Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 386
Watershed Management for Potable Water Supply: Assessing the New York City Strategy 9 Nonpoint Source Pollution Management Practices Nonpoint source (NPS) pollution is widely dispersed in the environment and is associated with a variety of human activities. These activities produce pollutants such as nutrients, toxic substances, sediment, and microorganisms that may be delivered to nearby waterbodies following rainfall or directly via atmospheric deposition. Under pristine conditions, land generally has an enormous capacity to remove pollutants from rainwater. For example, research in the Catskills has shown that undisturbed forests can remove as much as 90 percent of the nitrogen from rainwater before it can reach nearby streams (Lovett et al., 1999). However, activities that produce NPS pollution also cause changes in vegetative cover, disturbance of soil, or alteration of the path and rate of water flow. These physical changes may prevent the land from naturally removing pollutants in stormwater. Thus, there are two interacting effects of NPS activities: (1) production of a pollutant and (2) alteration of the land surface in a way that increases pollutant loading to receiving waters. The goals of NPS pollution best management practice (BMPs) are to maintain or restore the ability of the land to remove pollutants and to limit production of the pollutant. The intent of this chapter is to evaluate the BMPs that are being used to control NPS pollution in the Catskill/Delaware watershed. Because most BMPs are implemented within the framework of an NPS pollution control program, this chapter reviews and critiques a variety of such programs (1) the Watershed Agricultural Program, (2) the Watershed Forestry Program, and (3) the Stormwater Pollution Prevention Plans. Conclusions and recommendations are made for the BMPs and for the NPS pollution control programs in general. Table 9-1 lists potential nonpoint sources, priority pollutants, and some of the qualitative and quantitative criteria that can be used to rate NPS pollution
OCR for page 387
Watershed Management for Potable Water Supply: Assessing the New York City Strategy TABLE 9-1 Nonpoint Sources, Priority Pollutants, and Potential Criteria for Evaluating NPS Pollution in the New York City Watersheds (Not all table entries are considered in this report) Nonpoint Sources Priority Pollutants Evaluation Criteria • Agriculture • Phosphorus • Total land area covered under the MOA • Urban stormwater • Organic carbon compounds • Export coefficient • Construction/roads • Turbidity/TSS • Best management practices used • Forestry • Cryptosporidium • NYC DEP performance monitoring data of BMPs • On-site sewage treatment and disposal systems • Giardia • Are BMPs implemented using best available technology? • Atmospheric deposition • Fecal coliforms • National performance/general effectiveness • Does BMP efficiency depend on regular maintenance? • Are there appropriate institutions to ensure full-scale implementation? control programs. This review is not comprehensive; for example, atmospheric deposition is not specifically addressed. This is because nitrogen loading is not primary pollutant associated with atmospheric deposition, and nitrogen loading is not a particular concern in the watershed region. In addition, atmospheric deposition of pollutants onto the land surface might be treated by the BMPs designed to treat other sources of nonpoint pollution. NONPOINT SOURCES PROGRAMS NPS pollution is a problem that is becoming increasingly important in the Catskill/ Delaware watershed, as evidenced by at least 30 different programs developed to reduce its impact. In fact, the New York City Department of Environmental Protection (NYC DEP) identifies almost all the regulations in the Memorandum of Agreement (MOA) as dealing with NPS pollution (NYC DEP, 1998a). Because these programs are not integrated into one overall program, there can be some confusion when trying to evaluate the methods being used to manage NPS pollution in the New York City watersheds. Sources for NPS pollution programs that affect the New York City water supply include (1) the Watershed Rules and Regulations of the MOA, (2) the May 1997 Filtration Avoidance Determination (FAD), (3) the Watershed Protection and Partnership Programs of the MOA, and (4) various State programs.
OCR for page 388
Watershed Management for Potable Water Supply: Assessing the New York City Strategy Watershed Rules and Regulations The Watershed Rules and Regulations contain most of the NPS pollution programs conducted by NYC DEP. These programs include three basic mechanisms for controlling NPS pollution (NYC DEP, 1998a): (1) strict performance standards applied to activities that produce NPS pollution, (2) a review and approval process for activities that produce NPS pollution, and (3) prohibition of certain activities in a ''setback" region between the activity and nearby waterbodies. Performance standards exist for wastewater treatment plants (WWTPs) that discharge to the subsurface but not for on-site sewage treatment and disposal systems (OSTDS), stormwater BMPs, agricultural BMPs, and forestry BMPs. Although it is technically feasible to monitor performance standards for all these activities, it can be difficult and expensive because of the diffuse and episodic nature of pollutant transport. The Stormwater Pollution Prevention Plan (SPPP) is a good example of a review and approval process used to control NPS pollution. All construction activities affecting more than five acres must prepare an SPPP and receive approval before the project commences. Finally, setbacks have been designated for a range of activities, including OSTDS construction, hazardous materials storage, the construction of impervious surfaces, siting of landfills, and residential pesticide application. These setback distances, which vary depending on the activity and the type of waterbody nearby, are evaluated in detail in Chapter 10. Filtration Avoidance Determination and the Watershed Protection and Partnership Programs The FAD and the Watershed Protection and Partnership Programs indirectly manage NPS pollution. The FAD requires that Total Maximum Daily Loads (TMDLs) be calculated for the reservoirs and that a phosphorus offset pilot program be developed, both of which require implementation of NPS pollution BMPs. The Watershed Agricultural Program is included under the FAD, although agricultural BMPs are not specified. Finally, the Watershed Protection and Partnership Programs include the Watershed Forestry Program and the Stream Management Program, which discuss control of NPS pollution. New York State NPS Pollution Programs NYC DEP participates in a number of State activities relating to NPS pollution, including the New York State Nonpoint Source Coordinating Committee. NYS DEC is the primary state agency for controlling NPS pollution as part of its enforcement of the Clean Water Act (CWA). In many cases, the Watershed
