HomeMy WebLinkAbout11b_C1_Engineering_WW Feasibility Study 12-23-2013 (1)
20 Shaker Rd., P.O. Box 730, New Lebanon, N.Y. 12125
www.clarkpc.com
Orient, New York
Decentralized
Wastewater Collection & Treatment
Feasibility Study
PHASE 1
Potential Site Identification
for:
Peconic Green Growth LLC
Suffolk County, NY
651 W. Main Street
Riverhead, NY 11901
(T) (631) 591-2402
www.peconicgreengrowth.org
December 23, 2013
Project No. 3941302
TABLE OF CONTENTS
Peconic Green Growth LLC – Wastewater Feasibility Report – Phase 1 i
SECTION 1 BACKGROUND
1.1 Introduction ........................................................................ 1-1
1.2 Wastewater Background ................................................... 1-1
1.2.1 Service Area and Flows .......................................... 1-2
1.2.2 Proposed Treatment System .................................. 1-3
1.3 Project Area Characteristics .............................................. 1-3
1.3.1 Location & Population ............................................. 1-3
1.3.2 Environmental Resources ....................................... 1-3
1.3.3 Flood Zones ............................................................ 1-4
1.3.4 Geology/Topography/Soils ..................................... 1-5
1.3.5 Groundwater ........................................................... 1-7
1.3.6 Land Use/Zoning .................................................... 1-8
SECTION 2 WASTEWATER SYSTEM ALTERNATIVES
2.1 Wastewater Collection Systems ........................................ 2-1
2.1.1 Conventional Collection System ............................. 2-1
2.1.2 Alternative Collection Systems ............................... 2-2
2.2 Wastewater Treatment Systems ....................................... 2-3
2.2.1 Conventional Treatment System Description .......... 2-3
2.2.2 Alternative Treatment System ................................ 2-4
2.3 Alternative Treatment Technologies .................................. 2-6
2.4 Wastewater Disposal Systems .......................................... 2-8
2.4.1 Seepage Pits .......................................................... 2-8
2.4.2 Open Recharge Beds ............................................. 2-9
2.4.3 Absorption Fields and Beds .................................... 2-9
2.4.4 Absorption Fields and Beds .................................. 2-10
2.4.5 Irrigation Wastewater Reuse ................................ 2-11
2.5 Wastewater Disposal Quality ........................................... 2-12
SECTION 3 TREATMENT SITE IDENTIFICATION
3.1 Treatment System Siting Constraints ................................ 3-1
3.2 Preliminary Parcel Screening ............................................ 3-5
3.3 Additional Parcel Considerations ..................................... 3-11
3.3.1 Park Land ............................................................. 3-11
3.3.2 Agricultural Districts .............................................. 3-11
SECTION 4PROJECT ADVANCEMENT
4.1 Additional Study Phases.................................................... 4-1
4.1.1 Treatment Site Identification ................................... 4-1
4.1.2 Collection and Treatment Alternative Evaluation .... 4-1
4.1.3 System Recommendations ..................................... 4-1
4.1.4 Costs & Funding ..................................................... 4-1
4.1.5 Implementation ....................................................... 4-1
Peconic Green Growth LLC – Wastewater Feasibility Report – Phase 1 ii
SECTION 5 REFERENCES
APPENDIX A ALTERNATIVE ON-SITE SEWAGE DISPOSAL SYSTEMS –
EXECUTIVE SUMMARY
APPENDIX B PRESSURIZED SHALLOW NARROW DRAINFIELDS
G:\Projects\3941302\Documents\Report\WW Feasibility Study 9-20-2013.docx
SECTION 1 BACKGROUND
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 1-1
1.1 INTRODUCTION
This report presents the initial phase of a wastewater feasibility study performed for
Orient. This phase identifies suitable sites within the hamlet for subsurface wastewater
disposal. Additional phases will determine the most appropriate and cost-effective means
of wastewater collection, treatment and disposal using the potential sites identified during
this phase.
1.2 WASTEWATER NEEDS
The January 2011 Suffolk County Comprehensive Water Resources Management Plan is
an extensive document which provides valuable information on the impact of human
activities on groundwater sources. One of the most significant contaminates of concern is
nitrate. Sources of nitrate include on-site sanitary wastewater disposal in un-sewered
areas, sewerage treatment plant discharges to groundwater, as well as the application of
fertilizers to agricultural and manicured lands. Nitrate from these sources has resulted in
contamination of drinking water supplies. Nitrate is also an important factor in
eutrophication.
Wastewater has high levels of nitrogen and phosphorus. Both of these components are
known as good fertilizers. Once introduced into a body of water, they cause increased
plant growth, specifically of algae, which will bloom, then die and fall to the bottom of
the water body and decompose. The decomposition of algae fuels bacterial growth,
which consumes oxygen. Aquatic life needs oxygen and without it the water becomes
“dead” which means unsuitable to sustain life. Algal blooms not only harm animals, but
also block sunlight from reaching plants, which stunts or stops plant growth, destroying
habitat.
The Comprehensive Water Resources Management Plan presents data which shows
improved wastewater treatment is effective at lowering environmental nitrate levels. The
goal of wastewater improvements in Orient will be effective treatment to preserve
drinking water and environmental quality while providing a treatment system that would
be compatible with the character and concerns of the community.
1.3 WASTEWATER BACKGROUND
Orient is currently served by individual subsurface wastewater disposal systems
(primarily cesspools) and is un-sewered. The proposed service areas for the future
wastewater system are comprised of 7 different areas and are shown on Figure 1.1.
SECTION 1 BACKGROUND
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 1-2
Figure 1.1 Proposed Service Area
Peconic Green Growth (PGG), a not-for-profit organization, has expended significant
effort on developing the wastewater system needs and scope. The proposed sewer
service areas shown on Figure 1.1 were developed by PGG.
1.3.1 Service Area and Flows
Preliminary mapping by PPG shows seven potential wastewater districts. The final
district boundaries and number of districts will most likely be adjusted based on public
feedback and technical analysis going forward. These districts range in size from 11 to
393 structures with estimated flows of between 2,100 and 72,582 gallons per day (gpd).
With the exception of one district (District 1), these are primarily residential areas.
District 1 contains the commercial center of the hamlet of Orient and therefore a higher
number of commercial and institutional properties. The table below provides the
characteristics and flows of each district upon which this proposal is based.
SECTION 1 BACKGROUND
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 1-3
Project Understanding – RFP District Characteristics
District Area (acres) Buildings Dwellings Flow (gpd)
1 169 393 230 72,582
2 64 57 48 19,996
3 43 63 44 13,500
4 58 72 48 14,400
5 15 11 7 2,100
6 56 63 51 15,300
7 110 144 144 43,200
1.3.2 Proposed Treatment System
PGG has indicated that the study should focus on alternative treatment technologies and
collection systems. This phase of study will focus on acceptable areas for subsurface
disposal.
1.4 PROJECT AREA CHARACTERISTICS
1.4.1 Location & Population
Orient is located at the very eastern end of Suffolk County on Long Island within the
Town of Southold. Orient comprised of approximately 6.1 square miles including
residential and commercial uses.
The population in the hamlet has increased by 4.8% from 2000 to 2010, from 709 to 743.
The summer population of the hamlet is estimated to be over 1,000.
1.4.2 Environmental Resources
Of the 6.1 square mile area, one square mile is water. The majority of this is Hallock Bay
(Long Beach Bay), but there are also many tidal streams (NYSDEC Class SA & SC
Saline Surface Waters) and wetlands. Many of the wetlands areas are designated as
either federal or NYS DEC wetlands. Both of these features are shown on Figure 1.2.
SECTION 1 BACKGROUND
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 1-4
Figure 1.2 Orient Hamlet Wetlands Source: GIS Data from Southampton
GIS Department
The hamlet is located on the Nassau-Suffolk sole source Aquifer. A sole source aquifer
is one that has been identified by the EPA as one which supplies at least fifty percent
(50%) of the drinking water consumed in the area overlying the aquifer.
Orient is considered a Water Supply Sensitive Area under 760-706 of the Suffolk County
Sanitary Code. This is defined by the code as a groundwater area separated from a larger
regional groundwater system where salty groundwater may occur within the Upper
Glacial aquifer. Discharge of industrial wastes in Waste Supply Sensitive Areas is
restricted.
Orient also contains two estuaries of national importance, the Long Island Sound and the
Peconic Estuary. An estuary is a partially enclosed body of water along the coast where
freshwater from rivers and streams meets and mixes with salt water from the ocean.
1.4.3 Flood Zones
The FEMA 100 year flood plain boundary is present in the proposed service area as well
as Sea, Lake and Overland Surges from Hurricanes (SLOSH) zones. SLOSH zones
indicate the areas of flooding that could be anticipated from category 1 – 4 storms. Both
of these features are shown on Figure 1.3.
SECTION 1 BACKGROUND
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 1-5
Figure 1.3 Orient Hamlet Floodplain & SLOSH Zones Source: PGG with support from
Southampton GIS Department
1.4.4 Geology/Topography/Soils
A soil map of the hamlet is shown in Figure 1.3. There are many soil types in and
around the hamlet, the most prominent being: Haven, Montauk, Plymouth, Raynham,
Riverhead, and Scio. A significant percentage of soils, approximately 15%, are classified
as beaches (Bc)or tidal marsh (Tm). The following descriptions are based upon the
USDA Natural Resources Conservation Service soil descriptions. Exact soil composition
and extents requires field confirmation.
