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Watershed Management for Potable Water Supply: Assessing the New York City Strategy 12 Overarching Issues NEW DIRECTION FOR NEW YORK CITY'S WATERSHED MANAGEMENT PROGRAM The principal goal of the Memorandum of Agreement (MOA) is to protect public health in the City of New York by providing the City with safe, potable water while at the same time protecting the rights and needs of the residents of the watershed. A necessary component of any plan to meet this goal involves meeting the provisions set forth in the Safe Drinking Water Act (SDWA) and its amendments. For unfiltered surface water supplies, this legislation and the rules emanating from it involve (1) providing sufficient inactivation to control Giardia, (2) maintaining the turbidity and fecal coliform concentrations of the surface water supplies below specified levels, (3) controlling the concentrations of disinfection byproducts (DBPs) in the distribution system below specified levels, (4) maintaining a detectable residual disinfectant concentration ''or its equivalent" throughout the distribution system, (5) limiting the total coliform concentration in the distribution system, and (6) controlling corrosion that can lead to high lead and copper concentrations at the consumer's tap. Nutrients such as phosphorus are addressed in the Clean Water Act and are not a direct public health concern in drinking water. In fact, phosphate is often added to potable water supplies to retard corrosion in distribution networks and household plumbing, thereby reducing lead and copper concentrations. Nutrients can, however, have deleterious effects on drinking water when they stimulate algal and bacterial growth in reservoirs. Increased productivity can lead to the release of organic carbon compounds in the water and, in turn, increase the production of undesirable DBPs when the water is disinfected for potable use.
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Watershed Management for Potable Water Supply: Assessing the New York City Strategy Future Environmental Protection Agency (EPA) rules are expected to lower the allowable concentrations of several DBPs in drinking water distribution systems. Requirements for the inactivation and/or removal of Cryptosporidium oocysts may also be introduced. Pollutant Priorities In the committee's opinion, in order to meet the goals enumerated above, four primary contaminants require effective control in the management of the City's watershed. Prioritized by the committee, they are (1) microbial pathogens, (2) natural organic carbon compounds, (3) phosphorus, and (4) turbidity. Toxic compounds such as pesticides, heavy metals, and synthetic organic compounds are also potential pollutants that should not be overlooked. However, their use in the Catskill/Delaware watershed is limited to specific areas. Recent monitoring of toxic compounds in the water supply watersheds has not detected notable concentrations. Current and potential land and resource uses in the region are unlikely to involve industries that have substantial inventories of metals and solvents. Agricultural trends, such as the move from dairy operations to truck crops and organic practices, suggest reductions in pesticide use. For these reasons, toxic compounds are not considered further in this chapter. Rather, specific recommendations for monitoring these compounds are given in Chapter 6. Microbial pathogens should be the primary focus of the watershed management program for numerous reasons. The MOA was created to comply with the Surface Water Treatment Rule (SWTR), which specifically targets microorganisms for control. These organisms, which can produce mild to life threatening infections, originate from a diverse array of sources. Several are difficult to inactivate by conventional disinfection processes, and some can survive for long periods in aquatic environments. Finally, their transport and fate are difficult to assess, and the effectiveness of common best management practices (BMPs) in reducing their concentrations in stormwater is generally unknown. Natural organic carbon compounds—measured as dissolved organic carbon (DOC)—are placed second because they are a primary reactant in the formation of most DBPs that are, or are likely to be, regulated. Also, these compounds can serve as carbon and energy sources for microbial growth in the City's distribution system. Their origins in the watershed are diverse and in many cases difficult to manage. Organic carbon will be an important factor in the design and operation of any additional treatment facilities the City may consider. Third, attention is placed on phosphorus, which has several major impacts on potable water supplies. It can drive algal productivity in surface waters, which is the case in most of the City's water supply reservoirs. Algae, in turn, can generate several other water quality problems for a water supply. Because algae are particles, they scatter light and contribute to turbidity. When algae settle to the bottom waters of a reservoir, their degradation by heterotrophic bacteria can
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Watershed Management for Potable Water Supply: Assessing the New York City Strategy deplete oxygen in these waters and accelerate the release of undesirable contaminants such as iron and manganese from bottom sediments into the water column. The presence of these contaminants can necessitate treatment of the water prior to its potable use. Phytoplankton can release organic taste- and odor-causing substances to surface waters. Algae serve as substrates for bacteria and other organisms that also release organic carbon compounds. This autochthonous DOC is a precursor for DBP formation. The fourth contaminant considered is turbidity. Turbidity is an indirect and imperfect but easily assessed indicator of the possible presence of other pollutants. Turbidity arising from particles, including algal cells and debris, can protect pathogens from inactivation during disinfection. Particle-reactive pollutants are often associated with turbidity and are transported with sediments in the watershed. Particles can also accumulate in reservoir sediments and have long-term effects. Although the sources of turbidity in a watershed are diverse and intermittent, controls of many of these inputs can be effective. Current Approaches by New York City Pathogens At present New York City provides disinfection with free chlorine to meet EPA's "CT" requirement for the 3-log inactivation of Giardia cysts. It is likely that EPA will, in the next few years, require treatment to inactivate Cryptosporidium oocysts (EPA, 1998; NYC DEP, 1998a). These organisms are resistant to inactivation by free chlorine. Therefore, substantial changes in the City's disinfection strategy for control of microbial pathogens can be anticipated. Managers of unfiltered supplies should be at or near the forefront of information on Cryptosporidium, other emerging microbial pathogens, and their regulation. A comprehensive framework for controlling pathogens in the watershed should have three primary goals: (1) identifying pathogen sources in the watershed and determining quantitative source terms, (2) determining the effects of management practices on current pathogen concentrations, and (3) directing resources toward the most polluting sources. Reaching these three goals is paramount to demonstrating the role of watershed management in reducing the risk of microbial pathogens to public health. Once its role is established, watershed management can be compared to filtration and other treatment processes to better evaluate its costs and benefits. The current pathogen monitoring efforts represent a first step toward assessing quantitatively sources of pathogens (goal 1) and the degree to which watershed management improvements can reduce pathogen loading to the reservoirs (goal 2). As discussed in Chapter 6, accomplishing the first goal requires gathering data on the occurrence of pathogenic microorganisms in the watershed and calculating source terms, such as (oo)cyst concentration per area per time, for
