Wastewater treatment in the Croton, Catskill and Delaware watersheds, by a centralized wastewater treatment plant (WWTP) or by a septic system, has a direct impact on water quality in the watersheds and ultimately the quality of New York City’s source water. The programs that govern wastewater treatment in the watersheds also have an impact on the local ecosystem, in that effective wastewater treatment protects the land, the groundwater, and local streams from pollutants and/or excess nutrient loads. Finally, the wastewater programs have strong community vitality elements, in that a valuable public service is being provided at very low cost to watershed residents and businesses.
The west-of-Hudson (WOH) watershed has a population of approximately 46,500 that translates into a population density of 29 people per square mile, with 80 percent of the population served by septic systems (Meyer, 2018a). According to a count of residential tax parcels outside of sewered areas (data from K. Kane, NYC DEP, personal communication, 2019), there are about 23,000 septic systems in the WOH watershed. Only approximately 9,200 WOH residents are served by centralized wastewater treatment. In contrast, the east-of-Hudson (EOH) region has a population of approximately 201,500 residents, which corresponds to a population density of 520 people per square mile. Seventy-five percent of the residents are served by a septic system (Meyer, 2018b), with the balance, approximately 50,000 residents, served by centralized wastewater treatment. Compared to both WOH and EOH regions, New York City (NYC) has a population density of roughly 27,012 people per square mile with the vast majority of residents being served by a centralized WWTP.
Six parameters are regarded as priority pollutants for treatment of wastewater: total phosphorus (TP), total suspended solids (TSS), fecal coliforms, viruses, Giardia cysts, and Cryptosporidium oocysts (NYC DEP, 1993). The removal efficiency of these six parameters varies between septic systems and centralized wastewater treatment. Both processes are efficient in removing TSS and fecal coliforms. Phosphorus is present as phosphate (PO43-) in wastewater and is a nutrient for biological growth, and so a portion of the influent phosphorus is incorporated into the microorganisms responsible for organic degradation in both WWTPs and septic systems. The WWTPs constructed by the NYC DEP also include a chemical precipitation of phosphate by the addition of alum to precipitate solid AlPO4, and those solids are removed by the subsequent filters. Dissolved phosphorus passes through the septic tank of a passive septic system and enters the drainage or leach field, where it is metabolized by aerobic microorganisms in the soil, adsorbed to soil particles, or taken up by plants. However, the capacity of the soil in the leach field to retain phosphorus can eventually be exhausted, after which phosphorus-rich water can enter the environment (EPA, 2002). Hence, WWTPs that incorporate phosphate precipitation are more effective than septic systems at reducing concentrations of dissolved and total phosphorus and ensuring that this nutrient does not enter the reservoirs.
WWTP effluent is disinfected, and, therefore, more effective than septic systems in eliminating viruses and bacteria. Finally, the upgraded and new WWTPs were built with chemical addition for the precipitation of
phosphorus to very low levels and with microfiltration of 0.2 microns or less, which enhances their ability to remove Giardia cysts and Cryptosporidium oocysts and further removes any remaining particulate phosphorus in comparison to septic systems.
While not specified as priority pollutants by NYC DEP (1993), biochemical oxygen demand (BOD) and nitrogen are important constituents in the treatment of wastewater as both can exhibit considerable oxygen demand on receiving waters and can be toxic in the aquatic environment. BOD is a surrogate measure for the concentration of degradable organics in the wastewater; BOD5 is the standard reference value for quantifying the BOD in a liquid, and the test is five days at 20°C (Tchobanoglous and Schroeder, 1987). Secondary wastewater treatment is designed to remove at least 85 percent of the influent BOD5. Further, nitrogen in domestic wastewater is mostly present as ammonium (NH3), and in secondary treatment can be oxidized to NO3-; this conversion eliminates the oxygen demand that could be exerted in the reservoirs, but does not remove the nitrogen. Of the two nutrients (nitrogen and phosphorus), the limiting nutrient for biological growth in the NYC reservoirs (and in virtually all natural lakes) is phosphorus (Schindler, 1974; Carpenter et al., 1998), and so its elimination from the wastewater discharges (either from WWTPs or septic systems) is far more important than removing nitrogen.
The specific watershed protection programs that manage wastewater treatment include the Wastewater Treatment Plant Upgrade Program, the New Sewage Treatment Infrastructure Program, and a number of programs for replacement and proper maintenance of septic systems in the watersheds that provide NYC’s drinking water. The WWTP programs are extremely important because the majority of these plants discharge directly into streams or rivers that flow into the reservoirs that provide NYC’s drinking water. The septic system programs are also very important, even though septic systems indirectly affect water quality because such systems discharge into a leach field that completes the treatment of wastewater. If a septic system fails, it can lead to contamination of the streams and reservoirs that make up the water supply.
To comply with the filtration avoidance determination (FAD), the wastewater programs must protect water quality while enhancing community vitality. In the following descriptions of individual wastewater programs, the program’s effectiveness at meeting these objectives is discussed.
The WWTP programs are governed by the 1997 Memorandum of Agreement (MOA) signed by NYC DEP, upstate communities, and other interested parties. Prior to 1997, wastewater was managed according to the first FAD issued to NYC DEP by the U.S. Environmental Protection Agency (EPA) in 1993 in response to the 1989 Surface Water Treatment Rule, and by the 1953 Watershed Regulations that governed wastewater treatment in the Croton, Catskill and Delaware watersheds. The Watershed Rules and Regulations that were part of the 1997 MOA established standards for the design, construction, and operation of WWTPs. The Watershed Rules and Regulations specified that best available control technology for WWTPs should be sand filtration, disinfection, phosphorus removal, and microfiltration or treatment equivalent to microfiltration. Note that these specifications for wastewater treatment in the Croton, Catskill, and Delaware watersheds go beyond what is required of most WWTPs that discharge to surface waters in the United States. The Clean Water Act requires that municipal WWTPs meet the effluent limits consistent with secondary treatment (EPA, 2004). WWTPs plants in New York City employ secondary treatment and disinfection.1
WWTP Upgrade Program
When the MOA was signed, more than 100 WWTPs located both WOH and EOH required upgrades to comply with the Watershed Rules and Regulations. Of the 42 WWTPs in the WOH region, five are City-owned and account for approximately 40 percent of the WOH watershed’s total WWTP flow, while the rest are pri-
vately owned. The Wastewater Treatment Plant Upgrade Program required that all of these publicly- and privately-owned WWTPs be upgraded to tertiary treatment (see Box 8-1) regardless of location, with larger plants being upgraded first. The upgrade requirements included phosphorus removal, sand filtration, backup power, disinfection, microfiltration or the equivalent treatment, flow metering, and alarm telemetering. Since 1997, NYC DEP has funded the eligible costs of designing, permitting, and constructing upgrades required by the Watershed Rules and Regulations (WR&R) for all of the WWTPs in the watershed, which totaled $878 million between 1993 and 2019 (both capital and O&M costs, NYC DEP, 2019).