HaA, HaB, HaC – Haven loam is very deep, moderately well drained soil formed in
glacial outwash plains. It consists of loamy glaciofluvial deposits over sandy and
gravelly glaciofluvial deposits. This soil belongs to Hydrologic Soil Group B. Slope
ranges from 0 to 12 percent.
MfB, MfC– Montauk fine sandy loam is somewhat shallow well drained soil formed in
glacial moraines. It consists of loamy till over firm sandy till derived from crystalline
rock. This soil belongs to Hydrologic Group B. Dense material is typically encountered
at 18 to 38 inches. Groundwater is typically encountered at 16 to 36 inches. Slope ranges
from 3 to 15 percent.
SECTION 1 BACKGROUND
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 1-6
Figure 1.3 Orient Hamlet Soils Source: GIS Data from Southampton GIS Department
PlB, PlC- Plymouth loamy sand is deep, excessively drained soil formed in glacial
outwash plains and moraines. It consists of acid sand glaciofluvial or deltaic deposits.
This soil belongsHA to Hydrologic Group A.
Ra – Raynham Loam is deep, somewhat poorly drained soil formed in glaciolacustrian,
eolian or old alluvial deposits comprised mainly of silt and fine sand. This soil belongs
to Hydrologic Group B – D. Depth to water table is typically 6 to 12 inches.
RdA, RdB, RdC, RhB – Riverhead sandy loam is deep, well drained soil formed in
glacial outwash plains and moraines. It consists of loamy glaciofluvial deposits
overlying stratified sand and gravel. This soil belongs to Hydrogeologicl Group A.
SdA, SdB – Scio silt loam is somewhat deep, moderately well drained soils formed in
lake plains. It consists of glaciolacustrian deposits, eolian deposits, or old alluvium,
comprised mainly of silt and very fine sand. This soil belongs to Hydrologic Group B/D.
Depth to water table is typically 18 to 24 inches.
Other than in areas of the North shore, topography is relatively level. Topography is
shown in Figure 1.5.
SECTION 1 BACKGROUND
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 1-7
Figure 1.5 Orient Hamlet Topography Source: US Geological Survey Topographical Maps
1.4.5 Groundwater
The depth to groundwater in the hamlet generally decreases from North to South as
shown in Figure 1.6.
Figure 1.6 Depth to groundwater Source: PGG with support from
Southampton GIS Department
SECTION 1 BACKGROUND
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 1-8
It is important to note that groundwater elevations provided in Figure 1.6 have been
modified to address impacts by septic system design, but regardless, show the general
trend of increasing depths.
1.4.6 Land Use/Zoning
Orient is within the Town of Southold. Southold’s zoning laws enable the Town to
regulate specific types of development. The zoning districts present in the hamlet are
described below:
Residential Low Density District (R40)
Several residential areas throughout Orient.
Minimum 1 acre lot
Residential Low Density District (R80)
Several residential areas throughout Orient.
Minimum two acre lot
Residential Low Density District (R200)
Area south of Route 25, eastern end of Orient.
Minimum lot size of 5 acres
Residential Low Density District (R400)
Orient Beach State Park
Minimum lot size of 10 acres
Hamlet Density Residential District (HD)
One lot north of Route 25, near Orient.
No specified minimum lot size
Resort Residential (RR)
One parcel on Main Street, near the center of Orient.
Zoning to provide opportunity for resort development in waterfront areas or other
appropriate areas
SECTION 1 BACKGROUND
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 1-9
Hamlet Business District (HB)
Parcels at the center of Orient.
Zoning to provide for business development in Orient central business areas
General Business District (B)
Parcels near the center of Orient.
Zoning to provide for retail and commercial business development
Marine I District (MI)
Two coastal parcels in the western portion of Orient.
Zoning to provide a waterfront location for water related uses on Town creeks and
coves
Marine II District (MII)
One coastal parcel in the eastern portion of Orient.
Zoning to provide a waterfront location for water related uses on major
waterways.
The Town zoning indicates that municipal uses are permitted by right in most areas,
except Hamlet Density Residential where the specific use is not indicated as in all other
areas. Figure 1.7 provides the zoning districts in and around the service area.
SECTION 1 BACKGROUND
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 1-10
Figure 1. 6 Orient Hamlet Zoning Source: Town of Southold Zoning Map
MI
RR
B
HD
HB
SECTION 2 WASTEWATER SYSTEM ALTERNATIVES
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 2-1
2.1 INDIVIDUAL DISPOSAL SYSTEMS
In many portions of Orient continued use of individual homeowner on-site systems may
be appropriate and cost-effective. For parcels in areas with low development density,
suitable soils, and a deep depth to groundwater may have conditions that can support
continued use of properly designed and constructed individual septic systems.
Smaller lots in areas with dense development would require alternative technologies to
provide an acceptable level of treatment to protect drinking water and environmental
quality. Several alternative treatment systems discussed in the upcoming Section 2.4 are
manufactured in sizes appropriate for use by individual homeowners. Please refer to
Section 2.4 for more information on these units.
Alternative treatment systems require mechanical equipment (blowers and/or pumps) in
order to operate effectively and, as a result, require more periodic maintenance than a
conventional septic system. Typically a licensed operator will need to perform annual or
biannual maintenance.
On parcels with very small, non-conforming lot sizes which have no remaining room for
an appropriate treatment or disposal areas, upgrades to septic systems will not be
effective in correcting current wastewater effluent quality deficiencies. Because
upgrades to individual septic systems alone are not expected to be sufficient for all of
Orient, other wastewater disposal improvements have been described in the following
sections.
2.2 WASTEWATER COLLECTION SYSTEMS
There are generally two different types of wastewater collection systems: conventional
and alternative.
2.2.1 Conventional Collection System
A conventional collection system consists of gravity piping, typically PVC, installed by
an open trench method. This involves removing paving or sod on the ground surface,
excavating to depths of 5 – 12 feet (typically, can be deeper) installing crushed stone
bedding, installing rigid PVC pipe, backfilling and repairing the disturbed surface.
Gravity piping must be installed carefully to maintain a constant downward slope.
Access for inspection and cleaning is by pre-cast concrete manholes. Generally the
smallest gravity main is 8-inches with a minimum slope of 0.4%.
Gravity systems are appropriate when there is sufficient grade to ensure required pipe
slopes. However, since maintaining slope is vital to these systems, open trench
construction is necessary. Open trench construction in shallow cross-country routes with
sufficient space and only requiring loaming and seeding for repair can be very cost
effective. Open trench construction through congested paved areas can have expensive
restoration costs.
If gravity collection systems do not allow for conveyance to the treatment site, gravity
piping will discharge to a pump station. Conventional pump stations typically consist of
SECTION 2 WASTEWATER SYSTEM ALTERNATIVES
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 2-2
a pre-cast concrete wet well with two submersible wastewater pumps. Pump stations
discharge to a smaller diameter forcemain. Minimum sanitary forcemain diameter is 4-
inches. Pumps must maintain a flow velocity of 2 fps. Sanitary forcemain must have
clean out structures every 400 – 500 feet and may require air release structures at high
points.
2.2.2 Alternative Collection Systems
A significant difference between conventional and alternative collection systems is the
use of septic tanks. Septic tanks are typically plastic or concrete tanks which detain raw
wastewater discharge from a building service. The tank is baffled which allows solids to
settle to the bottom of the tank, and floatable material to form a scum layer at the top of
the tank. Wastes in the tank are decomposed by aerobic digestion. Wastewater water
leaving the tank, septic tank effluent, is of improved quality as solids remain with the
septic tank. Septic tanks must be pumped regularly (typically every 3 – 7 years) or solids
will build up in the tank and discharge in the effluent.
Figure 2.1 Typical Septic Tank Source: NYS Department of Health
While conventional wastewater collection systems convey raw wastewater, alternative
collection systems typically convey septic tank effluent.
There are alternative gravity and pressure collection systems. Septic tank effluent gravity
(STEG) systems use small diameter gravity collector lines to convey septic tank effluent
to a treatment location. These gravity lines have a minimum diameter of 4-inches and no
minimum slope but typically have a minimum velocity of 0.5 fps. Gravity lines have the
SECTION 2 WASTEWATER SYSTEM ALTERNATIVES
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 2-3
advantage of not requiring any power to operate, and will continue to provide appropriate
wastewater service even in cases of electricity outages.
Low pressure sewers consist of smaller diameter force main through which sewer flow is
pumped. Septic tank effluent pumps (STEP) or grinder pumps force wastewater through
the main regardless of pipe slope. Low pressure sewers can be installed by conventional
open trench methods, but smaller diameter piping can also be installed by directional
drilling. Directional drilling utilizes exit and entry pits, and access for service
connections, but does not disturb the ground surface over the entire pipe length,
significantly reducing restoration costs. The minimum diameter for low pressure sewer
piping is 2-inches and there are no minimum slope requirements. Similar to conventional
sanitary forcemain, low pressure sewers must have regular clean out structures and may
require air release valves at high points.
2.3 WASTEWATER TREATMENT SYSTEMS
Consistent with collections systems, wastewater treatment systems can be divided into
two categories; conventional and alternative systems.
2.3.1 Conventional Treatment System Description
Many communities have ‘conventional’ treatment systems which generally consist of the
following components:
Primary treatment for the removal of solids
Secondary treatment which typically consists of biological treatment for the
removal of additional contaminates
Tertiary treatment for further removal of contaminants by biological, chemical or
physical means
Disinfection by chemical treatment or by UV light, and
Discharge to a surface water body or groundwater.