OCR for page 389
Watershed Management for Potable Water Supply: Assessing the New York City Strategy Rules and Regulations mirror provisions in State regulations, and NYC DEP oversight provides additional protection. AGRICULTURE IN THE CATSKILL/DELAWARE WATERSHED Agriculture, the predominant industry in the Catskill/Delaware watershed, is concentrated primarily in the Cannonsville and Pepacton watersheds. As shown in Figure 9-1, farms are relatively evenly distributed across the Delaware watershed, with many found close to major tributaries such as the West Branch of the Delaware River. Farms become more sparse in the eastern portion of the watershed because of more mountainous terrain and relatively poor soils. Ninety (90) percent of the 351 farming operations in the Catskill/Delaware watershed are dairy farms, most of which have between 50 and 200 animals.1 Most farms in the region also support crop production and contain significant tracts of forest. Although dairy cows are the predominant animal at farms participating in the Watershed Agricultural Program, a wide variety of other animals can be found (Table 9-2). Watershed Agricultural Program The Watershed Agricultural Program (WAP) is a voluntary program intended to standardize and improve environmental practices among watershed farmers. Because of the WAP, all agricultural activities in the Catskill/Delaware watershed are exempt from MOA regulations such as setback distances, discharge permits, and rules regarding pesticide application. To date, many in the farming community and most of those concerned about the quality of New York City drinking water have been ardent advocates of the program. This broad support is testimony to the strong affinity for agriculture as an important economic endeavor in the Catskill/Delaware watershed region. The WAP is administered by the Watershed Agricultural Council (WAC), a grassroots organization composed of farm, agribusiness, and environmental leaders. Since 1993, the primary role of the WAC has been to review and approve changes being made on individual farms to improve the water quality of nearby receiving waters (both surface and subsurface). One of the unique features of the WAP is its strong connection to basic research being conducted by Cornell University on the sources and transport of pollutants from agricultural practices. With funding usually supplied by NYC DEP, scientists at Cornell have studied the hydrology, phosphorus transport, parasitology, and economics of the Catskill/Delaware watershed. Cornell 1 "351" refers only to those farms having a gross annual salary of at least $10,000, making them eligible for the Watershed Agricultural Program.
OCR for page 390
Watershed Management for Potable Water Supply: Assessing the New York City Strategy FIGURE 9-1 Farm locations in the Catskill/Delaware watershed. Courtesy of the NYC DEP.
OCR for page 391
Watershed Management for Potable Water Supply: Assessing the New York City Strategy TABLE 9-2 Livestock Types and Numbers in the Catskill/Delaware Watershed Livestock Type Number Mature Dairy 12,636 Dairy Heifers 8,758 Chickens 2,655 Beef Cattle 1,566 Veal Calves 790 Sheep 569 Horses 565 Deer 375 Pheasant 250 Other 284 Source: NYC DEP (1997a). researchers have also developed a mix of very useful process-based and empirical models to use as planning tools or to use in support of the planning process. Thus, the WAP has been in a position to apply research findings to actual farm practices at an early stage in the process. The WAP has largely focussed on understanding the role of agriculture in generating pathogens and phosphorus and on application of BMPs for pathogen and phosphorus control. Two activities that may change the overall focus of the program are manure export and the Conservation Reserve Enhancement Program. Whole Farm Plans Whole Farm Plans are comprehensive strategies for controlling potential sources of pollution at individual farms. For those farmers that participate in the WAP, a Whole Farm Plan, which addresses their specific problems and needs, is developed by a planning team consisting of the farmer and representatives from local Soil and Water Conservation Districts, the U.S. Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS), and the Cornell Cooperative Extension. The contributions of each organization to the Whole Farm Plans are described in Table 9-3, and the 11-step Whole Farm Plan process is outlined in Table 9-4. To date, 199 Whole Farm Plans have been completed and approved by the WAC (NYC DEP, 1999a). The main purpose of the Whole Farm Plan is to develop and implement BMPs that address pressing environmental concerns while being compatible with the farmer's mission and objectives. Specific BMPs are evaluated and approved
OCR for page 392
Watershed Management for Potable Water Supply: Assessing the New York City Strategy TABLE 9-3 Organizations Involved in Whole Farm Planning Organization/Party Role Farmer The focus of the Watershed Agricultural Program. Participation is voluntary. NYC Department of Environmental Protection A source of major funding and technical and administrative support to the WAP. One NYC DEP staff member is a member of the WAC. NYS Department of Environmental Conservation Ex officio member of the WAC, providing technical expertise on nonpoint source pollution control measures. USDA Natural Resources Conservation Service A source of technical and scientific expertise for the WAP. Its role in the watershed predates the WAP. Soil and Water Conservation Districts Grassroots organizations created by individual counties to supply technical expertise to farmers on conserving soil/water. Cornell Cooperative Extension Technical and managerial expertise to farmers as part of New York State's land grant university, Cornell University. Cornell University Original research focusing on water resources and pollution prevention in the New York City watershed. Source: WAP (1997). TABLE 9-4 Steps in the Whole Farm Plan Process Step Description 1 Identify farm mission, objectives, business plan, and resources, both short-term and long-term. 2 Inventory and analyze water, soil, air, plant, and animal resource information. 3 Determine the priority water quality (and other) issues for the farm. 4 Identify practices (BMPs) to address the priority water quality (and other) issues. 5 Evaluate the effects of these practices on water quality (and other) issues from Step 3. 6 Identify adequate alternatives that satisfy the WAP's water quality criteria. 7 Quantify the economic and management effects of the alternative practices. 8 Select and integrate the practices to be included in the Whole Farm Plan. Submit the plan to the Soil and Water Conservation District and the WAC for approval. 9 Develop tactical plans to ensure successful implementation of the approved Whole Farm Plan. 10 Implement the Whole Farm Plan. 11 Assist, monitor, and evaluate implementation of the Whole Farm Plan and evaluate progress toward addressing the priority issues. Source: NYC DEP (1997a).
