Watershed Management for Potable Water Supply Assessing the New York City Strategy (2000) / Chapter Skim
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8 Phosphorus Management Policies, Antidegradation, and Other Management Approaches
8 Phosphorus Management Policies, Antidegradation, and Other Management Approaches
Pages 314-385
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From page 314... ...
, is a powerful tool for determining the relative contributions of point and nonpoint source pollution to the water supply reservoirs. The Phosphorus Offset Pilot Program, or "trading" program, was created to allow new point sources of pollution without increasing the overall level of pollution within a subwatershed.
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From page 315... ...
formation, nuisance algae and eutrophication, hypolimnetic anoxia, and taste and odor problems. Using phosphorus as the target of the TMDL program presents several challenges because it is somewhat ambiguous and controversial as an indicator of drinking water quality.
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From page 316... ...
The derivation of the Vollenweider equation and its use to convert phosphorus concentrations to phosphorus loads is discussed in Box 8-1. It should be noted that the use of the Vollenweider equation to estimate loadings to the water supply reservoirs is unusual.
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From page 318... ...
Because current state regulations prohibit septic systems within 100 It of a waterbody, the septic system contribution is made up primarily of preexisting and noncomplying systems. The Reckhow equation sums up all the point and nonpoint sources and produces an annual phosphorus loading in kg/year, which can be converted into phosphorus concentration, again using the Vollenweider equation.
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From page 320... ...
The main purpose of calculating a WLA is to set a permanent upper bound on phosphorus loading that can be incorporated into the SPDES permit of a WWTP. The LA is sometimes used to target best management practices to the appropriate nonpoint sources.
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From page 321... ...
In the Catskill/Delaware watershed, the Reckhow model was replaced in favor of the GWLF, which can predict the temporal and spatial variability in phosphorus loading. The GWLF is a numerical model that simulates hydrology, nonpoint source runoff of pollutants, and point source inputs.
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From page 322... ...
Water balance submodel of the Generalized Watershed Loading Function. water and surface runoff, are not currently available and have been derived from the literature up to the present time.
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From page 323... ...
Phase III Methodology Although Phase III TMDLs are not due for several years, NYC DEP has been developing more sophisticated models for this process. It is anticipated that the Vollenweider equation will be discarded in favor of a more complex water quality model that has both hydrothermal and eutrophication components.
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From page 324... ...
As presently formulated, these water quality models focus specifically on nitrogen, phosphorus, dissolved oxygen, and sediment. Water quality and terrestrial models for simulating fate and transport of microbial pathogens and precursors of disinfection byproducts are not currently under development.
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From page 326... ...
because it is an important part of the phosphorus offset pilot program to be discussed later, and (3) because it is used in conjunction with the controversial 60-day travel time (see Chapter 11~.
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From page 327... ...
Phosphorus-Restricted Reservoir Concept TMDL Phosphorus Restriction Governing Agency NYS DEC and EPA NYC DEP Requirements Multiple data sets/models required Phosphorus concentration data Regulatory Determines compliance with the Affects siting of WWTPs in the Implications Clean Water Act and affects New York City water supply SPDES Permits watersheds only Exceedance Test Phosphorus load corresponding Phosphorus concentration of to 15 ,ug/L exceeded 20 ,ug/L exceeded Consequence of Reduction in SPDES-permitted No new WWTPs can be Exceeding the phosphorus loads and nonpoint constructed in the basin; extra TMDL or source loads requirements for SPPPs. Phosphorus Standard Margin of Safety 90% of load is allocated No margin of safety Updating Infrequent revisions Annual revision
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From page 328... ...
Nonpoint sources will have to be reduced to meet the TMDL. Source: NYC DEP (1997a, l999c-t)
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From page 329... ...
However, in Phase II, all of the basins that exceed their TMDLs must reduce phosphorus loadings from nonpoint sources in order to comply. As a result, meeting Phase II TMDLs in these basins will be considerably more difficult and challenging than implied from Phase I calculations.
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From page 330... ...
Because the Vollenweider will probably not be used during Phase III (in favor of a time-variable water quality model) , its use in Phases I and II is not perceived as a problem by this committee.
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From page 331... ...
NYC DEP has argued that because eutrophication parameters are not acutely toxic, variations in phosphorus concentration (occasionally including high concentrations) will not adversely affect reservoir water quality as long as average phosphorus concentrations are maintained at low levels (NYC DEP, 1999a)
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From page 332... ...
Where nonpoint source reductions are needed, NYC DEP must embark on a vigorous plan to understand how BMPs can be employed to reduce phosphorus loading to the reservoirs. This is a difficult task because most watershed management actions required by the MOA are not tied quantitatively to the load reductions necessary to improve water quality.
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From page 333... ...
Other Parameters. It would be desirable to extend the TMDL calculations on phosphorus to water quality parameters that more directly influence health effects and the protection of the New York City drinking water supply.
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From page 334... ...
, turbidity, and taste and odor. These are the water quality parameters that affect drinking water quality directly.
