Use Classifications and Water Quality Criteria for New York State
The New York State Department of Environmental Conservation (NYS DEC) is the agency responsible for setting water quality criteria and waterbody use classifications for the New York City drinking water reservoirs. Much of this information is contained in the New York State Codes, Rules, and Regulations, Title 6, Chapter X, Parts 700-705. New York divides water into four main categories for the purpose of classification: fresh surface waters (which includes the New York City drinking water reservoirs), saline surface waters, fresh groundwater, and saline groundwater. Each category is then divided into classes that represent different uses. Water quality criteria (often expressed as concentrations averaged over a certain time period) correspond to these classes for a wide variety of physical, chemical, and biological parameters.
USE CLASSIFICATIONS-FRESH SURFACE WATERS
Eight classes of fresh surface waters are delineated: N, AA-special (AA-S), A-special (A-S), AA, A, B, C, and D. Class N waters are the most pristine and support the greatest number of uses. The best uses of Class N waters are "the enjoyment of water in its natural condition." This phrase is unique to Class N waters. Other uses of Class N waters include use as a drinking water source, bathing, fishing, fish propagation, and recreation. Discharge of sewage and industrial wastes into Class N waters is prohibited, unless the sewage effluent has traveled at least 200 feet through unconsolidated earth. In addition, these waters shall contain no substances that will contribute to eutrophication, nor shall they receive runoff containing such substances. It is not clear which waterbodies in
the state of New York carry this classification. None of the drinking water reservoirs of New York City are Class N.
Each class below N supports fewer uses, and restrictions on discharges into those waterbodies become less strict. Classes AA-S, A-S, AA, and A all support use as a drinking water source, culinary or other food processing source, for recreation, for fishing, and for fish propagation. In addition, Class AA-S waters cannot be polluted with solids, oils, sludges, sewage, and other wastes (which is actually a more stringent requirement than for Class N waters). Class AA-S waters shall also contain no nitrogen or phosphorus in amounts that will result in algal growth, weeds, or slimes (similar to the eutrophication requirement for Class N). The main difference between the three remaining "A" classifications concerns their use as a source of drinking water. Class A-S (international boundary waters) and A waters must be treated with coagulation, sedimentation, filtration, and disinfection (or their equivalents) to qualify as sources of drinking water. Class AA waters require only disinfection. All of the reservoirs in the Catskill/Delaware and Croton watersheds are classified as either A or AA. Classes B, C, and D include waters that can be used for recreation and fishing, but not as a source of drinking water. Waterbodies can be reclassified every three years.
WATER QUALITY CRITERIA
For each use classification, there is a list of physical, chemical, and biological parameters that characterize that classification. These criteria are included in Part 703 of the Water Quality Regulations. The criteria fall under three broad categories: health-based assuming the waterbody is a drinking water source, health-based assuming the waterbody contains consumable fish that might bioaccumulate contaminants, and aquatic-based. aquatic-based. For many chemicals, the criteria are set equal to their MCLs. For oncogenic chemicals, the criteria are based on a one in a million lifetime cancer risk, with does based on a 70-kg adult. Criteria can also be based on former regulations, aesthetic considerations, and chemical correlations. The "Basis for Establishment of Standards" is defined in Table 2, Part 703 of the Water Quality Regulations.
Some of the criteria are narrative; e.g., turbidity in all classes of waters must not increase to cause a substantial visible contrast to natural conditions. There are narrative criteria for nitrogen and phosphorus, stating that for all classes there shall be none in amounts that result in the growth of weeds, algae, and slimes that will impair the waters for their best uses. The 20-µg/L guidance value for total phosphorus that is currently used by NYS DEC appears in a subsequent revision of the Water Quality Regulations.
For almost all other important physical, chemical, and biological parameters, there are specific criteria. Dissolved oxygen, pH, Cl, fecal coliforms, and metals are of most concern for New York City. pH must fall between 6.5 and 8.5 for all
waters. Most of the other parameters of interest do not differ between the various use classifications. There are apparent differences are between Classes AA, A, and B and Classes C and D for zinc, arsenic, and selenium concentration. For dissolved oxygen, two new use "subclassifications" arise: trout (T) and trout-spawning (TS). Many of the Catskill/Delaware reservoirs have one of these additional subclassifications, shown in parentheses after the main classification, e.g. A(TS). The T and TS subclassifications require higher dissolved oxygen concentrations than the AA, A, B, and C classifications. (T and TS classifications are made by the Department of Fish and Wildlife after observing whether trout are present, and whether, based on water temperature, reproduction is possible.)
Table 1 in Part 703 of the Water Quality Regulations lists almost 160 different chemical substances for which there are numeric criteria. Metals, organics, pesticides, and herbicides are included. For the ammonia and ammonium standard, both health-based and aquatic-based criteria are given. The aquatic-based criteria are considerably more stringent and depend heavily on pH and temperature. Many of the criteria for metals depend on hardness. For substances considered in a group (e.g., dichlorobenzenes), the standard applies to the sum of all substances within that group.