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Watershed Management for Potable Water Supply: Assessing the New York City Strategy each catchment. Although some data have been collected as part of the Pathogen Studies and other efforts (Auer et al., 1998a), they have not been systematically analyzed to the extent necessary to evaluate current impacts or future options. For example, the relative contributions of different land uses to overall pathogen loadings have not been determined as has been done for phosphorus, even though some of the necessary concentration and land use data are available. Development of quantitative source terms has not been undertaken. While wastewater effluents and reservoirs have been subject to regular monitoring for pathogens, there has not been the same regular and systematic monitoring of agricultural and other nonpoint sources (e.g., stormwater, septic systems) and BMPs used to control pathogen concentrations. Available information suggests that most urban stormwater BMPs are only moderately effective in removing bacteria, and no information is available on removal of protozoa. Chapter 9 stresses the urgent need for performance monitoring of agricultural BMPs, suites of BMPs, and Whole Farm Plans to determine their pathogen-removal capabilities. Finally, existing pathogen monitoring data of nonpoint sources have not been used in a coordinated way with watershed models. Integration of the pathogen monitoring data with watershed models must be accomplished and supported by appropriate validation. Once developed, these models can be coupled with field data and used as an analytical tool to assess the effectiveness of different watershed management options on pathogen concentrations in reservoirs. To implement this approach, which would place pathogens in a framework commensurate to other contaminants (e.g., phosphorus), additional effort should be made to obtain fundamental information on processes influencing pathogen transport and fate in the watershed. These additional processes include die-off, separation from manure, contributions from subsurface waste-disposal systems, and removal by agricultural and urban stormwater BMPs, among others. Given its prioritization of pollutants, the committee maintains that the level of resources and effort afforded to pathogens be the same as or greater than that currently afforded to phosphorus. The necessary resources should be devoted to expedite development and use of a pathogen management framework that integrates information on sources, life-cycle processes, and BMP removal rates with models of transport and fate. Natural Organic Carbon Compounds Natural organic carbon compounds are important because of their role in DBP formation. High levels of DOC in water supplies can reduce flexibility in treating water for pathogens by preventing water suppliers from aggressively disinfecting their water with chlorine. In order to manage DOC effectively, the City must determine the origins of DOC in the water supply and evaluate possible differences among those sources on the formation of DBPs and on other processes.
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Watershed Management for Potable Water Supply: Assessing the New York City Strategy Autochthonous sources of DOC are amenable to control by limiting the supply of inorganic nutrients to the reservoirs, and New York City is addressing this problem well by controlling phosphorus loading. Allochthonous sources, however, are more difficult to assess and are also very difficult to control. Much of the allochthonous carbon derived from areas high in the watershed is from natural plant tissue (e.g., forests), with less from agricultural, urban, and deep groundwater sources. Closer to New York City, anthropogenic sources (such as agriculture and urban areas) become more important, but because of the high percentage of forest cover in the Catskill/Delaware watershed, the majority of allochthonous DOC likely is derived from widespread natural sources. Because removal processes for allochthonous DOC are almost all biological, time is the most important factor for reducing concentrations of these recalcitrant compounds. Traditional urban stormwater and agricultural BMPs are not expected to remove DOC to any significant degree. Wetlands have some capacity for controlling DOC, but the percent removal is generally low. Buffer zones can accomplish some removal of allochthonous DOC if they retard its transport, particularly during periods of high DOC loading associated with rain or snowmelt events. Research efforts have revealed that both allochthonous and autochthonous sources of DOC can contribute to the formation of DBPs in the reservoirs. In the Cannonsville Reservoir, DOC from allochthonous sources was very effective in forming trihalomethane (THM) precursor compounds (Stepczuk et al., 1998a). Similar analyses were conducted within the reservoir open water, and again the DOC was found to be most effective in functioning as THM precursor compounds. In the open water, however, it is not possible to distinguish between allochthonous DOC and the autochthonous DOC produced by phytoplankton decomposition (Stepczuk et al., 1998b). Because inflows purportedly decreased and phytoplankton production increased during the summer, it was assumed that much of the THM precursor compounds was being formed by the algae. That may not be the case, however, because allochthonous DOC decomposes much more slowly in the reservoir than does the DOC from phytoplankton. Therefore, control of DOC (and consequently DBP formation) will not be accomplished by focusing solely on autochthonous sources and reducing nutrient inputs to the reservoirs. For the past few years, the concentrations of total trihalomethanes (TTHMs) in the City's water have been decreasing; they are well below past and present standards (0.10 and 0.08 mg/L, respectively). However, there is some evidence that the total concentration of five haloacetic acids (HAA5) in the water is close to the new limit of 0.060 mg/L. Under present conditions, the drinking water would exceed the forthcoming Stage 2 maximum contaminant level (MCL) for HAA5 (0.030 mg/L is the placeholder value). In actively managing DOC it is important that the City consider the causes of these trends in DBP levels and also address other DBPs that may be regulated in the future.