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From page 335... ...
| | Respiration Pho~o.sy'`the* i.s ~J,Reaerotio,' Phytoplankton ~ Re.`pirati(}~, SOD ,|, |.Vitrificatio', FIGURE 8-2 Conceptual submodels of the nutrient/phytoplankton model for Cannonsville Reservoir: (a)
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From page 336... ...
It is not clear whether additional trophic levels, such as zooplankton grazing and fish predation, will be needed to simulate chlorophyll a concentrations accurately. In general, it is best to develop the simplest model that accurately simulates important drinking water quality variables.
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From page 337... ...
In general, methods that were used for Phases I and II of the TMDL program were adequate. The Vollenweider model was the best choice for a water quality model given the limited data available and the time constraints placed on the program.
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From page 338... ...
6. Data collection to support and validate the GWLF and other Phase III water quality models should be given a high priority.
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From page 339... ...
Will the proposed offset program be sufficiently cost-effective or include sufficient incentives to be successfully implemented? Overview of Watershed-Based Trading Since 1996, EPA has been promoting effluent trading as an innovative way to develop cost-effective, common-sense solutions for water quality problems in watersheds.
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From page 340... ...
nonpoint source/nonpoint source trading (EPA, 1996~. Trading programs developed by the states must meet CWA water quality requirements by ensuring a number of important conditions.
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From page 341... ...
The New York City Phosphorus Offset Pilot Program The phosphorus offset pilot program for the New York City watershed is one of only a few programs in the northeastern United States. On Long Island, a trading program to improve marine water quality is in its initial stages (M.
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From page 344... ...
. If the pilot program successfully achieves water quality and regulatory goals, it will serve as the basis for establishing a permanent phosphorus offset program in the future.
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From page 345... ...
can be added to reduce phosphorus loadings associated with Stormwater runoff from existing sites, particularly those that were initially developed without BMPs. Stormwater retrofits are structures, such as ponds and wetlands, that remove urban pollutants through sedimentation, adsorption, and biological methods (Claytor, 1996~.
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From page 346... ...
Nonpoint Source Phosphorus-Load Change. Associated changes in nonpoint source phosphorus loading that result from WWTP and all associated construction are then calculated.
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From page 347... ...
For land reclamation and wetland restoration mechanisms, the reductions are calculated as the difference in loads generated by the land in its restored form versus the load generated in its current form. Existing Applications for the Phosphorus Offset Pilot Program As of April 10, 1999, three applications are being considered by NYC DEP for the pilot program.
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From page 348... ...
The analysis below suggests that many offset mechanisms will be difficult to monitor and that some cannot achieve the pollutant reductions claimed in the applications. Analysis of the New York City Program The committee has reviewed the phosphorus offset pilot program and provides recommended improvements to address concerns in several areas.
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From page 350... ...
1. The guidance appears to permit the use of any urban nonpoint source practice as an eligible stormwater retrofit, such as might be found in the "Urban/ Stormwater Runoff Management Practices Catalogue for Nonpoint Source Pollution Prevention and Water Quality Protection" (NYS DEC, 1996~.
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From page 351... ...
were actually able to reduce phosphorus loads to predevelopment levels for forest or meadow conditions. In a modeling study, Caraco et al.
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From page 352... ...
Land Reclamation. Land reclamation is a preferred offset mechanism because of its long-term nature, because of the ability to effectively quantify load reductions from this mechanism, and because of the direct water quality benefits.
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From page 353... ...
Finally, the incremental phosphorus load reduction to be gained from individual septic systems is small. The phosphorus offset pilot program should focus on more effective and substantial offset mechanisms.
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From page 354... ...
Higher trading ratios can also reflect a net reduction strategy, although this is not a stated goal of the New York City pilot phosphorus offset program. Establishing a scientific basis for trading ratios is an important component of any credible trading program.
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From page 355... ...
The Cherry Creek Basin program justifies its trading ratio as providing a safety margin against several relevant uncertainties, including variability in phosphorus loading and BMP performance, uncertainties associated with laboratory analysis and data evaluation, and institutional uncertainties. All these uncertainties exist in the New York City phosphorus offset pilot program as well.
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From page 357... ...
The TMDL program provides another opportunity for consolidating monitoring efforts and ensuring the protectiveness of the pilot phosphorus offset program. Phosphorus TMDLs are expressed in terms of allowable annual loads that are allocated among several components: point sources, nonpoint sources, future growth, and a safety factor.
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From page 358... ...
A final economic consideration for the phosphorus offset pilot program is whether offset mechanisms can be identified. In the Cannonsville watershed (which is the only eligible West-of-Hudson watershed)
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From page 359... ...
5. There is no evidence that the phosphorus offset pilot program will result in a net reduction in phosphorus loading to the water supply reservoirs, because the offset ratios do not currently incorporate an additional factor to provide for net reductions in phosphorus.
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From page 360... ...