New Sewage Treatment Infrastructure Program and the Community Wastewater Management Program
The 1997 MOA identified 22 WOH communities that had failing septic systems near watercourses and/or reservoirs. These communities were prioritized for new treatment systems by considering the number of buildings, the number of failing septic systems, their proximity to streams, development density, soil characteristics, and their location within a 60-day travel time to a reservoir. The New Sewage Treatment Infrastructure Program, a voluntary program, was created to assist these communities by providing funding for the study, design, and construction of WWTPs, community septic systems, or septic maintenance districts. A community septic system is a system that treats wastewater from multiple structures; the system can be constructed such that each structure is equipped with a septic tank and a common leach field receives flow from the community’s septic tanks. Alternatively, one large, common septic tank and leach field can serve multiple structures, connected by a local collection system. A septic maintenance district establishes a geographical boundary in which fee-based maintenance is performed on all systems within the district.
Following construction of each project, NYC DEP entered into operation and maintenance funding agreements with each facility owner. The first six projects included the construction of WWTPs in five communities (Villages of Hunter, and Fleischmanns, the Town of Windham, and the Hamlets of Andes and Prattsville) and one sewer extension, which conveys flow from the Hamlet of Roxbury to the Grand Gorge WWTP. These projects were constructed and placed into service from 2005 through 2007, with NYC DEP providing $86.9 million, to treat the equivalent of approximately 1,750 septic systems, handling about 1.1 MGD of flow (Meyer, 2018a).
In 2012, the Community Wastewater Management Program was created to continue the New Sewage Treatment Infrastructure Program for the remaining 15 communities identified in the MOA. According to Meyer (2018a), NYC DEP has spent $93 million for planning, design and construction of projects for these communities. All 15 communities agreed to participate, and 10 of the 15 projects were completed by the end of 2016. The ten projects include two WWTPs, two sewer extensions, five community septic systems and one septic maintenance district. The five remaining Community Wastewater Management Program projects are for the communities of Shandaken, West Conesville, Claryville, Halcottsville, and New Kingston. Draft preliminary engineering reports for each of these communities have been completed; the status of the remaining projects is as follows:
- Shandaken, roughly 15 miles upstream of the Ashokan Reservoir, is moving forward with a septic maintenance district. NYC DEP approved a block grant of $6.77 million in May 2017, and, in 2019, NYC DEP issued the design approval for the project. The town has awarded the construction contract, and construction is scheduled to commence in 2020.
- Conesville, roughly 3 miles from the Schoharie Reservoir, has a NYC DEP-approved block grant of $8.41 million for a community septic system. NYC DEP received the proposed final design drawings in November 2019. Final stamped design plan sets and project bidding are anticipated in 2020.
- Claryville, approximately 4 miles from the Neversink Reservoir, has received a NYC DEP block grant of $8.65 million to create septic maintenance districts for the towns of Denning and Neversink. Pump-out and inspections of septic systems in Neversink’s hamlet of Claryville were completed in 2018. In 2019, the contractor completed construction on the Denning portion and will return in spring 2020 to complete final site restoration. NYC DEP issued design approval for the Neversink portion in May 2019 and construction commenced in November 2019. After winter shutdown, construction will resume in spring 2020.
- Halcottsville, roughly 5.5 miles from Margaretville, New York, anticipates completing the design and preconstruction for pumping stations, a sewer collection system, and a force main connection to the City-owned Margaretville WWTP. NYC DEP approved a block grant of $8.95 million in September 2017 for the project. The project is now in the preconstruction phase and submission of the 65 percent design drawings is pending resolution of siting issues for the pumping station. Bidding for construction is anticipated in 2020.
- New Kingston, roughly 6 miles from the Pepacton Reservoir, has NYC DEP approval and a $5.2 million block grant for a community septic system with 28 connections. The project is in the preconstruction phase with some land acquisition still pending. The project is expected to be bid for construction in 2020 or 2021.
The 2017 FAD also included the hamlet of Shokan in Ulster County, which is less than 1 mile upstream of the Ashokan Reservoir. Shokan reported a population of 1,183 in the 2010 census and a study to develop recommended options commenced in 2019.
Wastewater Treatment Plant Funding Commitment
The WWTP programs’ capital and operating costs to-date and projected expenditures through 2028 are presented in Table 8-1. This includes nearly $14 million in annual operation and maintenance (O&M) expenses for the private WWTPs and approximately $3.5 million in O&M for the New Sewage Treatment Wastewater Infrastructure Program. Future funding for the O&M of the City-owned WWTPs is not part of the Watershed Protection Program budget, although it is a NYC DEP expense. Indeed, NYC DEP is required to pay for the capital replacement of certain equipment at all public WWTPs and all public or private WWTPs that existed or were under construction on November 2, 1995; the equipment included is that required by the Watershed Rules and Regulations but not otherwise required by federal or state law.
TABLE 8-1 Past and Future Capital and Operation and Maintenance Costs for Wastewater Treatment Plant Programs
|Capital ($)||Operation and Maintenance ($)|
|Program||1993- 2019||Projected 2020-2028||1993- 2019||Ten-year Projections|
|City-owned WWTP upgrades||$271,264,000||N/A||N/Aa||N/Aa|
|Private WWTP upgrades||$462,169,000||$60,000,000||$144,891,000||$147,192,000|
|New Sewage Treatment Infrastructure Program||$199,986,000||N/A||$37,640,000||$34,840,000|
a Future funding for the City-owned plants is not considered part of the budget of the Watershed Protection Program, although it is part of NYC DEP’s overall budget.
SOURCE: NYC DEP (2019).
WWTP Compliance and Inspection Program
The current WWTP Compliance and Inspection Program is coordinated by the New York State Department of Environmental Conservation (NYS DEC) and NYC DEP, with milestones set forth in the Revised 2007 FAD and the 2017 FAD. The program is intended to ensure that WWTPs operate effectively and protect NYC’s source water. The program created the Watershed Enforcement Coordination Committee (WECC), which is tasked to address noncompliance, in a timely manner, through formal enforcement and/or compliance assistance. The NYC DEP’s water quality sampling program regularly monitors the effluent of all WWTPs in the watershed. Also, the WECC conducts four on-site inspections each year of the WWTPs that operate year-round and two on-site inspections of seasonal WWTP facilities.
The WECC is required to prepare semiannual reports summarizing the WWTP Inspection Program results, including any enforcement actions taken against a WWTP, and the results of the water quality sampling monitoring report. The WECC is also required to report any sewage spills exceeding 500 gallons to the New York State Department of Health, by email, within 24 hours of becoming aware of the spill.
Program Effectiveness to Date
Of the 42 WWTPs in the WOH region, all have been upgraded to tertiary-equivalent treatment. The WOH total permitted flow of the surface-discharging WWTPs is 7.23 MGD (see Table 8-2); the locations of the surface discharging plants are shown in Figure 8-1. These 26 WWTPs are regulated by individual State Pollutant Discharge Elimination System (SPDES) permits. The 37 non-City-owned WWTPs include seven new WWTPs constructed as part of the New Sewage Treatment Infrastructure Program.