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Watershed Management for Potable Water Supply: Assessing the New York City Strategy Phosphorus Of the priority pollutants, phosphorus has received the most attention. This may be because it is an important contaminant, because the professional staff have extensive expertise in limnology and eutrophication, and because it may be the least difficult and costly to manage of the four types of priority contaminants. As noted earlier, phosphorus can be present in water in either soluble or particulate forms, with soluble phosphorus being more bioavailable for eutrophication. Because it has been shown that over 95 percent of the phosphorus taken up by phytoplankton in the Cannonsville Reservoir is soluble (Auer et al., 1998b), management efforts are primarily targeted at this form. Sources of soluble phosphorus in the watersheds are many and diverse. Soluble phosphorus is the primary type of phosphorus emanating from point source inputs such as wastewater treatment plants (WWTPs) and from septic systems with ineffective drainage fields. WWTP sources of soluble phosphorus are adequately addressed by the MOA through its mandated upgrade of all sewage treatment plants. Indications are that all 41 municipal WWTPs in the Catskill/Delaware watershed will receive these upgrades in the next two or three years. The control of soluble phosphorus from on-site sewage treatment and disposal systems (OSTDS) is much less certain. Because there is no current requirement for the use of aerobic treatment units with appropriate sludge disposal (as recommended in Chapter 11), reducing phosphorus loadings from OSTDS is unlikely. Recent research suggests, however, that point sources are not the primary source of soluble phosphorus in the watershed. Predictions from the Generalized Watershed Loading Function (GWLF) implicate subsurface flow (affected by nonpoint sources) as the greatest contributor of soluble phosphorus (NYC DEP, 1998b). Monitoring data have shown that nonpoint sources contribute significant amounts of soluble phosphorus, comprising about 61 percent of soluble reactive phosphorus between 1992 and 1996 in the Cannonsville watershed (Longabucco and Rafferty, 1998). Urban stormwater is typically 40 percent to 50 percent soluble reactive phosphorus (Schueler, 1995), and similar percentages have been observed for agricultural runoff (Longabucco and Rafferty, 1998). Controlling these sources of soluble phosphorus should be a goal of stormwater and agricultural BMPs. However, the current paucity of performance monitoring of these technologies makes it difficult to know how well these sources are being mitigated. The situation is more even complex when the contribution of particulate phosphorus to the pool of soluble phosphorus is considered. As much as 50 percent of particulate phosphorus from the Cannonsville watershed may be bioavailable (Auer et al., 1998b). In addition, biogeochemical cycling of phosphorus in reservoir sediments adds to the available pool of dissolved phosphorus. During wet years (such as 1996), extremely high loadings of particulate phosphorus—up to ten times greater than loadings of soluble phosphorus—are
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Watershed Management for Potable Water Supply: Assessing the New York City Strategy possible. Hence, particulate phosphorus cannot be ignored when assessing reservoir health and the potential for eutrophication. About 90 percent of particulate phosphorus in the Cannonsville watershed comes from nonpoint sources: urban stormwater, agriculture, and forests (Longabucco and Rafferty, 1998). Nonpoint sources are likely to also account for the majority of particulate phosphorus in the other Catskill/Delaware watersheds. Predictions from the GWLF that account for the area and type of land use suggest that much of this particulate phosphorus emanates mainly from forest land and urban areas in all basins except Cannonsville, where agriculture is the primary source (NYC DEP, 1998b). Thus, nonpoint source BMPs must be capable of reducing both particulate and soluble phosphorus loadings, a formidable task. In summary, available data and model predictions suggest nonpoint sources should be the focus of future management efforts. Although soluble phosphorus may seem, quite logically, to be the priority pollutant, for the reasons stated above, both soluble and particulate phosphorus must be controlled. Improvements in OSTDS design, installation of urban stormwater and agricultural BMPs, and performance monitoring of these technologies are fundamental to meeting these goals. Turbidity Phytoplankton growth is a source of turbidity in the water supply reservoirs that is being adequately controlled by the City's efforts to limit phosphorus loading from point and nonpoint inputs. However, most turbidity problems in the Catskill/Delaware watersheds are caused by inorganic sediment from soil and channel erosion mobilized during rainfall, snowmelt, and stormflow events. In undisturbed forests, with the soil surface well protected by leaf litter, most sediment originates within stream channels. As noted earlier, some land and resource uses exceed the inherent resistance and resilience of sites and increase the quantity and rate of soil and channel erosion. It is not clear what coordinated management efforts have been made to reduce erosion from distributed sources, especially in the Schoharie and Ashokan watersheds where the problem is most acute. In addition, water transfers from the Schoharie to the Ashokan may inadvertently promote channel instability and erosion in the Esopus Creek when releases are made to augment streamflow for recreational use. The operational response to high concentrations of turbidity is to add alum to the Catskill aqueduct just upstream of the Kensico Reservoir. As an alternative, or in addition to current efforts, the committee suggests the following approach to controlling sources of turbidity, some elements of which may already be under way. First, detailed land cover and land use data should be collected for watersheds with unacceptably high turbidities (e.g., Stony Clove, tributary to the
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Watershed Management for Potable Water Supply: Assessing the New York City Strategy Esopus Creek at Phoenicia) using high-resolution digital orthophotography. Using land cover/land use, soils, and digital elevation data, a Geographic Information System (GIS)-based model of soil erosion and sediment delivery should be developed. Polygons or grid cells in the resulting soil erosion and sediment delivery layers could then be ranked from the highest to lowest potential contributor of sediment. (Because active management is prohibited in some areas of the Catskill Forest Preserve, the Preserve can be excluded from the ranking procedure. However, erosion control and stormwater management measures—in collaboration with the New York State Department of Environmental Conservation (NYS DEC), the Appalachian Mountain Club, and others—may be needed on heavily used hiking trails and parking areas for recreational access.) Spatially distributed watershed modeling should be accompanied by the development of a simple, reproducible field assessment technique for soil erosion, channel stability, and sediment transport. Sites identified with the GIS should be visited in priority order to assess field conditions. Preliminary recommendations for erosion, sediment, and stormwater control should be formulated in the field. They could include such practices as (1) water bars on unpaved roads to divert overland flow into adjacent forest before it reaches streams, (2) bioengineering techniques for stream channel and road fill stabilization, (3) crushed stone applied to steep road sections, and (4) revegetation of unstable areas, among others. To promote successful implementation, the New York City Department of Environmental Protection (NYC DEP) should seek the cooperation of the Catskill Watershed Corporation, the Watershed Agricultural Program, the Watershed Forestry Program, or town officials in contacting landowners to gain permission to undertake erosion and sediment control. Sites selected either at random or on the basis of site characteristics and BMP types should be monitored before, during, and after mitigation activities to validate and refine modeling and assessment procedures, minimize construction impacts, and assess "as-built" performance, respectively. This program of coordinated, incremental, small-scale actions should have positive and cumulative effects on turbidity in the Catskill/Delaware system. Conclusions and Recommendations for Prioritization Within the Watershed Management Program The primary focus of the City's efforts in protecting the health of its consumers should be on microbial pathogens in the water supply and on developing means to control them. The strategy for controlling pathogens should have three goals: (1) identifying pathogen sources in the watershed and determining quantitative source terms, (2) determining the effects of management practices on current pathogen concentrations, and (3) directing resources toward the most polluting sources. To accomplish these tasks, fundamental information on pathogen sources, transport, and fate in the watershed must be
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Watershed Management for Potable Water Supply: Assessing the New York City Strategy obtained, and nonpoint source BMPs must be quantitatively assessed for their ability to control pathogens. This is especially important for sources of pathogens such as urban areas, OSTDS, and dairy farms. Finally, greater efforts should be made to link pathogen-monitoring data to disease surveillance activities, as recommended in Chapter 6. Coordination with multiple organizations, such as the Watershed Agricultural Program, the New York City Department of Health, and the Catskill Watershed Corporation, will be necessary to effectively mitigate sources of pathogens in the Catskill/Delaware watershed. After pathogens, New York City should focus efforts on the reduction of DBPs, both present and emerging. Because disinfection via chlorination is likely to continue (even if only to maintain a disinfectant residual following ozonation), control of DBPs will require precursor (organic carbon) removal. NYC DEP has started to characterize and compare sources of DOC in the reservoirs, an activity that should be extended to all Catskill/Delaware reservoirs. Current NYC DEP efforts to reduce phosphorus loading to the reservoirs are an important step in controlling DBP formation. However, it is highly likely that management of allochthonous DOC will be necessary to control DBP formation because of the recalcitrance of allochthonous DOC and its dominance during winter months. It should be noted that watershed management may not be capable of reducing allochthonous DOC levels to meet future DBP regulations. This may necessitate additional treatment. Reliable estimates of the sources of natural organic carbon compounds are critical to evaluating future treatment processes that may be needed to control DBP formation. Efforts to control phosphorus loading to the reservoirs have been strong to date, and a significant body of monitoring data and terrestrial models have been generated to determine the sources of phosphorus. NYC DEP should concentrate on measuring the success of nonpoint source BMPs in reducing both particulate and soluble phosphorus. Nonpoint sources are the logical future focus of phosphorus reduction efforts rather than WWTPs, which are adequately addressed by the MOA upgrades. More effort should be applied to control sources of turbidity in the watersheds rather than downstream in aqueducts and reservoirs. As outlined above, a more comprehensive erosion control program is needed throughout the watershed. Controlling turbidity at its origins has benefits beyond compliance with the SWTR. For example, controlling particulate-phase pollutants that might otherwise reach Kensico and other reservoirs will prolong the service life of the reservoirs and reduce maintenance costs in proportion to sediment accretion rates.