The final table in Part 703 of the regulations, Table 3, gives criteria for point source effluents discharging directly into groundwater. These criteria are typically twice the allowable maximum concentration of the chemical in groundwater, but not always. There are a significant number of chemicals in Table 1 (and consequently Table 3) for which criteria are only given for groundwater and not for fresh or saline surface waters.
REVISIONS TO THE WATER QUALITY REGULATIONS
On October 22, 1993, major revisions to Part 703 the Water Quality Regulations were published by NYS DEC. There are 51 new entries to Table 1, and most contain guidance values rather than criteria. Guidance values may be used where a standard has not yet been established. Table 1 is considerably more complete as a result of the revisions. Chemicals have either criteria or guidance values for all possible water types (fresh surface water, groundwater, etc.). A new addition to Table 1 is the guidance value for total phosphorus of 20 µg/L. This value is based on aesthetic effects for primary and secondary contact recreation (unlike the narrative standard, which is based on eutrophication).
Finally, the revisions contain an additional section dealing exclusively with groundwater—the principal organic contaminant groundwater standard (POC). These criteria are meant to provide protection of groundwater from any organic compound, regardless of whether toxicity data exist.
WATER QUALITY IMPAIRMENT
NYS DEC is responsible for categorizing all waterbodies that are "use-impaired." This information can be found in several documents, including the biennial Clean Water Act 305b, the biennial Clean Water Act 303d report, the triennial NYS DEC Priority Waterbodies List, and numerous NYS DEC publications.
The Priority Waterbodies List (PWL) is the state's basic tool for identifying and organizing impaired waters. The state is divided into drainage basins; those basins that include the New York City reservoirs are the Lower Hudson River basin, the Delaware River basin, and the Mohawk River basin. All available information, including monitoring data, surveys, and public input, are used to evaluate the severity of the water quality impairment. If there is insufficient information for judging a waterbody's use impairment, it is not listed. Fortunately, a great deal of monitoring data exists for the New York City watersheds, and every reservoir and some major tributaries are currently listed.
The Degree of Designated Use Support qualitatively describes water quality. Threatened waters have water quality supporting designated uses, with no obvious signs of stress to ecological systems. However, existing or changing land-use patterns may result in restricted use or ecosystem disruption. Stressed waters have reduced water quality and designated uses are intermittently or marginally restricted. Natural ecosystems may exhibit adverse changes. Impaired waters have water quality and/or habitat characteristics that frequently impair a classified use. This term also applies to water supporting a designated use at a level significantly lower than would be expected. Natural ecosystem function may be disrupted. Precluded waters have water quality and/or associated habitat degradation that precludes, eliminates, or does not support a classified use. Natural ecosystem functions may be significantly disrupted.
For each individual waterbody, the PWL includes basic information about the acreage, the location, the use classification, the use impairments, pollutants, pollutant sources, the degree of designated use support, and the resolvability. In some cases the PWL identifies impairments to uses other than the primary use. Depending on the pollutants present, a waterbody may be more impacted for a secondary use than a primary use.
Three reservoirs in the Catskill/Delaware watershed are threatened for use as a source of drinking water: Neversink, Rondout, and Pepacton. Nutrients from urban runoff are the primary pollutants at Neversink, while Pepacton is impacted by pathogenic microorganisms from septic systems. Cannonsville, Schoharie, and Ashokan reservoirs are stressed, suffering from nutrients in agricultural run-off, silt from construction activities, and nutrients and silt from urban runoff, respectively. In the Croton watershed, West Branch Reservoir is stressed due to silt and nutrients derived primarily from urban runoff. The Kensico Reservoir is threatened for a variety of uses, with nutrients from urban runoff again as the
primary culprit. One major drawback of the PWL is that it does not include a breakdown of all pollutants exceeding the water quality criteria for each waterbody.
The 303d list is required by EPA to identify and rank waterbodies, which may require development of TMDLs. Inclusion on the list, however, does not mean that TMDL calculations will be completed during the following two years. The list simply identifies impaired bodies, describes the primary pollutants, and ranks the waterbody according to its level of impairment. It draws heavily upon the PWL, using an identical format for grouping the waterbodies and describing their condition. Whole sections of the 1996 PWL appear to comprise the bulk of the 1998 303d list.
The 303d list categorizes impaired waterbodies as (1) designated priority for TMDL development, (2) impacted by atmospheric deposition, (3) with fish consumption advisories, (4) closed to shellfish harvesting, (5) showing water quality criteria exceedances supported by monitoring data, and (6) requiring verification of water quality problems. A waterbody can fall into more than one category, but a review of the list shows that very few do. The New York City reservoirs are all designated priority for TMDL development.
The 305b list gives an overall description of the health of waterbodies in New York State. As of 1996, 93 percent of New York's rivers and streams fully supported their designated uses, while only 47 percent of lakes, ponds, and reservoirs support their designated uses. The report identifies nonpoint source pollution as the cause of water quality impairment, with agriculture, urban runoff, and septic systems cited as the most prevalent contributors. Point sources such as wastewater treatment plants are now relatively minor contributors to pollution. However, the report voices the need to upgrade and replace the wastewater treatment infrastructure, which is apparently approaching the limits of its normal life span.