerobic conditions often exist that are conducive to denitrifica- tion, provide a poor environment for soil adsorption and precipitation of phosphorus (Vought et al.,1994). Therefore, riparian soil

Phosphorus Attenuation Factors Phosphorus has lower mobility than nitro- gen and is removed in soils by two primary processes: adsorption and precipitation. The vadose zone is considered the primary loca- tion for phosphorus attenuation due partially to the negative soil moisture potentials that push the treated wastewater into the finer soil interstices and promote phosphorus adsorp- tion and precipitation (U.S. Environmental Protection Agency [U.S. EPA], 2002). Finer- grained soils also tend to impede phosphorus migration more than coarser soils primarily due to their greater surface area that provides more locations for adsorption. The HSG of the predominant soil beneath the drainfield is used to determine the relative amount of fine-grained soil. MEANSS does not distin- guish between precipitation and adsorption; instead, it applies a single reduction factor combining the two processes. Noncalcareous soils impede the movement of phosphorus more than calcareous soils because calcareous soils commonly main- tain neutral pH levels where phosphorus precipitation does not readily occur (Lom- bardo, 2006; Lusk et al., 2011; Robertson et al., 1998). Lombardo (2006) defined calcare- ous soils as soils containing >15% CaCO 3 and noncalcareous soils as those containing <1% CaCO 3 . MEANSS uses these CaCO 3 divisions to adjust the amount of attenuation occurring


Volume 86 • Number 8

instances, users will have to decide how best to estimate this value. The MEANSS spreadsheet for nitrate attenuation is presented in Table 1 and the spreadsheet for phosphorus attenuation is presented in Table 2. Model Performance The accuracy of MEANSS was evaluated by comparing it to: a) four site-specific ground- water OWTS nitrate studies, b) two OWTS nitrate attenuation models, and c) the Soil and Water Assessment Tool (SWAT) water- shed model. A lack of adequate existing phos- phorus studies that were of su”cient quality to validate MEANSS limited the evaluation of MEANSS phosphorus attenuation estimates to the SWAT watershed model. For evaluating MEANSS performance, the estimated nitrate and ortho-phosphorus (ortho-P) loads discharged from a single-fam- ily OWTS were assumed to be 13.8 and 2.92 kg/year, respectively. These loads are based on averages of published treated wastewater char- acteristics (Montana Department of Environ- mental Quality, 2015; U.S. EPA, 2002). Validation Several locations around the U.S. were identi- fied as locations where the MEANSS model could be validated. Each is detailed in this section. For each, the percent diŒerence between the OWTS load and the load esti- mated by MEANSS was calculated as: (OWTS LOAD MEANSS – OWTS LOAD CASE STUDY )/ (OWTS LOAD CASE STUDY) ) × 100 Site 1 (Lolo, Montana) The study site (Boer, 2002) is a low-density residential area near Lolo, Montana. It cov- ers 6.5 km 2 and contains >500 single-family OWTS. The study used site-specific data for the hydraulic conductivity, hydraulic gradi- ent, and groundwater nitrate concentrations to estimate the amount of OWTS-related nitrate migrating from the study area. After accounting for the natural background con- centration of nitrate in the groundwater (esti- mated as 0.1 mg/L nitrate-N), the total calcu- lated OWTS-related nitrate groundwater load was 6,103 kg/year. The MEANSS analysis used a 2008 data- base provided by the Missoula Valley Water Quality District to extrapolate the number of


Phosphorus Attenuation Factors for Onsite Wastewater Treatment System Discharges to Soil

% Phosphorus Reduction *

Scoring Category 1

Scoring Category 2

Hydrologic Soil Group at

Hydrologic Soil Group at Drainfield (CaCO 3 ≥ 15%)

Distance to Surface Water (m)

Hydrologic Soil Group at Drainfield (CaCO 3 ≤ 1%)

Drainfield (CaCO 3 > 1% and < 15%)

10 20 40 50 60 80













*The total phosphorus reduction is the sum of the individual reductions for Category 1 + Category 2. For example, a drainfield in a hydrologic group C soil with >15% CaCO 3 (40% reduction) and is 100 m from the surface water (50% reduction) would reduce its phosphorus load to the surface water by 90% from the load discharged from the drainfield (Figure 1). Note. CaCO 3 = calcium carbonate.