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Watershed Management for Potable Water Supply: Assessing the New York City Strategy New York City should consider using a regular scientific external review/advisory process to expedite the use of new scientific information during watershed management. Whether particular areas of the watershed management program generate and use scientific information is highly variable. For example, phosphorus has been the subject of intense research and monitoring, while pathogens have received much less attention. New scientific information on wastewater treatment had a major role in the upgrades of WWTPs, but almost no role in improving OSTDS (which serve a substantial proportion of the watershed population). Disparities between state-of-the-art science and on-the-ground implementation are also apparent in the MOA's use of setbacks, in the Watershed Agricultural Program, in the Stormwater Pollution Prevention Plans, and in the phosphorus offset pilot program. Integration across programs within the watershed management strategy is needed. One way to accomplish this would be to hold an annual workshop during which all program managers would discuss their accomplishments to date, the challenges and problems, and future goals (perhaps with an external scientific advisory panel). This process could identify gaps and overlap between the programs and could better prioritize actions. ECONOMIC DEVELOPMENT IN THE WATERSHED REGION The MOA is the result of a lengthy and complex bargaining process among parties concerned with maintaining the economic and social viability of the watershed region on the one hand and protecting the water quality on the other. As summarized in Chapter 1, the MOA emerged from a sometimes acrimonious negotiation process that extended over many months. Difficult as the negotiation was, the signing of the MOA has allowed New York City and the watershed communities to move from impasse toward realization of their goals of watershed protection and economic growth. The potential for conflict between these two objectives was acknowledged during the negotiation process and is specifically addressed in the MOA and in the Watershed Protection and Partnership Programs. A substantial financial resource provided by the City under the MOA, the Catskill Fund for the Future, is being used to fund only environmentally sensitive development projects. This $59.7 million dollar fund has the potential complement the extensive infrastructure upgrades and regulatory actions undertaken in the interest of water quality and to fund income-generating activities that will advance the economic welfare of the region. Although it is too early to assess the success of the Catskill Fund for the Future, the committee believes that development consistent with maintenance of water quality is a realistic and achievable goal. Success in directing regional development depends upon a clear understanding of the impacts of various activi-
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Watershed Management for Potable Water Supply: Assessing the New York City Strategy ties on water quality as well as having the political will to direct and assist development in accord with current knowledge. Because the relevant science continues to grow and change, it is important for the parties to periodically review existing regulations and policies and to make adjustments in cases where either a significant added benefit to environmental protection can be obtained or controls can be modified without adverse impacts on water quality. What is the Future of the Catskill/Delaware Region? The recently completed comprehensive overview of the watershed economy shows that the decade of the 1990s has been a period of economic decline for the Catskill/Delaware watershed (HR&A, 1998a,b). Between 1990 and 1997, the five watershed counties experienced an overall decline in employment of some seven percent, and real wages declined in every sector except finance, insurance, and real estate. For services, which as the largest employment sector accounted for 40 percent of all jobs, the decline in real wages was comparable to the decline for the State as a whole (1.2 vs. 1.8 percent). For the next three largest employment sectors—retail trade, manufacturing, and government, which collectively account for about 42 percent of all jobs—real wages fell more than the respective New York State averages did during the same period. The decline in regional real wages occurred even though real wages in the watershed counties are substantially lower than the State average wages for every Standard Industrial Classification Sector (HR & A, 1998a). This suggests that the labor force of the region is not highly mobile. External markets have not, for the most part, driven recent regional economic growth. The largest and fastest-growing sector in the watershed, the service sector (including education, healthcare, and social services) serves the local population rather than short-term visitors or persons outside the region. Private sector service jobs, often oriented toward servicing visitors to the region, declined between 1990 and 1997 as the result of the loss of hotel employment opportunities. One of the goals of the comprehensive economic study is to assist the Catskill Watershed Corporation in defining objectives for the Catskill Fund for the Future in terms of markets to address and products or services to provide. Tourism and recreation, arts and crafts, and specialty manufacturing are among the major activities identified by the study that may hold promise for growth. Even given possibilities and the impetus provided by the growth-promoting programs under the MOA, the committee sees few signs that rapid increases in economic activity are likely in the region.
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Watershed Management for Potable Water Supply: Assessing the New York City Strategy sions of the MOA are carried out as envisioned, the quality of life in the region will be improved. Is the Concept of Balancing Development Restrictions and Incentives a Sound Strategy? The committee believes that the concept of balancing development restrictions and incentives is a reasonable strategy for New York City and possibly other communities. Because the City committed substantial financial resources to help advance environmentally sensitive development, other regulatory, land acquisition, and water quality investment programs that will contribute significantly to protection of its drinking water supply are moving forward. The Land Acquisition Program, which will seek to solicit 355,000 acres (approximately 30 percent of the Catskill/Delaware watershed), can affect the distribution of new economic activity within the region and alter the competitive prospects of areas within the watershed. Because of the possibility of acquiring such a large percentage of the total land area, the City has reviewed potential and existing recreational uses of City property. The potential for environmentally sensitive uses of City property should be thoroughly explored with the intent of making City ownership of land recognized as an asset that complements and assists regional growth rather than as an inhibitor of regional economic advancement. In the committee's opinion, the infrastructure improvements (if implemented) and financial assistance provided by the Watershed Protection and Partnership Programs should reduce the adverse impacts of existing development and provide the capacity to accommodate environmentally sustainable growth for several decades. The program expenditures have the potential to benefit the watershed communities by creating job opportunities for the duration of the implementation phase. The lack of strong growth pressures in the Catskill/Delaware region increases the likelihood that assistance through the Catskill Fund for the Future will be effective in shaping future development. The committee recommends a continuing process of program evaluation to ensure that funds are most productively used to meet the goals of environmentally sustainable development. Does the MOA Adequately Protect Private Property Rights? Both the Land Acquisition Program and the Watershed Rules and Regulations raise questions about the rights of watershed property owners. In the committee's opinion, the MOA adequately considers both the private property rights and the economic, social, and political concerns of watershed residents, while allowing a wide range of actions to protect water quality. The imposition of setbacks along waterbodies within the watershed is similar to measures currently employed in Massachusetts and other states to protect water
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Watershed Management for Potable Water Supply: Assessing the New York City Strategy quality and riparian habitat and to alleviate future flood damage. The setbacks do not involve any right of public access. Although the owner is not compensated, the setback restrictions typically apply to only a narrow portion of land parcels. As such, they are likely to be upheld by courts as reasonable, limited constraints on private land development, with the balance of the property being available for development in accordance with local zoning laws. Within the Land Acquisition Program, New York City has made significant concessions regarding private property. For example, the City explicitly promised not to exercise its power of eminent domain, promising instead to acquire all land on ''willing buyer/willing seller" terms. The Land Acquisition Program excludes from acquisition land with structures and land within the self-defined growth boundaries of towns. The purchase of conservation easements will also soften the effects of the Land Acquisition Program on the use of land for acceptable purposes such as agriculture and recreation. MOA provisions regarding property rights were made without complete knowledge about the sources of pollution in the watershed. The committee has emphasized the importance of evaluating the relative contributions of pollution sources in the watershed, and it has made recommendations regarding prioritization of pollutants. As new information becomes available, New York City should revisit its land acquisition priorities. In particular, the City should consider how the exclusion of certain lands from acquisition will affect pollutant loadings. The overall water quality impact of the MOA can only be assessed once the requisite monitoring data and information are in place. BALANCING TREATMENT OPTIONS AND WATERSHED MANAGEMENT As mentioned in Chapter 1, some perceive watershed management and other treatment options (such as coagulation/filtration) to be mutually exclusive in New York City. Nevertheless, the City's filtration avoidance determination requires that designs for a coagulation/filtration plant be drawn up concurrently with implementation of the watershed protection strategy. Watershed management and treatment process such as disinfection and coagulation/filtration are examples of barriers that comprise the multiple-barrier approach to providing safe drinking water endorsed by EPA, water supply organizations, and this committee. Other barriers include having the highest-quality source water, using the best available treatment technologies, maintaining a clean distribution system, practicing thorough monitoring and accurate data analyses, having well-trained operators, and maintaining operating equipment. If effectively implemented, the MOA represents the first barrier in a multiple-barrier approach to providing high-quality drinking water to New York City residents.
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Watershed Management for Potable Water Supply: Assessing the New York City Strategy Why Additional Treatment Options Should be Considered Drinking water that meets or exceeds all the requirements of federal, state, and local authorities is, in a regulatory sense, defined as safe to drink. It is, however, not risk-free. That is, the concentrations of microbial pathogens and chemicals in drinking water are not zero. Fortunately, each barrier in a multiple-barrier approach can reduce the microbial and chemical risk of drinking water, and these benefits accumulate as additional barriers are placed between pollution sources and water consumers. Although it presently complies with all federal and state standards for drinking water quality, a time may come when New York City will want or need to add additional barriers for the protection of its drinking water supply. Direct filtration and alternative disinfection, for which risk reduction can be systematically quantified, are the most probable and well-characterized additional treatment options, given the pilot studies already completed on these processes. Changes in Future Regulations As discussed in detail in Chapters 3 and 5, future changes to federal regulations may compel New York City to adopt additional treatment processes. The water supply currently appears to be most vulnerable to noncompliance for haloacetic acids (HAAs). When the Stage 2 MCL for HAA5 is promulgated, New York City may not be able to comply unless DBP precursor removal is added to its treatment train. Turbidity may also become a factor within the next ten years. It is possible that negotiations on the long-term Enhanced Surface Water Treatment Rule will lead to a substantially lower allowable turbidity from unfiltered supplies, which might be difficult to meet without some process for particulate control (such as coagulation/filtration). In addition, specific requirements for inactivation and/or removal of Cryptosporidium are likely. Finally, EPA's Candidate Contaminant List contains 10 microbial parameters and 30 organic compounds. If any of these should be regulated in the future, having particulate/precursor treatment in place to supplement disinfection would be beneficial for controlling the microbial contaminants, and it could provide a location for addition of an adsorbent to remove organic contaminants. Uncertainty Because some sources of pollution within the Catskill/Delaware water have not been quantified or even identified (particularly for microbial pathogens), it is impossible to conclude that the present high water quality will be maintained indefinitely. Uncertainty regarding pollutant sources can be partially ameliorated by adding additional treatment processes to the water supply. Uncertainty regarding sources, transport, and fate is greatest for pathogens, particularly
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Watershed Management for Potable Water Supply: Assessing the New York City Strategy Cryptosporidium. The Monte Carlo analysis performed by the committee (Table 6-11) suggests that New York City's drinking water may present a risk to consumers that is greater than the acceptable risk level informally suggested by EPA (although the many caveats discussed in Chapter 6 must be kept in mind). Because Cryptosporidium oocysts are resistant to some disinfectants, the use of alternate disinfectants coupled with coagulation/filtration or some other particulate-control treatment could be used to lower this risk and reduce uncertainty. The sources of DBP precursors have also not been unequivocally determined in the watershed. The MOA's focused efforts on phosphorus control will have a positive influence on the plankton-generated precursors of DBPs. However, as discussed above, allochthonous DBP precursors are substantially more difficult to control, with streamside buffers having limited effect. Treatment processes such as coagulation and filtration may be necessary to control these organic materials in the future. Changes in Supply and Demand Although not a current threat, future demand pressures as well as future supply shortages caused by drought could force New York City to use supplementary sources of drinking water such as the Hudson River. Because of its poor quality compared to water from the Catskill/Delaware watershed, this water is highly likely to require additional treatment beyond chlorination and coagulation with alum (which are currently provided for). The existence of additional treatment facilities for the Catskill/Delaware system would allow Hudson River water to be blended into Catskill/Delaware water with minimal complications. Summary New York City and other signatories of the MOA are commended for bolstering the multiple-barrier approach to water supply protection. Although limitations are noted in this report, the MOA is a template for proactive watershed management that, if diligently implemented over the long term, will improve source water quality. The New York City MOA emphasizes the importance of watershed management as a first-line barrier in all water systems, whether they are filtered or not. Box 12-1 highlights recommendations regarding watershed management in New York City that are transferable to other communities across the country. The committee encourages New York City and managers of all other unfiltered water supplies to be receptive to the possibility of new and additional treatment options. The need may arise because of uncertainties about pollutant sources, the growing scientific understanding of the impacts of pollutants on human health, and changing regulations. For example, New York City may be required to filter its water, not because watershed management does not
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Watershed Management for Potable Water Supply: Assessing the New York City Strategy BOX 12-1 Transferable Conclusions and Recommendations Although this report addresses the watershed management strategy of New York City, its conclusions and recommendations are relevant to other source water protection programs, whether their source water is filtered or not. This box discusses some of the most global conclusions and recommendations. The reader is referred to specific chapters for more detailed information. Monitoring (Chapter 6) Operational monitoring of physical, chemical, and biological parameters should be event-based rather than based on fixed intervals for streamflow, shallow subsurface flow, precipitation, and WWTP effluent. Sampling at fixed intervals will miss significant loadings of pollutants, particularly those in the particulate phase such as microbial pathogens, sediment, and particulate phosphorus. This report strongly encourages the use of performance monitoring to determine whether watershed management is effective over the long run. Examples of such monitoring over a wide range of spatial scales are given. GIS (Chapter 6) Land use and land cover should be maintained as separate databases in a GIS that supports watershed management. GIS databases are most useful when they are made readily available to the public. Public Health and Risk Assessment (Chapter 6) Active disease surveillance of the consumer population is a component of watershed management for a drinking water supply that is not practiced by all communities. Active disease surveillance can reveal trends in endemic rates of disease and, if enhanced surveillance is practices, possibly detect outbreaks of disease. These techniques should be supplemented with epidemiological studies in order to determine the proportion of disease attributable to drinking water. Such studies should occur in water utilities where the population is sufficient to provide a statistically powerful evaluation. Risk assessment is a complementary and powerful tool that can be used to estimate the risk of infection from drinking tap water. The accuracy and significance of risk assessment calculations rely on high-quality data collected from the source water, on accurate estimates of water con-
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Watershed Management for Potable Water Supply: Assessing the New York City Strategy sumption, and on a determination among relevant stakeholders of an acceptable risk level. Risk assessment can be used to assess the overall impact of watershed management over time. Nonstructural Protection Strategies (Chapter 7) A land acquisition program is potentially one of the most successful strategies for source water protection. This report stresses the importance of prioritizing land for acquisition based both on proximity to bodies of water and on land use. Land use planning is also integral to watershed management. Non-structural practices such as zoning and public education are sometimes the most effective and least expensive ways to prevent future pollution in water supply watersheds. Their success relies heavily on adequate public participation and effective implementation through enforcement of plan provisions. TMDLs (Chapter 8) As demonstrated in New York City, the Clean Water Act's Total Maximum Daily Load program relies heavily on developing accurate models for terrestrial runoff and reservoir water quality. These models in conjunction with the TMDL framework can be powerful tools for determining the relative importance of pollutant sources and directing BMPs to reduce pollutant loading. Adapting, calibrating, and validating such models may be a difficult prospect for many smaller communities. Pollutant Trading (Chapter 8) New York City's phosphorus offset pilot program illuminates many important issues that should be considered in the development of effluent trading programs for WWTPs in other communities. First, these programs should clearly define baseline requirements for pollutant reduction beyond which additional reductions can be counted as surplus. The success of these efforts depends largely on the availability and efficacy of monitoring techniques for the pollutant of interest, which should play a role in determining whether effluent trading can be viable. The ratios used in an effluent trading program should reflect the specific goals of the regulatory agency, the unique conditions present in the community, and the characteristics of the pollutant.
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Watershed Management for Potable Water Supply: Assessing the New York City Strategy Antidegradation (Chapter 8) This report describes the wide variation among state antidegradation policies and their implementation. The most important issue that all state antidegradation programs should address is how the assimilative capacity of waters will be allocated, a stipulation that is not explicitly stated in most state policies. Depending on the individual regulations used to implement antidegradation, states should bolster their policies to include language about assimilative capacity and to ensure adequate discussions of the social and economic benefits of new discharges and the significance of new discharges in terms of how much assimilative capacity is used. Additional Treatment (Chapter 8) This report points out that as future regulations are promulgated, the need for additional treatment processes should be carefully considered. The use of ozone as a sole disinfectant is cautioned against because of the potential creation of biodegradable organic matter that may foul distribution systems. Treatment beyond disinfection alone can provide additional benefits to the consumer. An aggressive watershed management program coupled with effective water treatment would maximize public health protection. Nonpoint Source Pollution Control (Chapters 9 and 10) The limitations of urban stormwater BMPs for reducing pollutant concentrations in runoff are applicable to all communities. In particular, the efficacies of individual stormwater BMPs diminish when placed in series, and many BMPs do not have demonstrated performance ratings. For all BMPs discussed, including urban stormwater, forestry, and agricultural produce substantial and sustained benefits, but to comply with more stringent regulations for DBPs and microbial pathogens. Management of these constituents may be infeasible with the current water supply infrastructure simply because increasing disinfectant concentrations to kill more pathogens simultaneously increases the quantity of DBPs. By contrast, coagulation/filtration or its equivalent, when operated properly, is effective against microbial pathogens, particulates, and the organic carbon precursors of DBPs. Furthermore, additional treatment options can reduce risk by predictable amounts. As noted in Chapter 6,
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Watershed Management for Potable Water Supply: Assessing the New York City Strategy BMPs, performance monitoring is required to demonstrate their effectiveness over the long term. Monitoring techniques should be developed in parallel with the development of new, innovative BMPs. Multiple recommendations are given on the wise use of setbacks and buffer zones adjacent to bodies of waters, which are a popular type of structural BMP in many settings. In general, buffer zones should not be used as a sole management practice, but should instead be combined with other BMPs to increase overall pollutant removal. The efficacy of buffer zones depends primarily on (1) the establishment of sheet flow upslope of the buffer, (2) the appropriateness of the buffer vegetation, and (3) the regular harvesting of the buffer to remove accumulated pollutants. These management techniques must be applied to setbacks if setbacks are expected to function as buffer zones. Wastewater Treatment (Chapter 11) This report suggests that the presence of WWTPs in a water supply watershed will not lead to immediate declines in reservoir water quality if tertiary and quaternary WWTP upgrades, such as microfiltration and continuous backwash upflow dual sand filtration, are put in place and are maintained over the long term. The use of a travel-time criterion for siting WWTPs is cautioned against unless sufficient scientific evidence exists to support the choice of travel time. Many communities rely on individual septic systems, or OSTDS, in lieu of WWTPs. The most important factors controlling the efficacy of OSTDS are the choice of technology and enforcement activities to reduce failure rates. The committee strongly advocates the use of aerobic treatment systems as BACT and yearly inspections to maintain their ability to remove pollutants. Such requirements are more realistic than setting effluent standards for OSTDS, which would be difficult to comply with. Failure rates for OSTDS can be substantially reduced by siting them on slopes of less than 15 percent. direct filtration is credited with at least a 100-fold (2-log) removal of Cryptosporidium (Nieminski and Ongerth, 1995), suggesting that filtration could lower the risk of waterborne cryptosporidiosis by a factor of 100. It is clear that if other factors controlling water quality remain the same, treatment beyond disinfection alone can enhance public health protection in an unfiltered water supply. Although its contribution to risk reduction is more difficult to quantify than that of treatment technologies, watershed management is an essential component
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Watershed Management for Potable Water Supply: Assessing the New York City Strategy of a modern water supply system. Because its watershed management strategy has gained national prominence, the committee encourages New York City to lead in efforts to quantify the contribution of watershed management to overall risk reduction. For example, New York City may be able to demonstrate the risk-reducing effects of the MOA by comparing the results of regular risk assessment calculations. The New York City MOA outlines an ambitious and path-breaking program of source water protection, and it is a unique document in the history of water resource management. The program it advances is a prototype of the utmost importance to all water supply managers. The MOA provides for an extraordinary financial and legal commitment from New York City (1) to prevent existing and potential contaminants from reaching the source reservoirs, (2) to monitor a broad range of water quality and drinking water parameters, (3) to conduct new research on public health and water quality, and (4) to promote the economic and social well-being of the Catskill/Delaware watershed communities in an environmentally sustainable manner. New York City should maintain its standing as a national model for watershed management and sustainable source water protection. The committee is encouraged by the evidence of progress to date in achieving the goals of the MOA. Other public water supplies, whether using filtration or not, have much to learn from these accomplishments. REFERENCES Auer, M. T., S. T. Bagley, D. A. Stern, and M. J. Babiera. 1998a. A framework for modeling the fate and transport of Giardia and Cryptosporidium in surface waters. Journal of Lake and Reservoir Management 14(2-3):393–400. Auer, M. T., K. A. Tomasoski, M. J. Babiera, M. L. Needham, S. W. Effler, E. M. Owens, and J. M. Hansen. 1998b. Phosphorus bioavailability and P-cycling in Cannonsville Reservoir. Journal of Lake and Reservoir Management 14(2-3):278–289. Environmental Protection Agency (EPA). 1998. Interim Enhanced Surface Water Treatment Rule (IESWTR), Federal Register 13(24): 69478–69521. Hamilton, Rabinovitz and Altschuler, Inc. 1998a. West of Hudson Economic Development Study for the Catskill Watershed Corporation. Report 1: Baseline Economic Analysis and Community Assessment, June 22, 1998. Hamilton, Rabinovitz and Altschuler, Inc. 1998b. West of Hudson Economic Development Strategy. Report 2: Market Sector Assessment & Program Issues Analysis, September 25, 1998. Longabucco, P., and M. Rafferty. 1998. Analysis of material loading to Cannonsville Reservoir: Advantages of event-based sampling. Journal of Lake and Reservoir Management 14(2-3):197–212. New York City Department of Environmental Protection (NYC DEP). 1998a. Disinfection Study for the Catskill and Delaware Water Supply Systems. October 30, 1998. Valhalla, NY: NYC DEP. NYC DEP. 1998b. Calibrate and Verify GWLF Models for Remaining Catskill/Delaware Reservoirs. Valhalla, NY: NYC DEP. Nieminski, E. C., and J. E. Ongerth. 1995. Removing Giardia and Cryptosporidium by conventional treatment and direct filtration. J. Amer. Waterworks Assoc. 9:96–106.
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Watershed Management for Potable Water Supply: Assessing the New York City Strategy Schueler, T. 1995. The importance of imperviousness. Watershed Protection Techniques 1(3):100–112. Stepczuk, C. L., A. N. Martin, P. Longabucco, J. A. Bloomfield, and S. W. Effler. 1998a. Allochthonous contributions of THM precursors in a eutrophic reservoir. Journal of Lake and Reservoir Management 14(2-3):344–355. Stepczuk, C. L., A. N. Martin, P. Longabucco, J. A. Bloomfield, and M. T. Auer. 1998b. Spatial and temporal patterns of THM precursors in a eutrophic reservoir. Journal of Lake and Reservoir Management 14(2-3): 356–366.
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Representative terms from entire chapter: