Computing appropriate septic system density (i.e. lot size) requires input of a target nitrate concentration into the Trela-Douglas model. The target concentration represents the nitrate protection standard that the Highlands Council has established for the Protection and Conservation Zones within the Planning Area of the Region. A number of different options were investigated for establishing the nitrate standards for these two zones.
The NJDEP, in establishing target nitrate concentrations in forested and non-forested areas within the Highlands Preservation Area, considered a number of different peer-reviewed data sources. For determining the target nitrate concentration for non-forested areas (i.e. mixed land uses), they selected the NJ Geological Survey report aimed at establishing baseline water quality in the New Jersey Highlands (Serfes, 2004), which provided the most conservative (i.e. lowest) value. According to the study, based upon results from 45 water samples collected from noncarbonated bedrock of northern New Jersey, the median nitrate concentration was 0.76 mg/L. The median value, rather than the mean, was selected as representing the “central tendency” of the data, as it minimizes the effect of extreme outliers that skew the mean.
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To assess nitrate levels under conditions that best represent pristine in contemporary terms, seven monitoring wells from the USGS QWDATA database that are located within the Highlands and surrounded by a 500-meter circular buffer that consists of at least 90% forest + wetlands + water, or conversely, less than 10% urban, agricultural, or barren land use, were identified. Although a low sample number, the 0.21 mg/L median nitrate concentration value for the seven monitoring wells is in close agreement with “background” surface water concentrations measured within the Highlands (a maximum nitrate concentration of 0.17 mg/L measured out of 20 samples collected from 1997- 2002). The 0.21 mg/L is also in close agreement with the USEPA’s Ambient Water Quality Criteria Recommendations (2001) manual for establishing a reference condition, which computed to 0.16 mg/L throughout sub-ecoregion 58, which consists of the Northern Highlands, including New Jersey/New York Highlands, as well as portions of Pennsylvania and states of the New England Highlands: Connecticut, Massachusetts, Vermont, New Hampshire, and Maine. In addition, the 0.17 mg/L value is in very close agreement with the 0.12 to 0.14 mg/L median nitrate concentration range estimated by USGS for undeveloped conditions using the logistic regression models.
In establishing the target nitrate concentrations for the Protection and Conservation Zones within the Planning Area, subwatershed median nitrate concentrations estimated with the logistic regression models calibrated to the 2002 water quality data were used. Several different approaches were investigated for establishing nitrate target concentrations with this data. As part of the process, it was recognized that the Conservation and Protection Zones should, by the nature of their markedly different land use characteristics, have different target nitrate concentrations. The data, when segregated by subwatershed, that are dominantly comprised of a particular zone clearly demonstrate statistical differences in median nitrate concentrations, as would be expected for different land use activities; for example, agricultural areas with high fertilizer loadings characteristic of the Conservation Zone generally have higher median nitrate concentrations than undeveloped areas characteristic of the Protection Zone.
Subwatersheds within the Protection and Conservation Zones that are primarily located within the Planning Area were identified, defined as any subwatershed that is more than 50% Planning Area (of the portion of its land located within the Highlands Region). Subwatersheds were identified as “dominantly” Protection or Conservation Zone if its total area within the Highlands Region was greater than 75% for the particular zone. For subwatersheds where no zone dominated, the Watershed Resource Value indicator was used (similar to the net water availability analysis, see Volume II of the Water Resources Technical Report), where “high” and “medium” values qualify the subwatersheds as Protection and Conservation Zones, respectively.
Because there is a fairly wide distribution of median nitrate concentrations even within a particular LUC Zone (for example, for the Conservation Zone median nitrate concentrations ranged from 0.44 to 3.08 mg/L), a bifurcation method was investigated. The method attempted to establish subwatershed specific target nitrate concentration that account for existing water quality conditions, as reflected by the median nitrate concentration estimated for each individual subwatersheds. The methodology would establish both a water quality goal concentration and a default target nitrate concentration value for each zone. A default value is necessary, given that the existing median nitrate concentration for some subwatersheds would invariably exceed any reasonable water quality goal. For example, the NJDEP has established a state-wide nitrate concentration target of 2.0 mg/L; accordingly, the water quality goals for the Protection and Conservation Zones could not exceed this value. However, there are a number of subwatersheds with median nitrate concentration estimates that already exceed the 2.0 mg/L state-wide target. The water quality goals and default values, then, are constrained by the need to be consistent with nitrate concentration targets and
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standards; they cannot be more stringent than the Preservation Area target concentrations or less stringent than the state-wide 2.0 mg/L target. At the same time, the water quality goal must be selected such that the default value is not excessively triggered, in effect becoming a de facto water quality goal, which would occur with lower water quality goals (i.e. the estimated median nitrate concentration of most subwatersheds would exceed the goal). After much analysis, a necessary balance between appropriate water quality goals and non-excessive triggering of an associated default value could not be achieved, and the method was rejected.