lowing text) are inputted into spreadsheets in the MEANSS model. The distance to the nearest receiving sur- face water is often the most uncertain param- eter required in MEANSS. The NHD informa- tion can provide the locations of ephemeral, intermittent, and perennial streams—but without a detailed groundwater flow map, it can be di”cult to determine the direction of groundwater movement and where shal- low groundwater will intersect surface water. When site-specific data are not available, one option is to assume the shortest distance between the OWTS and the nearest downgra- dient perennial surface water (as classified in the NHD) for the distance value (Figure 1). In MEANSS, the HSG used is based on the SSURGO classification of the predominant soil type beneath the drainfield and within 30.5 m of the receiving surface water. The 30.5-m stream buŒer is used as the default width to determine predominant soil types in the riparian area (Figure 1). The soil CaCO 3 content used in MEANSS is also based on values in the SSURGO data- base. In some areas, however, the CaCO 3 content is not available in SSURGO. In these

conditions are not used in the estimation of phosphorus attenuation as they are for nitrate. The review of the existing literature pro- vided three factors that are used in MEANSS to estimate phosphorus attenuation: 1) pre- dominant soil HSG in the drainfield area, 2) predominant soil CaCO 3 content in the drainfield area, and 3) distance between the drainfield and the receiving surface water. The phosphorus reduction values applied to these characteristics are presented in the Parameters subsection within the Methods section. Parameters The parameters used in MEANSS are avail- able via the following sources: GIS mapping for distance values, the National Hydrogra- phy Dataset (NHD or NHDPlus) from the U.S. Geological Survey (USGS) to determine appropriate receiving surface waters, and the Soil Survey Geographic Database (SSURGO) from NRCS to determine the HSG and soil CaCO 3 content. GIS analysis tools can be used to determine distance to surface water, soil characteristics at the drainfield, and soil HSG in the 30.5-m riparian buŒer (Figure 1). These data and others (described in the fol-


April 2024 • Journal of Environmental Health


single-family homes that existed at the time of the study: 558 homes. The analysis was run without using the second nitrate scoring category (soil type within 30.5 m of surface water) because the groundwater data was primarily from wells not within the 30.5-m riparian buer. Site 2 (Missoula, Montana) A study to estimate nitrate loading to the Bitterroot River from OWTS in and around the city of Missoula (Miller, 1996) was used for the second site. The study estimated the groundwater flux based on a groundwater model as 144,432 m 2 /day (Miller, 1991). Groundwater concentrations in the study were based on 8 groundwater wells and 11 groundwater seep samples collected in August 1995. Only the groundwater seeps were used in this analysis because they were closer to the river and therefore provided a better estimate of the nitrate concentrations near the river. The average nitrate + nitrite-N concentration of the 11 seeps was 1.04 mg/L (for the purpose of this analysis, the nitrate + nitrite concentration is assumed to consist entirely of nitrate). After accounting for the natural background concentration of nitrate in the groundwater (estimated as 0.1 mg/L nitrate-N), the total calculated OWTS-related nitrate groundwater load near the river was 49,551 kg/year. The MEANSS analysis used the 2008 data- base provided by the Missoula Valley Water Quality District to extrapolate the number of single-family OWTS that were contributing treated wastewater to the river in 1995: 4,315 homes. The analysis was run without using the second nitrate scoring category in Table 1 (soil type within 30.5 m of surface water) because the groundwater data was primar- ily from groundwater seeps not within the 30.5-m riparian buer. Sites 3 and 4 (Jordan Acres and Village Green Developments, Wisconsin) Two separate subdivisions in Wisconsin were monitored for nitrate impacts to ground- water (Shaw et al., 1993). Several multiport groundwater wells were used to measure the three-dimensional extent of nitrate impact on groundwater from selected portions of the subdivisions. The study used phosphorus and fluorescence in the multiport monitoring wells to separate the groundwater being impacted


Prickly Pear Watershed Used for Soil and Water Assessment Tool (SWAT) Model

Note. OWTS = onsite wastewater treatment system; USGS = U.S. Geological Survey.

from upgradient sources (i.e., deeper water) versus groundwater impacted by the subdivi- sions. The study calculated low, medium, and high groundwater flow rates beneath the sub- divisions to determine loading rates. Using the medium flow rates in the study, the calculated nitrate groundwater load from the Jordan Acres (26 homes) and Village Green (45 homes) OWTS was 240 and 616 kg/year, respectively.