Table 8-2 provides a summary of the WWTP flow that is surface discharged by basin, including the flow allowed by each plant’s SPDES permit and the average flow from 2014 through 2018. The difference between the SPDES-permitted flow and the recent average flow is the excess capacity available in the plants, which could allow for future development in the communities that the WWTPs serve—an important community vitality element. The sparsely populated WOH region ranges from 6 people per 100 acres in the Cannonsville basin to 2 people per 100 acres in the Neversink basin. The Neversink basin also has no WWTPs and the fewest septic systems, lower than the other watersheds by an order of magnitude. Also notable, the New Sewage Treatment Infrastructure Program (NIP in Table 8-2) has displaced 1,634 septic systems with WWTPs since construction for the program commenced in 2005, with the majority of septic displacement occurring in the Schoharie basin.
TABLE 8-2 Summary of 26 Wastewater Treatment Plants That Discharge to West-of-Hudson Surface Waterbodies
|Basin||2010 Population||Population/Acre||WWTP Flow (MGD)a||Annual Average Flow (MGD)b||Septics Displaced by NIP||Number of WWTPs||Number of Septic Systemsc|
SOURCES: Columns 2, 3: population metrics; Courtesy of NYC DEP, derived from U.S. Census data. Column 6: Septics displaced by NIP; NYC DEP (2019).
aSPDES-permitted flow; data courtesy of NYC DEP.
bAverage of 2014-2018 annual average flow; data courtesy of NYC DEP, average calculated by the Committee.
cBased on residential tax parcels that are completely outside existing and planned sewered areas and assumed to have a septic system. Courtesy of T. Spies, NYC DEP GIS Team, October 2018.
The EOH region has 69 WWTPs with a total permitted flow of 6.81 MGD; of these plants, 62 are surface-discharging (Figure 8-2). Upgrades of these 69 WWTPs are nearly complete, with a handful exploring the decommissioning of their WWTP and connecting to a nearby upgraded WWTP. It is also notable that these WWTPs are in the portion of the watershed in which the water is filtered prior to distribution to NYC.
Water Quality Metrics and Results
The wastewater program performance is reported, by WWTP, in SPDES compliance reports, in FAD annual reports, and a number of other outlets. The following summaries are presented by watershed using annual average data provided by NYC DEP and as reported in the 2016 Watershed Protection Program Summary and Assessment (NYC DEP, 2016).
Five WWTPs discharge into surface waters in the Cannonsville watershed. The phosphorus load from the WWTPs was over 5,500 kg total phosphorus per year in 1994 and has been reduced dramatically as the WWTP upgrades have been completed. The annual average loading from 2014 through 2018 in WWTP effluent in the Cannonsville watershed was 17 kg total phosphorus per year. The phosphorus loading by year from the WWTPs is presented in Figure 8-3. Plant upgrades were completed by August 2002 with the exception of the R. W. Harold Campus WWTP, where the upgrade to tertiary treatment was completed in 2004. As observable in Figure 8-3, a rapid decline in phosphorus loading coincides with the timing of these upgrades. The combined flow from the WWTPs increased from approximately 700 million gallons/year in 1994 to over 930 million gallons/year in 2018.
The performance of the WWTPs in the Cannonsville Reservoir watershed is also presented in Table 8-3, which shows that the actual treated flow is generally less than half of the SPDES-permitted flow for each plant. Table 8-3 also includes the total phosphorus limit for each plant given the Watershed Rules and Regulations limits, based on flow, and the 2014–2018 average total phosphorus in each plant’s effluent. The WWTPs in the Cannonsville watershed discharge an order of magnitude less phosphorus on a mass basis than the Watershed Rules and Regulations allow.
The 11 WWTPs in the Schoharie Watershed have a combined average flow of 0.711 MGD and a SPDES-permitted combined flow of 2.308 MGD. Two WWTPs in the Schoharie watershed are NYC DEP-owned plants, the Grand Gorge and the Tannersville WWTPs. Both plants were upgraded to
TABLE 8-3 Comparison of Cannonsville Reservoir Basin Wastewater Treatment Plant Permitted Flow and Total Phosphorus Concentrations Versus Actual Flows and Concentrations, 2014-2018
|WWTP||SPDES Permitted Flow (MGD)||Average Flow 2014-2018 (MGD)||WR&R TP Limit (mg/L)||Average TP Effluent Concentration 2014-2018 (mg/L)|
|R. W. Harold||0.010||0.003||1.0||0.169|
NOTE: SPDES = State Pollutant Discharge Elimination System, TP = total phosphorus, WR&R = Watershed Rules and Regulations.
SOURCE: Data provided by NYC DEP and analyzed by the Committee.
continuous microfiltration followed by ultraviolet (UV) disinfection prior to the year 2000. There are also four New Sewage Treatment Infrastructure Program WWTPs in the watershed: the Ashland, Hunter, Prattsville and Windham WWTPs. The phosphorus load from the 11 WWTPs has declined to approximately 5 percent of the pre-upgrade loading, despite a 35 percent increase in flow from these plants.
The four WWTPs in the Ashokan watershed have been upgraded to include continuous microfiltration and UV disinfection. The Pine Hill WWTP, owned by NYC DEP, was upgraded in 1999. The Timber Lake Camp WWTP and Olive Woods, LLC, were upgraded in 2005 and 2009, respectively. The Boiceville WWTP, part of the New Sewage Treatment Infrastructure Program, displaced 105 septic systems and commenced service in July 2010. The WWTP phosphorus loading from the plant has decreased to 2 percent of the pre-upgrade loading (Table 8-4). Also, the flow from WWTPs has declined by roughly half, even with the addition of the Boiceville WWTP.
There are five WWTPs in the Pepacton watershed (including two completed since 2004). NYC DEP upgraded the Margaretville WWTP to continuous microfiltration and UV disinfection in 1999. Under the New Sewage Treatment Infrastructure Program, NYC DEP funded the design and construction of the Andes WWTP, displacing 133 septic systems in 2005, and the Fleischmanns WWTP in 2007, displacing 295 septic systems. The phosphorus loading from WWTPs in this watershed has declined to less than 4 percent of the pre-upgrade loading and, given the addition of two new plants, the flow is roughly the same (Table 8-4).
The Grahamsville WWTP, owned by NYC DEP, is the only WWTP in the Rondout watershed. NYC DEP funded the upgrade of the Grahamsville WWTP to continuous microfiltration and UV disinfection; the upgrade was completed in 1998. The phosphorus loading discharged by the plant had declined approximately 90 percent since the upgrade (Table 8-4).
Table 8-4 summarizes the changes in WWTP flow and phosphorus loading that have occurred in the six WOH basins (excluding Neversink) since the addition of seven new WWTPs and the upgrading of all other WWTPs. The total flow discharged from WWTPs in the watershed increased approximately 24 percent in the 20-year time frame considered in the table, and yet the phosphorus loading from these plants is now only 2.3 percent of the loading prior to the plant upgrades.