According to the 2012 Report on the Sewage Treatment Plants of Suffolk County, there
are 43 municipal plants, 34 of which are considered tertiary plants due to nitrogen
removal in their treatment processes. Of these municipal plants, 16 discharge to surface
waters.
The largest municipal operator is the Southwest Sewer District which operates 21
municipal treatment plants in Islip, Babylon and Huntington with sizes ranging from
0.035 to 30.5 million gallons per day (mgd).
SECTION 2 WASTEWATER SYSTEM ALTERNATIVES
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 2-4
Figure 2.2 Bergen Point WWTP, West Babylon, NY Source: Bing Maps
2.3.2 Alternative Treatment System
Alternative treatment systems typically include:
Use of individual septic tanks for solids removal and primary treatment,
Use of several treatment locations for one community,
Packaged modular secondary/tertiary biological treatment units located at a
regional locations near denser development/neighborhoods
Subsurface discharge
SECTION 2 WASTEWATER SYSTEM ALTERNATIVES
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 2-5
Figure 2.3 Alternative Treatment, Dix Hills, NY Source: Newsday
2.3.3 Treatment System Comparison
There are several differences between the two treatment plant types. Significant
differences include:
Sludge Management
Piping Costs
Operation & Maintenance
One of the most challenging aspects of a conventional wastewater treatment system is
solids handling. Conventional wastewater treatment systems typically consist of
screening for large solids removal, comminutors, large above ground settling basins to
remove the remaining solids, pumps to remove the collected solids, digesters to further
break down sludge or mechanical dewatering devices and then loading facilities for
trucking to conventional landfills. These components are generally expensive to build
and operate especially at a small scale.
With many alternative treatment systems, solids removal occurs at each parcel or a
combination of a few parcels. This allows typical residential septic tank pumpers and
haulers to handle solids removal and disposal. Typically the community is responsible
SECTION 2 WASTEWATER SYSTEM ALTERNATIVES
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 2-6
for all maintenance of septic tanks, ensuring that efficient solids removal is occurring.
However, this does require the community to obtain easements from the parcel owner to
be able to access and maintain the septic tanks. In Suffolk County there are several
wastewater treatment plants which accept wastewater from pumped septic tanks from
licensed septic haulers.
By removing solids before the wastewater is conveyed to a treatment location, a
wastewater collection system can be sized at a smaller diameter, lowering installation
costs. For instance gravity lines can be reduced to 4-inches where an 8-inch diameter is
normally required. Pressure lines can be reduced to 2-inches where 4-inches would
normally be required.
However, septic tank effluent systems that utilize pumping may be difficult to manage
during power outages. Frequently, a home with no municipal wastewater services has no
municipal water service either. Thus if a power outage occurs, the well is without power,
as well as the wastewater system pump. If a home has a generator, it typically will be
sized to accommodate the well pump, as well as the wastewater pump, also avoiding a
conflict. However, if a home with municipal water service, which typically remains
unaffected by power outage also, has septic wastewater pumps as part of an alternative
collection system, there may be a continued source of wastewater, with no means of
pumping. If a sustained power outage lasted for several days, the municipality would
need to pump each septic tank into the collection system. For a conventional collection
system, this would require simply providing emergency power at a central pump station,
rather than requiring service at many individual systems. Both conventional and
alternative systems that utilize gravity collection avoid these problems. All treatment
systems, conventional and alternative, require emergency power at the main treatment
location.
In general, conventional wastewater treatment facilities are treating higher flows, and
have more complex treatment systems due to on-site sludge management. For proper
operation, conventional wastewater treatment facilities require a full time licensed
operator and generally at least one other trained staff member. Alternative treatment
systems typically have smaller flows and simpler treatment systems, thus staff is usually
part time.
Due to Orient’s the rural nature, and the style of development which includes several
densely populated areas separated by large areas of much smaller population, further
consideration of decentralized treatment is appropriate. Additional information on
alternative treatment technologies has been presented in the following section.
2.4 ALTERNATIVE TREATMENT TECHNOLOGIES
An alternative treatment system accomplishes treatment in two locations; primary
treatment occurs in the on-site septic tanks, and secondary/tertiary treatment which
occurs at a site where all the flow has been collected.
SECTION 2 WASTEWATER SYSTEM ALTERNATIVES
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 2-7
Treatment efficiency for small systems is generally characterized by their efficiency at
removal of organic constituents and solids. The most commonly used parameter to
define the organic strength of municipal wastewater is biochemical oxygen demand
(BOD). BOD is the quantity of dissolved oxygen utilized by microorganisms in the
aerobic oxidation of the organic matter in wastewater over a period of time. The
depletion of dissolved oxygen in wastewater is directly related to the amount of organic
matter present in the wastewater.
The quantity of solids in wastewater is typically expressed as total suspended solids
(TSS). Suspended solids are those removable by filtration of settling. Wastewater may
also have quantities of dissolved solids, which require additional treatment for removal.
Another parameter used to gauge the strength of wastewater is nitrogen. Common forms
of nitrogen are ammonia, nitrite, and nitrate. Nitrogen is used by plants for
photosynthesis, and is an important component in fertilizer. Large quantities of nitrogen
in wastewater discharged to a water body can cause growth of algae. Ammonia is
considered a serious water pollutant as it is toxic to fish. Nitrate can easily pass through
the soil to the groundwater, where it can accumulate to high levels over time, potentially
contaminating drinking water sources. Typically a permit for subsurface wastewater
discharge will have limitations set on ammonia (NH3). Typical individual disposal
system absorption fields remove little or no nitrogen from the septic tank effluent.
Primary treatment by septic tank is effective at removing quantities of BOD and TSS and
some nitrogen species. Table 2.1 below provides typical septic tank influent and effluent
concentrations.
Table 2.1
Septic Tank Influent & Effluent Concentrations
Parameter Influent
Concentration
Effluent
Concentration
BOD 350 mg/l 150 mg/l
TSS 400 mg/l 40 mg/l
NH3-N 70 mg/l 50 mg/l
FOG 150 mg/l 20 mg/l
There are many suitable technologies available for wastewater treatment. However there
are minimum criteria that each system must meet:
Ability to meet regulatory effluent limits
Suffolk County Department of Health Services familiarity with the system
Suffolk County has formally evaluated many innovation/alternative onsite sewage
disposal system capable of denitrification, ranging from individual home systems to small
plants with capacities of 30,000 gpd (approximately 100 homes). A summary of their
evaluation is included in Appendix A. The following systems are approved for use in
Suffolk County.
Advantex by Orenco followed by Nitrex
SECTION 2 WASTEWATER SYSTEM ALTERNATIVES
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 2-8
BESST by Purestream
Bioclere by Aquapoint
Commercial Treatment Unit by Waterloo Biofilter followed by Nitrex
Cromaglass SBR Systems
SeptiTech Commercial Unit followed by Lombardo Assc. Nitrex
STM Aerotor by WesTech
Further phases of this study will evaluate the available technologies and recommend
which may best meet the needs of the hamlet.
2.5 WASTEWATER DISPOSAL SYSTEMS
Several alternatives exist for disposal of the treated wastewater effluent to the ground
water;
Seepage Pits/Subsurface Leaching Pools
Open Recharge Beds
Absorption Beds and Fields
Shallow Narrow Drainfields
Subsurface Drip Irrigation
2.5.1 Seepage Pits
The most common form of wastewater disposal in the hamlet is seepage pits. Seepage
pits are typically used in Suffolk County as they are the smallest foot print of available
wastewater disposal systems. Large portions of the hamlet also have a significant depth to
groundwater, which is required for seepage pit usage. Groundwater depths are provided
in Figure 1.6 in the previous Section. Seepage pits are perforated circular concrete
structures which receive septic tank effluent. If sufficient distance between the seepage
pit and groundwater exists, then microorganisms in the soil sufficiently treat wastewater
effluent before it enters the groundwater. According to the Suffolk County Department
of Public Works/Cornell Cooperative Extension of Suffolk County Stormwater
Management Program failing seepage pits are the primary cause of nitrate contamination
in the groundwater in high density residential areas.
SECTION 2 WASTEWATER SYSTEM ALTERNATIVES
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 2-9
Figure 2.2 Seepage Pit Source: NYS Department of Health
Seepage pits are also indicated as acceptable by the Suffolk County Department of Public
Works Division of Sanitation’s Standards for Recharge of WWTP effluent as part of
shallow and deep subsurface disposal methodologies.
2.5.2 Open Recharge Beds
Open recharge beds are included in the Suffolk County Department of Health Services –
Appendix B “Standards for Approval and Construction of Sewage Collection System and
Treatment Works” and noted in the Suffolk County Department of Public Works
Division of Sanitation’s Standards for Recharge of WWTP effluent as the preferred
methodology. However utilization of this disposal method has been a contentious and
arduous process for other facilities in Suffolk County, such as the propped usage on the
SUNY Stony Brook Campus. The setbacks for these facilities are significant; 400’ to
buildings and 300’ to property lines. There is poor public perception of these facilities in
regard to the potential for odors and visual impact from the exposed pool of wastewater.
2.5.3 Absorption Fields and Beds
An alternative method for subsurface disposal is through the use of absorption fields or
beds. Wastewater effluent is discharged by gravity or pressure into buried perforated
PVC pipes which are surrounded by gravel. Absorption fields or beds are used to treat
wastewater similarly to seepage pits, except the closer proximity to the ground surface
SECTION 2 WASTEWATER SYSTEM ALTERNATIVES
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 2-10
makes the system more aerobic, and the wastewater is dispersed over a much larger soil
surface area.