OCR for page 393
Watershed Management for Potable Water Supply: Assessing the New York City Strategy by the planning team prior to their implementation. Once a plan is approved, the planning team develops a strategy for implementing the plan and measuring its success. Monitoring for changes in water quality at this stage is an ideal approach to measuring the impact of farm BMPs. However, in some cases the necessary monitoring techniques do not exist, or the staff or technical equipment is not available to conduct the monitoring. Thus, extensive monitoring of soil and water quality does not take place on a regular basis at all farms participating in the program. Planning teams ensure maintenance of the BMPs via field inspection and try to keep abreast of improvements in technology that should be considered for use. Focus of Agricultural Best Management Practices The BMPs that have been chosen for the farms in the Catskill/Delaware watershed are a direct outgrowth of the priority pollutants and the specific environmental problems present. They can be classified as one of three general types: (1) barriers to pollutant transport (source control), (2) landscape barriers, and (3) stream corridor barriers. As discussed in Chapter 5, livestock generates pathogens, underscoring the importance of managing manure on farms (NYS WRI, 1997). Nutrients, especially phosphorus, are also priority pollutants in the watershed. Typical phosphorus inputs occur in animal feed and fertilizers; typical outputs include animal waste, plant material, and fertilizer that does not penetrate the soil. Finally, pesticides are potential pollutants in the watershed, and the MOA does not regulate agricultural uses of these compounds. Common BMPs used in the watershed include barnyard management, improved manure storage, and the separation of calves from cows. A complete list of agricultural BMPs used in the WAP is given below (WAP, 1997): Barnyard water management system Conservation cropping sequence Cover and green manure crop Diversion Fencing Filter strip Grassed waterway or outlet Obstruction removal Pasture and hayland planting Pipeline Planned grazing system Access road Pathogen management Spring development Trough or tank
OCR for page 394
Watershed Management for Potable Water Supply: Assessing the New York City Strategy Stock trails and walkway Stripcropping—contour Structure for water control Nutrient management plan (manure spreading based on soil phosphorus recommendations) Pesticide management Subsurface drain Underground outlet Waste utilization (manure management) Windbreak Measuring Success Typically, the measures of success for water quality BMPs in agricultural settings have been related to the numbers of practices installed and the numbers of farms participating, an approach that was initially taken by the WAP. Several success metrics for the WAP are included in New York City's waiver from filtration: (1) the number of participating farms, (2) the number of Whole Farms Plans that are developed and approved, (3) the number of Whole Farm Plan implementations, and (4) the number of plans for which an annual evaluation has been completed. These measures were seen as important because of the contentious interactions between watershed farmers and City and State regulators. The WAP has not been prioritized by targeting specific farms with known pollution problems. Rather, farmers have been allowed (after observing the prototype of ten pilot farms) to join the program on a voluntary basis, regardless of the extent of pollution at their farm. These criteria have resulted in a large number of participating farms (317, over 90 percent of all eligible watershed farms). The most important measures of program success are monitoring data and other evidence that demonstrate a positive impact of new farm practices on water quality. This approach requires performance monitoring of BMPs, determining pollutant loadings emanating from these BMPs, and modeling the resultant water quality in nearby receiving waters. Unfortunately, linking the performance of BMPs with nearby water quality conditions is much more difficult to accomplish than determining the number of farms in the program or the number of plans implemented. To use this later approach, more information is needed on (1) the accumulation of pathogens and nutrients in source areas (as suggested in Chapter 6), (2) pathogen and nutrient wash-off from source areas during rainfall (i.e., pollutant loading in overland flow), and (3) transport of pathogens and nutrients through the shallow subsurface prior to reaching waterbodies (i.e., pollutant loading in subsurface flow). As suggested in a recent independent review of the WAP, this
OCR for page 395
Watershed Management for Potable Water Supply: Assessing the New York City Strategy approach relies on understanding the baseline pollutant conditions in the watershed and the receiving waters (CTIC, 1998). Monitoring of farm conditions is currently concentrated at only two locations–the Shaw Road control area and Robertson Farm—in the hope that data gathered at these locations will be applicable to the entire Catskill/Delaware watershed. This monitoring is based on a modified paired watershed approach to understanding the integrated effects of Whole Farm Plan implementation rather than being based on monitoring of individual BMPs. Preliminary data gathered since 1996 indicate that there are significant differences between the loading rates of different pollutants at the farm and at the control area (WAP, 1997). However, additional research must be conducted before these data can be used. Analysis of the Watershed Agricultural Program The whole farm planning approach taken by the WAP represents a significant advance compared to the standard conservation planning done by USDA-NRCS and associated agencies. Because of the level of resources available to the WAP and the early recognition that new scientific information was needed to accomplish the Whole Farm Plans, the WAP has been instrumental in attempting to integrate scientific information and farm plans for controlling nonpoint source pollution. Although the accomplishments of the WAP and the whole farm planning projects are substantial, gaps in knowledge, implementation, and monitoring underscore the difficulty of determining the level of ecological and environmental sustainability provided at the watershed scale by a suite of agricultural BMPs. As discussed below, specific areas that must be addressed to improve the whole farm planning process include the transport and loading of phosphorus (including issues of scale, modeling, and monitoring) and the transport of microbial pathogens. Transport and Loading of Phosphorus There have been numerous efforts over the last 20 years to study nutrient loadings (particularly phosphorus) from agricultural lands to the Cannonsville Reservoir via the West Branch of the Delaware River (WBDR), other tributaries, and subsurface flow. As described in Box 9-1, these efforts have revealed a wealth of information about the relative sources of phosphorus, average phosphorus concentrations in different types of runoff, and the efficacy of certain agricultural BMPs for reducing pollutant loading from some farm sources. Despite these efforts, there are still no scientifically based nutrient load reductions developed for the Cannonsville watershed. The following section discusses the importance of such requirements and the information needed to develop them.