Federal Antidegradation Policy As set forth in federal regulations, antidegradation dictates that waterbodies cannot be allowed to sustain pollutant loadings that will prevent them from meeting their specific use classification and associated water quality criteria. It is considered one of the three points to the "Clean Water Act triangle," along with waterbody use classifications and water quality criteria (EPA, 1994~.
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From page 361... ...
EPA recently contracted with consultants to compare the antidegradation policies of 26 states, including New York (Cadmus Group, 1998~. The study considered how each state has interpreted the three tiers of the EPA guidance and related them to their existing use classifications and water quality criteria.
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From page 365... ...
Montana The applicant must demonstrate that important economic or social development spurred by the activity outweighs the cost to society of allowing the proposed change in water quality. In determining whether a proposed activity is necessary, the department considers the economic, environmental, and technological feasibility.
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From page 366... ...
Vermont The project associated with a proposed discharge cannot produce substantial social or economic costs unless those costs are offset by equal or greater benefits of maintaining or improving water quality. The state must also find that the discharge is necessary to prevent substantial adverse economic and social impacts.
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From page 367... ...
Water that does not meet the standards assigned thereto will be improved to meet such. The water uses and the level of water quality necessary to protect such uses shall be maintained and protected." (NYS DEC, 1985)
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From page 368... ...
Waterbodies can be reclassified sometime during the state's triennial water quality standards review process. An entire round of classifications generally takes ten years given the number of waters that must be assessed and the size of the NYS DEC staff.
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From page 369... ...
Analysis of New York State's Antidegradation Policy NYS DEC currently argues that having a separate, distinct antidegradation review process is redundant because the SEQR process and the SPDES permitting process can accomplish the goals of maintaining high water quality (Cronin, 1997; N
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From page 370... ...
. Potential Applicability Antidegradation is most useful when water quality criteria are less strict and allow waterbodies to have assimilative capacity, as discussed in Box 8-8.
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From page 371... ...
The cumulative impact of multiple actions and long-term effects must be considered. Although a "substantial adverse change in existing water quality" is listed as an important criterion, SEQR does not define a particular percent change in assimilative capacity as significant, unlike 11 other states' antidegradation policies.
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From page 372... ...
If so, it is then used to develop alternative waste load scenarios that will achieve water quality standards. NYS DEC has developed multiple guidance documents for calculating waste assimilative capacity under a variety of conditions.
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From page 373... ...
Because SEQR is the only avenue for regulating nonpoint sources that will impact water quality, this requirement for addressing assimilative capacity is critical if the SEQR process is to be relied upon for implementing New York's antidegradation policy. Further guidance from EPA on how to implement antidegradation policy for nonpoint source activities should be taken into consideration as soon as it is made available.
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From page 374... ...
Although not completely analogous, the dual-track approach is similar to the multiple-barrier approach to producing high-quality drinking water introduced in Chapter 4, provided that both tracks continue into the foreseeable future. Filtration Plant for the Catskill/Delaware Water Supply Phase I Pilot Plant Study To determine optimal conditions for building a filtration plant for the Catskill/ Delaware system, NYC DEP has recently completed a two-year pilot study.
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From page 375... ...
A weighted matrix analysis of the schemes was conducted, taking costs, acceptability, site considerations, flexibility and reliability, implementation, and water quality into account. The preferred treatment scheme consisted of one filtration plant at the Eastview location, which had been identified previously by NYC DEP as a potential site.
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From page 376... ...
The motivation for such research was threefold. First, disinfection with chlorine is the primary chemical treatment received by Catskill/Delaware water, but there have been no previous attempts to Chemicais Ozonat~on Chemicals Chemicals 1~ FIGURE 8-5 Proposed treatment train for direct filtration of the Catskill/Delaware water supply.
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From page 377... ...
. A major assumption was that the New York City water supply would continue to be of high enough quality to qualify for filtration avoidance.
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From page 378... ...
. To obtain varying times, the pilot plant was run at different flow rates, and samples were obtained at multiple intermediate times within the ozonation train.
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From page 379... ...
In addition, in the presence of bromide ion, ozone can lead to formation of bromate and bromine-substituted organic compounds. Because bromide levels were not measured in the disinfection study, the potential for bromate formation in the Catskill/Delaware water supply is currently unknown.
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From page 380... ...
At least 3-log oocyst inactivation/removal is expected for the entire treatment train. These low effluent pollutant concentrations from a potential filtration plant are dependent on maintaining high source water quality via aggressive watershed management.
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From page 381... ...
1993b. Memorandum on State Antidegradation Implementation Methods to Regional Water Quality Standards Coordinator from B
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From page 382... ...
1993. Implications of Phosphorus Loading for Water Quality in NYC Reservoirs.
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From page 383... ...
1999a. Development of a water quality guidance value for Phase II Total Maximum Daily Loads (TMDLs)
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From page 384... ...
1996. Urban/Stormwater Runoff Management Practices Catalogue for Nonpoint Source Pollution Prevention and Water Quality Protection in New York State.
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From page 385... ...
1994. Effluent Allowance Trading: A New Approach to Watershed Management.
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