Figure 2.3 Absorption Field Source: NYS Department of Health
2.5.4 Absorption Fields and Beds
When any of the previously discussed absorption methodologies are used after secondary
treatment, they are primarily intended for discharge of the treated effluent into the
groundwater. However, there a dispersal method heavily researched by the University of
Rhode Island and the Rhode Island Department of Environmental Management, Shallow
Narrow Drainfields (SND), have been shown to effectively reduce nitrogen in effluent.
SNDs have been studied in coastal regions of Rhode Island to evaluate their nitrogen
reduction capabilities. This is important, as Rhode Island’s coastal areas were formed
geologically in the same fashion as long island, and typically have the same progressions
of sandy areas, sandy loam, loam and silt loam. Additional information on SNDs is
provided in Appendix B. In general, a 33% - 73% reduction in nitrogen is anticipated
utilizing the SND.
SECTION 2 WASTEWATER SYSTEM ALTERNATIVES
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 2-11
Figure 2.4 Shallow Narrow Drainfield Cross Section Source: RI Dept. of
Env. Management
2.5.5 Irrigation Wastewater Reuse
Another potential methodology for disposing of treated wastewater effluent is subsurface
drip irrigation. Subsurface drip irrigation technologies apply water to the root zone using
perforated small diameter piping or porous diffusers, placed 6 to 12 inches below the soil
surface.
Disposal of recycled water through subsurface drip irrigation will provide a valuable
source of nitrogen for nursery stock, and an efficient water reuse method. Once the needs
of the facility are better determined, a design could be completed that utilizes this
appropriate technology.
Additionally, reclaimed wastewater can be utilized for spray or surface drip applications.
Treatment would need to include UV disinfection.
SECTION 2 WASTEWATER SYSTEM ALTERNATIVES
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 2-12
Figure 3.7 Drip Irrigation System Source: Geoflow, Inc.
2.6 WASTEWATER DISPOSAL QUALITY
Based upon data from the Suffolk County Department of Health, and the NYS Code of
Regulations Part 703: Surface Water and Groundwater Effluent Limitations for
community systems, the following discharge limits are presumed:
Table 2.2
Effluent Characteristics
Wastewater Component Effluent
BOD5 < 30 mg/l
TSS < 30 mg/l
TDS 1,000 mg/l
pH 6.5 – 8.5
Nitrogen < 10 mg/l
SECTION 3 TREATMENT SITE IDENTIFICATION
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 3-1
3.1 TREATMENT SYSTEM SITING CONSTRAINTS
Determining the correct siting for a wastewater treatment facility is challenging, however
the use of alternative treatment technologies, with their low visual, audio and odor
impact, allow for a much greater number of sites to be considered. Preliminary potential
sites were identified by preliminary map review using the criteria provided in Table 3.1.
Table 3.1
Treatment Site Initial Screening
Criteria Initial Screening
Vacant parcels with usable land less than 3 acres Excluded
Occupied Parcels with less than 5 acres Excluded. Assumes 5 acres needed to
buffer existing house lot
100 year flood plains and SLOSH areas Excluded
State and Federal Wetlands Excluded
Streams, wetlands or protected water bodies Excluded areas within 100’
Steeply sloped areas (>15%) Excluded
Mapping showing each of the application of these criteria is found in Figure 3.1.
SECTION 3 TREATMENT SITE IDENTIFICATION
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 3-2
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SECTION 3 TREATMENT SITE IDENTIFICATION
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 3-3
Based upon the parcels eliminated by the criteria presented in Table 3.1, twenty sites
acceptable for wastewater treatment, based upon land review only, were determined and
are presented on Table 3.2, from West to East.
Table 3.2
Potential Wastewater Treatment Sites
Parcel
# Tax Map #
Property
Owner
Property
Location Acres Comment
1 2500.400.11009 Morton
Orchard
St. 13.5
Nursery in Ag district,
parcel in SLOSH, may
have subdivision plans
2 2700.100.2003 Guadagno
Orchard
St. 6.0
Farmed field in Ag.
District, small portion of
parcel in SLOSH, may
have subdivision plans
3 1800.200.23001
Oysterponds
School District Route 25 12.9
School playing fields
behind school building
4 1800.200.33000 C&P Healy Corp Route 25 8.0 One large structure
5 1800.200.34000 Boyle Route 25 22.3 Several large structures
6 1800.600.4001 Latham
Platt
Road 11.7
Ag District, garage,
farmed fields, portion of
parcel in SLOSH
7 1800.600.5002 Apostle Trust Route 25 4.2
Ag District, farmed fields,
Suffolk County owns
development rights
8 1800.600.5003 Apostle Trust Route 25 3.1
Ag District, farmed fields,
Suffolk County owns
development rights
9 1800.600.14009
Khedouri Ezair
Corp. Route 25 62.4
Ag District, farmed/fallow
fields, southern half of
parcel in SLOSH, Town of
Southold owns
development rights
10 1800.300.9009 Caslenova Route 25 11.3
Ag District, farmed/fallow
fields, Suffolk County
owns development rights
11 1800.300.30003 N. Brown LLC Route 25 28.5 Ag District, farmed fields
12 1800.400.1003
Oysterponds
Corp. Route 25 16.8
Ag District, farmed fields,
Peconic Land Trust
Preservation Easement
13 1800.400.7007
Sepenoski
Family Farm
LLC Route 25 18.8
Ag District, farmed fields,
Town of Southold owns
development rights
14 1300.200.8002 Benjamin
Heath
Drive 22.8 Ag District, farmed fields
15 1400.200.29003 Orient West LLC Old Road 8.7
Farmed field, southern
portion of parcel in SLOSH
16 1400.200.29004 Orient Point LLC Old Road 4.6
Farmed field with barn,
southern portion of parcel
in SLOSH
SECTION 3 TREATMENT SITE IDENTIFICATION
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 3-4
Table 3.2 (cont.)
Potential Wastewater Treatment Sites
Parcel
# Tax Map #
Property
Owner
Property
Location Acres Comment
17 1900.200.12002 Orient East LLC Old Road 16.8
Fallow field, landing strip,
southern portion of parcel
in SLOSH
18 2000.100.2002 Whitsit
Terry
Lane 19.2
Ag District, farmed fields,
portion of parcel in
SLOSH, Protected Town
of Southold open space
19 2000.100.3007 Egan Route 25 30.6
Ag District, farmed fields,
wooded area, portion of
parcel in SLOSH,
Protected Town of
Southold open space
20 1500.200.17006
Amelias Sound
Properties Inc. Route 25 32.3
Fallow field, southern
portion of parcel in SLOSH
These sites are shown on Figure 3.2.
Figure 3.2 Potential Wastewater Treatment Sites
SECTION 3 TREATMENT SITE IDENTIFICATION
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 3-5
3.2 PRELIMINARY PARCEL SCREENING
After the parcels identified by the matrix constraints were determined, additional review
of the parcels was completed. Based upon more detailed review of land use and other
constraints, additional parcels were excluded from further review.
The most common cause for exclusion was active farming of food crops. Food crops are
annual planting which require plowing and replanting every year. This would be a high
potential for disturbance of any wastewater disposal system. Also, utilizing wastewater
for irrigation of edible products requires additional treatment including filtration and
disinfection which would significantly impact treatment costs.
Table 3.3
Preliminary Wastewater Treatment Site Screening
Parcel
#
Property
Owner Comment Action
1 Morton
Nursery use may be compatible with wastewater
disposal, parcel in Ag. District, 4.8 acres of parcel in
SLOSH leaving 8.7 acres.
Include in
further study
2 Guadagno
Fallow field or pasture Ag. District, <0.5 acre parcel in
SLOSH leaving 5.5 acres available for disposal, Ag
district requirements must be adhered to
Include in
further study
3
Oysterponds
School
District
Elementary School playing fields behind school building,
wastewater disposal in playing field is compatible use.
Advantage of not being in Ag. District.
Include in
further study
4
C&P Healy
Corp This parcel appears to be a horse farm.
Include in
further study
5 Boyle This parcel appears to be a horse farm.
Include in
further study
6 Latham This parcel appears to be a vegetable farm.
Exclude from
further analysis
7
Apostle
Trust This parcel appears to be a berry farm.
Exclude from
further analysis
8
Apostle
Trust This parcel appears to be a berry farm
Exclude from
further analysis
9
Khedouri
Ezair Corp.
Over 20 acres are not in SLOSH. Town development
rights.
Include in
further study
10 Caslenova Ag District, County development rights.
Include in
further study
11
N. Brown
LLC
The southern portion of this is a plowed farm field.
Plowing would be incompatible with effluent disposal.
The northern portion of this parcel is mature trees.
Exclude from
further analysis
12
Oysterponds
Corp.
This parcel is a plowed farm field. Plowing is
incompatible with effluent disposal.
Exclude from
further analysis
13
Sepenoski
Family Farm
LLC
This parcel is a plowed farm field. Plowing is
incompatible with effluent disposal.
Exclude from
further analysis
14 Benjamin This parcel appears to be a vineyard.
Exclude from
further analysis
15
Orient West
LLC
This parcel is a plowed farm field. Plowing is
incompatible with effluent disposal.