OCR for page 396
Watershed Management for Potable Water Supply: Assessing the New York City Strategy BOX 9-1 The Model Implementation Program of the 1980s Phosphorus has been of considerable interest in the New York City water supply watersheds, especially in the West Branch of the Delaware River–Cannonsville watershed, for at least two decades. The first national demonstration of agricultural BMPs as a means of water pollution control was undertaken by USDA and EPA in 1977 as part of the Model Implementation Program (MIP). One of the MIP sites was the West Branch of the Delaware River (WBDR). MIP focused on control of dissolved phosphorus from animal wastes (particularly barnyard runoff), manure-spreading schedules, and conservation practices including waste storage, stripcropping, conservation tillage, conservation cropping, cover cropping, critical area planting, woodland improvement and harvest, and tree planting. As part of the MIP, barnyards on 275 farms were prioritized for treatment based on their distance from defined watercourses. Out of 154 high-priority barnyards, 91 were treated with BMPs. The practices applied included diversions, open drains, water-control structures, roof gutters, grading, fencing, livestock exclusion from streams, and pavement of heavily used areas. Treatment of some cropland with phosphorus and with erosion-control measures was accomplished, and an educational and advisory program for silviculture was established. Cornell University and NYS DEC subsequently studied the effects of the MIP in the Cannonsville watershed (Brown et al., 1984). As a result, a great deal was known about the potential sources of phosphorus, the appropriate analysis methods for phosphorus, and phosphorus transport mechanisms in agricultural watersheds. The MIP first focused on changing the size and management of dairy barnyards. Detailed monitoring data showed that barnyards can be treated to achieve a high level of phosphorus control (50–90 percent load reduction). Diversion of water flow from areas above the barnyard was found to be a critical factor in controlling runoff from barnyards. However, even though dairy barnyards were a significant source of phosphorus, the studies concluded that the Developing Phosphorus Reduction Goals. Two components are needed to assess the impact of farm activities on nearby water quality: (1) a water quality model for the Cannonsville Reservoir that predicts long-term phosphorus concentrations in relation to varying inputs and (2) phosphorus loadings from adjacent agricultural areas, considering both surface and subsurface contribu-
OCR for page 416
Watershed Management for Potable Water Supply: Assessing the New York City Strategy STORMWATER POLLUTION PREVENTION PLANS Urban stormwater is the final type of NPS pollution considered in this chapter. Most types of new, large-scale development in the New York City watershed region are required to submit a Stormwater Pollution Prevention Plan (SPPP) for controlling the quantity and quality of stormwater runoff generated by new impervious cover (MOA, Appendix X, Section 18-39). SPPPs specify best management practices that will prevent erosion and sedimentation during construction and any increase in the rate of pollutant loading in stormwater after construction. These plans must include a quantitative analysis demonstrating that runoff quantity and quality from postconstruction conditions will be less than or equal to that of preconstruction conditions. Whether or not an SPPP or some other type of stormwater plan is developed depends on a number of factors, including the proximity of the project to nearby waterbodies. For detailed information on the multiple types of stormwater plans and the activities that require them, see NYC DEP, 1997b. Although they have existed since 1993 as part of the NYS DEC's General Permit for stormwater discharges, SPPPs have recently received considerable attention because of their inclusion in the MOA for a variety of activities. Prior to the MOA, fewer activities required the drafting of an SPPP, and the regulatory oversight was spread among multiple agencies. It is not surprising, then, that SPPPs have spawned a great deal of confusion among engineers, developers, and local and State agencies about how SPPPs should be interpreted and implemented, since most of these organizations had no prior experience with stormwater quality control and/or stormwater BMP design. Stormwater Pollution Prevention Plan Contents An SPPP must include a description of the proposed construction activities. An estimate of pre-and postdevelopment runoff is required, considering both the quantity and quality of stormwater. Pollutants of concern vary, but often include biological oxygen demand, phosphorus, nitrogen, total suspended solids, organic matter, and bacteria. Measures that might be undertaken to reduce runoff rates and pollutant loading from stormwater are then presented. These measures are committed to a Stormwater Management Plan, which describes the specific BMPs that will be used to ensure that the postdevelopment runoff rates will not exceed predevelopment runoff rates for the 2-year, 10-year, and 100-year 24-hour storms. To prevent pollutant loadings, the Stormwater Management Plan must control the "first flush"—the first half inch of runoff from the 1-year, 24-hour storm event. However, there are no numeric standards requiring a certain amount of pollution to be removed by stormwater BMPs. Erosion and Sediment Control Plans are also part of an SPPP. These contain a complete description of the BMPs that will be used to control erosion during each phase of construction. The methods,
OCR for page 417
Watershed Management for Potable Water Supply: Assessing the New York City Strategy criteria, and documentation for preparing an SPPP are contained in a series of guidance and permit documents (NYC DEP, 1997b; NYS DEC, 1996). Performance of Stormwater BMPs Throughout the SPPP guidance document, it is clear that the goal is to prevent postdevelopment loadings of pollutants from exceeding predevelopment levels (NYC DEP, 1997b). The requirement is stated by the following: "Regulations require that pre- and postconstruction runoff characteristics not be substantially altered." In order for this to be achieved, the SPPPs rely on an underlying premise that current engineering technologies (i.e., stormwater BMPs) are capable of reducing postdevelopment pollutant loadings to predevelopment levels. Unfortunately, there is little basis for confidence that the current generation of urban stormwater BMPs can reduce pollutant loads to levels that approach predevelopment conditions. Table 9-7 provides a summary of reported nutrient removal rates for stormwater BMPs. Phosphorus Removal Although their removal rates are variable, most BMP groups have median annual removal rates in the 30 percent to 50 percent range for both soluble and total phosphorus (Table 9-7). Dry extended detention ponds and open channels TABLE 9-7 Median Removal Rates for Selected Groups of Stormwater Practices BMP Groups Median Removal Rate, % n TSS Total P Sol P Total N Nitrate Carbon Wet Ponds 36 67 48 52 31 24 41 Stormwater Wetlands 35 78 51 39 21 67 28 Sand Filtersa 11 87 51 -31 44 (-13) 66 Channels 9 0 (-14) (-15) 0 2 18 Water Quality Swalesb 9 81 29 34 ND 38 67 Notes: n is a number of performance monitoring studies. The actual number for a given parameter is likely to be slightly less. Sol P is soluble phosphorus, measured as orthophosphate, soluble reactive phosphorus, or biologically available phosphorus. Carbon is a measure of organic carbon (BOD, COD, or TOC). ND = not determined. a Excluding vertical sand filters and vegetated filter strips, but including organic filters. b Includes biofilters, wet swales and dry swales. Source: Brown and Schueler (1997). Reprinted, with permission, from Center for Watershed Protection, 1997. ©1997 by Center for Watershed Protection.