It was decided that the target nitrate concentrations for the Protection and Conservation Zones would be the estimated median nitrate concentration for the particular LUC Zone. This median- based target is consistent with how NJDEP established target nitrate concentrations for forested and non-forested areas within the Highlands Preservation area (0.21 and 0.76 mg/L, respectively), and how they developed the state-wide 2.0 mg/L target. Because the median nitrate concentrations were estimated only at the subwatershed scale, and not for specific zones (e.g. Protection), all subwatersheds primarily comprised of Planning Area and identified as dominantly one of the two Zones (i.e. Protection and Conservation) were included in the statistical sample for computing the median nitrate concentrations for the two Zones.
The tables Median Nitrate Concentrations for HUC14 Subwatersheds that are Dominantly Protection Zone and
Median Nitrate Concentrations for HUC14 Subwatersheds that are Dominantly Conservation Zone list the
different subwatersheds that apply for the Protection and Conservation Zones, respectively, along with their corresponding median nitrate concentrations estimated by logistic regression. Note that
the Papakating Creek subwatershed was excluded, as only 2200 ft2 of its area resides within the
Highlands Region, and consequently, was not considered sufficient to justify its inclusion for characterizing water quality conditions within the Region. Based upon the data, the two median nitrate concentrations for the Protection and Conservation Zones is 0.72 and 1.87 mg/L, respectively, which were used as the target nitrate concentrations. This method was the basis for nitrate targets in the Protection and Conservation Zones of the Planning Area.
For the Existing Community Zone, the NJDEP 2.0 mg/L state-wide target was selected. Although this does not represent the median nitrate value of 1.17 mg/L of this LUC Zone, it is appropriate that the anti-degradation standard reflect both of the goals and standards associated with the Existing Community Zone, as well as the state-wide ground water quality standard. It would be inconsistent with the zone standards to have the Existing Community Zone standard more stringent than the Conservation Zone, where more environmentally
Median Nitrate Concentrations for HUC14 Subwatersheds that are Dominantly Protection Zone
Subwatershed Name HUC14 Number Median Nitrate
Concentration (mg/L) Pequest R (below Bear Swamp to Trout Bk) 02040105070060 0.36
Pequest R (Drag Strip--below Bear Swamp) 02040105090010 0.36 Green Pond Brook (below Burnt Meadow Bk) 02030103030060 0.40
Black Brook (Great Swamp NWR) 02030103010060 0.44
Passaic R Upr (Pompton R to Pine Bk) 02030103040010 0.46
Trout Brook/Lake Tranquility 02040105070050 0.46
Great Brook (below Green Village Rd) 02030103010050 0.47 Wallkill River(Owens gage to 41d13m30s) 02020007030030 0.48
Lake Lenape trib 02040105070010 0.48
Prescott Brook / Round Valley Reservior 02030105020090 0.50 Whippany R (Wash. Valley Rd to 74d 33m) 02030103020020 0.52 Black Ck(above/incl G.Gorge Resort trib) 02020007040010 0.56 Black Creek (below G. Gorge Resort trib) 02020007040020 0.57
Union Church trib 02040105100010 0.59
Bear Creek 02040105080020 0.60
Musconetcong R(Waterloo to/incl WillsBk) 02040105150070 0.61
Primrose Brook 02030103010020 0.62