TABLE 8-4 Summary of West-of-Hudson Wastewater Treatment Plant Phosphorus Loading to Watersheds
|Watershed||1998 WWTP Flow (MG/year)||Pre-upgrade Total Phosphorus (TP)a Load (kg/yr)||Average Flow 2014-2018 (MG/year)||Average Post-upgrade TPb Load (kg/yr)|
b Post-WWTP upgrade loading annual average data 2014-2018.
SOURCE: Data provided by NYC DEP.
From 2002 through September 2015, NYC DEP monitored eight WWTPs in the Catskill system for protozoa to verify the effectiveness of the WWTP upgrades in reducing loading of these pathogens. Samples were collected quarterly and resulted in 19 detections of Giardia in the 215 samples collected. Cryptosporidium oocysts were detected in three of the 215 samples. NYC DEP also monitored eight WWTPs in the Delaware system from 2002 through September 2015 quarterly for detection of protozoa. Giardia was detected in 32 of the 190 samples collected through 2010. For the balance of the sampling, Giardia detection dropped to one detection out of 76 samples. The reduction in detections from 2011 through September 2015 was believed to be the result of moving the sampling location where wildlife would have less access. Cryptosporidium oocysts were detected in four of the 190 samples collected through 2010 and none thereafter. The excellent solid/liquid separation accomplished by the membranes or dual sand filters described in Box 8-1 are presumably responsible for the low occurrence of detections.
The source water protection requirements of the FAD also included a number of septic system upgrade, replacement, and rehabilitation programs for the NYC DEP to implement. These programs include the Septic Rehabilitation and Replacement Program (for residences), the Small Business Septic System Rehabilitation and Replacement Program, the Cluster Septic System Program, and the Septic Maintenance Program. To date, NYC DEP has collectively committed over $100 million to these programs (Warne, 2018). The closer a septic system is to a stream or reservoir, the more likely it is to negatively affect water quality if it were to fail. An estimated 92 percent of the approximately 23,000 residential septic systems in the WOH watershed are within 700 feet of a watercourse, with the vast majority within 50 feet (Meyer, 2018a, slide 10).
A schematic and summary of a conventional septic system, which includes a septic tank and a soil adsorption system, is presented in Box 8-2. A properly designed, constructed, sited, and maintained conventional septic system will provide adequate treatment of wastewater and protect human health and the environment (EPA, 2002). However, there are many variables relating to influent properties and site characteristics that can cause a conventional septic system to inadequately treat septic influent or even fail; these are discussed later in this section. Septic systems and their performance were considered at length in the previous Academies report (NRC, 2000). Although the MOA does not specify the best available control technology for septic systems, the NRC (2000) report recommended aerobic treatment units (ATUs) followed by a conventional drainage field.
West-of-Hudson Septic System Program Descriptions
The septic system program in the WOH watershed allows for repair and replacement of septic systems that are either failing or deemed likely to fail, and it provides residents full reimbursement for the work. The Catskill Watershed Corporation (CWC) administers four different WOH septic programs, described in this section.
Septic Rehabilitation and Replacement Program
The Septic Rehabilitation and Replacement Program rehabilitates and replaces septic systems in residential, mixed-use, and commercial buildings with a flow of less than 1,000 gallons per day. This program addresses roughly 1.4 MGD of wastewater flow.
The CWC initially targeted septic systems located in the 60-day travel time area (see Figure 7-1), but then expanded the program with prioritization according to the potential for septic systems to impact the NYC water supply. Priority 1A are sub-basins within the 60-day travel time to distribution that are near intakes, while Priority 1B are sub-basins within the 60-day travel time to distribution that are not near intakes. Priority areas P3 through P9 are a function of the distance of the septic system to a watercourse ranging from within 50 feet
of a watercourse (P3) to from 300 to 700 feet of a watercourse (P9). More than 2,650 septic systems within 50 feet of a stream have been repaired or replaced (Meyer, 2018a, slide 11), which accounts for about half of all of the parcels in the WOH region (Meyer, 2018a, slide 10).
CWC seeks agreement with a homeowner and conducts inspections to determine if the septic system is functioning properly. A failing system can be repaired with select reimbursement from CWC if it is a primary or secondary residence. From 1997 to date, over 5,500 residential septic systems have been repaired or replaced under this program (Meyer, 2018a) and in 2018 this program was expanded to all WOH watershed homeowners (NYC DEP, 2018).
Small Business Septic System Rehabilitation and Replacement Program
The Small Business Septic System Rehabilitation and Replacement Program commenced in 2007 to fund the rehabilitation or replacement of failing septic systems serving eligible small businesses. CWC administers the program to reimburse eligible business owners 75 percent of the cost of repairs, up to a total reimbursement of $40,000. To be eligible, a failing commercial septic system must be within 700 feet of a watercourse or
within the 60-day travel time area. The business owner is responsible for the system/upgrade design, which must be approved by NYC DEP, and for the construction of the system/upgrade and for seeking reimbursement of costs. A total of 19 septic system rehabilitations/replacements have been funded since the program’s inception. In 2018, this program was expanded to include nonprofit corporations and eligible public facilities.
Cluster Septic System Program
The Cluster Septic System Program was created to provide the planning, design, and construction of community septic systems in 13 eligible communities seeking to connect multiple properties to a centralized treatment system; this program was established as a part of the 2007 FAD, and expanded the list of eligible communities from that originally established in the MOA. Although this program was intended to provide a more efficient way to manage wastewater and maintain systems, no community elected to establish a community septic system under the Cluster Septic System Program. However, as discussed earlier in this chapter, the Community Wastewater Management Program, established to continue the work of the New Infrastructure Program in 2012, has completed the construction of community septic systems in five communities. The Cluster Septic System was established later and targeted specific communities that were not included in the list of eligible communities at the time of the MOA; although conceptually identical to the community septic systems that have been or will soon be completed, no community has yet to avail themselves of this opportunity.
Septic Maintenance Program
The Septic Maintenance Program provides a 50 percent reimbursement of septic tank pump-out costs to all owners of WOH septic systems. Routine inspection and pump-out of septic systems every three to five years is important to ensure the proper treatment of sanitary waste. If a system is not properly maintained, sludge and scum layers can accumulate, causing short-circuiting of treatment and resulting in untreated sewage being discharged to the leach field and potentially a nearby watercourse. To be eligible for this program, the septic system needs to have been installed after November 1995 or repaired/replaced under the CWC Septic Rehabilitation and Replacement Program. The Septic Maintenance Program has funded over 2,283 pump-outs to date, and in 2018 pumped out 308 systems (NYC DEP, 2018). The target of the program is to pump out each qualified septic system every 3 to 5 years, but the actual time between pump-outs appears to be longer, based on the total number of eligible units and the number of pump-outs in recent years.
East-of-Hudson Septic System Program Descriptions
The EOH Septic Rehabilitation and Replacement Program commenced in 2009 in the Kensico Reservoir basin. The program is voluntary and administered by the NYS Environmental Facilities Corporation, which is responsible for promoting the program through annual mailings to residents and providing reimbursement for eligible construction. All residents in the Kensico basin are eligible for up to 50 percent reimbursement for repair or rehabilitation of their septic system, or to connect to an existing municipal sewage collection system.
