FINAL-REPORT
STORMWATER MITIGATION
IN MAMARONECK HARBOR
LONG ISLAND SOUND STUDY ACTION PLAN
Submitted to
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Wetlands, Oceans, and Watersheds
Oceans and Coastal Protection Division
30 September 1991
EPA Contract No. 68-C8-0105
Work Assignment 2-30
Prepared by
Battelle Ocean Sciences
397 Washington Street
Duxbury, Massachusetts 02332
(617) 934-0571
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CONTENTS
1.0 BACKGROUND
2.0 TASK 1 - ANALYSIS OF BMPs 1
2.1 Institutional Evaluation 2
2.2 Technical Review and Demonstration Project 3
3.0 TASK 2 - WATER QUALITY ASSESSMENT 4
4.0 TASK 3 - PRELIMINARY MODEL CALIBRATION 5
5.0 SUMMARY AND CONCLUSIONS 6
APPENDICES
A. Evaluation of Best Management Practices Applied to Control of Stormwater-Borne
Pollution in Mamaroneck Harbor, New York
B. Analysis of Best Management Practices in Mamaroneck Harbor Watershed
C. Mamaroneck Harbor Project - Data Evaluation and Model Analysis
D. "Mamaroneck Harbor Action Plan Demonstration Project"
Figure 1. Halstead Avenue East Outfall/Storm Sewer System Facing page 1
U.S. EPA Region II Library
290 Broadway, 16th Fl.
New York, NY 10007-1866
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Figure 1. Halstead Avenue East Outfall/Storm Sewer System.
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1.0 BACKGROUND
As pan of the National Estuary Program, funds have been made available for the implementation of
priority action plans in estuaries for which 5-year action plans are in place. The Long Island Sound Study
has developed an action plan for the management of stormwater flows in Mamaroneck Harbor, New
York.
At present, .the beaches in Mamaroneck Harbor must be periodically closed during the summer following
rainfall events because of coliform contamination. Previous work has indicated that stormwater runoff
and sanitary sewer overflows are the major contributors to the elevated coliform levels that occur in the
Harbor following rain events. The sewer overflow problem is currently being addressed through the
negotiation of Administrative Orders of Consent. To address the elevated levels of coliform bacteria in
stormwater, Best Management Practices (BMP) that can help to reduce coliform loadings in stormwater
runoff were identified and evaluated.
The Mamaroneck Study, designated as Work Assignment 30 (WA-30), was implemented to determine
the extent to which a reduction of coliform loading in stormwater and, consequently, in the Harbor was
possible with these available technologies.
This report summarizes the four tasks that were conducted and completed under Work Assignment 30.
Task 1. Analysis of BMPs
Task 2. Water Quality Assessment
Task 3. Preliminary Model Calibration
Task 4. Development of Education Program
2.0 TASK 1 - ANALYSIS OF BMPs
The BMPs (Best Management Practices) utilized by the communities in the Mamaroneck Harbor water-
shed were identified in the report Evaluation of Best Management Practices Applied to Control of
Stomwater-Bome Pollution Mamaroneck Harbor, New York (Appendix A). The effectiveness of these
BMPs in reducing fecal coliform loadings in stormwater were estimated from a review of the technical
literature. The removal efficiency, coupled with the effectiveness of implementation from a political and
economic viewpoint supplied by the local communities, was the basis for ranking of the BMPs. One or
more BMPs were recommended as a demonstration project for the Long Island Sound
Study (Appendix B).
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2.1 INSTITUTIONAL EVALUATION
Given the very large expenditures currently being made to upgrade not only the Mamaroneck wastewater
treatment plant, but also the sewer systems in the Mamaroneck Harbor tributary watersheds, communi-
ties now have an opportunity to make changes in the overall approach to stormwater management. The
changes can build on these upgrades to significantly improve the water quality of the Harbor.
Communities have made significant steps in the direction of flood-hazard management, and have also
established means to protect critical environmental areas, the latter primarily through the Local Water-
front Revitalization programs and via the State environmental quality review law. Many local regulatory
programs have been enacted, and several types of flood and sediment control management practices are
routinely put in place. However, regulatory measures are extremely fragmented, several key implementa-
tion elements are advisory only, and there is no mechanism for the management and oversight of the
watershed as a whole to ensure compatibility of technical and interjurisdictional approach.
Although important efforts have been made to understand and to address bacterial loadings to the Har-
bor, the primary focus of stormwater management efforts at the County and local level has been on
flood-hazard management. Practices in place are designed chiefly to meet the objectives of detaining or
timing peak flood flow rather than to enhance the quality of the water that runs off the land. Communi-
ties have continued to take a very traditional approach to drainage, piping runoff to watercourses. A
wide range of opportunities may be available to provide improved treatment and infiltration of runoff
before it enters the piped conveyance network, and to work toward restoring the floodplains* natural
capacity for storage and treatment of runoff waters. Regulations and policies at the local, County and
State levels could be adjusted to support such an expansion of focus.
Using the tools at hand, municipalities could move aggressively to eliminate existing contamination
sources. Local land-use review and site-planning authorities could be revised to ensure consistency and
to support objectives of water quality enhancement. Drainage provisions should be updated. Local Wa-
terfront Revitalization programs, environmental quality review authorities, surface-water protection regu-
lations, and wetland and floodplain protection authorities should be strengthened and rigorously imple-
mented. Municipalities should give careful consideration to the potential role of nutrient loading in sus-
taining survival of coliform bacteria, and should develop effective means to manage pet wastes, which
may be a serious source of contamination.
Despite evident concern at the local level, administrative inconsistencies, lack of funding, and personnel
constraints limit the effectiveness of current implementation efforts. Maintenance problems are poorly
understood and are likely to increase in importance. Inspection, maintenance, and enforcement prac-
tices need to be rationalized, formalized, and better funded at the local level.
A management system that treats the watershed as a whole should be developed. Such a system could
allocate drainage contributions, coordinate efforts, address cumulative water quality and flooding impacts
of stormwater, and improve interjurisdictional consistency. Use of regional facilities to detain flood flows
and improve water quality should be emphasized before escalating land values eliminate the possibility
for effective action. Findings indicate that existing BMPs could be upgraded to meet objectives for im-
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proved water quality as well as for flood control. A stormwater-management utility framework could be
applied to meet administrative and management costs.
12 TECHNICAL REVIEW AND DEMONSTRATION PROJECT
Mamaroneck Harbor is a natural, constricted embayment that is surrounded by established urban devel-
opment. It is valued as a recreational resource, and it supports a number of beaches that are used for
swimming during the summer. However, the Harbor is subject to periodic closures because of elevated
bacterial levels that are associated with the influx of stormwater. Recent efforts have been made to
understand and address contamination sources, with the goal of eliminating these beach closures.
In the past, the primary focus on stormwater management in the Mamaroneck watershed has been on
flood control. Practices have been designed to mitigate the effects of peak flood flow by piping runoff
into directed watercourses as quickly as possible (Figure 1). Existing regulations on the local, County,
and State levels encouraged this traditional approach to drainage.
More recently, the quality of the runoff has become an issue of concern. To address water quality, it has
been recognized that a management system that treats the watershed as a whole must be developed.
Toward that end, a number of Best Management Practices (BMP) have been examined as having the
potential to upgrade the quality of the stormwater runoff entering the Harbor. These BMPs include
structural provisions such as detention ponds, infiltration devices, and vegetative measures, and nonstruc-
tural (or housekeeping) ordinances such as catch-basin cleaning, street sweeping, and litter control. Many
of these BMPs have been implemented by some of the communities in the Mamaroneck watershed.
However, these BMPs could be upgraded and implemented regionwide to address the objectives of signif-
icantly improving the quality of stormwater runoff and potentially eliminating the necessity of closing the
beaches in Mamaroneck Harbor.
The review of the BMPs used in the Mamaroneck Harbor Watershed and their bacterial removal poten-
tial indicates that the following were suitable for a demonstration project:
Catch-basin cleaning
Street cleaning
Pet-waste ordinances
The implementation of these nonstructural Best Management Practices (BMP) was facilitated by increas-
ing the public's understanding of the coliform problem and of the benefits of implementing BMPs. A
public education program was initiated that was designed to satisfy the requirements of Task 4, Develop-
ment of Education program, of this work assignment. A brochure, entitled "Mamaroneck Harbor Action
Plan Demonstration Project," was prepared by Battelle for public dissemination. The brochure was used
by local and State agencies to raise public awareness to the positive contribution that the nonpoint-source
management project would have on the viability of the Harbor and the locale. This brochure forms
Appendix D of this report. Approximately 500 copies of the brochure were supplied to participants in
the Action Plan as follows.
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Town of Harrison Village of Scarsdale
Village of Mamaroneck City of White Plains
Town of Mamaroneck Westchester County
City of New Rochelle New York Sea Grant Institute
City of Rye New York State Department of Environmental
Village of Rye Brook Conservation
U.S. Environmental Protection Agency Region n
The effectiveness of the two mechanical nonstructural BMPs was demonstrated and evaluated in existing
residential watersheds. Two storm drainage basins consisting of catchbasins and storm drains outfalling
to the Mamaroneck River were selected and monitored for total and fecal coliform during stormwater
runoff events during the summer and early fall of 1989.
One of these drainage basins was selected as the "test" system (see Figure 1), the other as a "control."
In the test system, the 23 catchbasins were vacuumed. The brochure defining the project and emphasiz-
ing control strategies, such as for pet wastes, was assembled and distributed door to door. The frequency
of mechanical street sweeping was increased from approximately monthly to twice weekly for the subse-
quent 4 weeks. Coliform concentrations were determined for several weeks in the Mamaroneck River
and Harbor before and after stormwater runoff events in these two drainage basins. However, it was
difficult to judge the effectiveness of the education program based on the responses to the door-to-door
visits.
3.0 TASK 2 - WATER QUALITY ASSESSMENT
The primary purpose of this task was to quantify the impact of urban runoff on water quality and to
determine the degree to which runoff may continue to cause use impairment after storm sewer mitigation
measures related to infiltration and inflow are implemented. The objectives of this work were to provide
a methodology and guidelines to assess stormwater and nonpoint-source impact on water quality, to
illustrate how mathematical water-quality modeling could be used to assess water quality issues in Long
Island Sound embayments, and to provide an initial technical format for developing permit limitations for
stormwater discharges.
To complete this task, it was necessary to complete the review of existing information. An urban storm-
water model had been developed in a previous investigation, and the loading rates generated by this
model were the primary cause for concern about urban stormwater runoff. This model was carefully
reviewed by Battelle and its subcontractor, HydroQual, Inc., and was refined as appropriate during the
calibration phase in Task 3.
A time-varying water quality model for the Harbor was developed based on physical characteristics of the
study area, and was also refined during the calibration task (Appendix C). This time-varying water quali-
ty model and the urban stormwater model simulate typical summer conditions: the urban runoff model
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generates coliform loading rates and the water quality model calculates receiving-water responses. Statis-
tical analyses of the results were developed and evaluated. The results from these analyses provided a
quantitative basis for determining whether urban runoff continues to cause use impairment after imple-
menting other controls related to infiltration/inflow into the sanitary sewer system. The analysis further
defined the percent reduction of coliform discharge rates necessary to achieve water quality objectives.
The results provided a technical guideline for selecting and implementing BMPs.
Sensitivity analyses were performed using stormwater and water quality models. Model parameters af-
fecting discharge rates, transport, and dilution were evaluated. These analyses helped to identify the
strengths and weaknesses of the modeling analysis. A Gnal report was prepared that discusses model
results and the methods used for assessment of stormwater impacts (Appendix C). Data evaluation
results are preseented in Section 6.0 of this Final Report.
4.0 TASK 3 - PRELIMINARY MODEL CALIBRATION
The urban stormwater model and the time-varying water quality model of Mamaroneck Harbor were
refined in this task in an attempt to reproduce available prototype data collected in the area. Since
historical data collections were not designed for mathematical model development, these calibrations
were considered preliminary.
The urban stormwater model developed by Satterthwaite Associates, Inc., simulates a single 2-year storm.
To serve as a flow and load generator to the time-varying water quality model, the stormwater model
was amended to accommodate continuous rainfall events for various summer seasons. This generated
calculations of temporal flows and coliform discharges based on actual rainfall records.
The runoff calculated by the time-varying stormwater model was compared against flow measurements
collected by the Geological Survey (USGS) at the mouths of Beaver Swamp Brook and the Mamaroneck
River. Six years of flow measurements (1983 through 1988) were compared to calculated runoff volumes.
The theoretical basis and/or model coefficients were adjusted to reproduce overall volumes of runoff
measured at the USGS gauging stations.
The historical database of measured coliform concentrations in the discharges and in the receiving waters
was limited with regard to both frequency and quality of data. Only in 1984 were samples collected in
storm drains and in receiving-water streams upstream of the Harbor. In addition, laboratory procedures
capped the measurable quantity of most coliform samples at 24,000 MPN/100 mL. Therefore, for most
counts greater than 24,000 MPN/100 mL, the true coliform quantity was unknown. The impact of the
laboratory limitations on the model analysis was uncertain, and poses a restriction on developing a fully
calibrated runoff model.
The transport parameters of the water quality model was calibrated using available salinity data collected
by Westchester County. Flows generated by the runoff model for a summer season (wet and dry) were
routed through the water quality model. Dispersion coefficients were adjusted to reproduce average
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salinity data at the various summer sampling stations. However, salinity data were available only at the
surface with two or three collections per month. Therefore, data limitations permit only a cursory cali-
bration of transport parameters.
A model calibration of total and fecal coliform bacteria in the Harbor was attempted. Data limitations
with regard to frequency and "capping" restricted model calibration. Due to the highly variable nature of
coliform concentrations and transport influences (i.e., rainfall events and tidal interactions), it was not
reasonable to compare temporal model results against discrete measurements in the water column.
However, a more realistic approach was adopted to compare the probability distribution of the observed
data at a given location against the calculated probability distribution at the corresponding model seg-
ment. In this approach, the model calibration was not as sensitive to transient system behavior, but
included the dynamic effects of intermittent runoff events.
Another restriction that affected model calibration was the lack of loading information from sources
other than stormwater runoff. Other coliform discharges included dry-weather overflows or overflows
attributable to excessive infiltration/inflow into the separate sanitary system. Although these sources had
been identified, the magnitude of these discharges could not be defined for a selected calibration period
(i.e., 1984). These discharges were estimated from available information as characterized in the final
report titled Mamaroneck Harbor Project Data Evaluation and Model Analysis, which forms Appendix C of
this report.
5.0 SUMMARY AND CONCLUSIONS
A comprehensive data-evaluation and modeling analysis was performed to investigate the impact of
storm-runoff flows to Mamaroneck Harbor. The primary objectives of this study were to assess (1) the
influence of urban storm runoff and nonpoint-source impact on the quality of bathing water and (2) the
required level of abatement for compliance with New York State bathing water coliform standards.
These objectives were designed to evaluate existing bacterial conditions, quantify the sources of coliforms
at bathing beaches, and assess abatement requirements. The evaluations described in the reports con-
tained in Appendices A-C were directed toward determining compliance with New York State bathing
standards as defined by numerical limits on total and on fecal coliform concentrations. The Westchester
County Department of Health assesses the sanitary quality of bathing water at Mamaroneck Harbor
beaches in accordance with policy that is based primarily on total coliform data, in accordance with New
York State and Westchester County Sanitary Codes.
The activities completed through the four tasks of this study include
Evaluation of existing data
Evaluation/revision of the existing storm runoff model and assessment of storm-runoff water
quality
Development of a time-variable water-quality model of Mamaroneck Harbor with calibration
Assessment of the required level of abatement for runoff and for nonpoint-source pollutants.
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Based on the analyses completed during these tasks, the following conclusions are presented.
1. Elevated coliform concentrations are present throughout the Mamaroneck Harbor and Beaver
Swamp Brook watersheds. These drainage basins account for nearly all freshwater flow to Ma-
maroneck Harbor. Coliform levels during wet-weather conditions are significantly higher than
during dry-weather conditions. Coliform levels during both wet- and dry-weather conditions are
considerably higher than New York State coliform standards for bathing.
2. A composite analysis of all beach data collected between 1983 and 1989 shows violations of total
and fecal coliform standards at three of the six beaches in the vicinity of Mamaroneck Harbor.
The three northern beaches - Harbor Island (also known as S.E. Johnston), Shore Acres, and
Mamaroneck Beach Cabana and Yacht Club (Mamaroneck BC&YC) - show exceedance of
coliform standards. The three southern beaches - Beach Point, Orienta Beach, and Westchester
Summer Day School (Westchester SDS) - are in compliance with coliform standards.
3. An analysis of the beach fecal coliform data indicates that fecal coliform levels greater than 1000
MPN/100 ml have been reported in 30% to 50% of the samples collected at the three northern-
most beaches. Although this is not a violation of bathing standards, New York State Sanitary
Code suggests consideration of beach closure and requires additional sampling when fecal coli-
form levels exceed 1000 MPN/100 ml.
4. An analysis of data at the beaches, excluding wet-weather samples, indicates violations of fecal
coliform bathing standards at the northern beaches even during dry-weather conditions. There-
fore, background tributary loadings and/or local sources of bacteria can cause noncompliance
with coliform standards.
5. The analysis of tributary checkpoint data distinguishes the relative contributions of coliform bac-
teria from background and storm-related sources within the tributaries. About 89% of the total
coliform loads is estimated from stormwater runoff and 11% from background sources. Similar-
ly, about 74% of the fecal coliform loads is estimated from stormwater runoff and 26% from
background sources. Of the total from both drainage basins, 67% of the total coliform and 86%
of the fecal coliform are estimated to originate from the Mamaroneck River basin.
6. Estimated storm runoff concentrations of coliform bacteria are reasonable when compared to
concentrations measured in other areas. The results imply that on an areawide basis the influx of
other sources of bacteria, such as sanitary waste, cannot be distinguished in this analysis. Howev-
er, the possibility of some level of sanitary inflow to the Harbor watershed is still feasible.
7. Localized sources of bacteria vary from beach to beach and may vary from year to year. Based
on the 1989 model analysis and data evaluation, localized sources have relatively significant im-
pact at two beaches and lesser impact at two other beaches.
8. The model and data analyses indicate that at Harbor Island and Shore Acres an approximate
reduction of total coliforms would be required to meet standards. At Mamaroneck
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BC&YC, a minor reduction of total colifonns would be required. With regard to fecal coliforms,
reductions of about 50% to 75% would be required to meet standards at the three northern
beaches (Harbor Island, Shore Acres, and Mamaronec BC&YC).
9. Assuming localized source control, Mamaroneck BC&YC may comply with coliform standards.
Harbor Island and Shore Acres would still require substantial reductions in coliforms from the
tributaries (50% to 75%) to comply with standards.
10. To comply with fecal coliform standards at Harbor Island during dry-weather conditions would
require a 33% reduction of background tributary sources of fecal coliforms. This reduction is in
addition to localized source control. At shore Acres, the required level of reduction of back-
ground tributary sources is marginal.
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Appendix A
EVALUATION OF
BEST MANAGEMENT PRACTICES APPLIED TO CONTROL OF
STORMWATER-BORNE POLLUTION IN
MAMARONECK HARBOR, NEW YORK
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Evaluation of Best Management Practices
Applied to Control of Stormwater-Borne Pollution
in Mamaroneck Harbor, New York
Analysis and Recommendations
prepared for
the Long Island Sound Study
U.S. EPA Region E
by
Jennie C. Myers
Consultant to Battelle Ocean Sciences
Duxbury, Massachusetts
March 1989
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Table of Contents
Executive Summary of Findings and Conclusions
Introduction and Background 2
Part I Existing Regulatory Initiatives at the County and Local Level 7
A. GENERAL FINDINGS AND CONCERNS 7
1. Role of Westchester County 7
2 .Role of Local Jurisdictions 9
3. Overall Finding: Need for an Inter-jurisdicrional Watershed Management
Program 13
4. Other Recommendations to Enhance Effectiveness of Existing Regulatory
Measures 16
B. EVALUATION OF SPECIFIC REGULATORY BMPs 18
1. Zoning 18
2. Subdivision and Land Development 20
3 Site Planning, 22
4. Building Codes 22
5. Erosion and Sediment Control/Earth Removal 23
6. Other Regulatory Tools 25
Part II Structural Best Management Practices 27
A. GENERAL FINDINGS AND CONCERNS 27
1. Overall Recommendations to Enhance Local Enforcement Capabilities 29
2. Overall Finding: Need for Rationalized Performance Standards 30
B. SPECIFIC FINDINGS AND CONCERNS RELATED TO INDIVIDUAL BMPs....32
1. Detention Devices 32
2. Recharge/Infiltration Devices 34
3. Vegetative Measures :36
4. Overall Finding: Potential to Enhance Mamaroneck Harbor Water Quality
via New Structures and Up-grades 37
Part HI Housekeeping Ordinances andPractices 40
1. Catch Basin Cleaning 40
2. Maintenance of Oil/Water Separators 41
3. Lawn-Care-Related Restrictions 41
4 Road De-Icing 43
5. Street Sweeping and Leaf Removal 44
6. Litter Control 45
7 Dog Clean-up Laws 46
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Contacts C-l
References R-l
Appendix I Regulatory Controls in Place in the Study Communities A-l
Town of Harrison A-l
Town of Mamaroneck A-6
Village of Mamaroneck A-12
Village of Port Chester A-15
City of Rye A-19
Village of Rye Brook A-23
Village of Scarsdale A-27
City of White Plains A-31
Appendix II.. Structural and Housekeeping Controls in Place in the Study
Communities
Structural Controls in Place in the Study Communities (Table 1)
Housekeeping Controls in Place in the Study Communities (Table 2)
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Executive Summary of Findings and Conclusions
Given the very large expenditures currently being «Hg to upgrade not only the
Mamaroneck wastewater treatment plant, but also the sewer systems in the Mamaroneck
Harbor tributary watersheds, communities now have an opportunity to make changes in the
overall approach to stormwater management The changes can build on these upgrades to
significantly improve the water qulaity of the Harbor.
Communities have made significant steps in the direction of flood hazard management,
and have also established means to protect critical environmental areas, the latter primarily
through the Local Waterfront Revitalization programs and via the state environmental
quality'review law. Many local regulatory programs have been enacted, and several types
of flood and sediment control management practices are routinely put in place. However,
regulatory measures are extremely fragmented, several key implementation elements are
advisory only, and there is no mechanism for management and oversight of the watershed
as a whole to ensure compatibility of technical and inter-jurisdictional approach.
Although important efforts have been made to understand and address bacterial loadings
to the Harbor, the primary focus of stormwater management efforts at the county and local
level has been on flood hazard management Practices in place are chiefly designed to meet
objectives of detaining or timing peak flood flow rather than enhancing the quality of the
water that runs off the land. Communities have continued to take a very traditional
approach to drainage, piping runoff to watercourses. A wide range of opportunities may
oe available to provide improved treatment and infiltration of runoff before it enters the
piped conveyance network, and to work toward restoring the flopdplains' natural capacity
for storage and treatment of runoff waters. Regulations and policies at the local, county
and state levels could be adjusted to support such an expansion of focus.
Using the tools at hand, municipalities could move aggressively to eliminate existing
contamination sources. Local land use review and site planning authorities could be
revised to ensure consistency, and to support objectives of water quality enhancement.
Drainage provisions should be updated Local Waterfront Revitalization programs,
environmental quality review authorities, surface water protection regulations, and wetland
and floodplain protection authorities should be strengthened and rigorously implemented.
Municipalities should give careful consideration to the potential role of nutrient loading in
sustaining survival of coliform bacteria, and should develop effective means to manage pet
wastes, which may be a serious source of contamination.
In spite of evident concern at the local level, administrative inconsistencies, lack of
funding, and personnel constraints limit the effectiveness of current implementation efforts.
Maintenance problems are poorly understood and are likely to increase in importance.
Inspection, maintenance, and enforcement practices need to be rationalized, formalized, and
better funded at the local level.
A management system that treats the watershed as a whole should be developed. Such a
system could allocate drainage contributions, coordinate efforts, address cumulative water
quality and flooding impacts of stormwater, and improve inter-jurisdictional consistency.
Use of regional facilities to detain flood flows and improve water quality should be
emphasized before escalating land values eliminate the possibility for effective action.
Findings indicate that existing BMPs could be upgraded to meet objectives for improved
water quality as well as flood control. A stormwater management utility framework could
be applied to meet administrative and management costs.
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Introduction and Background
Mamaroneck Harbor is a valuable recreational waterbpdy, supporting several marinas,
beaches, and mooring fields. It is also vulnerable to the impacts of stormwater, due to a
range of interrelated factors. The Harbor's natural configuration as a shallow constricted
waterbody exacerbates the impacts that storm drainage from a large, heavily altered
watershed can generate. To summarize the sources of concern:
Mamaroneck is a constricted embavment surrounded by densely developed, older
urban areas, particularly in the lower watershed.
Although beach closures raised the colifortn contamination issue that motivated
much of the current corrective action being directed toward water quality
improvement, harbor sediments have been contaminated with the range of classic
constituents associated with both stormwater and sewage pollution. Sediment
loading remains a significant concern, contributing to flooding problems, impeding
piped drainage, and serving as a potent sourceof contamination.
The contributing watershed is both large and steep, and has been severely
modified hydrologically over the years.
Heavy development of the floodplains has led to severe flooding problems which
vary dramatically from one sub-watershed to another. Flooding has been addressed
primarily via structural controls.
Much of the sewer system is between SO and 80 years of age. Though storm and
sanitary sewers are technically separated, the system is badly deteriorated.
Hydraulic overloading problems are exacerbated by numerous illegal connections,
yielding storm flow quality similar to that of combined sewer overflows in wet
weather.
The contributing watershed includes portions of two sewer districts, one
discharging to Mamaroneck Harbor and the other directly to Long Island Sound at
New Rochelle. The Mamaroneck publicly owned treatment works is under consent
order to upgrade to secondary treatment, but has historically been subject to a series
of malfunctions. The capacity of the upgraded plant will still be insufficient to treat
total contributing flow unless surcharge can be very significantly reduced.
Eleven separate autonomous jurisdictions have distinct approaches to
infrastructure, planning, and development problems. Particularly from the upper to
lower watershed, water management priorities differ considerably, due to
differences in the magnitude and frequency of flooding events experienced.
Study Context
A number of research and management efforts in the Mamaroneck watershed provide a
basis for analysis of stormwater management needs and opportunities. These include early
work conducted during the mid-1940's and 1950's examining stormwater management and
coliform loadings respectively, the Westchester County 208 studies and related plans, and a
County Department of Health Study series initiated in 1984 relating coliform concentrations
to various monitored sources and factors.
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The County of Westchester and the Village of Mamaroneck commissioned a study,
completed in 1987, to evaluated Mamaroneck Harbor pollution "components." That study,
prepared by Walter B. Sattenhwaite Associates, Inc., identified deficiencies in the storm
and sanitary sewer infrastructure that contribute to coliform loadings, quantified urban
runoff pollutant loadings, evaluated the complex set of grpundwater and infrastructure
interactions leading to documented surcharge and hydraulic overloading, and recommended
use of general categories of best management practices to address potential nonpoint source
contributions.
A two-phase sewer system evaluation and plan for the Mamaroneck Sewer District was
initiated by the County Department of Environmental Facilities. The set of studies, which
involved analysis by two separate engineering consultants, yielded an evaluation of
infiltration and inflow problems as well as a facilities report and plan for major
rehabilitation of storm and sanitary sewers. Priorities among facilities construction needs
are set based upon defined "cost-effectiveness" criteria.
As pan of the effort to upgrade facilities, municipalities are required to identify illegal
private connections to sanitary sewers using county smoke detection equipment if
necessary, and to enforce local sewer ordinances mandating re-rounng of on-lot stormwater
drainage. The Village of Mamaroneck and the Town of Harrison have made significant
progress in this area.
In 1988, the Westchester County Department of Health initiated comprehensive
inventory of municipal sewer contributions to Mamaroneck Harbor, covering a range of
local maintenance and sewer correction problems. The results of the questionnaire are
being assembled as response files are completed, but have not yet been compiled. The
inventory questionnaire was reviewed. Results should be extremely valuable to the County
in allocating effort, because municipalities were requested not only to identify sewered
areas, problem overflow areas, and concentrations of suspected illegal connections, but
also to provide basic data on capacity, condition of pumping stations, cleaning and
maintenance programs, and progress on public infiltration and inflow as well as elimination
of illicit connections.
The Beaver Swamp Brook Watershed Model and Management Plan was prepared to
analyze stormwater problems comprehensively in terms of joint water quality and flood
hazard management issues. Using a runoff model calibrated to estimate watershed-specific
analytical parameters, the plan proposed a management approach based upon zones of
runoff contribution. Other elements included a rationale for location of several regional
detention facilities, a review of local regulatory issues, and a detailed implementation
strategy, including recommendations for development of a watershed management system
utilizing a coordinated regulatory framework. The plan has been used as the basis to
support a formal intermunicipal agreement on management needs and objectives and serves
as a model framework for application to other watersheds.
In view of the history of County stormwater problems, the potential for their
exacerbation with growth, and the potential advantages offered by the watershed
management approach applied in the Beaver Swamp Brook Watershed, the County
Watershed Management Task Force has initiated a feasibility study to evaluate needs and
methods for the development of a County-wide administrative agency to manage
stormwater. Critical documentation will be provided by the feasibility study, which was
scheduled for completion in the winter of 1988/89. Overall, the County has supported
preparation of more than 24 studies and projects related to municipal stormwater
management concerns.
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Another important set of efforts have grown out of the development and implementation
of Local Waterfront Revitalization Programs (LWRP). Initiated under the aegis of the state
coastal zone management program, housed in the New York Department of State, the
LWRPs have enabled participating communities to undertake a comprehensive review of
local regulatory and planning capabilities and needs in view of clearly defined state and
local objectives. Several municipalities have worked jointly with neighboring communities
in developing the plans, and are working to develop intermunicipal solutions to watershed
problems in the coastal zone. The plans also provide a means of incorporating the Soil and
Water Conservation District's recommended best management practices for nonpoint
source controls in a manner that addresses inter-jurisdictional concerns directly.
Methodology
As outlined above, several available documents contribute to an understanding of the
stormwater problems affecting Mamaroneck Harbor water quality. Available documents
were reviewed and evaluated. Based on the results of the evaluanon and conversations
with County personnel, the detailed framework of the current analysis was adjusted to
build upon and complement existing research results so as to make optimum use of contract
resources.
Conversations with Mr. Materazzo of the Westchester County Department of
Environmental Facilities indicated that this study should not duplicate elements of the two-
phase facilities analysis discussed in the previous section. Similarly, officials of the
Westchester County Department of Health indicated that an inventory of the condition of
underground sewage disposal systems in critical County areas had led the Department to
eliminate those systems from consideration as a significant source of Harbor water quality
degradation. Based on these results, septic systems were not considered in this analysis.
A comprehensive telephone interview questionnaire was prepared for adminmistration to
local officials. The interview format was designed to supplement literature sources and
available documentation. It addressed several areas of interest in evaluating the
effectiveness of existing nonstructural and structural BMPs and identifying those that could
be applied toward control of stormwater impacts in Mamaroneck Harbor.
In addition, important insights on related issues were provided through supplemental
telephone conversations with officials of the New York State Department of Environmental
Conservation, the New York Department of State Coastal Zone Management Program, the
U.S. Army Corps of Engineers, Westchester County, and other concerned parties.
Categorizing Controls
According to the definition applied by the Soil Conservation Service, structural best
management practices or controls are those which involve "any disturbance of tne land
surface," while nonstructural controls do noi.There is considerable interaction among
approaches to structural and nonstructural controls. Certain iand use regulatory measures.
ior example, encourage control of sources, or implementation of nonstructural strategies,
while recommending installation of specific structural devices. As a valid basis for
categorization, however, nonstructural controls based on input prevention and initial
control of loadings have generally been found to be considerably more cost-effective than
structural approaches. Of key importance, however, is the wise use of multiple controls,
and the manner in which nonstructural controls are applied as complements to structural
practices.
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For simplicity, this evaluation will categorize controls in the following manner:
I Elements of existing institutional framework potentially applicable to stormwater
management and water quality management planning:
Zoning
Subdivision ordinances
Site planning
Building codes
Erosion and sediment control
Earth removal
^Other related controls
n Structural Controls, considered in three categories:
Detention devices
Recharge/Infiltration devices
Vegetative practices
HI Housekeeping Practices
Litter management
Street cleaning practices
Catch basin cleaning
Maintenance of oil/water separators
Fertilizer, pesticide, and herbicide controls
Roadway de-icing
Dog clean-up laws
Evaluation Criteria
As a basis for evaluation of structural and nonstructural controls available, the following
genera] criteria, which address all standard aspects of stormwater management programs,
were used:
1) Adequacy of technical guidelines (in terms of clarity and overall ability to reach policy
objectives; public safety; protection of groundwater, minimized maintenance requirements;
simplified design procedures; cost effectiveness; compatibility with existing state
regulations and standards; coordination with flood protection objectives);
2) Definition and applicability of
Minimum design and/or performance criteria
Site plan requirements
Facility design guidelines and procedures
3) Maintenance considerations
4) Inspection considerations
5) Enforcement considerations
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With regard to the effectiveness of institutional arrangements and regulatory measures,
the following additional criteria were applied:
1) Clarity and overall ability to reach policy objectives in terms of both local and watershed-
wide needs; consistency with other local policy and management objectives
2) Breadth of responsibilities and jurisdiction
3) Types of sources included
4) Technical approaches utilized
5) Regulatory inconsistencies and gaps
6) Nature of procedures for exemptions, appeal and issuance of variances
6) Inspection and enforcement considerations
7) Funding considerations
8) Personnel availability
Organization of the Report
The following sections present the results of the evaluation, based upon analysis of
interviews and other documentation, and review of regulatory provisions. Pan I presents
an analysis of regulatory controls and other land use planning authorities available to
communities. General findings are outlined, along with significant findings and
recommendations by category of authority. Appendix I presents an alphabetically
organized set of summaries of authority by community. Citations and brief descriptions of
the authorities, key elements relating to stormwater, and some potential strengths and
limititions are presented.
Part II presents the results of the evaluation of structural controls in place in the
Mamaroneck watersheds, considering three groups of devices and practices. Practices are
described, and considerations important to evaluation, such as maintenance and cost
factors, are briefly reviewed The use and effectiveness of specific practices in the study
communities is described, and recommendations are outlined. The first table included in
Appendix II presents a general inventory of all types of structural practices identified as
being in place in each of the study communities.
Pan m presents an evaluation of housekeeping practices applied in the study
communities. Again, findings from the literature on the effectiveness of practices are
presented to provide a context for evaluation within the study communities.
Recommendations concerning general effectiveness and applicability to Mamaroneck
Harbor water quality restoration are briefly presented. The second table included in
Appendix D briefly inventories housekeeping practices in place in the study communities.
Names and affiliations of all individuals contacted during the research effort are listed in
a brief section which follows the Appendices.
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I EXISTING REGULATORY INITIATIVES AT THE COUNTY AND
LOCAL LEVEL
Introduction
In the late 1970's the Westchester County Department of Health embarked on a three-
year federally funded Section 208 Water Quality Study. Although the 208 program gave
primary focus to sanitary sewerage issues, it also pointed to stormwater as the primary
source of pollutants degrading surface water quality in the southern portion of the county,
and drew clear connections between land use and the impacts of both stormwater and
eroded sediment.
Use of zoning, subdivision and health regulations, land acquisition, and extension of
sewer service areas were all recommended as mitigating measures, in addition to
development of a comprehensive watershed planning framework. In the context of
stormwater management planning, it is appropriate to review the extent to which previously
recommended stormwater-related management measures have been adopted, and to
evaluate the issues surrounding exercise of local initiative.
The limited scope of this evaluation effort cannot accommodate a comprehensive review
of county and local regulatory controls and housekeeping practices. However, a basic
review of initiatives and a discussion of factors contributing to success or failure is
presented.
A. GENERAL FINDINGS AND CONCERNS
1. Role of Westchester County
At the county level, three departments are responsible for specific elements of
stormwater management. The Westchester County Stream Control Law, enacted in the
1950's, was developed specifically for the purposes of floodway protection. Within 100
feet of specifically designated stream boundaries, a permit must be obtained from the
Department of Public Works for proposed construction or alteration. Boundaries were
defined on a stream-by-stream basis by assuming a variable setback (depending upon
stream characteristics) from surveyed property lines along the particular streams.
The stream control program attempts to maintain floodway integrity by establishing
specific construction procedures to be applied in stream corridors. It neither strictly
prohibits development nor includes water quality enhancement objectives, relating primarily
to alleviation of obstruction. A number of factors limit the effectiveness of the Stream
Control Law in addressing floodplain management needs and in providing indirect water
quality control benefits.
First, the designated stream channel areas constitute only a small portion of the total
network in the County, and the statute fails to address such key stormwater management
factors as increases in storm flows, prevention of damages attributable to excessive runoff,
or cumulative effects. Further, the Department of Public Works is not provided authority
to purchase property, to acquire easements, or to implement stream channel modifications.