Paulins Kill (Blairstown to Stillwater) 02040105050010 0.63 Passaic R Upr (Plainfield Rd to Dead R) 02030103010110 0.65 Dead River (below Harrisons Brook) 02030103010100 0.69 Wallkill R(Hamburg SW Bdy to Ogdensburg) 02020007010040 0.70 Wallkill R(Martins Rd to Hamburg SW Bdy) 02020007010070 0.70 Whippany R (above road at 74d 33m) 02030103020010 0.71
Montville tribs. 02030103030160 0.72
Pequest River (above Brighton) 02040105070030 0.72
Middle Brook WB 02030105120060 0.74
Raritan R NB(Peapack Bk to McVickers Bk) 02030105060040 0.76
Drakes Brook (above Eyland Ave) 02030105010010 0.79
Sparta Junction tribs 02040105040050 0.79
Raritan R NB(incl McVickers to India Bk) 02030105060030 0.81 Wallkill R(41d13m30s to Martins Road) 02020007030010 0.83 Passaic R Upr (above Osborn Mills) 02030103010010 0.83 Pequest R (Cemetary Road to Drag Strip) 02040105090020 0.84
Lafayette Swamp tribs 02040105040040 0.86
Holland Twp (Hakihokake to Musconetcong) 02040105170010 0.88
Beaver Run 02020007010060 0.89
Lincoln Park tribs (Pompton River) 02030103110010 0.89 Rockaway Ck (RockawaySB to McCrea Mills) 02030105050090 0.89
Beaver Brook (above Hope Village) 02040105100030 0.98
Pequest R (below Furnace Brook) 02040105090060 1.00
Delawanna Creek (incl UDRV) 02040105060020 1.08
Honey Run 02040105100020 1.08
Hakihokake Creek 02040105170020 1.13
Lamington R (below Halls Bridge Rd) 02030105050110 1.20
Beaver Brook (below Hope Village) 02040105100040 1.27
Median Nitrate Concentrations for HUC14 Subwatersheds that are Dominantly Conservation Zone
Subwatershed Name HUC14 Number Median Nitrate
Concentration (mg/L)
Troy Brook (below Reynolds Ave) 02030103020090 0.44
Burnett Brook (above Old Mill Rd) 02030105060020 0.82
Raritan R NB (above/incl India Bk) 02030105060010 0.86
Paulins Kill (above Rt 15) 02040105040060 0.90
Bear Brook (Sussex/Warren Co) 02040105080010 1.02
Peapack Brook (below Gladstone Brook) 02030105060060 1.15 Lamington R(HallsBrRd-Pottersville gage) 02030105050070 1.24 Raritan R NB (Rt 28 to Lamington R) 02030105070010 1.29 Pequest River (Trout Brook to Brighton) 02040105070040 1.36 Raritan R NB (Lamington R to Mine Bk) 02030105060090 1.57
Pophandusing Brook 02040105110010 1.72
Beaver Brook (Clinton) 02030105020050 1.74
Pohatcong Ck (Merrill Ck to Edison Rd) 02040105140050 1.87 Harihokake Creek (and to Hakihokake Ck) 02040105170030 1.88
Pleasant Run 02030105040020 1.90
Musconetcong R (I-78 to 75d 00m) 02040105160050 1.95
Cold Brook 02030105050060 1.98
Nishisakawick Creek (below 40d 33m) 02040105170050 1.99
UDRV tribs (Rt 22 to Buckhorn Ck) 02040105110030 2.01
Middle Brook (NB Raritan River) 02030105060080 2.03
Musconetcong R (Rt 31 to Changewater) 02040105160030 2.03
Musconetcong R (75d 00m to Rt 31) 02040105160040 2.05
Nishisakawick Creek (above 40d 33m) 02040105170040 2.62
Cakepoulin Creek 02030105020060 2.74
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sensitive resources are located. Finally, the Existing Community Zone boundary was partly generated using utility infrastructure service areas such as public water and sewer. The use of new septic systems as a wastewater alternative will be limited to specific projects, such as in-fill, in this zone. The table Nitrate Dilution Targets for Various Areas within the Highlands Region is shown again displaying the nitrate targets for the different zone of the Highlands Region.
Nitrate Dilution Targets for Various Areas within the Highlands Region
Highlands Area/Zone Nitrate Dilution Target (mg/L)*
Preservation Forested Area 0.21
Preservation Non-Forested Area 0.76
Planning Area Protection Zone 0.72
Planning Area Conservation Zone 1.87
Planning Area Existing Community Zone 2.0