Exclude from
further analysis
SECTION 3 TREATMENT SITE IDENTIFICATION
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 3-6
16
Orient Point
LLC
This parcel appears to be a fallow field. If no longer
used regularly for agriculture, maybe available for
disposal. This parcel is not in the Ag. District.
Include in
further study
17
Orient East
LLC
This parcel appears to contain brush to mature trees.
This parcel is not in the Ag. District.
Include in
further study
18 Whitsit
Parcel is a plowed field in the Ag. District, Town
protected open space.
Exclude from
further analysis
19 Egan
The southern portion of this is a plowed farm field in
SLOSH zone. The northern portion is mature trees.
Town protected open space.
Exclude from
further analysis
20
Amelias
Sound
Properties Fallow field with southern portion in SLOSH.
Include in
further study
As provided in the Suffolk County Department of Health Services – Appendix B
“Standards for Approval and Construction of Sewage Collection System and Treatment
Works”, the following assumptions were made in regard to the treated wastewater
effluent disposal:
- 2.3 gpd/sq ft application rate. Per Suffolk County guidance a 5 gpd/sq ft application
rate is permissible (10 gpd/sqft is permitted with filtered wastewater), but without
detailed treatment process analysis, we are recommending use of a use more
conservative number)
- a 100% reserve/expansion area
- a minimum 25’ setback to property lines
- a minimum 100’ setback to surface waters or wetlands
- a minimum 200’ setback from surrounding wells (assumed 200’ from property line
on small adjacent parcels and assumed to be in general area of building on large
buildings on adjacent parcels)
- A field efficiency of 30% was assumed. This means that of the available area, it was
assumed that 30% was actually used as disposal area, and the remaining was
separation between disposal practices, areas where manifold piping was, and other
spacing.
Table 3.3 provides the estimated wastewater disposal capability of each parcel.
Table 3.4
Preliminary Wastewater Disposal Capacity
Parcel
ID
Total
Area
(acres)
Useable
Area
(acres)
Field
Area
(acres)
Absorption
Area (sf)
Disposal
Capacity
(gpd)
1 13.5 0.70 0.35 4,590 10,557
2 6 3.72 1.86 24,300 55,890
SECTION 3 TREATMENT SITE IDENTIFICATION
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 3-7
3 12.9 2.11 1.06 13,800 31,740
4 8 4.41 2.20 28,800 66,240
5 22.3 9.11 4.56 59,550 136,965
9 62.4 17.93 8.96 117,150 269,445
10 11.3 3.97 1.99 25,950 59,685
16 4.6 1.49 0.75 9,750 22,425
17 16.8 2.55 1.27 16,650 38,295
20 32.3 4.06 2.03 26,550 61,065
Each of the considered parcels is presented in the following Figures 3.3 – 3.9.
Figure 3.3 –Parcels 1 & 2
SECTION 3 TREATMENT SITE IDENTIFICATION
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 3-8
Figure 3.4 Parcels 3, 4 & 5
SECTION 3 TREATMENT SITE IDENTIFICATION
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 3-9
Figure 3.5 – Parcel 9
Figure 3.6 – Parcel 10
SECTION 3 TREATMENT SITE IDENTIFICATION
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 3-10
Figure 3.7 – Parcel 16 & 17
Figure 3.8 – Parcel 20
SECTION 3 TREATMENT SITE IDENTIFICATION
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 3-11
3.3 ADDITIONAL PARCEL CONSIDERATIONS
There are restrictions of working on certain types of properties, especially those classified
as parks or agricultural districts. These restrictions are described below:
3.3.1 Park Land
As explained in the New York State Office of Parks, Recreation and Historic
Preservation’s Handbook on the Alienation and Conversion of Municipal Parkland in
New York, “Once land has been dedicated to use as a park, it cannot be diverted for uses
other than recreation, in whole or in part, temporarily or permanently, even for another
public purpose, without legislative approval.” The handbook specifically recommends
that municipality should obtain alienation legislation for “The granting of temporary or
permanent easements for the installation of underground facilities such as water and
sewer pipelines even when the surface of the land will be restored and continue to be
used for park and recreational purposes”. The New York State Legislature routinely
passes underground easement related alienation bills, and this fact would give a court a
basis for finding such an easement to be an alienation. The New York State Attorney
General’s Office has the ability to bring action against a municipality that does not comply
with proper legislative procedures.
Legal counsel should be sought to advise on this matter.
3.3.2 Agricultural Districts
Parcels located within Agricultural District No. 1 must comply with Agriculture and
Markets Law Section 305, Subdivision 4 as required by 1 NYCRR Part 371. These
regulations specify that a preliminary and final notice of intent must be filed with the
Commissioner of Agriculture and Markets of NYS and county agricultural and farmland
protection board before initiating an action, with “action” specifically defined as “The
construction by a State agency, public benefit corporation or local government, within an
agricultural district, of dwellings, commercial or industrial facilities, or water or sewer
facilities to serve non-farm structures.” The notice of intent contents include important
information about the parcel in the agricultural district and the proposed usage which is
specifically identified in Part 371. It must be filed at least 65 days before any action is
commenced. The Commissioner will determine if alternatives are available that avoid
impacts to the farmland and can propose alternative actions. It is also possible for the
Owner of the parcel to sign a document waiving the requirement for notice of intent filing
which provides the commissioner the name of the purchasing parties, the address and
specifically states the intent of the waiver. It is recommended that legal counsel research
the required steps needed to use a portion of a parcel in an Agricultural District for
wastewater treatment and disposal.
SECTION 3 TREATMENT SITE IDENTIFICATION
Peconic Green Growth LLC – Orient Wastewater Feasibility Report – Phase 1 3-12
3.3.3 Development Rights
In a purchase of development rights program, a landowner voluntarily sells the parcels
development rights to a governmental agency or land trust. In the case of farmland, the
agency typically pays the farmer the difference between the agricultural value of the land,
and the land’s potential development value. When the property is sold, an easement
which restricts the use of the land for agricultural uses incorporated in the title. Private
ownership of the parcel is maintained.
There are several parcels where development rights of the parcel have been purchased by
the Town or County. Easements on development rights are not consistent from parcel to
parcel, but most easements limit use of property to agricultural production. While
certainly it seems that some form of agricultural production could be maintained while
also using the property for wastewater disposal, it is likely to be a challenging process to
utilize parcels with development right easements for wastewater disposal purposes.
These parcels include: parcel #9, Khedouri Ezair Corp., and parcel #10, Caslenova.
While these parcels have been included on the list for further study, legal review of the
specifics of the easements for these two parcels should be completed to determine siting
feasibility.
SECTION 4 PROJECT ADVANCEMENT
PGG – Hamlet of Orient – Wastewater Feasibility Report - Phase 1 4-1
4.1 ADDITIONAL STUDY PHASES
To complete the Wastewater Feasibility Report, the following additional phases are
recommended.
4.1.1 Treatment Site Identification
The effort to identify appropriate treatment sites should continue with onsite soils review
of each of the feasible sites needs to be completed to confirm the NRCS soil data. A
biologist may need to complete the wetlands delineation.
4.1.2 Collection and Treatment Alternative Evaluation
In concert with continuing to refine acceptable treatment sites, a complete analysis on the
collection and treatment methodologies presented in this report needs to be completed
and a preferred treatment alternative identified. The analysis should be based upon costs,
regulatory compliance, and appropriateness for the community and expandability. As
there are significant difference in space requirements, identifying the preferred
technology will impact capacity of feasible disposal parcels, thus both aspects need to be
considered together.
4.1.3 System Recommendations
Combining the results of the parcel identification, and the collection and treatment
system analysis a comprehensive wastewater approach for the 7 districts should be
completed, and project phasing should be recommended.
4.1.4 Costs & Funding
The engineering report should include:
An estimate of probable construction and operation and maintenance costs for the
recommended alternative.
An estimate of sewer use rates for each parcel using the Equivalent Dwelling Unit
(EDU) methodology.
The funding required to reach the maximum rate of $500 per EDU will be
calculated.
4.1.5 Implementation
The report should present any additional tasks that will need to be completed before
design could begin. These could include: regulatory agency concurrence, wetlands
delineation, additional subsurface exploration, easement procurement, and SEQR
preparation and submission.
SECTION 5 REFERENCES
PGG – Hamlet of Orient – Wastewater Feasibility Report - Phase 1 5-1
Standards for Approval of Plans and Construction for Sewage Disposal Systems for
Other than Single-Family Residences, Suffolk County Department of Health Services
Division of Environmental Quality, 2008.
Alternative On-Site Sewage Disposal Systems, Task IX – Summary Report, Suffolk
County, New York Department of Health Services, Office of Wastewater Management,
2013.
Rhode Island Department of Environmental Management, Guidelines fo rhte Design and
Use of Sand Filters and Pressureized Shallow-Narrow Drainfields, 2010.
Season Variation in Nitrogen Leaching from Shallow-Narrow Drainfields, Holden et. al.,
2004.
Design Standards for Intermediate-Sized Wastewater Treatment Systems, New York
State Department of Environmental Conservation, 2012.
Individual Residential Wastewater Treatment Systems Design Handbook, New York
State Department of Health, 1996.
Recommended Standards for Wastewater Facilities, Great Lakes-Upper Mississippi River
Board of State and Provincial Public Health and Environmental Managers, 2004 Edition.
Suffolk County Sanitary Coe Standards, Suffolk County Department of Health Services,
November 2011.
Suffolk County Comprehensive Water Resources Management Plan, CDM et. al, August
2010.