From the standpoint of water quality restoration in tributaries, expanded authority to
acquire or regulate riparian buffer areas and restore natural pollutant attenuation capacity
would be extremely beneficial. The capacity of natural buffer areas to attenuate coliform
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loadings, in particular, has been demonstrated on Long Island (Long Island Regional
Planning Board, 1982).
The County Department of Public Works also has authority to review development
applications which front on, have access to, or are otherwise directly related to existing
county roads, drainage systems, or county road or drainage hghts-of-way, via S. 239-K of
the General Municipal Law.
The County Health Department input to stormwater management issues devolves from
the authority provided by two sections of the County Administrative Code. Article IX,
Sanitation of Habitable Buildings, directs the Department to ensure that every court, yard,
or other area on the premesis of any habitable building be graded and drained to prevent the
accumulation of water within, or outside of the premesis. The Department must also
approve the proposed method of land drainage prior to any development or sale of a realty
subdivision, according to Article X, Realty Subdivisions.
The County Department of Planning is provided the authority to consult with the staff of
the Soil and Water Conservation District, and to comment on stormwater or flooding
concerns, via the referral process detailed in Article IV of the County Administrative Code.
Although no direct jursidiction over development-related stormwater considerations is
established, departmental reports on specific project referrals may reflect concerns. The
Environmental Management Council (EMC), which operates as an adjunct to the Planning
Department, reviews and comments on all State Environmental Quality Review Act
(SEQRA) referrals. The EMC can also designate County level Critical Environmental
Areas, which are automatically subject to Type IEIS review requirements under SEQRA.
Finally, the Westchester County Soil and Water Conservation District, also operating as
an adjunct to the Planning Department, reviews stormwater-management-related elements
of development proposals in the county, within the scope of memoranda of agreement
reached with specific municipalities. A number of important factors limit the impact of the
SWCD role, however.
Chief among these are the fact that municipal decisions to refer projects are
discretionary, SWCD recommendations are advisory only, and the District is woefully
understaffed in view of the number of requests received. Further, the County Executive
has historically placed priority upon flooding as opposed to water quality aspects of
stormwater management. As a result, considerations of water quality enhancement, aside
from erosion and sediment control, generally appear to be given somewhat less emphasis
by the SWCD than in some other conservation districts. The SWCD role may be
expanded based on results of the ongoing County Water Management Task Force study
findings.
In general, county involvement in the water quality aspects of stormwater management
is somewhat fragmented Particularly if the authorities for protection of Critical
Environmental Areas can be enhanced, nonstructural floodplain management can be
emphasized, and County jurisdiction over water quality can be upgraded, the County could
play a key role in protecting regional resources by requiring stricter consideration of cross-
jurisdictional concerns.
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2. Role of Local Jurisdictions
Background
Through the authority of New York enabling legislation (General City Law S. 20, Town
Law S.361, and Village Article 7, S. 7-700), local governments have considerable
authority over development, land use, and certain public health issues. Zoning and land and
water management controls are critically important in protecting and enhancing watershed
water quality, protecting floodplain storage areas, targeting growth toward areas capable of
sustaining development, and providing support for structural initiatives currently being
undertaken to improve harbor water quality. Several complicating factors, however, have
served to restrict the effectiveness of local initiatives.
In the study area, municipalities are densely developed (virually up to 100 percent in
certain lower watershed communities), have previously allowed extensive alteration of the
floodplains, and have relied primarily on structural controls to mitigate the locally severe
flooding problems. The response to stormwater management is thus constrained by the
problems and limitations of existing infrastructure and by the lack of availability of land to
purchase for flood storage and stormwater treatment purposes.
Fundamentally, opportunites for effective control of stormwater runoff quality are
greatest in newly developing areas where the availability of space for the development of
regional control facilities remains relatively unconstrained. Institutional considerations thus
become very important in managing density so as to minimize sources, and in avoiding
reliance on internalized, structural drainage systems. As the rate of development in
Westchester County has escalated, particularly in the northern reaches, and sources of
runoff have increased, land available for regional detention has dwindled dramatically.
In spite of vigorous effort on the pan of many county and municipal officials, the
general public still has an incomplete understanding of the connections between source
inputs, particularly in the upper watershed, and the condition of Mamaroneck Harbor and
its tributaries. The lack of understanding contributes to difficulties in installing and
maintaining BMPs, eliminating illegal connections to the sanitary sewer system, and
encouraging adequate nonsmictural approaches to flood control.
Stormwater management issues are extremely complex. Recent research results have
documented the consistently high levels of heavy metals, hydrocarbons, pathogens,
pesticides and nutrients to be found in urban runoff in particular, yet traditional stormwater
management concerns have focused primarily on flooding rather that water quality impacts.
As such, technological solutions to flood-protection-oriented stormwater management
measures are firmly established and well understood. Controls providing water quality
enhancement are less familiar on the local level and sometimes poorly understood,
particularly where combined flood control and water quality benefits are to be considered.
Therefore, in spite of an increasingly broad appreciation for the need for joint
management of stormwater quality and quantity, study area communities have moved
cautiously, fearing to involve themselves in technical and financial obligations beyond their
administrative ability. The reluctance to assume financial and administrative responsibility
for facility management is exacerbated by concern regarding potential liability issues.
Institutional Issues and Consistency
All of the study communities have some level of authority to manage stormwater
through land use and/or development ordinances. However existing local programs are
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inconsistent in approach, in the types of stormwater control measures required, and in the
terms of specific requirements from one municipality to another. Among the several factors
potentially contributing to inconsistency are the lack of a comprehensive statewide
stormwater policy (although state guidance documents have been prepared), differences in
the perceptions of problems and impacts in various locations in the watershed, differing
legislative mandates and authorities at the local level, and other factors.
In some cases, requirements are uneven within a given community, due to
incongruencies of mandate among various regulatory instruments, incomplete "coverage"
of all land developing activities within the regulatory definitions, contrasting technical
orientation among the overseeing boards or commissions, seasonal differences in permit
and inspection "load" and other factors.
The inconsistencies result not only in disparate protection of common resources and
public safety from one area of the watershed to another, but also in controls that may
discourage creative and efficient solutions to stormwater management problems.
Communication among local elected or appointed bodies within municipalities is
sometimes incomplete, due in pan to time and staff constraints, as is communication
between community bodies and elements of county government. Boards may be unaware
of other town bodies' policy objectives, may operate under contradictory assumptions, or
may otherwise fail to support closely related initiatives. For example, a town subdivision
rule may require developers to direct storm runoff into stream channels, or to the lowest
available drainage point, while a surface water control ordinance, or strict interpretation of a
wetland protection ordinance, would require installation of detention/retention basins
addressing water quality needs.
Ordinances may also be severely diminished in effectiveness if specific regulatory
language providing implementation responsibility is not incorporated into applicable board
operating procedures and into the regulatory language of related authorities. For example,
building codes would benefit from being upgraded to include or appropriately reference
applicable stormwater provisions and to ensure that the building inspection process can be
brought to bear on the use of structural BMPs as well as other on-lot drainage elements.
Without the authority to address these concerns, building inspectors lack the legal means to
take action on visible problems.
In related situations, elected board members may have little power to ensure that town
policies be internally consistent, particularly where a variance granted by one board may be
appealed to a review body having conflicting or overlapping jurisdiction. Town
commissions are generally advisory only, have little formal coordinating responsibility, and
may have only a limited role in the substance of permit review.
The Westchester County Soil and Water Conservation District is attempting to develop a
county-wide approach to stormwater management based upon watershed management
principles. A key element of the approach is to encourage communities to develop
programs which, at a minimum, ensure cross-jurisdictional consistency within watersheds.
Implementation
In study towns, not all public works departments and municipal boards and
commissions are sufficiently informed and/or sympathetic regarding the objectives and
regulatory necessities of water quality issues in watershed management. Given the
initiatives which study cpmmmunities have underaken to protect surface waters, these
concerns should be serving as a force to encourage imer-jurisdictional consistency.
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Generally, with regard to local regulations, effectiveness is heavily dependent upon a
local inspector's or engineer's interpretation of requirements, hisfter commitment to
ensuring that requirements are strictly met, and the resources and time which are available
to undertake inspections. Some local inspectors and officials have taken their positions
based on familiarity with the building trade, and may need additional training where review
of the water quality enhancement aspects of stormwater management facilities are
concerned, or where soils, vegetation, wetlands, or other natural resource evaluation
elements must be addressed in permit review.
Town engineers and building inspectors may also exercise considerable influence with
regard to the scope and character of local initiatives. Although inspectors are enforcement
officials, and not policy makers, they nevertheless act in an advisory capacity to the local
boards. Boards may rely heavily on an inspector's opinion regarding constraints to
implementation in determining an ordinance's appropriate scope, and in setting
performance standards.
Partly because of the political pressures exerted on town councils to undertake resource
protection initiatives with limited enforcement capability, many town ordinances describe
the purpose of the law and the extent of its jurisdiction, but fail to provide clear
performance standards supplemented by design standards for facility components. A great
deal of discretionary authority thus passes to local officials.
This issue is of particular-importance where the use of SWCD technical standards is
concerned. Although nearly all of the study municipalities have an active memorandum of
understanding in place with the SWCD, the decision to refer a specific project to the SWCD
for review lies with the municipality and recommendations made to the town have no
regulatory force. Only in towns which specifically require adherence to the technical
specifications of the SWCD manual can a strict interpretation be assured. Again, the
demands on the District staff greatly exceed capabilities, requests for assistance having
increased nearly 400 percent over since 1983.
The local special permit and variance granting processes are particularly vulnerable to
the lack of specific standards and guidelines. Most town ordinances provide an appeal
process through which many land use activities may be reviewed by boards of appeals or
other designated authorities. Frequently, the special permit granting authority or appeal
board is an appointed board which does not formally adopt standards or policy guideb'nes
for the issuance of permits. The lack of accepted standards not only inhibits regulatory
accountability, but may allow for unjustified inconsistency in review procedure.
Basically, the extent of variation among town initiatives is quite broad, with regard to
approach and effectiveness. In order to make a comprehensive determination of local
government capabilities in addressing stormwater management, an in-depth analysis of
enforcement capabilities must be undertaken, as alluded to previously.
Staffing
An issue of importance is the constraints which local planning and engineering staff face
in meeting review, inspection, maintenance, and enforcement demands. Several
communities have developed in-house technical planning and engineering support, but
town budget constraints frequently limit staffing capability. In several towns where
interacting flood hazard management and water quality protection issues have created a
critical need for consideration of long-term objectives, and a need for full-time professional
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1 L
assistance in evaluating and implementing alternative approaches, technical staff remains
limited.
Several towns rely very heavily on obtaining detailed technical assistance from the Soil
and Water Conservation District on a regular basis. Staffing shortages at the SWCD do not
lessen the pressure for rapid review "turn-around," resulting in reliance on local staff
insufficiently trained in the complex technical evaluations necessary for effective review of
stormwater management plans.
Limited Exercise of Watershed-Wide Perspective
Despite the efforts of the Westchester Soil and Water Conservation District to promote
watershed-wide approaches to stormwater management, the impacts of incremental
development in one sub-watershed on other municipalities remains insufficiently
considered. Planning board rules of procedure require that adjacent communities be given
opportunities to comment on projects of inter-municipal concern, but no mechanism exists
to enable one municipality to condition permits issued by another.
Although New York State has not yet completed development of a comprehensive
stormwater management policy as envisioned by the federal Water Quality Act of 1987,
certain state regulatory tools could be used more effectively to provide incentives for
structural rehabilitation, to support local initiative and to provide oversight. For example,
general NYPDES permits to be issued to municipalities for storm drain discharges must
cover inputs "contributing" to discharges, giving DEC authority over a range of stormwater
sources identified in the New York State Nonpoint Source Management Plan.
A key concern reiterated by the District Manager of the SWCD is the lack of authority on
the pan of any one entity to review specific project proposals in the context of the
watershed in which they are located. The overall inability to address cumulative effects
hampers the effectiveness of a range of local programs, as in many other areas. In
response, the SWCD is attempting to encourage use of watershed release rate percentage
formulas, which could be designated on zoning overlays. The formulas allow predictions
to be made as to the percentage of runoff which infiltrates versus the percentage which runs
off surfaces directly to drainage systems.
In general, the SWCD has pointed to the serious consequences to be expected when
site-specific decision making on stormwater management creates a proliferation of poorly
maintained facilities, ignores downstream impacts due to channel modification and
sediment accumulation, and obscures the need for management of increasing volume of
runoff as a watershed develops. Only in towns which specifically incorporate a watershed
management perspective can resulting impacts-increased flood damage potential and
degraded water quality-be avoided.
Supporting Role of the Local Waterfront Revitalization Planning Process
In spite of resource constraints, several local governments have extended their
jurisdictions well beyond the authority provided by state regulatory language, particularly
with regard to wetlands protection.
Local governments along the coast which are actively concerned with resource
protection have used the Local Waterfront Revitalization Process, in particular, to promote
consistency among resource protection requirements. With its broad mandate, the
waterfront revitalization process allows communities to address a range of issues related to
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stormwater management, including management of pollutant sources, protection of open
space via density controls, retrofitting of facilities, and harbor management.
Naturally the flexibility of the multiple purpose Local Waterfront Revitalization process,
as well as the broad guidance provided, has supported a divergence of objectives. While
several towns have provided a strict regulatory interpretation supporting aggressive local
action toward resource protection, others, such as Port Chester, have used the process
primarily for waterfront infrastructure revitalization. In addition, the plans are put in place
only in coastal municipalities, limiting opportunities to consider needs on a watershed-wide
basis.
3. Overall Finding: Need for an Interjurisdictional Watershed Management
Program
The Westchester County Soil and Water Conservation District has advocated an overall
watershed approach to stormwater management utilizing a combination of control methods.
As outlined in other sections, the County's proposed approach would involve calculation of
release rate percentages attributable to specific sub-watersheds. By overlaying the release
rate percentage maps on local zoning, the county and municipal governments could assess
cumulative stormwater delivery impacts watershed-wide, and could require that site
drainage practices and stormwater management efforts be adjusted so as to account for
regional needs.
As initiatives in this direction proceed, a number of steps can be taken to enhance the
effectiveness of regional and local stormwater management in meeting water quality
enhancement objectives as well and flood damage prevention needs.
Coordinating Flood Hazard Management and Surface Water Quality Enhancement
A range of options should be considered for establishment of a comprehensive
stormwater management program which gives priority consideration to water quality
rehabilitation needs as well as to flood hazard management objectives. The County's Water
Management Task Force has recently prepared a feasibility study which considers
development of a permitting strategy for stormwater discharge which would also address
erosion and sediment control. The concurrent efforts of other Task Force advisory groups
provide an opportunity to move aggressively toward a coordinated approach.
Regional flood hazard management measures which emphasize restoration of natural
flood storage capacity have been proven most effective in mitigating hazard. The Beaver
Swamp Brook Watershed Management Plan provides an example of such an effort, in
which a watershed model was used to support the siting of proposed regional detention
facilities. Similarly, the use of a regional approach provides enhanced opportunity to
address combined water quality and flood control needs.
In order to make progress toward improvement of water quality conditions, the county
and communities would benefit from establishing clear standards which can be used to
address inter-related water quality and flood hazard management needs throughout the
contributing watersheds. General performance standards, applied in concert with specific
design standards for system components, are recommended.
For purposes of restoring degraded waters in specific tributaries and dealing with soil or
slope-specific sedimentation problems, a permitting program based on watershed
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management could differentiate minimum performance standards according to a phased set
of targets for receiving water quality.
Similarly, standards could be differentiated according to existing receiving water quality
to protect designated resource areas such as the Critical Environmental Areas in place.
These efforts should be coordinated with the state's nonpoint source management program.
To address the severe sedimentation problems in the harbor and its tributaries, a solids
removal efficiency of 85 percent (including suspended fine sediment) is recommended for
existing critical resource areas. For an initial phase of restoration in waters affected by
sedimentation, a solids removal efficiency of at least 70 percent should be considered.
(These objectives are based upon performance standards adopted in New Jersey and New
England states.)
Minimum flood control standards should be rationalized for all communities in the study
watersheds, based upon methods recognizing flood discharge volume as well as discharge
rate. Zones of contribution should be mapped as per the recommendations of the S WCD,
as soon as watershed-specific models can be used to calibrate sub-watershed inputs and
evaluate other factors affecting concentration. Where current rate-based standards are
applied, available estimation measures should be used to approximate volume discharge
factors so designers can calculate to maximize recharge to the extent consistent with
groundwater protection.
Sub-Watershed Evaluations
As documented by the SWCD, the flood storage capacity of many small streams, as
well as the contaminant assimilation capacity of adjacent floodplains, has been lost to
internalized drainage. Diversion of stream flow into poorly designed undersized road
drainage systems and culverts has caused localized flooding in small tributary valleys, due
to altered timing of natural runoff flows. The appropriate jurisdictions should inventory
areas where natural drainage patterns could be restored and floodplains revegetated, or
where drainage facilities could be retrofitted to minimize impacts upon surface waters and
adjacent areas. Development of regional detention facilities, as anticipated by the Beaver
Swamp Brook Plan, should be strongly encouraged.
In the Beaver Swamp Brook watershed study, the Penn State Runoff Model was used
to quantify relationships between land use and water management objectives. Although the
effort gave primary focus to the evaluation of detention options for peak flow timing, the
protection of several important wetland resource areas in the lower watershed was also an
important objective. The coordinated inter-municipal review process anticipated for the
Beaver Swamp Brook watershed can be used to address water quality needs and
remediation priorities, and should be applied to other basin watersheds in a comprehensive
fashion.
In evaluating water quality remediation priorities on a sub-watershed basis in other areas
of the country, a number of models have been applied. While the extent of development in
the study watersheds limits the applicability of models designed for ex-urban areas, many
others have been adapted for suburban and urban conditions, are being refined in
application, and should be considered. Several literature and planning reviews are available
to assist decision-makers in defining needs and evaluating options (Metropolitan
Washington Council of Governments, 1987; Reckhow et al, 1985; U.S. EPA, 1984,1987;
etc.).
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Existing storaiwater discharges into surface waters tributary to Mamaroneck Harbor
should be inventoried and evaluated to assess whether remediation measures can be
pursued. Where sufficient land area exists to develop detention/retention areas or facilities,
sediment basins, or cost-feasible energy dissipation areas, or where easements can be
aquired for those purposes, these alternatives should be investigated and pursued, and
mechanisms addressing both pollution and flood flow mitigation should be installed.
Among direct discharges of concern, priorities ratings for remediation should be set on the
basis of pollutant loading and flood hazard factors.
Performance Standards
Although various stonnwater management authorities are available, performance
standards which encourage consistent adherence to some imponant principles have not
been put in place. The SWCD has stressed the need to protect natural storage and address
concerns of runoff volume as well as runoff rate increases in stormwater management.
Performance standards could be established by the county and municipalities which require
that applicants for new site development address volume as well as rate of runoff in
stormwater management plans.
Stormwater Management Plans
Water quality and flood control benefits may be achieved jointly via a combination of
site design, and structural and nonstructural measures. Stormwater management plans
should be required on all applicable development proposals, with accompanying
maintenance plans where structural controls are to be put in place. The intent of all
stormwater management plans, and the basis for their evaluation, should be to
1) reduce the volume of runoff generated by minimizing the extent of imperviousness,
enhancing overland flow, and maximizing pre-concentration surface infiltration;
2) treat or mitigate pollutant concentrations in runoff transported off-site.
Stormwater management plans should be required for
new plats
applications for subdivision of land
alteration of an existing drainage system
proposals for new development of more than one residential unit on a plat
changes of use which significantly increase the rate oj volume of runoff.
Review of Cumulative Effects
Although a number of groundwater and surface water controls have been broadly
delegated to the county, there is often little specific regulatory jurisdiction over water
resource protection needs at the local level, unless developments are subject to SEQRA (or
to a local analogue) or within LWRP planning purview, due to the lack of a specific
mandate in most municipal codes. Designation of a particular resource area under SEQRA
as a Critical Environmental Area provides some protection, primarily as a method of
requiring full EIS review.
No municipalities in the study area have moved to address the cumulative impacts of
numerous individual projects, except as provided for in local floodplain management
regulations. Because site plan and subdivision proposals affecting the same area are made
incrementally through time, no evaluation of the collective impacts of individual projects is
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made. Use of a sub-watershed-based watershed release rate percentage formula, as
advocated for the Beaver Swamp Brook watershed, would accommodate considerations of
cumulative flooding impacts. A complementary formula should be developed for
consideration of water quality impacts.
The following method could be considered in preparing a strategy for evaluation of
cumulative effects. They are based upon a procedure used to implement a local
Massachusetts regulation which has been in place for six years for the purpose of
cumulative impacts evaluation.
Identify developments requiring submission of a cumulative impacts evaluation (e.g., if a
portion or all of the proposed development lies within the watershed or zone of contribution
of a freshwater or coastal pond or embayment or a public water supply well (existing or
proposed)).
Integrate with other local environmental review procedures.
Establish criteria for determination of cumulative impact (including, for example,
determination of the contaminant loading of the proposed subdivision and a comparison to
the carrying capacity of the receiving waters, and setting forth the probable impact or effect
of the proposed subdivision on the receiving waters (ground or surface) over a period of
time, assuming completion of the maximum level of development proposed).
Develop methodology for analysis of contaminant loading to the groundwater or to other
receiving waters impacting the town's or region's Critical Environmental Areas.
Identify state or federal performance standards which must be applied in preparing an
analysis of the existing condition of the affected water body or supply, and the expected
change in the condition of the water body or supply as a result of the proposed
development
Establish methodology to be appb'ed in comparing, on a per-acre basis, the contaminant
loading from the proposed development with a) the existing and potential loading from all
other developments and acreage within the recharge area of the water supply or water body,
and b) the loading rate which would be expected to produce critical bacterial levels or
eutrophic levels or exceed applicable water quality standards in a water body.
Devise measures to reduce contaminant loading if per-acre loading rates from the
proposed development will equal or exceed the critical loading rate when combined with
existing and potential development within the water body's tributary area.
4. Other Recommendations to Enhance Effectiveness of Existing
Regulatory Measures
Administration
Attachment of permit conditions as deed encumbrances, and the referencing of EIS
findings in county records could be an extremely useful mechanism to provide continuity
of review and enforcement, and to enable permit reviewers to evaluate cumulative effects.
The fact that all county property transfers are computerized and computer-retrievable means
that inspections conducted at property transfer could be tracked through time to ensure
consistent maintenance and enforcement.
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1 7
Procedures of municipal highway departments, departments of public works, sanitation
departments, and other applicable service and maintenance departments should be revised
to ensure that procedures and practices of these departments are, at a minimum, consistent
with the technical requirements and recommendations of the SWCD concerning design and
installation of best management practices, and maintenance and repair of facilities.
Communities should consider adopting formal standards and policy guidelines clearly
defining permit review procedures, appeal review procedures, and procedures for granting
variances, area zoning variances, and special exceptions. These standards, and procedures
for public notification, should be included in applicable municipal codes.
Municipalities would benefit from ensuring that the staff resources dedicated to
inspection and enforcement (including environmental coordinators, staff of building,
planning, and engineering departments and coastal zone management commissions) grow
proportionally with the development or re-development activity in the town. This is
particularly true at the present time in upper watershed areas, as development pressure is
increasingly forcing activity into marginal lands. The pressure on marginal land is expected
to increase. Dedicated permit fees, land transfer assessments, fines collected as a result of
enforcement actions, etc. could be used to fund additional staff posinons.
Technical Needs
Inland communities which have not participated in the LWRP program should consider
undertaking a similar environmental review to support evaluation of community land use
and water quality remediation objectives, and in-depth assessment of available resource
protection programs. An inventory and review strategy could be pursued which would
support broad planning objectives, including revision of the town Comprehensive Plan,
revision of related town ordinances, adjustment of zoning policy, etc., as needed to ensure.
at a minimum, compatiblity with a watershed-based management strategy and consistency
with defined resource protection policy.
Using the results of the environmental review, communities should undertake an
assessment of existing ordinances, municipal policies, and other control mechanisms to
determine whether allowable land uses, densities, and municipal practices are compatible
with current knowledge of water quality protection needs in Mamaroneck Harbor and
proposed strategies for management of stormwater on a watershed basis.
Communities which have prepared similar evaluations as an element of the LWRP
program should consider malting an assessment of progress in reaching articulated policy
objectives, as well as regulatory considerations which might be appropriate in adapting
consistent inter-municipal controls which could be applied to unified watershed
management
Until such time as a watershed management approach can be implemented, communities
should cross-reference ordinances, regulations and procedures to improve internal
consistency.
Municipalities should consider forming watershed-wide water resource protection
advisory committees to advise planning boards of the member towns on development
within the watershed. Development proposals could be reviewed by the committee, and
findings and recommendations would be reported to the municipal body or bodies having
jurisdiction.
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B. EVALUATION OF SPECIFIC REGULATORY BMPS
1. Zoning
Under the New York State enabling legislation, towns have authority to establish land
use provisions and to set use restrictions by district Lot sire, shape and dimensions,
allowable density of structures, frontage requirements, parking and height stipulations and
allowable use are all established via zoning regulations. Municipal zoning and permit
conditioning can prove extremely important in control of nonpoint pollution.
Given the fact that zoning regulations enable municipalities to consider land use
suitability and compatibility of use, districting may be used to preserve certain uses or
aspects of community character (e.g. riverways, historical areas, fishing villages), to
reserve areas for a potential use (such as water supply), or to prevent irreversible trends
which limit opportunities for further public consideration (protection of open space).
Temporary building moratoria may be imposed while consideration is given to the long-
term objectives of zoning policy and proper implementation methods.
In addition to the three general zoning types in place in mosi towns (including
residential, commercial, and industrial), certain towns have established special districts in
which additional development criteria and stipulations are imposed. Other elements of
zoning authority which can enable towns to address stormwater management issues include
use of zoning to allow clustering, lot grouping, or planned unit/planned residential
development (in which reduced lot sizes are allowed in exchange for open space set-
asides).
In terms of stormwater impacts, development density is related to management of flood
hazard (re timing and magnitude of local and regional impacts), aquifer recharge potential,
management of urban runoff contamination potential, lawn-care-related pollutant loading,
and delivery of discharge to sewers subject to hydraulic overloading.
Zoning ordinances can address stormwater management issues by establishing
procedures and terms for site plan review, defining allowed land usage, setting minimum
lot sizes, and specifying allowable percentage of impermeable lot coverage. In addition,
communities can impose stormwater management standards on development of single lots
via site plan review. Other mechanisms available for review of stormwater management
requirements include "change of use" petitions and permitting processes set up to
implement building codes. Requirements can thus be applied consistently to developments
not covered by subdivision/land development ordinances or within the jurisdiction of
resource protection rules.
As is the case with other regulatory authorities, use of zoning authority to address
stormwater management objectives is inconsistent across study municipalities, particularly
with respect to surface water quality protection. While most apply density restrictions, the
degree to which the zoning provisions reference or complement other stormwater-related
regulations differs broadly.
Harrison and the Village of Mamaroneck. for example, complement density controls via
erosion control and subdivision regulations, while Rye has in place a surface water control
ordinance, strictly controls development in floodplains via the local floodplain management
ordinance, and has down-zoned to preserve flood storage capacity in certain areas. White
Plains uses the zoning ordinance to require that a percentage of usable open space be
maintained or created in the case of redevelopments.
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A number of techniques now in use elsewhere in New York, including planned
residential developments (PRDs), density transfers, clustering, lot averaging, and
performance zoning, can be incorporated into zoning ordinances to encourage protection of
open space, efficient provision of utilities and services, improved floodplain management,
and enhanced use of the pollutant assimilative capacity of natural systems.
Where development can be concentrated on suitable portions of a site, more space can
be made available for groundwater recharge and recreation, as well as for installation of wet
detention ponds and other BMPs providing water quality as well as flood hazard
management benefits.
Although PRDs are provided for in most communities, use of other techniques is
uncommon, partly due to public misunderstanding as to the effects of these techniques on
overall density. Lack of recourse to such techniques has contributed to the inefficient
proliferation of on-site BMPs discussed in other sections. In several study communites
BMPs are shared among landowners in condominium or subdivision developments, but no
off-site cooperatively owned BMPs were mentioned by the officials contacted.
Where review mechanisms relating to watercourses are in effect, they are less oriented
toward restoration of natural floodplain values and pollutant buffering capacity than toward
stabilization of waterways as stormflow channels. In Harrison, for example, a required
50-foot setback for brook protection does not prohibit construction, but can provide for
engineered bank stabilization.
Permit sequencing may also pose problems. Most zoning ordinances do not specify thai
an applicant must obtain all floodplain, erosion/sediment control, wetlands, and other
permits prior to issuance of a building permit or zoning use permit. As a result, some
construction-related requirements are improperly or tardily installed, or may be omitted if
inspectors are unaware of applicability.
Water resource protection criteria are not generally applied to zoning variances.
Although a range of qualifications are considered (including practical difficulty or hardship
in compliance), legally established criteria generally fail to address water resource impacts.
Area variances may be especially important with respect to stormwater control, as issues
concerning density, proposed setbacks, and placement of structures on properties are
addressed.
Zoning boards of appeals (ZBA) are not routinely required to submit zoning variance
proposals for review by the municipal planning boards or advisory bodies such as
conservation commissions. Policies of other municipal bodies and applicable case law
should be completely reflected in ZBA decisions.
Appointed ZBA members may be insufficiently aquainted with state and county law to
assess whether a proposed development and zoning variance request is compatible with the
New York Compilation of Rules and Regulations, SPDES regulations, and DEC nonpoint
source management policy.
As discussed in other sections, zoning maps and maps delineating special overlay
districts should reflect watershed release rate percentage formulas as soon as these are
available.
Zoning maps and overlays should be prepared which indicate areas of particular concern
in addressing stormwater quality. The maps should locate the factors investigated in the
comprehensive environmental review (recommended in the previous section General
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Recommendations) and should assign ratings with respect to vulnerability to runoff-borne
contamination.
These maps should reasonably draw upon (and be consistent with) available engineering
master plans, facilities plans, flood designation maps, SCS soils maps, etc., but should
clearly illustrate results of the inventories undertaken within the scope of the environmental
review. The maps should be prepared at a scale sufficient to make them usable in public
presentations, but should also be reducible for use as public education tools.
Local officials and permit reviewers could then use the maps in several ways to protect
resource areas from the impacts of stormwater. First, via establishment of special runoff
impact protection districts on a watershed basis, uses which could potentially impair the
viability of integrated hydrologic systems could be restricted. Alternatively, the maps could
be used to ensure a coordinated review of all applicable permits within and across
municipal boundaries.
Protection of open space is critical in managing flood storage capacity, recharging
groundwater aquifers, and allowing natural assimilative mechanisms to treat stormwater-
borne contaminants. Larger private holdings which have long performed these functions in
upper-watershed portions of the study communities are now being sub-divided. The Long
Island NURP identified medium-density residential development as the land use
classification contributing highest coliform levels to receieving waters. Communities
should consider down-zoning these open areas to limit escalation of water quality impacts.
Communities should consider adjusting zoning density generally to specifically consider
cumulative impacts of development-related resource cpntaminaoon so as to be consistent
with public health protection objectives. Zoning provisions should also reflect known
siting limitations and those identified in the advocated environmental review, by
environmental impact statements, and in other research on the carrying capacity of the
resource base.
2. Subdivision and Land Development
Under the authority of the General Municipal Law, planning boards are required to
adopt ordinances pertaining to land on which new roads are being built to obtain access to
one or more lots lacking adequate frontage. Generally such ordinances and regulations
provide standards for the site improvement specifications established by the municipality
(construction of roadways, utilities, curbs, sidewalks, and other aspects of road, street,
and building layout, including drainage and construction specifications). In certain
instances, subdivision ordinances may also have jurisdiction over condominium
developments, commercial developments and/or industrial developments as well as
residential areas.
By establishing drainage stipulations, subdivision regulations govern local quantities
and patterns of surface and sub-surface flow, and can reference flood control and hazard
mitigation measures. Thus, water quality impacts of runoff and erosion can be
significantly affected by the emphasis of these regulatory instruments.
Unfortunately, subdivision regulations in the study communities may be contributing to
runoff problems by requiring features such as wide streets, curbs, piped drainage, double
sidewalks, and paved driveways, all of which retard groundwater infiltration. In addition,
most regulations require that runoff be collected in storm drains and directed to the nearest
surface water channel, a practice which limits recharge and can exacerbate downstream
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flooding potential. In general, internalized drainage contributes to watershed hydrological
modification, and speeds the transport of runoff-borne pollutants to receiving waters.
The SWCD (1984) cited dramatic increases in runoff volume since the 1960's. Although
storm drainage has long been in place in the study communities, amendments to some
provisions of the subdivision ordinances could mitigate both the flow volume and the
concentration of pollutants in stormwater runoff.
For example, subdivison ordinances generally do not require that developers maintain
existing topography or preserve natural drainage patterns, even in areas where sensitive
resources may be affected. Although natural vegetation can reduce stormwater flows and
pollutant loadings, most subdivision regulations do not restrict disturbance unless specific
reference is made to critical areas. Vegetation must generally be restored as per the
landscaping provisions of site plan review, but few communities have authority to require
restoration of buffer areas or to stipulate that specific plant materials be used. None of the
study area ordinances limit the size of lawn area, although pesticide and nutrient loadings
from turf may be significant.
Most subdivision ordinances require that 60-foot rights-of-way be cleared in all
subdivision developments irrespective of anticipated traffic volume, site topography, or the
consequences in terms of runoff generated.
Subdivision proposals in the study area are reviewed with reference to the SWCD BMPs
for stormwater-related activities, at least in practice, but specific technical stipulations are
not generally included in the ordinances themselves, and the BMP requirements are often
not formally referenced. As a result, technical guidance with respect to flood hazard
management may be incomplete.
With respect to water quality concerns, the lack of criteria and standards for review has
even larger consequences except where the proposed activity must be reviewed under
SEQR, a local analogue, or another local conservation rule such as the City of Rye's
Surface Water Control ACL Without sound specifications that can be used to address
cumulative hydrologic impacts and incremental contaminant loadings to the watersheds,
municipalities are hampered in their efforts to reach local and inter-municipal water duality
objectives. 7
As discussed in the previous section on zoning, permit sequencing can create difficulties
if a building permit is issued for sites within a subdivision after the final planning board
plat approval, but before mitigating measures required during the site planning process can
be put in place.
These concerns having been raised, some study communities are using drainage design
controls to address stormwater pollution loading factors, directly or indirectly, by requiring
installation of detention basins, grease and oil traps, gravel driveways, emplacement of
drywells and sedimentation basins, etc.
Certain municipal regulations restrict building on steep slopes, require protection of
natural vegetation, and other means of retarding runoff. A recent amendment to the
enabling act governing local subdivision ordinances specifically includes securing
"adequate drainage and provision of erosion controls to mitigate stormwater runoff" among
the purposes of subdivision rules and regulations.
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3. Site Planning
Several towns have used the site plan review process to establish control over drainage
and stormwater runoff, in a manner which can be applied to address both water quality and
flooding concerns. Site plan review, when rigorously and consistently applied, can be an
effective and flexible tool in control of stormwater impacts. In addition, the SEQRA
process and local environmental quality review acts require that the site planning process
serve as the means of coordination to ensure that mitigating measures required by an
environmental impact statement are
incorporated into designs and carried out
Most of the study communities rely heavily on the site planning process to review flood
hazard management needs and implement many of the BMPs recommended by the SWCD.
As with enforcement of EIS mitigation requirments, and subdivision permit review, a great
deal depends upon the smooth, accurate and coherent functioning of many pans of the
process, and there may be numerous opportunities for elements to "fall through the cracks"
in important ways.
Because of its flexibility the site planning process leaves much open to the interpretation
of local officials. A complex review process involving town highway, engineering, traffic,
building, and planning departments, as well as environmental coordinators and various
commissions may be difficult to coordinate internally and with SEQRA where applicable.
Sequencing approvals and revisions may be difficult, particularly with repeated
submissions or controversial projects.
Due to lack of staff expertise and availability in some of the study towns, considerable
reliance may be placed upon the developer's consulting engineer to identify major
environmental impacts as required by the environmental quality review acts, and to ensure
that building contractors build structures to the specifications defined in the plans. Often
the designer never reviews the actual construction, even where complex stormwater
management structures are put in place. Several town inspectors arriving separately on a
site to inspect the installation of various facilities may have little opportunity to review
construction elements outside their particular jurisdictions. Only Rye Brook has put a fee
system in place which allows the Village to engage its own consultant for review of plans,
with fees paid for by the applicant.
As is the case with subdivision review, after issuance of an occupancy permit, a
municipality loses considerable leverage with regard to insuring proper installation of
control measures. Several towns in the study area withhold occupancy permits, but in
some cases temporary certificates may be issued conditional on an applicant's promise to
comply with the site plan in the future. Compliance becomes difficult to enforce, as most
stormwater control measures remain in private ownership.
4. Building Codes
Because many stormwater mitigation measures can be considered pan of a structure and
its building systems, building codes should set out or reference all standards for
structurally related stormwater management techniques, and for measures addressing water
quality. Cross-referencing to relevant regulations can also ensure that all developments, re-
developments, and alterations comply with applicable stormwater regulations and that
building inspectors can review specific aspects of BMPs while undertaking inspection
activities.
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« J
Building codes can also be used to ensure that a change in ownership from a developer
to a subsequent owner or builder does not affect compliance with the original stormwater
management elements of a site plan. Building codes should require that a site's stormwater
management provisions be reflected in altered building plans, or that new plans be
submitted for approval.
Although the basic state building code may be expanded upon and updated by
communities, many building codes echo subdivision regulations in requiring that runoff be
directed via piped systems to watercourses. These stipulations are inconsistent with
watershed management principles, or with the need to encourage maximum infiltration on
site to the extent consistent with groundwater protection needs. Building codes, like
subdivision regulations, should be examined to ensure that they emphasize on-site control
of volume as well as discharge rate, and that water-quality-related principles and
requirements are complied with.
Communities need to ensure that building inspectors have sufficient staff assistance to
enable them to meet their responsibilities in monitoring compliance with local stipulations.
5. Erosion and Sediment Control/Earth Removal
In many states, earth removal is regulated under home rule zoning powers, for the
purpose of conserving natural resources and ensuring appropriate use of land. Because
earth removal operations may impair the natural filtering capacity of vegetation and soils,
ground and surface water quality may be significantly impacted. Allowable depth to water
table, maximum slope, revegetarion, and other erosion control requirements may also be
included as stipulations. Although construction activities and agriculture are sometimes
exempted from a range of the provisions, earth removal regulations may also address
nuisances such as dust, noise, traffic, and erosion-inducing activities.
The Westchester County Soil and Water Conservation District prepared a model
ordinance for sediment, erosion, and flood control which specifically references the SWCD
Best Management Practices Manual for Construction Activities. Recommended techniques
include soil stabilization practices, design specifications for sediment basins and traps,
contouring techniques and other methods.
Although a few of the study towns, such as the Village of Mamaroneck and the Town of
Harrison, have enacted erosion and sediment control ordinances, most impose erosion
control practices via the site plan review process. Officials stated generally that SWCD
BMPs are applied as a matter of practice. Erosion control plans are required in Rye, which
references the SWCD BMP manual in its subdivision and surface water control regulations.
Most communities simply require that proposed measures be identified on site plans fen-
review and inspection purposes. Nearly all of the communities require the use of silt
fences and screens, hay bales, and sediment traps. Temporary sediment basins may be
required depending upon site topography. Use of diversions, filter strips, and energy
dissipation techniques are not generally required. Only the Town of Mamaroneck officials
stated that retention/detention devices were in place to capture construction-related runoff
perse.
Rye Brook and Rye inspect erosion control BMPs on site prior to the outset of any
construction activity beyond groundbreaking. Other towns did not mention inspecting
erosion control practices outside the regular inspection schedule for footing, framing,
plumbing, utilities, back-fill, etc.
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Revegetation requirements vary broadly, but are generally handled through the
landscaping provision of site plan review or through the subdivision regulations. ScarsdaJe
stipulates that vegetation and topsoil be replaced in accordance with a required restoration
plan. White Plains requires revegetation, and can stipulate plant materials to be used. In
most communes use of native vegetation versus turf is a matter of negotiation. Rye Brook
restricts removal of topsoil. In most towns officials stated that builders stockpile soil for
on-site landscaping purposes.
Given the severity of erosion and sedimentation problems in the watersheds, inspection
and restoration planning and procedures should be up-graded. Again, lack of funding and
inspection personnel at the local level do not enable officials to monitor conditions
optimally. Officials stated that many problems are discovered outside the regular inspection
process, during the performance of other activities in an area.
As stated in related sections, site plans for erosion and sediment control and restoration
plans should incorporate other permit conditions and stipulations so that building inspectors
and other officials could ensure compliance. In order to expand inspection capability,
building permit fees should be based on the combined cost of the building itself and the
erosion and sediment control facilities. Bonds and letters of credit should establish erosion
and sedimentation BMP maintenance responsibility.
To ensure that municipalities themselves are conforming to recommended practice,
procedures of the municipal highway departments, the departments of public works, the
sanitation departments, and other appb'cable service and maintenance departments should be
revised to specifically incorporate or reference the applicable SWCD BMPs, at a minimum.
Language should refer to erosion and sedimentation control, design and installation of best
management practices, and maintenance and repair of facilities.
Earth removal is regulated in a variety of ways in addition to general landscaping and
site plan provisions; within specific excavation and regrading permit processes (e.g.,
Harrison, Rye Brook), through building codes (e.g., White Plains, Village of
Mamaroneck) through excavation and fill permits under the zoning code (e.g., Port
Chester) and through resource protection ordinances (Rye).
Communities having specific excavation permit processes impose erosion control
conditions, although SWCD BMPs may not be referenced in the ordinances. No study
communities set a maximum depth from the seasonal high water table for earth removal.
Some, but not all, set grade and slope restrictions. Slope is generally set to the natural
angle of repose of the material.
According to officials interviewed, most earth removal ordinances were put in place to
regulate large-scale sand and gravel removal. Routine building excavations are generally
handled via site planning. To regulate earth removal in a manner complementary to erosion
and sediment control provisions, applicable provisions of the various ordinances should be
amended to require that erosion control measures as recommended by the SWCD be put in
place and maintained during the full course of earth removal and site restoration operations.
Maximum grade, learning (topsoil replacement) and planting and seeding requirements
should be established as recommended by the SWCD for excavation operations and
maintenance of sites following earth removal. In areas where groundwater contamination
may be of concern, maximum water table separation requirements should be put in place.
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6. Other Regulatory Tools
The study communities have a number of resource protection tools in place which can
provide valuable local authority in addressing water quality aspects of stormwater
management. These include local wetlands protection ordinances, environmental
conservation laws, surface water control measures, local analogues to SEQR, floodplain
management and flood hazard protection ordinances, coastal policies established via the
local waterfront revitalization program, vegetation or topsoil protection ordinances, and
ordinances related to water supply protection.
Local freshwater and tidal wetland protection ordinances have been used to increase
local regulatory jurisdiction well beyond 12.5 acre jurisdiction provided by the state. The
Village of Mamaroneck regulates disturbance of wetlands down to 1/4 acre in size. Several
communities have mapped wetland areas to improve upon the accuracy of the county 208
maps and FEMA FIRM maps. The Village of Mamaroneck has designated all wetlands as
critical areas. Local dredge and fill rules and environmental conservation laws regulating
alteration of natural features are also applicable to control of discharges of runoff-borne
pollutants to coastal areas.
The local wetland protection ordinances establish bordering areas (generally 100 feet),
within which activities are considered to affect the wetland resource and are regulated. The
extent of alteration allowed varies from community to communty. The Town of
Mamaroneck negotiates restrictions on activities within the jurisdictional boundary, while
Rye and Scarsdale have established a no-impact buffer area.
The chief weaknesses of certain of the wetland protection ordinances are their lack of
precise stipulations, and the fact that activities in areas adjacent to the designated "area of
influence" may be difficult to control. For example, pesticides and fertilizers may be
carried into fragile areas by stormwater, as may road salt or other highway-associated
contaminants, and sediment. In its LWRP, the Town of Mamaroneck attempted to address
these concerns by proposing to designate a golf course bordering a marsh as a critical area
in itself, with the objective of increasing municipal control over activities affecting the
resource area.
The communities which have participated in the New York Dept. of State's local
waterfront revitalization program have used the process to designate resources and
geographic areas of concern. The LWRPs have provided a forum in which participating
communities have attempted to comprehensively review local resource protection needs,'
within and across municipal boundaries. Regulatory and planning capabilities and needs
have also been analyzed, in view of clearly defined state and local objectives. Several
communities have made a great deal of progress in amending and revising local regulatory
authorities to conform to specific policies and regulatory review agendas set out in the
LWRPs.
Rye, for example, used the LWRP process as a means to propose new zoning districts
(waterfront districts, recreational districts, conservation districts), to propose new
requirements for natural vegetaitive ground cover, and to specify that best management
practices should be used to control certain nonpoint source pollutants.
The LWRP process enables communities to set up administrative mechanisms for
coordinated review of projects and activities in the coastal zone. Coastal zone management
commissions and review commissions have been established to provide advisory input to
town boards on project consistency with the LWRP, and to undertake studies and analyses
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of specific technical problems, among other functions. Unfortunately, the coastal zone
review commissions have only advisory authority and cannot impose project conditions
without the cooperation of the lead authority.
The City of Rye uses the authority available under its Surface Water Control Act to
regulate a variety of stormwater-related impacts, including grading, excavation, removal of
vegetaion, and flow alteration. The City has also proposed to incorporate county
regulations protecting fish and wildlife habitat into its subdivision regulations.
Local flood damage prevention laws provide another avenue from which to address
stormwater quality concerns, in that towns have the authority to restrict development in
floodplains and floodways. Most of the study communities have floodplain management
rules in place, and use them to esablish floodpropfing, storage displacement, and grading
requirements, but the role these ordinances play in stormwater qualify management is
limited.
Because many of the floodplain areas in the watersheds are heavily developed, the
opportunties to direct new development out of the floodplains, or to restore natural flood
storage capacity, are limited Further, certain communities have encountered legal
difficulties in enforcing the regulations in areas where lots were platted before the advent of
the National Flood Insurance Program. Scarsdale has such a case in court at the present
time. Flaws in the national program weaken it as a mechanism to support relocation of
repeatedly flooded property owners, limiting options to undertake a large-scale program to
restore natural vegetated floodplains, which could provide flood storage and stormwater
filtering mechanisms.
With regard to SEQRA, several communities have designated Critical Environmental
Areas, which are automatically subject to Type IEIS review requirements. Most of the
study communities also have local environmental quality review acts in place, although Pon
Chester recently abolished its authority as "duplicative" of the state program. The Critical
Environmental Area Designation process should be strengthened and clarified so that
effects of urban runoff and other nonpoint pollution sources on inter-related natural
systems in the watersheds can be considered in a cohesive manner.
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27
n STRUCTURAL BEST MANAGEMENT PRACTICES
A. GENERAL FINDINGS AND CONCERNS
Background
Unless properly managed, stormwater runoff rates and volumes are accelerated due to
watershed development. Watershed alteration also increases flood flows and velocities,
reduces groundwater recharge, contributes to erosion and sedimentation, stresses the
carrying capacity of natural and manmade waterways, and contributes to the incidence of
damaging downstream flooding.
In the watersheds contributing runoff to Mamaroneck Harbor, historical development
patterns, a traditional reliance upon structural flood control methods, and use of
internalized (piped) drainage have resulted in severe hydrolpgical modification. To prevent
stream bank erosion and channel scouring associated with increases in the 2-yr, 24 hour
frequency storm event peak discharge rate and runoff volume, channels have been rip-
rapped and stabilized. Nuisance flooding associated with similar increases in the 10- or 25-
yr frequency storm event has until recently led to a nearly exclusive reliance on internalized
drainage. The storm and sanitary sewer problems are currently being addressed.
More recently, stormwater control measures have been adopted by local communities in
response to concerns about escalating localized flooding problems, particularly in the
Village of Mamaroneck and Town of Mamaroneck. Although the measures have been
adopted with the guidance of the SWCD, the County has no authority to require
consistency among measures from community to community, possesses no regulatory
power to impose a watershed-level review structure, and has no oversight authority in
implementation. As indicated in previous sections, municipal controls are inconsistently
appb'ed from one municipality to another.
Focus on Flood Hazard Management
As discussed in Pan I, except for specific practices required on properties affecting
critical areas, the vast majority of the BMPs presently being put in place are designed to
meet flood hazard management objectives. Most local controls are designed to prevent
increases in flooding for the 2-yr, 24 hour and 25-yr, 24 hr frequency storm event on
individual properties, with provision for prevention of 100-yr storm event flooding in
subdivisions or on larger parcels. Because the structural integrity of stormwater
management facilities must be capable of withstanding the discharge from the 100-yr, 24
hour storm event, and because of the significance of downstream impacts related to timing
of concentration, several communities require control of the 100-yr storm event peak
discharge on-site as a matter of practice.
All of the officials interviewed stated that BMPs in place were designed for flood control
purposes, but that little emphasis is given to reduction of flow volume from a site in spite
of the SWCD's expressed concerns on this issue. Most of the municipal engineers
interviewed were of the opinion that volume increases due to increased development were
"inevitable" and that the best option was to restrict flow rates. Nevertheless, there seems to
be a growing appreciation of the need to coordinate release rates within watersheds,
particularly in the Beaver Swamp Brook watershed communities.
This understanding could be built upon in developing a watershed approach to water
quality concerns. The need to establish water quality oriented controls presently appears to
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be well understood on a site specific basis among some municipal bodies. For example,
water quality concerns were articulated regarding highway runoff to critical areas and
potential impacts of the proposed Corps of Engineers diversion of the Sheldrake on Harbor
pollutant concentrations. Given the success which some of the watershed communities
have had in getting innovative stormwater controls in place, there seems to be much
opportunity to increase understanding and expand focus.
Implementation
Experience with structural best management practices in the study communities has been
variable, both in duration and outcome. Harrison has required installation of detention
facilities for the past eight years, but most of the communities have had similar BMPs in
place for only about two years or up to a maximum of five. As such, experience with
inspection problems, long-term integrity, effectiveness, and maintenance needs and
problems is just now developing.
As outlined in Pan n and reflected in the Appendices, inspection authorities and
methods vary considerably, and may represent a critical element in the attainment of
objectives. In most cases inspection duties are apportioned among several departments or
individuals, and problems may be revealed by accident or may escape notice. In some
municipalities such as Scarsdale, the Village has no right of access, and the applicant's own
engineer must inspect construction and certify compliance.
On-site verification of as-built drawings is required in White Plains and Rye (which
requires as-built photographs). In these communities, as-builis must be re-submitted until
they meet specifications. The Town of Mamaroneck engages its consulting engineer to
perform on-site verification of volume calculations in stormwater storage facilities. In Pon
Chester, the building inspector completes as-built drawings for comparison to site plans.
Unfortunately, as-builts may not be completely verified in some towns, due to a variety
of factors including lack of staff and financial resources and, perhaps particularly where
stormwater facilities are concerned, insufficient technical expertise. Many municipal
responses appear to be based on complaints from neighbors.
Where municipalities lack accurate data on the actual, as opposed to the conceptual,
configuration of stormwater management BMPs and facilities, maintenance difficulties may
become hard to anticipate, and satisfactory performance virtually impossible to achieve.
Proper installation of simple stormwater BMPs, to say nothing of more complex facilities,
is therefore extremely important. Clear, consistent performance standards need to be pur in
place at the community level, and should be complemented by component design standards
where the functioning performance of specific required elements has been well established.
Lack of clarity in these areas can make performance of stormwater BMPs quite vulnerable
to poor installation.
Maintenance of stormwater facilities, particularly on private properties, is becoming an
increasing concern in the watersheds tributary to Mamaroneck Harbor as more small on-site
facilities are developed Experience thus far appears to be quite mixed, depending upon the
community in question, the type of BMP at issue, ownership, visibility, and other factors.
White Plains, for example, has had considerable difficulty keeping dry detention ponds in
certain areas maintained, while Rye Brook and Harrison have not had similar problems.
Wet detention/retention ponds, on the other hand, do not appear to be causing significant
maintenance problems, although sediment has diminished the capacity of one in the Town
of Mamaroneck. In fact wet ponds are viewed as "taking care of themselves" in most of
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the study communities, perhaps partly because of the amenity value which they have for
owners and neighbors.
Although a great deal of data is available regarding methods to design for reduced
maintenance, most officials contacted did not mention this aspect as a factor in review of
designs. In some cases, however, choices among different required BMPs are made on the
basis of anticipated maintenance problems (e.g. discouraging use of porous pavements, dry
wells, gravel driveways, leaching catch basins).
None of the study communities require submission of maintenance plans and schedules
or have specific criteria establishing minimum maintenance frequencies, although most do
require that ownership be fully clarified. Similarly none were identified as having specific
regulatory definitions of "failure" for BMPs required, or standardized regulatory
specifications for repair. As more facilities are developed, these management and
regulatory tools will become increasingly important.
Communities have had mixed success in using performance and maintenance bonds to
ensure adequacy of construction and upkeep. Rye requires 90 percent bonding/surety and
10 percent cash in general, and, like other watershed communities, has had difficulty
collecting bonds and tracking down poorly rated bonding companies. As a result, a
different procedure has been developed for its Surface Water Control Act (SWCA).
Although its bonding authority under the SWCA calls for cash bonds of up to $5000, the
City prefers to do remedial work and backcharge the applicant.
Change in ownership from developer to developer has complicated the bonding and
maintenance issue in more than one community, especially where individuals subdivide lots
and sell to separate developers. Although Harrison has had success in requiring previous
owners to subdivision performance bond conditions, Rye and Scarsdale officials stressed
the need to insist that individual lots be tied to overall subdivision bond provisions.
The authority to do work and back-charge, even on private properties, is available to
most of the study communities, but "emergency" conditions may be required, as in Rye.
Because dealing with homeowners' associations in assigning responsibility may be
problematic, several towns such as White Plains and Port Chester prefer to impose a
schedule for required repairs and then place a lien on the property.
1. Overall Recommendations to Enhance Local Enforcement Capabilities
As stated in Pan II, a detailed inventory needs to be made of facilities in place, design
elements, history and condition, and other factors, so that towns can learn from existing
practice and can develop clear policies and priorities. The criteria applied by the State of
Maryland in undertaking similar inventories could serve as a model.
Communities should carefully consider maintenance needs in evaluating designs and
stormwater management plans. To monitor sediment accumulation and other aspects of
performance, it is recommended that observation wells and other monitoring devices be
installed and records kept by the municipality as well as by the owner/operator.
Individuals and entities responsible for maintenance need to be clearly and formally
identified, appropriate agreements should be reached with owners, and maintenance
schedules and plans need to be prepared for the life of all stormwater facilities. The plans
should be based upon specific municipal criteria establishing minimum maintenance
frequencies and definitions of failure. Cleaning, mowing, sediment removal, re-planting,
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re-grading, replacement of components and other necessary procedures need to be
included.
Virtually all study communities should consider increasing permit application fees
and/or review and inspection fees. Only Rye Brook collects a substantial review fee that
can be drawn upon and expanded until the Village's own independent technical review can
be satisfactorily completed. Local staffing levels and technical expertise need to be
expanded in order to meet existing demands, and need to increase by an additional margin
to address water quality enhancement aspects of stormwater management.
Municipalities might consider requiring project applicants to submit an anticipated
construction schedule along with other review materials, so that elements of stormwater
management facilities can be inspected effectively. (See also specifications for Plans in
Part ID
Procedures need to be developed for long-term municipal inspection of facility function
and appearance. Specific schedules could be set up for inspection of different BMPs (e.g.,
annual inspection of basins, semi-annual inspection of vegetative control measures).
2. Overall Finding: Need for Rationalized Performance Standards
Water quality and flood control benefits may be achieved jointly via a combination of
site design, and structural and non-structural measures. Municipalities could benefit from
requiring that stormwater management plans be submitted for all applicable development
proposals, with accompanying maintenance plans where structural controls are to be put in
place. The intent of all stormwater management plans, and the basis for their evaluation,
should be to
1) reduce the volume of runoff generated by minimizing the extent of imperviousness,
enhancing overland flow, and maximizing pre-concentradon surface infiltration;
2) treat or mitigate pollutant concentrations in runoff transported off-site.
Where structural measures are required to meet flood hazard mitigation requirements,
strict preference should be given to those which provide water quality enhancement or can
efficiently be up-graded during the design process to treat runoff effectively. Because of
their efficiency in removing sediment load and other pollutants, use of wet basins designed
to attain specified removal rates is recommended. Similarly, measures providing biological
uptake should be applied in any feasible situations. In accordance with the
recommendations of the SWCD, and where consistent with groundwater protection
objectives, infiltration devices should be used to complement the previously mentioned
strategies.
As recommended by the Beaver Swamp Brook Management Plan (Sattenhwaite,
1987),
water quality management objectives, performance standards, and component design
standards should be incorporated in detail into town ordinances to the maximum extent
possible. Provisions which might be incorporated into local regulations, or adopted as
planning board standards include:
1. Control stormwater volume on site to the maximum extent practicable to prevent
degradation of surface waters, depletion of groundwaters, and exacerbation of flooding
problems;
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2. Use detention/retention basins to collect runoff from catch basins and drains; where
possible transport piped stormwater to detention basins rather than to surface waters;
3. Where soils and groundwater protection standards permit, use perforated pipes to
recharge underlying aquifers. Use grassed swales and rip-rapped channels as alternatives
to subsurface stormwater drainage networks;
4. Use dry wells and infiltration devices with added storage where appropriate to collect
roof drainage and drainage from parking areas;
5. Collect parking lot runoff in catch basins (equipped with oil and grease traps) which
subsequently drain into detention/retention basins. Schedule regular maintenance of traps
and detention areas;
6. Place limitations on the impervious surface area of roads, driveways, and sidewalks,
consistent with minimum federal requirements, to reduce surface area contributing to
runoff. Discourage use of curbs and berms except as necessary to protect the integrity of
heavily-travelled roads. Encourage use of porous or permeable driveways, permeable road
shoulders on less heavily used roads, and permeable surface walkways;
7. Limit site impervious area to 10 percent. Encourage use of permeable or porous
pavement to meet impervious area limits. For site re-development, create tax or other
incentives for reduction of existing impermeable surface.
8. Encourage development of detention/retention facilities serving larger areas by requiring
that post-development peak runoff equal pre-development quantities as well as pre-
developmem rates; and
9. Require maintenance of naturally vegetated buffer strips adjacent to surface waters in
critical areas. If vegetative filter strips must be used as an alternative to natural cover,
require use of recommended seed mixtures necessitating little or no fertilization.
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B. SPECIFIC FINDINGS AND CONCERNS RELATED TO INDIVIDUAL BMPS
Introduction
Water quality enhancement measures include, for example, wet basins, extended
detention dry basins, infiltration devices (such as basins, trenches, and dry wells) and
vegetative control measures. Water quality control techniques basically fall into four
general categories, elements of which are sometimes combined in multiple purpose BMPs.
The benefits to be gained in combining different BMPs (such as infiltration devices and wet
detention basins; vegetative measures and wet or extended detention dry basins; etc. has
been widely documented and should not be underestimated in development of a
comprehensive watershed control strategy.
A. Detention Devices: These include normally dry detention basins typically designed for
runoff quantity control, normally wet detention basins, dual purpose basins, over-sized
drain pipes, and catch-basins.
B. Recharge/Infiltration Devices: This category includes infiltration pits, trenches, and
ponds; open bottom galleries and catch-basins; and porous pavements.
C. Vegetative Control Measures or Living Filters: These include grassed swales, artificial
wetlands, biofiltration systems.
D. Housekeeping Practices: These include street sweeping, leaf removal, de-icing, litter
management, catch-basin cleaning, maintenance functions, pet clean-up ordinances, etc.,
and are discussed in Pan ED.
As indicated in other sections, the limited scope of the current effort, and the number of
jurisdictions involved, did not accommodate an in-depth evaluation of facility effectiveness.
To accompany development of a counrywide stormwater management strategy considering
inter-related flood hazard management and water quality protection needs, an in-depth site-
by-site inventory of local stormwater control facilities and an analysis of the effectiveness
of specific types on public and private property should be undertaken to acquire date on
operation and maintenance issues and enforcement problems in particular.
1. Detention Devices
Dry Detention Basins
A dry detention basin is an open pond designed to retain flood flows for a certain period
so that downstream flooding can be avoided In dry detention basins, outflow rates are set
at the pre-development peak discharge rate, and the flow is 'metered' out of the basin to a
storm sewer or water course.
Although dry basins have proven effective in mitigating increases in downstream
flooding due to changes in upstream land use, they are designed to control runoff peak
discharge rates, rather than volumes, and cannot adequately address considerations of
timing of discharge into a water course, or other volume-related aspects of regional
stormwater management
In addition, dry basins are typically quite ineffective in terms of providing water quality
enhancement of runoff (U.S. EPA, 1983). As opposed to traditional flood control
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measures, water quality control measures are designed to control runoff volumes, rather
than peak discharge rates, and to remove runoff-borne pollutants via such measures as
physical settling, infiltration into the soil substrate, biological uptake, or chemical
transformation.
Turf and other vegetation lining grass pond bottoms should be mowed twice a year to
prevent the growth of woody plants, and up to 14 times per year for aesthetic landscaping
purposes. Low flow outlet channels should be cleared to prevent persistence of marshy
pools during the growing season, which may provide mosquito breeding areas as well as
interfering with even turf growth and mowing operations. Simple outlet structures should
be maintained to prevent clogging with sediment and debris. Sediment and trash must also
be removed. Sediment is generally removed mechanically.
Several dry detention basins are in place in the Mamaroneck Sheldrake watershed and,
to a lesser extent in the creek watersheds tributary to Mamaroneck Harbor. Maintenance
problems, particularly litter removal, were cited as major continuing concerns by officials
in White Plains. In Rye Brook, Harrison, and the Town of Mamaroneck, maintenance has
not proven to be a notable problem.
As an element of cost effectiveness, however, maintenance issues should be carefully
considered. In a 1987 presentation, the District Manager of the SWCD pointed to "a
proliferation of numerous, variously sized detention facilities throughout the area, most of
which have little or no long-term maintenance provisions." Because these facilities offer
very few water quality benefits, they are not recommended as elements of a stormwater
quality rehabilitation strategy for Mamaroneck Harbor.
Wet Detention Basins
Wet detention basins are ponds in which water levels are maintained, rather than
metered out Because wet basins are designed to maintain a permanent pool of water,
'reaction time' is enhanced and the scouring action of incoming flows (with associated
resuspension of sediments) is reduced. Wet detention basins employing permanent pools
have found to be capable of achieving substantial reductions in indicator bacteria, heavy
metals, PAH, particulates, and other contaminants (U.S. EPA, 1983; Harrington, 1986;
New Jersey DEP, 1986; Northern Virginia Planning District Commission, 1987)
Wet basin performance in terms of pollutant removal is correlated to the size of the basin
relative to the connected urban area and local storm characteristics. Efficiency is optimized
when size relationships result in the mean storm displacing only approximately 10 percent
of the available volume, and producing overflow rates which are a small fraction of the rate
of overall particle settling velocity (U.S. EPA, 1983).
Time of detention is extremely important. Harrington's (1986) analysis of the NURP
data indicated that after an average of 24 hours more than two thirds of the sediments, total
nitrogen, total phosphate and trace metals contained in urban runoff were removed. The
Metropolitan Washington Council of Governments 0983) found a positive correlation
between pollutant concentration and rate of removal, which supports the 6 to 12 hour
period required to remove 65 percent of sediment from commercial areas sampled
Whipple and Hunter (1981) found that between 16 and 32 hours detention were required to
remove a range of constituents. Seventy percent of suspended solids concentrations were
removed after 32 hours, along with 65 percent of lead and hydrocarbons, respectively.
BOD and phosphate reductions of up to 50 and 60 percent, respectively, were found in the
same time period.
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Side slopes should be designed at 3:1 to 4:1 or more to facilitate mowing. Cattails,
phragmites, or other vegetation planted along shorelines aids in nutrient and contaminant
assimilation, and provides habitat for wildlife, which can help to control mosquitps.
Sediment removal costs can be reduced if sediment forebays are constructed at primary
inlets and outlets where much of settling occurs, and by constructing additional storage in a
portion of the permanent pool area. In larger wet ponds, use of hydraulic dredges or
draglines may be required every 10 to 20 years to remove sediment.
There are a number of wet basins in use in the study communities, some of which, such
as the General Foods headquarters pond in Rye Brook, serve as major aesthetic design
features of the properties. In White Plains, Scarsdale, Harrison, and Rye Brook, officials
were of the opinion that wet basins enhanced real estate values of associated properties. As
outlined previously, the basins have not presented major maintenance concerns.
Installation of wet detention basins need not involve large scale excavation. In fact,
shallower vegetated ponds capable of treating the "first flush" have proven extremely
effective in water quality enhancement (Driscoll, 1982). In addition, wet basin design
procedures have been developed which can be used to design dual purpose basins for flood
control and water quality enhancement (U.S. EPA, 1986). Given the water quality
enhancement potential of these facilities, potential for dry basin upgrades, and existing
experience with the facilities, expanded use of wet detention basins should be strongly
considered as an aspect of Mamaroneck Harbor restoration.
Extended Detention Dry Basins
Extended detention dry basins are dual purpose BMPs which meter out flow at a
significantly slower rate than dry basins, allowing for enhanced physical settling of
sediments and greater biological uptake of pollutants. However, extended detention dry
basins are subject to scouring, and thus to resuspension and discharge of previously settled
sediments. Basins designed for 24 hour minimum detention time have been found to
effectively remove more than 2/3 of sediments, total nitrogen, total phosphate, and trace
metals contained in runoff (Harrington, 1986).
Maintenance requirements of extended detention dry ponds are similar to those of dry
ponds, although longer detention times may create sustained marshy conditions which
impede mowing and debris removal. To prevent clogging of small orifice outlets,
perforated riser outlets with stone filter jackets should be used. Sediment may be removed
mechanically.
Only one basin having the characteristics of an extended detention dry basin was
identified in the study area. The basin is located in Port Chester, and may not have been
intended to sustain wet conditions as it does in practice. Extended detention dry basins can
provide significant pollution control benefits, can be applied to combined water quality and
flood control needs, and can be economically created by retrofitting existing dry ponds.
For these reasons, they should be investigated as a potentially important element of
Mamaroneck Harbor water quality improvements.
2. Recharge/Infiltration Devices
Partly due to hydrological constraints (slow soil percolation rates, shallow depth to
bedrock, seasonal high water table) use of larger scale infiltration BMPs have been
approached quite cautiously in Westchester County. The SWCD Stormwater Management
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35
Manual suggests that infiltration BMPs be used only for small areas in well-percolating
soils (preferably outwash soils).
Because of the potential for sediment buildup, experience on Long Island and in other
areas suggests that infiltration devices should only be used on fairly gradual slopes to treat
runoff from stabilized areas where the sediment loading rate will be extremely low.
However, these facilities can be combined with additional prc-treatment devices to prevent
clogging by solids, oil and grease, etc. Vegetative filter strips and oil/water separators can
help serve these purposes. Added storage facilities can be combined with infiltration
devices to allow for metered infiltration that accommodates larger flow.
Infiltration Trenches, Pits, and Basins
Infiltration pits, basins, and trenches are stabilized, excavated facilities, generally filled
with a porous aggregate and equipped with perforated distribution channels or pipes, which
are designed to hold flood flow for seepage into the soil substrate. Infiltration measures
rely primarily on biological uptake of pollutants as the principal means of runoff treatment.
Because runoff seeps into the surrounding profile, infiltration measures provide for viable
volume reduction. A ponding time between 48 and 72 hours is recommended as a storage
time allowing adequate treatment (Versar, Inc., 1986).
As previously stated, infiltration trenches and pits may be subject to clogging by
sediment, oil, grease, grit, and/or other debris. Performance, and build-up of sediment in
the top foot of stone aggregate near the surface inlet, should be closely monitored after
every large storm or on a quarterly basis. Use of a monitoring observation well for this
purpose has proven successful in the Washington metropolitan area. Depending upon
performance and siltation rates, monitoring frequency may be reduced after the first year.
Sediment should be preventing from accumulating to a point which inhibits infiltration rates
into trenches. Planted vegetation has been found to help sustain infiltration rates.
Side slopes of infiltration basins should be mowed at the beginning and end of
summer. Once turf is well established on an infiltration basin floor, as with infiltration
trenches, roots should penetrate sediment deposits and impede the formation of an
impermeable sediment layer. On non-vegetated basin floors, sediment should be removed
and tilled annually, preferably during the summer.
No use of infiltration trenches or basins was documented in the study communities,
although large underground infiltration chambers and/or buried sand leaching beds are in
use in Rye Brook, White Plains, and Harrison. Given the successful use of these
practices, and the use of arrays of dry wells in the area, expanded use of infiltraton devices
should be strongly considered as a means toward water quality protection and mitigation of
runoff volume.
The devices might be appropriately used in areas at a distance from water supply wells,
or where deep wells draw from supplies which would be unaffected by drawdown. When
appropriately sited, adequately sized and properly designed, infiltration devices can provide
very effective control of urban runoff-borne pollutant discharges. Evidence from NTJRP
studies did not indicate that significant groundwater contamination would result from these
practices (U.S. EPA. 1983).
Dry Wells
Dry wells are a common infiltration device. The structures are generally precast
concrete chambers with slotted or perforated sides, and are used to collect roof, driveway
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and other surface drainage. Because runoff infiltrates directly into the soil, runoff volume
can be completely retained, or can effectively be held to pre-development levels.
Dry wells must be sited in permeable soils, and effectively spaced one from another, as
well as from walls, roads, structures, and septic facilities.
In the study communities dry wells are in nearly ubiquitous use on residential lots, and
in two to three lot subdivisions. Dry wells are also used to drain some non-commercial
parking lots. Underground detention galleries are preferred in Harrison, due to less
frequent clogging, but arrays of dry well are also occasionally used to infiltrate roof
drainage from commercial properties. These devices in general appear to be functioning
effectively in water quality enhancement and runoff reduction.
Pre-formed Porous Pavements and Permeable Pavements
Used in driveways, walkways, low-use parking areas, or turn-arounds, porous
pavements are pre-formed reinforced concrete grids or open-graded asphalt concrete mixes
.which can enhance infiltration, while providing aesthetic benefits. The upper surface
allows rainfall to seep into a prepared porous crushed rock subbase for infiltration or
detention. Permeable paving, such as brick and gravel, can be used for walkways, patios.
and driveways for the same purposes. Permeability must be sufficient to allow rapid
drainage. These techniques are suited to small sites where installation of detention facilities
is difficult, but are unsuitable for areas where a seasonally high water table is anticipated
(SWCD Soil Groups C and D).
Pollutant loadings can be dramatically reduced by porous pavements. The Washington,
D.C. NURP findings showed pollutant reductions of 85 to 90 percent, depending upon the
pollutants considered (U.S. EPA, 1983).
Porous pavement surfaces should be cleaned quarterly to avoid clogging of pavement
pores by fine sediments, oil, and grease, which may bind sediments. A vacuum street
sweeper should be used quarterly, followed in all cases by high pressure water washing.
Porous pavements should not be used in areas where sand must be applied for winter
traction.
In pan because of winter maintenance concerns, porous pavement is little used in the
Mamaroneck tributary watersheds. Only one municipal site in the Village of Mamaroneck
was identified, as were two sites in Harrison. Applied to two sites in Rye, the pavement
was incompletely maintained, and use has not been encouraged since. The SWCD limits'
porous pavement area to one acre.
In Scarsdale and Harrison, gravel driveways are considered permeable for runoff
calculation purposes. White Plains and Harrison do not encourage use of gravel driveways
because of compaction and maintenance concerns. Pon Chester requires that driveways be
paved and drain into detention facilities.
Overall, winter conditions appear to limit the applicability of these practices other than
for residential or less travelled areas.
3. Vegetative Measures
Vegetative measures include grasses swales, filter strips, grassed ditches, and vegetated
buffer strips. These measures can enhance infiltration, as well as mitigating waterbody
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sedimentation and providing biological uptake. In NURP investigations, grassed swales
achieved up to 50 percent reduction in heavy metals, and 25 percent reduction of COD,
nitrate, and ammonia (U.S. EPA, 1983). Use of organic liners and incorporation of
organic material into the soil profile can enhance pollutant removal efficiency. The
Metropolitan Washington Council of Governments recommends use of forested filter strips
where ever possible, because of their significant pollutant removal efficiency (Metropolitan
Washington Council of Governments, 1987).
Swales and filter strips art effectively applied as complements to other structural
stormwater control devices where they can reduce sediment load, increase time of
concentration, and lower pollutant loadings. They may also be used to treat sheet flow
from residential areas, low intensity roadways, and in areas adjacent to waterbodies.
Pollutant removal effectiveness in these applications depends upon several factors,
including rate of runoff flow through the vegetated area and soil infiltration rate.
Vegetative measures cited as specific BMPs are not in wide use in the Mamaroneck
Harbor watersheds in spite of the fact that the SWCD BMP manual on stormwater
expressly recommends two vegetative measures. Diversion of roof water to grassed
surfaces is recommended in residential areas to reduce both volume and peak rate of runoff
and to improve water quality. Grassed ditches are recommended as being applicable to
residential, institutional, commercial, industrial and highway use, for the same purposes.
Although vegetated buffer strips are sometimes required adjacent to critical areas, and
roadside swales are in place-in older neighborhoods, use of grassed areas for roof leader
drainage is expressly prohibited in most communities, except on very large lots, and does
not seem to be encouraged in any of the study communities. Similarly, filter strips seem to
be little used except in road construction activities.
As outlined in Pan JJ, most communities require revegetaoon via the site plan review
process. Buffer requirements are sometimes imposed adjacent to critical environmental
areas, but may not require the use of native vegetation.
Use of the entire range of vegetative measures should be increased in the watershed
wherever appropriate. Grassed swales and ditches, in particular, could be effective in
reducing pollutant concentration and runoff volume.
4. Overall Finding: Potential to Enhance Mamaroneck Harbor Water
Quality via New Structures and Up-Grades
An extensive body of literature has developed on the effectiveness, efficiency and cost-
effectiveness of various volume control measures. Although an analysis of the literature is
beyond the scope of the present research effort, a review of related materials suggests that
several consistent findings may be applicable to the stormwater-relaied pollution problems
in Mamaroneck Harbor
Wet detention basins have a very high potential to provide significant pollutant removal
benefits.
NURP studies showed that wet basins reduced soluble phosphorus in urban runoff by
65 percent, and other soluble nutrients and pollutants (total nitrogen, BOD, COD, copper
and zinc) by 50 percent. Both sedimentation and biological processes operating in wet
ponds contribute to effective removal. When adequately sized, wet detention basins were
found to remove more than 90 percent of total suspended solids and lead, and were also
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capable of removing 50 to 94 percent of petroleum hydrocarbons, and 24 to 93 percent of
paniculate PAH (U.S. EPA, 1983).
Given the current role of conform bacteria in regulation of beach use in Mamaroneck
Harbor, the ability of wet detention basins to reduce coliform bacteria concentrations could
be of considerable significance. At the Unqua basin site of the Long Island NURP project
mean reductions in coliform concentrations over a wide range of storm sizes were reduced
94 percent for total coliform, 91 percent for fecal coliform, and 95 percent for fecal
streptococci. Overall, the NURP analysis concluded that detention basins employing
permanent pools were capable of achieving substantial reductions in indicator bacteria.
Extended detention dry ponds designed for 24 hour detention can also be extremely
effective in reducing nutrient and pollutant loadings.
Results of urban runoff monitoring studies document the occurrence of maximum
pollutant concentrations during the 'first flush' of storm events (Hoffman et al, 1985; 1983,
1982). Because Hoffman and others have documented that the discharge of runoff-borne
pollutants is supply limited as opposed to transport limited, the majority of pollutants can
be 'captured' if the facility is designed to provide storage or treatment of the first flush.
The design storm for water quality purposes, then, may be considered to be the one year
frequency 24 hour duration storm, which represents the commonly occurring, short
duration rainfall event, and in a majority of cases, the "first flush" of longer duration, less
frequently occurring events. Maryland, New Jersey, Rhode Island and the Federal
Highway Administration have selected this storm event as the design storm for water
quality purposes.
Because the design storm volume for water quality is relatively small as compared to
flood control storage volumes, it has been proven effective to upgrade existing small
detention facilities to dual purpose facilities (providing treatment of the first flush) while
developing larger dual purpose regional facilities for watershed level control. Recent
research by the Metropolitan Washington Council of Governments 0986) has indicated that
modifying a dry pond for extension represents the least cost water quality BMP option at
most sites.
Existing flood control basins can be upgraded to increase pollutant removal capability.
While the pollutant removal performance capabilities of dual purpose detention devices
(extended detention dry ponds) are not equal to those of wet detention ponds, many
existing stormwater detention facilities may be readily modified to significantly increase
their potential for treating stormwater. In watershed municipalities where ordinances
requiring retention to pre-existing discharge rates are already in place, the only regulatory
adjustment required would be an alternate specification of the outlet design.
In addition, flood control requirements may be met more economically than with wet
basins, where optimum displacement proportions are fairly low. Ideally, a combination of
controls should be put in place, in which smaller wet ponds and extended detention dry
ponds served as complements to the use of regional dual purpose detention facilities.
Appreciable economies of scale can be realized in meeting construction and maintenance
costs of basins as larger drainage areas are served.
For on-site controls serving a catchment area of 20 to 40 acres. NURP data indicate that
annual costs to achieve 50 to 90 percent TSS reductions ranged between $60 and $175 per
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acre. Similar off-site controls serving 640 to 1000 acres showed annual costs of $10 to
$25 per acre (U.S. EPA, 1983).
Incremental costs of building a multi-purpose water quality BMP, in lieu of a
conventional dry pond, vary with land use and watershed size. In general, costs have been
lowered by roughly a factor of 10 when comparable regional facilities are developed. The
reduced cost-effectiveness of BMPs for smaller development sites implies that stormwater
control strategies should focus on drainage areas of 25 acres or greater (Weigand, et al,
1986).
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Ill HOUSEKEEPING ORDINANCES AND PRACTICES
The activities and practices classified as housekeeping practices varies broadly
depending upon the source documents consulted. The Westchester County Soil and Water
Conservation District uses a general classification of "Non-structural Controls" for the
following practices:
1) Water Quality Management Planning
2) Liner Management
3) Street Cleaning Practices
4) Catch Basin Maintenance
5) Erosion Control Practices
6) Fertilizer, Pesticide, and Herbicide Controls
7) Roadway De-icing Salt and Chemical Controls
8) Industrial/Commercial Site Drainage Controls
In the present study, water quality management planning and erosion control are
considered in Pan n, as authority is provided primarily via specific elements of zoning,
subdivision, floodplain management or resource protection ordinances.
Practices relating to routine public maintenance and/or use of specific materials are
classified as housekeeping practices, along the lines of the NURP classifications.
Mamaroneck study area practices are listed in Appendix n.
1. Catch Basin Cleaning
Stormwater catch basins can accumulate significant levels of silt, coarser grained
sediment and organic material in the sumps designed to prevent entry of debris into the
storm sewers. Levels of BOD generated by decaying organic material, can be quite high,
depending upon seasonal factors and the length of time separating storm events. Most of
the catch basins in the Mamaroneck harbor watershed communities were designed with
sumps, which must periodically be cleaned to reduce the "first flush" shock loadings of
BOD and sediment-adsorbed pollutants which accompany storm runoff events. For storm
sewer sections without catch basin sumps, and for removal of heavy sediment loads,
vacuum and jet cleaning machinery must be used in a sequenced pattern from upper to
lower watershed areas of the network.
As with other housekeeping practices, the communities in the Mamaroneck-Sheldrake
and other tributary watersheds of the Harbor take a range of approaches to catch basin
cleaning. Most do not have specific budgetary allocations for the purpose, but use general
public works department or highway department funds for periodic maintenance. A few
contract out the work. The Village of Mamaroneck, for example expended $70,000 in 1987
to get roughly fifty percent of the Village catch basins cleaned. Absent a special allocation
of funds for the purpose, basins in the Village are cleaned in response to complaints.
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2. Maintenance of Oil/Water Separators
Gravity oil/water separators are increasingly required by municipalities to control site
drainage from specific types of facilities. In the relatively near future, parking lots (above
and below ground), service stations, public works and transportation maintenance
facilities, industrial yards, and other sites accumulating high levels of priority pollutants
characteristic of industrial contaminant categories may relatively soon require SPDES
permits for discharge to storm sewers. Because these sites must then meet assigned
effluent limits based upon DEC and EPA water quality standards, oil/water separators are
now being used to anticipate those limits.
None of the study communities has a program or regulatory authority in place to require
maintenance of oil/water separators. Officials interviewed indicated that maintenance was
the owner's responsibility. Maintenance has not arisen as an issue in any of the watershed
communities.
Although very little data exists on the performance of oil/water separators, owner
experience with these devices should be carefully monitored by the study communities.
Many jurisdictions in New England have reconsidered requiring installation because of
evidence that materials clog the devices and are subsequently released in a "pulse" of highly
concentrated contaminants during heavy storms.
3. Lawn-Care-Related Restrictions
Pesticide and fertilizer application on home lawns has increased steadily since the
beginning of the 1970's, and chemicals are frequently applied adjacent to impervious zones
having high potential for surface runoff. The Long Island NURP study monitoring results
indicate that medium density residential development has the highest loading factor of any
land use studied (Long Island Regional Planning Board, 1982). Other researchers have
identified turfgrass, in particular, as a source of substantial levels of contaminant leachate.
A1980 survey conducted by Cornell University showed that 39 percent of the residential
land on Long Island was in turfgrass (130,000 acres) and that an additional 26,000 acres of
turf was associated with commercial development The study found a direct correlation
between fertilizer use and affluence, with wealthier communities heavily utilizing lawn care
services (Cornell Water Resources Inst., 1985, in Myers, 1988).
The Long Island study assembled a range of statistical data on application. In the most
affluent communities, 98 percent of residents used fertilizers on their lawns and gardens,
72 percent used lawn care services, and the average fertilizer application rate was 3.3
pounds per 1000 square feet of turf. In the least affluent neighborhoods, 45 percent of
residents used fertilizer and none subscribed to lawn care services. In those areas, the
average fertilizer application rate was 1.1 pounds per 1000 square feet Overall, the average
for Long Island turfed areas was 2.3 pounds per 1000 square feet, or between 6500 and
8500 tons of fertilizer applied annually. On mature lawns, any amount over 1 pound per
1000 square feet is excessive, and is likely to reach receiving waters via runoff or leaching
into groundwater (Cornell Water Resources Inst., 1985 in Myers, 1988).
Attribution of residential loadings to waterbodies depends upon the extent of sewering
and the condition of individual septic disposal systems. In sewered areas, where the
primary source of nitrates is turf and garden care practice, the 1980 Long Island study
showed that nitrate levels were correlated with housing density, such that levels ranged
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between 3.0 to 4.3 ppm at one house per acre, and up to 11 to 15.5 ppm. at densities of five
to ten houses per acre. The authors concluded that, although affluent neighborhoods
fertilize more readily, smaller house lots have higher proportions of land in turf (Cornell
Water Resources Inst., 1985 jn. Myers, 1988).
The Planning Board of the Town of Falmouth cited other studies of the use of fertilizer
on lawns which showed a range of averages from 1.52 Ibs. N per 1000 square ft. (standard
deviation 1.4) to 3.75 Ibs N per 1000 square ft. Socioecpnomic and environmental factors
identified as playing a large pan in the size and fertilization of lawns included average
income of residents; age of the development; zoning status; maturity of lawns; size and age
of trees in the area; topography of land area (Memorandum to the Falmouth, Massachusetts
Planning Board from K. Buckland, Town Planner, Nov. 25,1986, in Myers, 1988).
Golf courses, cemeteries, and other heavily landscaped areas have also been sources of
concern with regard to contaminant loading. On Long Island, in the same study,
researchers found that more fertilizer (4.3 pounds/1000 square feet) is used on golf course
greens than on fairways (3.1 pounds/1000 square feet). However, fairways constitute 74
percent of the course area, and clippings are left to serve as mulch, so nitrate levels are
actually higher beneath fairways (15 ppm, compared to 9.3 ppm beneath greens) (Cornell
Water Resources InsL, 1985). Technical personnel interviewed during the course of the
present study considered underground irrigation mechanisms to be a significant potential
concern on golf courses, as these devices could accelerate transport of nitrate-laden soil
percolate.
In the Mamaroneck Harbor watersheds, leaching of nutrients is of considerable concern
given recent evidence that nutrient enrichment may contribute to coliform replication
(Sanenhwaite, Inc., 1987 and Heufelder et al, 1989). Relationships suggested by Cowen
and Lee 0976), and Cowen et al 0976) indicate that the biologically available fraction of
plant nutrients in urban runoff loadings may be approximately 59% to 69% of total
phosphorus and 70% of total nitrogen loadings.
In addition, nitrogen limited coastal estuaries, bays, and coves may be degraded by
concentrations of nitrate-N far below the U.S. drinking water standard of 10 me per liter
(Gold, 1987, io_Myers, 1988).
Research conducted by Gold and Sullivan at the University of Rhode Island was
designed to evaluate the waterbome losses of nitrogen and the herbicides 2,4-D and
Dicamba from home lawns. The two pesticides were selected because they are among the
most common agrichemicals used on home lawns, have been found to leach in sandy soils,
have been detected in Great Lakes basin surface waters, and could affect marine vegetation.
Simulating typical application rates and formulations use by commercial lawn care
operations, and using two irrigation schedules that simulated adequate and overwatered
treatments, the investigators measured input to receiving waters. Results showed that
substantial increases in nitrogen loadings to groundwater resulted from overwatering of
fertilized lawns. Overwatering caused a 16 fold increase in the annual loss of inorganic-N
in soil water percolate, demonstrating the key importance of water management in off-site
losses of N. Pesticides did not appreciably migrate to groundwater in the study (Gold and
Sullivan. 1987, in Myers, 1988).
None of the study communities have nutrient control ordinances in place, although the
Village of Mamaroneck has considered putting such a mechanism into effect In
cooperation with the County, DEC, and SUNY, communities should consider working to
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identify sensitive areas where further nutrient and/or pesticide loading to waterbodies and
groundwater should be controlled.
To complement DEC guidelines on pesticide application, communities could consider
adopting pesticide control regulations to require a consumer notification provisions. The
regulations could stipulate that commercial lawn care operations place clear warning signs
on all properties where pesticides were applied. Landowners would be required to leave
the notification signs in place for three days following each application. (This practice is
required by the Massachusetts Pesticide Control Act, MGL Chapter 132b.)
With regard to nutrient loading, communities could consider adopting provisions for
determination of nutrient loading as an element of project review, particularly in sub-
watersheds affecting critical environmental areas. Falmouth, Massachusetts has applied a
subdivision ordinance and analytical methodology which include use of a nutrient loading
model that account for inputs from human waste, lawn care, and road runoff.
Watershed communities could also consider developing an aggressive public education
campaign to inform home-owners regarding proper use, handling, and storage of fertilizers
and pesticides. Detailed information on rate and timing of application and irrigation should
be included. Results of a Northern Virginia Planning District Commission study estimated
that a public education campaign that achieved a SO percent reduction in fertilizer losses
from residential lawns could translate into total phosphorus removal rates on the order of
5% to 25% for single family land uses, depending upon soil permeability.
In subwatersheds affecting critical areas, municipalities could consider establishing
community standards limiting the use of fertilizers on home lawns, and severely restricting
use of commercial lawn treatments unless operators conform to established standards.
Covenant restrictions containing such standards could be placed on subdivision properties.
compounds or other properties potentially contributing significant loadings. Similarly,
communities could consider establishing policy standards for use of alternative ground
cover, focusing on indigenous or introduced species with low level water and nutrient
requirements.
4. Road De-Icing
Until recently, the use of road salt to accelerate melting of ice and snow has steadily
accelerated. Both the use and storage of road salt can have several deleterious effects,
including:
degrading the quality of receiving waters;
adversely affecting roadside vegetation;
reducing soil permeability;
contributing to corrosion of automobile pans;
damaging highways; and
corroding and damaging underground utilities such as water mains,
electric lines, and telephone cables.
In drainage areas of enclosed coastal embayments such as Mamaroneck Harbor, delicate
salinity regimes may be altered by the impacts of salt-laden runoff, particularly when
periods of warm temperatures induce melting of accumulated salt build-up. Pulses
associated with heavy rainfall may also be deleterious (Myers, 1988).
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A1981 Rhode Island study estimated that 3 to 4 percent of stockpiled road salts are lost
annually to the environment through runoff or leaching. Although salt storage has been
responsible for some chloride loadings in the Mamaroneck Harbor watersheds, surface
water loadings primarily result from application to roads. Due to the slow flushing rate of
groundwater, it is more susceptible to sodium and chloride contamination than surface
waters of the state, which have not yet been substantially affected by salting activities. Salt
has impacted groundwaters in the state, however, particularly on Long Island. In response
to these concerns, communities such as Scarsdale have begun using salt substitutes as a
proportion of their de-icing mixture.
Use of lower salt to sand ratio mixes in deicing has affected sediment loading in ways
which have not been completely accounted for in sediment management. The New York
State Department of Transportation publishes snow and ice treatment guidelines for various
road classes under specific conditions. Sand application rates are established by the
County and truck distribution equipment must be calibrated annually. However, decision-
making as to actual operating practice rests primarily with individual municipalities.
Salt storage and application practices are fairly dissimilar across study communities and
within communities, depending upon predominant road classification, slope, and other
factors. Most communities store salt in covered sheds located on asphalt pavement, though
White Plains leaves storage areas uncovered in winter. No brine recycling mechanisms are
in place. Standard salt to sand ratios cited by officials range between 1:5 using a portion of
liquid salt substitute and 1:3 using salt and sand only.
In environmentally sensitive areas such as the brackish wetland and marsh areas
bordering Mamaroneck Harbor, and in areas subject to groundwater contamination,
communities should consider incorporating the de-icing recommendations of the Long
Island Regional Planning Board into local highway department procedures. The
recommendations address all aspects of road salt application and plowing, providing
specific guidance as to runoff and leaching mitigation methods (Long Island Regional
Planning Board, 1984). The Draft New York State Nonpoim Source Management Strategy
specifically references these guidelines. All salt should be stored in permanent closed
structures located on impermeable surfaces, to minimize loss due to leaching and runoff.
5. Street Sweeping and Leaf Removal
Street sweeping can be justified on the basis of general municipal sanitation and
aesthetic improvement. However, results of numerous carefully controlled NURP studies
of the effectiveness of street sweeping in control of urban runoff quality indicated that,
overall, no significant reductions in event mean concentrations of pollutants could be
demonstrated. Further, benefits observed were masked by the large variability of the event
mean concentrations and never exceeded 50 percent reduction in any constituents
(U.S.EPA, 1983). These results were corroborated in the Long Island NURP for
coliforms.
The Long Island study stratified data indicated 48 percent reduction in fecal coliforms, a
marginal 15 percent reduction in total coliforms, and essentially no reduction in fecal
streptococci. Seasonal differences found with all of the coliforms pointed to a possibly
significant removal of fecal coliforms by street cleaning during the summer.
Nevertheless, the authors considered the value of street cleaning to be "rather suspect"
as a control measure, in view of the fact that broom-type sweepers, in particular, may
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reduce particle size for material not picked up, making the fine material more susceptible to
washoff (Driscoll, 1983, in U.S. EPA, 1983).
Leaf removal, however, can be important in preventing clogging of catch basins and
sewers, reducing levels of chlorinated organics in reservoirs, and controlling loadings of
biologically available plant nutrients to receiving waters.
All of the Mamaroneck Harbor study communities maintain street sweeping and
seasonal leaf removal programs. Except for leaf removal, most use broom-type sweepers
exclusively, although a very few of the vacuum sweepers, which are marginally more
expensive, are also in use. Among the officials interviewed, all considered vacuum
sweepers to be ineffective in removing heavy sediment, and thus inapplicable to springtime
or autumn sweeping where sand and leaf removal is required. Vacuum sweeper operation
and maintenance cost, however, is lower than that of broom sweepers (SWCD, 1984). A
few of the study communities own large vacuum trucks usable for cleaning debris from
catch basins and picking up wind-rows of autumn leaves.
Schedules of sweeping vary considerably, ranging from daily sweeping of business
districts to seasonal sweeping of geographic sectors for leaf and sand removal. Parking
restrictions allowing thorough coverage are imposed in some municipalities, but not in
others.
Given the high cost of street cleaning relative to its dubious benefits, expanded overall
investment in the effort may-not be justified in terms of potential harbor water quality
improvement. Municipalities should, however, evaluate the potential benefits of using
vacuum-type sweepers more frequently in summer, as a substitute for, or in close sequence
with the use of broom sweepers. Potential reductions in fecal coliform loadings to the
harbor during the bathing season may justify such a strategy. This effort should be
coupled with stepped-up enforcement of dog clean-up ordinances during the same season.
6. Litter Control
In contrast to its set of conclusions regarding the effectiveness of street sweeping in
stormwatcr quality management, NURP results with regard to litter management were
positive. NURP classified litter management within its category of "miscellaneous BMPs"
which were applicable on a site-specific basis. These BMPs were frequently found to
show marked effectiveness on a small spatial scale, although broad scale effect on overall
urban runoff loads was impossible to document (U.S. EPA, 1983).
Urban housekeeping, or liner control, was found to produce substantial differences in
urban runoff quality in the Baltimore and Long Island NURP projects, among others
(U.S.EPA, 1983; Metropolitan Washington Council of Governments, 1983,1987).
All of the communities in the present study maintain litter control programs, although
schedules, area coverage, and other factors vary widely. In all municipalities liner is
collected from central business districts. Schedules range from "on an as-needed basis" to
daily pick-ups. The effectiveness of the individual programs in mitigating runoff quality
cannot be determined, given the lack of local sampling data. However, certain institutional
efforts should be encouraged as a maner of practice, such as the Village of Mamaroneck's
program encouraging proprietors in the central business district to keep sidewalks clean and
clear of refuse.
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7. Dog Clean-up Laws
Stormwater runoff from town secondary roads and neighborhoods has been shown to
be a very significant source of coliform loading, particularly in areas having large domestic
dog populations (Heufelder, 1989; Long Island Regional Planning Board, 1982). In the
New York NURP studies urban runoff containing dog and other animal wastes was found
responsible for shellfish bed closures.
Comparing estimated coliform contributions of dogs and domesticated wildfowl to
contributions of an acre of residential land, the Long Island NURP concluded that animal
waste could "in fact be contributing all or almost all of the fecal coliform load attributed to
runoff from the landscape." Dog waste was estimated to contribute a fourfold higher
coliform concentration than the residential parcel, while domesticated wild ducks and geese
contributed 11 and 49 times the residential loading respectively. Further, runoff samples
from in situ sites contained proportional concentrations of fecal coliform and fecal
streptococci characteristic of animal sources.
Pointing to the relatively larger importance of these sources in small watersheds with
significant animal populations, the study stressed that "with regard to coliform reduction
and control in urban runoff, such institutional measures as those dealing with animal waste
control, preservation of stream corridors, and the prevention of increased runoff loads in
developing areas are of particular applicability."
Although nearly all of the study communities have moved beyond laws requiring
curbing of dogs to more modern dog waste control ordinances, a few have only leash laws.
In areas where dog clean-up laws are in place, enforcement has proven extremely difficult.
Only in Scarsdale did the official interviewed state that implementation appeared
"reasonably effective," because of the patrolling activities of local dog wardens.
In addition to continued vigorous emphasis on public education in this area,
municipalities should give consideration to the imposition of a street sweeping tax to be
added to dog licence fees. Fees could be applied toward purchase of vacuum street
sweepers capable of collecting the fine particles in which coliform is eventually
concentrated. Where waste clean-up ordinances cannot be effectively enforced,
municipalities should stress that dogs not be "curbed" (as was required in older
regulations), but rather walked in turfed areas where runoff can be minimized.
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Contacts
Town of Harrison
Bill Morgenroth, City Engineer
Tom DiBono, Superintendent of Highways
Village of Larchmont (not in Harbor watershed)
Wally Erwin, formerly of CZM Commission
Frank Devore, Asst. Village Engineer
Village of Mamaroneck
Paul Noto, Mayor
Paul Ryan, Chair of CZM Commission
Allen Lilliquist, CZM Commission
Joe Frioli, Village Manager
Benedict Salanitrp, Asst. Village Engineer
Les Zakarin, Engineering Dept.
Town of Mamaroneck
Phyllis Whinner, Chair of CZM Commission
Claudia Ng, CZM Commission Staff
Steve Altieri, Town Administrator
Gary Trachman, Consulting Engineer
Joe Patemo, Highway Dept.
Village of Pen Chester
Patrick Cleary, Village Planner
Billay Summa, Highway Foreman
John Myers, Dir, Building Dept.
Michael Ritchie, Village Manager
CitvofRve
George Motterella, City Engineer
Fred Zepf, City Planner
Village of Rve Brook
Rocko Circosta, Dir., Building Dept.
Village of Scarsdale
Dick Haggbladd, Village Engineer
George Jacob, Dept of Public Works
Steve Pappalardo, Assistant to the Mayor
Peter Van der Water, Village Planner
Valerie Woodbine, Asst. Village Planner
Citv of White Plains
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Buddy Nicolletti, Deputy Commissioner of Public Works
Ed Steinberg, Dir., Dept. of Planning
Phillip Amicone, Building Depu
County of Westchester
Laura Tessier, Soil and Water Conservation District
Susan Gallion, Environmental Quality Commission
Bob Materazzo, Dept. of Environmental Facilities
Richard Doran, Dept. of Health
State of New York
Charles Manfredi, DEC
Phil Digitano, DEC
Charlie Morrison, CZM, Dept. of State
, Bill Monon, CZM, Dept. of State
U.S. EPA
Barbara Finazzo, Region n
Jo Brecher, Region U
Rosemary Monihan, Region-1
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References
City of Rye, 1987. Local Waterfront Revitalization Program. New York State Dept. of
State. August, 1987.
County of Westchester and Village of Maraaroneck, N.Y., 1987. Mamaroneck Harbor
Pollution Study. Final Report. Sanenhwaite Associates, Inc., West Chester, PA.
Cowen, W.F. and Lee, G.F., 1976. "Phosphorus Availability in Particualte Materials
Transported by Urban Runoff," J. of the Water Pollution Control Federation, v.
48. No. 3.1976.
Cowen, W.F. et al, 1976. "Nitrogen Availability in Urban Runoff," J. of the Water
Pollution Control Federation, v. 48, No. 2, Feb., March, 1976.
Dennis, Jeffrey. 1986. "Phosphorus Export from a Low-Density Residential Watershed
and Adjacent Forested Watershed." in Lake and Reservoir Management. Vol. D.
North American Lake Management Society, 1986.
DiToro, D.M. and M.J. Small. 1979. "Stormwater Interception and Storage," J. of the
Environmental Engineering Division. ASCE, Vol. 105, No. EE1, Proc Paper
14368.
Driscoll, Eugene, 1982. "Analysis of Detention Basins in the EPA NTJRP Program," in
Proceedings of the Conference on Stormwater Detention Facilities Planning.
Design. Operation, and Maintenance (William DeGroot, ed.) American Society of
Civil Engineers, New York, NY.
Harrington, Bruce. 1986. "Feasibility and Design of Wet Ponds to Achieve Water Quality
Control." Maryland Water Resources Administration. Sediment and Stormwater'
Div., MDNR, Annapolis, MD.
Heaney, J.R. et al, 1976. "Storm Water Management Model. Level 1. Preliminary
Screening Procedures." EPA 600/2-76-275. U.S. EPA. Cincmatti. OH.
Heufelder, G. et al, 1989. "Potential effects of nutrient loading on bacterial contamination
levels in enclosed estuaries." Paper presented at the Buzzards Bay Symposium,
Woods Hole, MA, February 7-8,1989.
Hey, Donald L. and Gary C. Schaefer, 1983. "An evaluation of the Water Quality Effects
of Detention Storage and Source Control." Prepared for the Northeastern Illinois
Planning Commission for U.S. EPA Nationwide Urban Runoff Program.
Hoffman, Eva J. et al, 1985. "Stormwater Runoff from Highways," Water. Air, and Soil
Pollution. 25: 349-364.
Hoffman. Eva J. et al., 1982. "Petroleum Hydrocarbons in Urban Runoff from a
Commercial Land Use Area," J. of Water Pollution Control Federation. 54(11V
1517-1525.
Hoffman, Eva J., et al, 1983. "Annual Input of Petroleum Hydrocarbons to the Coastal
Environment via Urban Runoff," Canadian J. of Fisheries and Aquatic Sciences.
40: 41-53.
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Hohberg, R.P, 1984. "Downstream analysis of East Creek, tributary to Mamaroneck
Harbor (Drain or Sewer?)" Unpublished document, 1984.
Long Island Regional Planning Board, 1982. The Long Island Sepncnt of the Nationwide
Urban Runoff Program. Hauppauge, N.Y.
Long Island Regional Planning Board, 1984. "Non-point Source Management Handbook."
Hauppauge, New York, 1984.
Maryland Dept. of Natural Resources, Water Resources Administration. 1986.
"Maintenance of Stormwater Management Structures, A Departmental Summary."
Sediment and Stormwater Division, Water Resources Administration, MDNR,
Annapolis, MD.
Maryland Dept. of Natural Resources, Water Resources Administration. 1984. "Maryland
Standards and Specifications for Stormwater Management Infiltrations Practices."
Sediment and Stormwater Division, Water Resources Administration, MDNR,
Annapolis, MD.
McElroy, A., et al, 1976. Loading Functions for Assessment of Water Pollution from
Nonpoint Sources. U.S.EPA 600/2-76151. US.EPA, Washington, D.C.
Metropolitan Washington Council of Governments, 1983. An Evaluation of the Costs of
Stormwater Management Pond Construction and Maintenance. U.S.EPA
Nationwide Urban Runoff Program, Wahsington, D.C.
Metropolitan Washington Council of Governments, 1987. Controlling Urban Runoff: a
practical manual for planning and designing urban BMPs. July, 1987.
Murphy, Cornelius B. et al 1981. "Best Management Practices Implementation -
Rochester, New York." U.S. EPA Great Lakes National Program Office,
Chicago, IL EPA-905/9-81-002.
Myers, J.C., 1988. Governance of Non-point Source Inputs into Narrapansett Bav: A
Plan for Coordinated Action. Narragansett Bay Project (R.I.D.E.M./U.S. EPA),
Providence, R.I.
New Jersey Dept. of Environmental Protection, Div. of Water Resources. 1986. "A Guide
to Stormwater Management Practices in New Jersey."
New York State Dept. of Environmental Conservation, "Management Practices for
Controlling Stormwater Runoff," (no date).
Northern Virginia Planning District Commission, 1979. "Guidebook for Screening Urban
Nonpoint Pollution Management Strategies." Annandale, VA, 1979.
Northern Virginia Planning District Commission, 1987. "BMP Handbook for the Occoquan
Watershed." NVPDC, Annandale, Va. (Occoquan Basin Non-point Pollution
Program)
Northern Virginia Regional Planning District Commission, 1978. "Occoquan-Four Mile
Run Non-point Source Correlation Study." Dept. of Civil Engineering, Virginia
Polytechnic Institute and State University, Falls Church, Virginia.
-------
Oakland, Paul H. et al, 1983. "Summary Report: Durham Urban Runoff Program."
New Hampshire Water Supply and Pollution Control Commission, Concord, N.H.
Reckhow, K.H et al, 1985. "Pollutant Runoff Models: Selection and Use in Decision
Making." Water Resources Bulletin 21(21:185-95.
Satterthwaite Associates, Inc., 1986. "Comprehensive Stormwater Management Plan:
Beaver Swamp Brook Watershed, Westchester Co., N.Y." Sattenhwaite
Associates, Inc., West Chester, PA.
Small, M.J. and D.M. DiToro, 1979. "Stormwater Treatment Systems," J. of the
Environmental Engineering Div.. ASCE. Vol.105, No. EE3, Proc. Paper 14617.
Town of Mamaroneck and Village of Larchmont, 1986. Local Waterfront Revitalizarion
Program. New York State Dept. of State. Adopted 1986.
Town of Mamaroneck-Village of Larchmont Coastal Zone Management Commission, 1988.
"Feasibility Study of Remedial Actions for the Premium River-Pine Brook
Wetlands Complex." Malcolm Pimie, Inc., White Plains, New York.
U.S. Dept. of Agriculture, Soil Conservation Service. 1979. "Engineering Field Manual
for Conservation Practices." USDA, Washington, D.C.
U.S. Dept. of Agriculture, Soil Conservation Service. 1986. "Urban Hydrology for Small
Watersheds." Revised Technical Release Number 55. USDA, Washington, D.C.
U.S. Dept. of Commerce, National Oceanic and Atmospheric Admin., Office of Coastal
Zone Management and New York Dept. of State. 1982. New York State Coastal
Management Program and Final Environmental Impact Statement Albany, NY
1982.
U.S. Environmental Protection Agency, 1986." Methodology for Analysis of Detention
Basins for Control of Urban Runoff Quality." Office of Water, Nonpoint Source
Branch, Washington, D.C. (EPA 440/5-87-001).
U.S. Environmental Protection Agency. 1983. Results of the Nationwide Urban Runoff
Program, v. 1. Final Report. Water Planning Div., U.S. EPA, Washington, D.C.
NTIS PB 84-185552
U.S. EPA, 1984. "A Probabilistic Methodology for Analyzing Water Quality Effects of
Urban Runoff on Rivers and Streams." Office of Water, Nonpoint Source Branch,
U.S. EPA, Washington, D.C, 1984.
U.S. EPA, 1987. Guide to Nonpoint Source Pollution Control. Office of Water, Nonpoint
Source Branch, U.S. EPA, Washington, D.C, 1987.
U.S. Soil Conservation Service, 1988. "New York Guidelines for Urban Erosion and
Sediment Control," Syracuse, NY, rev. March 1988.
Versar, Inc. 1986. "Retention, Detention, and Overland Flow for Pollutant Removal from
Highway Stormwater Runoff- Interim Design Guidelines for Management
Measures." Federal Highway Admin., McLean, VA, 1986.
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Village of Mamaroneck, 1984. Local Waterfront Revitalizarion Program. New York State
Dept. of State. Adopted 1984.
Village of Mamaroneck, 1988. "Local Hood Control Washingtonville/Cential Business
District Comprehensive Study Sanitary and Stonnwater System." Phase I Report.
Blasland & Bouck Engineers, P.C.
Village of Port Chester, 1987. Local Waterfront Redevelopment Plan. New York State
Dept of State. June, 1987.
Westchester County Soil and Water Conservation District, 1984. "Stonnwater
Management." Best Management Practices Manual Series, Westchester Co. Dept.
of Planning, White Plains, New York.
Westchester County Soil and Water Conservation District, 1984. "Construction-Related
Practices." Best Management Practices Manual Series, Westchester Co. Dept. of
Planning, White Plains, New York.
Wiegand, C. et al. "Cost of Urban Runoff Quality Controls." Urban Runoff Quality:
Proceedings of an Engineering Foundation Conference, Urban Water Res.
ASCEyHenniker, NH, June 23-27,1986.
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Appendix I
Regulatory Controls in Place in Study Communities
Town of Harrison
I Governance of Stormwater
1) Summary: stoimwater controls in place
via subdivision regulations: Subdivision Regulations (SR) adopted June 3,
1981; amended June 22, 1982, March 3, 1988.
Subdivision ordinance, site plan review, and excavation ordinance
supplement one another. Overall lead agency is planning board.
Excavation applications are first reviewed by the engineering and building
departments.
a) name and reference number
SR 505.11
b) last amended
March 3, 1988
c) purpose of most recent revision
To incorporate some Beaver Swamp Brook recommendations. Certain
recommendations approved by the planning board but not yet adopted
formally; some require approval by the zoning board and others by the
planning board
d) revisions planned
further adoption of Beaver Swamp Brook (BSB) recommendations
2) Specify design storm?
a) what used (10,25 yrctc.)
25 yr specified in SR 505.11; in practice, use 100 yr
100 specified in BSB. Town doesn't attempt to detain water low in
watershed,but North of Union Ave, runoff detained. With 1 - 2
family lots, require dry wells; pass through applications to SWCD.
b) adopts/references SWCD recommendations?
references SWCD handbook and recommendations of SCS
c) used in practice? governing policies?
in practice use 100 yr
d) design storm varies by area of site?
design storm is 100 year; policy on holding water controls site-by-
site analysis
e) varies by percent imperviousness?
no; imperviousness not considered in subdivision regulations.
Imperviousness addressed via zoning; e.g. residential limit is 15
percent, increasing up to 35 percent in 50x100 lot district
Underground parking encouraged.
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Oboth?
g) same design storm used in practice
in practice use 100 yr
h) same for all locations in town?
3) Rate of runoff standard?
a) e.g., no increase for 5,10,25 year storms
Until 1988, no increase for 5-.IO-, and 25 yr storms. Amended
formally in '88 to stipulate no increase for 2 - 100 year storms
Provisions: for commercial and large subdivisions, require retention
For some single lots and 3-lot subdivisions, require dry wells.
If development contributes to floodplain storage needs in critical
areas, require retention galleries.
Division of basin: in upper 2/3, evaluation based upon specified
criteria
In lower 1/3: let water off.
In upper 1/3: policy to hold all runoff.
No specific requirements for small lots; controls based upon flood
control considerations
b) increase only if provided for by watershed plan
as per BSB Plan,-increase in lower third allowed based on timing of
peak flow
c) tie/reference SWCD BMPs
references SWCD handbook and recommendations of SCS
4) specified calculation method?
no
with small roof and paved area, calculation based upon yield of 2.5"
for 10 year storm, but credit given for existing conditions may
leverage calculation to 25 or 50 year storm
a) SWCD BMP manual reference?
b) TR-55; rational formula?
based upon site conditions
encourage indirectly: require retention for large subdivisions,
commercial areas, depending on recharge characteristics
6) consultation with SWCD
a) m.o.u. adopted; date
mou adopted 12/4/69; Town not active in stormwater management
until late 1970's
b) involvement of SWCD
refer all permit applications; no staff available to perform evaluations
7) Site-plan review required ?
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required by subdivision regulations; SR 502.3. Site plans also sent
to SWCD if for new building or increase in impervious coverage.