MEANSS was run without using the sec- ond nitrate scoring category in Table 1 (soil type within 30.5 m of surface water) because the groundwater data was not collected within the 30.5-m riparian buer. ArcNLET (Site #2, Missoula, Montana) An analysis with the ArcGIS-Based Nitrate Load Estimation Toolkit (ArcNLET) was


Volume 86 • Number 8

instream concentrations of both total nitro- gen (TN) and ortho-P. For this comparison, the SWAT OWTS biozone algorithm—which is designed to simulate nitrogen, phosphorus, bacteria, and biological oxygen demand dis- charges from septic tank e¡uent (Jeong et al., 2011)—was not used and was replaced with the MEANSS estimates. The Prickly Pear watershed in central Mon- tana (Figure 2) was chosen for this project because it has a su§cient number of OWTS (approximately 1,010) for the size of the water- shed (531 km 2 ) to create noticeable impacts to stream water quality. In addition, there is little industrial or agricultural development in this watershed above the USGS streamflow gage near the town of Clancy that could potentially mask the impacts from OWTS. The SWAT model was developed using available information for elevation, land use and land cover, soils, and streamflow. The hydrology was calibrated to daily streamflow values measured near Clancy, Montana, at the USGS Prickly Pear Creek gage (06061500), which was also used as the outlet for the model. The streamflow calibration period was from 1992 through April 2013. Daily mea- sured streamflow was available for 82% of the calibration period. The daily error statistics of relative error, coe§cient of determination, and Nash–Sutcli©e e§ciency coe§cient were -9.0%, 0.76, and 0.76, respectively. All three statistics indicate a good match between mea- sured and simulated streamflow values. The instream water quality calibration data consisted of 20 TN and ortho-P sam- ples collected from 1999 through 2003 by USGS, along with three cold-weather samples (February, March, and April) collected by the Montana Department of Environmental Quality in 2013. Incorporating the steady-state MEANSS loading estimates into the daily-time step SWAT model showed that the lack of sea- sonal variation in MEANSS results created unreasonably large TN and ortho-P values in the winter months during baseflow con- ditions. To provide better seasonal variation for the MEANSS results, it was assumed that OWTS TN and ortho-P contributions to streams varied proportionally with stream- flow. This approach assumes a higher vol- ume of groundwater contribution (and cor- responding OWTS e¡uent contributions) to streams during the spring when ground-


Validation Results of the Method for Estimating Attenuation of Nutrients From Septic Systems (MEANSS)



OWTS Load (or % Reduction) Estimated From Site Information

OWTS Load (or % Reduction) Estimated From MEANSS

% Difference

1 2 3 4


7,008 kg/year 49,551 kg/year

5,312 kg/year 37,767 kg/year

-24 -24

237 kg/year 637 kg/year

289 kg/year 508 kg/year




19,023 kg/year

17,956 kg/year






16.3 kg/day 0.39 kg/day

22.4 kg/day 0.54 kg/day

37 38


*See Figure 3. Note. ArcNLET = ArcGIS-Based Nitrate Load Estimation Toolkit; ortho-P = ortho-phosphorus; OWTS = onsite wastewater treatment system; STUMOD = Soil Treatment Unit Model; SWAT = Soil and Water Assessment Tool; TN = total nitrogen.

used with the data from Site 2 (Rios et al., 2013). ArcNLET is a GIS-based program that estimates nitrate reduction from OWTS using groundwater velocity rates (calculated from site-specific hydraulic conductivity, hydrau- lic gradient, and porosity) and a user-defined denitrification rate. The same OWTS spatial information used for the MEANSS analysis was also used for ArcNLET. For the ArcNLET analysis, the hydraulic conductivities and hydraulic gra- dient from Miller (1991) were used. The hydraulic conductivity ranged from between 610 and 4,417 m/day, the hydraulic gradi- ent ranged from 0.001 to 0.003 m/m, and a porosity of 25% was estimated using the upper end of the range for sand and gravel aquifers (Driscoll, 1986). Moreover, the denitrification rate suggested in the ArcN- LET documentation (0.008 L/day) was used. Using those parameters, ArcNLET was used to estimate a total nitrate load to the Bitter- root River of 19,067 kg/year. All the MEANSS nitrate scoring categories were used for this comparison. STUMOD MEANSS was compared to a mechanis- tic model, Soil Treatment Unit Model (STUMOD), that calculates nitrogen reduc- tion below the drainfield in the vadose zone