Sewage Treatment Plants in Suffolk County: Case Studies, Stony Brook State University
of New York, Long Island Groundwater Research Institute, 2011.
G:\Projects\3941302\Documents\Report\WW Feasibility Study 12-23-2013.docx
APPENDIX A
ALTERNATIVE ON-SITE SEWAGE DISPOSAL SYSTEMS –
EXECUTIVE SUMMARY
SUFFOLK COUNTY, NEW YORK
DEPARTMENT OF HEALTH SERVICES
OFFICE OF WASTEWATER MANAGEMENT
ALTERNATIVE ON-SITE SEWAGE DISPOSAL SYSTEMS
TASK IX –SUMMARY REPORT
H2M Project No.: SCHS 09-01
Draft: August 2012
Final: February 2013
Prepared by:
Holzmacher, McLendon & Murrell, P.C.
Division of Wastewater Engineering
175 Pinelawn Road, Suite 308
Melville, New York 1174 7
SUFFOLK COUNTY DEPARTMENT OF HEALTH SERVICES
OFFICE OF WASTEWATER MANAGEMENT
TASK IX – SUFFOLK COUNTY DEPARTMENT OF HEALTH SERVICES ALTERNATIVE
ON-SITE SEWAGE DISPOSAL SYSTEMS STUDY SUMMARY REPORT
3
H2M architects + engineers
EXECUTIVE SUMMARY
The Suffolk County Department of Health Services (SCDHS) retained the services of Holzmacher,
McLendon and Murrell, P.C. (H2M) to determine the feasibility of instituting alternative on-site
wastewater treatment systems into decentralized sewered communities or in single family residential
properties that could better manage total nitrogen discharged to groundwater. The project objective, as
stated in the County’s Request for Proposal, is to investigate the performance, installation and design
costs, economic benefits, and operation and maintenance requirements for alternative on-site sewage
disposal systems for projects generating a flow less than 30,000 gpd. The investigation was broken down
into two different treatment categories. The first category was defined as single-family residential
dwellings with flows from 300 to 1,000 gallons per day (GPD); the second category was defined as other
than single-family comprised of commercial, industrial, or high-density residential properties, with flows
from 1,000 GPD to 30,000 GPD. For the purposes of this report, the first flow category will be referred to
as residential applications, while the second flow category will be referred to as commercial applications.
The investigation was broken down into the following nine (9) tasks composed of reports and progress
meetings with the Department.
Task I, III, V, VI – Progress meetings to discuss previously submitted Task Reports
Task II – Review of Standards, Codes, and Regulations for On-Site System Technologies
Task IV A and B – Selection, Sampling, and Evaluation of AOSSDS
Task IV C – System Assessment and Acceptance using SCDHS Requirements
Task VI – Cost and Benefit Analysis
Task VIII – Evaluations of Conditions and Restrictions Under Which AOSSDS are Permitted for
use in Massachusetts, Rhode Island, New Jersey, and Maryland
Task IX – Study Summary, Findings and Recommendations
Overall study conclusions and recommendations for the individual residential applications:
The NitrexTM System was the only on-site treatment system that consistently met the 10 mg/l total
nitrogen discharge requirement.
Suffolk County currently utilizes the practice of limiting the building density in order to protect
both the drinking and surface water supplies in addition to conventional sanitary systems.
At this point in time, further study and modeling are necessary to determine if additional nitrogen
controls are required and to what extent. This companion study is currently in the planning stage.
There are numerous policy concerns with the proposed use of treatment systems for individual
residences. These deal not only with potential public health nuisances, but also with various
SUFFOLK COUNTY DEPARTMENT OF HEALTH SERVICES
OFFICE OF WASTEWATER MANAGEMENT
TASK IX – SUFFOLK COUNTY DEPARTMENT OF HEALTH SERVICES ALTERNATIVE
ON-SITE SEWAGE DISPOSAL SYSTEMS STUDY SUMMARY REPORT
4
H2M architects + engineers
social and economic concerns that transcend the purview of Department of Environmental
Quality (DEQ) – especially since the goal is generally surface water protection, rather than
strictly public health and drinking water.
Ultimately, once DEQ is able to provide facts grounded in science, issues can be fully vetted by
policymakers in an informed manner to support a reasoned and systematic regional approach to
treatment on individual residences, with the goal of garnering public support and implementation
funding.
Overall study conclusion and recommendations for commercial projects:
The NitrexTM System, Aqua Point – Bioclere®, WesTech’s STM-AerotorsTM, and BESST
technologies were added to the list of technologies that the Department would approve.
Cromaglass, SBR, and MBR technologies are currently approvable technologies.
For larger communal systems (i.e. commercial property or small housing clusters), the owners
could propose to install an alternative system as a demonstration system providing that the project
is within the sanitary density permitted under Article 6 of the Suffolk County Sanitary Code and
that the proposed system is in conformance with separation distances as specified in Appendix A
of the Commercial Standards.
APPENDIX B
PRESSURIZED SHALLOW NARROW DRAINFIELDS
SEASONAL VARIATION IN NITROGEN LEACHING FROM SHALLOW-
NARROW DRAINFIELDS
S.A. Holden1, M.H. Stolt2, G.W. Loomis3, and A.J. Gold4
ABSTRACT
Nitrogen removal from septic tank effluent is one of the most pressing issues in coastal areas
undergoing growth and development. Seven home-sites using onsite wastewater treatment
systems were monitored in coastal Rhode Island to examine N treatment and leaching. The
primary treatment units at these sites include: geo-textile filters; recirculating sand filters; single
pass sand filters; a fixed activated sludge treatment system; and a modular peat filter. The final
treatment step of all of these systems is a pressure-dosed shallow-narrow drainfield (SND). This
paper focuses on N-removal by the SND serving these sites (treatment performance of the
secondary treatment units will be delivered in a separate paper). Sites vary in age from four to six
years. Five suction-cup lysimeters were installed at each site, three within the SND and two
within a control plot (i.e., outside the drainfield area). In the SND, lysimeters were installed in the
undisturbed soils adjacent to each trench at a depth of 30 cm below the drainfield lines. Control
lysimeters were placed at 70 cm below the soil surface. Soil porewater samples were collected
through the lysimeters twice seasonally from the winter of 2001 until the summer of 2003 and
analyzed for total N. Average concentrations of N entering the groundwater for these seven sites
ranged from 2 to 41 mg/L (ppm). Six of the seven sites showed a 33 to 73% overall reduction in
N levels as a result of treatment in the SND. Seasonal effects were recognized for inputs of N into
the groundwater for two of the sites. There were no observed seasonal effects on the amount that
N levels were reduced as a result of treatment in the SND. Porewater samples collected from the
control area of two sites had considerably higher levels of total nitrogen (TN) than those below
the SND. The higher N levels outside the SND are likely the result of excess fertilizer additions to
the lawns.
KEYWORDS. Alternative onsite wastewater treatment, Nitrogen reduction, Shallow-narrow
drainfield, Low pressure distribution.
INTRODUCTION
The major pollutants to ground and surface waters from onsite wastewater disposal systems
(OSWDS) are N, P, and pathogens (Reneau et al., 1989). Nitrogen is generally considered the
most mobile of the three, thus assessment of N concentrations in pore and groundwaters below
an OSWDS can be used to estimate the potential for pollution from the system (Loomis, 1999).
The main sources of N in domestic wastewater are feces, urine, food, and chemical wastes
(Siegrist and Jenssen, 1989). The N found in wastewater is mostly organic nitrogen (NH3-R),
nitrate (NO3-), nitrite (NO2-), ammonium (NH4+), and nitrogen gas (Burks and Minnis, 1994).
Under aerobic conditions organic nitrogen and ammonium (the most abundant forms of N) are
oxidized to nitrate (Walker et al, 1973; Lance, 1975). Nitrate is not adsorbed to the negatively
charged soil particles, therefore it leaches easily, and may reach the groundwater resulting in
contaminated drinking water and eutrophication of surrounding coastal waters (Stolt and Reneau,
1991; Peterson and Simpson, 1992; Burks and Minnis, 1994; Brady and Weil, 2002; Loomis et
al., 2001). Most OSWDS rely on denitrification to convert nitrate to N2 gas, which is then
released to the atmosphere (Siegrist and Jenssen, 1989; Reneau et al., 1989; Stolt and Reneau,
1 Steven A. Holden, Graduate Assistant, Natural Resources Science, University of Rhode Island
2 Mark H. Stolt, Associate Professor, Natural Resources Science, University of Rhode Island
3 George W. Loomis, Research and Extension Soil Scientist and Director of Onsite Wastewater Training Center,
University of Rhode Island
4 Art J. Gold, Professor and Cooperative Extension Water Quality Program Leader, University of Rhode Island
1991). In order for denitrification to occur certain conditions; such as an available carbon
source, anaerobic conditions, and a favorable soil temperature and pH (Brady and Weil, 2002);
must exist. Conventional OSWDS, however, are designed for aerobic treatment of effluent and
will remove little N through denitrification.