Site plan, subdivision analysis, and drainage analysis must be done
by site engineer.
a) by town engineer, department of public works, environmental coordinator
reviewed by town engineer; after completed and dedicated,
responsibility transferred to public works or highway department.
Planning board is lead agency on environmental impact review.
b) planning board, coastal commission, rcvitalization commission
c) zoning board and board of appeals
8) requirement for review/inspection of plans on-site? o
yes
a) beginning of project
For subdivisions, field inspectors go during construction
For commercial, after site plan approval, applicant goes to the
building dept, and they complete inspection. Engineers compare site
plan drawings to approved plans.
b) before back-fill
SR 800 engineer must be notified before back-fill
c) end of project
for subdivisions and for commercial, also review final as-built
d) associated with other facility inspections
yes: (utilities, erosion and sedimentation facilities, water mains,
curbs, paving) and footings, foundations, framing, plumbing.
Withhold occupancy permit until satisfied as to compliance.
Roads and public facilities are inspected by town engineer
9) requirement for review by through process or in as-built condition?
both, see above. Stormwater and erosion and sedimentation controls
go in early in project, sequenced with construction
10) fees
generally 4 percent of bond amount
a) via subdivision or site plan application
subdivision application fee
b) other permit application fees
c) review and inspection fees
building permit fee schedule for commission review; separate fee for
inspection of roads and utilities
d) bonding requirements
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SR 703 maintenance bond required for 2 yrs; then infrastructure
taken over by town. Town maintains right to do work and back-
charge for failure due to construction.
For subdivisions, performance bond set at cost of construction for
all public improvements (roadways, utilities). May require letter of
credit for securities or bond. For lots sold to a subsequent
developer, original developer obligated to meet town performance
conditions before infrastructure can be dedicated to the town.
For subdivisions and site plan review, if facilities are insufficiently
maintained and improperly functioning, town can do repairs and
impose a lein on the property.
For commercial properties, no bond (all private property), no
occupancy permit.
Detention and retention facilities are owned by homeowners
associations and private property owners. No maintenance
requirements are imposed. No system for inspection; owners may be
contacted in response to neighbors' complaints.
11) long term inspection
ESC XIII ; engineer can go on-site at any time
(see individual specifications above)
a) at siting of other facilities
SR 800: engineer-must be notified before back-fill
b) access at any rime
c) ad hoc/ no scheduled inspection
ESC XIII ; engineer can go on-site at any time
12) Comments: ESC IXC requires notification of areas potentially
affected outside municipality
II Other Instruments
1) Floodplain management
Flood Damage Prevention Ordinance, Ch. 146, amended 1982. Under NFIP
in zoning ordinance, lowest flood elevation is 1 foot above 100 year flood
level. Use FIRMS. Control elevations and limit fill if in floodway; if in
flood fringe, limit to existing grade.
2) Erosion and Sediment Control
Erosion and Sediment Control Ordinance (ESC) adopted May 19, 1982
With site plans for subdivisions, applicant must submit erosion and
sedimentation plans. Town inspector reviews on-site sediment traps, hay
bales, fences.
3) Subdivision Ordinance
Subdivision Regulations (SR) adopted June 3, 1981; amended June 22,
1982, again in '88. (See previous sections re role in stormwater
management.)
4) Zoning Ordinance
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Zoning Ordinance (ZO) adopted Nov. 18, 1974, with amendments included
as of May 5, 1982.
Varianced by zoning board as well as planning board.
For larger zoning districts (1/2 acre or larger, a setback of 50 feet from any
stream or waterbody is required. For smaller lots, application is
transmitted through town boards, and town engineer sets specific
requirements on a site-by-site basis
Zoning board must enact a zone change if a "significant" variation from
specific classifications is requested. A set of criteria sets limiting
standards as to issues which can be considered and justification required.
5) Local Environmental Quality Review Act
Local Law No. 1 of 1977- Environmental Quality Review Act (EQRA)
March 16, 1977 (no major revisions have been adopted since inception)
6) Surface Water Control Ordinance
no. Practices handled through subdivision and zoning ordinances,
providing for no increase in rate of runoff.
7) Local Wetlands Protection Ordinance
Freshwater Wetlands Ordinance, Ch. 149 of code, adopted 1976.
Considering revisions with advise from SUNY experts. Applicants must
show wetlands on all submittals. Any development within 100 feet of a
wetland must be permitted. Work with SWCD on appropriate facilities.
8) Coastal and/or Waterfront Revitalization Ordinances
no
9) Excavation and Soil Removal, Ch. 133 of Code. Establishes standards,
permit and fee schedule for earth removal.
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Town of Mamaroneck
I Governance of Stormwater
1) Summary: Stormwater controls in place
Stormwater addressed via site plan approval process.
name and reference number
Local Law #3, Ch. 66A, Site Plan Approval, adopted 1984, amended in
1986 to address Stormwater.
last amended
1986
purpose of most recent revision
to address Stormwater
revisions planned
2) Specify design storm?
a) what used (10,25 yr etc.)
not specified
b) adpptsAeferences SWCD recommendations?
considered, but not mandated
c) used in practice? governing policies?
in general, used in practice. Also consider LWRP policies.
d) design storm varies by area of site?
e) varies by percent imperviousness?
f)both?
g) same design storm used in practice
h) same for all locations in town?
3) Rate of runoff standard?
a) e.g., no increase for 5,10,25 year storms
policy of no increase in rate of runoff considered site-by-site
b) increase only if provided for by watershed plan
no specific reference
c) tie/reference SWCD BMPs
no specific reference
4) specified calculation method?
no, generally use TR-55, except where use of rational method better
justified
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a) SWCD BMP manual reference?
not specific
b) TR-55; rational formula?
use revised TR-55 except where SWCD recommends rational method
5) emphasis of ordinance on groundwater recharge?
no
6) consultation with SWCD
a) m.o.u. adopted; date
'yes
b) involvement of SWCD
SWCD reviews proposals for planning board to provide guidance on
stormwater and construction practices.
7) on-site review of plans required?
Yes; staff involved depends on requirements and complexity; town
consulting engineers engaged as necessary.
a) by town engineer, department of public works,
depends on site
b) planning board, CZM commission, envir. coordinator
depends upon jurisdiction; Univ. of Larchmont may also be involved
c) zoning board and board of appeals
no
8) on-site inspection
except for erosion and sedimentation practices, generally associated
with other inspections
a) beginning of project
Yes; subdivision regulations require that erosion and sedimentation
plans must be reviewed before building permit is issued.
b) before back-fill
yes
c) end of project
For retention facilities, town engineering consultant does as-built
survey to verify volume specifications.
d) associated with other facility inspections (utilities, erosion and sedimentation
facilities, water mains, curbs, paving
yes
9) requirement for review by through process or in as-built condition?
Through process, but as-built drawing must be provided to town.
Site engineer must certify that work has been done according to
plans. Building inspector often finds problems "by chance,"
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according to consulting engineer. Finds that projects "require close
supervision."
10)fees
a) via subdivision or site plan application
subdivision permit fee required
b) other permit application fees
c) review and inspection fees
d) bonding requirements
Town prefers letters of credit.
11) long term inspection
a) at siting of other facilities
b) access at any time
access authority at any time, but no scheduled inspections
c) ad hoc/ no scheduled inspection
yes
II Other Instruments
I) Floodplain management
Town Law Ch. 28 controls alteration of natural floodplains, streams,
channels, .natural protective barriers; regulates construction of Hood
barriers; regulates activities in special flood hazard areas; prohibits
encroachment yielding increases in flood waters.
2) Erosion and Sediment Control
Enacting laws related to construction projects, referencing standards of
SWCD; limited to "construction-related activities."
3) Subdivision Ordinance
Subdivision ordinance governs drainage, water and sewer improvements,
traffic and parking, parks, playgrounds
3.1) Site Plan Approval
Town Local Law # 3, adopted in '84, requires submission of a plan for
proposed development and/or use. Must be submitted to planning board
certifying that proposed actions are consistent with standards of traffic,
parking, screening, landscaping, environmental quality, drainage and
sewage disposal.
Amended in 1986 as per commitment stated by Coastal policy 14, stating
intent to amend site plan approval process to control and regulate rates of
stormwater runoff in new developments. Amended to prohibit rate increase
on property or decrease in rate of runoff on adjacent property.
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4) Zoning Ordinance
Town Law Ch 89 establishes land use and density controls.
Amended in July, 1986 to create R-50 zone preserving "low density
shoreline character."
5) Local Environmental Quality Review Act
Local Law #4, adopted 1985 provides for environmental quality review
under procedure analogous to state SEQR where proposed actions
significantly affect the environment.
Revised in June, 1986 to designate and map as critical areas marsh wetland
complexes identified in the LWRP as of significant regulationsional value.
(administered by the Townwide Conservation Advisory Commission and
Water Control Commission)
6) Surface Water Control Ordinance
7) Local Wetlands Protection Ordinance
(administered by the Townwide Conservation Advisory Commission and
Water Control Commission)
Town Law Ch 88, adopted in mid-1970's designated wetlands, rainfall
drainage systems, ponds, lakes, reservoirs, and adjacent lands at specified
distances as "controlled areas" where certain actions would be prohibited
(dumping of debris or chemical waste) and others would be regulated by a
permit process (building excavation, diversion of flow, etc.)
In 1986, amended to conform to state law, create technical definition of
wetlands, limit flooding and erosion impacts in the affected watersheds,
incorporate a frewhwater wetlands map.
8) Coastal and/or Waterfront Revitalizanon
Coastal Zone Management Committee created by Town of Mamaroneck and
Village of Larchmont to draft LWRP. Several actions stated in the plan as
necessary in order to implement the program are related to stormwater
management issues.
a) intermunicipal watershed cooperation Both the Town of Mamaroneck
and the Village of Larchmont pledged to "initiate and participate in
intermunicipal mechanisms for better control of flooding, erosion, and
siltation through coordinate planning and management of shared watershed,
and to work with the SWCD and other concerned agencies to that end."
Related directly to LWRP Policies 14 and 14A; indirectly to Policies 5,
7/7A, 44, 44A
b) intermunicipal and County cooperation against pollution. Town and
Village pledged to initiate and participate in pollution control efforts with
neighboring municipalities and concerned county agencies, including
working toward timely repair of County sewers and construction of
adequate POTWs.
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Related directly to LWRP Policies 7/7A, 8, 10A, 14A, 30, 31, 33, 33A,
36, 37, 38, 44, 44A
c) pollution monitoring and control. Town and Village to "develop, with
County agencies, a systematic program to inspect, monitor, and report on
water quality and pollution sources and incidents; improve compliance with
regulations including safe disposal and/or recycling of polluting wastes;
and apply pollution guidelines set forth in County Best Management
Practices Manuals on Construction-Related Projects and Stormwater
Management.
Related directly to LWRP Policies 7/7A, 8, 10A, 14A, 30, 31, 33, 33A,
36, 37, 38, 44, 44A
d) Elimination of strom drain-sanitary sewer connections. Town and
Village to "give high priority to elimination of illegal connections of storm
drains to sanitary sewers, whether on private or municipal property..."
Related directly to LWRP Policy 33A
e) Litter and dog waste. Town and Vijlage to "study effective approaches
to control of these nuisances with a view to new legislative, administrative,
and/or community action."
Related directly to LWRP Policy 39A
0 Pollution from nutrients, etc. Town and Village to "follow best
management practices on municipal projects to greatest extent practicable,
and encourage property owners to do likewise, in order to minimize
pollution of coastal waters by runoff of excess nutrients, organics, and
eroded soils."
Related directly to LWRP Policy 37
9) Consistency Law
Local Consistency Law enacted in 1986 requiring that local government
actions, including granting of permits, be consistent to maximum extent
practicable with the policies and purposes of the LWRP, and establishing
procedures to assure such consistency.
10) Sewer Ordinance/Plumbing Code
Town Law Ch 60. Article VIII governs plumbing into sewers;
Article XII forbids connection between storm drains and sewers; prohibits
surface water connection from ground, cellar, or roof to discharge to
sewer, directly or inderectly.
Article XIV states that surface drains must connect only into storm drains.
Ill Miscellaneous Housekeeping Practices
1) Litter Control.
Town Law Ch. 30 establishes prohibition on littering of public areas
2) Dog Waste Control
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Town Law Ch. 6 Article 2 requires removal and proper disposal of pet
waste; forbids discharge of waste into storm drains
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Village of Mamaroneck
I Governance of Stormwater
1) Summary: stormwater controls in place
governed via Flood, Erosion, and Sediment Control (FESC), and
subdivision regulations
name and reference number
FESC, see below
last amended
purpose of most recent revision
revisions planned
Village attempting to revise regulatory structure to reflect LWRP policies
2) Specify design storm?
a) what used (10,25 yr etc.)
Land and Subdivision Regulations (LSR) VI le: 10 yr storm used for
establishing impact
b) adopts/references SWCD-recommendanons?
FESC 7.10(6) adopts SWCD stormwater management BMPs (100 yr
storm)
c) used in practice? governing policies?
yes
d) design storm varies by area of site?
may depend on location in watershed
e) varies by percent imperviousness?
no
Oboth?
g) same design storm used in practice
h) same for all locations in town?
3) Rate of runoff standard?
a) e.g., no increase for 5,10,25 year storms
b) increase only if provided for by watershed plan
FESC 9.60 and 7.10(6) no rate increase unless provided for in
comprehensive plan for watershed
c) tie/reference SWCD BMPs
Calculations required according to Westchester SWCD stormwater
BMPs (2-10-,IOO yr storms)
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4) specified calculation method?
FESC endorses use of SWCD stormwater BMPs
a) SWCD BMP manual reference?
Calculations required according to Westchester SWCD stormwater
BMPs (2-10-,IOO yr storms)
b) TR-55; rational formula?
TR-55, except where SWCD prefers use of rational method
5) emphasis of ordinance on groundwater recharge?
"no
6) consultation with SWCD
FESC 6.12 adopts stormwater BMPs
a) m.o.u. adopted; date
MOD adopted 10/3/85
b) involvement of SWCD
review plans as necessary
7) site plan review required by ordinance?
LSR V A2(d) general review of plans
a) by town engineer, department of public works, environmental coordinator
yes
b) planning board, coastal commission.conservation commission
yes
c) zoning board and board of appeals
no
8) review of plans/inspection on site o
a) beginning of project
b) before back-fill
c) end of project
d) associated with other facility inspections (utilities, erosion and sedimentation
facilities, water mains, curbs, paving
yes, except for special requirements or work in critical areas
9) requirement for review by through process or in as-built condition?
depends on site
10)fees
LSR III application fee
a) via subdivision or site plan application
fei
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11
b) stoimwater permit application
c) review and inspection fees
d) bonding requirements
LSR VI 14 - maintenance bond for five years; then facility taken over
by municipality
11) long term inspection
no regular schedule
a) at siting of other facilities
b) access at any time
c) ad hoc/ no scheduled inspection
II Other Instruments
I) Floodplain management
Local Law No. 35, 1984- Flood, Erosion and Sediment Control (FESC),
effective Dec. 24, 1984
2) Erosion and Sediment Control
Local Law No. 35, 1984- Flood, Erosion and Sediment Control (FESC),
effective Dec. 24, 1984
3) Subdivision Ordinance
Land Subdivision Regulations (LSR), adopter November 1964, with
amendments through Sept. 26, 1985
4) Zoning Ordinance
yes
5) Local Environmental Quality Review Act
Local Law 10-1987 - adopts State Environmental Qualitv Review Act
(EQRA), effective May 13, 1977
6) Surface Water Control Ordinance
7) Local Wetlands Protection Ordinance
8) Coastal and/or Waterfront Rcvitalizarion Ordinances
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Village of Port Chester
I Governance of Stormwater
I) Summary: Stormwater controls in place
via Local Law # 5, Ch. 98-23 Site Plan Review; section of zoning
ordinance
No program to address Stormwater specifically; reviewed case by case
name and reference number
Local Law # 5, Ch. 98-23 Site Plan Review
last amended
Local Law # 5 last amended May 27, '87 and June '87
purpose of most recent revision
LWRP-related revisions
revisions planned
2) Specify design storm?
a) what used (10,25 yr etc.)
25 year 24 hour duration; 5.7 inches of rain over impervious areas
b) adopts/references SWCD recommendations?
requires use of recommendations for site grading, erosion and
sedimentation
c) used in practice? governing policies?
d) design storm varies by area of site?
same design storm used uniformly
e) varies by percent imperviousness?
Paved areas use 25 year return frequency.
f)both?
g) same design storm used in practice
yes
h) same for all locations in town?
Yes; new one or 2 family homes use dry wells; if high water table,
applicant may be required to connect to storm sewer.
3) Rate of runoff standard?
a) e.g., no increase for 5,10, 25 year storms
25 year 24 hour duration; 5.7 inches of rain over impervious areas
b) increase only if provided for by watershed plan
"emphasize" use of retention/detention facilities
c) tie/reference SWCD BMPs
-------
reference
4) specified calculation method?
a) SWCD BMP manual reference?
use table in stormwater manual; Westchester 24 hr storm; rainfall 5.7
b) TR-SS; rational formula?
TR-55
5) emphasis of ordinance on groundwater recharge?
avoidance of stormwater runoff
6) consultation with SWCD
if adjacent to county roadway, municipal boards send copies to the
county including design and computations
a) m.o.u. adopted; date
no
b) involvement of SWCD
where county, state, or municipal boundaries are involved, copies
sent to county planning board,, or department of public works
7) site plan review required?
by zoning, ordinance
a) by town engineer, departmenrof-public works; environmental coordinator
b) planning commission, coastal commission, revitalization commission
planning commission reviews all applications other than 1-2 family
homes; coastal commission involved within jurisdiction of LVVRP'
c) zoning board and board of appeals
8) requirement for on-site review/inspection of plans
yes; via building inspection, and by town engineer. Consultant
occasionally hired to perform inspections of stormwater infiltration
facilities
a) beginning of project
footing; foundations; framing
b) before back-fill
c) end of project
d) associated with other facility inspections (utilities, erosion and sedimentation
facilities, water mains, curbs, paving
footing; foundations; framing
9) requirement for review through process or in as-built condition?
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Appendix I ] 7
certification of building inspector required; can withold occupancy
permit pending certification. Village does not require as-built
drawings; certification by building inspector (mostly developed
waterfront, soredevelopment predominant). Upon certification,
funding is released from lending institution to developer.
10) fees (based on cost of development: 4 to 5 percent) environmental
application form; fee for site plan review; no impact fee
a) via subdivision or site plan application
b) other application fees
NA
c) review and inspection fees
see above
d) bonding requirements
subject to planning commission discretion in Ch. 98-23; certification
of occupancy denial generally preferred; I year to complete
landscaping. For improvements, minimum of $5000 is authorized,
but planning commission may waive and usually does.
11) long-term inspection
not scheduled
a) at siting of other facilities
b) access at any time
c) ad hoc/ no scheduled inspection
not scheduled
II Other Instruments
I) Floodplain management
Regulations incorporated in Ch 39 of Village code, revised early '87 to .
address new FIRM. Regulationsulates development within flood hazard
areas as defined by FIRM. "Outlines" method to use in assuring that
buildings are sited so as to minimize property damage and endangerment
(references Policy 11 of LWRP).
"Recommends" nons-structural means of flood damage prevention.
Administered by planning department.
2) Erosion and Sediment Control
3) Subdivision Ordinance
Applicants referred to planning commission for recommendation to board of
trustees. Trustees approve or deny; then applicant referred to county if
applicable.
Ch. 98-16 recently revised cluster development zone for large
subdivisions.
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Appendix i
3.1) Site Plan Review
S. 98 23 of Village Code. Required for all residential developments over
1-2 family and all commercial. Revised site plan review requirements in
late '86 to require three phase submission process: set review criteria,
submission standards, site development standards, other miscellaneous
requirements
Outlined requirements for stormwater management; established municipal
standards for all aspects of review.
S. 98* 23 of Village Code governs drainage
4) Zoning Ordinance
S. 98 of Village Code; percent coverage requirement-varies by zoning
classification
5) Local Environmental Quality Review Act
Ch. 36 B of Village Code. Implemented SEQR. LWRP Policies #31-39
and 44 referenced local EQRA. Repealed due to "conflicts with site plan
review." (repeal recommended by LWRP consultant) Village relies on state
SEQR.
6) Surface Water Control Ordinance
no
7) Local Wetlands Protection Ordinance
no; use wetland designations provided on FIRM
8) Coastal and/or Waterfront Revitalization Ordinances
administered by planning department; no revisions made to draft plan
Waterfront Commission reviews projects for consistency with LWRP.
Refers decisions to planning commission. Advisory only.
9) Sewer Ordinance
Ch. 73 of Village Code; includes standards and conditions for connection.
Sewage distribution includes all of Port Chester and parts of Rye Brook.
Includes prohibition on connection of roof drains, basement drains, sump
pumps, etc. to sanitary sewer.
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City of Rye
I Governance of Stormwater
1) Summary: stonnwater controls in place
regulated via surface water control authority
name and reference number
Surface Water Control Ordinance (SWC) adopted April 23 1975.
SWC 173: comprehensive coverage of surface water quality
Surface Water Control Amendments (SWCA) adopted Aug., 1987. Drafted
as component of the Beaver Swamp Brook management initiative; provides
for control of 100 year storm unless otherwise indicated in the Beaver
Swamp Brook Plan.
SWCA 173: amended along with other related ordinances according to the
provisions of the Local Waterfront Revitalization Plan
purpose of most recent revision: consistency with LWRP
revisions planned: see below
2) design stormspecified:
a) what used ?(10,25 yr etc.)
SWCA I73-4A(4): 10 yr storm
b) adopts/references SWCD recommendations? An amendment has been
proposed to incorporate the SWCD recommendations
c) used in practice? to the extent practicable
d) design storm varies by area of site?
4 acres or more requires 100 yr storm
e) governing policies? See LWRP III (p. 54); on-site retention facilities
required except in specificed circumstances.
f) varies by percent imperviousness?
With 75 % imperviousness or more, City requires design for 100 yr
storm.
g)both?
If less than 4 acres, with less than 75 % imperviousness, City
requires 25 yr storm design.
h) same design storm used in practice?
no, see above
i) same for all locations in town?
if in Beaver Swamp Brook, must consult with model
3) Rate of runoff standard?
a) e.g., no increase for 5,10,25 year storms
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SWC I73-4A(4) no rate of runoff increase for 10 yr storm
SWCA I73-4A(4): a) if 100 yr design storm required, no rate of
runoff increase in 100-, 50-, 25-, 10- or 2- year storms, b) if 25 yr
design storm required, no rate of runoff increase in IOO-, 50-, 25-,
10- or 2- year storm.
b) increase only if provided for by watershed plan? yes
c) tic/reference SWCD BMPs
4) specified calculation method? no
a) SWCD BMP manual reference?
b) TR-55; rational formula?
SWCA-I73-4A use TR 55
5) emphasis of ordinance on groundwater recharge?
encourages indirectly
6) consultation with SWCD
a) m.o.u. adopted; date
MOU adopted 7/12/84
b) involvement of SWCD
7) site plan review required ?
yes
a) reviewed by town engineer, department of public works, environmental
coordinator
SWC: city engineer reviews permit application
b) planning board, coastal commission, revitalization commission
c) zoning board and board of appeals
d) other town planner; town engineer
8) requirement for review/inspection of plans on-site o
a) beginning of project
b) before back-fill
c) end of project
d) associated with other facility inspections (utilities, erosion and sedimentation
facilities, water mains, curbs, paving
Yes
9) requirement for review through process or in as-built condition?
as-built
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10) fees
a) via subdivision or site plan application
b) other application fees
SWC 173-1 permit required
SWC 173-6 inspection fee
c) review and inspection fees
SWC 173-6 inspection fee
d) bonding requirements
no maintenance bond required
11) long-term inspection
a) at siting of other facilities
b) access at any time
not regular; engineer can go on-site at any time
c) ad hoc/ no scheduled inspection
II Other Instruments
I) Floodplain management
yes
2) Erosion and Sediment Control
via proposed amendment to subdivision regulations
3) Subdivision Ordinance
Ch. 170 Subdivision Regulations: City has proposed sediment and erosion
control amendments; will incorporate County regulations to protect fish and
wildlife habitat as per Coastal policies 31,33,37
3.1 Site Development
Proposal to incorporate County erosion and sedimentation regulations as
above
4) Zoning Ordinance
Zoning Ordinance (ZO) last amended June 15, 1983
Final amendments to the LWRP provide for waterfront recreation districts
and conservation districts. Conservation districts reference minimum site
sizes, set floor to lot area ratios of 10 percent and require maintenance of
50 percent natural ground cover.
5) Local Environmental Quality Review Act
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6) Surface Water Control Ordinance
Surface Water Control Ordinance (SWC) adopted April 23 1975
SWC 173 requires city permit to grade, excavate, construct, remove
vegetation, or alter flow of surface water.
Surface Water Control Amendments (SWCA)
SWCA 173 amendments will adopt county erosion and sedimentation
regulations as outlined in Appendix C of Coastal policy
7) Local Wetlands Protection Ordinance
When final Freshwater Wetlands maps have been filed, City can improve
over state jurisdiction (12.5 acres) via Ch. 102 of Rye City Code
Dredge and fill is regulated via Art. 15, 24, 25, 34 of NY Environmental
Conservation Law. Activities must also be consistent with Coastal policies
7, 24, 15, 26, 44.
Waiver of city permit up to 100 c. yds of fill for erosion restoration or silt
removal. Bonding provisions: 20 percent or up to $5000. Bond released
upon certification of surveyor.
All freshwater and tidal wetlands are under jurisdiction of Rye city code
Ch. 92, require planning commission approval, and must conform with
standards of
Ch 197 . 10 of Rye City Code and state and Corps of Engineers
requirements.
8) Coastal and/or Waterfront Revitalization Ordinances
Policy 33: states that use of structural approaches (detention basins,
separating CSO's) infeasible. States non-structural approaches (street
cleaning, reduced road salting) to be encouraged.
Policy 37: BMPs will be used to minimize nonpoint source discharge of
excess nutrients, organics, eroded soils into coastal waters
Policy 44: Provides for preservation and protection of tidal and freshwater
wetlands and preservation of benefits derived; definition of wetlands and
ecological zones references NY Freshwater Wetlands Act and NY
Protection of Waters Act.
Wetlands are delineated in the Natural Resources Inventory, to be updated
Final amendments to the LWRP provide for waterfront recreation districts,
conservation districts. Conservation districts reference minimum site sizes,
set floor to lot area ratios of 10 percent, and require maintenance of 50
percent natural ground cover.
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Village of Rye Brook
I Governance of Stormwater
1) Summary: stomiwater controls in place
via site plan review process (subdivision rule) Local Law #5.3.2
name and reference number
Local Law #5.3.2 Subdivision Ordinance, governing drainage
improvements
last amended
1988
purpose of most recent revision
revisions planned
2) Specify design storm?
a) what used (10,25 yr etc.)
Retention of 100 yr frequency storm is required for all sized lots.
b) adopts/references SWCD recommendations?
c) used in practice? governing policies?
uses SWCD recommendations in practice
d) design storm varies by area of site?
e) varies by percent imperviousness?
f)both?
g) same design storm used in practice
h) same for all locations in town?
3) Rate of runoff standard?
a) e.g., no increase for 5,10,25 year storms
b) increase only if provided for by watershed plan
c) tie/reference SWCD BMPs
4) specified calculation method?
refers to SWCD recommendations
a) SWCD BMP manual reference?
b) TR-55; rational formula?
5) emphasis of ordinance on groundwater recharge?
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6) consultation with SWCD
refers projects to SWCD
a) m.o.u. adopted; date
adopted
b) involvement of SWCD
7) site plan review required ?:
a) reviewed by town engineer, department of public works, environmental
coordinator
town engineer, building department, department of public works,
highway superintendent, as needed
b) planning board, coastal commission, revitalization commission
c) zoning board and board of appeals
8) requirement for on-site inspection/ review of plans
yes
a) beginning of project
erosion/sedimentation controls inspected initially
b) before back-fill
c) end of project
for improvements, certification required from a professional
engineer; project engineer generally not the designer involved in the
project; changes in the design should be cleared with the building
department
d) associated with other facility inspections (utilities, erosion and sedimentation
facilities, water mains, curbs, paving
other controls inspected in concert with review of footing,
foundation, framing, plumbing, etc.
9) requirement for review by through process or in as-built condition?
as-built plans prepared by site contractor, reviewed prior to
acceptance of dedicted public facilities
10) fees
a) via subdivision or site plan application
nominal fee required for planning procedure
b) other application fees
c) review and inspection fees
Codified provision for environmental review fee, which is required
to support town's hiring of a consulting engineer to review plans,
advise town re incorporation of SWCD drainage recommendations,
and/or perform inspections as needed. Applicant is required to pay
$5000 into an environmental account, which can be increased as
-------
needed. 3-lot subdivisions are required to submit $1000. Village
board establishes fee rates.
d) bonding requirements
Performance bonds are required only for municipal improvements,
primarily in subdivisions. All site work relating to street drainage
and storm drains is covered. Bonds are not collected for detention
basins as of now.
Village can impose maintenance bonds, held for one year, on
facilities to be dedicated to the municipality. Maintenance bonds are
also imposed for utilities, in which terms are specified in
- homeowners' agreements. In case of malfunction, Village can
perform work and backcharge or place a lein on the property.
Village prefers letters of credit; as being easier to administer than
bonds.
11) long-term inspection
a) at siting of other facilities
b) access at any time
right of access at-any time
c) ad hoc/ no scheduled inspection
no scheduled inspections
II Other Instruments
1) Floodplain management
Flood Damage Prevention Law: Local Law # 7 of 1987. Recentlv adopted
FEMA guidelines.
2) Erosion and sediment control:
Local Law # 17 of 1984. Required BMPs based on SWCD Construction
Activities Manual
3) Subdivision regulations:
Local Law # 3 of 1985,
Local Law #1 of 1988 relating to cluster developmerl
3a) Site plan review:
Local Law #28 of 1984
4) Zoning Ordinance
density controls: categories address maximum percent lot coverage
5) Local Environmental Quality Review Act
no
6) Surface Water Control Ordinance
no
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Appenau i 2 6
7) Local Wetlands Protection Ordinance
no local ordinance
8) Coastal and/or Waterfront Revitalization Ordinances
no
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Village of Scarsdale
I Governance of Stormwater
1) Summary: stormwater controls in place
regulated by the planning board via subdivision review, and site plan
review
name and reference number
Local Law #7, 1985, restricting lot coverage and percent impervious area in
all building permits
last amended
purpose of most recent revision
revisions planned
2) Specify design storm?
a) what used (10-, 25- yr etc.)
25- yr for new subdivisions unless conditions warrent otherwise;
2-,5-,IO-, and 25- for other properties less than 2 acres;
100- yr for properties exceeding 2 acres
b) adopts/references SWCD recommendations?
adhere in practice; not referenced.
c) used in practice? governing policies?
abide by policy to allow no increase in rate of runoff
d) design storm varies by area of site?
yes, see above
e) varies by percent imperviousness?
if existing coverage exceeds stipulations, owner must obtain a
variance from the board of appeals.
A restrictive covenant is then placed on the deed to ensure
compliance with terms of varianc.
f)both?
g) same design storm used in practice
no
h) same for all locations in town?
board makes decision based on a hearing, including presentation of
staff evidence on watershed considerations
3) Rate of runoff standard?
a) e.g., no increase for 5,10,25 year storms
use SWCD recommendations
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b) increase only if provided for by watershed plan
c) tie/reference SWCD BMPs
4) specified calculation method?
TR 55 unless lot involved is very small
a) SWCD BMP manual reference?
b) TR-55; rational formula?
5) emphasis of ordinance on groundwater recharge?
no
6) consultation with SWCD
a) m.o.u. adopted; date
1985 or 1986
b) involvement of SWCD
reviews applications as necessary, comments as necessary
7) site plan review required?
Codified in planning board operating rules and regulations.
Required for non-residential buildings in residential* or commercial
zone, interior lots, flag lots, cluster developments -
a) by town engineer, department of public works, environmental coordinator
reviewed by engineer and Village planner
b) planning board, coastal commission
reviewed by planning board
c) zoning board and board of appeals
8) requirements for on-site review and inspection
handled by engineer and building department, depending on facilities
involved; no specified schedule
a) beginning of project
b) before back-fill
c) end of project
d) associated with other facility inspections (utilities, erosion and sedimentation
facilities, water mains, curbs, paving)
yes
9) requirement for review by through process or in as-built condition?
Right of entry not provided for; applicant's own engineer inspects as
installed. Applicant's engineer provides as-built drawing at the end
of a project; town engineer and building inspector compare with
-------
approved plans. Revisions of plans through the project require re-
approval
10) fees
a) via subdivision or site plan application
b) other application fees
c) review and inspection fees
planning board review fee of $100; repeat reviews completed at no
charge
d) bonding requirements
For facilities to be dedicated (roads, utilities, stormwater retention
basins), require 80 % bond, 20 % cash. Impose maintenance bond
after construction is complete, when performance bond is requested
back. Higher bond is required if construction appears flawed.
11) long term inspection
a) at siting of other facilities
b) access at any time-
c) ad hoc/ no scheduled inspection
no access provision, no scheduled inspection
II Other Instruments
I) Floodplain management
Local Law # 3 of 1980 incorporated Final FIRM;
Local Law #8 of 1987 repealed earlier regulations; adopted new FEMA rules
2) Erosion and Sediment Control
Construction-related methods required on plans; placement specificatins
required on plan drawings
3) Subdivision Ordinance
Local Law #7, 1985
3a) Site Plan Review
Codified in operating regulations of the planning board.
4) Zoning Ordinance
no change since 1960's
5) Local Environmental Quality Review Act
Local Law #2, 1979 adopted SEQRA at local level
6) Surface Water Control Ordinance
no, but county stream protection program prohibits obstruction or diversion
of certain streams
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7) Local Wetlands Protection Ordinance
Local Law #3 of 1976
Defines wetlands, controls activities within 100 feet of wetlands of any
size. Also governs dredge and fill and vegetation disturbance
8) Other
Local Law #10 of 1987 prohibits stream and water obstructions.
A permit is required to fill or divert any stream or water course from its
natural course.
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City of White Plains
I Governance of Stormwater
1) Summary: stormwater controls in place
Via site plan approval.
Zoning Ordinance S. 7.5.3.7 establishes criteria regulationsarding
stormwater.
All construction except 1 to 2 family homes requires site plan approval,
including change in existing use.
name and reference number
Zoning Ordinance S. 7.5.3.7
last amended
June, 1981
purpose of most recent revision
revisions planned
2) Specify design storm?
a) what used (10,25 yr etc.)
no calculation method specified
All project applicants must calculate expected drainage loads and
runoff patterns to be accommodated. Review by department of
public works
b) adopts/references SWCD recommendations?
MOU in place.
c) used in practice? governing policies?
TR 55 used in practice. Attempt to avoid rate of runoff increase in
undeveloped areas, by requiring detention and retention containment.
d) design storm varies by area of site?
Professional city staff determine case-by-case.
e) varies by percent imperviousness?
As a practical matter, 20 percent of area must be retained as usable
open space in the downtown district; however not required to
upgrade to permeable surface.
Oboth?
g) same design storm used in practice
see above
h) same for all locations in town?
yes
3) Rate of runoff standard?
a) e.g., no increase for 5, 10,25 year storms
As a matter of practice, conform to SWCD BMPs
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b) increase only if provided for by watershed plan
c) tie/reference SWCD BMPs
MOU in place.
4) specified calculation method?
a) SWCD BMP manual reference?
b) TR-55; rational formula?
Primarily use TR-55
5) emphasis of ordinance on groundwater recharge?
no
6) consultation with SWCD
a) m.o.u. adopted; date
yes
b) involvement of SWCD
detention/retention facility design review
7) site plan review procedure
Submitted to Building Department and referred to other applicable-
staff departments, to the planning board, the design review board, all
others having jurisdiction
a) by town engineer, department of public works, city planners
yes
b) planning board, other technical commissions and boards
yes, Environmental Officer operating out of the Planning Department
acts.as principal advisor to approving agencies as regulationsards to
what actions are necessary, threshold determinations, etc.
c) zoning board and board of appeals
8) on-site review/inspection of plans required?
Building department imposes composite conditions of approving agencies,
conducts inspections except in fragile areas, where other staff may be
involved.
a) beginning of project
yes
b) before back-fill
yes
c) end of project
yes; to ensure conformance with as-built drawings
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J J
d) associated with other facility inspections (utilities, erosion and sedimentation
facilities, water mains, curbs, paving
yes
9) requirement for review by through process or in as-built condition?
Building Department reviews as-built drawings; re-submits to staff
departments to ensure compliance, requires correction if necessary.
10) fees
a) via subdivision or site plan application
basic $100 fee submitted to Building Department with original
application
b) site plan application
c) review and inspection fees
d) bonding requirements
City has authority to impose maintenance requirements for dedicated
facilities and private factilities. Can perform work and back-charge
or impose lein on property. City prefers letters of credit to bonds,
due to administrative advantages.