(McCray et al., 2010). To provide comparable results, only the soil type at the drainfield category in MEANSS was used in the com- parison (Table 1). The 12 soil types included in McCray et al. (2010) were compared and the HSG for each of those soil types was esti- mated for comparison purposes. The nitrogen reduction values for STUMOD were estimated from cumulative probability graphs of Monte Carlo simulation results for a deep-water table (McCray et al., 2010). The STUMOD results were based on the following parameters: • hydraulic loading rate: 2 cm/day; •frigid/cryic temperature range (0–8 °C), which is comparable to Montana tempera- ture ranges (Supplemental Figure 1); • reduction estimated at 120-cm soil depth; • standard drainfield e¡uent of 60 mg/L as ammonium-N and 1 mg/L as nitrate-N; and • 50% value on the cumulative frequency distribution (i.e., one half the simulations showed greater reductions and one half the simulations showed lesser reductions). SWAT Model (Prickly Pear Watershed, Montana) The final validation method was a watershed model created using SWAT (Arnold et al., 1993). For this method, OWTS loading val- ues from MEANSS were incorporated into the SWAT simulation and calibrated to observed


April 2024 • our9-l o2 9@5ro9me9>-l e-l>4


water elevations and velocities are higher than during other months of the year when groundwater elevations recede. The annual loads estimated using MEANSS were pro- portionally divided on a monthly basis (the sum of the monthly loads remained equal to the MEANSS annual load) to match the monthly variation of streamflow at the USGS streamflow gage. Adjusting the MEANSS results for seasonal variation produced bet- ter calibration results. Results The validation results of each site or method compared with MEANSS are summarized in Table 3. The absolute average percent di€er- ence between MEANSS estimated loads and the loads estimated via other methods (not including STUMOD results) in Table 3 is 19%. Site 1 (Lolo, Montana) MEANSS was used to calculate a nitrate reduction of 41.5%, which provides a total nitrate load in groundwater of 5,312 kg/year from the 558 homes. The MEANSS load is 76% of the load estimated by Boer (2002), which was 7,008 kg/year. Site 2 (Missoula, Montana) MEANSS was used to calculate a nitrate reduc- tion of 43.7%, which provides a groundwater nitrate load of 37,767 kg/year from the 4,315 homes. The MEANSS load is 76% of the amount estimated by Miller (1996), which was 49,551 kg/year. Sites 3 and 4 (Jordan Acres and Village Green Developments, Wisconsin) MEANSS was used to estimate a 19.6% nitrate reduction at Jordan Acres (Site 3), which is equal to a groundwater load of 289 kg/ year. The MEANSS estimated load is 122% of the measured load, which was 237 kg/ year. MEANSS was used to estimate a nitrate reduction of 18.4% at Village Green (Site 4), which is equal to a groundwater load of 508 kg/year. The MEANSS estimated load is 80% of the measured load, which was 637 kg/year. ArcNLET (Site 2) The ArcNLET program estimated the nitrate load into the Bitterroot River as 19,023 kg/ year. The MEANSS estimated load is 17,956 kg/year, which is 94% of the ArcNLET cal- culated load. The MEANSS estimated load


Comparison of the Soil Treatment Unit Model (STUMOD) and the Method for Estimating Attenuation of Nutrients From Septic Systems (MEANSS) Nitrogen Reduction in the Vadose Zone Below the Drainfield

0 10 20 30 4 0 5 0 6 0 7 0 8 0 9 0 100






























S oil D es crip tion and E s timated H ydrologic S oil G roup

STU MOD (f rigid/cryic @ 120 cm )



Soil and Water Assessment Tool (SWAT) Model Calibration Results for Total Nitrogen (TN) and Ortho-Phosphate (Ortho-P) Using the Method for Estimating Attenuation of Nutrients From Septic Systems (MEANSS) to Estimate TN and Ortho-P Loading From Onsite Wastewater Treatment Systems to Prickly Pear Creek

1 x 10 3

75th Percentile Maximum Median 25th Percentile Minimum

1 x 10 2

1 x 10 1

1 x 10 0

1 x 10 -1

1 x 10 -2

1 x 10 -3

Note. Based on 23 dates of observed instream concentrations and 19 dates of observed instream loads in Prickly Pear Creek.


Volume 86 • Number 8

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