Numerous studies have focused on the effectiveness of alternative OSWDS to remove N from
domestic wastewater (Stolt and Reneau, 1991; Peterson and Simpson, 1992; Loomis et al.,
2001). Most of these studies have focused on the effectiveness of secondary treatment units,
such as sand filters and aeration treatment units, to remove N and have not evaluated final
treatment of the wastewater. One commonly used final treatment step used for alternative
systems is a shallow narrow drainfield (SND), sometimes referred to as a low pressure
distribution system (Carlisle, 1980; Simon and Reneau, 1985; Stewart and Reneau, 1988). A
SND consists of a series drainfield lines, placed 25-45 cm below the soil surface, that are
pressure dosed with effluent from a secondary treatment unit. The SND offers many potential
advantages over a conventional drainfield. By being closer to the surface, a SND creates a larger
aerobic treatment zone for the effluent before it reaches the ground water or a limiting layer.
Another advantage is that the system is pressure dosed and will disperse the effluent equally over
the drainfield preventing overloading. Microbial and root biomass greatly decreases at a depth
below 50 cm (Brady and Weil, 2002), thus by having the drainfield lines in the upper 25 to 45
cm of soil the effluent is released in a zone where roots and soil microbes are most active
(Stewart and Reneau, 1988). This allows for the increased uptake and transformation of N in the
wastewater. The objectives of this study were to examine the amount of N potentially entering
the groundwater below SND in Rhode Island and to determine if time of year affects the
groundwater inputs. Our hypothesis was that reduced biological activity would occur in the
SND during winter and late fall and result in an increase in the amount of N entering the
groundwater from these systems. We assumed that soil porewaters collected 30 cm below the
SND lines would represent N concentrations entering the shallow groundwater in these coastal
settings.
METHODOLOGY
Seven home-sites located in coastal resource areas of Rhode Island were chosen for study. The
sites vary in the type of secondary treatment, age (four to six years old), placement of the
drainfield lines, and loading rates (Table 1). Each site has a SND as the final treatment step for
waste disposal.
Ceramic cup lysimeters were installed at each site: three directly adjacent to the trenches in the SND and
two in a control area. A push probe (diameter equal to lysimeter) was used to install the lysimeters and
reduce disturbance of the natural soil during installation. The base of the lysimeters was located 30 cm
below the trench bottom (depth was measured from the middle of the ceramic cup). Lysimeters within
the control were placed 70 cm below the soil surface at all the sites. The top of each lysimeter was 5-10
cm below the soil surface. A bucket auger (10 cm diameter) was used to excavate a space to allow
access to the lysimeter. These access ports were stabilized with an appropriate sized section of PVC
pipe. The PVC pipe was sealed with a #11 rubber stopper or a plastic cover. A screened PVC well was
placed 90 cm from the outside of the SND at a depth of 60 cm below the trench bottom to monitor the
water table level at each site. The purpose of the well was to confirm that the water table was not
approaching the treatment zone of the SND and that we were collecting porewater samples (i.e. not
collecting samples below the water table). Redox potential was measured at selected sites using six
redox probes (electrodes) inserted along the drainfield to a depth equal to the trench bottom. Potentials
were also measured at the same depth in the control area. Values were corrected by adding the standard
potential of a saturated calomel reference electrode at a pH = 7 (244 mV). The soil redox potential
measurements were made to determine if Eh levels were low enough in the SND for denitrification to
occur (Mohn et al., 2000).
2
Soil-porewater samples were collected from the lysimeters on consecutive days each season from
the winter of 2002 until summer 2003: a total of 14 samplings over the seven seasons. To collect
the samples, a vacuum was established within each lysimeter using a field pump and portable
power source. The following day the soil porewater was extracted from the lysimeter by
extending a tube to the bottom and pumping the water into a labeled 120 ml bottle. Effluent was
sampled from the secondary treatment unit of every system. Effluent from the LON, LIN, and
MCG sites (Table 1) were collected 15 times between August 1997 and February 1999 (Sykes et
al., 1999; Sykes, 2001). Effluent from the HAZ, TAR, TWE, and SIS secondary units were
collected seasonally from the winter of 2002 until summer 2003. Soil porewater and effluent
samples were stored in 120 ml econoware brown-glass bottles at 40 C until analyzed.
Soil-porewater and effluent samples were prepared for analysis by filtering them through a #2
Whatman filter using a Buchner funnel connected to a vacuum. One mL of sample was diluted
by a factor of 20 and added to a 40 mL glass vial. A 5 mL liquid digestion reagent, consisting of
recrystallized potassium persulfate (K2S2O8), boric acid (H3BO3), and 1N sodium hydoxide
(NaOH), was added to the samples. The samples were boiled in a water bath for 15 minutes and
left overnight (American Public Health Association, 1995). Standards, created using potassium
nitrate (KNO3), were also digested following the same procedure. The following day the samples
were analyzed for total N using a rapid flow analyzer (RFA-300, ALPKEM Corp.).
RESULTS AND DISCUSSION
Nitrogen Entering the Groundwater
Average N levels in the soil porewaters, based on seasonal sampling over a 20-month period,
ranged from 2 to 42 mg/L (Figs. 1-7). Nitrogen levels from individual lysimeters ranged from 0
to 121 mg/L. Because of dry conditions during the summer of 2002, no soil-porewater samples
could be obtained from the control areas of the MCG, HAZ, TAR, and LON sites and the SND
from the LIN site (Figs. 1, 2, 3, 6, and 7). Concentrations of N entering the groundwater from the
LIN and TAR sites were below drinking water standards (10 mg/L N) for nearly every season
(Figs. 2 and 7). At the other 5 sites, N levels entering the groundwater were mostly well above
the drinking water standard.
Two of the sites, LON and MCG, showed a trend suggesting seasonal effects on the amount of N
entering the groundwater (Figs. 1 and 2). At these two sites porewater collected in the winter
had the highest N concentrations, spring and summer months showed lower levels, and the levels
increased in the fall. Although this trend was not strong, it was recognized for both years. We
suspect that lower soil temperatures in the winter and fall resulted in reduced biological activity
(plant growth, nutrient uptake, and microbial activity) in the SND such that more N was entering
the groundwater during this time of year. Seasonal effects on the amount of N entering the
groundwater were not apparent at the LIN, TAR, HAZ, SIS, and TWE sites (Figs. 3-7).
Variations in the soil types within the SND, effluent N concentrations, or loading rates may have
masked any seasonal patterns for these sites and contributed to the amount of variability seen in
the MCG and LON sites.
Reductions in Nitrogen Levels within the SND
Reduction in N concentrations, based on seasonal effluent levels and N concentrations in the
porewater samples, for the TWE, SIS, HAZ, and TAR sites range from 0 to 97%. No seasonal
effect on N removal was observed. Average N concentration reductions for the entire sampling
period were 53, 43, 40, and 33% for TWE, SIS, HAZ, and TAR sites, respectively. Reduced
concentration levels in N can be attributed to plant uptake, denitrification, and dilution. Since our
porewater samples were collected above the water table, we expect little dilution to occur within
3
the 30 cm of soil between the disposal points in the SND and where the lysimeters were located.
Lush green grass was observed in all the sites at times during the spring, fall, and summer at each
site. These observations suggest that the grassroots had access to both water and nutrients over
the SND and may potentially remove N during the growing season. Over time, however, N
mineralization will reach some equilibrium with N uptake by the grass and this effect will likely
be inconsequential. Our redox potential measurements were lower in the SND than the control
and at or below potentials reported for denitrification to occur. Therefore, we expect that
denitrification may be the leading factor in the reduction of N concentrations in these four sites.
Effluent levels dosed on the SND at the LON, LIN, and MCG sites were measured in 1997
through 1999 (Sykes et al., 1999; Sykes, 2001). Since, the data reported here represent N levels
reaching the groundwater for 2002 and 2003, examining seasonal effects was not possible. Based
on average N levels for the effluent, and our seasonal porewater measurements, reduction of N
due to treatment in the SND of these three systems is estimated to range from 0 to 99%. This
range in values is similar to the range for the four sites where both effluent and porewater
samples were collected seasonally. The average reduction for the entire sampling period,
however, was much different. Nitrogen levels in four of the seven porewater samples collected
from the LON site were higher than average effluent levels recorded for an 18 month period
from 1997 to 1999. At the LIN site, there was a much higher percent of reduction (73%) than
observed at any of the other sites. These data suggest that effluent N levels leaving the secondary
treatment unit may have increased between 1999 and 2002 at the LON site and decreased at the
LIN site during the same period. These differences in N levels in the effluent are likely due to
changes in water usage or occupancy by the homeowner, resulting in higher or lower levels of
contaminants entering the SND.
Control Plot N Levels
Ratios of N in porewaters below the SND to N concentrations below the control plots ranged
from 0.2 to 18.4. The LIN and TAR sites had ratios of less than one, meaning more N was
present in porewater samples collected below the control plots than porewater extracted below
the SND (Figs. 2 and 7). For the LIN site, five of the six seasonal measurements show this trend
(Fig. 2). Similarly in the TAR site, levels of N in the control exceeded the SND in all cases
where porewater samples could be extracted (Fig. 7). In both of these cases, the porewater
entering the groundwater from the control plots was much higher than drinking water standards.
This is significant, since the alternative systems at these locations have greatly reduced N
additions coming from disposal of domestic wastewater to less than 10 mg/L. The lawns at these
locations are plush and green suggesting the likely source of the elevated N concentrations in the
control plots is excess fertilizer.