11) long term inspection
a) at siting of other facilities
b) access at any time
See above.
c) ad hoc/ no scheduled inspection
See above.
II Other Instruments
I) Floodplain management
Use most recent Flood Insurance Rate Maps (FIRMs) as guidance
2) Erosion and Sediment Control
via site plan approval and SWCD BMP manuals.
Except in fragile areas, inspection handled by the building inspector.
No restrictions per se on steep slope development.
3) Subdivision Regulations
Regulations currently being revised. Approval under authority of the
planning board. Regulations standard regulationsarding drainage: require
"provision of adequate storm and surface water drainage." Storm drains
must meet the requirements of the Department of public works.
3.1) Site Plan Review
Zoning Ordinance S. 7.5.3.7 establishes criteria regulationsarding
stormwater.
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All construction except 1 to 2 family homes requires site plan approval.
Process determined by number of parking spaces: if less than 50, planning
board reviews; if more than 50, town council reviews.
Commissioner of Public works may require submission of engineering
reports for redevelopments.
4) Zoning Ordinance
Zoning Ordinance S. 7.5.3.7 establishes criteria regulationsarding
stormwater.
5) Local Environmental Quality Review Act
Local procedures follow state regulations. SEQRA "more than adequate for
review of existing and potential problems."
6) Surface Water Control Ordinance
no
7) Local Wetlands Protection Ordinance
.Adopted 1976. Although the planning board was given authority to develop
rules and regulations, this was never accomplished as a matter of law. As
a matter of practice, two wetland areas have been defined within the city,
are reflected in the building code, and are reviewed as per SEQRA authority
via the site plan review. No formal requirements have been established.
8) Sewer Ordinance
Prohibits hookup of storm drainage facilities to sanitary sewers.
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PAGE NOT
AVAILABLE
DIGITALLY
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Appendix B
v.
ANALYSIS OF
BEST MANAGEMENT PRACTICES IN
MAMARONECK HARBOR WATERSHED
-------
FINAL REPORT
on
ANALYSIS OF BEST MANAGEMENT PRACTICES
IN THE MAMARONECK HARBOR WATERSHED
to
U.S. Environmental Protection Agency
Office of Marine and Estuarine Protection
September 15. 1989
Contract No. 68-C8-0105
Work Assignment No. 30
BATTELLE MEMORIAL INSTITUTE
Duxbury Operations
397 Washington Street
Duxbury, MA 02332
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TABLE OF CONTENTS
Page
1.0 INTRODUCTION 1
1.1 ACTION PLAN HISTORY 1
1.2 WATER QUALITY MODELING 2
1.3 SUB-BASIN MONITORING PROGRAM 3
2.0 REVIEW OF BEST MANAGEMENT PRACTICES 6
2.1 EVALUATION OF BMPs IN MAMARONECK HARBOR 6
2.2 FECAL COLIFORM REDUCTIONS BY STRUCTURAL BMP 6
2.2.1 Dry Detention Basins 7
2.2.2 Wet Detention Basins 7
2.2.3 Extended Detention Dry Basins 8
2.2.4 Infiltration Basins and Dry Wells 8
2.2.5 Permeable Pavements 8
2.2.6 Vegetative Measures 9
2.2.7 Storage in the Receiving Water 9
2.3 FECAL COLIFORM REDUCTIONS BY HOUSEKEEPING BMP 10
2.3.1 Catch Basin Cleaning 10
2.3.2 Lawn Care-Related Controls 11
2.3.3 Street Cleaning 11
2.3.4 Litter Control 12
2.3.5 Pet Waste/Animal Waste Ordinances 12
3.0 RECOMMENDATIONS 12
4.0 LITERATURE CITED 13
LIST OF FIGURES
FIGURE 1. Hal stead Avenue East Outfall/Storm Sewer System 4
FIGURE 2. North Barry Avenue Outfall/Storm Sewer System 5
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1.0 INTRODUCTION
1.1 ACTION PLAN HISTORY
Federal funds have been made available through the National Estuary
Program to initiate implementation of priority action plans in estuaries that
are developing comprehensive conservation and management plans. As part of
the Long Island Sound Study, a demonstration action plan has been developed to
address management of stormwater flows in Mamaroneck Harbor.
At present, the beaches in Mamaroneck Harbor must be periodically closed
during the summer following rainfall because of coliform contamination.
Previous work has indicated that stormwater runoff and sanitary sewer
overflows are the major contributors to the elevated coliform levels that
occur in the harbor following rain. The sewer overflow problem is currently
being addressed through the negotiation of Judicial Orders on Consent by the
State of New York. To address the elevated levels of coliform bacteria in
stormwater, Best Management Practices (BMPs) that can help reduce coliform
loadings in stormwater runoff have been identified and evaluated.
Several meetings have been held with representatives of the communities
in the watershed to explain the program and its goals. The communities have
enthusiastically supported the program.
The BMPs utilized by the communities in the Mamaroneck Harbor Watershed
have previously been identified in a report entitled "Evaluation of Best
Management Practices in the Mamaroneck Harbor Drainage Basin (Myers, 1989)."
This report will address the effectiveness of these BMPs in reducing fecal
coliform loadings in stormwater by reviewing of technical literature. Myers1
report will serve as an addendum to this report. The removal efficiency,
coupled with the effectiveness of implementation from a political and economic
viewpoint supplied by the local communities, will be the basis for ranking the
BMPs. One or more of the BMPs will then be selected for implementation and
will serve as a demonstration project in Mamaroneck Harbor. The results will
then be used to predict the impact of "full implementation" throughout the
watershed.
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1.2 WATER QUALITY MODELING
The primary purpose of the water quality assessment is to quantify the
impacts of urban runoff on water quality and to determine the degree to which
runoff may continue to cause use impairment after controls are implemented.
The objectives are to provide a methodology and guidelines to assess
stormwater and nonpoint source impacts on water quality, to illustrate how
mathematical water quality modeling can be used to assess water quality issues
in Long Island embayments, and to provide an initial technical format for
developing permit limitations for stormwater discharges.
An urban stormwater model was developed in a previous investigation
(Satterthwaite Associates, 1987). The loading rates generated by this model
are a primary cause for concern about urban stormwater runoff.
A time-varying water quality model (AESOP) for the harbor has been
developed based on physical characteristics of the study area. This time-
varying water quality model and the urban stormwater model will simulate
typical summer conditions; the urban runoff model will generate coliform
loading rates and the water quality model will calculate receiving water
responses. Statistical analyses will provide a quantitative basis for
determining whether urban runoff will continue to cause use impairment after
other controls related to infiltration/inflow into the sanitary sewer system
are implemented. If use impairment is attributed to urban runoff, the
analysis will define the percent reduction of coliform discharge rates
necessary to achieve water quality objectives.
The urban stormwater model developed by Satterthwaite Associates (1987)
simulates a single two-year storm. In order to serve as a flow and load
generator to the time-varying water quality model, the stormwater model must
be amended to accommodate continuous rainfall events for various summer
seasons. That is, the model must be able to calculate temporal flows and
coliform discharges based on actual rainfall records.
The runoff calculated by the time-varying stormwater model will be
compared to flow measurements collected by the U.S. Geological Survey (USGS)
at the mouths of Beaver Swamp Brook and the Mamaroneck River. The transport
of the water quality model will be calibrated using available salinity data
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collected by Hestchester County. Flows generated by the runoff model for a
summer season (wet and dry) will be routed through the water quality model.
Dispersion coefficients will be adjusted to reproduce average salinity data at
the various summer sampling stations. However, salinity data are available
only at the surface with two or three collections per month. Therefore, data
limitations may permit only a cursory calibration of transport parameters.
The water quality assessment will be described in a separate report
which will be submitted later in the program, about spring 1990.
1.3 SUB-BASIN MONITORING PROGRAM
Westchester County has implemented a monitoring program of wet weather
flows in two small sub-watersheds within the Mamaroneck Harbor Drainage Basin.
Measurement of coliform levels in the stormwater runoff from each of these
sub-watersheds will be conducted before and after the implementation of non-
structural BMPs to evaluate effectiveness of BMPs. The two sub-watersheds are
located in the Village of Mamaroneck, all in residential areas, and discharge
to the Mamaroneck River. The two sub-watersheds are:
Hal stead Avenue East Outfall System
North Barry Avenue System.
The Halstead System is the largest of the three, consisting of about six
blocks including branches. It has no dry weather flow. The North Barry
System drains about four blocks and discharges further upstream, and it also
has no dry weather flow. The stormwater sewer systems are shown on Figures 1
and 2.
The monitoring program was started in July, 1989, and will continue
after the implementation of BMPs.
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ft*0'
,0*
KEY
OMANHOLE
D CATCH 9ASIN
30UTLET
-Mi
FIGURE 1.
HALSTEAO AVENUE EAST
OUTFALL/STORM SEWER
-------
KEY
O MANHOLE
a CATCH BASIN
3 OUTLET
FIGURE 2.
NORTH BARRY AVENUE
OUTFALL/STORM SEWER
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2.0 REVIEW OF BEST MANAGEMENT PRACTICES
2.1 EVALUATION OF BMPs IN MAMARONECK HARBOR
Mamaroneck Harbor is a natural constricted embayment that is surrounded
by established urban development. It is valued as a recreational resource and
it supports a number of beaches used for swimming during the summer. However,
the harbor is subject to periodic closures because of elevated bacterial
levels that are associated with the influx of stormwater. Recent efforts have
been made to understand and address contamination sources with the goal of
eliminating these beach closures.
In the past, the primary focus on stormwater management in the Mamaroneck
Watershed has been on flood control. Practices have been designed to mitigate
the effects of peak flood flow by piping runoff into directed watercourses as
quickly as possible. Existing regulations on the local, county, and state
levels encouraged this traditional approach to drainage.
More recently, the quality of the runoff has become an issue of concern.
To address water quality, it has been recognized that a management system that
treats the watershed as a whole must be developed. Toward that end, a number
of Best Management Practices (BMPs) have been examined as having the potential
to upgrade the quality of the stormwater runoff entering the harbor. These
BMPs include structural provisions such as detention ponds, infiltration
devices, and vegetative measures, and non-structural (or housekeeping)
ordinances such as catch basin cleaning, street sweeping, and litter control.
Many of these BMPs have been implemented by some of the communities in the
Mamaroneck Watershed. However, these BMPs could be upgraded and implemented
region-wide to address the objectives of significantly improving the quality
of stormwater runoff and potentially eliminating the necessity of closing the
beaches in Mamaroneck Harbor.
2.2 FECAL COLIFORM REDUCTIONS BY STRUCTURAL BMP
The implementation of structural BMPs was examined in the draft
evaluation of techniques to control pollution input to Mamaroneck Harbor
-------
(Myers, 1989). Many of these structures directly affect the number of total
coliforms, fecal coliforms, and fecal streptococci found in downstream runoff.
Each of these structural BMPs is examined below.
2.2.1 Dry Detention Basins
A dry detention basin is a storage facility designed to slow or dampen
storm flows entering a sewer system by temporarily holding the water. A dry
basin does not contain a permanent pool of water but contains water only
during storms. Dry detention basins typically are not effective in
controlling pollutant loadings.
Dry ponds exhibited little or no pollutant removal capability in a test
of urban stormwater BMPs in metropolitan Washington, DC (Schueler et al.,
1985). However, parking-area detention ponding through undersized drain
openings was shown to be effective in controlling coliforms at Myrtle Beach,
SC (Bludau and Schwartz, 1981).
A study in Arizona showed that flooding a basin and then allowing it to
dry for three days was very effective in removing total coliforms. Total
coliform levels decreased to 2/100 ml at a distance of 30 feet from the point
of application (Goff and Goldman, 1981).
2.2.2 Wet Detention Basins
Wet detention basins are designed to maintain a permanent pool of water,
which reduces the scouring action of incoming stormflows and the associated
resuspension of sediments. A Nationwide Urban Runoff Program (NURP) project
resulted in a 94% reduction in total coliforms, 91% reduction in fecal
coliforms, and 95% reduction in fecal streptococci at the Unqua basin site in
Long Island (Long Island Regional Planning Board, 1982). It was noted that
concentrations of fecal coliforms and fecal streptococci are highly correlated
with physical factors and that settling of stormwater suspended solids is
closely associated with bacterial reductions in stormwater (Davis, 1979).
However, the storage and eventual treatment of runoff was found to have the
highest suitability as a control measure for bacteria (Pitt, 1979).
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2.2.3 Extended Detention Dry Basins
Extended detention dry basins are designed to slow the storm flow a
significantly greater amount than dry detention basins. This allows for
enhanced settling and greater biological uptake of pollutants (Myers, 1989).
Tests conducted on urban runoff to measure the removal of different
pollutants by settlement have indicated a significant trend in the reduction
of fecal coliforms. A 32-hour settlement period resulted in reductions
exceeding an order of magnitude (Whipple and Hunter, 1981).
2.2.4 Infiltration Basins and Dry Wells
Infiltration basins are stormwater control structures that allow runoff
to seep into the soil around them. Dry wells are usually precast concrete
chambers with perforated sides designed so that runoff infiltrates directly
into the soil. Infiltration wells, ditches, and drains were shown to be
effective in controlling coliform bacteria at Myrtle Beach, SC (Bludau and
Schwartz, 1981). Pathogenic bacteria and coliforms were found to be
completely removed by percolation through 5 feet of soil under controlled slow
infiltration design conditions. Survival times were typically a maximum of
three months for organisms retained on soil particles (Goff and Goldman,
1981). The concentrations of most pollutants in urban runoff percolating
through 3/4 meter of Guam soil and limestone were substantially reduced.
Total and fecal coliforms showed a 70% or greater reduction (Zolan et al.,
1978).
2.2.5 Permeable Pavements
Permeable paving is usually brick or gravel, which can be used in
driveways, walkways, and low-use parking areas. Porous pavements were one
potential solution to water quality impairment induced by wet weather (Murphy
et al., 1977). Rains were much less effective in removing material from oil
and crushed rocks streets than from asphalt streets (Pitt, 1979). Porous
surface materials for light-traffic parking areas, walkways, and deck areas
8
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were also shown to be effective in controlling coliform bacteria at Myrtle
Beach, SC (Bludau and Schwartz, 1981).
2.2.6 Vegetative Measures
Vegetative measures include seeding, sodding, and mulching of uncovered
ground to prevent erosion of soil and contaminants associated with the soil.
Grass swales exhibited little or no pollutant removal capability in a test of
urban stormwater BMPs in metropolitan Washington, DC (Schueler et al., 1985).
However, grass filter strips were recommended as a BMP for improving runoff
quality near small feedlots (Sweeten and Melvin, 1985).
The maintenance of grass cover downslope from sites where animals
congregate and along stream banks is a recommended BMP for unconfined cattle
production (U.S. EPA, 1984). Other recommended measures include maintenance
of good ground cover to decrease runoff volume and rate, and restriction of
animal access to critical areas. Vegetation strips for absorption, detention,
and runoff filtering, and landscape planting to maximize transpiration were
shown to be effective in controlling coliforms at Myrtle Beach, SC (Bludau and
Schwartz, 1981).
2.2.7 Storage in the Receiving Hater
Storage of stormwater flow is considered a viable BMP because of the high
volume and variability of storm runoff. One recently developed storage
alternative is the in-receiving-water flow balance method. In this method, a
series of cells formed by plastic curtains are suspended from wooden pontoons
floating at the surface of the receiving water. The facility is located at a
stormwater overflow and receives the flow during a storm. The receiving water
in each cell is successively displaced until the overflow stops. After
cessation of the overflow, the stormwater can be pumped from the first cell to
a treatment plant. The receiving water enters the series of cells from the
last compartment and pushes the stormwater toward the first cell (Field,
1988).
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The storage method is low cost, about 5-15 percent of conventional
concrete tank costs. The facility was tested at three sites in Sweden and
performed well (Field, 1988). A demonstration project has been designed and
constructed at the Fresh Creek Basin in New York City. However, data on the
effectiveness of the system are not yet available (Moffa, P.E., Blasland,
Bouck, and Lee, personal communicaton, 1989). Another flow balance method was
proposed for Guion Creek in Mamaroneck Harbor. In this system, the stormwater
was to be" settled and then disinfected with chlorine before discharge to the
harbor (Moffa, P.E. Moffa and Associates, personal communication, 1988). The
facility was sized in only a preliminary manner and construction costs were
estimated at about $1.5 million (Moffa, P.E., Blasland, Bouck, and Lee,
personal communication, 1989). Many questions as to the impact of discharging
chlorinated effluent to the harbor, aesthetics (e.g., floatable debris), and
liability have not been addressed for this system.
2.3 FECAL COLIFORM REDUCTIONS BY HOUSEKEEPING BMP
The implementation of non-structural, housekeeping BMPs was also
examined in the draft evaluation of Mamaroneck Harbor (Myers, 1989). Some of
these techniques are directly applicable in reducing coliform counts, while
others have little or no bearing on bacterial contamination.
2.3.1 Catch Basin Cleaning
A catch basin is a storage facility or well that allows stormwater to
flow to a sewer system and has a sump at its base designed to retain grit and
sediment. Historically, the role of catch basins was to reduce the clogging
of sewers by trapping coarse detritus (Lager et al., 1977).
Sediments appeared to act as reservoirs of bacteria in a study of
watersheds above two Puget Sound bays, and disturbances of these sediments
produced large increases in downstream counts (Saunders, 1985). Thus, catch
basins can be a source of bacteria if not routinely cleaned. Cleaning can be
by hand, bucket, eductor, or vacuum (Lager et al., 1977).
10
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2.3.2 Lawn-Care-Related Controls
Pesticide and fertilizer application in residential areas has increased
over the past two decades (Myers, 1989). This is one of the most overlooked
measures for reducing pollution from stormwater runoff (Lager et al., 1977).
Leaching nutrients from lawns and green-belt areas is of concern in the
Mamaroneck Harbor Watershed because of the potential that nutrient enrichment
may contribute to coliform replication in the harbor (Satterthwaite
Associates, 1987). Concentrations of total coliforms, fecal coliforms, and
total aerobic bacteria were also shown to correlate with winter low
temperatures and nitrate-nitrogen concentration. A negative correlation with
phosphate was found (Reddy et al., 1986).
2.3.3 Street Cleaning
Most communities use street cleaning to remove accumulated dirt and
litter, usually for aesthetic reasons (Lager et al., 1977). Studies have
shown that abatement of stormwater runoff pollution has been accomplished
through source control, including improved street sanitation (Ford et al.,
1979). Dry vacuum sampling is capable of removing all of the particulates
(>99%) from the street surface. Some sort of wetting/flushing must be used to
effectively remove fecal coliform and fecal streptococcal bacteria from the
road surface with a mechanical sweeper (Pitt, 1979). The use of combined
broom and vacuum cleaning of parking areas and streets was shown to be
effective in controlling coliform bacteria at Myrtle Beach, SC (Bludau and
Schwartz, 1981).
Public awareness of street cleaning programs is very important for
effective implementation. When automobiles are left parked in streets during
street cleaning, street cleaning is impaired. For cleaning of 70-80 percent
of the curb area, parking regulations must be complied with along at least 85
percent of the curb length (Lager et al., 1977).
11
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2.3.4 Litter Control
The control of litter was shown to be effective in reducing runoff
loadings on a small spatial scale although, on a broad scale, the
effectiveness could not be documented (Myers, 1989). Pitt (1979) considered
seasonal leaf removal and litter control as low in suitability for control of
bacteria.
2.3.5 Pet Haste/Animal Haste Ordinances
A significant source of coliform loading occurs in stormwater runoff from
neighborhoods having large domestic dog populations (Heufelder, 1989; Long
Island Regional Planning Board, 1982). The control of dog litter ranks medium
to high in suitability as a control measure for bacteria (Pitt, 1979). This
would indicate that animal waste control may be a promising BMP for reducing
coliform levels. However, no correlation was developed between coliform
levels and bird counts in a study of two small bays in Puget Sound (Saunders,
1985). Restricting animal access to critical areas was also recommended as a
BMP for nonpoint source pollution control for unconfined cattle (U.S. EPA,
1984).
Most of the communities in the Mamaroneck Harbor Watershed have modern
pet waste control ordinances. However, in some areas with dog cleanup laws,
enforcement has proven to be difficult. The education of the public through
an outreach program may increase the compliance with these ordinances and
reduce coliform loadings from these sources.
3.0 RECOMMENDATIONS
The review of the BMPs used in the Mamaroneck Harbor Watershed and their
bacterial removal potential indicates that the following may be suitable for a
demonstration project:
Catch Basin Cleaning
Street Cleaning
Pet Waste Ordinances.
12
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The feasibility of implementating of these BMPs needs to be discussed with the
Village of Mamaroneck. If the Village considers these as feasible for the
demonstration project, a public outreach program should be started.
4.0 LITERATURE CITED
Bludau, O.W. and L. Schwartz. 1981. Urban runoff - Its impact and control at
Myrtle Beach, South Carolina. In: D.J. Wood (ed.), 1981 Proceedings,
International Symposium on Urban Hydrology, Hydraulics and Sediment
Control, University of Kentucky, Lexington, KY. pp. 207-210.
Davis, E.M. 1979. Maximum utilization of water resources in a planned
communityBacterial characteristics of stormwaters in developing rural
areas. U.S. EPA Report No. EPA-600/2-79-050f.
Field, R. 1988. Storm and combined sewer overflow: An overview of EPA's
research program. U.S. EPA Report No. EPA-600/8-89-054. EPA Storm and
Combined Sewer Program, Edison, NJ.
Ford, W.C. et al. 1979. Treating peak discharges of stormwater runoff.
Water & Sewage Works 126(1):48.
Goff, J.D. and F.E. Goldman. 1981. Urban recreational lakes serving as storm
water retention basins and effluent disposal. In: D.J. Wood (ed.), 1981
Proceedings, International Symposium on Urban HyUrology, Hydraulics and
Sediment Control, University of Kentucky, Lexington, KY. pp. 315-321.
Heufelder, G. et al. 1989. Potential effects of nutrient loading on
bacterial contamination levels in enclosed estuaries. Paper presented at
the Buzzards Bay Symposium, Woods Hole, MA, 7-8 Feb 1989.
Lager, J.A. et al. 1977. Urban Stormwater Management and Technology: Update
and Users' Guide. U.S. EPA Report No. EPA-600/8-77-014. Municipal
Environmental Research Laboratory, Cincinnati, OH.
Long Island Regional Planning Board. 1982. The Long Island Segment of the
Nationwide Urban Runoff Program. Hauppauge, NY.
Murphy, C.B., Jr., et al. 1977. Best Management Practice for urban storm and
combined sewer pollution control. Water & Sewer Works 124(11):81.
Myers, J.C. 1989. Evaluation of Best Management Practices Applied to Control
of Stormwater-Borne Pollution in Mamaroneck Harbor, NY. Prepared for the
U.S. EPA, Office of Marine and Estuarine Protection under contract to
Battelle.
Pitt, R. 1979. Demonstration of non-point pollution abatement through
improved street cleaning practices. U.S. EPA Report No. EPA-600/2-79-
161. Cincinnati, OH.
13
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Reddy, G.B., E. Ford, and D. Aldridge. 1986. Seasonal changes in bacterial
numbers and plant nutrients in point and non-point source ponds. Envir.
Poll. Series A: Ecol. and Biol. 40(4):359-367.
Satterthwaite Associates, Inc. 1987. Mamaroneck Harbor Pollution Study.
Prepared for the County of Westchester and the Village of Mamaroneck, NY.
Saunders, B. 1985. Nonpoint source pollution control in small bays of Puget
Sound. In: Perspectives on Nonpoint Source Pollution, Kansas City,
Missouri, pp. 177-179. EPA Report No. EPA 440/5-85-001. Office of
Water Regulations and Standards, Washington, DC.
Schueler, T., R. Magill, M.P. Sullivan, and C. Wiegand. 1985. Comparative
pollutant removal capability, economics, and physical suitability of
urban Best Management Practices in the Washington DC metropolitan area.
Nonpoint Pollution Abatement Symposium, Milwaukee, WI.
Sweeten, J.M. and S.W. Melvin. 1985. Controlling water pollution from
nonpoint source livestock operations, _In: Perspectives on Nonpoint
Source Pollution, Kansas City, Missouri, pp. 215-217. U.S. EPA Report
No. EPA 440/5-85-001. Office of Water Regulations and Standards,
Washington, DC.
U.S. EPA. 1984. Report to Congress: Nonpoint source pollution in the U.S.
U.S. Environmental Protection Agency, Office of Water Program Operations,
Washington, DC.
Whipple, W. and J.V. Hunter. 1981. Settleability of urban runoff pollution.
J. Water Pollut. Control Fed. 53(12):1726-1731.
Zolan, W.J., R.N. Clayshulte, and S.J. Winter. 1978. Urban runoff pollutant
adsorption and filtering by selected northern Guam soils and limestone.
Report to the U.S. Dept. of the Interior under Contract No. 14-34-0001-
6054-70231-7024. 48 pp.
14
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Appendix C
MAMARONECK HARBOR PROJECT
DATA EVALUATION AND MODEL ANALYSIS
-------
FINAL REPORT
MAMARONECK HARBOR PROJECT
DATA EVALUATION AND MODEL ANALYSIS
EPA Contract No. 68-C8-0105
Work Assignment 2-30
to
ENVIRONMENTAL PROTECTION AGENCY
Office of Wetlands, Oceans, and Watersheds
Washington, DC
31 July 1991
Prepared by
HydroQual, Inc.
1 Lethbridge Plaza
Mabwah, New Jersey 07430
Prepared for
Battelle Ocean Sciences
397 Washington Street
Duxbury, Massachusetts 02332
(617) 9344)571
-------
CONTENTS
List of Tables
List of Figures
SUMMARY AND CONCLUSIONS ........................................ vii
Evaluation of Existing Data .......................................... ix
Evaluation/Revision of Existing Storm-Runoff Model
and Assessment of Storm-Runoff Quality ............................. x
Development of a Time- Variable Water-Quality Model of
Mamaroneck Harbor ............................................ »
Assess Required Level of Abatement for
Runoff and Nonpoint-Source Pollutants .............................. xvi
1.0 INTRODUCTION
Westchester County Protocol for Beach Closing ........................... M
2.0 DATA ANALYSES
2.1 Analysis of Inland-Stream Water-Quality Data ......................... 2-1
2.2 Analysis of Stream Checkpoint Data ................................ 2-7
2.3 Analysis of Beach Data .......................................... 2-15
3.0 DEVELOPMENT OF STORM-RUNOFF MODEL
4.0 ANALYSIS OF STORM-WATER CONCENTRATIONS
5.0 DEVELOPMENT OF MATHEMATICAL WATER-QUALITY MODEL
5.1 Calibration of Model Transport .................................... 5-1
5.2 Coliform Calibration ............................................ 5-5
6.0 ASSESSMENT OF LOAD REDUCTION
6.1 Assessment of Source Distribution .................................. 6-1
6.2 Estimated Load-Reduction Requirements ............................. 6-3
7.0 REFERENCES
111
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LIST OF TABLES
S-l Beach Data Analysis
(a) Total Coliform Summaiy 1983-1989 x
(b) Fecal Coliform Summaiy 1983-1989 x
S-2 Calculated Tributary Coliform Source Distribution ri
S-3 Calculated Total Source Distribution for Total and Fecal Coliform Bacteria xvi
S-4 Estimated Load Reductions Required To Meet Water-Quality Standards xvi
S-S Reductions of Total and Fecal Coliform Required at Tributaries,
Assuming Local Source Control xvii
2-1 Mamaroneck Harbor 1985 Inland-Stream Data -
Probability Distribution Summary 2-6
2-2 Mamaroneck Harbor 1985 Inland-Stream Data - Geometric Means 2-7
2-3 Characteristics of Checkpoint (1) Coliform Distributions 2-8
2-4 Calculated Fecal Coliform Source Distribution.
May 15 through September 15,1983 - 1989 2-15
2-5 Beach Data Analysis
(a) Yearly Median Total Coliform Concentrations 2-23
(b) Yearly Median Fecal Coliform Concentrations 2-23
(c) Total Coliform Summary. 1983 - 1989 2-24
(d) Fecal Coliform Summary. 1983 - 1989 2-24
2-6 Percent Fecal Coliform Samples Exceeding 1000 MPN/100 mL 2-25
4-1 Estimated Stormwater Concentrations. 1983 - 1989 4-1
4-2 Observed Stormwater Coliform Concentrations in Other Studies 4-2
6-1 Comparison of Calculated and Observed Geometric-Mean
Concentrations of Fecal Coliform Bacteria 6-1
6-2 Observed MLE and Calculated Mean Fecal Coliform
Concentrations and Source Distribution 6-2
6-3 Calculated Tributary Coliform Source Distribution 6-3
6-4 Calculated Total Source Distribution for Total and Fecal Coliform Bacteria 6-4
6-5 Comparison of Long-Term Total and Fecal Coliform Concentrations
against Standards 6-4
6-6 Estimated Load Reductions Required To Meet Water-Quality Standards 6-5
6-7 Reductions of Total and Fecal Coliform Required at Tributaries,
Assuming Local Source Control 6-5
iv
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LIST OF FIGURES
S-l Observed and Calculated Cumulative Flow
(a) Mamaroneck River xii
(b) Beaver Swamp Brook »v
S-2 Observed and Calculated Salinity and Fecal Coliform Distributions
at Harbor Water-Quality Stations
(a) Salinity Distributions xix
(b) Fecal Coliform Distributions xri
1-1 Mamaroneck Harbor Study Area Facing page 1-1
2-1 Inland-Stream Sample Sites 2-2
2-2 Inland-Stream Probability Distributions. 1985
(a) Mamaroneck River 2-3
(b) Beaver Swamp Brook 2-4
(c) Sheldrake River 2-5
2-3 Probability Density Distribution Analysis of Coliform Concentrations
(a) Mamaroneck River Checkpoint Data 2-10
(b) Beaver Swamp Brook Checkpoint Data 2-11
2-4 Calculated and Measured Coliform Loading Distributions
(a) Mamaroneck River 2-12
(b) Beaver Swamp Brook 2-13
2-5 Mamaroneck Harbor and Beach Sampling Locations 2-14
2-6 Beach Coliform Probability Density Distributions. 1983 - 1989
(a) Harbor Island Beach 2-16
(b) Shore Acres Point 2-17
(c) Mamaronsck Beach Cabana and Yacht Club 2-18
(d) Beach Point Club 2-19
(e) Orienta Beach 2-20
(f) Westchester Summer Day School 2-21
2-7 Yearly Median Total and Fecal Coliform Concentrations
Dry-Weather Conditions 2-26
3-1 Basis of Storm-Runoff Model 3-2
3-2 Westchester County Airport Rainfall Records 3-3
3-3 Observed and Calculated Cumulative Flow
(a) Mamaroneck River 3-5
(b) Beaver Swamp Brook 3-7
5-1 Three-Dimensional Water-Quality Model Segmentation 5-2
5-2 Mamaroneck Harbor Model Segments 5-3
5-3 Vertical Salinity Profiles 5-4
5-4 Comparison of Observed and Calculated Salinity Concentrations 5-7
-------
LIST OF FIGURES (continued)
5-5 Comparison of Observed and Calculated Salinity Distributions 5-9
5-6 Comparison of Observed and Calculated Fecal Coliform Concentrations
(a) Harbor Survey Stations 5-11
(b) Beach Samples 5-13
5-7 Comparison of Observed and Calculated Total Coliform Concentrations
(a) Harbor Survey Stations 5-15
(b) Beach Samples 5-17
5-8 Comparison of Observed and Calculated Fecal Coliform Distributions
(a) Harbor Survey Stations 5-19
(b) Beach Samples 5-21
vi
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SUMMARY AND CONCLUSIONS
A comprehensive data-evaluation and modeling analysis was performed to investigate the impact
of storm-runoff flows to Mamaroneck Harbor. The primary objectives of this study have been to
assess (1) the influence of urban storm runoff and nonpoint-source impact on the quality of bath-
ing water and (2) the required level of abatement for compliance with New York State bathing-
water coliform standards.
These objectives are designed to evaluate existing bacterial conditions, quantify the sources of
coliforms at bathing beaches, and assess abatement requirements. The evaluations described in
this report are directed toward determining compliance with New York State bathing standards
as defined by numerical limits on total and on fecal coliform concentrations. The Westchester
County Department of Health assesses the sanitary quality of bathing water at Mamaroneck Har-
bor beaches in accordance with policy that is based primarily on total coliform data, in ac-
cordance with the New York State and Westchester County Sanitary Codes.
The tasks completed in this study include
1. Evaluation of existing data
2. Evaluation/revision of the existing storm runoff model and assessment of storm-runoff
quality
3. Development of a time-variable water-quality model of Mamaroneck Harbor
4. Assessment of the required level of abatement for runoff and for nonpoint-source pollut-
ants.
Based on the analyses completed during these tasks, the following conclusions are presented.
1. Elevated coliform concentrations are present throughout the Mamaroneck Harbor and
Beaver Swamp Brook watersheds. These drainage basins account for nearly all fresh-
water flow to Mamaroneck Harbor. Coliform levels during wet-weather conditions are
significantly higher than during dry-weather conditions. Coliform levels during both wet-
and dry-weather conditions are considerably higher than New York State coliform stan-
dards for bathing.
2. A composite analysis of all beach data collected between 1983 and 1989 shows violations
of total and fecal coliform standards at three of the six beaches in the vicinity of Mama-
roneck Harbor. The three northern beaches - Harbor Island (also known as S.E. Johns-
ton), Shore Acres, and Mamaroneck Beach Cabana and Yacht Club (hereafter: Mamaro-
neck BC&YC) - show exceedance of coliform standards. The three southern beaches
- Beach Point, Orienta Beach, and Westchester Summer Day School (hereafter: West-
Chester SDS) - are in compliance with coliform standards.
3. An analysis of the beach fecal coliform data indicates that fecal coliform levels greater
than 1000 MPN/100 mL have been reported in 30% to 50% of the samples collected at
the three northernmost beaches. Although this is not a violation of bathing standards,
New York State Sanitary Code suggests consideration of beach closure and requires
additional sampling when fecal coliform levels exceed 1000 MPN/100 mL.
4. An analysis of data at the beaches, excluding wet-weather samples, indicates violations of
fecal coliform bathing standards at the northern beaches even during dry-weather condi-
tions. Therefore, background tributary loadings and/or local sources of bacteria can
cause noncompliance with coliform standards.
Vll
-------
5. The analysis of tributary checkpoint data distinguishes the relative contributions of coli-
form bacteria from background and storm-related sources within the tributaries. About
89% of the total coliform loads is estimated from stornwater runoff and 11% from
background sources. Similarly, about 74% of the fecal coliform loads is estimated from
stormwater runoff and 26% from background sources. Of the total from both drainage
basins, 67% of the total coliform and 86% of the fecal coliform are estimated to origi-
nate from the Mamaroneck River basin.
6. Estimated storm runoff concentrations of coliform bacteria are reasonable when com-
pared to concentrations measured in other areas. The results imply that on an area-
wide basis the influx of other sources of bacteria, such as sanitary waste, cannot be dis-
tinguished in this analysis. However, the possibility of some level of sanitary inflow to
the Harbor watershed is still feasible.
7. Localized sources of bacteria vary from beach to beach and may vary from year to year.
Based on the 1989 model analysis and data evaluation, localized sources have relatively
significant impact at two beaches and lesser impact at two other beaches.
8. The model and data analyses indicate that at Harbor Island and Shore Acres an ap-
proximate 60% reduction of total coliforms would be required to meet standards. At
Mamaroneck BC&YC, a minor reduction of total coliforms would be required. With
regard to fecal coliforms, reductions of about 50% to 75% would be required to meet
standards at the three northern beaches (Harbor Island, Shore Acres, and Mamaroneck
BC&YC).
9. Assuming localized source control, Mamaroneck BC&YC may comply with coliform
standards. Harbor Island and Shore Acres would still require substantial reductions in
coliforms from the tributaries (50% to 75%) to comply with standards.
10. To comply with fecal coliform standards at Harbor Island during dry-weather conditions
would require a 33% reduction of background tributary sources of fecal coliforms. This
reduction is in addition to localized source control. At Shore Acres, the required level of
reduction of background tributary sources is marginal.
The following Sections summarize the key results of the tasks outlined above.
Vlll
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EVALUATION OF EXISTING DATA
Three types of data set are evaluated extensively in this study. These include inland-stream data,
stream checkpoint data, and beach data. The inland-stream data and the beach data are evalu-
ated to assess existing conditions and to determine if differences are evident between wet- and
dry-weather samples. Beach data are evaluated also for comparison with existing water-quality
standards.
Overall, the inland-stream data analyses reveal elevated coliform concentrations during both wet
and dry sampling periods, but they also indicate wet-weather concentrations as being the more
severe. During wet- and dry-weather conditions, the total coliform concentrations in the tribu-
taries are > 24,000 and about 8000 MPN/100 mL, respectively. The median fecal coliform con-
centrations in the tributary streams are about 3500 and 1500 MPN/100 mL, respectively. For
comparison purposes, these are well above the New York State geometric-mean bathing stan-
dard of 2400 MPN/100 mL for total coliform bacteria and 200 MPN/100 mL for fecal coliform
bacteria.
The key results of the analysis of the beach data are summarized in Tables S-l(a) and (b). The
results include all beach data collected between 1983 and 1989. Coliform concentrations exceed
bathing standards for total and for fecal coliforms at the three northern beaches that comprise
Harbor Island, Shore Acres, and Mamaroneck BC&YC. The other three area beaches are in
compliance with coliform standards. The analysis also demonstrates that fecal coliform stan-
dards are exceeded during periods of dry weather. Therefore, the dry-weather analysis of fecal
coliform bacteria implies that background and/or local sources of bacteria are significant and can
cause fecal coliform standards to be exceeded.
Stream checkpoint data are the data that were collected near the mouths of the major tribu-
taries: the Mamaroneck River and Beaver Swamp Brook. Nearly all the runoff waters in the
study area are transported to the harbor by the tributaries. Therefore, a statistical methodology
was developed, using these data to compute coliform runoff and background loadings to the
harbor. The analysis uses discreet coliform measurements to statistically characterize the quality
of inflow to the harbor and provides a basis for computing daily loading rates.
The checkpoint data analysis distinguishes the contributions of background coliform levels and
stormwater runoff. The relative contributions of fecal coliform bacteria from the tributary drain-
age basins are summarized in Table S-2. In summary, about 89% of the total coliform loads
from the tributary basins is estimated to be from runoff waters, with the balance coming from
background sources. Of the total from both basins, 67% is estimated to come from the Mama-
roneck River basin. For fecal coliforms, about 74% is estimated to be from runoff waters, with
86% coming from the Mamaroneck River basin.
IX
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Table S-l. Beach Data Analysis.
(a) Total Colifonn Summary. 1983 - 1989.
Concentration Percentiles (MPN/100 mL)
All Data Dry-Weather Data
Harbor Island
Shore Acres
Mamaroneck BC&YC
Beach Point
Orienta Beach
Westchester SDS
Geometric
Mean8
2,700
1,700
960
250
230
230
80%b
13,540
11,250
5,500
1,100
1,100
950
Geometric
Mean8
1,280
790
470
140
150
230
80%"
4,670
3,080
1,850
540
640
870
"Standard: 2400 MPN/100 mL.
Standard: 5000 MPN/100 mL.
(b) Fecal Colifonn Summary. 1983 - 1989.
Concentration Percentiles (MPN/100 mL)
All Data Dry-Weather Data
Geometric Geometric
Mean3 Mean"
Harbor Island
Shore Acres
Mamaroneck BC&YC
Beach Point
Orienta Beach
Westchester SDS
850
430
500
120
120
110
460
220
290
80
90
110
"Standard: 200 MPN/100 mL.
EVALUATION/REVISION OF EXISTING STORM-RUNOFF MODEL
AND ASSESSMENT OF STORM-RUNOFF QUALITY
The storm-runoff model, originally developed by Satterthwaite Associates, was revised to sim-
ulate temporal runoff volumes based on daily rainfall records. The model is calibrated by com-
paring calculated discharges against the flow records of the Mamaroneck River and Beaver
Swamp Brook. Comparisons made between calculated and observed cumulative runoff volumes
are shown for the Mamaroneck River and Beaver Swamp Brook in Figures S-l(a) and (b), re-
spectively. The comparisons show good agreement for both the Mamaroneck River and Beaver
Swamp Brook watersheds.
-------
Table S-2. Calculated Tributary Colifonn Source Distribution.
Total Coliform Fecal Colifonn
Mamaroneck River
Storm runoff 58 64
Background 9 22
Total 67 86
Beaver Swamp Brook
Storm runoff 31 10
Background 2 4
Total 33 14
Analysis of the checkpoint data and results from the storm-runoff model are combined to es-
timate average coliform concentrations in runoff waters. Dividing estimated runoff loading rates
by runoff flow gives an average coliform runoff concentration. The analysis estimates of total
and fecal coliform concentrations in the storm-runoff waters are 180,000 and 16,000 MPN/100
mL, respectively, for the Mamaroneck drainage basin and 450,000 and 11,000 MPN/100 mL,
respectively, for the Beaver Swamp drainage basin. The average concentrations estimated in this
analysis are reasonable when compared to storm-water concentrations measured in other areas.
The results imply that there probably is no other significant source of bacteria in the drainage
basins, such as sanitary inflow. There may be sanitary inflow in the drainage basins but, based on
this areawide analysis, sanitary inflow does not appear to have a very significant impact. The
comparison suggests that if there were any sanitary inflow into the drainage basin such inflow
appeared to have little significant impact and the coliform concentrations were primarily a func-
tion of storm runoff.
DEVELOPMENT OF A TIME-VARIABLE
WATER-QUALITY MODEL OF MAMARONECK HARBOR
A mathematical water-quality model of Mamaroneck Harbor has been developed to evaluate the
cause/effect relationships between coliform sources and water quality in the harbor waters and at
the beaches. The basic modeling framework uses a three-dimensional time-variable model devel-
oped by Hydroscience in 1978. In this study, the model is recalibrated in the nearshore areas to
reproduce the 1989 salinity and coliform profiles. Comparisons of observed and calculated salini-
ty and fecal coliform distributions at harbor water-quality stations are shown in Figures S-2(a)
and (b). The comparisons show good agreement between the calculated and observed data.
XI
-------
-^
u
0)
o
i -
r- ~T~ r~
ofcse-v'ecJ runcff
calculated runoff
DAYS - 19B3
I
o
c.
DAYS -
-k
U
01
I
DAYS - 19B5
Figure S-l. Observed and Calculated Cumulative Row.
(a) Mamaroneck River.
301
-------
U
c
c
o
L
(0
1C
cCse~ve3 runoff
calculated runoff
DAYS - 19B6
cr mm
r
[
-
u
0)
o
L.
DAYS - 1967
1
o
re
10
DAYS - 39BB
Figure S-l. Observed and Calculated Cumulative Flow, (continued)
(a) Mamaroneck River, (continued)
xiii
-------
6)
>
ID
01
m
-r- r- r-
observed runcff
calculates runoff
DAYS - 19B3
ITS
L.
V
n
v
c
DAYS -
1C
in
*
DAYS - 19B5
Figure S-l. Observed and Calculated Cumulative Row. (continued)
(b) Beaver Swamp Brook.
xiv
-------
IBC
in
a
(0
i r- r-
cfcserved rjncff
calculates runoff
DAYS - 1986
T T
DAYS - 19B7
i
I
ip
DAYS - 19BB
Figure S-l. Observed and Calculated Cumulative Flow, (continued)
(b) Beaver Swamp Brook, (continued)
xv
-------
Table S-3. Calculated Total Source Distribution for Total and Fecal Coliform Bacteria
SOURCE DISTRIBUTION (%)
Total Coliform Fecal Coliform
Local* Mamaroneck Beaver Local* Mamaroneck Beaver
River Basin Swamp Brk. River Basin Swamp Brk.
Basin Basin
Harbor Island 12
Shore Acres 0
Mamaroneck BC&YC 58
Beach Point 14
Orienta Beach 27
Westchester SDS 0
59
67
28
58
49
67
29
33
14
28
24
33
12
0
58
14
27
0
75
86
36
74
63
86
13
14
6
12
10
14
Approximate from 1989 analyses. Percentages may vary due to year-to-year fluctuations, moni-
toring error, and model accuracy.
ASSESS REQUIRED LEVEL OF ABATEMENT
FOR RUNOFF AND NONPOINT-SOURCE POLLUTANTS
The water-quality data evaluations and modeling analyses are used as the basis for estimating the
load reductions necessary to comply with New York State bathing water-quality standards. The
analysis quantiGes the overall level of control required to meet total and fecal coliform standards
at six beach locations in the harbor. The analysis also quantifies the source distribution of coli-
forms at each of the beaches.
Table S-4. Estimated Load Reductions Required To Meet Water-Quality Standards
PERCENT REDUCTIONS
Total Coliform Fecal Coliform
Geometric Mean C Geometric Mean
Harbor Island
Shore Acres
Mamaroneck BC&YC
Beach Point
Orienta Point
Westchester SDS
11
0
0
0
0
0
63
56
9
0
0
0
76
53
60
0
0
0
XVI
-------
Table S-S. Reductions of Total and Fecal Coliform Required at Tributaries,
Assuming Local Source Control
PERCENT REDUCTIONS
Total Colifonn Fecal Colifonn
Geometric Mean Cg, Geometric Mean
Harbor Island
Shore Acres
Mamaroneck BC&YC
Beach Point
Orienta Point
Westchester SDS
0
0
0
0
0
0
58
51
0
0
0
0
73
46
0
0
0
0
The calculated source distributions for total and for fecal coliform bacteria are given in Table
S-3. The table summarizes the estimated contributions from localized sources and the two river
basins. The assessment of local contributions is based on 1989 model and data analysis. The
analysis indicates that most of the coliform bacteria originate from the Mamaroneck River basin,
with the exception of Mamaroneck BC&YC. At Mamaroneck BC&YC, over 50% of the coli-
forms is estimated from local sources.
Estimated load-reduction requirements are based on the beach data analyses shown in Tables
S-l(a) and (b). The reductions necessary to meet water-quality standards at each beach are sum-
marized in Table S-4. At Harbor Island and Shore Acres, an approximate 60% reduction would
be required to meet total coliform standards. A minor reduction of total coliforms would be
required for Mamaroneck BC&YC. With regard to fecal coliforms, reductions of about 50% to
75% would be required to meet standards at the three northern beaches (Harbor Island, Shore
Acres, and Mamaroneck BC&YC).
The tributary loading reductions were assessed as though the localized sources of coliform bac-
teria are eliminated. Table S-5 gives the percent reductions of total and fecal coliform that
would be required at the tributaries assuming local source control. Harbor Island and Shore
Acres would still require 50% to 75% reductions from tributary sources.
The results shown in Tables S-l through S-5 indicate that the three southern beaches (Beach
Point, Orienta Beach, and Westchester SDS) are in compliance with coliform standards. The
three northern beaches (Harbor Island, Shore Acres, and Mamaroneck BC&YC) require sub-
stantial reductions of coliforms to comply with standards. However, at Mamaroneck BC&YC
compliance with coliform standards may be achieved with the elimination of local sources of bac-
teria. Harbor Island and Shore Acres would require 50% to 75% reductions from the tributaries
in addition to local source control to comply with standards.
xvii
-------
In summary, the analysis presented herein indicates that (1) fecal coliform standards are ex-
ceeded during dry-weather periods at the three northern beaches, (2) coliform concentrations in
the tributaries to Mamaroneck Harbor increase substantially during wet weather, and (3) coli-
form concentrations in the stormwater runoff to the tributaries appear to be typical of those from
suburban areas. Consequently, consistent attainment of bathing-water quality at all beaches
would require effective management of localized coliform sources and tributary coliform sources,
particularly stormwater runoff.
xvin
-------
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Figure S-2. Observed and Calculated Salinity and Fecal Coliform Distributions
at Harbor Water-Quality Stations.
May IS September IS, 1989.
(a) Salinity Distributions.
xix
-------
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Rgure S-2. Observed and Calculated Salinity and Fecal Coliform Distributions
at Harbor Water-Quality Stations, (continued)
May 15 September 15,1989.
(a) Salinity Distributions, (continued)
us.
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Egure S-2. Observed and Calculated Salinity and Fecal Colifonn Distributions
at Haibor Water-QuaL'ty Stations, (continued)
May IS - September 15.1989.
(b) Fecal Colifonn Distributions.
-------
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Figure S-2. Observed and Calculated Salinity and Fecal Coliform Distributions
at Harbor Water-Quality Stations, (continued)
May IS September IS, 1989.
(b) Fecal Coliform Distributions, (continued)
xxn
-------
MAMARONECK HARBOR PROJECT
Data Evaluation and Model Analysis
-------
SOUND
Figure 1-1. Mamaroneck Harbor Study Area
-------
1.0 INTRODUCTION
Mamaroneck Harbor is located in southeastern Westchester County, New York. It is situated on
Long Island Sound. Two primary watersheds discharge to the upper eastern portion of Mama-
roneck Harbor: the Mamaroneck River and Beaver Swamp Brook (see Figure 1-1). In all, these
river basins encompass over 18,000 acres of Westchester County. Virtually the entire area is
serviced by two separate sewer systems (there are some small septic districts): storm water and
sanitary waste, which are not combined. The mouths of these rivers contain nearly all the runoff
water that is discharged to the Harbor.
Currently, the four northernmost Mamaroneck Harbor beaches are closed periodically during the
summer following rainfall events because of coliform contamination. The potential sanitary
sources of coliform contamination, such as dry- and wet-weather overflows from the sanitary
sewer system, have been or are now being corrected. However, it had been shown (Satter-
thwaite, 1987) that stormwater runoff contributes a significant amount of coliform bacteria to the
Harbor. These results are a primary cause for concern regarding storm runoff to the Harbor,
however, the previous analysis had not addressed the cause/effect relationship between pollutant
sources and water quality in the Harbor waters.
The primary objective of this study is to assess the degree to which storm runoff causes water-
use impairment, particularly at six beach locations in the vicinity of Mamaroneck Harbor. Analy-
ses were performed to quantify storm-related discharges to the Harbor. In addition, background
sources of bacteria and the impact of localized bacterial sources were also quantified. A mathe-
matical water-quality model of the harbor was calibrated to evaluate the relationship between
coliform pollutant loadings and water-quality impact. An assessment of the load reductions that
are required to comply with New York State Water Quality Standards is presented.
Westchester County Protocol for Beach Closing
Based on studies conducted by the Westchester County Department of Health, heavy rainfalls in
the watershed of the Mamaroneck River greatly impact the quality of water in Mamaroneck
Harbor. The beaches that receive the greatest impact are those within Mamaroneck Harbor:
Harbor Island Beach (also known as S.E. Johnston Beach), Beach Point Club, Mamaroneck
Beach Cabana and Yacht Club, and Shore Acres Point (hereafter: Harbor Island, Beach Point,
Mamaroneck BC&YC, and Shore Acres, respectively).
Threshold levels have been established to provide a guide for the closing of beaches situated
within the protected area of the Harbor. The threshold levels are as follows.
1-1
-------
Rain on Watershed No. Days To Close Beaches
(inJ2A h) Following Rainfall Events
>0.5 1 day
> 1.0 2 days
>2.0 To be determined
The water-quality analyses that follow are divided into five sections. Each section contributes to
the overall assessment of the sources of conforms, the water-quality impact, and source-abate-
ment requirements.
The following summarizes each section with a brief description of the analyses performed.
Section 2.0 Data Analysis. Data analysis has formed a large part of this work effort; sev-
eral types of data sets were extensively evaluated. Critical to this analysis in particular were
evaluations of data collected near the mouths of the tributaries. Since nearly all the runoff wa-
ters from the study area are transported to the Harbor by the tributaries, a statistical methodolo-
gy was developed by using these data to compute coliform runoff and background loadings to the
Harbor. The analysis used discreet coliform measurements to statistically characterize the quality
of inflow to the Harbor and provided a basis for computing daily loading rates.
Other important data evaluations include analysis of instream tributary data and beach data.
These data were evaluated to assess existing conditions and determine if differences are evident
between wet- and dry-weather samples. Beach data were also evaluated for comparison with
existing water-quality standards.
Section 3.0 Development of Storm-Runoff Model. A storm-runoff model of the Mamaro-
neck Harbor drainage basins was developed to estimate the volume of rainfall-induced runoff
that entered the Harbor. The model calculates temporal discharges to the Harbor that are based
on daily rainfall records. The model is calibrated by using the Geological Survey (Department of
the Interior) flow-monitoring data of the Mamaroneck River and Beaver Swamp Brook.
Section 4.0 Analysis of Storm-Water Concentrations. The analysis of tributary data and
results from the storm runoff model are combined to estimate average coliform concentrations in
runoff waters. The purpose of this analysis is to determine the quality of runoff waters in the
study area and to assess if substantial sanitary flow enters the storm sewer system.
1-2
-------
Section 5.0 Development of Mathematical Water-Quality Model. A mathematical water-
quality model of Mamaroneck Harbor was developed to evaluate the cause/effect relationships
between coliform sources and the water quality in the Harbor and at the beaches. The basic
modeling framework uses a three-dimensional time-variable model developed by Hydroscience in
1978. In this study, the model is recalibrated in the nearshore areas to reproduce 1989 salinity,
fecal coliform, and total coliform profiles.
Section 6.0 Assessment of Load Reduction. The water-quality data evaluations and model
development were used as the basis for estimating the load reductions necessary to comply with-
New York State water-quality standards. The analysis quantified the overall level of control
required to meet total and fecal coliform standards at six beach locations in the Harbor. The.
analysis also quantified the source distribution of coliforms at each of the six beaches. A matrix
is developed indicating the percent coliform reductions required and the percent each major so-
urce of coliforms contributed at each beach site.
1-3
-------
2.0 DATA ANALYSES
Colifonn data are routinely collected at Mamaroneck, New York, beach sites and harbor sites
during the summer months. In 1985, the Mamaroneck River, Beaver Swamp Brook, and the
Sheldrake River, tributaries to Mamaroneck Harbor, were extensively sampled throughout the
basins. In addition, data from checkpoint stations near the mouths of these streams were evalu-
ated for the years 1984, 1985, and 1989. The inland-stream data, checkpoint data, and beach
data are evaluated in the following sections. The evaluation of the checkpoint data includes a
methodology for computing daily coliform loading rates from the major tributaries to the Harbor
waters. The methodology is applied in subsequent data and model analyses.
All samples were collected by the Westchester County Department of Health and were analyzed
by the Westchester County Department of Laboratories and Research, using a lauryl tryptose
MPN method (as described in Standard Methods, 15th edition, as per the NYS-ELAP).
2.1 ANALYSIS OF INLAND-STREAM WATER-QUALITY DATA
During the summer of 1985, water-quality data were collected in the tributaries to Mamaroneck
Harbor. Sample sites (indicated on Figure 2-1) were selected on the Mamaroneck River, Beaver
Swamp Brook (Cuion Creek), and Sheldrake River, a major tributary of the Mamaroneck River.
Sixteen of these sites were sampled extensively for total and fecal coliform bacteria. In all, 283
samples were collected at seven sites on the Mamaroneck River, 191 samples were collected at
four sites on Beaver Swamp Brook, and 184 samples were collected at five sites on the Sheldrake
River.
An analysis was performed to determine if differences are evident between the wet- and dry-
weather samples. A dry-weather day is defined as one in which the total rainfall for the three
consecutive days has been less than 0.2 in., including the sample day. All other sample days are
considered to be wet-weather days.
In the analysis, samples from each water body are grouped to form three data sets: Mamaroneck
River, Beaver Swamp Brook, and Sheldrake River. Probability distributions are developed for
total and fecal coliform bacteria during wet- and dry-weather conditions. These distributions are
shown on Figures 2-2(a)-(c). It is noted that laboratory analytical procedures "capped" the maxi-
mum recorded concentration at 24,000 MPN/100 mL. The results of these analyses are sum-
marized in Table 2-1.
Overall, each of the three streams shares similar characteristics. During dry-weather conditions,
the median total coliform concentrations between streams range from 6000 to 9000 MPN/100 mL
whereas the fecal coliform concentrations range from 1000 to 2000 MPN/100 mL. During wet-
weather conditions, the median total and the fecal coliform concentrations for all three streams
are 24,000 MPN/100 mL or greater and 3500 MPN/100 mL, respectively.
2-1
-------
Figure 2-1. Inland-Stream Sample Sites.
2-2
-------
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WET WEATHER DATA
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(a) Mamaroneck River. 1985.
2-3
-------
WET WEATHER DATA
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(b) Beaver Swamp Brook. 1985.
2-4
-------
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(c) Sheldrake River. 1985.
2-5
-------
Table 2-1. Mamaroneck Harbor 1985 Inland-Stream Data.
Probability Distribution Summary.
Wet
C50
C50
Dry
Total Colifonn
Mamaroneck River
Beaver Swamp Brook
Sheldrake River
> 24,000
> 24,000
> 24,000
> 24,000
> 24,000
> 24,000
8,000
9,000
6,000
> 24,000
> 24,000
> 24,000
Fecal Colifonn
Mamaroneck River
Beaver Swamp Brook
Sheldrake River
3,500
3,500
3,500
24,000
> 24,000
> 24,000
1,000
2,000
1,500
10,000
10,000
10,000
For comparison purposes, the New York State bathing standards for total and for fecal coliform
bacteria are 2400 and 200 MPN/100 ml (geometric mean), respectively. The observed instream
concentrations are all well above these standards.
This analysis implies two important conclusions.
First, wet-weather concentrations are significantly higher than are dry-weather concentrations,
implying that runoff waters contain elevated coliform concentrations that could impact the
water quality of Mamaroneck Harbor.
Second, since dry-weather concentrations exceed the coliform standards, sources of bacteria
that are not related to stormwater may also have an impact on the water quality in Mamaro-
neck Harbor.
Geometric-mean concentrations were also calculated for individual sampling station; these are
shown on Table 2-2. However, this analysis is biased due to the many values that were capped at
24,000 MPN/100 mL. Therefore, the analysis is presented only to show the relative trends within
each stream; the absolute values given in the table are not very meaningful because of the bias.
The analysis shows that the coliform levels in the Mamaroneck and Sheldrake Rivers tend to
increase in the downstream directions (stations Ml and SI being near the mouths). Beaver
Swamp Brook does not demonstrate a discernible trend, considering that station Gl is heavily
influenced by tidal exchange and is not representative of the free-flowing portion of the brook.
The analysis, however, again confirms high coliform concentrations during all periods, but also
distinguishes wet-weather concentrations as being the more severe.
2-6
-------
Table 2-2. Mamaroneck Harbor 1985 Inland-Stream Data.
Geometric Means (MPN/100 mL).
Location
Station
Total
Wet
Coliform
Dry
Fecal
Wet
Coliform
Dry
Mamaroneck River
Ml
M2
M3
M4
M6
M8
M10
14,690
10,880
16,560
13,960
9,940
16,530
7,060
11,040
9,470
8,800
5,550
3,730
5,270
1,880
6,320
6,080
5,520
2,380
1,350
5,200
1,050
3,460
3,130
2,090
720
1,160
1,500
280
Beaver Swamp Brook
Gl
G2
G4
G12
Sheldrake River
SI
S2
S6
S10
S12
8,000
5,700
11,500
22,600
14,440
17,200
15,950
11,730
2,890
1,560
8,630
8,460
22,200
13,500
14,300
10,850
4,070
2,340
2,580
4,060
2,160
5,860
4,510
6,560
4,590
2,460
640
425
2,770
880
7,400
3,410
2,450
3,160
320
170
22 ANALYSIS OF STREAM CHECKPOINT DATA
A detailed statistical analysis of data collected near the mouths of the Mamaroneck River and
Beaver Swamp Brook was performed to evaluate the mass loading rate of cohforms entering the
Harbor from upstream sources. The purpose of the analysis is to develop a methodology for
calculating daily coliform discharges to the Harbor that is based on observed measurements.
That is, the analysis uses discreet coliform measurements to statistically characterize the quality
of inflow to the Harbor and provides a basis for computing daily loading rates.
The data that are used in this analysis were collected during 1984,1985, and 1989; the bulk of the
information dates from 1985. The stations evaluated as checkpoints are station Ml on the Ma-
maroneck River and station G2 on Beaver Swamp Brook. It is to be noted that station Ml, on
the Mamaroneck River, is located just below the tidal fall-line. However, since the samples were
collected near the surface of the stream, the measurements that were made at Ml are assumed
to be representative of freshwater in the Mamaroneck River. This assumption is supported by
the analysis of individual stream stations; Table 2-2 shows the coliform characteristics at station
Ml as being similar to hose at station M2, which is above the fall-line. Since station Ml has a
larger database than does M2, station Ml was selected for the analysis.
2-7
-------
Table 2-3. Characteristics of Checkpoint (1) Coliform Distributions.
Parameter Mamaroneck River Beaver Swamp Brook
Ml 'i MI 'i
Total wet
Total diy
Fecal wet
Fecal dry
39,000
15,700
6,940
3,890
1.82
1.30
1.22
1.07
85,000
18,600
4,200
2,600
2.02
1.53
1.53
1.47
On Beaver Swamp Brook, however, station Gl is substantially influenced by exchange with the
Harbor waters; station Gl has coliform characteristics that are different from those of station G2,
which are above tidal influence (Table 2-2). Therefore, on Beaver Swamp Brook, station G2 was
selected for the checkpoint analysis.
Underlying probability distributions were determined for total and fecal coliform bacteria at the
checkpoints. Data were also grouped by wet and dry conditions. Therefore, for both the Mama-
roneck and Beaver Swamp Brook checkpoints, four probability distributions were developed:
Total coliform wet Total coliform dry
Fecal coliform - wet Fecal coliform - dry
As previously mentioned, analytical methods capped coliform concentrations at 24,000 MPN/100
mL. Therefore, to evaluate the underlying density distributions, an analysis that evaluates "cen-
sored" data was utilized (Cros and Shinizu, 1988). The analysis produces an optimized regression
of log-normal distributions that contain capped data.
The probability distributions of the observed data and the optimized regression analysis are
shown in Figures 2-3(a) and (b). The solid lines on the Figures represent the results of the opti-
mized regression analysis. As illustrated for the total coliform analyses, the optimized regression
projects concentrations that are greater than the capped or censored data at the higher probabili-
ties. The optimized regression lines, however, are best estimates of the true underlying density
distributions, given the restriction in the data sets.
The estimated characteristics of the underlying density distributions are shown on Table 2-3. The
table shows the log-mean (/ij) and log-standard deviation (
-------
A primary objective of this analysis is to develop a methodology to generate coliform loading
rates to the Harbor on a daily basis. This objective is achieved by generating wet- and dry-
weather concentration distributions for a desired period, then randomly multiplying the concen-
trations by measured stream flows that are coded as wet or dry. The concentration distributions
have the characteristics shown in Table 2-3.
The number of values (wet or dry) that need to be generated is variable depending on the peri-
od to be evaluated. For example, if the period to be evaluated contains 60 dry days and 40 wet
days, then 60 dry- and 40 wet-weather values would be generated with the appropriate underlying
density distribution. If the stream flow is on a dry-weather day, then the flow is multiplied by
one of the 60 dry-weather concentrations randomly selected. Each concentration is associated
once with a stream flow. The result is a loading rate of coliforms for each day of stream-flow
record.
The methodology described above is validated with measured checkpoint data. Coliform values
are generated for each of the eight distributions shown on Table 2-3. The number of values
generated varies according to the number of observed measurements. Measured concentrations
are then multiplied by the corresponding stream flow for the day of collection, whereas the gen-
erated values are multiplied randomly by the stream flows. The resulting loading-rate distribu-
tions (organisms per day) using observed concentrations and generated values are shown in Fig-
ures 2-4(a) and (b).
The comparison between measured and calculated for each distribution is very good. Although
differences are noted at some of the higher probabilities, these differences are the result of the
capping restriction of the observed data. A value of 24,000 MPN/100 mL was used to calculate
the observed loading distribution for all those concentrations reported as greater than 24,000
MPN/100 mL. The generated concentrations are not restricted and therefore higher loading
rates are calculated at the higher probabilities.
The methodology described above may be used to calculate coliform input from the streams for
any summer period. The data necessary to generate the input are simply rainfall records and
stream flow. Therefore, coliform loading rates are calculated for the summer periods May 15
through September IS from 1983 through 1989. Total loading rates are calculated for both wet-
and dry-weather periods. Assuming that loading rates during dry periods are representative of
background conditions, the difference between average wet and dry loading rates may be consid-
ered to be the contribution from rainfall-induced runoff. The total average daily loading rates
and relative contributions from background and storm runoff are summarized in Table 2-4. In
general, about 89% of the calculated total coliform loadings is due to storm runoff, and about
67% of the total coliform loadings are from the Mamaroneck River. Similarly, about 74% of the
fecal coliform loadings is due to storm runoff and about 86% of the fecal coliform loadings are
from the Mamaroneck River. Although the earlier Sections show elevated coliform levels during
dry-weather periods, this analysis emphasizes the importance of storm-runoff coliform contribu-
tions.
2-9
-------
Is)
»1>
O
Q 100000
0
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>^
Q_ 10000
T.
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o loeo
o
_l
45 ;
nu in 1 1 nun i j_
01 1 10 tO SO HO 10 «1 H
PROBABILITY
O.I I
10 70 50 HO 90
PROBABILITY
U.IUUII_1-ULI1JIII_1JL_1_1
0 I
10 70 50 BO
PROBABILITY
«ji qq 9
74 -
III111JL1JLJI1IILLL
10 ?o BO 80 *n
PROBABILITY
ot.g
Figure 2-3. ProbabUity Density Distribution Analysis of Colifonn Concentrations.
(a) Mamaroneck River Checkpoint Data. 1984,1985,1989.
-------
z.
o.
_l
o
o
IOOOOM
100000
1000G
100
10
tjl Illllll II Illllll
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§ tKTO
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o
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. 1 1 IO TO *) M DO 01 pq
0
PROBABILITY
PROBABILITY
K>
E
O
z
f.
i
o
=i limn 1 1 mini
100
loLllll
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IIIL
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Dry f
10 99 W M
PROBABILITY
48 ~
JllllllJLLJIIIIUL
n on PO.O
10
o.i
10 TO ra no oo
PROBABILITY
Figure 2-3. Probability Density Distribution Analysis of Cotifonn Concentrations.
(b) Beaver Swamp Brook Checkpoint Data. 1984.1985.1989.
-------
in 10"
3-:
in
l__|
Z 10 '"
tf
0 P^
M
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O.I 1 10 ?0 CO SO OO (I'l OQ.fl O.I 1 10 2O GO no 90 00 91
PROBABILITY PROBABILITY
10 "
in ,o "
in
2 10 "
ID
a 10 "
0
- 10"
J
0
° 10"
_J
1
o
10*
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=
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=
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=
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N= 74 '-_
111111 ii i 1111111 r
O.I 1
PROBABILITY
PROBABILITY
0: Measured. 4: Calculated.
Figure 2-4. Calculated and Measured Coliform Loading Distributions.
(a) Mamaroneck River.
-------
W ,«
in
z 10"
ID
2 ""
»- 10 "
o
0 10"
_J
^J
o
1
10*
Jj
^
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)
K tor
f
TQQCTn
.
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no00 °
i
.
^
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i
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N= 35 !
ill n nun n
VI ,0"
(fi
^ 10"
-------
Mamaroneck Harbor
Sampling Locations
[t) BOAT S'US
Q BEACH SITES
Beach Sampling Sites
(7) HARBOR ISLANB
(D SMO«E »C«ES
(j) MAMARONECK BCiv;
(J) BE*:M POINT
(i) 0*:ENTA BEAIi
0 WES-CHEST" S:E
MILTON HARBOR
Figure 2-5. Mamaroneck Harbor and Beach Sampling Locations.
2-14
-------
Table 2-4. Calculated Coliform Source Distribution.
May 15 through September 15,1983 - 1989.
Total Coliform Fecal Coliform
Mamaroneck River
Storm runoff 58 64
Background 9 22
Beaver Swamp Brook
Storm runoff 31 10
Background 2 4
Average Organisms per Day 1.3 x 1014 10 x 1012
23 ANALYSIS OF BEACH DATA
Coliform bacteria data are routinely collected at six beach locations during summer periods.
These beach sites and the Harbor sampling locations (boat sites) are indicated on Figure 2-5.
Data collected from 1983 through 1989 are evaluated in this analysis.
The probability distributions of total and fecal coliform bacteria are developed for each beach
location, using all years of data. These distributions are indicated on Figures 2-6(a) through (f).
New York State coliform standards for bathing waters are also shown on the Figures. The geo-
metric mean total coliform and fecal coliform concentrations should not exceed 2400 and 200
MPN/100 mL, respectively, according to standards (New York State Sanitary Code, Part 6, Sub-
pan 6-2, 1988). By definition, the geometric mean concentration for a log-normal distribution
corresponds to the value that is not exceeded 50% of the time. The standards also specify that
only 20% of samples may exceed 5000 MPN/100 mL for total coliform bacteria. Therefore, 80%
of the samples collected for total coliform should not exceed this value. For comparison purpos-
es, the standards on the Figures are referred to as the 50% and 80% standards.
Additional probability distributions are developed separating wet- and dry-weather sample days.
The distributions are developed by using all years of data collectively and on a year-to-year basis.
These distributions are summarized in Tables 2-5(a) and (b). The data do not appear to display
any temporal trend from year to year. As an example, the median (50%) concentrations of dry-
weather total coliform and fecal coliform bacteria are illustrated as a function of time in Figure
2-7. The data shown on the Figure do not appear to support any obvious trend. The findings of
the beach-data analysis are summarized in Tables 2-5(c) and (d). The analysis indicates that only
Harbor Island Beach (hereafter: Harbor Island) exceeds the geometric-mean total coliform stan-
dard. However, at the three northern beach sites - Harbor Island, Shore Acres, and the Mama-
roneck BC&YC - total coliform levels exceed the 5000-MPN/100 mL standard for 20% of the
samples analyzed. During periods of dry weather, all total coliform levels are in compliance with
New York State standards.
2-15
-------
loeoc::
itocc:
O
o
toco:
5 MS*
toe
! o °°W
" ' ' ' ll!l"
me
__rT
JTV
_!__! 1_
1 1 1
0
_1_J I_
S
-
3
'" ii"" i ' I
C 1
1C K
PROBABILITY
PROBABILITY
Figure 2-6. Beach Colifonn Probability Density Distributions.
(a) Harbor Island Beach. 1983 - 1989.
2-16
-------
100D9C
O
O
JOCJ6
teoo
ut
0 0
I 11 'i I 1111)1
-aJ=-
1C 1C
tt tt
It i
U
0 00
OOCCEDD
.OCCDT
I I 1JI1III I I I I I I III
0000 0
inn i i i t mini i
PROBABILITY
Figure 2-6. Beach Colifonn Probability Density Distributions, (continued)
(b) Shore Acres Point 1983 - 1989.
2-17
-------
ioss:sc
§
o
U toot
:
e si r»*-
_ rr
1 0°^
: o 00°"'
n i i
d
,
iii.
i
&
_i i 1_
=
oomxico o 1
F= 1
J
\
=.
""'"' ' 1 ! 1
PROBABILITY
PROBABILITY
Figure 2-6. Beach Coliform Probability Density Distributions, (continued)
(c) Mamaroneck BCAYC 1983 - 1989.
2-18
-------
ioc:::t
I099C:
o
o
IOODC
S ««_
tec
: i i 1 1
-
: COEDS
0 0 ODCO
-i i r
a
LJ L_L_
«/
CC
j
00° |
= E
J
]
111(1. J_LJ II 1 1
PROBABILITY
Figure 2-6. Beach Coliform Probabib'ty Density Distributions, (continued)
(d) Beach Point Qub. 1983 - 1989.
2-19
-------
1C
C I
1C 1C K
PROBABILITY
M Ml
!
o
u
K
OEI
0 0 OOOCCD
i i i nun
jinn i i i ii
11 i
PROBABILITY
Figure 2-6. Beach Coliform Probability Density Distributions, (continued)
(e) Orienta Beach. 1983 - 1989.
2-20
-------
o
o
IOODC3C
IMODC
IQDK
nee
IOC
c
: . ! 1 1 i 1 l.lil.
on
0 0 DOX
t tu te
-I 1 I
ciF
cF
1C 1
1 1 1-
ffC
cn/^
i:,illi i I n: -i i i g
3
a
1
s
QC Q 0 -
3
g
i
HUM i i l Illllill 1
i
e
««
N.
u
J
i i nil.i.i i i hit.i 1r
0 0 OOOOOD
in i ilium
(E D
-tP30-
nP
"i"'i ' ' "l""1 '
t.i i
PROBABILITY
Figure 2-6. Beach Coliform Probability Density Distributions, (continued)
(f) Westchester SDS. 1983 - 1989.
2-21
-------
Fecal coliform levels exceed New York State standards at the three northern beaches when (1)
all sample days and (s) only dry-weather sample days are considered. These findings imply that
dry-weather and/or local sources of fecal coliform bacteria may be significant and can cause viola-
tions of fecal coliform standards.
New York Sanitary Code also states
"When fecal coliform density of any sample exceeds 1000 per ml, consideration shall be
given to closing the beach and daily samples shall immediately be collected and analyzed
for fecal coliform for at least two consecutive days."
From the beach-data analysis and probability distributions shown on Figure 2-6, it is noted that
1000 MPN/100 mL fecal coliform bacteria has been exceeded at all beaches to varying degrees.
Table 2-6 summarizes the percent of fecal coliform samples that have exceeded 1000
MPN/100 mL.
The results given in Table 2-6 are not an indicator of a standard violation nor of mandatory
beach closings. However, the results indicate that from 30% to 50% of the historical data at the
three northern beaches would have warranted consideration of Beach closure and additional sam-
pling according to New York State Sanitary Code. As noted previously, however, the sanitary
quality of Mamaroneck Harbor beaches is judged primarily on the basis of total coliform values,
as provided as an option under the New York State Sanitary Code.
2-22
-------
Table 2-5. Beach Data Analysis.
(a) Yearly Median Total Coliform Concentrations.
Beach Location Q
Harbor Island
Shore Acres
Mamaroneck BC&YC
Beach Point
Orienta Beach
Westchester SDS
andition
Wet
Dry
Wet
Dry
Wet
Dry
Wet
Dry
Wet
Dry
Wet
Dry
Total
1983
2,000
900
2,500
400
900
900
90
40
90
Coliform Median Concentration (MPN/100 mL)
1984 1985 1986 1987 1988 1989
6,000
2,200
15,000
1,500
8,000
600
1,000
300
700
60
1,000
400
10,000
2,200
2,000
400
1,500
700
~
10,000
400
500
_
70
100
100
500
9,000
1,000
9,000
3,000
800
400
200
200
150
50
800
20,000
1,000
1,500
500
11,000
300
500
100
150
150
~
8,000
3,000
10,000
1,000
1,000
1,500
1,500
150
900
400
200
(b) Yearly Median Fecal Coliform Concentrations
Beach Location Condition
Harbor Island
Shore Acres
Mamaroneck BC&YC
Beach Point
Orienta Beach
Westchester SDS
Wet
Dry
Wet
Dry
Wet
Dry
Wet
Dry
Wet
Dry
Wet
Dry
Total
1983
400
150
2,000
200
300
600
60
40
50
Coliform
1984
1,200
800
2,500
250
2,000
300
200
40
150
40
150
80
Median Concentration (MPN/100 mL)
1985 1986 1987 1988 1989
2,500
600
1,000
150
450
200
500
300
150
70
30
100
400
3,000
400
1,000
100
350
150
150
70
50
20
_
400
3,000
250
700
200
10,000
300
200
60
150
60
_
2,000
800
500
120
800
500
1,500
80
120
120
_
80
2-23
-------
Table 2-5. Beach Data Analysis, (continued)
(c) Total Coliform Summary. 1983 - 1989.
Concentration Peicentfles (MPN/100 mL)
AD Data Dry-Weather Data
Geometric 80%b Geometric
Mean8 Mean8
"Standard: 2400 MPN/100 mL.
Standard: 5000 MPN/100 mL.
(d) Fecal Coliform Summary. 1983 - 1989.
Harbor Island
Shore Acres
Mamaroneck BC&YC
Beach Point
Orienta Beach
Westchester SDS
2,700
1,700
960
250
230
230
13,540
11,250
5,500
1,100
1,100
950
1,280.
790
470
140
150
230
4,670
3,080
1,850
540
640
870
Concentration Percentiles (MPN/100 mL)
AD Data Dry-Weather Data
Geometric Geometric
Mean8 Mean"
Harbor Island 850
Shore Acres 430
Mamaroneck BC&YC 500
Beach Point 120
Orienta Beach 120
Westchester SDS 110
460
220
290
80
90
110
"Standard: 200 MPN/100 mL.
2-24
-------
Table 2-6. Percent Fecal Colifoim Samples
Exceeding 1000 MPN/100 mL.
% Samples
> 1000 MPN/100 mL
Harbor Island 48
Shore Acres 33
Mamaroneck BC&YC 32
Beach Point 8
Orienta Beach 13
Westchester SDS 4
2-25
-------
JdwUfc
7
S tose
I
1 ice
IL
i
it
= 111111
i
§ .
8 .
0
I HARBOR ISLAND
i i i i i i
' =
* I
0 =
-
s
1
K.c u e < e u.e K.O i'.c M.C 0 c ec.e
YEAR
£ too;
100
*
te
1 1
- ,
- ° ° n o °
° ° 0 »
I SHORE ACRES
YEAR
teooc
£ tooe
u
i
= I 111111 =
is.-
I MAMARONECK BC&YC
i i i i i i
E.C u.c M.C e.c K.C r.e M.C u c K.C
YEAR
IMOC
*OC
1C
s" o
*.
o o.
^ BEACH POlK'f
M.C e.c «-.e K.C M.C r.e M.C M.C tc.e
YEAR
vvw»
teet
I
i ...
It
i
w
to
; 1 1 1 1 1
I TOTAL COL (FORM
I 0- FECAL CO.trofiv
:
= 0
= . S
I ORIEMTA POINT 0
i i i i i
li.e u.c M.C e.c w.c «.c
YEAR
i i =
Z
B
^
' "I
o 5
-
i i
M.C It.O 1C
fooec
I
I
tec
*
B o
" WESTCHESTER SOS
o i
ie
K.C M.C »I.C K.C M.C S7.C M.C M.C M.C
YEAR
Figure 2-7. Yearly Median Total and Fecal Coliform Concentrations.
Dry-Weather Conditions.
2-26
-------
3.0 DEVELOPMENT OF STORM RUNOFF MODEL
A storm runoff model of the Mamaroneck Harbor drainage basins was developed to estimate the
volume of rainfall-induced runoff entering the Harbor. The major drainage areas to the Harbor
include the Mamaroneck River and Beaver Swamp Brook. The Sheldrake River, a tributary to
the Mamaroneck River, is also included. In all, the drainage area encompasses 18,154 acres or
28.4 square miles. The area is serviced almost entirely by a separate sewer system (>99%) so
that it was not necessary to consider significant sanitary flow in the analysis.
Much of the model development is based on work performed by Satterthwaite Associates, Inc.,
for the County of Westchester and the Village of Mamaroneck (Satterthwaite Associates, 1987).
The Satterthwaite model divided the watersheds into a total of 54 subareas. Each subarea was
characterized by a drainage area and an SCS (Soil Conservation Service) curve number (Cn).
The HydroQual storm model uses these same areas and characterizations for its model develop-
ment.
There are some important differences between the Satterthwaite and HydroQual storm-runoff
models. First, the HydroQual model is a time-varying model that computes daily total flows in
the two major watersheds. The Satterthwaite model is a single-event model that can predict
runoff volume only from a single storm event.
There are many advantages to using a time-varying model for this analysis, including the fol-
lowing.
An analysis of bacterial contamination due to runoff waters is by nature a time-varying prob-
lem. The sequence of rainfall events can be an important phenomenon governing the
amount of runoff. The effective SCS curve number and amount of depression storage, for
example, are a function of antecedent conditions.
Runoff may be evaluated on a seasonal basis.
The time-varying model may be calibrated and verified by using actual stream- flow data.
Another difference between the Satterthwaite and HydroQual models is in theory. The Satter-
thwaite model uses the SCS curve-number technique for computing runoff from pervious as well
as from impervious areas. However, the SCS curve-number technique is directly applicable only
to pervious areas, which is characteristic of about 75% of the study area. Satterthwaite Associ-
ates recognized this deficiency and adjusted the curve numbers for each model subarea to ap-
proximate the total runoff from pervious as well as impervious areas. Although these approxima-
tions may be reasonable, HydroQual divided the computation to directly calculate runoff from
impervious areas by using a standard urban runoff equation. Therefore, runoff from pervious
areas is calculated without having to adjust the curve number.
The basis for the storm runoff model is illustrated in Figure 3-1. For each of the 54 model sub-
areas, a total runoff flow is calculated from daily rainfall records. The runoff flows combined
with an estimate of the streams' base flow gives an estimate of the total flow in both the Mama-
roneck River and Beaver Swamp Brook.
3-1
-------
MAMARONECK HARBOR
STORM RUNOFF MODEL
DRAINAGE AREA
PERVIOUS AREA (PA)
IMPERVIOUS AREA
BEAVER SWAMP WATERSHED-33 DRAINAGE AREAS (3004 ACRES)
MAM.ARONECK AND SHELDRAKE WATERSHED-21 DRAINAGE AREAS
(15.150 ACRES)
IMPERVIOUS AREA
PERVIOUS AREA
0R= RUNOFF DEPTH (in.)
R« RAINFALL (in.)
K« RUNOFF COEFFICIENT (0.90-0.95)
Oc« DEPRESSION STORAGE
5 -f(ANTECEDENTR)
Q,.DRUA
(-R-0.2S)
(R + O.BS)
S« RETENTION PARAMETER
1000
CN
-10
C.,' CURVE NUMBER
f(ANTECEDENT R)
TOTAL RUNOFF (QT)
-------
4 OC
C
-r-l
2 * ^ f
*-4
a
1 -r- -r -r
r' i , f ^ 1
mm
1 il i :
( .Jill J ill Ituill -
iSIs
C
*-i
a
-
j ,
_
1 ll =
1 ll 1 IL , i a /ll IlL, Z
. IOC »C W «*
C
*(N
2 roc
»-H
a
~~T" ~T~ -
_
II n J ill ,
r i n i .1 . AJ. Mill ^j_ J LJLJU&iLi
ifis
C
^
* i
C
"
C i I 1 i. II ll. J,i , uJlU :
c tec »« «°« **
19B6
c
2 »»
t i
C
r-
-
"
U ,. i
-
.11 k i .j, j Ul i .1 1 LL ~
in?
c
2 i-«c
r-l
C OC
!
^
kiL
. I.JL. iiA JLL i
4BC
Figure 3-2. Westchester County Airport Rainfall Records.
3-3
-------
The model is calibrated and verified against river-flow data during the summer months (May IS
through September IS) for the years 1983 to 1988. Rainfall records, which drive the model, are
illustrated in Figure 3-2 (Westchester County Airport). Comparisons of calculated and observed
cumulative runoff volumes are made in Figures 3-3(a) and (b). The comparisons show good
agreement for the Mamaroneck River and the Beaver Swamp Brook watersheds.
3-4
-------
a.
L:
0!
c
c
L
ft
E
(C
r
otse1" >eS runc-f
ca]cu2ated
T
cr
DAYS - 19E3
a
C
o
L
«c
e
re
r
!
DAYS -
r
c
o
L
(C
E
tr
DAYS - 19E5
Figure 3-3. Observed and Calculated Cumulative Flow.
(a) Mamaroneck River. 1983 - 1985.
3-5
-------
. nx
O
c
o
L
-------
IS
c
£.
P
IT
P
C
« -
CtservEu r,
c 3 ] c u j a t e c
"I
DAYS - 1953
I
L
o;
K
E
DAYS - 1964
in
L
c.
P
e
DAYS - 3555
Figure 3-3. Observed and Calculated Cumulative Flow, (continued)
(b) Beaver Swamp Brook. 1983 - 1985.
3-7
-------
J
calculates
n
1C
i
tn
L.
v
>
m
03
C
DAYS - 1955
(D
in
L
OJ
ID
C
CD
DAYS - 19E7
C;
(C
DAYS - 1966
Figure 3-3. Observed and Calculated Cumulative Flow, (continued).
(b) Beaver Swamp Brook. 1986 - 1988. (continued)
3-8
-------
4.0 ANALYSIS OF STORM-WATER CONCENTRATIONS
The analysis of the checkpoint data along with results bom the rainfall-runoff model are com-
bined to estimate average coliform concentrations in runoff waters. In each year of simulation
(1983 -1989), the contribution of runoff flow in the Mamaroneck River and the Beaver Swamp
Brook is calculated. Dividing estimated runoff loading rates by the runoff flow gives an estimate
of coliform concentration in the runoff.
Coliform loading rates due to runoff water are estimated through the wet- and dry-weather anal-
ysis discussed in Section 22. If the average daily loading rate calculated for dry-weather condi-
tions is assumed to be the background condition, then the coliform loading rate due to runoff
water is estimated by subtracting the average daily dry-weather coliform loading rate from the
average daily wet-weather coliform loading rate. The results of this analysis are summarized in
Table 4-1.
Table 4-1. Estimated Stormwater Concentrations. 1983 - 1989.
Mamaroneck River Beaver Swamp Brook
Average Runoff Flow 18.2 3.9
(cfs)
Average Total Coliform Concentration 182,000 450,000
(MPN/100 mL)
Average Fecal Coliform Concentration 15,900 11,100
(MPN/100 mL)
The analysis estimates the total coliform and the fecal coliform concentrations in the storm run-
off water to be 180,000 and 16,000 MPN/100 mL, respectively, for the Mamaroneck drainage
basin and 450,000 and 11,000 MPN/100 mL, respectively, for the Beaver Swamp Brook drainage
basin. It is to be noted that these estimates are averages throughout the basin; concentrations
may vary considerably from site to site. In any case, the average concentrations estimated in this
analysis are reasonable when compared to Stormwater concentrations measured in other areas
(Table 4-2). The importance of this result is that the analysis does not indicate a significant
sanitary inflow to the drainage basins. Otherwise, the estimated concentrations would be consid-
erably higher.
4-1
-------
Table 4-2. Observed Stonnwater Colifoim Concentrations in Other Studies.
Geometric Mean Concentrations
(MPNAOOmL)
NYC208b UNURP*
Total coliform 120,000 - 660,000 90,000 - 240,000
Fecal ccliform 40,000-130,000 20,000- 45,000
'Long Island National Urban Runoff Program.
York City 208 Water Quality Planning Study.
4-2
-------
5.0 DEVELOPMENT OF MATHEMATICAL WATER-QUALITY MODEL
A mathematical water-quality model of Mamaroneck Harbor has been developed to evaluate the
cause/effect relationships between coliform sources and water quality in the Harbor and at the
beaches. The basic modeling framework uses a three-dimensional time-variable model developed
by Hydroscience, Inc., in 1978 for the Mamaroneck Harbor Outfall Study. In this study, the
model is recalibrated in the nearshore areas to reproduce salinity, total coliform, and fecal coli-
form profiles. The model is then used as a tool to develop allocations of coliform bacteria from
nonpoint-source discharges.
5.1 CALIBRATION OF MODEL TRANSPORT
The previously developed three-dimensional water-quality model consists of 374 segments in two
layers; it is shown in Figure 5-1. Each layer contains 187 segments. Model transport character-
istics considers geometry, advective flow, and mixing by tidal dispersion. The primary area of
concern in the original investigation, however, was 0.5 to 1.5 miles into Long Island Sound.
Therefore, the inner Harbor area was not rigorously calibrated.- In this analysis, Mamaroneck
Harbor area is recalibrated with salinity data collected during the summer of 1989. Figure 5-2
enlarges the model segmentation for the area of concern in this study.
Salinity, as a conservative substance, is used to calibrate the advective/dispersive transport in
Mamaroneck Harbor. The major sources of freshwater flow include the Mamaroneck River and
Beaver Swamp Brook. These flows are routed through the Harbor and out to Long Island
Sound. As part of the calibration process, transport parameters, such as dispersion coefficients,
are adjusted to reproduce observed data.
During the summer of 1989, special field measurements were collected by the Westchester Coun-
ty Department of Health at the request of HydroQual, Inc. These measurements were specified
to ascertain the degree of vertical stratification in the water column. The first request specified
that both top and bottom measurements be collected as part of the routine Harbor boat surveys.
The second request required a special field cruise after a storm event to measure vertical casts of
salinity at the Mamaroneck Harbor sampling stations. These vertical casts were collected by
Westchester County on September 15,1989, following a 1.60-in. rainfall.
Results of the September 15, 1989, survey are shown in Figure 5-3. Stations 16 and 105b are
near the mouths of the Mamaroneck River and the Beaver Swamp Brook, respectively, as shown
in Figure 2-5. Stations 17,117b, 15, and 14 are positioned successively away from the freshwater
sources and into Long Island Sound. The data demonstrate that the freshwater entering the
Harbor stays very close to the surface. At stations 16,105b, 17, and 117b salinity concentrations
decreases rapidly in the upper 2 to 3 ft of the water column, indicative of freshwater flowing over
the surface of the water column. This phenomenon is not unusual and has been observed in
other estuarine basius in the New York area (e.g., the Paerdegat Basin, Gowanus Canal).
5-1
-------
F^iaSpggE
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NAUTICAL CHART 12364
NEW HAVEN HARBOR ENTRANCE
?v AND PORT JEFFERSON
TO THROGS NECK
CONNECTICUT-NEW YORK
Figure 5-1. Thrce-Dimensional Water-Quality Model Segmentation.
-------
MAMARONECK
IIIVI R
MILTON HrtPBOR
Figure 5-2. Mamaroneck Hartor Model Segments.
-------
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SALINITY SALINITY
Figure 5-3. Vertical Salinity Profiles. September 15,1989.
5-4
-------
Model segment geometiy was adjusted to reflect the stratified condition in the Harbor. The up-
per-layer depths were set to 2 ft for segments 1 through 33 whereas the corresponding lower-
layer segments were assigned depths equal to the balance of the total water-column depth.
Freshwater flows were routed accordingly through the surface segments.
Model calibration used salinity data collected between May 15, 1989, and September IS, 1989.
Freshwater flow from the Mamaroneck River and Beaver Swamp Brook were assigned on a daily
basis during the same period from Geological Survey monitoring records. Horizontal and vertical
dispersion coefficients are adjusted to reproduce observed data collected at the surface and on
the bottom of the water column.
Comparisons of observed and calculated salinity profiles are shown in Figure 5-4. The horizontal
and vertical dispersion coefficients were assigned the values of 0.5 miles2/day and 3 x 10"8 to 1 x
10"6 miles2/day (0.01 to 0.3 cm2/s), respectively. The figures indicate very good comparisons be-
tween the calculated and the observed concentrations. Another method of comparison is to con-
struct the probability distributions of calculated and observed data for the simulation period.
These comparisons are shown in Figure 5-5. Very good agreement between calculated and ob-
served concentrations is evident.
52 COUFORM CALIBRATION
Coliform concentrations measured in 1989 were reproduced by using the time-variable water-
quality model. The transport conditions are those developed in the previous section to repro-
duce salinity concentrations. The tributary loads for the Mamaroneck River and Beaver Swamp
Brook are calculated by using the methodology described in Section 2.2: Analysis of Stream
Checkpoint Data.
The coliform dieoff rate is calculated by using an expression developed for the New York 208
model (Hydroscience, 1978). The expression correlates the coliform dieoff rate salinity and tem-
perature. For Mamaroneck Harbor, the calculated coliform dieoff rate averages about 1.4 per
day.
The water-quality model is first calibrated to fecal coliform bacteria since the tributary loads for
fecal coliform bacteria are more reliable than for total coliform bacteria. As discussed in Section
2.2, coliform measurements were capped at 24,000 MPN/100 mL. Therefore, at higher concen-
tration percentiles, the tributary loadings are the result of an extrapolation technique. Since the
capping of coliform measurements affects total coliform more often than fecal coliform, the total
coliform loading estimates are the result of more extrapolated values and, therefore, are not as
reliable as those developed for fecal coliform.
5-5
-------
The calculated temporal concentrations of fecal coliform bacteria are compared with measured
concentrations of the Harbor surveys and beach sampling on Figures 5-6(a) and (b), respectively.
Likewise, the measured and calculated temporal concentrations of total coliform bacteria are
compared on Figures 5-7(a) and (b). The first day of simulation (Day 0) corresponds to May 15,
1989. The simulation runs for 126 days until September IS, 1989. Model results are compared
against data collected at five Harbor survey stations and at six beach sites. The comparisons show
good agreement between calculated and observed coliform concentrations.
Probability distributions of calculated and observed fecal coliform concentrations are also com-
pared. Comparisons against the Harbor survey data and the beach data are shown on Figures
5-8(a) and (b), respectively. In general, these comparisons are favorable. However, there are
areas where the comparisons between calculated and observed distributions show discrepancies.
These discrepancies are particularly evident at some of the beach sites, particularly Mamaroneck
Beach Cabana and Yacht Club (hereafter: Mamaroneck BC&YC), Orienta Beach, and to some
extent at Harbor Island Beach (hereafter: Harbor Island). At these locations, the model appears
to underestimate fecal coliform distributions.
The discrepancies in coliform levels at some of the beaches may be due to sources of bacteria
that are not accounted for in this model analysis. These waste sources are probably localized,
and may include disposal from recreational boats or local runoff and discharges. Model input
includes waste sources from the tributaries and the Mamaroneck STP. The impact of localized
sources of bacteria is evaluated in Section 6.0: Assessment of Load Reduction. However, local
discharges and impact should be quantified through additional field efforts.
5-6
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Figure 5-4. Comparison of Observed and Calculated Salinity Concentrations.
May 15,1989, to September 15,1989.
5-7
-------
SALINITY fpph]
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DAYS - 19ES
Figure 5-4. Comparison of Observed and Calculated Salinity Concentrations.
May 15,1989, to September 15,1989 (continued).
5-8
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5-9
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Figure 5-5. Comparison of Observed and Calculated Salinity Distributions.
May 15,1989, to September 15,1989 (continued).
5-10
-------
1COOOOO
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DAYS - 1969
Figure 5-6. Comparison of Observed and Calculated Fecal Colifonn Concentrations.
May 15 to September 15, 1989.
(a) Harbor Survey Stations,
5-11
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Figure 5-6. Comparison of Observed and Calculated Fecal Colifonn Concentrations.
May 15 to September 15,1989. (continued)
(a) Harbor Survey Stations, (continued)
5-12
-------
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Figure 5-6. Comparison of Observed and Calculated Fecal Colifonn Concentrations.
May 15 to September 15, 1989. (continued)
(b) Beach Samples.
5-13
-------
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Figure 5-6. Comparison of Observed and Calculated Fecal Coliform Concentrations.
May 15 to September 15,1989. (continued)
(b) Beach Samples, (continued)
5-14
-------
16
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Figure 5-7. Comparison of Observed and Calculated Total Coliform Concentrations.
May 15 to September 15, 1989.
(a) Harbor Survey Stations.
5-15
-------
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Figure 5-7. Comparison of Observed and Calculated Total Coliform Concentrations.
May 15 to September 15,1989. (continued)
(a) Harbor Survey Stations, (continued)
5-16
-------
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Figure 5-7. Comparison of Observed and Calculated Total Coliform Concentrations.
May 15 to September 15,1989. (continued)
(b) Beach Samples.
5-17
-------
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Figure 5-7. Comparison of Observed and Calculated Total Coliform Concentrations.
May 15 to September 15,1989. (continued)
(b) Beach Samples, (continued)
5-18
-------
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Figure 5-8. Comparison of Observed and Calculated Fecal Coliform Distributions.
May 15 to September 15,1989.
(a) Harbor Survey Stations.
5-19
-------
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Figure 5-8. Comparison of Observed and Calculated Fecal Coliform Distributions.
May 15 to September 15,1989. (continued)
(a) Harbor Survey Stations, (continued)
5-20
-------
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PROBABILITY
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Figure 5-8. Comparison of Observed and Calculated Fecal Coliform Distributions.
May 15 to September 15,1989. (continued)
(b) Beach Samples.
5-21
-------
1000COC
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PROBABILITY
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Figure 5-8. Comparison of Observed and Calculated Fecal Coliform Distributions.
May 15 to September 15,1989. (continued)
(b) Beach Samples, (continued)
5-22
-------
6.0 ASSESSMENT OF LOAD REDUCTION
The water-quality data evaluations and modeling analyses of the previous Sections are used as
the basis for estimating the load reductions necessary to comply with New York State water-
quality standards. The primary objective of this Section is to quantify the levels of control re-
quired to meet coliform standards at the six beach locations in Mamaroneck Harbor. The analy-
sis also quantifies, to the extent possible, the source distribution of coliforms at each beach.
6.1 ASSESSMENT OF SOURCE DISTRIBUTION
Section 2.2 evaluates the source distribution of coliform bacteria from the tributaries. This Sec-
tion also considers the magnitude of localized sources of bacteria. The following analysis is based
on 1989 fecal coliform data because it is the basis for model calibration. Although it is recog-
nized that there will be year-to-year variability, the analysis provides an insight to the magnitude
of localized sources.
The key data-evaluation results and the modeling results for 1989 are summarized in Table 6-1.
The table shows the observed and the calculated geometric-mean concentrations of fecal coliform
bacteria at each beach site.
The results show observed geometric-mean concentrations higher than calculated geometric-
mean concentrations at all beaches except Shore Acres. However, it is noted that the long-term
geometric mean at Shore Acres is more than double that observed in 1989 (430 and 190
MPN/100 mL, respectively). At other beaches, the long-term geometric means [Table 2-S(d)] are
comparable to the 1989 results.
Table 6-1. Comparison of Calculated* and Observed Geometric-Mean
Concentrations of Fecal Coliform Bacteria.
Geometric Mean
Observed Calculated
Harbor Island
Shore Acres
Mamaroneck BC&YC
Beach Point
Orienta Beach
Westchester SDS
860
190
550
140
150
80
540
310
200
120
70
70
"Calculated concentrations do not include local impact.
6-1
-------
Table 6-2. Observed MLE and Calculated Mean Fecal Colifonn Concentrations
and Source Distribution.
Harbor Island
Shore Acres
Mamaroneck BC&YC
Beach Point
Orienta Beach
Westchester SDS
Observed
MLE
1,900
840
1,650
500
300
140
Calculated
Mean
(Tributary)
1,675
1,030
690
430
220
220
Approx.
Percent
Tributary
88
100
42
86
73
100
Approx.8
Percent
Local
12
0
58
14
27
0
"Approximations are based on 1989 analyses. Percentages may vary due to year-to-year
fluctuations, monitoring error, and model accuracy.
The calculated concentrations are due primarily to tributary loadings to the Harbor. Treatment-
plant effluent impact is insignificant, and there are no treatment-plan bypasses affecting the cali-
bration data set. Therefore, differences between observed and calculated concentrations at the
beaches are assumed to be the result of localized sources of fecal coliform bacteria. These local
sources of bacteria have not been identified in this project, but could be the result of poor recre-
ational boating practices or local wildlife activity (ducks, geese, etc.).
The contribution of local sources at each beach site is assessed by comparing the summer mean
observed and calculated concentrations. It is noted, however, that the arithmetic mean of a finite
data set that is log-normally distributed is best estimated through a standard statistical analysis.
That is, the best approximation of the mean concentration is estimated by the most likely esti-
mate (MLE) and is calculated by
MLE = expO*! + W ffj) , (6-1)
where ft1 is the log-mean and of is the log-variance.
Therefore, the best likely estimates of the mean concentrations (MLE) are calculated at each
beach for the observed measurement. The ratio of the calculated mean to observed MLE con-
centrations is then assumed to represent the percentage of coliforms at the beach site that is due
to the tributary basin loadings. Likewise, the balance of the observed concentrations is assumed
to be due to local input of bacteria. The calculated distributions between tributary and local
bacteria sources are shown in Table 6-2. The results indicate that fairly substantial localized
coliform input is estimated at Mamaroneck Beach Cabana and Yacht Club (hereafter: Mamaro-
neck BC&YC) and Orienta Beach. The percentages given in Table 6-2 are approximations
based on the 1989 data and model evaluations. Depending on year-to-year variability, monitor-
ing error, and model accuracy, these percentages may vary. The analysis, however, gives a scien-
tific basis for indicating where localized input may be significant.
6-2
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Table 6-3. Calculated Tributary Colifonn Source Distribution.
Total Oolifoim Fecal Colifonn
Mamanneck River
Storm runoff 58 64
Background 9 22
Total 67 86
Beaver Swamp Brook
Storm runoff 31 10
Background 2 4
Total 33 14
Tributary source distributions, evaluated in Section 2.2, are summarized in Table 6-3. The total
source distribution, considering local input, is then reproportioned at each beach. These distribu-
tions (Table 6-4) indicate that most of the coliform bacteria at the beaches originate from the
Mamaroneck River basin, with the exception of Mamaroneck BC&YC. At Mamaroneck
BC&YC, over 50% of the coliforms are estimated from local sources. At the other-beaches;
between 49% and 86% of the coliforms are estimated from the Mamaroneck River basin. Of
the coliforms from the Mamaroneck River basin, 89% of the total coliform and 74% of the fecal
coliform are attributed to runoff (Table 6-3).
62 ESTIMATED LOAD-REDUCTION REQUIREMENTS
To assess the required abatement necessary to comply with New York State water-quality stan-
dards, the beach data analysis of Section 23 is reviewed. For data collection between 1983 and
1989, the geometric-mean total and fecal coliform concentrations and the 80th percentile total
coliform concentrations are compared against standards. These comparisons, summarized in
Table 6-5, indicate that all coliform standards are exceeded at Harbor Island. At Shore Acres
and Mamaroneck BC&YC, the 80th percentile total coliform standard and the geometric-mean
fecal coliform standard are exceeded. The three southern beaches [Beach Point, Orienta Beach,
and Westchester Summer Day School (hereafter: Westchester SDS)] are in compliance with all
standards.
The estimated load-reduction requirements to meet water-quality standards at each beach are
summarized in Table 6-6. The table shows that at Harbor Island and Shore Acres an approxi-
mate 60% reduction would be required to meet total coliform standards. A minor reduction of
total coliforms would be required for Mamaroneck BC&YC. With regard to fecal coliforms,
reductions of about 50% to 75% would be required to meet standards at the three northern
beaches (Harbor Island, Shore Acres, and Mamaroneck BC&YC).
6-3
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Table 6-4. Calculated Total Source Distribution for Total and Fecal Colifoim Bacteria
SOURCE DISTRIBUTION (%)
Total Colifonn Fecal Coliform
Local" Mamaroneck Beaver
River Basin Swamp Brk.
Basin
Local" Mamaroneck Beaver
River Basin Swamp Brk.
Basin
Harbor Island 12
Shore Acres 0
Mamaroneck BC&YC 58
Beach Point 14
Orienta Beach 27
Westchester SDS 0
59
67
28
58
49
67
29
33
14
28
24
33
12
0
58
14
27
0
75
86
36
74
63
86
13
14
6
12
10
14
"Approximate from 1989 analyses. Percentages may vary due to year-to-year fluctuations, moni-
toring error, and model accuracy.
Tributary loading-reductions are also assessed as though the localized sources-of coliform bac-
teria have been eliminated. Table 6-7 shows the percent reductions of total and fecal coliform
that would be required at the tributaries when assuming local source control. At these condi-
tions, the total coliform geometric-mean standard would be in compliance at all beaches. At
Harbor Island and Shore Acres, the total coliform 80th percentile standard and the fecal coliform
standard would be in violation of standards. The tributary reductions required to meet coliform
standards at Harbor Island and Shore Acres would be about 50% to 60% of total coliform and
45% to 75% of fecal coliform.
Table 6-5. Comparison of Long-Term Total and Fecal Coliform Concentrations
against Standards
FECAL COLIFORM
Geometric Standard
Mean
TOTAL COLIFORM
Geometric Standard C& Standard
Mean
Harbor Island
Shore Acres
Mamaroneck BC&YC
Beach Point
Orienta Point
Westchester SDS
850
430
500
120
120
110
200
200
200
200
200
200
2,690
1,720
960
250
230
230
2,400
2,400
2,400
2,400
2,400
2,400
13,540
11,250
5,480
1,120
1,140
950
5,000
5,000
5,000
5,000
5,000
5,000
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Table 6-6. Estimated Load Redactions Required To Meet Water-Quality Standards
PERCENT REDUCTIONS
Total Colifonn Fecal Ooliform
Geometric Mean Cg,
Harbor Island
Shore Acres
Mamaroneck BC&YC
Beach Point
Orienta Point
Westchester SDS
11
0
0
0
0
0
63
56
9
0
0
0
Geometric Mean
76
53
60
0
0
0
The results given in Tables 6-6 and 6-7 indicate that the three southern beaches (Beach Point,
Orienta- Beach, and' Westchester SDS) are in compliance with coliform standards. The three.
northern beaches (Harbor Island, Shore Acres, and Mamaroneck BC&YC) require substantial
reductions of coliforms to comply with standards. However, at Mamaroneck BC&YC, compli-
ance with coliform standards may be achieved by the elimination of local sources of bacteria.
Harbor Island and Shore Acres would require 50% to 75% reductions from the tributaries in
addition to local source control to comply with standards.
Table 6-7. Reductions of Total and Fecal Coliform Required at Tributaries,
Assuming Local Source Control
PERCENT REDUCTIONS
Total Coliform Fecal Colifonn
Geometric Mean Can Geometric Mean
Harbor Island
Shore Acres
Mamaroneck BC&YC
Beach Point
Orienta Point
Westchester SDS
0
0
0
0
0
0
58
51
0
0
0
0
73
46
0
0
0
0
6-5
-------
The analyses presented in the previous Sections indicate that
Fecal coliform standards are exceeded during dry-weather periods at the three northern
beaches.
Coliform concentrations in the tributaries to Mamaroneck Harbor increase substantially dur-
ing wet weather.
Coliform concentrations in the stormwater runoff to the tributaries appear to be typical of
those from suburban areas.
Consequently, consistent attainment of bathing-water quality at all beaches would require effec-
tive management of localized coliform sources and tributary coliform sources, particularly storm-
water runoff.
6-6
-------
IS) REFERENCES
Crow, E.L, and Shinuzu. 1988. Log-Normal Distributions. Marcell Decker, New York, NY.
Hydroscience. 1978. Evaluation of wastewater discharge alternatives, Mamaroneck Harbor.
Prepared for Hazen and Sawyer, Engineers, New York, NY.
Hydroscience. 1978. NYC 208 Task Report. Seasonal Steady State Model, PCP Task 314.
Prepared for Hazen and Sawyer, Engineers, New York, NY.
Satterthwaite. 1987. Mamaroneck Harbor pollution study, Westchester County, NY. Prepared
by Satterthwaite Associates, Inc., for the County of Westchester and the Village of Mama-
roneck.
7-1
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Appendix D
"MAMARONECK HARBOR ACTION PLAN DEMONSTRATION PROJECT
For the convenience of the reader, Figure 1 cited in Section 2.2 in the
main text was reproduced from this brochure. It is also included here as
originally disseminated to the public as part of Task 4, Development of
Education Program, utilized in this work assignment.
-------
THE PROBLEM
Mamaroneck Harbor beaches must
periodically be closed after rainstorms
because of contamination by coliform
bacteria. Coliform are bacteria that
come from the digestive system of man
and other animals, and their abundance
in water is used to indicate the presence
of other organisms that are a health
concern. Studies have shown that
stormwater entering the harbor is one
source of the coliform bacteria.
(_oliform can be present in many places
in the environment. During a rainstorm,
the rain washes coliform bacteria into the
storm drains from where they eventually
can reach Mamaroneck Harbor.
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-------
THE LONG ISLAND SOUND STUDY
The States of New York and
Connecticut, the U.S. Environmental
Protection Agency, local agencies and
organizations, universities, industries, and
the public together form the Long Island
Sound Study, whose goal is to restore
and protect the resources of Long Island
Sound. As part of its management plan
for Long Island Sound, the Long Island
Sound Study developed a priority action
plan to address the problem of bacterial
contamination of Mamaroneck Harbor
by stormwater.
Participants in the Action Plan are:
Town of Harrison
Village of Mamaroneck
Town of Mamaroneck
I City of New Rochelle
I City of Rye
I Village of Rye Brook
I Village of Scarsdale
I City of White Plains
I Westchesler County
I New York State Department of
Environmental Conservation
I U.S. Environmental Protection
Agency Region II
BEST MANAGEMENT PRACTICES (BMPs)
CAN HELP SOLVE THE PROBLEM
Best Management Practices (BMPs) are
ways to help alleviate the bacterial
contamination problem. These practices
can range from building expensive structures
that reduce the volume or treat the
stormwater entering the harbor to simple
"good housekeeping" practices we can all
follow to eliminate the contaminating
materials before they enter the stormwater.
We have selected three "housekeeping"
BMPs to use in demonstrating how effective
simple measures can be in helping to keep
the harbor clean and the beaches open.
The BMPs are
CLEANING OF CATCH BASINS.
Catch basins are storage areas that
are part of the stormwater collection
system. Keeping these basins free of
debris helps remove bacteria that
have become trapped in the basin.
STREET CLEANING. Removing dirt
and litter from the streets with
mechanical sweepers can help
reduce the numbers of bacteria
entering the stormwater collection
system.
CONTROL OF PET WASTES. Large
numbers of coliform bacteria are
present in pet waste. By cleaning up
after our pets, we can prevent these
bacteria from being carried into the
harbor by stormwater.
WHAT YOU CAN DO TO HELP
We are asking all of you who enjoy the
harbor and its beaches and other resources
to assist us in demonstrating how these
simple BMPs can help keep the water clean
and the beaches open. The effectiveness of
three BMPs will be tested in the Halstead
Avenue East Outfall System. This system
runs in a zigzag pattern from where
Halstead crosses the Mamaroneck, along
Union Avenue, Hinman Place, Melbourne
Avenue, and Brook Street, to the intersection
with North Barry Avenue. The catch basin
cleaning will be conducted by trained
personnel, but you can help us with the
other BMPs.
Help us when we sweep the streets!
When cars are left parked on streets
during cleaning, the effectiveness of
the cleaning is greatly reduced.
Please don't park your car on the
street on the days that street
sweeping is scheduled in your area!
Please help keep the streets and
catch basins clean. Compost or bag
your grass clippings and other yard
waste for pick-up at curbside.
Please control your pet's waste I
Animal waste is the source of large
numbers of coliform bacteria. Clean
up after your pets wherever they may
"90"! ,
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