OCR for page 418
Watershed Management for Potable Water Supply: Assessing the New York City Strategy showed low or no ability to remove either total or dissolved phosphorus. Interestingly, several BMP groups—wetlands, water quality swales, and sand filters—exhibit very wide variation in phosphorus removal, suggesting internal nutrient cycling can be an important factor in determining BMP effectiveness. Some BMPs, such as sand filters, actually increase soluble phosphorus concentrations via desorption, dissolution, or extraction of phosphorus into the aqueous phase. These removal rates are average annual load reductions, and the removal rates do not account for diminished removal related to poor design or construction, age, or lack of maintenance. It is also important to remember that trapping of phosphorus within a stormwater BMP is only a temporary form of removal; ultimate removal is dependent on the cleanout, removal, and safe disposal of trapped sediments through periodic maintenance. For stormwater wetlands, continued phosphorus removal may require periodic replacement of wetland media as adsorption sites diminish over time (Oberts, 1997). The moderate phosphorus removal of stormwater BMPs needs to be balanced against the sharp rise in phosphorus loads produced by new development. The effect of stormwater BMPs on phosphorus load as a function of impervious cover is shown in Figure 9-3. At a low density of development (5 percent to 25 percent site impervious cover), the reduction in phosphorus load by stormwater BMPs keeps pace with the increased load produced by impervious cover. After that point, however, stormwater BMPs can no longer achieve predevelopment phosphorus loads. Bacterial Removal To date, studies evaluating the performance of stormwater BMPs in removing microbial pathogens have focused on bacteria. Urban stormwater BMPs must be extremely efficient if they are to produce stormwater effluents that meet the 200-CFU/100 mL standard for fecal coliforms at a site. Assuming a national mean storm inflow fecal coliform concentration of 15,000/100 mL (see Table 5-6), a 99 percent removal rate is needed to meet the standard. The limited research conducted to date indicates that current BMPs cannot meet this standard on a reliable basis. Only 24 BMP performance-monitoring studies have measured the input and output of fecal coliform bacteria from stormwater BMPs during storm events. These data, collected for fecal coliform, fecal streptococcus, and E. coli, are summarized in Table 9-8. For stormwater ponds, the mean fecal coliform removal efficiency was about 65 percent (range was from –5 percent to 99 percent). The mean removal efficiency calculated for sand filters was lower (about 50 percent), but these practices had a wider range in reported removal (–68 percent to 97 percent). It should be noted that most sand filter performance data have been collected in warm seasons, and most sites were in Texas—conditions unlike those in the Catskill/Delaware watershed. Grass swales and biofilters were found to have no ability to
OCR for page 419
Watershed Management for Potable Water Supply: Assessing the New York City Strategy FIGURE 9-3 Relationships between impervious cover, phosphorus loads, and stormwater BMP performance in a typical watershed. The grey band indicates typical "background" phosphorus loads from undeveloped watersheds. The BMP-Hi line illustrates the effect of reducing phosphorus loads using BMPs with an average long-term removal rate of 60 percent. The BMP-Lo indicates a 40 percent removal rate. It should be noted that actual curves in individual watersheds may be different. For example, the contribution of new septic systems that accompany development to overall phosphorus loading is not represented by these curves. Source: Schueler (1996). Reprinted, with permission, from Center for Watershed Protection, 1996. © 1996 by Center for Watershed Protection. TABLE 9-8 Comparison of Mean Bacterial Removal Rates Achieved by Different Stormwater BMP Groups Bacterial Indicator Bacterial Removal Rate, % Ponds Sand Filters Swales Fecal Coliform 65% (n =9) 51% (n=9) –58% (n=5) Fecal Streptococci 73% (n =4) 58% (n=7) ND E. coli 51% (n=2) ND ND ND=not determined Source: Schueler (1999). Reprinted, with permission, from Center for Watershed Protection, 1999. © 1999 by Center for Watershed Protection.