SUMMARY AND CONCLUSIONS
Alternative OSWDS are called upon in areas where soils are marginal with respect to their
treatment capacity or resources are such that special requirements are in place to minimize
development impacts on water quality. Numerous studies have evaluated the effectiveness of the
secondary units that define the alternative OSWDS to treat wastewater. Few studies, however,
have addressed the effectiveness of SND as the final treatment step in an alternative OSWDS. In
our study we found that on average as much as 73% of the N leaving a secondary unit can be
removed by a SND, and that between 33 and 53% of the N is commonly removed. We expected
considerable seasonal variations in the N removal. These effects, however, were only observed
in two of the seven sites we studied. The lack of consistent evidence of seasonal effects on N
removal may be the result of variations in soil type, N concentrations in the effluent, and loading
rates. Variations in water usage by the homeowner may also make seasonal effects less evident.
Although as much as 73% of the N disposed of in a SND may be removed, we found that N
concentrations reaching the groundwater below these systems were well above drinking water
4
standards. These data suggest that although alternative measures were taken in these critical
coastal resource areas of Rhode Island to control N additions to the groundwater from onsite
waste disposal, more work needs to be done to control N entering our ground and surface waters.
REFERENCES
1. American Public Health Association, American Water Works Association and Water
Pollution Control Federation. 1995. Standard Methods for Examination of Water and
Wastewater, 19th ed. Washington, D.C.
2. Brady, N.C., and R.R.Weil. 2002. The Nature and Properties of Soils-13th Edition. Prentice
Hall, Upper Saddle River, NJ.
3. Burks, D.B., and M.M. Minnis. 1994. Onsite Wastewater Treatment Systems. Hogart House
Ltd., Madison, WI.
4. Carlile, B.L. 1980. Use of shallow, low pressure injection systems in large and small
installations. In Proccedings of the 6th National Conference on Individual Onsite Wastewater
Systems, 371-385. N.I. McClelland, ed. National Sanitation Foundation, Ann Arbor, MI.
5. Lance, C.L. 1975. Fate of nitrogen in sewage effluent applied to the soil. Journal of the
Irrigation and Drainage Division. 101:131-144
6. Loomis, G., L. Joubert, B. Dillmann, D. Dow, J. Lucht, and A. Gold. 1999. A watershed risk-
based approach to onsite wastewater management - A Block Island, Rhode Island case study.
In 10th Northwest On-Site Wastewater Treatment Short Course and Equipment Exhibition,
249-262. R.W. Seabloom, ed. University of Washington, Seattle, Washington.
7. Loomis, G.W., D.B. Dow, M.H. Stolt, L.T. Green, and A.J. Gold. 2001. Evaluation of
innovative onsite wastewater treatment systems in the Green Hill Pond watershed, RI – A
NODP II project update, on-site wastewater treatment. In 9th National Symposium on
Individual and Small Community Sewage Systems, 506-515. K. Mancl, ed., ASAE, Fort
Worth, Texas.
8. Mohn, J., A. Schürmann, F. Hagedorn, P. Schleppi, and R. Bachofen. 2000. Increased rates
of denitrification in nitrogen-treated forest soils. Forest Ecology and Management. 137:113-
119.
9. Peterson, C.E., and T.W.Simpson. 1992, Alternative on-site wastewater treatment and
disposal systems. Department of Crop and Soil Environmental Sciences and Virginia
Cooperative Extension Service, College of Agricultural and Life Sciences, Virginia
Polytechnic Institute and State University, Blacksburg, Virginia.
10. Reneau, R.B. Jr., C. Hagedorn, and M.J. Degen. 1989. Fate and transport of biological and
inorganic contaminants from on-site disposal of domestic wastewater, Journal of
Environmental Quality. 18:135-144.
11. Siegrist, R.L., and P.D.Jenssen, 1989. Nitrogen removal during wastewater infiltration as
affected by design and environmental factors. In 6th Northwest On-Site Wastewater
Treatment Short Course, 304-318. R.W.Seabloom, and D. Lenning, eds.University of
Washington, Seattle, Washington.
12. Simon, J.J., and R.B. Reneau JR., 1985. Hydraulic performance of prototype low pressure
distribution systems. In Proceedings of 4th National Symposium on Individual and Small
Community Sewage Systems. 251-259. ASAE, St. Thomas, MI.
13. Stewart, L.W., and R.B. Reneau JR., 1988. Shallowly placed, low pressure distribution
system to treat domestic wastewater in soil with fluctuating high water tables, Journal of
Environmental Quality. 17:499-504.
5
14. Stolt, M.H., and R.B. Reneau JR., 1991. Potential for contamination of ground and surface
waters from on-site wastewater disposal systems: Crop and Soil Environmental Sciences
Department, Virginia Polytechnic Institute and State University, Blacksburg, Virginia.
15. Sykes, A.D., G. Loomis, D. Dow, and M.H. Stolt. 1999. Evaluation of treatment
performance in Rhode Island sand filters. In Proceedings from the Annual Meetings of the
National Onsite Wastewater Recycling Association. 195-200. Jekyll Island, Georgia
16. Sykes, A.D., 2001. Performance of sand filters in Rhode Island, Department of Natural
Resources, Non-Thesis Masters Degree Report, University of Rhode Island, Kingston,
Rhode Island.
17. Walker, W.G., J. Bouma, D.R. Keeney, and F.R. Magdoff. 1973. Nitrogen transformation
during subsurface disposal of septic tank effluent in sands: I. Soil transformation, Journal of
Environmental Quality 2:521-525.
6
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W N 02
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S e as
on
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a m p li
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(
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:
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a t io
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m
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S yk
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., 1
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9
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;
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t an
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8
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n
t r at
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10
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F i gu
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s
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a
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)
a
n
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t
a
d
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t
h
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(C
ON
).
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f f l ue
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a
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u
t
o
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f
r om
3
2
s
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s
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r 4
1
m o nths . E r r o r bar s
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s
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11
020406080
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Se
a
s
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l
S
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m
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s
T
N
(
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g
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F
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SI S
Fi
g u r e
5
:
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n t
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p
o r e wa
t
e r f
r om
t
h e
S
I S s
i t e .
S
a m p l e s w
e
r
e c
o
l
l ec
t
ed
t
w i ce s e as on al l y fr o m mu lt i p le
l y s i m e te
r s p
l
a c e d 3
0
c
m b
e
l o w t
h
e
s
h al
l o w -na
r
r o w d
r
ai
n
f
i e l d (
S
N D ) a
n
d
a
t
a
d
e
p
t
h
o
f
7
0
c
m
i
n
t
h e cont r o l ar e a (C ON ).
E f f l ue
nt
l
e ve
l s (
E
F F ) r
e pr
e s e n t
a
v
e
r a g e
s
e as
on
a
l
i
n
p
u
t
o
f
N
f
r om
3
2
s
a m p l i n g s o
v e r 4
1 m
o n t h s .
E rro r b a rs re p r e s e n t +/- o n e
s t an
d
a
r
d d
e
v
i
a
t
io
n
.
12
020406080
10
0
12
0
14
0
W N 02
S P 02
S M 02
F L 02
W N 03
S P 03 S M 03
Se
a
s
o
n
a
l
S
a
m
p l i ng
s
T
N
(
m
g
/
L
)
EF
F
SN
D
CO
N
No
Da
t
a
HA Z
F i g u r e 6
:
T
o ta
l N
c
o nc
e n tr
a t io
ns
i
n
t
h
e
p
o r e w a te
r f
r o m t
h
e
H
A Z s
i t e .
S
a m p l e s w
e
r
e c
o l l ec
t
ed
t
w i ce s e as on al l y f r om
m u lt
i p le
l
y
s i m e t
e r s p
l a c e d 3
0 c
m b
e lo
w t
h e s
h a ll
o
w -
n
a r r o w d
r a i nf
ie
l d (
S
N
D ) a
n
d
a
t
a
d
e
pt
h
o
f 70 cm i n t h e c o n t r o l ar ea
(C
ON
).
E
f f l ue
nt
l
e v e l s (
E
F F )
r
e pr
e s e n t
a
v
e r ag
e
s
e as
on
a
l
i
n
p
u
t
o
f N
f
r o m 3
2
s
a m p l i ng
s
o
v
e
r 4
1 m o nths . E r r o r bar s
r e pr
e s e n t
+
/-
o
n
e
s
t an
d
a
r
d d
e
vi
a
t
i
o n.
13
020406080
10
0
12
0
14
0
W N 02
S P 02
S M 02
F L 02
W N 03
S P 03 S M 03
S e as
on
al
S
a m p li
n
gs
T
N
(
m
g
/
L
)
EF
F
SN
D
CO
N
No
Da
t a
F i g u r e 7
:
T
o ta
l N
c
o nc
e n tr
a t io
ns
i
n t
h
e
p
o
r e w a te
r f
r o m t
h
e
T
A
R
s
i t e .
S
a
m
p l e s w
e
r
e c
o l l ec
t
ed
t
w i ce s e as on al l y f r om
m u lt
i p le
l
y
s i me
t e r s p
l a c e d
3
0 c
m b
e lo
w t
h e s
h a ll
o
w -
n
a r r o w d
r ai
n
f
ie
l
d (
S ND
)
a
n
d
a
t
a
d
e
p
t
h
o
f
70 cm in t h e c o nt r o l ar ea
(C
ON
).
E
f f l ue
nt
l
e v e l s (
E
F F )
r
e pr
e s e n t
a
v
e r ag
e
s
e as
on
a
l
i
n
p
u
t
o
f N
f
r om
3
2
s
a m p l i ng
s
o
v
e
r 4
1
m o nths . E r r o r bar s
r e pr
e s e n t
+
/-
o
n
e
s
t a nd
a
r
d d
e
vi
a
t
i
o
n.
TAR
14