In 2015, NYC DEP expanded the EOH residential septic program to the West Branch and Boyds Corner basins in which all residents within 200 feet of a watercourse or 500 feet of a reservoir are eligible for the program. In 2016, Cross River and Croton Falls basin residents within 200 feet of a watercourse or 500 feet of a reservoir that demonstrate a financial need were also added to the program. NYC DEP plans to further expand the program upstream to hydrologically connected basins, as prescribed by the 2017 FAD. Each basin has program prioritization based on the potential risk to water quality and proximity to Kensico Reservoir.
Figure 8-4 shows the sewered status of the Kensico watershed. NYC DEP initially focused the Septic Program on the Kensico basin because it is the terminal reservoir for the entire Cat/Del system. When the MOA was signed in 1997, no residents in the Kensico basin were connected to sewers, all 913 parcels in the Kensico basin were served by septic systems—a situation that has changed substantially over the last 20 years. The population in the Kensico Reservoir basin was 4,293 in the 2010 census, which translates to 0.51 resident/acre. Today, there are approximately 550 septic systems in the basin. The NYC DEP records indicate that 24 septic systems in the Kensico Reservoir basin have been addressed by the Septic Rehabilitation and Replacement Program since 2008.
The Kensico Reservoir basin also contains the West Lake Sewer Trunk Line, which conveys sanitary sewage outside of the Kensico basin for treatment. The sewer is owned by the Westchester County Department of Environmental Facilities. Because of the trunk sewer’s proximity to the Kensico Reservoir, NYC DEP has funded the installation of a remote sensing system for the trunk line to provide real-time detection of leaks, system breaks, overflows, and blockages. NYC DEP also conducts annual visual inspection of the entire trunk line, manholes, and vicinity to assess the condition of sewer and conducts routine partial inspections throughout the year.
Given the critical nature of the Kensico basin to the NYC water supply, a high priority of the NYC DEP should be the expansion of the sewered area of the Kensico basin to replace many of the septic systems with advanced WWTPs. The map in Figure 8-4 shows that some areas with septic systems are quite close to the Kensico Reservoir, leading to the real possibility of contamination of the water supply. To the extent that such expansion of the area served by WWTPs is infeasible, a concerted effort to replace conventional septic systems with modern aerated units should be undertaken.
Program Effectiveness to Date
For the numerous programs that address septic systems, NYC DEP staff report that they only know the number of systems installed, repaired, and pumped out and have no direct performance data to assess the extent to which the septic system programs benefit water quality. NYC DEP reports that WOH, over 5,400 residential and 19 small business septic systems have been repaired or rehabilitated since the inception of the program and over 1,900 systems have been pumped out (Meyer, 2018a). These numbers suggest that about 32 percent of the approximately 23,000 WOH septic systems have been addressed in some form since 1993. Over $100 million dollars have been invested in the septic system programs since 1993, roughly $4 million each year. This investment should support approximately 65 WOH jobs dedicated to the repair, rehabilitation, and maintenance of septic system (Bivens, 2019).
In the absence of site-specific water quality monitoring data that could shed light on the effectiveness of the septic system programs to maintain high water quality in the NYC reservoirs, one can consider the pollutant removal efficiencies of a properly designed and maintained septic system that includes a septic tank and an effective leach field. A properly designed septic tank removes 49 percent of the influent carbonaceous biochemical oxygen demand (CBOD5) and 74 percent of the TSS, and an appropriately sited, constructed, soil adsorption field will continue treatment and provide total removal efficiencies of 90–98 percent for CBOD5 and TSS and 99–99.99 percent removal of fecal coliforms (EPA, 2002). However, onsite septic systems currently constitute the third most common source of groundwater contamination; these systems have failed because of inappropriate siting or design, inadequate long-term maintenance, and saturation of the adsorption field (EPA, 1996). Because conventional septic system failure can put at risk the quality of NYC’s source water, NRC (2000) specified ATUs followed by a conventional soil adsorption system as the best available control technology for septic systems. The benefits of ATUs will be discussed further later in this chapter.
In addition to water quality benefits, the septic system programs provide significant community vitality benefits for WOH residents. In particular, the programs provide a fully or mostly subsidized way for residents to treat their sanitary waste, they provide jobs for contractors in the region to repair and replace septic systems, and they prevent the contamination of local drinking water wells by neighboring septic systems—a public health benefit that many residents may not be aware of. Despite these benefits, uptake into this voluntary program has not been widespread among WOH residents. The lack of participation might be attributed to the backlog of systems to be repaired and replaced and/or the waiting time between agreeing to participate and installation and repair.
The WOH programs are run by the CWC, which contracts with NYC DEP every five years. After the 2017 update to the FAD, there was a delay between when the FAD was signed and when a contract with CWC was finalized. Because of this delay, a backlog of 422 septic system repairs and replacements built up within the CWC’s septic program. According to Alan Rosa (CWC, personal communication, 2019), the backlog accrued because CWC could not contract with residents to replace the septic systems while it did not have a contract with NYC DEP guaranteeing that funding was available. Even once a contract in place, the structure of the contract with the Office of Management and Budget of New York City can be problematic. This is because CWC receives only a portion of its contracted funding at a time and must “voucher” the City for additional money when the funds on hand have been spent. During the early months of the fiscal year (July through October) this process is relatively timely, yet during later months (after November) there are often delays. These facts, along with the limited season during which repair and replacement can occur (primarily during late
spring and summer), can substantially limit the number of septic systems addressed in a given year. Given the likely urgency for septic repairs when needed, the CWC contract with NYC DEP should allow for a one-year extension prior to the contract end so that there is always a contract in place for these very important rehabilitations and repairs.
Best Available Technology for Septic Tanks
The NRC (2000) study of the NYC Watershed Protection Program comprehensively assessed the potential role of septic systems in degrading water quality, including a discussion of whether the appropriate technologies were prescribed for septic systems and whether the siting locations prescribed for septic systems would protect water quality. In addition, that report conducted a quantitative assessment of whether the estimated (at that time) 39,000 WOH septic systems, including the Kensico Reservoir basin, would alter the then current loading of pollutants in terms of total phosphorus, TSS, fecal coliforms, viruses, Giardia cysts, and Cryptosporidium oocysts. Both conventional septic tanks and ATUs (which were considered to be best available control technology) were evaluated. Aerobic treatment units include mechanical mixers and/or an external air compressor to aerate the septic tank, enhancing nitrification and conversion of soluble phosphorus to more recalcitrant forms that can potentially precipitate into the sludge, as well as media to support a larger population of bacteria in the tank (see Figure 8-5). As stated in NRC (2000), ATUs are superior to conventional septic tanks in the removal of the microbial contaminants, but their use would not appreciably change removal of suspended solids. Depending on how the residuals were managed, ATUs could lead to superior reduction of phosphorus loading to the soil adsorption field compared to conventional septic tanks.
Soil Adsorption Field Technologies and Siting Issues
Along with improved primary treatment of influent in the septic tank, using the best available control technology should also include the appropriate soil adsorption system, which is dictated by the physical conditions of the site where the leach field is located. Much of the WOH region is characterized by shallow soils underlain by some sort of restricting layer that impedes vertical drainage (Day, 2004). Soil type, percolation rate, depth to impermeable layer, and the average water table height are all factors that must be considered when determining the suitability of a site for a soil adsorption system. Yet, design criteria for conventional leach fields have generally been developed for landscapes with deep soils overlying aquifers (Collick et al., 2006).
General design requirements for conventional soil adsorption systems specify that there should be at least 1 meter between the septic effluent distribution pipes and seasonal high groundwater depth (Otis, 1980a,b). NYS DOH (1996) has two requirements relating to leach field suitability: (1) there should be a minimum of 1.2 meters of suitable soil above bedrock to ensure leach-field performance, and (2) the seasonal high groundwater table may be no closer than 0.6 meters below the lowest part of the trench to allow treatment of the effluent by the soil. Yet, Day (2004) found that 96 percent of the area in the Cannonsville Basin had soils that did not meet these criteria. Shallow soils can result in both treatment failure and hydraulic failure of a septic system. Treatment failure occurs when contaminants are not fully removed from the wastewater because of an insufficient depth of the aerated zone. Hydraulic failure occurs when the water table inundates the disposal pipes or reaches the ground surface, such that overland flow can transport pollutants offsite without further treatment (Robertson, 1995; Robertson and Harman, 1999; Wilhelm et al., 1994). Both treatment and hydraulic failure can result in offsite transport of nutrients and pathogens.
Alternatives to conventional soil adsorption systems include shallow adsorption trenches, mounds, and drip systems (Figure 8-6), all three of which may be appropriate for areas with shallow soils and high groundwater (EPA, 2002). While the biological, physical, and chemical treatment of effluent in alternative and conventional soil adsorption systems is largely the same, these alternative soil adsorption systems adjust the configuration of the leach field to ensure complete treatment of the wastewater.
A shallow adsorption trench system is appropriate for soils with adequate infiltration characteristics but inadequate soil depth to support a standard soil adsorption system. Shallow adsorption trench systems generally locate the drain pipe following contours at or within 15 cm of the soil surface, dependent on soil and site characteristics, and cover the pipe with some sort of exclusionary barrier (e.g., geotextile or infiltrator chamber, Figure 8-6) to prevent roots and soil migration into the drain pipe. The leach filed is then covered with a minimum of 20 cm of topsoil (EPA, 1980).
Similar to shallow adsorption trench systems, a drip distribution system is generally most appropriate in soils with adequate drainage characteristics but inadequate soil depth and in areas with steep slopes or heavily forested areas where it is difficult to install trenches, mounds or at-grade systems. A drip system is constructed of ‘drip’ laterals in the top 3 to 15 cm of soil and a dose tank after the primary septic tank to accommodate the timed dose delivery of wastewater to the drip absorption area. Additional components for the mound and drip systems, including an equalization tank, a pump, and electrical power, require additional expense and increased maintenance. Drip systems also require a greater leach field area over which to dose flow because drip tubes allow only a small amount of effluent to be applied to the soil at a time.
Mound systems are generally the most expensive to construct and are often used where there are both inadequate soil infiltration characteristics and inadequate soil depth for a conventional soil adsorption system. A mound system creates a “mound” of sand, soil, and gravel to ensure that proper infiltration characteristics are met and the drain pipe is above the restricting layer or the seasonal high water table. Effluent from a septic tank must be pumped to the mound in appropriate quantities for treatment through the system and into native soil.
Consequences of Septic System Failure
Many studies have documented elevated pollutant levels downgradient of even seemingly well-functioning septic systems. Aley et al. (2007) found nitrate concentrations in plumes downgradient of a septic system that well exceeded drinking water standards (10 mg/L NO3-N), and as high as 40 mg/L at distances upward of 35 meters from a septic system. Gold et al. (1990) measured mean annual concentrations of 68 mg NO3-N/L with an associated mass loss of 48 kg N/ha from septic fields on well-drained silt loam or sandy loam soils. Phosphate plume concentrations in groundwater have also exceeded drinking water standards (2 mg/L) at documented distances greater than 25 meters from septic disposal fields (Wilhelm et al., 1994). Twenty years ago, the NYC DEP conducted a Septic Siting Study that is summarized in Box 8-3. The findings of the Septic Siting Study included documentation of surrogate pathogens observed beyond the 100-ft setback required for the septic system drainage field by the Watershed Rules and Regulations. Given the proximity of residences in the WOH region to waterbodies (more than 11,000 parcels are within 50 ft of a watercourse, Meyer 2018a), the potential of a conventional septic system to contribute nutrients and pathogens to the NYC water supply, if it fails, is a significant risk that should be resolved by the septic system programs. This situation is particularly
important for septic systems in the Kensico basin because the opportunity for further degradation in the natural environment is far less than in the WOH reservoirs.
Recommended Course of Action
The Septic System Program has suffered from poor program participation. From 1997 to 2018, there were only 2,283 systems pumped out and approximately 5,500 residential systems repaired or replaced (NYC DEP, 2018). This suggest that systems are being pumped out roughly once every ten years. Furthermore, if systems are repaired or replaced at a rate of 5,500 every 20 years, the lifespan of the systems, in general, is expected to exceed 80 years. Research suggests that typical septic systems have an average lifespan of 15-40 years (Clayton, 1974; Dix and Hoxie, 2001; Jensen and Seigrist, 1990; Saxton and Zeneski, 1979). These statistics suggest that the Septic System Program is falling well short of its potential to protect water quality in the reservoirs from failing systems.
Best Available Control Technology
NRC (2000) recommended in very strong terms that the septic system technology used in the NYC watersheds was not adequate and did not represent best available control technology. Since the NRC (2000) recommendation, additional research has further corroborated the effectiveness of advanced septic systems (although none of the following studies were conducted in the NYC watershed system). For example, Garcia et al. (2013) compared the pollutant removal efficiencies of a conventional secondary WWTP, an ATU, and a conventional septic tank, all three of which treated the same municipal wastewater influent. (Note that the effluent from the ATU and the conventional septic tank were not dosed to a soil adsorption system, thereby ignoring the potential for additional treatment in a properly functioning leach field.) TSS, CBOD and NH3 removal was comparable for the WWTP and ATUs, and the effluent quality for both of these treatment systems was very good, in the low parts per million concentrations. In contrast, the effluent quality from the septic tank was very high in TSS and CBOD and exceeded the criteria established by the Texas Commission on Environmental Quality of 65 mg/L and 60 mg/L, respectively.
Abbassi et al. (2018) tested two ATU configurations and reported removal efficiencies measured at the effluent tank discharge point (i.e., before being dosed to the leach field); both configurations had four equal-sized chambers operated in series, the first three chambers being anaerobic and the fourth aerobic. One of the systems was configured with attached growth media and one with suspended growth. The attached growth media was corrugated plastic media with specific area of 100 m2/m3; the media was filled to two-thirds of the chamber capacity, but was not included in the first chamber. They documented removal of 95 to 98 percent BOD and 92 to 98 percent TSS at hydraulic retention times ranging from 2.6 to 4.4 days. Significant total nitrogen removal of 59 percent was observed in the attached growth system at 2.6 days hydraulic residence time, while results varied between 26 to 33 percent removal at higher loading rates and between 0 and 29 percent in the suspended growth configuration. Both configurations removed an average of 24 to 29 percent total phosphorus. Effluent quality met secondary wastewater quality criteria for all parameters except for E. coli before dosing to the soil adsorption field.
Bradley et al. (2002) reported challenges with employing standard septic system design in regions with characteristics similar to the WOH region: a seasonal high water table and shallow soils short-circuiting treatment. Bradley et al. (2002) concluded that shallow adsorption trench system with a geotextile filter and pressure-dosed dispersal provides effective wastewater treatment: BOD and TSS less than 5 mg/L, and a significant amount of nitrogen removal. They also note that shallow adsorption trench systems are more sustainable than conventional septic systems due to the minimal cost differential between the capital and operating costs and the dramatically improved treatment efficiency. They further noted that the electrical energy consumed by the system was minimal and suggested that maintenance of the system is on the order of $100 annually.
The studies outlined above support the recommendation by NRC (2000) that an ATU provides superior treatment compared to a conventional septic tank and provides CBOD, TSS and NH3 removal consistent with secondary treatment in case the leach field fails. In addition, given the improvements in soil adsorption field technology, and the site characteristics in both the WOH and EOH watersheds, alternative soil adsorption fields should be incorporated into any new or replacement designs.
Given the proximity of many of the septic systems to watercourses in the NYC watersheds and the consequences of system failure, there is a strong case to require best available control technology for both the septic tank and soil adsorption field to ensure proper treatment of wastewater and protection of NYC source water. ATUs are more effective than conventional septic tanks in that they degrade contaminants more completely. Further, combining an ATU with an appropriate soil adsorption system will also more effectively remove nitrogen and phosphorus. Throughout most of the WOH region, the soil characteristics, groundwater, and/or shallow bedrock should preclude the effectiveness of a conventional drain field (Day, 2004).
Cost and Maintenance Considerations
ATUs require yearly maintenance (normally mandated and overseen by state or local health departments), produce more sludge than conventional septic tanks, and can be considered unsightly. Alternative leach field designs are more expensive and often more time-consuming to install than conventional leach fields, due to the need for pumping from the tank to the leach field (for mound and drip systems), additional substrate such as topsoil, sand, and gravel (for mound and shallow adsorption trenches), and more advanced design considerations. Yet, once the complexity of an ATU is added to a septic system, the additional effort to construct a mound or drip system is not as onerous given that the system will already require the addition of an electrical power feed to the system.
Installing ATUs and alternative soil adsorption systems would require that local construction companies be retrained to become familiar with the installation, operation, and maintenance of such units. Ideally, maintenance of these systems would fall under the umbrella of the Septic Maintenance Program. Although such advanced systems come with more frequent maintenance, this could actually help ensure better program participation and provide confirmation that the systems are functioning correctly. An improved Septic System Program that includes advanced technologies will increase community vitality through the provision of jobs in the watershed region needed to support this program.
Assuming complete uptake by watershed residents, the funding for the Septic System Program is currently inadequate to service the number of known septic systems in the region and their anticipated life span. If there are 23,000 septic systems in the WOH watershed and they have a lifetime of approximately 15 to 40 years, the Septic System Program should be replacing about 500 to 1,500 systems a year. Assuming an average cost of $20,000 to replace a system, the program would need to maintain a funding level of $10 million to 30 million a year into the future. This funding level is an underestimate, considering that costs to integrate ATUs and alternative soil adsorption systems into the Septic System Program would further increase costs, perhaps by 30-50 percent in capital expenses and $200-300 a year in power, maintenance, and inspection costs per system.2
The attention given to improving centralized wastewater treatment in the NYC watershed has made substantial impacts in terms of reducing pollutant concentrations in the water supply reservoirs (see Chapter 4). However, the Septic System Program has not experienced the same success, despite the fact that the vast majority of watershed residents both east and west of the Hudson River have septic systems. The following conclusions and recommendations are aimed at helping the Watershed Protection Program close the loop with respect to treatment of human wastes.
Although the Wastewater Treatment Plant Program is expensive, it is effective and provides state-of-the-art wastewater treatment to the residents and industries served. The WWTP program has been very effective in removing suspended sediment and pathogens and has been tremendously effective in reducing phosphorus loading in the respective basins. If the incremental cost to operate the WWTPs remains roughly $19 million annually, it seems like an effective, sustainable program. The capital cost for rehabilitation of these WWTPs in 20 years should be quantified and budgeted now. Given that the program will continue to provide upgrades to WWTPs into the future, NYC DEP may want to investigate management and/or technology improvements to make sure that best available control technology is used and to reduce operations and maintenance costs (e.g., if membranes get less expensive).
Protecting the Kensico Reservoir from wastewater treatment plant effluent and failed septic systems should be a top priority for the Watershed Protection Program. Given the proximity of septic systems to the Kensico Reservoir and the findings of the 1999 Septic Siting Study, the NYC DEP should focus on removing conventional septic systems from this watershed and replacing them with either best available
2 The additional cost of installing an ATU is estimated to increase the capital cost up to 20 percent, depending on the distance to a source of power for the aerated mixing pump, and alternative leach fields can add another 10 to 30 percent to total costs (G. Rohloff, Managing Civil Engineer, Metropolitan Water Reclamation District of Greater Chicago, personal communication, 2020).
control technology or centralized wastewater treatment. Only 20 septic systems in the Kensico basin were rehabilitated/repaired by the date of the 2016 Watershed Protection Program Summary and Assessment (and only one in 2018), indicating very poor program uptake among the watershed’s residents.
The Septic System Program should be better funded to accelerate its implementation, eliminate the backlog of septic system repairs and replacements, and train contractors on the installation and maintenance of best available control technologies. The contracts between NYC DEP and the CWC should allow time extensions so there is always a contract in place for critical septic system repairs and replacements. The Septic System Program provides significant community vitality benefits that are currently unrealized because implementation has been relatively slow and enrollment by residents has been limited.
Once again, the New York City Department of Environmental Protection is encouraged to require the use of aerobic treatment units (ATUs) for new and replacement septic tanks. Further, given the topography and soil characteristics of the Catskill region, alternative soil adsorption systems (shallow adsorption, mound, or drip systems) should be required to ensure more complete wastewater treatment. The FAD reports give no indication that ATUs or advanced soil adsorption systems have been required for residents in either the WOH or EOH watersheds. These units could be introduced in a phased manner, prioritizing the Cannonsville and Kensico watersheds. The effectiveness of ATUs and advanced soil adsorption systems in the watershed could be investigated by conducting a pilot study, which might also serve to increase familiarity with these systems among contractors. Use of ATUs and alternative soil adsorption systems will require a workforce to install and maintain these systems.
Abbassi, B. E., R. Abuharb, B. Ammary, N. Almanaseer, and C. Kinsley. 2018. Modified septic tank: Innovative onsite wastewater treatment system. Water (10):578.
Aley W., M. Mechling, G. Pastrana, and E. Fuller. 2007. Multiple nitrogen loading assessments from onsite waste treatment and disposal systems within the Wekiva River Basin. Tallahassee, FL: FL Department of Health, Division of Environmental Health, Bureau of Onsite Sewage Programs.
Bivens, J. 2019. Updated employment multipliers for the U.S. economy. Washington, DC: Economic Policy Institute. January. https://www.epi.org/publication/updated-employment-multipliers-for-the-u-s-economy/.
Bradley, B. R, G. T. Daigger, R. Rubin, and G. Tchobanoglous. 2002. Evaluation of onsite wastewater treatment technologies using sustainable development criteria. Clean Technologies and Environmental Policy 4:87–99.
Carpenter, S. R., N. F. Caraco, D. L. Correll, R. W. Howarth, A. N. Sharpley, and V. H. Smith. 1998. Nonpoint pollution of surface waters with phosphorus and nitrogen. Ecological Applications 8:559-568.
Clayton, K. W. 1974. An analysis of septic tank survival data from 1952 to 1972 in Fairfax County, Virginia. Journal of Environmental Health 36(6):562-567.
Collick, A. S., Z. M. Easton, F. A. Montalto, B., Gao, Y. J. Kim, L. Day, and T. S. Steenhuis. 2006. Hydrological evaluation of septic disposal field performance in sloping terrains. Journal of Environmental Engineering 132(10):1289‐1297.
Davis, M. L. 2010. Water and Wastewater Engineering: Design Principles and Practice. New York: McGraw Hill.
Day, L. D. 2004. Septic systems as potential pollution sources in the Cannonsville Reservoir Watershed, New York. Journal of Environmental Quality 33:1989-1999.
Dix, S., and D. Hoxie. 2001. Analysis of Septic System Longevity in Maine. On-Site Wastewater Treatment Proceedings. K. Manci (ed.). Ninth National Symposium on Individual and Small Community Sewage Systems, Fort Worth, TX. St. Joseph, MI: American Society of Agricultural Engineers.
EPA (U.S. Environmental Protection Agency). 1980. Design Manual, Onsite Wastewater Treatment and Disposal Systems. EPA 625/1-80-012. Washington, DC: EPA. https://www.epa.gov/sites/production/files/2015-06/documents/septic_1980_osdm_all.pdf.
EPA. 1996. National Water Quality Inventory Report to Congress (305b Report). EPA 841-R97-008. Washington, DC: EPA Office of Water.
EPA. 2002. Onsite Wastewater Treatment System Manual. EPA 625-R-00-008. Washington, DC: EPA Office of Water. https://www.epa.gov/sites/production/files/2015-06/documents/2004_07_07_septics_septic_2002_osdm_all.pdf.
EPA. 2004. Primer for Municipal Wastewater Treatment Systems. EPA 832-R-04-001. Washington, DC: EPA Office of Water. https://www3.epa.gov/npdes/pubs/primer.pdf.
Garcia, S. N., R. L. Clubbs, J. K. Stanley, B. Scheffe, J. C. Yelderman Jr., and B. W. Brooks. 2013. Comparative analysis of effluent water quality from a municipal treatment plant and two on-site wastewater treatment systems. Chemosphere (92):38–44.
Gold, A. J., W. R. DeRagon, W. M. Sullivan, and J. L. Lemunyon. 1990. Nitrate-nitrogen losses to groundwater from rural and suburban and uses. Journal of Soil and Water Conservation 45(2):305-310.
Jensen, P., and R. Seigrist. 1990. Technology assessment of wastewater treatment by soil infiltration systems. Water Science and Technology 22(3/4):83-92.
Meyer, M. 2018a. Wastewater Programs WOH. Presentation at the 2nd meeting of the NASEM Committee to Review the NYC DEP Watershed Protection Program. Rhinebeck, NY. October 24-26.
Meyer, M. 2018b. East of Hudson Programs. Presentation at the 2nd meeting of the NASEM Committee to Review the NYC DEP Watershed Protection Program. Rhinebeck, NY. October 24-26.
NRC (National Research Council). 2000. Watershed Management for Potable Water Supply: Assessing the New York City Strategy. Washington, DC: The National Academies Press.
NYC DEP (New York City Department of Environmental Protection). 1993. Final Generic Environmental Impact Statement for the Proposed Watershed Regulations for the Protection from Contamination, Degradation, and Pollution of the New York City Water Supply and its Sources. November. Corona, NY: NYC DEP.
NYC DEP. 1998. Protocol for Testing Equivalency of Continuous Backwash, Upflow Dual Sand Filter with Microfiltration. https://archive.epa.gov/region02/water/nycshed/web/pdf/protocol.pdf.
NYC DEP. 1999. Final Report for the Septic Siting Study. December 31.
NYC DEP. 2016. Watershed Protection Program Summary and Assessment. March.
NYC DEP. 2018. Filtration Avoidance Annual Report.
NYC DEP. 2019. Watershed Protection Program summaries. January.
NYS DOH (New York State Department of Health). 1996. Individual residential wastewater treatment systems design handbook. Albany, NY: NYS DOH.
Otis, R. J. 1980a. Onsite wastewater treatment: Septic tanks. Morgantown, WV: National Small Flows Clearinghouse.
Otis, R. J. 1980b. Subsurface soil absorption of wastewater: Trenches and beds. Morgantown, WV: National Small Flows Clearinghouse.
Robertson, W. D. 1995. Development of steady-state phosphate concentrations in septic systems. Journal of Contaminant Hydrology 19:289–305.
Robertson, W. D., and J. Harman. 1999. Phosphate plume persistence at two decommissioned septic system sites. Ground Water 37(2):228–236.
Saxton, G. B., and J. M. Zeneski, J. M. 1979. Septic systems in Connecticut. Proceedings of the American Society of Civil Engineers 105:503.
Schindler, D. W. 1974. Eutrophication and recovery in experimental lakes: Implications for lake management. Science 184:897–899.
Tchobanoglous, G., and E. D. Schroeder. 1987. Water Quality: Characteristics, Modeling and Modification. Reading, MA: Addison-Wesley.
Warne, D. 2018. New York City’s Source Water Protection Program. Presentation at the 1st meeting of the NASEM Committee to Review the NYC DEP Watershed Protection Program. Saugerties, NY. September 26-28.
Wilhelm, S. R., S. L. Schiff, and W. D. Robertson. 1994. Chemical fate and transport in a domestic septic system: Unsaturated and saturated zone geochemistry. Environmental Toxicology and Chemistry 13(2):193-203.