OCR for page 420
Watershed Management for Potable Water Supply: Assessing the New York City Strategy removal fecal coliform bacteria, with zero or negative removal reported in four of the five studies. Pet wastes and in situ multiplication of bacteria were cited as the primary reason for the poor performance. No performance monitoring data are available to assess the capability of infiltration or wetland BMPs to remove coliforms. The limited data on fecal streptococcus and E. coli removal by stormwater BMPs are generally comparable to the more abundant fecal coliform data, suggesting that fecal coliform is a sufficient indicator of these organisms. There are no current monitoring data on Giardia, Cryptosporidium, or Salmonella removal by stormwater BMPs. Based on the mediocre effectiveness of BMP removal mechanisms for fecal coliforms, and the survivability of cysts and oocysts in sediments, the committee expects that it will be difficult to reliably remove the protozoan pathogens from urban runoff using traditional stormwater BMPs. In summary, current BMP technology is not capable of removing fecal coliform bacteria to meet the 200-CFU/100 mL standard in stormwater discharges, assuming a national average bacterial concentration in stormwater influent. If no net increase in bacterial concentrations in postdevelopment runoff is desired, it may be necessary to install stormwater BMPs at both current development projects as well as at older, neighboring development sites. As written, the SPPPs call for a level of BMP performance that simply cannot be met with current stormwater techniques at most highly developed sites. As discussed in detail in Chapter 8, the use of multiple BMPs in series at individual sites cannot reduce postdevelopment loadings below predevelopment levels. Acreage Requirements for Stormwater Quality Controls With some exceptions, the Watershed Rules and Regulations exempt development projects of less than five acres in size from the stormwater pollution prevention plan requirements4. Many kinds of small-scale industrial and commercial development are thus allowed to produce phosphorus and bacteria loads without treatment. Most states and localities that currently regulate stormwater discharges have a much lower threshold for stormwater requirements (usually less than one acre) (Watershed Management Institute, 1997). Although it is true that even very low-acreage thresholds (30,000 ft2) have been found to allow as much as 25 percent of stormwater to pass through untreated (Booth and Jackson, 1997), the efficacy of stormwater management will be markedly improved by lowering the current threshold from five acres to one acre. A one-acre threshold 4 SPPPs are also required, regardless of acreage, for construction of a subdivision; construction of an industrial, commercial, multifamily, or municipal project where more than 40,000 sq. ft. of impervious surface will be created; a landclearing or grading project involving two or more acres that are partially located on slopes greater than 15 percent or within setback distances from waterbodies; construction of an impervious surface in a village, hamlet, village extension, or area zoned for commercial or industrial uses West-of-Hudson; or construction of an impervious surface within a East-of-Hudson designated Main Street area.
OCR for page 421
Watershed Management for Potable Water Supply: Assessing the New York City Strategy should be the basis for further refinement, using the GIS database to identify the most appropriate long-term threshold given land development patterns in the watershed. Sizing Criteria for Designing Stormwater BMPs The SPPPs contain three different sizing criteria that must be considered when designing stormwater treatment facilities. The chosen BMPs must treat the greater of (1) the first half inch of runoff from impervious areas of the site or (2) the runoff produced by the one-year, 24-hour storm event (approximately 2.5–3.0 inches of rainfall). In phosphorus- and coliform-restricted basins, the BMPs must treat the runoff produced by the two-year, 24-hour storm event (approximately 3–4 inches of rainfall). The latter two sizing criteria are among the largest sizing criteria for stormwater runoff in the United States. The regulations, however, provide no guidance for designing BMPs that can fulfill these requirements, either in terms of the hydrologic models that should be employed or standardized parameters. Consequently, design engineers and state and local regulatory agencies are in frequent conflict as to how SPPPs should be interpreted and applied. The derivation of more effective sizing criteria should become a high priority for NYC DEP. It should be noted that the larger stormwater treatment volumes do not necessarily lead to proportionately greater levels of pollutant removal. For example, a BMP designed to capture runoff from the one-year storm is able to treat 90 percent of the annual stormwater runoff volume each year (MDE, 1999). A BMP designed to capture runoff from the two-year storm is able to treat only 95 percent to 97 percent of the annual runoff volume produced each year, even though it is four times larger in size (and cost). BMP research has shown that treatment volume alone is not a reliable predictor of pollutant removal performance. Other design variables, such as internal geometry, pretreatment, conveyance, and multiple treatment pathways, are very important in determining pollutant removal. Yet the SPPP requirements offer minimal guidance on these other important design parameters. The lack of a stormwater design and engineering manual and of performance criteria for individual BMPs for the New York City watersheds is a major impediment to achieving higher and more consistent pollutant removal. Other states such as Maryland have recently produced detailed and useful manuals to assist engineers in designing and building more effective BMPs (MDE, 1999). Need for Program Support The Watershed Rules and Regulations of the MOA have introduced stormwater control technologies into a region of the country that had little or no prior experience with stormwater management. The regulations emphasize a
OCR for page 422
Watershed Management for Potable Water Supply: Assessing the New York City Strategy permit-driven approach rather than a performance-based approach. That is, an SPPP relies strongly on quantitative (and highly theoretical) calculations, rather than on performance monitoring or strict requirements for BMP size and treatment efficiency. The SPPP program does not currently have the basic support needed to foster success in the areas of training, engineering manuals, performance monitoring, review staffing, program financing and demonstration projects, maintenance requirements, design methods, BMP feasibility guidance, construction and maintenance inspection criteria, or BMP specifications. As the Watershed Management Institute (1997) notes, strong program support in these areas has been the critical ingredient in effective implementation of stormwater requirements in other localities. It will be critical to the success of stormwater management in the New York City watersheds as well. Incentives to Reduce Impervious Cover The SPPP approach relies heavily on the use of structural stormwater practices such as ponds, wetlands, filters, and infiltration. Although these practices are an essential component of an effective stormwater quality strategy, they need to be combined with site design practices that reduce the amount or impact of impervious cover created by land development. Better site design techniques (narrower streets, open-space subdivisions, smaller parking lots, and on-lot bioretention) are being advocated by many stormwater agencies (Arendt, 1997; BASMAA, 1997; CWP, 1998; MDE, 1999). Recent modeling work has indicated that widespread application of better site design techniques can provide stormwater pollutant reduction equivalent to that achieved by structural stormwater practices (Caraco et al., 1998). When better site design techniques and structural practices are combined, nutrient loadings are projected to decline to levels 30 percent to 50 percent lower than what can be achieved using conventional subdivision designs. The Watershed Rules and Regulations and the SPPP requirements provide no incentives for developments that employ better site design techniques. Recently, the state of Maryland provided a series of stormwater quality credits for developments that use better site design (MDE, 1999). These credits could be adapted for developments in the New York City watersheds. Conclusions and Recommendations For phosphorus, current stormwater best management practices are only moderately effective. In almost all cases, they cannot reduce postdevelopment loadings to predevelopment levels. Most current practices show some ability to remove bacteria but not enough to meet current water quality standards. Swales are capable of no net
OCR for page 423
Watershed Management for Potable Water Supply: Assessing the New York City Strategy removal. Because urban areas are a source of Cryptosporidium oocysts (see Chapter 5), this deficiency is particularly notable. Stormwater Pollution Prevention Plans should be required for activities greater than one acre, rather than for those greater than five acres. The five-acre measure was likely derived from the fact that activities that affect less than five acres are generally not required to obtain an NPDES permit for stormwater. However, most communities have recognized that one acre is a more appropriate lower limit. Lowering the size requirement is important because much of the new development in the Catskill/Delaware watershed may be on a small scale. NYC DEP should develop guidance material for designing stormwater BMPs that can meet the one-year, 24-hour storm event and the two-year, 24-hour storm event. NYC DEP should embrace a performance-based approach to stormwater management rather than the permit-based approach embodied by the current SPPPs. Among other things, guidance material for such a new approach should include information on performance monitoring of stormwater BMPs for a variety of pollutants, including Cryptosporidium, and on long-term maintenance of stormwater BMPs. The Stormwater Pollution Prevention Plans should encourage the use of nonstructural BMPs that limit the amount and the adverse effects of impervious surfaces. Excellent examples of good site design practices using such BMPs are found in Maryland. REFERENCES Arendt, R. 1997. Designing Open Space Subdivisions. Media, PA: National Lands Trust and American Planning Association. Auer, M. T., K. A. Tomasoski, M. J. Babiera, M. L. Needham, S. W. Effler, E. M. Owens, and J. M. Hansen. 1998. Phosphorus bioavailability and P-cycling in Cannonsville Reservoir. Journal of Lake and Reservoir Management 14(2-3):278-289. Barten, P. K. 1998. Conservation of soil, water, and aquatic resources of the NorSask Forest. Prepared for Mistik Management, Ltd., Meadow Lake, Saskatchewan. Barten, P. K., T. Kyker-Snowman, P. J. Lyons, T. Mahlstedt, R. O'Connor, and B. A. Spencer. 1998. Managing a watershed protection forest. Journal of Forestry 96(8):10-15. Bay Area Stormwater Management Agencies Association (BASMAA). 1997. Start at the Source: Residential Site Planning and Design Guidance Manual for Stormwater Protection. Oakland, CA: BASMAA. Bentley, W., and W. Langbein. 1996. Seventh American Forest Congress: Final Report. Yale University, School of Forestry and Environmental Studies, New Haven, CT.
OCR for page 424
Watershed Management for Potable Water Supply: Assessing the New York City Strategy Booth, D. B., and C. R. Jackson. 1997. Urbanization of aquatic systems—degradation thresholds, stormwater detention, and limits of mitigation. Journal of American Water Resources Association 33(5):1077-1090. Brown, M. P., M. R. Rafferty, P. B. Robillard, M. F. Walter, D. A. Haith, and L. R. Shuvler. 1984. Nonpoint Source Control of Phosphorus: A Watershed Evaluation. Albany, NY: NYS DEC Bureau of Water Research. Brown, W., and T. Schueler. 1997. Pollutant Removal of Urban Stormwater Best Management Practices—A National Database. Ellicott City, MD: Center for Watershed Management, Chesapeake Research Consortium. Campbell, S. M., and D. B. Kittredge. 1996. Application of an ecosystem-based approach to management on multiple NIPF ownerships: A pilot project. Journal of Forestry 94(2):24-29. Caraco, D., J. Zieluski, and R. Claytor. 1998. Nutrient Loading from Conventional and Innovative Development Sites. Ellicott City, MD: Chesapeake Research Consortium, Center for Watershed Protection. Center for Watershed Protection (CWP). 1998. Better Site Design—A Manual for Changing Development Rules in a Community . Site Planning Roundtable. Ellicott City, MD: Center for Watershed Protection. Conservation Technology Information Center (CTIC). 1998. Review of the Watershed Agricultural Program. West Lafayette, IN: CTIC. Dana, S. T., and S. K. Fairfax. 1980. Forest and Range Policy. Second Edition. New York, NY: McGraw Hill. Davis, L S., and K. N. Johnson. 1987. Forest Management. Second Edition. New York, NY: McGraw Hill. Dillaha, T. A., J. H. Sherrard, and D. Lee. 1989. Long-term effectiveness of vegetative filter strips. Water Environment and Society 1:419-421. Ellefson, P. V. 1992. Forest Resources Policy: Process, Participants, and Programs. New York, NY: McGraw Hill. Forsyth, K., D. Haley, and R. Kozak. 1999. Will consumers pay more for certified wood products? Journal of Forestry 97(2):18-22. Haith, D. A., L. L. Shoemaker, R. L. Doneker, and L. D. Delwiche. 1984. Modeling of streamflow, sediment yield, and nutrient export from the West Branch Delaware River Watershed. Volume 4 in Brown, M., et al. (eds.) Nonpoint Source Control of Phosphorus: A Watershed Evaluation. Albany, NY: NYS DEC Bureau of Water Research. Hayward, J., and I. Vertinsky. 1999. High expectations, unexpected benefits: What managers and owners think of certification. Journal of Forestry 97(2):13-17. Jannik, P. 1998. Keynote address for Intl. Conference on the Science of Managing Forests to Sustain Water Resources. 9-11 November 1998, Sturbridge, MA. Kittredge, D. B., and C. Woodall. 1997. Massachusetts loggers rate portable skidder bridges. The Northern Logger 46(4):26-27, 36. Kittredge, D. B., C. Woodall, and A. M. Kittredge. 1997. Skidder bridge fact sheet. Amherst, MA: University of Massachusetts Extension. Leak, W. B., M. Yamasaki, D. B. Kittredge, N. I. Lamson, and M. L. Smith. 1997. Applied ecosystem management on nonindustrial forestland. USDA Forest Service GTR NE-239. Radnor, PA: USDA Forest Service. Longabucco, P., M. Rafferty, and J. L. Ojpersberger. 1999. Preliminary Analysis of the First Year of Sampling Data Following BMP Implementation at the Robertson Farm. Albany, NY: NYS DEC Bureau of Watershed Management. Lovett, G. M., and J. D. Kinsman. 1990. Atmospheric pollutant deposition to high-elevation ecosystems. Atmospheric Environment 24A:239-264. Lovett, G. M., and S. E. Lindberg. 1993. Atmospheric deposition and canopy interactions of nitrogen in forests. Canadian Journal of Forest Research 23:1603-1616.
OCR for page 425
Watershed Management for Potable Water Supply: Assessing the New York City Strategy Lovett, G. M., A. W. Thompson, J. B. Anderson, and J. J. Bowser. 1998. Elevational patterns of sulfur deposition at a site in the Catskill Mountains, NY. Atmospheric Environment (in press). Lovett, G. M., Weathers, K. C. and W. V. Sobczak. 1999. Nitrogen saturation and retention in forested watersheds of the Catskill Mountains, NY. Ecological Applications (in press). Maryland Department of Environment (MDE). 1999. Stormwater Design Manual. Volume I. Baltimore, MD: Maryland Department of Environment. Mater, C. M., V. A. Sample, J. R. Grace, and G. A. Rose. 1999. Third party, performance-based certification: What public forestland managers should know . Journal of Forestry 97(2):6–12. MDC (Metropolitan District Commission). 1995. Quabbin watershed: MDC land management plan 1995–2004. Boston, MA: Division of Watershed Management. National Research Council (NRC). 1990. Forestry Research: A Mandate for Change. Washington, DC: National Academy Press. NRC. 1998. Forested Landscapes in Perspective: Prospects and Opportunities for Sustainable Management for America's Non-Federal Forests. Washington, DC: National Academy Press. National Wildlife Federation (NWF). 1998. Quality not quantity: Community and economic benefits from MDC forestry at the Massachusetts Quabbin Reservoir watershed. Montpelier, VT: Northeast Natural Resource Center. New York City Department of Environmental Protection (NYC DEP). 1997a. Watershed Agricultural Program Preliminary Evaluation. December 1997. Valhalla, NY: NYC DEP. NYC DEP. 1997b. Applicants Guide to Stormwater Pollution Prevention Plans and Crossing, Piping, or Diversion Permits. May 1997. Valhalla, NY: NYC DEP. NYC DEP. 1998a. Quarterly Report on the Status of Implementing Projects Designed to Reduce Nonpoint Source Pollution. January 1, 1998–March 1, 1998. Valhalla, NY: NYC DEP. NYC DEP. 1998b. DEP Pathogen Studies of Giardia spp., Cryptosporidium spp., and Enteric Viruses . Semi-Annual Report. Valhalla, NY: NYC DEP. NYC DEP. 1999a. Watershed Agricultural Program Status Report. April 30, 1999. Valhalla, NY: NYC DEP. NYC DEP. 1999b. Filtration Avoidance Annual Report for the period January 1 through December 31, 1998. Corona, NY: NYC DEP. New York State Department of Environmental Conservation (NYS DEC). 1993. Silviculture Management Practices Catalogue for Nonpoint Source Pollution Prevention and Water Quality Protection in New York State. Albany, NY: NYS DEC. NYS DEC. 1996. Stormwater Guidance Documents. New York State Water Resources Institute (NYS WRI). 1997. Science for Whole Farm Planning: Cornell University Phase II Twelfth Quarter and Completion Report. Ithaca, NY: NYS WRI. Northern Forest Lands Council. 1994. Finding Common Ground. Conserving the Northern Forest. Concord, NH: Northern Forest Lands Council. Oberts, H. 1997. Lake McCavrons Wetland Treatment System—Phase III Study Report. Metropolitan Council Environmental Services. St. Paul, MN: Metropolitan Council Environmental Services. Rickenbach, M. G., D. B. Kittredge, D. Dennis, and T. Stevens. 1998. Ecosystem management: Capturing the concept of woodland owners. Journal of Forestry 96(4):18–24. Robillard, P. D., and M. F. Walter. 1984a. Phosphorus losses from dairy barnyard areas. Volume 1 in Brown, M. et al. (eds.) Nonpoint Source Control of Phosphorus: A Watershed Evaluation. Albany, N.Y.: NYS DEC Bureau of Water Research. Robillard, P. D., and M. F. Walter. 1984b. Development of manure spreading schedules to decrease phosphorus loading to streams. Volume 2 in Brown, M. et al. (eds.) Nonpoint Source Control of Phosphorus: A Watershed Evaluation. Albany, N.Y.: NYS DEC Bureau of Water Research. Schueler, T. 1995. The importance of imperviousness. Watershed Protection Techniques 1(3):100–112.
OCR for page 426
Watershed Management for Potable Water Supply: Assessing the New York City Strategy Schueler, T. 1999. Microbes in urban watersheds—Concentrations, sources, and pathways. Watershed Protection Technique 3(1):554–565. Smith, D. M., Larson, B. C., M. J. Kelty, and P. M. Ashton. 1997. The Practice of Silviculture. 9th Edition. New York, NY: John Wiley & Sons. Watershed Agricultural Program (WAP). 1997. Pollution Prevention through Effective Agricultural Management. Walton, NY: Watershed Agricultural Program. Walker, F. R., and J. R. Stedinger. 1999. Fate and transport model of Cryptosporidium. Journal of Environmental Engineering April 1999:325–333. Watershed Forest Ad Hoc Task Force (WFAHTF). 1996. Policy recommendations for the watersheds of the New York City's water supply. Ithaca, NY: NYS Water Resources Institute, Cornell University. Watershed Management Institute. 1997. Institutional Aspects of Urban Runoff Management—A Guide for Program Development and Implementation. Washington, DC: Office of Water, EPA.
Representative terms from entire chapter: