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EPA /903/R-06/004
August 2006
Proceedings of the Workshop on
Stormwater Management
and Mosquito Control
Edited by
Patricia Bradley
U.S. Environmental Protection Agency
and
Frederick W. Kutz, Ph.D.
Consultant in Environmental Sciences
February 9, 2005
WorWic Community College
Salisbury, Maryland
U.S. Environmental Protection Agency
Office of Research and Development
Fort Meade, Maryland 20755-5350
Recycled /Recyclable
Printed with Vegetable Oil Based Inks on 100%
Post-consumer Process Chlorine Free Recycled Paper
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Abstract
A workshop on various aspects of stormwater management was held at WorWic Community
College, Salisbury, MD, on February 9, 2005. The management of stormwater received
national prominence as an important part of the Federal Clean Water Act. The workshop
emphasized four distinct but related attributes of stormwater management areas: water
quality considerations, mosquito production, wildlife habitat and engineering parameters.
The objective of the meeting was to develop consensus guidance and recommendations for
the construction, modification and maintenance of facilities that promote water quality, limit
mosquito production and provide wildlife habitat to the extent possible. Workshop organizers
developed a list of expectations that considered the role of stormwater best management
practices (BMPs) in the context of legislatively and regulatorily driven objectives,
engineering considerations and ecological considerations (wildlife habitat and mosquito
production). The results of the workshop indicated that it is possible to achieve water quality
objectives and at the same time to limit mosquito production in stormwater management
facilities. The success of simultaneously resolving these two objectives rest with site specific
planning and flexible, innovative engineering solutions. A critical task associated with
stormwater management areas is periodic maintenance. Maintaining stormwater areas falls to
the property owner. In most cases, the owner is an individual or a homeowners' association
unaware that these areas require ongoing and sometimes extensive periodic maintenance.
The existence and effects of predators on mosquito populations in stormwater management
facilities remain somewhat unknown; certain species offish appear to be the best predators.
Similarly, the use of stormwater areas as wildlife habitat has been poorly explored.
Presentations made at the workshop can be found on the EPA Web site at
http://www.epa.gov/maia/html/swmprog.html.
Keywords: Stormwater management facilities, mosquito production, wildlife habitat,
stormwater engineering, ecological services, mosquito control, Clean Water Act
Proceedings of the Workshop on Stormwater Management and Mosquito Control
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Acknowledgements
Many people and organizations assisted in the planning and implementation of the
Storm water Workshop. Their contributions ranged from making individual suggestions,
to working on the steering committee and providing services needed to hold a successful
workshop. Acknowledgement with thanks is made for all of their efforts.
We gratefully acknowledge the following organizations for providing either financial or in-
kind support for the workshop:
Delaware Center for the Inland Bays
Delaware Department of Natural Resources and Environmental Control
Maryland Coastal Bays Program
Maryland Department of Agriculture
Maryland Department of the Environment
Maryland Pesticide Advisory Committee
U.S. Environmental Protection Agency - MAIA Team
WorWic Community College
The major planning and implementation for the workshop was accomplished by using
a steering committee. The steering committee initiated and managed all aspects of the
workshop (Table 1, pg 2).
The appropriate citation for this report is:
Bradley, P. and F.W. Kutz (eds.). 2006. Proceedings of the Workshop on Stormwater
Management and Mosquito Control. U.S. Environmental Protection Agency, Office of
Research and Development. EPA/903/R-06/004
iv Proceedings of the Workshop on Stormwater Management and Mosquito Control
-------
Contents
Abstract iii
Acknowledgements iv
Introduction 1
A Workshop on Stormwater Management and Mosquito Control, Frederick W. Kutz
Stormwater Management and Mosquito Control: A Regional Perspective, Kevin Magerr
(Written by Patricia Bradley)
Stormwater Management Regulations 13
Overview of Stormwater Management Regulations in Delaware, Randy Greer
Stormwater Management in Maryland - A Regulatory Overview, Charlie Wallis
Mosquito Production Considerations 17
A National Perspective, Joe Conlon
Stormwater Management Areas as Mosquito Larvae Habitat in the State of Maryland,
Cyrus R. Lesser and Jeannine Dorothy
Stormwater Structures and Mosquito Production in Calvert County, V. Wilson Freeland
Mosquito Production Issues in Delaware's Stormwater Management Basins,
William Meredith, Thomas Moran and Darin Callaway
Predictors of Mosquito Abundance in Stormwater Ponds in Delaware, Jack Gingrich
Wildlife Habitat Considerations 31
Ecosystem and Wildlife Habitat Considerations in Stormwater Management,
Roger Tanker si ey
Facilitated Discussion (Kent Thornton) 41
Summary 45
Unfinished Business (Frederick Kutz/Roman Jesien) 47
Appendix A 51
AMC A Position Paper, Spring Washington Conference, 2006
Appendix B 53
Workshop Attendees
Appendix C 57
Glossary
Appendix D 71
Sources of Information
Proceedings of the Workshop on Stormwater Management and Mosquito Control
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Introduction
A Workshop on Stormwater Management and Mosquito Control
Presented by:
Frederick W. Kutz, Ph.D.1, 4967 Moonfall Way, Columbia, MD 21044
Stormwater management has been a subject
generating controversy since its inception under
the Federal Clean Water Act. Most Stormwater
management strategies include the use of a
collection basin, pond or area into which Stormwater
from roads, parking lots, etc., drains. The principal
purpose of these ponds is to provide treatment that
will improve the quality of the water as it drains
into the ground water layers. The natural processes
in the pond theoretically will reduce the levels of
nutrients, sediment and toxic pollutants in the water.
Some observers have noted that these ponds provide
limited habitat for wildlife and waterfowl.
Stormwater management areas require periodic
maintenance. The task of maintaining Stormwater
areas falls to the property owner. In most cases, the
owner is an individual or a homeowners' association.
Some individuals or associations seek professional
support while others, particularly those with dry
ponds, choose to manage them on their own. Still
other property owners may not even be aware that
these areas require ongoing and sometimes extensive
periodic maintenance.
Certain types of these areas (both well maintained
and poorly maintained) have the potential to
provide productive larval habitat to certain species
of mosquitoes (Banks 2003 and Walton 2003).
The adults of several species of mosquitoes found
in these areas have been incriminated as efficient
vectors of human and animal diseases, i.e., West
Nile virus. The presence of these vector species
within a developed area presents public health and
economic challenges that requires some type of
mitigation (Zohrabian et al. 2004). Mosquito control
in these management areas usually involves the
use of pesticides. In certain pond environments,
however, populations of predatory fish and perhaps
some other animals seem to contribute to control of
mosquito larvae.
These attributes of water quality improvement,
limited habitat provision and mosquito production
when considered as an assemblage pose conflicting
and complex problems for all concerned. In many
cases the exact location of these areas is unrecorded.
Also, the efficacy of the areas in providing their
environmental services is not monitored. Only
limited information is available on non-chemical
means of mosquito control. Stormwater management
area maintenance is lacking in many locations. The
grand convergence of these factors provides ample
justification for convening a workshop to discuss
Stormwater management with emphasis on mosquito
control in an open, non-confrontational forum.
OBJECTIVE
This workshop focused exclusively on Stormwater
management areas in the Coastal Plain of Maryland
and Delaware. It emphasized four distinct but
related attributes of these structures: water quality
considerations, mosquito production, wildlife
habitat and engineering parameters. The objective
of the meeting was to develop consensus guidance
recommendations for the construction, modification
and maintenance of these facilities that promote
water quality, limit mosquito production and provide
wildlife habitat to the extent possible.
The Steering Committee developed a list of
expectations for the workshop to aid in guiding
the discussions and focusing comments. Each
participant was requested to consider the role of
Stormwater BMPs in the context of legislatively/
regulatorily driven objectives, engineering
considerations and ecological considerations
(wildlife habitat and mosquito production).
Although Dr. Kutz is an independent consultant in environmental
sciences, his efforts on behalf of the workshop were voluntary
as a contribution to his work as a member of the MD Pesticide
Advisory Committee.
Proceedings of the Workshop on Stormwater Management and Mosquito Control
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Participants were asked to arrive at the workshop prepared to discuss their thoughts on the
following six issues:
1. Which stormwater BMPs have the greatest potential for mosquito production?
2. What maintenance practices, by BMPs, would reduce mosquito production and
improve BMP effectiveness?
3. What mosquito control practices are recommended for different BMPs?
4. What re-engineering designs might decrease mosquito production but retain
wildlife habitat and BMP efficiency?
5. What recommendations are there for increasing public awareness and
knowledge about the need for stormwater BMPs and the potential for mosquito
production and control?
6. What research is needed to contribute to answering the five questions above?
This workshop was considered a pilot effort. The members of the Steering Committee hope
that if deemed successful by participants, other similar workshops may be convened in the
Mid-Atlantic area.
DATE AND VENUE
The workshop was a one-day session held on Wednesday, February 9, 2005, in the Academic
and Administrative Building, AAB III, WorWic Community College, Salisbury, MD.
WORKSHOP PRODUCTS
These proceedings of the workshop were assembled, published and distributed by the U.S.
EPA to each participant. Additionally, all presentations made at the conference can be found
on the EPA Web site at www.epa.gov/maia.
Table 1. Steering Committee for the MD-DE Stormwater Workshop
Steering Committee for the MD-DE Stormwater Workshop
Cyrus R. Lesser
MD Dept. of Agriculture
410-841-5870
lessercr@mda.state.md.us
Charlie Wallis
MD Dept. of the
Environment
410-537-3543
cwallis@mde.state.md.us
Roman Jesien
MD Coastal Bays Program
410-213-2297
science@mdcoastalbays.org
Edward A. Lewandowski
DE Center for the Inland
Bays
302-645-7325
director@inlandbays.org
M. Patricia Bradley
EPA Mid-Atlantic Integrated
Assessment Team
410-305-2744
bradley.patricia@epa.gov
William H. Meredith
DE DNR and Environmental
Control
DE Mosquito Control Section
302-739-9917
william.meredith@state.de.us
Frederick W. (Rick) Kutz
410-730-8865
rick.kutz@comcast.net
Lynne Lewis
EPA MAIA Team
410-305-2751
lewis.lynn@epa.gov
Kent Thornton
FTN Associates
501-225-7779
kwt@ftn-assoc.com
Proceedings of the Workshop on Stormwater Management and Mosquito Control
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Stormwater Management and Mosquito Control: A Regional Perspective
Presented by:
Kevin Magerr, USEPA
(Written by: Patricia Bradley, USEPA)
STORMWATER PRIMER
When it rains, or when snow melts, the resulting
water may be absorbed into the ground or it may run
off the land surface into a nearby lake, stream, or
estuary.
Pervious surfaces, such as meadows and woodlands,
absorb and infiltrate rainfall, and generate very little
Stormwater runoff. Impervious surfaces such as
paved streets, driveways, sidewalks, parking lots,
and building rooftops prevent Stormwater from
naturally soaking into the ground. Stormwater runoff
from residential, commercial and industrial sites
picks up fertilizers, dirt, pesticides, oil and grease,
heavy metals, and many other pollutants.
Stormwater runoff is responsible for 21 percent of
impaired lakes and 45 percent of impaired estuaries
in the United States. In the Mid-Atlantic Region
alone, Stormwater is responsible for 5,265 miles of
impaired streams. These impacts are caused not only
by the quality of runoff, but also by its quantity, as
a high volume of flow contributes to erosion and
sedimentation, and impacts aquatic habitats.
CLEAN WATER ACT
In 1948 Congress passed the Federal Water Pollution
Control Act, 33 U.S.C. §§ 1251-1387, commonly
known as the Clean Water Act (CWA). Since 1948,
the original statute has been amended to authorize
additional water quality programs, standards and
procedures to govern allowable discharges, funding
for construction grants and general program funding.
Section 402 of the 1972 amendments established the
National Pollutant Discharge Elimination System
(NPDES) to authorize EPA issuance of discharge
permits (33 U.S.C. 1342).
The CWA was amended in 1987 to require
implementation of a comprehensive national
program for addressing Stormwater discharges. EPA
issued Phase I of the NPDES Stormwater Program
in 1990 requiring NPDES permits for Stormwater
discharges from large municipalities and certain
industrial sources (including construction sites
disturbing at least 5 acres.). Permits from these
sources were required to be submitted beginning
in 1992. EPA issued Phase II of the NPDES
Stormwater Program in 1999 to require NPDES
Stormwater permits from smaller cities and smaller
construction sites and public entities that own or
operate a municipal separate storm sewer system
(MS4).
NPDES is administered through EPA Regions or
state offices within those regions that have been
granted the authority by EPA. Most states have been
delegated authority to run the NPDES permitting
program and issue NPDES Stormwater permits
within their state boundaries. EPA regional offices
still issue NPDES Stormwater permits in nine states/
territories (AK, AZ, DC, ID, MA, ME, NH, NM,
and PR) and on federal facilities or Native American
lands in some delegated states.
EPA REGION 3
The Mid-Atlantic regional office of the U.S.
Environmental Protection Agency, is responsible
for programs in Delaware, Maryland, Pennsylvania,
Virginia, West Virginia and the District of Columbia.
Headquartered in Philadelphia, the region has
field operations and laboratories in Wheeling, WV,
Annapolis and Ft. George G. Meade, MD, and
Pittsburgh, PA.
The Water Protection Division is responsible for the
management and implementation of the Region's
programs to protect, preserve, and enhance water
resources. The Division administers programs
authorized by the Clean Water Act (CWA) and the
Safe Drinking water Act (SDWA). Along with the
administration of programs, the Division assists
the Mid-Atlantic states, localities, and interstate
commissions in developing comprehensive
environmental programs for the achievement of
Proceedings of the Workshop on Stormwater Management and Mosquito Control
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environmental and public health goals and standards,
and oversees delegation of programs and state
implementation of these delegated programs.
EPA Mid-Atlantic delegates the administration
of the NPDES program to the states of Delaware,
Maryland, Pennsylvania, Virginia and West Virginia.
However, EPA administers the NPDES program for
the District of Columbia.
The Office of Watersheds administers the permit
tracking process, while the Office of Compliance
& Enforcement administers the enforcement of
the NPDES Permitting Program. EPA Region 3's
Storm water Web site is:
http://www.epa.gov/reg3wapd/stormwater/index.htm
THE NPDES STORMWATER PROGRAM
Municipal. A municipal separate storm sewer
system (MS4) is a conveyance or system of
conveyances (roads with drainage systems,
municipal streets, catch basins, curbs, gutters,
ditches, man-made channels, storm drains):
• Owned or operated by a state, city, town,
borough, county, parish, district, association,
or other public body (created by or pursuant
to state law) having jurisdiction over disposal
of sewage, industrial wastes, stormwater, or
other wastes, including special districts under
state law such as a sewer district, flood control
district or drainage districts, or similar entity,
or an Indian tribe or an authorized Indian tribal
organization, or a designated and approved
management agency under section 208 of the
Clean Water Act that discharges to waters of
the United States;
• Designed or used for collecting or conveying
stormwater;
• Which is not a combined sewer; and
• Which is not part of a publicly owned
treatment works.
The Stormwater Program for MS4s is designed to
reduce the amount of sediment and pollution that
enters surface and ground water from storm sewer
systems to the maximum extent practicable. Medium
and large MS4 operators are required to submit
comprehensive permit applications and are issued
individual permits. Regulated small MS4 operators
have the option of choosing to be covered by an
individual permit, a general permit or a modification
of an existing Phase I MS4's individual permit.
Industrial Facilities. Operators of industrial
facilities included in one of the 11 categories of
stormwater discharges associated with industrial
activity that discharge or have the potential to
discharge stormwater to a MS4 or directly to waters
of the U.S. must obtain coverage under an NPDES
industrial stormwater permit, unless conditionally
excluded. The 11 categories are:
1. Facilities with Effluent Limitations
2. Manufacturing
3. Mineral, Metal, Oil and Gas
4. Hazardous Waste, Treatment, or Disposal
Facilities
5. Landfills
6. Recycling Facilities
7. Steam Electric Plants
8. Transportation Facilities
9. Treatment Works
10. Construction Activity
11. Light Industrial Activity
Construction. Stormwater runoff from construction
activities can have a significant impact on water
quality. Sediment runoff rates from construction sites
are typically 10 to 20 times greater than those of
agricultural lands, and 1,000 to 2,000 times greater
than those of forested lands. During a short period
of time, construction sites can contribute more
sediment to streams than can be deposited naturally
during several decades. The NPDES Stormwater
program requires operators of construction sites one
acre or larger (including smaller sites that are part
of a larger common plan of development) to obtain
authorization to discharge stormwater under an
NPDES construction stormwater permit.
Stormwater Best Management Practices (BMPs).
There are a wide variety of stormwater BMPs that
industry, municipalities, construction sites and even
homeowners can adopt.
Proceedings of the Workshop on Stormwater Management and Mosquito Control
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Stormwater Ponds. Ponds are designed to
temporarily retain stormwater to keep it from
affecting the quality of streams, lakes, or wetlands.
Nationally there are tens of thousands of stormwater
ponds. These ponds, depending on their design,
serve three main purposes:
1. To capture stormwater to prevent flooding,
2. To detain and slow the rate of runoff to
reduce stream channel erosion and habitat
degradation; and
3. To capture and hold sediment and other
pollutants that are present in runoff.
TYPES OF PONDS
Wet Ponds (Retention ponds).
Wet ponds are stormwater control
structures that provide both retention and
treatment of contaminated stormwater
runoff. A wet pond consists of a permanent
pool of water into which stormwater runoff
is directed. Runoff from each rain event is
detained and treated in the pond until it is
displaced by runoff from the next storm. By
capturing and retaining runoff during storm
events, wet detention ponds control both
stormwater quantity and quality.
Dry Ponds (Detention ponds).
A dry pond is designed to capture and
slowly release runoff water for a period of
72 hours or less after a precipitation event.
Dry ponds do not treat the stormwater and
are typically constructed in areas where
flood control is the greatest concern.
Non-Structural Controls - Infiltration. An
infiltration BMP is designed to capture a volume of
stormwater runoff, retain it and infiltrate that volume
into the ground. There are a variety of infiltration
BMPs, including:
• Rain Gardens. Rain gardens are a way for
homeowners and businesses to reduce polluted
runoff. A rain garden is a shallow, constructed
depression that is planted with deep-rooted
native plants and grasses, and positioned to
receive runoff from impervious surfaces. Rain
gardens slow down the rush of water from
impervious surfaces, hold the water for a short
period of time, and allow it to naturally infiltrate
into the ground.
• Biofiltration. Biofiltration involves treating
stormwater using microbial soil processes,
infiltration, evaporation, and appropriate
plantings. Instead of the typical landscape
islands that are set higher than paved grade (and
which often require supplemental irrigation),
these biofiltration landscape islands are
recessed, and the pavement is graded so that
surface flow is into, rather than away from,
these areas.
• Vegetative Swales. Swales are broad, shallow
channels with a dense stand of fine, close-
growing, water-resistant grass covering the side
slopes and bottom. Swales can be natural or
manmade, and are designed to trap sediments,
promote infiltration, and reduce the flow
velocity of stormwater runoff.
• Reduce Impervious Surfaces. Reducing
impervious surfaces helps minimize water
velocity and runoff. Site design and planning to
reduce impervious surface can help alleviate its
negative effects. Reducing impervious surface
often requires innovative techniques such as:
Narrower Streets. Narrower streets reduce the
amount of impervious surface created by new
residential development, and in turn, reduce the
stormwater runoff and associated pollutant loads.
Currently, many communities require residential
streets that are 32 to 40 feet wide. These wide
streets provide two parking lanes and two moving
lanes. In many residential settings, streets can be
as narrow as 22 to 26 feet wide without sacrificing
emergency access, on-street parking or vehicular and
pedestrian safety. Even narrower access streets or
shared driveways can be used when only a handful
of homes need to be served.
Elimination of Cul-de-Sacs. Cul-de-sacs are local
access streets with a closed circular end that allows
for vehicle turnarounds. Many of these cul-de-sacs
Proceedings of the Workshop on Stormwater Management and Mosquito Control
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can have a radius of more than 40 feet. From a
stormwater perspective, cul-de-sacs create a huge
bulb of impervious surface, increasing the amount
of stormwater runoff. For this reason, reducing the
size of cul-de-sacs through the use of alternative
turnarounds or eliminating them altogether can
reduce the amount of impervious surface created at
a site.
BMP Database. The American Society of Civil
Engineers has developed a comprehensive database
on BMP performance. The project, which began
in 1996 under a cooperative agreement between
the American Society of Civil Engineers (ASCE)
and the U.S. Environmental Protection Agency
(USEPA), now has support and funding from a
broad coalition of partners including the Water
Environment Research Foundation (WERF), ASCE
Environmental and Water Resources Institute
(EWRI), Federal Highway Administration (FHWA)
and the American Public Works Association
(APWA). Wright Water Engineers, Inc., and
GeoSyntec Consultants are the entities maintaining
and operating the database clearinghouse and Web
site, answering questions, conducting analyses of
newly submitted BMP data, conducting updated
performance evaluations of the overall data set,
disseminating project findings, and expanding the
database to include other approaches such as Low
Impact Development techniques. The database itself
is downloadable to any individual or organization
that would like to conduct its own assessments.
On this Web site, you can obtain:
• The minimum protocols for submitting BMP
monitoring studies for inclusion into the
database;
• Guidance for monitoring stormwater BMPs
to meet these protocols;
• Data entry software to store and report BMP
monitoring study data;
• Performance summaries for individual BMPs
through the on-line searchable database
containing roughly 200 BMPs;
• Statistical summaries of the overall BMP
database;
Statistical summaries of performance by
BMP types (e.g., wet ponds);
Technical reports describing the statistical
techniques recommended for analyzing BMP
performance and the results of performance
evaluations;
• Published papers from conference
proceedings and journals on the BMP
database; and other useful information.
The long-term goal of the project is to provide
better understanding of factors influencing BMP
performance and help to promote improvements in
BMP design, selection and implementation. EPA
and ASCE invite organizations that have conducted
BMP performance monitoring to submit their data to
the database and share their findings with the public.
The database Web site is: www.bmpdatabase.org
Recent Concerns Regarding Mosquito
Management
Stormwater management programs always address
public health and safety, largely from the perspective
of flood control and the reduction of waterborne
pathogens. Unfortunately, mosquito management is
often overlooked. Mosquito management is essential
to prevent disease transmission and maintain quality
of life and must be integrated into every stormwater
program.
Stormwater management structures can be a
problem when they hold water long enough to allow
mosquito breeding. Local vector-control agencies
(where they exist) or environmental health programs
should be consulted during preconstruction design
review to ensure that vector breeding habitat is
minimized. These agencies and programs also
should be consulted when developing maintenance
schedules for stormwater management structures.
Even those stormwater facilities that are properly
designed and constructed to minimize mosquito
breeding habitat may collect standing water if
they are not maintained properly, thus creating the
potential for mosquito breeding.
The Mid-Atlantic mosquito season extends from
the vernal equinox past the autumnal equinox
into October. Mosquitoes are true flies and like
other insects have a development cycle involving
Proceedings of the Workshop on Stormwater Management and Mosquito Control
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complete metamorphosis from the egg to the
adult stage. Mosquito eggs are laid singly or in
clusters on water or in mud and debris near water
prone areas. Tiny larvae hatch from the eggs and
develop in the water. The larvae feed on a variety
of microorganisms and organic matter in the water,
and develop through four larval stages to the pupal
stage. Adult mosquitoes emerge from the pupal stage
and fly away. Male mosquitoes feed on nectar and
do not bite for blood; female mosquitoes of most
species require a blood meal to develop their eggs,
and may bite several times during their lifetime.
Female mosquitoes not only bite people, but also
other animals including birds, mammals, frogs, and
snakes.
Mosquito breeding potential depends on the depth
and location of standing water. Ponds that are
uniformly deep, with steep side slopes, resident
populations of larvae-eating fish (particularly
Gambusia minnows), and certain species of aquatic
insects such as dragonfly niads might not produce a
significant number of adult mosquitoes. In contrast,
certain types of stormwater management practices
that are characterized by ephemeral shallow water
habitat and/or dense growth of emergent vegetation
provide excellent mosquito breeding habitat. The
limiting factors are the longevity of the aquatic
habitat, and the duration of the mosquito species' life
cycle (that is, time from egg hatch to emergence of
adult mosquitoes from the water).
Some mosquito species may stay nearby their
breeding areas and travel limited distances, other
species can fly miles from their breeding habitat.
Encephalitis. Encephalitis literally means an
inflammation of the brain, but it usually refers to
brain inflammation caused by a virus. It is a rare
disease that occurs in approximately 0.5 per 100,000
individuals—most commonly in children, the
elderly, and people with weakened immune systems.
Mosquitoes can transmit the viruses for several types
of encephalitis, including West Nile encephalitis,
St. Louis encephalitis, La Crosse encephalitis, and
eastern equine encephalitis.
0 States reporting the presence of West Nile Virus since 1999
^ States reporting human West Nile Virus-related deaths since 2001
O States reporting human cases of St. Louis Encephalitis since 1964
O States reporting human cases of La Crosse Encephalitis since 1964
(Source: mosqurtobuzz.com, modified for B/W printing)
West Nile Encephalitis (WNE). The West
Nile virus (WNV) can cause a West Nile
encephalitis. Although mainly a bird disease,
WNV afflicts horses and humans as well.
With exception of organ transplants or blood
transfusions, WNV is not spread from person
to person, and there is no evidence that a
person can get infected by handling live or
dead infected birds, although handling WNV-
suspect birds while wearing gloves or with
tools is a good precaution. About 80% of the
people who contract WNV have no symptoms;
others get only a mild flu-like illness with
fever, headache, and sore throat. For a small
percentage of people (primarily elderly),
WNV leads to infection of the central nervous
system, resulting in a sudden fever and severe
headache, which can be followed quickly by
seizures and coma; the death rate for patients
who experience this level of infection is about
5-10%.
Since WNV was first isolated in 1937, it has
been known to cause infection and fevers in
humans in Africa, West Asia, and the Middle
East. Human and animal infections were
not documented in the Western Hemisphere
until the 1999 outbreak in the New York City
metropolitan area. Since then, the disease has
spread across the United States. According to
the federal Centers for Disease Control and
Prevention (CDC), in 2003 there were 9,862
Proceedings of the Workshop on Stormwater Management and Mosquito Control
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human cases in 45 states, with 264 deaths.
Mid-Atlantic statistics for 2003 include:
Delaware (17 cases, 2 deaths), Maryland (73
cases, 8 deaths), New Jersey (34 cases, 3
deaths), Pennsylvania (237 cases, 8 deaths),
Virginia (26 cases, 1 death), West Virginia
(2 cases, 0 deaths), and District of Columbia
(3 cases, 0 deaths). In 2004 there were 2,539
human cases in 40 states, with 100 deaths.
Mid-Atlantic statistics for 2004 include:
Maryland (16 cases, 0 deaths), Pennsylvania (5
cases, 2 deaths). Nothing was reported to CDC
for Virginia or West Virginia.
La Crosse Encephalitis (LAC). La Crosse
encephalitis was discovered in La Crosse,
WI in 1963. Since then, the virus has been
identified in several Midwestern and Mid-
Atlantic states. During an average year, about
75 cases of LAC encephalitis are reported to
the CDC. Most cases of LAC encephalitis
occur in children under 16 years of age.
LAC virus is cycled between the daytime-
biting mosquito, Ochlerotatus triseriatus,
and vertebrate amplifier hosts (chipmunks,
tree squirrels) in deciduous forest habitats. If
the female mosquito is infected, she may lay
eggs that carry the virus. People are not an
important part of the life cycle of the virus.
In rare cases, however, people who live in or
visit an area where the virus occurs can be
infected by the bite of an infected mosquito.
After infection, the virus invades the central
nervous system, including the spinal cord and
brain. LAC is usually a mild illness, with fever,
headache, nausea, vomiting, and tiredness.
People with severe disease, primarily children,
can have seizures, coma, paralysis and lasting
brain damage.
Eastern Equine Encephalitis (EEE). Eastern
equine encephalitis is also caused by a virus
transmitted to humans and equines by the bite
of infected mosquitoes that live in marshes and
swamps. Mosquitoes contract the virus by first
feeding on birds. In the Mid-Atlantic region,
salt marsh mosquitoes such as Ochleratatus
sollicitans and freshwater mosquitoes such as
Aedes vexans transmit EEE to humans. As with
WNV, EEE is cycled in reservoir host birds by
Culiseta melanura.ThesQ mosquitoes feed only
on birds, not on humans or other mammals.
The EEE virus escapes from the swamp habitat
in mosquitoes that feed on both birds and
mammals, thus becoming "bridge vectors".
These mosquitoes can transmit the virus to
animals (including horses) and people. EEE is
much more virulent but fortunately much rarer
than WNV. After EEE infection occurs, the
virus often invades the central nervous system,
including the spinal cord and brain. About a
third of EEE patients die from the disease,
with children and the elderly most susceptible.
Of those who survive, many suffer permanent
brain damage and require lifetime institutional
care. EEE virus was first identified in the
1930s and currently occurs in locations along
the Eastern Seaboard, the Gulf Coast and some
Midwestern locations of the United States.
CDC reports about five human cases of EEE
per year in the United States.
St. Louis Encephalitis (SLE). SLE is now the
second most common mosquito-transmitted
human pathogen in the U.S., having been
superceded by WNV. While periodic SLE
epidemics have occurred only in the Midwest
and Southeast, SLE virus is distributed
throughout the lower 48 states. Since 1964,
there have been 4,437 confirmed cases of
SLE with an average of 193 cases per year
(with a range of 4 to 1,967). However, less
than 1% of SLE viral infections are clinically
apparent and the vast majority of infections
remain undiagnosed. Illness ranges in
severity from a simple headache and fever to
meningoencephalitis, with an overall fatality of
5-15 % in patients severely afflicted with SLE.
The disease is generally milder in children than
in adults, but in those children with the virus,
there is a high rate of encephalitis. The elderly
are at highest risk for severe disease and death.
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During the summer season, SLE virus is
maintained in a mosquito-bird-mosquito cycle
(by Culex mosquitoes).
Other Mosquito-Borne Diseases
• Malaria. At one time, malaria (carried by
Anopheles mosquitoes) was common in the
Mid-Atlantic but due to progressive mosquito
control programs and modern medicine, it
has been virtually eradicated in the U.S. and
other developed countries which practice
mosquito control and provide a high standard
of living for their residents. However, malaria
continues to affect hundreds of people in
this country every year. In 2000, health care
workers reported 1,400 cases of malaria to the
CDC. Malaria reported in the U.S. is typically
acquired during trips to malaria-endemic areas
of the world and, therefore, is often called
travelers' or imported malaria. Malaria has
been diagnosed in some U.S. soldiers returning
from Afghanistan. Recently cases have been
reported in Florida, southern California, and
Virginia. In these instances, infected migrant
workers were either directly implicated or
suspected.
• Canine Heartworm. Canine heartworm
disease occurs worldwide in tropical,
subtropical, and some temperate regions.
Until the late 1960s, the disease was restricted
to southern and eastern coastal regions of
the United States. Now, however, cases
have been reported from dogs native to all
50 states. For most of North America, the
danger of infection is greatest during the
summer when temperatures are favorable
for mosquito breeding. In the southern U.S.,
especially the Gulf Coast and Florida, where
mosquitoes are present year-round, the threat
of heartworm disease is constant. Canine
heartworm is common in the Mid-Atlantic and
is transmitted by a variety of Ochlerotatus and
Aedes mosquitoes. The mosquito bites a dog
with heartworm infection, collects some of the
microscopic heartworm offspring and then,
after a couple of weeks, passes these on to
another dog. Prophylactic drugs are available
from veterinarians to prevent dogs from
contracting this disease.
Dengue Fever. Dengue fever is primarily
a disease of the tropics, and the viruses that
cause it are maintained in a cycle that involves
humans and Aedes aegypti, a domestic,
day-biting mosquito that prefers to feed on
humans. Aedes aegypti is now once again
well established in the southern states, from
Texas to South Carolina, and more recently in
Maryland and New Jersey. While dengue fever
is rarely fatal, the symptoms include fever,
painful headaches, eye, joint and muscle pain
and a rash on the arms or legs. From 1977
to 1994, a total of 2,248 suspected cases of
imported dengue were reported in the United
States.
This is a female Aedes aegypti mosquito engorged
with blood while feeding. Dengue viruses are
transmitted during the feeding process.
• Rift Valley Fever (RVF). Rift Valley Fever
is an acute viral disease that causes fever in
domestic animals (such as cattle, buffalo,
sheep, goats, and camels) and humans. The
virus usually lies dormant in the eggs of Aedes
mosquitoes. During heavy rains and floods,
the eggs hatch large numbers of infected
mosquitoes that feed on livestock and spread
the virus. Other species of mosquitoes,
and possibly other biting insects, can also
become infected and spread the disease.
The occurrence of disease in a large number
of domestic animals is referred to as an
"epizootic." The presence of a mosquito-borne
epizootic can lead to an epidemic in humans.
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RVF is more deadly than WNV. RVF has not
occurred in the U.S. (through 2005). However,
there has been concern that it could become
permanently established in the U.S. if it does
enter the country. People with Rift Valley
fever usually have flu-like symptoms but may
develop complications such as kidney or liver
disease. In outbreaks of RVF, the death rate has
been about 15% for those seriously ill.
• Yellow Fever. Yellow fever virus is believed
to have originated in Africa and spread by
trading ships to the New World. During the
1700s and 1880s, yellow fever was one of the
most dreaded diseases in the port cities of the
United States. The last outbreak of yellow
fever in the U.S. occurred in New Orleans and
the Mississippi delta in 1905.
During the 1970s, weakening of Aedes aegypti
control programs allowed reinfestation of this
vector in South America. In 1997-98, a limited
outbreak of yellow fever occurred in Santa
Cruz, Bolivia, which probably represented
the first episode of urban yellow fever in
South America since 1954. The factors that
permitted this outbreak included Aedes aegypti
infestation, low rates of vaccination, and the
proximity of human habitation to areas of
endemic infection. The number of patients
with jungle and urban yellow fever also has
increased markedly in sub-Saharan Africa
since the 1980s. Because Aedes aegypti infests
the southeastern U.S., the possibility exists that
urban yellow fever may return to this country.
Mosquitoes are a part of the ecosystem. Trying
to fully eradicate them would cause adverse
environmental consequences. We can take
steps to limit mosquito habitat, and people
can take steps to reduce their risk of exposure.
If stormwater management systems are well
designed and managed, the risk of mosquito-
borne disease is reduced. However, vigilance is
required.
CURRENT ACTIVITIES
Interpretive Statement on Pesticides and
Water/Proposed Rule. In recent years, courts
have been faced with the question of weather the
Clean Water Act requires an NPDES permit for
pesticide applications (e.g., Headwaters, Inc. v.
Talent Irrigation District). As a result, public health
authorities, natural resource managers, and others
who rely on pesticides, have expressed to EPA their
concern and confusion about whether they have a
legal obligation to obtain an NPDES permit when
pesticides are applied to or over waters of the United
States.
In January 2005, EPA published an interpretive
statement outlining circumstances under which
NPDES permits are not required to apply pesticides
to waters of the United States. The statement
and proposed rule reflect EPA's long-standing
policy that a CWA permit is not required where
application of a particular pesticide to or over
water is consistent with requirements under the
Federal Insecticide, Fungicide, and Rodenticide Act
(FIFRA). Any pesticide that is approved for use in
the U.S. must undergo extensive study and review
to help ensure that, when properly used, it does not
pose unreasonable risk to human health and the
environment. The EPA's Final Rule regarding this
matter is expected to be issued before the end of
2006.
National Management Measures to Control
Nonpoint Source Pollution from Urban Waters
(EPA 841-B-05-004, November 2005). This
guidance helps citizens and municipalities in urban
areas protect bodies of water from polluted runoff
that can result from everyday activities. These
scientifically sound techniques are the best practices
known today. The guidance will also help states to
implement their nonpoint source control programs
and municipalities to implement their Phase II
Stormwater Permit Programs.
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Proceedings of the Workshop on Stormwater Management and Mosquito Control
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EPA Guide for Operating and Maintaining
Stormwater BMP Facilities
This is an upcoming BMP dealing with dry detention
ponds and infiltration systems for stormwater
management, supposedly to be developed during
2006-2007, as opposed to the BMP for wet/retention
ponds (below).
Ponds and Wetlands BMP Maintenance
Guide. The draft "Stormwater Pond and Wetland
Maintenance Guidebook", prepared by the Center
for Watershed Protection for Tetra Tech under a
contract for the U.S. EPA Office of Science and
Technology, is now available for download. The
final version of this BMP is expected to be released
before the end of June 2006; extensive input was
provided to EPA by the American Mosquito Control
Association (AMCA) prior to the final publication
of this document, and mosquito control will be
addressed in these types of BMPs in the future.
This guidebook addresses maintenance through
the lifecycle of a facility, from design to major
repairs. Eight common maintenance concerns are
described in detail including access difficulties
that are commonly encountered by inspectors
or maintenance contractors and a concise list of
pipe failure mechanisms in stormwater ponds and
wetlands.
Designers and plan reviewers will find the Chapter
on "Designing for Low Maintenance Ponds and
Wetlands" to be helpful in understanding the links
between design features and long-term performance.
Those responsible for signing off on the construction
or planning-for-construction inspection can find
highlights on items to keep an eye on during
construction to prevent future problems. The meat
of the guidebook comes as eight profile sheets,
addressing each of the common maintenance
concerns. "Problems to Inspect for" are described
in detail, as are preventative and corrective actions.
Color photographs visually depict the problems
described.
When used by the inspector, program manager,
designer, and owner of stormwater facilities in
NPDES Phase I and II communities, this guidebook
can be a starting place for a stormwater pond and
wetland maintenance program.
You can download the guidebook by visiting
http://www.stormwatercenter.net and clicking on
Program Resources and then STP Maintenance
Resources.
STORMWATER CONTACTS
EPA Headquarters
Jack Faulk 202-564-0768
Rod Frederick 202-566-1197
EPA Region 3
Paula Estornell 215-814-5632
Chad Harsh 215-814-2633
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Stormwater Management Regulations
Overview of Stormwater Management Regulations in Delaware
Presented by:
Randy Greer, Delaware Department of Natural Resources and Environmental Control (DNREC)
The National Pollutant Discharge Elimination
System (NPDES) permit program regulates the
discharge of pollutants to waters of the United
States. The 1987 amendments to the Federal
Clean Water Act added Stormwater to the NPDES
permitting universe. EPA issued regulations in 1990
requiring NPDES permits for Stormwater discharges
from large municipalities and certain industrial
sources (including construction sites disturbing five
acres or more). Permits from these sources were
required to be submitted beginning in 1992. EPA
issued new regulations in 1999 to require NPDES
Stormwater permits from smaller cities and smaller
construction sites.
In the 1970s some of the Mid-Atlantic states
(beginning with Maryland in 1970 and Delaware
in 1979) began to develop state programs in
anticipation of federal regulations. In 1984 Maryland
again led the nation within statewide Stormwater
management laws, and Delaware established a
combination Sediment and Stormwater Law and
Regulations in 1991. The Delaware General Permit
for Construction Activities is the most recent to be
revised in 2004.
Under the current Delaware Sediment and
Stormwater Law and Regulations, all land disturbing
activity over 5,000 ft2 is covered by the regulations.
There are exemptions for:
• Agricultural land management practices
• Emergency projects
• Land disturbing activity less than 5000 ft2
Of late, more agricultural activities are being
included in nutrient management and conservation
plans to provide for increased water quality
protection.
All land disturbing activity over 5,000 ft2 (unless
exempted) must have an approved sediment and
Stormwater plan. The plan must cover:
• Temporary erosion and sediment control
measures that are to be implemented during
construction;
• Construction management measures that will
reduce pollution during construction;
• Post construction Stormwater practices for
water quality and quantity.
The Sediment and Stormwater Program is delegated
throughout the State to eight local program
jurisdictions. These are the agencies that will be
reviewing, approving and inspecting the project.
(NSW Castle County) ( Kent County J f Sussex County J
Local Delegation
of
Program Elements
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Each plan will have a place for the owner/developer
to certify to DNREC or the approval agency that:
• All responsible persons will have attended
DNREC sponsored training;
• All land disturbing activity shall be done
pursuant to the approved plan;
• DNREC and/or their authorized
representatives have the right to enter the site
to inspect the construction for compliance
with the approved plans.
All Erosion and Sediment Control practices must be
designed in accordance with the Delaware Standards
and Specifications for Erosion and Sediment
Control 2003. The Delaware ESC Handbook can
be ordered online from DNREC (www.dnrec. state.
de.us/DNREC2000/Divisions/Soil/Stormwater/
storm water, htm).
The Sediment and Stormwater Regulations require
that all disturbed areas that have not been graded
for a period of 14 calendar days, be temporarily
or permanently stabilized. The regulations require
that grading and construction be accomplished in
grading phases so that no more than 20 acres is
being actively graded at once. This requirement can
be met and the project can move forward by using
temporary stabilization and good sequencing.
The Regulations allow certain projects to have a
standard plan for Erosion and Sediment (E&S). This
would include minor earth disturbance for a single
residential home.
The Regulations allow the requirement (by the
approval agency) of a Certified Construction
Reviewer or CCR to inspect a site. They also require
that all active construction sites are inspected and
that inspection reports be written and distributed to
the parties involved. Onsite personnel should also
inspect the E&S measures on a weekly basis and
after each rainfall event. There are provisions for
enforcement and penalties for noncompliance with
the provisions of the Sediment and Stormwater Law
and Regulations.
WhatisaTMDL?
TMDL stands for Total Maximum
Daily Load.
The TMDL represents the
maximum amount of a pollutant
allowed to enter a waterbody by
law so that the waterbody will meet
and continue to meet the water
quality standards for that particular
pollutant.
Pollutants are anything that
prevents a waterbody from attaining
the national goal of being "fishable
and swimmable."
Common pollutants include
sediment metals (often from
mining activities), toxic chemicals,
fecal coliform bacteria, pH, and
excessive nutrients.
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Proceedings of the Workshop on Stormwater Management and Mosquito Control
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Stormwater Management in Maryland - A Regulatory Overview
Presented by:
Charlie Wallis, Maryland Department of the Environment (MDE)
Clearly, any standing water has the potential to
promote mosquito growth. Some Stormwater
management practices use ponded water to promote
water quality improvement. Therefore, there is the
potential for contributing to mosquito problems.
However, Stormwater management is essential to
mitigate the adverse effects of development on
the environment. These effects include increased
flooding, water quality impairment, reduced
groundwater recharge, and stream channel erosion.
Streams are Eroded by High Volumes & Flows
Maintenance of constructed facilities is of
paramount importance to their function. The state
and local governments make efforts to inspect
both publicly and privately owned Stormwater
management facilities. These efforts can certainly
improve. A greater public awareness of the value
of these facilities will help in making increased
funding available so that better maintenance can be
achieved. Alack of maintenance typically results in
diminished pond performance, poor drainage, and
promotes mosquito population growth. Temporary
sediment and erosion control measures employed
during construction also benefit from increased
maintenance activity.
The state of Maryland revised its Stormwater
management regulations in 2000. Included in the
revisions were changes in design requirements that
reduce the potential for mosquito breeding. Specific
changes include:
Greater flexibility of practice selection based
on site specific conditions. Previously, certain
practices were required because it was believed
they would provide the greatest improvement to
water quality. Over time it became evident that site
conditions had a significant influence on practice
performance. Forcing a specific practice to be used
where it was impractical often led to poor drainage
and eventually failure. Using the appropriate
practice will result in less frequent occurrences of
poor drainage and stagnant water.
Improved drainage performance. Not all
Stormwater management practices require extended
ponding of water. Any practice that is not designed
with a permanent pool is required to drain within 48
hours after a storm event. If a practice does involve
longer retention times, then features are to be
incorporated to promote mixing of incoming runoff
and reduce stagnation.
Improving the design of permanent pools.
Research clearly shows that varying the depths of
permanent pools reduces mosquito breeding habitat.
Portions of all new ponds have to be a minimum
of 4 feet deep. Other areas of ponds that have
varying shallower depths are to be planted with
aquatic vegetation. This results in habitat for natural
predators of mosquitoes such as dragonflies, birds,
fish, and frogs.
Encouraging better site design practices that
reduce the need for structural Stormwater
management features. Development alters natural
drainage and creates the need for Stormwater
Proceedings of the Workshop on Stormwater Management and Mosquito Control
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management. Following new design criteria
minimizes the generation of pollutants and
reduces the concentration of runoff. Following
the nonstructural measures promoted by the State
in some cases can eliminate the need for a pond
altogether.
Considerable development is occurring on the lower
Eastern Shore of Maryland. Development leads
to negative impacts on the land and environment,
including increased flooding, pollution, stream
channel erosion, and degradation of aquatic life.
Stormwater management attempts to mitigate these
negative effects.
Stormwater management practices can vary widely
between jurisdictions. The factors that can affect
Stormwater management practices include:
Property Rights. Public statements often
do not reflect an understanding of the land
development process. If a site is developed,
then its' Stormwater impacts must be addressed
on site, prior to the runoff leaving the site. A
developer cannot flood a downstream property
owner. Typically a developer plans Stormwater
management to maximize sellable lots rather than
minimize environmental impacts.
iO»0 M4RVLAVD.,
STORMWATER DjglCNf
Federal Clean Water
Act. National Pollutant
Discharge Elimination
System (NPDES)
regulates point
discharges at the end
of a pipe. Originally
applied to industrial and
wastewater treatment
plants, the definition
has been expanded
to include municipal
storm sewer systems.
Maximum Extent Practicable - The standard that
Stormwater management practices are supposed
to meet. Municipal NPDES has wide applicability
in Maryland. A large database of Stormwater
MM:
information exists, and efforts are underway to
make this information more accessible.
Maryland's Stormwater Management Program.
Its authority is in State law and regulation.
Hurricane Agnes in 1972 caused widespread
destruction and provided the impetus for the laws
that created Maryland's Stormwater Management
Program, which was up and running by 1984.
Local government has authority except for state
and federal projects. The State reviews local
programs for conformance with state regulations
and provides technical advice. Maryland revised
its regulations in 2000 including the introduction
of a Design Manual. Anecdotally, Hurricane
Floyd in 1999 exceeded the 100 year rainfall in
many locations in the State, yet major flooding
was limited to the Northeast watershed. Hopefully
the Stormwater Management Program is
beginning to provide a benefit.
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Proceedings of the Workshop on Stormwater Management and Mosquito Control
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Mosquito Production Considerations
A National Perspective
Presented by:
Joe Conlon, American Mosquito Control Association (AMCA)
The introduction and spread of West Nile Virus
in the U.S. has reawakened an appreciation of
mosquitoes as vectors of diseases. I use the term
"reawakened" advisedly, for mosquito-borne
diseases were once quite prevalent in the U.S. and,
indeed, played a major part in shaping our nation's
destiny. These diseases no longer claim victims in
the U.S. as a matter of course largely due to the
exemplary efforts of organized mosquito control
agencies, in conjunction with an enlightened and
effective public health infrastructure.
Basi
As early as 1905, mosquito control pioneers
recognized the value of a diversified approach by
integrating surveillance, source reduction, personal
protection, and chemical and biological control.
Early control methods consisted of ditching,
draining, and/or filling marshes, applying oils to
water to kill immature mosquitoes, and insecticide
sprays against adults. The first districts were
established in New Jersey in 1912. California and
Florida followed suit in 1915 and 1925, respectively.
In the ensuing years, mosquito control districts
and state agencies were established nationwide.
Mosquito control personnel refined their methods
through applied research and assisted federal and
state agencies in developing certification criteria to
ensure conformance to stringent safety standards.
Vector control programs continue to progressively
adopt the use of integrated mosquito management
methods. These strategies, endorsed by the CDC
and EPA, are comprehensive and specifically
tailored to safely counter each stage of the mosquito
life cycle. Control of immature stages through
water management and source reduction, where
compatible with other land management uses, is a
linchpin of this strategy.
Mosquito Life Cycle
'^KAduIt
Larva
v
Each of the 176 species of mosquitoes currently
recognized in the U.S. utilizes preferred aquatic
habitats for breeding. These habitats vary widely,
from salt marshes to scrap car tires. Virtually any
collection of stagnant water is fair game, with some
species successfully utilizing even soda bottle caps.
Factors favoring choice of breeding habitat depend
upon the mosquito species involved. Many types of
stormwater management systems provide standing
water habitats suitable for mosquito development,
particularly retention ponds, bioretention basins, and
a variety of above and below-ground devices that
incorporate sumps, vaults or catch basins.
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Mosquito breeding associated with wetland
habitats and flood-control devices is coming under
increasing scrutiny by the scientific community. A
landmark study conducted (between 1999-2001)
by the California Department of Health Services
Vector-borne Disease Section identified at least five
separate mosquito genera utilizing BMPs nationwide
for breeding. Of the 72 agencies that participated
in this study, 86% reported mosquitoes breeding
in local BMPs. Ominously, several putative vector
species of West Nile virus and other encephalitides
were strongly associated with poorly maintained
BMPs (Metzger et al. 2002). This corroborates
data from a 1993 Florida study that reported 180
out of 238 (76%) stormwater systems surveyed
for breeding were mosquito productive (Santana
et al. 1994) in addition to a 1988 Maryland study
that reported approximately 50% of dry and wet
stormwater ponds located in housing and industrial
developments breeding mosquitoes (Dorothy and
Staker 1990). The proximity of urban and peri-urban
BMPs breeding large numbers of vector mosquitoes
to large human populations is of concern to
mosquito control personnel because it substantially
increases the probability of disease transmission to
humans, including West Nile virus.
Mosquito Larval Habitats
Temporary Pools
Freshwater Ochlerotatus dorsalis, Aedes vexans
Psorophora confinnis & ciliata
Brackish Oc. sollicitans & taeniorhynchus
Permanent Pools
Polluted Culex tarsalis, salinarius & pipiens
Clean Anopheles spp.
Culiseta melanura
Coquillettidia perturbans
Safe and adequate access to stormwater management
systems is a crucial program element and should
be considered in all phases of design, construction,
and in the operations and maintenance plan.
Designs that provide reductions in maintenance
requirements are crucial for agencies with limited
manpower resources. However, all systems require
regular maintenance to ensure optimal performance
and mosquito suppression. This also comes at a
significant cost to agencies.
Even well-designed and maintained systems will
require programmed corrective mosquito control
efforts to address mosquito populations escaping
natural predation in retention ponds, etc. Failure to
consider the full inventory of remedial larvicidal
measures, where indicated, to control immature
mosquitoes in their aquatic stages will have
the perverse effect of increasing reliance upon
adulticides to control adult mosquitoes following
their emergence and widespread dispersal.
Provisions of the CWA mandating measures to
reduce pollution through the use of stormwater
management systems provide both significant
challenges and opportunities to those charged with
protecting the public's health. A proactive rather than
reactive approach to addressing issues can mitigate
their untoward effects. Thus, communication
between those charged with stormwater management
and public health agencies at every level and step
in the process can produce results satisfactory to
the interests of both parties and, most importantly,
the public that they both serve. Partnerships are
needed to promote responsible stewardship of water
resources. Active collaboration and funding on site
surveys, design, construction, maintenance and
operations protocols for stormwater management
systems will promote and maintain a balance
between water quality improvement and vector
control-they are not mutually exclusive.
The continued increase in worldwide tourism and
trade virtually guarantees further challenges from
exotic diseases requiring ready control expertise
to prevent their establishment and spread. Should
these emerging mosquito-borne diseases of man
and animals settle into the American public
health landscape, particularly as an unintended
consequence of otherwise laudatory environmental
policy initiatives, we will have only ourselves
to blame, for we have the means to control these
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Proceedings of the Workshop on Stormwater Management and Mosquito Control
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diseases within our grasp. A robust inter-agency
cooperation in the design and implementation of
stormwater management programs is a cornerstone
of this national effort. We must remain prepared to
accept and meet these challenges - our citizens and
our nation's wildlife deserve no less.
Future threats
Rift Valley Fever
Japanese Encephalitis
Murray Valley Encephalitis
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Stormwater Management Areas as Mosquito Larvae Habitat in the State of Maryland
Presented by:
Cyrus R. Lesser and Jeannine Dorothy, Maryland Department of Agriculture
Early
80s
1988-
1989
2000
' Maryland adopted ^™ Maryland Dept of Agriculture first conducted
stormwater quality surveillance of Stormwater management
regulations sites as habitat for mosquito larvae (Howard,
Montgomery & Prince George's counties)
Maryland revised their
stormwater management
regulations,allowing and
promoting more sophisticated
design of stormwater facilities.
Mosquito control is provided throughout Maryland
by public agencies. The Maryland Department of
Agriculture provides direct service in the City of
Baltimore and 19 of Maryland's 23 counties. In
Calvert, Caroline and Queen Anne's Counties,
mosquito control is provided by county government.
Participation in the mosquito control program
is voluntary and at the discretion of community
associations, towns and residential groups.
Participation in the mosquito control program
is greatest in the coastal plain of Maryland and
in the metropolitan area between Baltimore and
Washington, D.C.
The state of Maryland adopted stormwater quality
regulations in the early 1980s and was one of the
first states to do so. State regulations follow federal
regulations and are contained in Title 4, Subtitle 2
of the Environment Article of the Annotated Code
of Maryland. The regulations are promulgated by
the Maryland Department of the Environment and
administered by counties and municipalities. These
regulations are designed to protect the waters of
the State from adverse effects of stormwater runoff
from areas developed for residential, industrial and
business uses. Both federal and state stormwater
regulations fail to adequately address public health
concerns related to mosquitoes and mosquito-borne
disease.
The Maryland Department of Agriculture first
conducted surveillance of stormwater management
sites as habitat for mosquito larvae during 1988-
1989. The initial survey was conducted in Howard,
Montgomery and Prince George's Counties. In that
era of stormwater design, diversity of management
options was generally limited to permanently wet
'retention' basins and temporarily wet 'detention'
basins. The survey in the late 1980s monitored 139
sites and found that mosquito production in both
retention and detention basins were approximately
the same. Subsequent evaluation discovered that
retention basins provide excellent habitat for
Gambusia holbrooki (mosquitofish) and a stocking
program of these fish to permanently wet basins
alleviated the mosquito breeding problem. Mosquito
breeding in temporarily wet detention basins was
managed by use of pesticides to control mosquito
larvae because the sites were not suitable for the
stocking of mosquitofish.
In 2000, stormwater management regulations in
Maryland were revised, allowing and promoting
more sophisticated design of stormwater facilities.
The construction of permanently wet retention
basins declined and the construction of stormwater
wetlands, infiltration practices, filtering practices
and non-structural practices increased following the
2000 revision of regulations. The current designs of
stormwater management facilities in Maryland are
frequently conducive to mosquito breeding because
they promote shallow water detention. Surveys by
MDA entomologists have found that stormwater
wetlands, bioswales, infiltration trenches, infiltration
basins, filtering practices and vegetated open
channels that capture and detain runoff provide
good habitat requirements for mosquito larvae and
do not provide habitat for sustainable populations
Proceedings of the Workshop on Stormwater Management and Mosquito Control
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of predators; or if predator habitat is available,
access to mosquito breeding habitat is restricted.
The mosquito breeding problem in stormwater sites
is caused by design criteria, lack of maintenance, or
a combination of the two. Because they are located
within or adjacent to residential areas, business
locations and schools, mosquitoes produced in
stormwater sites have a disproportionately large
impact on human populations.
Design Criteria
Lack of Maintenance
Proximity to Human Population
Lack of Central Tracking Mechanism
Ineffective Inspection and Maintenance
Confusion over Ownership
Other issues impacting mosquito management in
stormwater sites in Maryland include a lack of
an effective central tracking mechanism to locate
and enumerate stormwater facilities, ineffective
inspection and maintenance of existing sites, and
confusion about ownership of the sites. The state
provides oversight on these issues, but it is the
responsibility of local jurisdictions to administer
the actual permitting and review of stormwater
facilities construction. Few counties have the
resources to provide real time tracking of site
locations or provide regular monitoring of sites to
determine the need for maintenance. These issues
vary by jurisdiction, but in general counties are
hard pressed to meet the unfunded state mandate
regarding stormwater management. In many
Maryland jurisdictions, the legal ownership of a
stormwater facility is transferred from a developer to
the local community association and responsibilities
for maintenance, etc., are also transferred to the
community. Often, the stormwater regulations
are poorly understood, if known at all, by the
community group.
Mosquito management must be given greater
attention and consideration in the planning, design
and operational phases of stormwater facilities in
Maryland. Federal and state regulations should
be reviewed and amended to include mosquito
control and public health considerations of
stormwater management. A centralized database of
stormwater facilities should be kept by the Maryland
Department of the Environment. This should include
information on the exact location and design type
of each site, as well as the maintenance history and
these data should be readily available to mosquito
control managers at the State and County levels.
Centralized Database of Stormwater
Facilities
location of facility design
maintenance history owner
22
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Stormwater Management Structures and Mosquito Production in Calvert County, MD
Presented by:
V.Wilson Freeland, Calvert County Mosquito Control Program
Calvert County is located in southern
Maryland, bordering the Patuxent River and
Chesapeake Bay. It has a landmass of about
217 square miles and contains over 100 miles
of shoreline. Calvert is the smallest of the Maryland
counties but ranks second in population growth.
Calvert is currently home to more than eight hundred
(800) Stormwater Management Structures.
Historically, the primary mosquito species found in
the county have been salt marsh mosquitoes; this
trend is changing. We are now seeing increases in
floodwater and permanent water species, specifically
Culex restuans, salinarius and Aedes vexans.
While Stormwater management structures cannot
be considered as the sole source of the mosquito
population affecting this trend, they are certainly
contributing factors. The issues with Stormwater
management structures, from a mosquito control
viewpoint, lie mainly with their design and
maintenance. Retention, detention and bio-retention
structures require considerable man-hours to survey,
document and, when required, treat. Bio-retention
structures are fairly new designs that create the
most problems in regard to mosquito production.
These structures appear designed to mimic natural
wetlands. Their water depth is very shallow when
filled and the structure is planted with wetland
vegetation. Large broods of Aedes vexans are
commonplace when the structures fail to dry in
seven days or less. The habitat is usually void of
natural predators and, when predator populations
are present, their numbers lag well behind mosquito
larvae development.
Detention structures that function properly will
not produce mosquitoes. However, without annual
maintenance, most begin holding water much
longer and become ideal habitat for the previously
mentioned species. Detention structures are designed
to allow Stormwater to slowly percolate into the
Calvert / !
County"*>*,
ground water or are designed with a weep structure
that slowly releases water from the structures
discharge. When the bottoms of these detention
structures become covered with silt or vegetation,
the percolation process is severely restricted and
these detention structures begin acting as retention
structures.
Retention structures can produce large populations
of Culex restuans and Anopheles quadramaculatus.
Most of these structures will hold water indefinitely
and can be stocked with fish that provide excellent
biological control. Unfortunately there are retention
structures that become dry enough not to support
fish. These structures need to be restocked or
chemically treated to control mosquitoes throughout
the season.
The maintenance of the structure is critical to
its function and to its efficiency in producing
mosquitoes. Maintenance issues arise when, in most
cases, the developer of the property transfers the
land to the community association or, in some cases,
to an individual owner. In both circumstances the
new property owner is usually completely unaware
of their responsibilities to maintain the Stormwater
structure.
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In Calvert County the inspection of stormwater
structures is delegated to the Department of Public
Works. Three full time Erosion and Sediment
Control Inspectors, as a part of their duties, carry
out inspections at one year, three year, six year and
twelve year intervals. Maintenance requirements
can include removing trees and shrubs from the
dikes of the structure, cleaning the out flows of
debris, and removing sediment from the basin of the
structure. In some cases maintenance costs can be
considerable, and the new property owner finds that
they must bare these costs alone.
24 Proceedings of the Workshop on Stormwater Management and Mosquito Control
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Mosquito Production Issues in Delaware's Stormwater Management Basins
Presented by:
William Meredith, Thomas Moran, and Darin Callaway, DNREC
We like SWMBs, but mosquitoes do too. The
Delaware Mosquito Control Section, being an
integral part of the State's fish-and-wildlife
management agency, strongly supports the use of
Stormwater management basins (SWMBs) for their
water quality improvement benefits and for whatever
wildlife habitats they might provide. Because of
these environmental benefits, statutes, regulations
and policies have been implemented at federal, state,
county and municipal levels that mandate the use of
SWMBs and other types of BMPs to help improve
the water quality of surface runoff. The Section
knows that not every SWMB is a problematic
producer of mosquitoes; but unfortunately many
are, and the trick is recognize which ones produce
excessive amounts of mosquitoes and to act upon
such knowledge. We also know that the relative
contribution of any individual SWMB to local
mosquito problems is dependent upon other sources
of mosquitoes too, from either natural or other man-
made sources, and originating from nearby or remote
locations. In some areas a SWMB might be solely
responsible or highly contributory to local problems;
in other areas, a SWMB's contribution might be nil
or very minor. We often receive alarmed calls from
the public or their elected officials about actual or
potential mosquito production problems emanating
from individual SWMBs, especially now with the
public's concern for transmission of West Nile virus.
We tell callers that indeed there could be a problem
but that the sky is not falling, not to worry, and we
will take control actions as warranted.
The challenges we face. Delaware has plenty of
natural mosquito production habitats in that about
8% of the state's surface area is tidal wetlands and
another 10% is some type of freshwater wetlands.
All kinds of wetlands can produce excessive
amounts of mosquitoes, including natural, "healthy"
wetlands, whether they are salt marshes, freshwater
marshes, forested swamps, woodland pools or
Coastal Plain ponds. Degraded wetlands will also
cause mosquito production problems, whether
these wetlands have been altered by hydrological
modifications, sedimentation, filling, pollution
runoff or other factors—often the mosquito
production in these degraded areas is worse than
in "healthy" wetlands, and sometimes not. Man-
made wetlands can also produce excessive amount
of mosquitoes, including SWMBs and constructed
mitigation wetlands (e.g., highway wetlands
compensation projects); man-made containers of
all sizes and configurations can hold water that
(function as wetlands environments) and provide
mosquito breeding habitat. These natural habitats
whether "healthy" or degraded, in combination
with man-made sources, produce 57 species of
mosquitoes in Delaware, of which 19 will bite
humans, and 17 are of concern for transmission of
mosquito-borne diseases. As such, we have plenty of
control challenges to address, which in part now also
include trying to deal with more than 1500 SWMBs
scattered around the state (with about two-thirds
of these SWMBs in New Castle County and the
remaining one-third in Kent and Sussex Counties).
Species of concern for breeding in SWMBs include
Culexpipiens, Cx. salinarius, Cx. restuam, Aedes
vexans, Ochlerotatusjaponicus, and Coquilletidia
perturbans, having both quality-of-life (nuisance)
and disease vector concerns. Other mosquito species
of concern also breed in SWMBs, and the extent
of their contributions to the overall problem needs
more study.
Are natural predators enough? Mosquitoes have
many types of natural predators, preying upon both
larval immature mosquitoes (e.g., dragonfly naiads,
water boatmen, backswimmers, predacious diving
beetles, water striders, salamander larvae, native
fishes) and adult mosquitoes (e.g., dragonflies,
Proceedings of the Workshop on Stormwater Management and Mosquito Control
25
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purple martins, swallows, bats). However, it is a
fallacy to think that natural predators are enough
to keep mosquito populations at levels expected
and demanded by modern society. Even natural
populations of predators living in balanced,
"healthy" wetlands may not provide sufficient
control. The situation often becomes worse (in
degraded wetlands) where predators might be scarce
or absent. Mosquitoes have evolved to be able to
"outrun" their natural predators at the population
level by being chronically present in intolerable
numbers or having horrendous, sporadic population
eruptions. This is why modern-day mosquito control
programs are in business: Quite simply, we're doing
what Mother Nature can't do!
How do we control mosquitoes? The Delaware
Mosquito Control Section, like all modern-day
mosquito control programs, uses an Integrated Pest
Management (IPM) approach, where surveillance
and monitoring of mosquito populations and the
diseases they carry is key. When control actions
are needed, we always prefer non-chemical,
source reduction measures. In salt marshes this
might involve the selective installation of shallow
ponds and ditches known as Open Marsh Water
Management (OMWM), done to eliminate mosquito
egg-deposition and larval rearing habitats and
to encourage predation on mosquito larvae by
native fishes. Around residences or businesses,
we encourage good water sanitation practices by
property owners in order to remove standing water
habitats that can breed mosquitoes. For SWMBs,
we want to encourage (to the extent practicable)
basin engineering designs, water and vegetation
management practices, and good maintenance
practices to help lower or eliminate mosquito
breeding. In some situations it is possible to help
control mosquitoes by introducing larval-consuming
fishes (e.g., Gambusia stocking), but for several
environmental and practicable reasons this has only
limited utility.
The role of insecticides. As part of the IPM
approach, when source reduction measures either
fail or cannot be employed, then it is necessary
to use chemical controls, either larvicides or
adulticides. Our preference is to use larvicides first
(e.g., Bti, methoprene, temephos), since applications
of larvicides are more localized and results in
less exposure to humans. Adulticides (e.g., naled,
malathion, permethrin, resmethrin, sumithrin) are
tools of last resort, but because of the challenges via
other means, it is often necessary to use adulticides.
Spray applications are typically more widespread
due to the dispersed nature of adult mosquitoes;
hence, there is more exposure to humans. But no
matter what type of chemical controls we might
have to use, the U.S. Environmental Protection
Agency (EPA) has scientifically determined that
EPA-registered mosquito control insecticides,
when applied in accordance with all product label
requirements and conditions, "pose no unreasonable
risk to human health, wildlife or the environment."
Needed thinking and actions. The Delaware
Mosquito Control Section has three hopes for the
outcome of this Storm water Management and
Mosquito Control Workshop, involving some new
thinking by several parties and taking actions where
possible:
1. Realistic recognition by all parties that
SWMBs can often cause mosquito
production problems (i.e., do not take a
"head-in-the-sand" approach that this is not
true);
2. To the extent practicable, implement
source reduction practices in design and
management of SWMBs to reduce mosquito
production, without unduly compromising
important values and functions of SWMBs
for good water quality and wildlife habitats;
3. For whatever excessive mosquito production
in SWMBs that cannot be controlled by
source reduction, recognize the need to
treat such SWMBs with larvicides. Do not
bemoan our having to use chemical controls,
which many "environmentalists" are often
prone to do in almost knee-jerk manner. In
26
Proceedings of the Workshop on Stormwater Management and Mosquito Control
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Try not to build this! Based upon our Delaware experience and observations
in the field, what we believe would constitute a blueprint or recipe in SWMBs to
create "mosquito-breeding heaven" would have the following features - obviously,
any steps that could be taken to reduce or eliminate such features, without unduly
compromising the primary environmental goals and functions of SWMBs, we
encourage to be taken. Here is a listing of some "nasty" features to help build
mosquito-friendly environs - don't do this!
• Have uniformly shallow water
depths throughout a basin,
without deeper reservoirs
for predator survival during
droughts, drawdowns, or times
of poor water quality.
• Have shallow, gently sloping
sides along basin margins.
• Have the entire basin
periodically dry-out and then
reflood to hold water for >5
consecutive days.
• Have water levels along basin
margins fluctuate to cause
wet-dry-wet conditions in
isolated edge pockets.
• Have basin choked with
emergent or floating
vegetation.
• Have lots of organic
material get into the basin
(e.g., grass clippings).
• Have little water flow
or changeover of basin
waters, creating stagnant
conditions.
• Locate these SWMBs
among or nearby where
people live (where they
unfortunately often must
be located for their primary
water quality functions!).
many locations or situations, the need to
use larvicides might well be the reality, an
unavoidable aspect or cost of creating and
using SWMBs.
Case examples in Delaware. In trying to "bring
home" these problems (through photographed case
studies), we present (to the Workshop's audience)
several examples of types and extent of mosquito
production problems in SWMBs and types of
control actions to implement. Historically, the most
use of SWMBs has been in heavily populated and
urbanized areas of northern New Castle County
above the C&D Canal, and indeed there might now
be more than 1000 SWMBs in this area, with many
of these basins continuing to present problems.
However, the burgeoning growth of this County
south of the Canal, with subdivisions seemingly
popping up everywhere, has also led to a spread of
SWMBs into areas where the demand for mosquito
control was historically low. There are of course
many natural sources of mosquito production also
at play here. In downstate Delaware, particularly in
eastern Sussex County where human populations
are booming due to the coastal resort (beach)
economy and retirement relocations, the recent
proliferation of SWMBs is also quite daunting
to our control program. If there is one theme that
we want to convey in these case examples, it is
that wherever basin engineering designs, water
and vegetation management practices, and good
attention to necessary maintenance and upkeep of
SWMBs can be accommodated or undertaken to
reduce or eliminate mosquito breeding, we implore
our stormwater management and water quality
colleagues to do so. Given the nature and perhaps
conflicting goals of some of these SWMBs in
relation to mosquito production and control, by no
Proceedings of the Workshop on Stormwater Management and Mosquito Control
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means are we saying that such new measures will
fully eliminate the necessity for mosquito control
programs to inspect SWMBs and to treat them as
warranted; rather, whatever you can do here to help
the cause, please do so!
Scientific survey. While the Mosquito Control
Section has generated operational information in
regard to many of the SWMBs causing us problems,
until recently we have not had the luxury or
resources for undertaking a systematic, large-scale,
scientific look at the situation. In large measure this
has now been remedied by completion of a two-year
scientific survey of mosquito production in SWMBs,
contractually performed in the summers of 2003 and
2004 by Dr. John Gingrich (Dept. of Entomology
and Wildlife Ecology, University of Delaware).
This study systematically and repetitively examines
over 90 sites around the State representing a
variety of SWMB habitats, plus several constructed
wetland mitigation sites associated with highway
development projects. Dr. Gingrich's findings report
upon the species and extent of mosquito production
found in these systems relative to a basin's physical
and biotic features. The Mosquito Control Section
initiated this project, helped design the sampling
strategy, and provided the funding to carry it out. Dr.
Gingrich's findings were reported at the Workshop
and are found elsewhere in these Proceedings.
For further information, please contact: William
H. Meredith, Mosquito Control Section, Division
of Fish and Wildlife, DNREC, 89 Kings Highway,
Dover, DE 19901. Phone: 302-739-9917. Email:
William.Meredith@state.de.us.
28 Proceedings of the Workshop on Stormwater Management and Mosquito Control
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Predictors of Mosquito Abundance in Stormwater Ponds in Delaware
Presented by:
Jack Gingrich, Department of Entomology and Wildlife Conservation, University of Delaware
Our primary objective was to evaluate the
relationship between different types of BMPs/
wetlands, mosquito species, and their abundance
in four different pond types: a) retention ponds;
b) detention ponds; c) CREP ponds; and d)
constructed wetlands. Ancillary objectives included:
1) Determining the physical and biological
attributes of good and poor mosquito habitats
among the various types of Stormwater catchments;
2) determining biotic factors that might influence
mosquito abundance; 3) where vector species occur,
determining the species associations present; and
4) establishing the relationship between various
water quality factors and mosquito abundance.
Ultimately, we sought to find predictors of mosquito
abundance in these Stormwater ponds.
There are seasonal differences in larval mosquito
abundance in Stormwater ponds. Abundance is
generally much elevated in August and September.
Among the various pond types, detention ponds
are generally much better producers of mosquitoes
than other pond types, including retention ponds,
wetlands, and usually, CREP ponds. Shallow
retention ponds are more apt to have abundant
mosquito subsites than steep ponds. Partially
or fully shaded ponds are also more likely to
exhibit an abundance of mosquitoes. Invertebrate
predator numbers are inversely correlated with
mosquito abundance. Water quality factors are
difficult to quantify with respect to mosquito
abundance, and statistical analyses at this date are
incomplete. Nevertheless, orthophosphate appears
to be positively correlated with overall mosquito
abundance, while chloride ion presence appears to
be inversely correlated.
Seasonal Mosquito Distribution, All Ponds
With respect to vector species of concern, Culex
pipiens, Cx. salinarius, Cx. restuans, Aedes vexans,
and Ochlerotatus sollictans appeared to have
some associations with specific vegetation groups,
including grasses, Ludwigia, duckweed, sedges,
Phragmites, and rushes, depending upon species.
Overall, ponds that are heavily vegetated around
the periphery appear to have abundant mosquito
activity. However, there were no statistically
significant associations. Concerning mosquito-
mosquito associations, Culex pipiens was very often
associated with Cx. salinarius, while Ae. vexans was
sometimes associated with Oc. sollicitans.
Relationships between Mosquito
Species and Vegetation
Association
Two variables that are related.
Association does not imply causation.
Correlation
A measure of the linear
relationship between two variables.
Cx. salinarius appears to be associated with
duckweed and phragmites, but correlated with
Cx. pipiens in early season only
Cx. pipiens associated with Ludwigia, grasses,
loosestrife, correlated with Cx. salinarius
Oc. sollicitans is associated with rushes and Ae.
vexans, but not correlated
Ae. vexans is associated with sedges and but
not correlated
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Even though mean mosquito abundance per dip
may sometimes appear to be low, this is often
misleading; sites with low abundance or even zeroes
drag down the overall means, as do seasonal periods
of low abundance. From an operational standpoint,
there were many times and sublocations where the
abundance was high enough (> 10 per dip) to have
triggered operational measures.
Preliminary Predictors of High Mosquito
Producing Ponds
Ponds with shallow, heavily vegetated edges
Shaded or partially shaded ponds
Low predator numbers
Possible Associations—if vegetation is
skewed towards grasses, sedges, algae,
duckweed, loosestrife, Alisma, Phragmites
High phosphate content—no stats, but likely
association
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Wildlife Habitat Considerations
Ecosystem and Wildlife Habitat Considerations in Stormwater Management
Presented by:
Roger Tankersley, Jr and Mark H. Wolfe, Tennessee Valley Authority
Stormwater management is progressively a
concern for states, municipalities, and water
control districts as well as for the industries,
businesses, and developments that occur within
those jurisdictions. Incorporating wetland habitats
into passive Stormwater management design can
increase the overall benefit of Stormwater treatment
plans, provide key habitats in areas that are usually
habitat deficient, and provide opportunities for
public education on wetland issues. We present
many of the important concepts and issues related to
successful integration of wildlife habitat into passive
Stormwater control.
Key to successful integration of wildlife habitat is
an understanding of the types of wetland habitats
located in your region. The Hydrogeomorphic
Classification of Wetlands (Brinson 1993) is an
excellent way to assess what plants and animals may
occur in your area, and to understand the moisture
regime they require for year-round survival.
Hydrogeomorphic classification incorporates the
geomorphic setting (landform shape, topographic
position), water source, and hydrodynamics (energy
level and direction of water flow) into a succinct
description of wetland type. The key advantage for
constructed wetlands is that these factors can be
assessed before construction, and similar wetlands
can be visited to identify target plants that should be
used to mimic natural wetlands.
Most Stormwater wetlands are small and isolated. To
maximize the benefit of establishing wildlife habitat,
planners should consider the regional landscape
configuration of existing wetlands and attempt
to locate constructed wetlands nearby. Existing
wetland location and size can be assessed using the
National Wetlands Inventory (NWI, http://wetlands.
fws.gov). On larger construction sites, this regional
consideration may mean a simple adjustment of
wetland location from one side of the site to the
other. If there are no nearby wetlands, locating the
site near intact blocks of other habitat types (forested
upland, green infrastructure sites) will still increase
the ecological value of the wetland. By providing
landscape connectivity between existing habitats
and newly established wetlands, planners can
foster the movement of plants and animals across
the landscape, and more fully integrate Stormwater
wetlands into the natural environment.
We developed several prototype constructed
wetlands to illustrate integration of ecological
function into Stormwater management; these
prototypes can be viewed in our presentation at
http://www.epa.gov/maia. Our designs attempt to
mimic natural, depressional wetlands with overland
inflow and evaporation or groundwater discharge
outflow. All designs meet EPA standards for trapping
overland flow and preventing pollutants from
reaching groundwater. We believe a tiered design,
with several topographic levels providing slightly
different habitats ranging from fully inundated to
well drained soils, provides the best year-round
diversity of habitats while maintaining Stormwater
capture functions. Where ecologically enhanced
Stormwater wetlands are used, particularly in an
urban environment, planners may also realize a
public relations benefit through the use of walking
paths or boardwalks constructed around the retention
system. Birdwatchers, teachers, and general wildlife
watchers are known to visit constructed wetlands,
and signage at these sites provide an excellent
opportunity for communicating how Stormwater
control can enhance the natural environment. In new
housing developments, the wetlands can provide
a scenic focal point for the neighborhood and may
enhance property values. With relatively little
additional effort, site planners can greatly enhance
both the biological function and the scenic value of
Stormwater wetlands.
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Overview of Stormwater Best Management Practices (BMPs) in Delaware
Presented by:
Randy Greer, DNREC
The Stormwater management practice with which
most people are familiar is the Stormwater
management pond or basin. Runoff is collected in
the pond and either held there to be released at the
pre-development discharge rate, or the runoff is
infiltrated into the ground. Stormwater ponds can
be permanently wet, with typically three to four
feet of water. They may also be dry, only containing
water during rain events. They can be designed with
an outlet structure to release water into a ditch or
stream, or they can be designed without an outlet
structure, allowing the runoff volume to infiltrate
into the existing soil.
Any of these types of ponds may be excavated. They
may also be created by constructing an embankment,
or dam, through a depression to develop a pond area.
Ponds may also be a combination of embankment
and excavation. All Stormwater management ponds
in the State must be designed and constructed
in accordance with USD A Natural Resources
Conservation Service's Pond Code 378.
A properly designed wet pond will always contain a
pool of water, regardless of when the last rain event
occurred. The permanent pool may be supported
by groundwater, or totally supported by runoff
generated throughout the watershed draining to the
pond. Ponds designed to be wet that are constructed
in areas of sandy soil may need to be lined with clay
or a synthetic liner to prevent the permanent pool
from infiltrating.
A wet pond will contain approximately three to
four feet of water depth within the permanent pool.
Enough volume is provided above the elevation
of the permanent pool (to the top of bank of the
pond) to store and contain the developed runoff and
discharge it at pre-development rates. To achieve
the water quality objectives of the Sediment and
Stormwater Regulations, the quality storm runoff
should be held in the pond and released over a
twenty-four hour period. This time delay allows for
settling of 80% of the suspended solids that enter the
basin in the runoff.
Schematic of a wet pond showing aquatic and safety
benches (Source: Schueler, 1987)
The side slopes of Stormwater management basins
are designed to be no steeper than 3:1. A 3:1 slope
can be mowed and maintained more easily than
steeper slopes and they can be traversed by foot with
little difficulty.
Wet ponds are designed with benches, or level
areas, around the pond for safety. Two ten foot wide
benches should be provided: one at one foot above
the permanent pool elevation and one at one foot
below the permanent pool elevation. If someone
were to fall while walking along the top of bank of
the pond and roll down the pond slope, they would
come to rest on the bench above water. If the same
person were walking along the water's edge and
slipped, they would only fall into a foot of water,
rather than three or four feet. These benches have
the added benefit of providing a good environment
for the establishment of aquatic grasses and other
vegetation. In addition to providing habitat for pond-
dwelling critters, this vegetation can create a screen
that discourages people from wandering too close to
the open water.
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People are often concerned about mosquitoes
breeding in stormwater management ponds. If the
pond is designed properly, with three to four feet of
depth in the permanent pool, an aquatic ecosystem
will become established in the pond with fish, frogs
and other predators to keep mosquito larvae in
check.
Another concern with stormwater ponds is that
they will become cattail- or phragmites-infested
holes in the ground. Again, if the pond is designed
and constructed properly, the water depth will
be greater than what is optimum for the growth
of these invasive species. Both can be managed
through mechanical removal or chemical means if
they are introduced into the pond. Furthermore, if a
"pondscaping" plan is implemented, more desirable
aquatic species like reeds and rushes will become
established and out-compete the invasive species.
Forebays are established at the pond inlets to
capture sediment as runoff enters the stormwater
management basin. Forebays are contained areas
at the inlets that are deeper than the remainder of
the pond to allow for sediment accumulation. By
allowing a place for sediment to settle at the inlet,
maintenance of the stormwater pond is easier.
Maintenance can be confined to excavating the
accumulated sediment from the forebay, rather than
dewatering the basin to muck out the sediment from
the entire pond bottom.
Pond inlets should be designed to be as distant from
the outlet structure as possible. Doing so provides
for the longest flow path between inlet and outlet,
allowing for the most sediment settling time to
occur. Inlets that are too near the pond outlet can
result in "short circuiting" of the flow and reduced
pollutant removal.
The original urban stormwater BMP is the dry basin.
Dry stormwater basins do not contain a permanent
pool and remain in a turf condition until a rain event.
During the storm, runoff is stored in the basin and
discharged at pre-development rates. This approach
works well for flood control, or stormwater quantity
management, but provides little pollutant removal
capabilities, or stormwater quality management. By
introducing extended detention in dry basins, runoff
from the quality storm events must be held in the
basin and released over a twenty-four hour period to
allow sediment and other pollutants to settle out.
Better sediment removal capabilities are seen when
runoff is introduced to a permanent pool rather than
into a dry basin. To achieve better quality treatment
from dry extended detention basins, oversized
forebays at the inlets and a micropool prior to the
pond outlet provide the necessary pool area for
sediment removal, while maintaining a dry basin for
management of larger storm events.
Ponds are classified by USDA Natural Resources
Conservation Service's Pond Code 378 as either
embankment or excavated ponds. In an embankment
pond, fill material is used to create a dam to pond
water. In an excavated pond the entire basin is
excavated below the existing grade. Ponds may also
be a combination of embankment and excavation.
Any basin, wet, dry or infiltration, may be excavated
or embankment.
All of the components necessary to construct
the pond embankment and outlet structure will
be designed and detailed on the approved plan.
The principal spillway is composed of the outlet
structure and the outfall pipe. The outlet structure
may be a corrugated metal standpipe or a modified
concrete catch basin, each with orifices and/or weirs
to discharge the various design storm flows. The
outfall pipe is connected to the outlet structure and
carries the discharge flow through the embankment
to the point of discharge in the stream. The outfall
pipe can be constructed of various materials; the
pipe diameter, length, slope, and material should
be detailed on the plan. The outfall pipe joints and
the connection to the outlet structure must all be
watertight. Rock outlet protection must be provided
at the discharge end of the outfall pipe to dissipate
energy and protect the area from erosion.
Infiltration is a stormwater management practice
that may be designed throughout the state, but is
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most commonly seen in the coastal areas of Sussex
County where soil is sandy and infiltration rates
are high. In an infiltration facility, all of the runoff
will be discharged back into the ground, not surface
discharged into a ditch or stream.
Infiltration can occur in open ponds or basins, in
underground manifold systems, and in trenches.
An infiltration basin will be dry until a rain event
occurs. After a rain, runoff from the watershed is
stored in the infiltration basin until the existing soil
can take that runoff in through infiltration. In an
underground infiltration manifold system, runoff is
conveyed through a surface inlet into a perforated
pipe system that is laid in a stone bed. The pipe and
stone provide volume to store the runoff until it is
able to infiltrate.
Less common infiltration practices include trenches,
pavers, and porous pavement. In an infiltration
trench, runoff enters a stone-filled trench by surface
flow and is held there until the runoff infiltrates.
Pavers provide openings in the parking surface
where water is conveyed to a stone reservoir layer
below to allow the runoff to infiltrate. Pavers should
only be used in overflow parking situations where
their useful life will not be shortened by excessive
amounts of sediment, oil and other pollutants.
Non Rooftop Disconnection—Permeable Pavers
P
Porous pavement contains less fine aggregate in the
mix to allow water to flow through the pavement
to the stone reservoir below where runoff will be
held until it is able to infiltrate into the existing soil.
Porous pavement requires regular maintenance,
including vacuuming and power washing to prevent
sediment from sealing off the surface.
Infiltration systems, particularly underground
systems, must have a suspended solids filter to
remove sediment from the runoff before it enters
the infiltration system. Sediment can easily clog the
bottom of an infiltration facility, causing it to fail. In
most cases, vegetation in the form of a grassed swale
is used as a suspended solids filter, but occasionally
a structural filter will be used at the catch basin.
Infiltration practices are normally designed to
manage the quality storm runoff, and can be used
to manage larger storms if the soils and measured
infiltration rate permit. However, a safe overflow
must be provided to bypass larger storm events
through the infiltration practice.
Infiltration trenches and basins must be sized to
adequately infiltrate the design runoff volume within
48 hours. Statistically, Delaware receives rainfall
every three days, so the infiltration system must
drain within 48 hours so that the facility volume is
available for storage of runoff from the next storm
event.
Green Technology BMPs include conservation site
design, impervious area disconnection, conveyance
of runoff through swales and biofiltration swales,
filtration through filter strips, terraces, bioretention
facilities, and recharge through infiltration facilities.
The Green Technology approach is designed to
intercept runoff from rooftops, parking lots and
roads as close as possible to its source, and direct
it into vegetative recharge and filtration facilities
incorporated into the overall site design and runoff
conveyance system.
Incorporating stormwater management into the
core of the site design for a new development
allows stormwater to be treated as a resource
rather than as an afterthought. Conservation site
design takes into account the ideas of low impact
development (LID) that were discussed earlier in
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the Principals of Stormwater Runoff section. By
clustering development, leaving areas undisturbed,
and reducing impervious surfaces by narrowing
streets and using gravel drives rather than asphalt or
concrete, less runoff is developed. Constructing open
swales and creating natural areas to which to direct
runoff allows for recharge of that runoff rather than
surface discharge into streams.
The benefits of LID extend beyond water quality.
While less impervious surfaces, greater amounts of
open space, open swales, and buffers all have the
benefit of increased infiltration rates and lowered
volumes of runoff to mimic the pre-development
hydrology, there are other benefits as well. Leaving
forested areas, wetlands, and open spaces in their
pre-development condition preserves habitat for
the plants and animals living in that ecosystem.
Providing or maintaining open space is a benefit to
the community in a residential area and enhances
property values. People want to have open space
around them, as is evident by the popularity of golf
course living.
Environmentally Sensitive Design
Impervious areas such as rooftops can be
"disconnected" by directing downspouts onto
grassed areas to allow the roof water to infiltrate
and recharge groundwater. This is preferable to
piping the roof water directly from the house or
building to the driveway, street, or storm drain
system where it will be collected and discharged
into the Stormwater facility or receiving stream with
no recharge at all. Roadways and parking areas can
be "disconnected" by allowing them to sheet flow
off into grassed swales or open areas. Runoff in
swales, while being conveyed to the discharge point,
has a significant chance of recharging while runoff
in a pipe collection system is totally conveyed to
the downstream water body, with no reduction in
volume.
Structural Practices—Filtering Systems
Biofiltration swales convey runoff at shallow flow
depths through wide swales. Swale bottom widths
are generally two to eight feet wide, but can be
wider if a level spreader is provided to spread flow
evenly throughout the swale bottom. The design
depth of flow for the quality storm is one half the
swale vegetation height to provide the maximum
grass contact and filtration. Biofiltration swale
vegetation is maintained at a height of six to eight
inches, allowing for a design flow depth of three to
four inches.
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Biofiltration Swale
Biofiltration swales can be very effective in
removing Total Suspended Solids (TSS) and
adsorbed metals, although they are less effective in
removing nutrients. While swales are not thought
to be capable of quantity management, designs
incorporating check dams can provide control of
peak flows.
Filter strips are designed based on the same
principal as biofiltration swales. They spread runoff
uniformly over a filtering surface of vegetation,
providing infiltration and pollutant removal. Filter
strips can provide substantial treatment if they are
not overloaded by sediment and runoff. They are
best suited for treating small areas of impervious
surfaces.
Structural Practices—Filtering Systems
r Ite
Bioretention facilities are landscaped pocket
depressions designed to infiltrate runoff through
an engineered soil media. The media is porous,
containing washed sand, peat, and triple shredded
hardwood mulch. The quality storm runoff is stored
in a depression on the surface, then the runoff filters
through the porous media and either infiltrates
into the existing soil or is discharged through the
underdrain. During the growing season, plants in
the bioretention facility use nutrients in the runoff,
providing for some pollutant removal in that fashion.
When bioretention facilities are incorporated into the
landscape, they can provide substantial filtering and
nutrient transformations before runoff is discharged
into the conveyance system. Originally bioretention
was designed to treat only the quality storm and
bypass the larger storms; however, they have been
proven to provide some peak flow attenuation,
making bioretention an option for quantity treatment
as well.
Most Green Technology BMPs incorporate
infiltration as part of the treatment process.
However, infiltration trenches located in swales
can be considered a Green Technology BMP of
their own. Infiltration trenches in swales provide
additional wetted surface area and storage volume,
and often they can be designed to penetrate shallow
impermeable soil profiles to recharge deeper soil
horizons. The same design criteria would apply for
these infiltration trenches as other, more traditional,
infiltration practices. Pretreatment measures are
extremely important in the design of infiltration
trenches since high sediment pollutant loadings will
cause failure.
There are methods of treating runoff in urban
settings other than construction of a pond or
infiltration system. Structural BMPs such as
filtration systems including sand filters, gravity
and/or swirl separators and catch basin inserts
are available when space does not allow for the
construction of traditional BMPs, as when a site is
being redeveloped. These types of BMPs are not
applicable when stormwater quantity management
Proceedings of the Workshop on Stormwater Management and Mosquito Control
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is required; they are quality treatment practices only.
Furthermore, only the sand filter has been approved
as a stand-alone quality treatment practice. The
other types of units may be used in a treatment train
approach on a case-by-case basis.
Engineered stormwater management filtration
BMPs are structural units that allow for runoff
to flow through media such as sand, polymeric
materials, activated carbon, compost, etc., to remove
pollutants. The quality storm, or first flush, of runoff
is treated for pollutant removal while larger flows
bypass the system. The medium used determines the
type of pollutants that are removed. Sand has the
capability to remove sediment and hydrocarbons.
Polymer materials are formulated for hydrocarbon
removal. Activated carbon is used to remove
organics and metals in addition to hydrocarbons.
Nutrients are removed in compost media.
Each proprietor of a filtration system has a
specialized medium targeted to certain pollutants;
however, many of the manufacturers now offer
the option of various media to target site-specific
pollutant loads. Filtration BMPs such as the
sand filter, Aqua-Filter, Ultra Hydro-Kleen and
StormFilter all require monitoring and periodic
maintenance which is more intensive than traditional
stormwater practices such as ponds. Eventually,
the filtration media will need to be removed and
replaced; the time between replacements of media is
dependent upon pollutant loading.
The sand filter is the only engineered structural BMP
that has been approved in Delaware as a stand-alone
stormwater quality treatment practice. The sand
filter is a linear concrete unit with two chambers
running the length of the filter. One chamber has a
grate at the surface; this is called the sedimentation
chamber. Runoff flows from the surface of a parking
lot, through the grate, and into the sedimentation
chamber. This chamber is 18 inches deep and stays
wet. It is here that the largest sediment particles
settle out. Water from the sedimentation chamber
overflows through a series of weirs into the second
chamber, the filtration chamber. The filtration
chamber has a solid cover so that no runoff goes
directly into the filtration chamber. The filtration
chamber is filled with 18 inches of sand. As the
runoff percolates through the sand, smaller sediment
particles and other pollutants such as oil and grease
are filtered out. Once the runoff filters through the
18 inches of sand it is discharged through a low flow
underdrain pipe into the storm drain system.
Many engineered stormwater treatment structures
are available for treatment of the first flush of
runoff. Products such as Stormceptor, Vortechs,
CDS (Continuous Deflective Separation), BaySaver,
Aqua-Swirl, and Downstream Defender use gravity
and/or swirl separation to remove pollutants such
as sediment, oil and grease, trash and debris from
the runoff stream. Gravity separation is achieved by
forcing runoff through a series of baffles to collect
both floatable pollutants and settleable solids. Units
that use the swirl technique, also known as vortex or
hydrodynamic technology, do so by deflecting the
runoff as it enters the unit, taking advantage of the
energy in the flow itself, and propelling that runoff
into a vortex. Sediment is caught up in the swirling
flow path to settle out later.
Engineered stormwater treatment structures require
more intensive monitoring and maintenance
than more traditional methods of stormwater
management. They are suited to highly or totally
impervious sites. They are designed to treat small
storm events such as the quality storm, and require a
bypass for peak flows of larger storms. They all are
constructed underground, taking up no developable
land. These units adequately trap floatable
pollutants, such as oil and grease and trash and
debris, as well as heavier settleable solids, but they
are not effective at removing suspended solids and
soluble pollutants such nutrients. For these reasons,
these units have not been approved as stand-alone
stormwater quality treatment practices. They may be
used as part of a treatment train, or in redevelopment
projects where land availability is limited.
Catch basin inserts are varied in how they function
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and in the level of pollutant removal they provide.
Some catch basin inserts are simple gross pollutant
removal systems, while others employ filtration
media for removal of oil and grease, hydrocarbons,
particulate metals, and sediment. What these inserts
do have in common is their ability to be inserted
into a new or existing catch basin. This allows them
to be used extensively in retrofit projects and in
redevelopment projects where space is limited for
stormwater management facilities. As will all of the
engineered structural BMPs, catch basin inserts are
only approved for use as part of a treatment train on
a case-by-case basis.
There are many varied type of stormwater
management BMPs. There is not one BMP that is
applicable to all sites. Each of them has their place.
Some sites may even have two, three, four, or more
different types of practices, all with same goal:
to enhance the quality of runoff from the site and
provide flood control.
Summary
Traditional Approaches
• Wet Ponds
• Dry Ponds
• Infiltration
Structural BMPs
• Filtration Systems
• Separation Units
• Catch Basin Inserts
Green Technology BMPs
• Conservation Design
• Disconnect Impervious Surfaces
• Biofiltration Swales
• Filter Strips
• Bioretention
• Infiltration
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Facilitated Discussion
Presented by:
Kent Thornton, FTN Associates
Following the presentations, a discussion among
participants was facilitated to:
1. Address questions that were not raised during
the presentations because of time constraints;
2. Identify characteristics of stormwater
retention basins that would achieve desired
water quality goals and minimize mosquito
production; and
3. Identify approaches for improving public
knowledge about:
a. mosquito production and disease
transmission;
b. contribution of stormwater retention/
detention basins to mosquito problems;
and
c. contribution of stormwater retention/
detention basins to achieving water
quality standards.
QUESTIONS
Questions and responses raised during the facilitated
discussion session included:
1. Because maintenance is so important to the
effective operation of stormwater basins, can
the maintenance requirements be included as
part of the NPDES permit?
Delaware has created a Task Force
to evaluate the current regulatory
requirements for maintenance and provide
recommendations for ensuring stormwater
basins are maintained. In Maryland,
stormwater basin inspection agreements
are included as part of the 2000 stormwater
regulations. Under these regulations,
stormwater basins are inspected every
three years and recommendations provided
to the owner for maintenance. The EPA
might be able to incorporate maintenance
requirements as part of the Municipal
Separate Storm Sewer System regulations.
Additional avenues for ensuring maintenance
of stormwater basins and practices are being
pursued by both of the states and EPA.
In Maryland, maintenance is included in
the NPDES MS4 permits and regulations.
However, there are no federal, Delaware,
or Maryland regulations that satisfactorily
address maintenance of stormwater sites for
mosquito control.
2. Where does the public think mosquito
problems arise?
This depends on where they live in the
States, and the location of the stormwater
basin. If wetlands are prevalent in the
community, the public might view the
wetlands as the culprit and want to take
action to eliminate or treat the wetlands.
Leading public perceptions of wetlands are
as swampy, snake and mosquito-infested
areas. Because stormwater wetlands typically
are located near houses, the stormwater
sites are likely to be viewed as the culprit.
In some instances, stormwater wetlands do
contribute to mosquito production, but this is
not always the case. Public education must
be part of integrated stormwater management
for stormwater control, mosquito reduction,
and wildlife habitat enhancement.
3. Where do mosquito problems occur and
why?
The geographic location of mosquito
problems, the specific mosquito species,
land use and ownership, and season are all
considered by mosquito control agencies
when complaints are received. The relative
importance of mosquito production in
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stormwater basins varies according to
the design and maintenance of the site,
mosquito-borne disease activity in the area,
public tolerance of mosquito annoyance, and
the proximity of natural mosquito producing
wetlands.
Land use and property management
by owners can contribute to mosquito
production by supporting areas that pond
or catch water (e.g., roof gutters, tires, open
containers, poorly drained areas). The source,
or location, of mosquito problems varies by
season. In the spring, mosquito production
in natural habitat occurs most commonly
in areas experiencing seasonal flooding.
In the summer low flow period, mosquito
production in natural wetlands occurs most
commonly in permanent and temporary
pools. Mosquito production can occur at any
time in stormwater sites, but most commonly
occurs during the summer, particularly
in shallow water stormwater basins with
abundant emergent vegetation and few,
or no predators of mosquito larvae. Land
use and property management by owners
can contribute to mosquito production in
stormwater basins. Deep water detention
basins with high levels of sedimentation and/
or accumulation of rubbish must be regularly
maintained by dredging to prevent the
creation of shallow water mosquito breeding
areas. The particular species of mosquito is
also important. Different mosquito species
are associated with temporary pools of water
versus permanent pools, and different species
are vectors for different diseases. Finally,
tolerance to mosquitoes varies significantly
among individuals, from any mosquitoes
considered intolerable by some to tolerance
of a bite every minute by others. All these
factors are considered in the mosquito
control approach.
4. What assurances are there that pesticide use
will not be more harmful than West Nile
Virus (WNV)?
Any pesticide in use for mosquito control
has gone through extensive research and
risk assessment modeling as part of the EPA
pesticide registration process. In addition,
these pesticides can only be used by, or
under the supervision of, a licensed pesticide
applicator according to the registration
requirements. These conditions reduce the
risk of adverse effects to human health,
wildlife or the environment from exposure
to pesticides used for mosquito control.
This opinion is supported by a recent court
ruling and by EPA's pending Final Rule
that an NPDES permit is not required for
applications of insecticides registered as
mosquito larvicides to bodies of water.
STORMWATER RETENTION BASINS AND MINIMIZING
MOSQUITO PRODUCTION
The optimal design for a stormwater retention basin
that minimizes mosquito production would achieve
the following desired goals:
1. Satisfy the regulatory requirements of the
Clean Water Act for stormwater control.
2. Control flooding/water quantity in
downstream systems (MD, DE).
3. Support water quality standards of the
receiving waters by attaining NPDES
requirements to:
a. Reduce total suspended solids by 80%
(DE, MD)
b. Reduce total phosphorus loads by 40%
(MD)
4. Protect or improve the receiving stream
channel and riparian habitat.
5. Provide for easy maintenance.
These criteria are already part of the Delaware
and Maryland Stormwater Design Manuals for
stormwater management basins and include:
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For Wet Ponds
• Steep slopes (no steeper than 3:1, with 4:1
slopes preferred),
• Minimal vegetation (< 20% of the surface
area), which does not choke the basin,
Permanent open water 3-4 feet deep (i.e.,
deep enough it does not dry out and provides
for fish habitat), and
• Sidewall benches for public safety.
For Dry Ponds
Pond does not hold water for longer than 48-
72 hour period.
These design criteria, with the possible exception
of sidewall benches, should minimize mosquito
production in both wet and dry ponds. The sidewall
benches may retain shallow, pooled water where
natural predators might not be able to prey on
mosquito larvae. In addition, these benches can
become colonized by vegetation, which can create
habitat for mosquito production. Public safety,
however, cannot be compromised. An alternative
design should be sought that has side benches to
protect the public, but as narrow as possible without
compromising safety, that drain readily toward the
basins interior, and that minimize colonization by
emergent vegetation.
Stormwater basin inflow/outflow designs are
adequate to achieve storm water goals and, if
properly maintained, should minimize mosquito
production. However, water can pool in the
interstices of the outflow riprap or energy dissipater,
creating a habitat for mosquito production.
Multiple sized aggregate was discussed, but the
velocities during storm flow would likely scour
small aggregate. Concrete or other solid materials
for energy dissipation crack during freeze-thaw
cycles, so properly sized rip-rap is considered the
best choice. Substrate having good drainage or
percolation characteristics under the riprap might
also be explored. This is an area that could also
benefit from design research.
Maintenance is an important issue associated with
Stormwater basins. Many stormwater basins are
under private ownership. In many instances, the
owner or community association does not realize
they are responsible for the maintenance of the
stormwater basins, which can be expensive. In
addition there are no, or limited, government funds
available to off-set maintenance costs. In Maryland,
regular basin maintenance is part of the Stormwater
Management Plan or Stormwater Pollution
Prevention Plan. Stormwater systems are reviewed
and inspected every three years.
At present, there are no requirements in the
Delaware, Maryland, or federal stormwater
regulations, policies, or guidelines to consider and
manage for the unintended consequence of mosquito
production in stormwater management sites.
Given the concerns over mosquito-borne diseases,
guidelines are needed. A positive step along these
lines was taken when the EPAs Office of Waste
Water invited the American Mosquito Control
Association in May 2005, to help revise the EPAs
final draft for the Agency's "Stormwater Pond and
Wetland Maintenance Guidebook" (a BMP for wet/
retention stormwater management ponds and their
associated wetlands.
PUBLIC EDUCATION
Educating the public about the regulatory
requirements for stormwater systems and factors
associated with mosquito production was raised as
an important topic. The following suggestions were
offered to improve public education:
1. Frequent meetings with stakeholders to
develop trust and reinforce information;
2. Use of public service announcements;
3. Use of agency and non-governmental
organization newsletters, brochures, and Web
sites;
4. Providing factual messages that emphasize
that:
a. There are multiple objectives for
stormwater management basins (flood
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control, water quality improvement,
etc.).
b. Mosquito production can occur in
stormwater basins and might become
a problem.
c. There are multiple mosquito
species, each with different habitat
requirements and different risks to
human populations.
d. Reducing the amount of water,
sediment, and nutrients entering
stormwater basins can improve the
quality of the water stored in the
stormwater basins so they can support
natural controls on mosquitoes (e.g.,
insect, fish predators).
e. Use of natural controls can reduce
mosquito production, but natural
controls will not eliminate mosquito
production.
f. The importance of identifying the
issues within communities, including
individual tolerance of mosquitoes,
and concerns over West Nile virus,
pesticide use, mosquito production,
and stormwater basins.
5. Risks from stormwater pollutants, mosquito
vectors for West Nile virus, and pesticide use
in mosquito control can all be reduced. There
is some disagreement among the public about
what constitutes the greatest risk: for some,
the risk of West Nile virus exceeds the risk
from pesticide exposure; for others, concern
about pesticide exposure for children exceeds
concern over West Nile virus. However, the
preponderance of peer reviewed scientific
evidence indicates that pesticides, when
used according to label directions for larval
and adult mosquito control, pose minimal
risk to human health and environmental
quality. The documented negative impacts of
mosquito-borne diseases in the U.S., such as
West Nile virus, eastern equine encephalitis,
western equine encephalitis, etc., have been
much greater on human health and wildlife
populations than the impact of mosquito
control insecticides.
Delaware held a series of workshops to provide
information to the public about stormwater basin
management, and maintenance requirements. These
workshops were effective in bringing stakeholders
together, resolving conflicts that were arising
among stakeholder interests and regulatory agency
requirements, and providing factual information
on all issues. A similar workshop format might be
useful in providing information to the public on
stormwater basin management, mosquito production,
West Nile virus transmission, and pesticide use.
EPA has a Web site that provides fact sheets on
responsible pesticide use for mosquito control that
would be useful for public education.
OTHER ISSUES
While stormwater basins can be effective in
achieving water quality goals and minimizing
mosquito production, better watershed management
practices can significantly reduce inflow volume
and pollutant loads. Environmentally Sensitive
Design (ESD) or Low Impact Development (LID)
techniques, using green technologies, enhance
filtration/infiltration and reduces pollutant loading.
Information on ESD is available in the Maryland
Design Manual and from the Newcastle model. The
key is to focus on reducing impervious surface area
and sheet flow through buffer areas, encouraging
natural conservation, and promoting sustainable
development.
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Summary
A Stormwater Management Workshop was held
on February 9, 2005, at WorWic Community
College, Salisbury, Maryland to discuss Stormwater
management basins and their role in mosquito
production and potential for wildlife habitat.
Participants represented state, federal, and local
governments; engineers; mosquito scientists and
control specialists; non-governmental organizations;
homeowners' associations; and interested members
of the public.
The regulatory requirements for Stormwater
management under both federal (EPA) and state
statutes (DE, MD) were presented. Stormwater
management is regulated through the NPDES
program within EPA and state agencies with
designated authority. Stormwater regulations include
specific requirements for flood control and total
suspended solids reductions (> 80%) in both DE
and MD, with MD also requiring at least a 40%
reduction of Stormwater total phosphorus loads.
Mosquito production and mosquito control programs
were discussed both from a national perspective and
state perspective (DE and MD). There was a general
recognition that Stormwater basins can contribute
to mosquito production problems, particularly if
these basins are not adequately maintained. As
with any biological organism, mosquito production
and control is a complex issue, that depends upon
the specific mosquito species, species feeding
times, disease-specific vectors, unique habitat
requirements, and natural controls. Mosquito control
programs are tailored to specific locations, habitats,
community characteristics, mosquito species, and
season of the year.
The wildlife habitat potential of Stormwater basins
has not been extensively investigated. However,
Stormwater basins have the potential to provide
the ecological conditions that favor natural aquatic
predators of mosquitoes, including permanent pools,
complex emergent/submergent vegetation structure,
complex food webs, and good water quality. While
natural mosquito predators often won't reduce
mosquito populations to levels desired by local
communities, mosquito predator populations should
be encouraged through Stormwater basin design and
management
Engineering considerations for Stormwater
management practices are included in design
manuals for both Delaware and Maryland, and are
used by the construction, development, municipal,
and industrial communities in designing Stormwater
systems. As within any built structure, maintenance
is the linchpin for successful operation of
Stormwater systems.
A facilitated discussion followed the presentations.
A question and answer period initiated the
discussion. Following this question and answer
period, workshop participants discussed the optimal
design for a Stormwater management site that would
achieve water quantity/quality goals and minimize
mosquito production. In general, the current designs
for Stormwater basins (wet basins) in both Delaware
and Maryland satisfy the optimal design criteria,
although some minor design changes are warranted.
The principal design feature that might contribute
to mosquito production and invasive vegetation
are sidewall benches that are required by Delaware
for public safety. There was also concurrence that
Stormwater detention (dry) basins would not be
problematic for mosquito production if they fully
dried after their designated 24-72 hour wet periods.
Mosquito production problems frequently occur
when these systems retain water past 5-7 days, either
because of heavy or frequent rains, improper design
or construction, and/or inadequate maintenance.
Maintenance was discussed as a critical issue
in the successful operation of Stormwater
management systems whether they are retention
or detention ponds. There was some discussion of
incorporating maintenance requirements in NPDES
Stormwater permits. Maryland regulations do
Proceedings of the Workshop on Stormwater Management and Mosquito Control
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include maintenance. Suggestions for improving
public education were also provided by workshop
participants.
The workshop provided an effective forum for
showcasing and discussing different perspectives
on stormwater management practices and mosquito
production. It is hoped the constructive impacts
of this workshop won't only be felt at municipal,
county, or state levels in Delaware and Maryland,
but also at a national level.
At the national level and as a direct consequence
of the workshop, interactions between EPA and the
American Mosquito Control Association (AMCA)
were initiated in May 2005, with the focus on
having the AMCA help revise the EPA's final draft
for the Agency's "Stormwater Pond and Wetlands
Maintenance Guidebook" (a BMP for wet/retention
stormwater management ponds and their associated
wetlands).
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Unfinished Business
Written by:
Frederick Kutz, Consultant in Environmental Sciences
and Roman Jesien, MD Coastal Bays Program
The Stormwater Workshop was successful in
bringing together people of diverse disciplines and
venues; attendance filled the largest room at WorWic
Community College. During this one-day event,
both formal and informal discussions occurred
throughout the workshop. Many of the central
issues involving storm water management, mosquito
production, wildlife habitat and engineering
considerations emerged and were discussed openly
in a non-confrontational environment. However, the
central focus of the Workshop was broad, and thus,
some issues were either insufficiently discussed or
did not surface at all because of time constraints.
The objective of this chapter is to outline some of
these remaining issues for future consideration.
LOCATION, LOCATION, LOCATION!
This old adage of real estate contains a certain truth
about stormwater management facilities. No central
geospatial inventory of stormwater management
facilities exists; so for the most part, many locations
are unknown. Therefore, much information about the
types of facility, their upkeep, their ownership and
their functioning is unknown. Action is needed to
remedy this lack of knowledge.
BEST MANAGEMENT PRACTICES (BMPs)
This is a widely used term in engineering science.
In most cases, BMPs are supported by research
results that confirm that BMPs are accomplishing
intended results. In stormwater management
systems, however, wide latitude has emerged in the
configurations and locations of these structures.
Studies need to continue to confirm that BMPs are
in fact accomplishing their intended ecological
functions.
PROVISION OF WILDLIFE HABITAT
One of the disappointing features of the Workshop
was the lack of discussion on the habitat value of
stormwater management facilities (SMFs).
SWFs can possess characteristics common to
degraded wetlands that include: wide fluctuations
in water levels, and water contaminated with high
nutrient, sediment, metal and in some locations, high
chloride loads. The degraded physical and chemical
characteristics are typically manifest in low plant
diversity dominated by tolerant (e.g., cattail) and
invasive plants (e.g., Phragmites, purple loosestrife)
and low animal diversity that can be dominated by
nuisance pests such as mosquitoes. Therefore, it is
paramount to minimize stormwater runoff wherever
possible. Infiltration of storm runoff through
maintenance of pervious surfaces should be strongly
promoted.
However, in spite of degraded conditions, SWFs,
such as retention basins containing a permanent
pool, can serve as beacons of aquatic habitat amidst
heavily urbanized landscapes. Depending on
water quality, tolerant fish and insect predators can
survive in SMFs and can provide effective control
on mosquito production. Also, SMFs can provide
marginal habitat for birds and mammals in areas that
would otherwise be without access to standing water.
More ecological research is needed to address these
complex habitat issues.
PREDATION
Stormwater management facilities are inhabited by
a diverse group of animals; if satisfactory habitat
exists, this species list will include predators of
immature mosquitoes. To further complicate this
managed ecosystem, different types of facilities
at different locations might be influential in
determining the kinds of animals and plants found
Proceedings of the Workshop on Stormwater Management and Mosquito Control
47
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in their environs. Few studies have elucidated
the degree of predation that these animals might
provide. Adults and immature stages of a number
of insects present in stormwater management
systems have been shown to be predatory on
immature mosquitoes, but their influence on
population dynamics appears to be undetermined.
Most observations indicate that predation does
occurs, but not to the extent of providing effective
population control. However, not all stormwater
ponds produce excessive amounts of mosquitoes
warranting control, so it can probably be assumed
that the natural predators in such non-problematic
ponds play some role in helping to limit mosquito
production. More research is needed to demonstrate
the role of predation in population dynamics of
stormwater management facilities, and particularly
whether some biological control mechanism may be
possible.
INNOVATIVE STORMWATER MANAGEMENT FACILITIES
Within the last several years, stormwater
management guidance has been enhanced to
encourage a wider variety of approaches. In fact,
many other designs are available to supplement
the traditional approach of constructing ponds.
Designers of stormwater management systems
should be encouraged to use these newer
technologies that would reduce mosquito production,
particularly in suburban settings.
HARMONIZATION WITH NATURAL LANDSCAPE
To the extent possible, location of SMFs should
consider the features of the environment to describe
the contributing drainage area. Natural wetlands
should be separated from SMF treatment and only
fully treated stormwater should be allowed to enter
wetlands. According to recommendations from
the Center for Watershed Protection (http://www.
cwp.org), there should be no increase in average
discharge to the wetland if treated discharge does
enter the wetland.
MAINTENANCE
A simple truth in stormwater management is that
facilities require periodic maintenance. Without
this required maintenance, it is doubtful that the
ecological services expected of these facilities
will be provided. Additionally, poorly maintained
facilities contain the necessary environment for
mosquito production, and in many cases, diminished
wildlife habitat. More effort is needed to identify
poorly maintained facilities and persuade the owners
of them to provide the periodic care critical for their
effective operation.
POST CONFERENCE SUCCESS STORY
One positive result of the Stormwater Workshop
was an invitation issued by the EPA Assistant
Administrator for Water to the American Mosquito
Control Association (AMCA) to become more
involved with the process of drafting stormwater
management guidelines. The Office of Water at EPA
is charged under federal law with implementing
the Clean Waste Water Act that contains regulatory
authorities for stormwater. The AMCA is a
professional organization of mosquito control
workers and scientists with a mission to provide
leadership, information, and education leading to the
enhancement of health and quality of life through
the suppression of mosquitoes and other vector-
transmitted diseases, and the reduction of annoyance
levels caused by mosquitoes and other vectors and
pests of public health importance.
As an outcome of the workshop, in May 2005, on
behalf of AMCA, William Meredith (Delaware
Mosquito Control Section) met in Washington, DC
with Nikos Singelis (EPA Office of Waste Water
Management) and other EPA staff from the EPAs
Office of Water to discuss how mosquito control
concerns could be better addressed relative to the
construction and management of stormwater ponds
and other stormwater management facilities. This
very productive meeting quickly led to formation
48
Proceedings of the Workshop on Stormwater Management and Mosquito Control
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of an AMCA Stormwater Management Committee
that, in June 2005, reviewed and commented upon
the EPA's final draft for the Agency's "Stormwater
Pond and Wetland Maintenance Guidebook". The
AMCA submitted an extensive set of comments
and recommendations for EPA to consider. It is
anticipated that EPA will incorporate most of these
comments and recommendations into its final BMP
for wet/retention ponds, targeted for completion
by the end of June 2006. During the May 2005,
meeting, the AMCA was also told that when EPA
prepares its BMP for dry/detention Stormwater
ponds targeted for development in 2006-07, that the
AMCA will be invited to help in its crafting.
The Steering Committee for the Workshop is
delighted with the emergence of this spirit of
cooperation.
Proceedings of the Workshop on Stormwater Management and Mosquito Control 49
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Appendix A
AMCA Position Paper
Stormwater Management Facilities and Mosquito Production
ISSUES
Regulations issued under the Clean Water Act
require that pollution associated with stormwater
runoff be reduced through the use of Best
Management Practices (BMPs), but if these BMPs
are not carefully designed, implemented and
managed in a manner that also considers mosquito
production concerns, significant quality-of-life
and human health problems can arise. The EPA
implements this water quality program, but until
very recently had essentially ignored in their
regulations and BMPs public health risks associated
with mosquitoes, leading uninformed permit holders
to create new health threats and public nuisances,
while often trapping local governments between
conflicting requirements. Additionally, regulations
or opinions issued by the U.S. Fish and Wildlife
Service (USFWS) for protection of endangered
species frequently prohibit or sharply limit mosquito
control practices or maintenance activities that
might prevent or reduce mosquito production in
stormwater facilities.
BACKGROUND
EPAs "Phase II" stormwater requirements could
dramatically increase the number and extent of
urban and suburban stormwater treatment facilities
(e.g., dry/detention or wet/retention ponds,
infiltration swales, etc.) over the next few years.
At hearings in October 2002, before a House
Subcommittee, speakers from the AMCA, CDC, and
EPA all acknowledged potential mosquito problems
associated with stormwater management systems.
These hearings were driven by pressing concerns
over the emergence and spread of West Nile virus
especially in the context of mosquito problems due
to poorly maintained facilities. Unfortunately, EPA
was not quick to implement any corrective measures.
[EPA had also notified stormwater managers that any
activities in stormwater facilities that might harm
organisms listed under the Endangered Species Act
are subject to enforcement actions under that Act.]
However, more recently and more encouragingly, as
aftermath of an EPA-sponsored workshop (February
2005) that examined stormwater management and
mosquito production problems in Maryland and
Delaware, and along with a follow-up meeting with
EPA officials in Washington, D.C. in May 2005,
the AMCA has seemingly now triggered a bright,
new era within EPA relative to these matters, in
now getting the Agency to better recognize these
mosquito production problems and adopt some
solutions.
DISCUSSION
Despite past problems with having EPA
acknowledge and address—in their regulations,
BMP guidance documents and factsheets—a wide
range of mosquito production problems associated
with stormwater management facilities, during
the summer of 2005, EPAs Office of Waste Water
Management (the federal regulatory authority
for stormwater management) invited the AMCA
to make revisions to an OWWM draft factsheet
titled "Stormwater Structures & Mosquitoes." The
AMCA then proceeded to extensively undertake and
produce an acceptable final product. The AMCA
was also invited by the OWWM this past summer
to help critique and revise a voluminous draft BMP
for wet/retention stormwater management systems
titled "Stormwater Pond & Wetland Maintenance
Guidebook," which the AMCA then extensively
undertook, and we are waiting optimistically to
see how EPA has accommodated our input. During
2006 we understand that the OWWM will also
invite the AMCA to help craft and review a BMP
focused upon dry/detention stormwater management
ponds and infiltration treatment systems. All of
this is very refreshing, and seems to mark a new
era of collaboration with EPA regarding mosquito
problems and their remedies.
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NEEDED ACTIONS
The AMCA should continue to request of EPA
and take advantage of all opportunities to help the
OWWM craft regulations, policies, BMP guidance
documents, factsheets, and other instruments that
touch upon mosquito production/control issues in
stormwater management facilities, working with
EPA in professional and collegial manner. It seems
that a new era of cooperation and interaction with
EPA has now emerged regarding these matters,
one that must be cultivated and nurtured by the
AMCA. In regard to BMPs, the AMCA should
work with EPA to help ensure that the state, county
and municipal stormwater management agencies
charged with constructing and managing stormwater
facilities adhere to all mosquito control aspects of
these BMPs, with EPA achieving such compliance
through federal regulations, grant conditions,
education programs, etc. Similar attention and
breakthroughs that better accommodate mosquito
control needs/practices are also now needed with
both EPA and USFWS in regard to what to do (or
can be done) when encountering endangered species
in stormwater management facilities, especially for
addressing maintenance needs within these systems.
AMCA Position Paper - Spring Washington
Conference, 2006
52 Proceedings of the Workshop on Stormwater Management and Mosquito Control
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Workshop Attendees
Appendix B
Adkins, Jared
Kent Conservation District
800 Bay Road #2
Dover, DE 19901
P: 302-741-2600, ext. 3
Jared.adkins@state.de.us
Anderson, Robert
University of Delaware
Dept. of Entomology
Newark, DE 19716
P: 856-854-5533
rdand@udel.edu
Bason, Chris
James Farm
RR 1, Box230C
Ocean View, DE 19970
P: 302-537-1680
chrisbason@inlandbays.org
Blazer, Gail
Town of Ocean City
301 Baltimore Avenue
Ocean City, MD21843
P: 410-289-8825
sblazer@ococean.com
Blazer, Dave
Maryland Coastal Bays Program
9609 Stephen Decatur Hwy
Berlin, MD 21811
P: 410-208-3619
director® mdcoastalbays.org
Brittingham, Phillip
MDA-Mosquito Control
27722 Nanticoke Rd, Unit 2
Salisbury, MD21801
P: 410-632-3767
Buehl, Eric
Center for MD Inland Bays
16529 Coastal Highway
Lewes, DE 19958
P: 301-645-7325
habitat@inlandbays.org
Cain, Carol
MD Coastal Bays Program
9609 Stephen Decatur Hwy
Berlin, MD 21811
P: 410-213-2297
technical@mdcoastalbays.org
Cantwell, Mike
MD Dept of Agriculture
50 Harry S.Truman Parkway
Annapolis, MD 21401
P: 301-927-8357
macmda@cs.com
Caraway, Kenneth
DE Mosquito Control
1161 Airport Rd
Milford, DE 19963
P: 302-422-1512
Kenneth.caraway@state.de.us
Carey, Nathan
New Castle County
807 Old Churchmans Road
Newcastle, DE 19720
P: 302-388-9985
ncarey@co.new-castle.de.us
Charland, Jay
Assateague Coastal Trust
PO Box 731
Berlin, MD 21811
P: 443-235-2014
Coastkeeper@actforbays.org
Comstock, Steve
MD Dept of the Environment
1800 Washington Blvd
Baltimore, MD21230
P: 410-537-3543
scomstock@mde. state, md. us
Conlon, Joe
American Mosquito Control Assoc.
1500MillbrookCt
Orange Park, FL 32003
P: 904-215-3008
amcata@bellsouth.new
Cook, Heather
Ocean Pines Assoc.
239 Ocean Parkway
Ocean Pines, MD 21811
P: 410-208-0208
heatherEcook@verizon.net
Coyman, Sandy
Worcester Co. Dept of Comp. Plan
Snow Hill, MD21863
P: 410-632-5656
scoyman@co.worcester.md.us
Cummins, Carolyn
Worcester County
9628 Oceanview Lane
W. Ocean City, MD21842
P: 410-213-0586
ccummins@dmv.com
Davis, Vince
Del. DOT
PO Box 778
Dover, DE 19901
P: 302-760-2180
Vince.davis@state.de.us
Dawson, Steve
MDE, Non-tidal Wetlands
PO Box 417
Sharptown, MD21861
P: 410-543-6703 (pager)
sdawson@mde.state.md.us
Devlin, Larry
Worcester Co. Planning Commission
352 Ocean Parkway
Ocean Pines, MD 21811
P: 410-208-0208
devlincook@verizon.net
Dorothy, Jeannine
MD Dept of Agriculture
6701 Lafayette Avenue
Riverdale, MD 20737
P: 301-927-8357
Skeetermdl ©cs.com
Dyott, Steve
Town of Federalsburg
PO Box 471
Federalsburg, MD21632
P: 410-754-8173
hsdyott@hotmail.com
Ferguson, Dave
Ocean Pines Assoc.
239 Ocean Parkway
Ocean Pines, MD21811
P: 410-641-7717, ext. 3001
dferguson@oceanpines.org
Ferrao, Patricia
MD Dept of Agriculture
50 Harry S. Truman Pkwy
Annapolis, MD21401
P: 410-841-5928
ferraopn@mda.state.md.us
Francis, Woody
Corps of Engineers-Baltimore
PO Box 1715
Baltimore, MD 21203-1715
P: 410-962-5689
woody.francis@nab02.usace.army.mil
Freeland, V.Wilson
Calvert Co. Dept of General Services
175 Main Street
Prince Frederick, MD 20678
P: 410-535-1600, ext. 2299
freelavw@co.cal.md.us
Gertler, Ed
MDE-lndustrial Discharge Permits
1800 Washington Blvd
Baltimore, MD21230
P: 410-537-3651
egertler@mde.state.md.us
Proceedings of the Workshop on Stormwater Management and Mosquito Control
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Gingrich, Jack
Univ. of Delaware
Dept. of Entomology
Newark, DE 19716
P: 301-831-1308
Gingrich@udel.edu
Goeller, Debbie
Worcester Co. Health Dept.
PO Box 249
Snow Hill, MD21863
P: 410-632-1100
debbiegoeller@dhmh.state.md. us
Greer, Randy
DE Dept of Nat Res & Env Control
89 Kings Hwy
Dover, DE 19901
P: 302-739-4411
Randell.greer@state.de.us
Higgins, Michael
US Fish & Wildlife Service
177 Admiral Cochrane Drive
Annapolis, MD 21401
P: 410-573-4520
Mike_j_Higgins@fws.com
Jesien, Roman *
MD Coastal Bays Program
9609 Stephen Decatur Hwy
Berlin, MD 21811
P: 410-213-2297
science@mdcoastalbays.org
Johnson, Carl
12 Riverside Ct.
Berlin, MD 21811
carlbarbe@earthlink.net
Kincaid, Joseph P.
MDE-Tidal Water Div.
1800 Washington Blvd
Baltimore, MD21230
P: 410-961-4044
jkinaid@mde.state.md.us
Krumrine, Beth
DE Dept of Nat Res & Env Control
89 Kings Highway
Dover, DE 19901
P: 302-739-4411
Beth, krumrine@state.de.us
Kutz, Frederick (Rick) *
4967 Moonfall Way
Columbia, MD 21044
P: 410-730-8865
rick.kutz@comcast.net
Lembeck, Larry
MDA/Mosquito Control
27722 Nanticoke Rd, #2
Salisbury, MD21801
P: 410-843-6626
lalembeck@yahoo.com
Lesser, Chris
DE Mosquito Control
1161 Airport Rd
Milford, DE 19963
P: 302-422-1512
Christopher, lesser® state.de. us
Lesser, Cyrus *
MD Dept of Agriculture
50 Harry S. Truman Pkwy
Annapolis, MD 21801
P: 410-841-5870
lessercr@mda.state.md.us
Lewandowski, Edward *
DE Center for the Inland Bays
467 Highway One
Lewes, DE 19958
P: 302-645-7325
director® inlandbays.org
Limpert, Roland
MD Dept of Nat Resources
Tawes State Office Bldg.
Annapolis, MD 21401
P: 410-260-8333
rlimpert@dnr.state.md.us
Magerr, Kevin
US EPA
1650 Arch Street
Philadelphia, PA 19104
P: 215-814-5724
Magerr.kevin@epa.gov
Matuszak, Diane
MD Dept of Health & Mental Hygiene
201 W.Preston St., #320
Baltimore, MD21201
P: 410-767-1255
dmatuszzak@dhmh. state, md. us
Mayer, George E. Jr.
Town of Federalsburg
PO Box 471
Federalsburg, MD21632
P: 410-754-8173
grantmainstreet@hotmail.com
McCabe, Chris
Worcester County
D.R.P. Sun/SEC
Snow Hill, MD21863
P: 410-632-1200x1143
mccabe@worcester.state.md.us
McNatt, Stacy
New Castle County Government
87 Reads Way
Newcastle, DE 19720
P: 302-395-5415
smcnatt@co.new-castle.de. us
Meadows, Bob
DNREC
1024 Old County Rd
Newark, DE 19202
P: 302-836-2558
robert.meadows@state.de. us
Meredith, William H.*
DE DNR - Mosquito Control Section
89 Kings Hwy
Dover, DE 19901
P: 302-739-3493
william.meredith@state.de.us
Moran, Thomas
DE Mosquito Control
2430 Old County Road
Newark, DE 19711
P: 302-836-2555, ext. 103
Thomas.moran@state.de.us
Moreno, David
Wicomico Co. Health Dept.
108 EMainSt
Salisbury, MD 221801
P: 410-546-4446
davem@dhmh.state.md.us
Munson, Katherine
Worcester Co. Comp Planning
Snow Hill, MD21863
P: 410-632-5651
kmunson@co.worcester.md.us
Newlin, Scott
DEDNR
89 Kings Hwy
Dover, DE 19901
P: 302-422-1512
Scott, newlin@state.de.us
Orth, Rebecca
DE Mosquito Control
2430 Old County Rd
Newark, DE 19402
P: 302-836-2555
Rebecca.orth@state.de.us
Palalay, Sal
DE Dept of Transportation
PO Box 778
Dover, DE 19901
P: 302-760-2191
Salvador.palalay@state.de.us
54
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Phipps-Dickerson, Mary
Wicomico Co. Health Dept.
108EMainSt
Salisbury, MD21801
P: 410-546-4446
marypd@dhmh.state, md.us
Possident, Tom
Worcester County Health Dept.
Snow Hill, MD21803
P: 419-352-3234
tomp@dhmd.state, md.us
Potetz, Ed
Worcester County Health Dept.
Snow Hill, MD21803
P: 410-352-3234
edp@dhmh.state.md. us
Rutherford, Jamie
DEDNREC
89 Kings Hwy
Dover, DE 19901
Jamie.rutherford@state.de. us
Sachs, Herb
MD Dept. Environment
1800 Washington Blvd
Baltimore, MD 21230
P: 410-537-3731
hsachs@mde. state, md. us
Sanghavi, Sonal
MD State Highway Admin.
707 N.Calvert Street
MS-C-201
P: 410-545-8414
ssanghavi@sha.state.md.us
Saveikis, David
Delaware Mosquito Control
1161 Airport Rd
Milford, DE 19963
P: 301-422-1512
David.saveikis@state.de.us
Schamberger, Dan
MDA-Mosquito Control
27722 Nanticoke Rd. #2
Salisbury, MD21801
P: 410-543-6626
dschamberger@ccisp.net
Schofield, Dave
MDA-Mosquito Control
27722 Nanticoke Rd #2
Salisbury, MD21801
P: 410-543-6626
dschofield@ccisp.net
Scott, Michael
Dept. of Geography and Geosciences
Salisbury Univ.
Salisbury, MD21801
P: 410-543-6456
msscott@salisbury.edu
Setting, Mary Ellen
MDA
50 Harry S. Truman Pkwy
Annapolis, MD21401
P: 410-841-5872
Settingm@mda.state.md.us
Shockley, Robert E.
Worcester County
DCAN Review
Snow Hill, MD21803
P: 410-632-1200, ext. 1141
Silaphone, Keota
Worcester County Dept of Comp. Plan
Snow Hill, MD21863
P: 410-632-5651
ksilaphone@co.worcester.md.us
Spagnolo, Ralph
US EPA
1650 Arch Street
Philadelphia, PA 19104
P: 215-0814-2718
Spagnolo.ralph@epa.gov
Stachurski, Dan
President, Ocean Pines Assoc.
60 Beaconhill Rd
Berlin, MD 21811
P: 410-208-9760
Danielbz@earthlink.net
Swan, Chris
Dept of Geography & Env Systems
UMBC
1000 Hilltop Circle
Baltimore, MD 21250
P: 410-455-3957
cmswan® umbc.edu
Tankersley, Roger
TVA
400 W. Summit Hill Dr.
Knoxville, TN 37902-1499
P: 865-632-79317
rdtankserley@tva.gov
Thornton, Kent *
FTN Associates
3 Innwood Circle
Suite 220
Little Rock, AR 72211
P: 501-225-7779
kwt@ftn-assoc.com
Tudor, Ed
Worcester County Gov.
1 Market Street
Snow Hill, 21863
P: 410-632-1200
ddrp® co.Worcester, md.us
Walch, Marianne
Delaware DOT
PO Box 778
Dover, DE 19903
P: 302-0760-2195
Marianne.walch@state.de.us
Wallis, Charlie *
MD Dept of the Environment
1800 Washington Blvd
Baltimore, MD 21230
P: 410-537-3543
cwallis@mde.state.md.us
Watson, Jessica
SCO
23818 Shortly Rd
Georgetown, DE 19947
P: 302-856-2105
Jessica.watson@state.de.us
Webb, Elaine Z.
DNREC
89 Kings Hwy.
Dover, DE 19901
P: 302-739-411
Elaine.webb@state.de.us
Zarebicki, Paul
DE Mosquito Control
1161 Airport Rd
Milford, DE 19963
P: 302-422-1512
Paul.zarebicki@state.de.us
* Steering Committee members
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Appendix C
Glossary
Activated Carbon: a highly adsorbent form of
carbon used to remove odors and toxic substances
from liquid or gaseous emissions. In waste
treatment, it is used to remove dissolved organic
matter from waste drinking water. It is also used in
motor vehicle evaporative control systems.
Adsorb: to gather (a gas, liquid, or dissolved
substance) on a surface in a condensed layer, as
when charcoal adsorbs gases. In other words,
adsorb means to store a substance on the surface of
something.
Adulticides: insecticides applied to kill adult
mosquitoes. Their use is an important part of an
effective mosquito management program, based on
mosquito surveillance information.
Aedes vexans: one of the most widespread pest
mosquitoes in the world. Aedes vexans is found in
every state in the U.S. including Alaska and Hawaii.
Virtually any transient water can support Ae. vexans
larvae, but rain pools in unshaded areas produce
the largest broods. The species is most common in
grassy pools that border wooded areas but specimens
can be encountered in partially shaded woodland
pools, roadside ditches, and vernal pools in open
fields on Delmarva Peninsula during summer, this
species is probably the major mosquito problem
originating from woodland pools.
Aggregate: term for the crushed stone or rock
needed to fill in an infiltration device such as a
trench or porous pavement. Clean-washed aggregate
is simply aggregate that has been washed clean so
that no sediment is included.
Anopheles quadrimaculatus: historically, this
mosquito is the most important vector of malaria
in North America and today is a major host of
the nematode that causes canine heartworm. This
species prefers habitats with well-developed beds
of submergent, floating leaf or emergent aquatic
vegetation. Larvae are typically found in sites with
abundant rooted aquatic vegetation, such as rice
fields and adjacent irrigation ditches, freshwater
marshes and the vegetated margins of lakes, ponds
and reservoirs.
Aqua-Swirl™ Concentrator: provides for the
removal of sediment (TSS) and free-floating oil
and debris. Swirl technology is a proven form of
treatment utilized throughout the stormwater and
wastewater industry.
Aquatic: relating to or consisting of or being in
water; "an aquatic environment."
Asphalt: a brownish-black solid or semisolid
mixture of hydrocarbons and other materials
obtained from native deposits or as a petroleum
byproduct, used in paving, roofing, and
waterproofing.
Assemblage: collection; several things grouped
together or considered as a whole.
Backswimmers: a tiny insect that is no more than
half an inch in length, spends its entire life in the
water, and with the exception of surfacing for air
most of that time is swimming on its back. Found in
the Hemiptera order of true bugs, the backswimmer
is part of the Notonectidae family. They can usually
be observed swimming just below the surface in
still waters such as those found in ponds, the calm
surfaces of some streams, lakes, swamps and small
fresh water inlets of some rivers. Backswimmers are
carnivorous, eating other insects, tadpoles, small fish
and crustaceans.
Bats: members of the mammalian order Chiroptera,
which means "winged hand." They represent our
only true flying mammals. Bats are not flying mice
or rats. In fact, they are not even closely related
to rodents. With the exception of only a very few
species of bats found in the Southwest that feed
on nectar, pollen and fruit, the 40 different bat
species of the U.S. feed exclusively on insects.
The species that are most commonly found around
urban communities are the "colonial bats", which
include the big brown bat, Eptesicusfiiscus, the
little brown batMyotis lucifugus, and the Mexican
free-tailed bat, Tadarida brasiliensis. Bats may be
both opportunistic and selective in their feeding,
and several factors are involved as to which specific
insects might be consumed in the greatest quantity.
In general, research has shown that the little brown
bat feeds on soft bodied insects such as moths, flies,
midges, mosquitoes and mayflies.
Bay Saver™ Separation System: a stormwater
treatment system that is designed to efficiently
and economically remove suspended solids,
hydrocarbons, debris and other pollutants from
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stormwater runoff. They have been installed across
the country and accepted by many communities and
watershed areas as the stormwater Best Management
Practice (BMP) device of choice.
Best Management Practice (BMP): methods
that have been determined to be the most effective,
practical means of preventing or reducing pollution
from non-point sources.
Biofiltration Swale (Bioswale): a long, gently
sloped, vegetated ditch designed to filter pollutants
from stormwater. Grass is the most common
vegetation, but wetland vegetation can be used if the
soil is saturated.
Bioretention Basins: landscaped depressions
or shallow basins used to slow and treat on-site
stormwater runoff. Stormwater is directed to the
basin and then percolates through the system where
it is treated by a number of physical, chemical and
biological processes. The slowed, cleaned water is
allowed to infiltrate native soils or directed to nearby
stormwater drains or receiving waters. Bioretention
basins are typically associated within small areas
of land with residential usage or with parking
lots where the islands become visually pleasing
stormwater treatment centers.
Bioretention: a water quality practice that utilizes
landscaping and soils to treat urban stormwater
runoff.
Bti (Bacillus thuringiensis ismelensis): is a
bacterium or bacterially-produced toxin that is
larvicidal for mosquitoes. Bacterial spores of Bti
must be actively ingested by mosquito larvae (rather
than acting as an external contact poison.
Chesapeake & Delaware Canal (C&D Canal):
one of only two commercially vital sea-level canals
in the United States. The C&D runs 14 miles long,
450 feet wide and 35 feet deep across Maryland
and Delaware, connecting the Delaware River with
the Chesapeake Bay and the Port of Baltimore. The
C&D Canal is owned and operated by the U.S. Army
Corps of Engineers, Philadelphia District.
Catch Basin (a.k.a., storm drain inlet, curb inlet):
an inlet to the storm drain system that typically
includes a grate or curb inlet where stormwater
enters the catch basin and a sump to capture
sediment, debris and associated pollutants. They are
also used in combined sewer watersheds to capture
floatables and settle some solids. Catch basins act
as pretreatment for other treatment practices by
capturing large sediments. The performance of catch
basins at removing sediment and other pollutants
depends on the design of the catch basin (e.g.,
the size of the sump), and routine maintenance to
retain the storage available in the sump to capture
sediment.
Catch Basin Inserts: used to filter runoff entering
the catch basin. The most frequent application for
catch basin inserts is for reduction of sediment, oil,
and grease in stormwater runoff.
Cattail: tall erect herbs with sword-shaped leaves;
cosmopolitan in fresh and salt marshes.
CDS (Continuous Deflective Separation): a
technology developed to meet a community demand
for an effective method of removing gross pollutants
from stormwater. The Continuous Deflective
Separation (CDS) technology overcomes the
clogging, reduced efficiency and capacity problems
experienced by direct filtration systems by using
controlled fluid flows through a non-blocking screen.
Certified Construction Reviewer (CCR): an
individual who has passed an approved training
course and who provides on-site construction review
for sediment control and stormwater management in
accordance with state stormwater regulations.
Channel: a passage for water (or other fluids) to
flow through; "the fields were crossed with irrigation
channels"; "gutters carried off the rainwater into a
series of channels under the street."
Chloride Ion: formed when the element chlorine
picks up one electron to form the anion (negatively
charged ion) Ch The salts of hydrochloric acid HC1
contain chloride ions and are also called chlorides.
An example is table salt, which is sodium chloride
with the chemical formulaNaCl. In water, it
dissolves into Na+ and Cl~ ions. Although chloride
is a naturally occurring element, it also reflects as a
contaminant of human use.
Clean Water Act: legislation that provides statutory
authority for the NPDES program; Public law 92-
500; 33 U.S.C. 1251 et seq. Also known as the
Federal Water Pollution Control Act.
Coastal Plain: an area of relatively low land of
variable width lying between uplands and the sea.
The Mid-Atlantic Coastal Plain extends inland
from the Atlantic Ocean, south of Long Island, to
the Fall Line, where the hilly Piedmont begins. It is
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arbitrarily separated from the South Atlantic Coastal
Plain at the Virginia-North Carolina border (with
the exception of the Great Dismal Swamp in the
southeast corner of Virginia, which is grouped in the
southern area). The area was formed by shifting sea
levels and alluvial deposition from rivers draining
mountains to the west. Water continues to be a
dominant feature of the landscape, creating forested
wetlands and salt marsh and shaping barrier island
and bay complexes. Upland forests on the remaining
land graded in composition from pine dominated
areas on the outer Coastal Plain (nearer the coast)
to hardwood forests on the inner Coastal Plain. This
was the site of the first successful English settlement
in North America, and the natural landscape has
been altered by European culture for nearly four
centuries.
Collection Basin: storm water from roads, parking
lots, etc., is drained.
Compost: the relatively stable humus material that
is produced from a composting process in which
bacteria in soil mixed with garbage and degradable
trash break down the mixture into organic fertilizer.
Concrete: a mixture of sand, coarse aggregate
(crushed gravel or crushed stone), Portland cement
and water correctly called Portland cement concrete.
The wet mixture is placed in a form or trench and
dries to a hard material.
Conservation Site Design: a method that requires
dwelling units to be clustered (grouped) on smaller
lots on a select part of the parcel, thus, leaving
a portion of the parcel as dedicated open space.
Conservation Design for Stormwater Management
places less emphasis on structural stormwater
practices—such as large ponds and sand filters—
and emphasizes site design that reduces impervious
areas. Conservation Design approaches also
highlight the value of a water-budget approach to
site design where recharge of rainfall is a primary
design consideration.
Constructed Wetlands: wetlands that are created
by humans, sometimes in places where there were
no wetlands before. These constructed wetlands
mimic nature by mechanically filtering, chemically
transforming, and biologically consuming potential
pollutants in the wastewater stream.
Coquilletidiaperturbans: a mosquito associated
with cattail marshes as well as other emergent
freshwater vegetation. The submerged larvae attach
themselves to the stems and roots of the emergent
vegetation and obtain oxygen from them. When
disturbed the pupae and larvae will burrow into the
mud. This behavior makes control of the larvae of
this species very difficult.
CREP (Conservation Reserve Enhancement
Program): focuses on protecting water quality
and improving wildlife habitat through the planting
of forested buffers in pasture or cropland next to
streams and ponds. CREP shares the cost of fencing
and other practices needed to exclude livestock from
the buffer zone, preventing erosion and filtering out
sediment, nutrients and other forms of pollution in
stormwater runoff. In addition, the program shares
the cost of establishing water sources in pastures
and planting hardwood trees and shrubs in buffer
zones. Finally, the CREP program makes rental
payments on contracted acres for 10 or 15 years as
well as providing financial incentive payments to the
landowner for agreeing to set aside the land in the
buffer zone for the term of the contract.
Culex restuans: a common mosquito in the eastern
and central United States. Culex restuans utilizes
an exceptionally wide range of larval habitats. The
types of water used by this species can vary from
nearly clear to grossly polluted. A partial list of
larval habitats includes: temporary ground water,
the edge of grassy swampland, sphagnum bogs, road
side ditches, tire ruts, hoof prints, discarded buckets,
tires, catch basins, sewage effluent and septic
seepage. Some consider them as troublesome biters,
although others say they rarely bite humans. Flight
range 1 to 2 miles. May transmit Western Equine
Encephalitis.
Culex salinarius: a widespread mosquito
(facultative avian feeder) that reaches greatest
abundance along the Atlantic and Gulf Coasts of the
U.S. Larvae are found in fresh or brackish water and
salt marshes that contain a great deal of emergent
and decaying vegetation. Impoundments have been
shown to be an excellent source of Cx. salinarius.
Adult females of the species host seek within the
first 2 or 3 hours after sunset, but may be active
in non host-seeking pursuits just prior to sunrise.
Studies have also indicated that Cx. salinarius
appear to be most abundant at elevations of 20 ft.
or more. In addition, they are indiscriminate in their
bloodmeal preferences, and are efficient vectors of
St. Louis encephalitis (SLE) and in the Mid-Atlantic
region are also vectors for West Nile virus.
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Dam: barrier to confine or raise water for storage
or diversion, to create a hydraulic head, to prevent
gully erosion, or for retention of soil, sediment or
other debris.
Depressional Wetlands: occur in topographic
depressions that have closed contours on three sides.
Elevations within the wetland are lower than in the
surrounding landscape. The shapes of depressional
wetlands vary, but in all cases the movement of
surface water and shallow subsurface water is
toward the lowest point in the depression. The
depression may have an outlet, but the lowest point
in the wetland is somewhere within the boundary,
not at the outlet.
Detention: the collection and temporary storage of
stormwater, generally for a period of time ranging
from 24 to 72 hours, to provide for treatment
through primarily physical, biological, and—to
a much lesser degree—chemical processes with
subsequent gradual release of stormwater to
downstream receiving waters.
Detention Basins: structures which are built to
detain precipitation for short periods. They are
normally dry, but are designed to detain surface
water temporarily during, and immediately after a
runoff event. Their primary function is to attenuate
the storm flows by releasing flows at a lower flow
rate. There are no gates or valves allowed on the
outlet so that water can never be stored on a long-
term basis. By design and unless reflooded or further
inundated, detention basins should go completely
dry within 24-72 hours of a rewetting or refilling
event.
Ditching: digging a path for water that drains the
surrounding land and alters naturally existing water
flow through the area.
Downstream Defender™: a treatment device
engineered to capture settleable solids, floatables,
oil and grease from stormwater runoff. It is one
of the family of advanced Hydrodynamic Vortex
Separators provided by HIL Technology, Inc. that
augments gravitational forces with complex but
stabilized vortex forces to maximize solids/liquids
separation. The result is a compact separator that
requires a smaller land area than conventional
gravitational sedimentation. A floatables trap is
incorporated within the same vessel.
Dragonfly: an insect belonging to the Order
Odonata, and characterized by large multifaceted
eyes, two pairs of strong transparent wings, and
an elongated body. Dragonfy adults typically eat
mosquitoes, midges and other small insects like flies,
bees, and butterflies. They are usually found around
lakes, ponds, streams, and wetlands for the reason
that their larvae (known as naiads) are aquatic;
dragonfly larvae will consume mosquito larvae.
Dragonflies do not bite or sting humans.
Dry Ponds: are stormwater basins that are designed
to intercept a volume of stormwater runoff and
temporarily impound the water for gradual release
to the receiving stream or storm sewer system and
as such, are also known as detention ponds. Dry
ponds are typically on-line, end-of-pipe BMPs. Dry
ponds are designed to completely empty out between
runoff events (by design within 24-72 hours), and
therefore provide mainly runoff rate control as
opposed to water quality control. Dry ponds can
provide limited settling of particulate matter, but a
large portion of this material can be resuspended
by subsequent runoff events. Therefore, dry ponds
should be considered mainly as practices used to
reduce the peak discharge of stormwater to receiving
streams to limit downstream flooding and to provide
some degree of channel protection while also
providing some limited water quality benefits.
Duckweed: any small or minute aquatic plant of the
family Lemnaceae that float on or near the surface of
shallow ponds.
Eastern Equine Encephalitis (EEE): is spread
to horses and humans by infected mosquitoes. It
is among the most serious of a group of mosquito-
borne arboviruses that can affect the central nervous
system and cause severe complications and even
death. EEE is found in North America, Central and
South America, and the Caribbean. It has a complex
life cycle involving birds and specific types of
mosquitoes that cycle EEE among birds including
several Aedes, Ochlerotatus and Culex species and
Culiseta melanura. Other types of mosquitoes, in
particular Ochlerotatus, Aedes and Coquilletidia
species are known as "bridge vectors" for EEE, in
that they might first feed upon an EEE-infected bird,
and then take a subsequent bloodmeal from humans
or horses, passing EEE on to these mammals. EEE
is a virulent arbovirus, and humans who contract
EEE are fortunate if their symptoms range from
none at all to only a mild flu-like illness with fever,
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headache, and sore throat. More serious infections
of the central nervous system lead to a sudden fever
and severe headache followed quickly by seizures
and coma, with children and the elderly most prone
to more severe cases. About a third of these patients
die from the disease. Of those who survive, many
suffer permanent brain damage and require lifetime
institutional care. There is no specific treatment. A
vaccine is available for horses, but not humans.
Eastern Shore of Maryland: the eastern side of the
Chesapeake Bay. The region is characterized by tiny
historic towns, meandering creeks, beautiful natural
areas, crabs and clams.
Ecological Function: the role that any process,
species, population, or physical attribute plays
in the interrelation among living or non-living
components of ecosystems. Ecological functions
include hydrologic transfers and storage of
water, biogeochemical transformations, primary
productivity, decomposition, and the ability to
provide habitats for dependent species and the
diversity of species and organization they support.
Ecological Value: a measure of the significance or
interest of an area as a habitat supporting species of
flora and fauna.
Efficacy: the ability to produce an effect, usually a
specifically desired effect.
Embankment: a structure of earth, gravel, or
similar material raised to form a pond bank or
foundation for a road.
Emergent: a type of plant rooted in shallow water
but supporting stems and leaves that reach and
grow up out of the water; cattails and arrowhead are
emergent plants.
Encephalitis: a viral disease transmitted by infected
mosquitoes. It affects the central nervous system
causing fever and depending upon the form of
encephalitis, can often be fatal. The youngest and
oldest segments of the population are usually the
most susceptible. Many viruses cause encephalitis
and occur in the U.S. every year. Three different
encephalitides occur in Maryland: Eastern equine
encephalitis (EEE), West Nile encephalitis (WNE),
and St. Louis encephalitis (SLE). The former is
fatal in about a third of all infections while fatality
rates for WNE and SLE are much lower. These
viral diseases have three cycles. The first is the
maintenance cycle in the wild reservoir hosts (birds);
the second, an amplifying cycle in a susceptible
domestic or wild host (domestic animals or birds);
and the third may affect the human population or
horses. Humans who become infected with EEE,
WNE, or SLE do not have enough of the virus in
their blood to infect other mosquitoes that bite them.
Endangered Species Act (ESA): provides a
program for the conservation of threatened and
endangered plants and animals and the habitats in
which they are found. The U.S. Fish and Wildlife
Service of the Department of the Interior maintains
the list of endangered species and threatened
species. Species include birds, insects, fish, reptiles,
mammals, crustaceans, flowers, grasses, and trees.
Anyone can petition FWS to include a species on
this list. The law prohibits any action, administrative
or real, that results in a "taking" of a listed species,
or adversely affecting habitat. Likewise, import,
export, interstate, and foreign commerce of listed
species are all prohibited.
Energy Dissipater: a rock or concrete structure
designed to reduce the velocity of the flow exiting
a culvert to prevent erosion of the streambed and
banks.
Entomologists: scientists who study insects.
Environmentally Sensitive Design (ESD):
practices that attempt to limit impervious cover
or pavement, and protect or create green/open
space at the site level. Site design practices include
minimizing street widths, reducing set backs,
adopting smaller lot sizes or clustering housing
units.
Erosion: the wearing away of land surface
by wind or water, intensified by land-clearing
practices related to farming, residential or industrial
development, road building, or logging.
Evaporation: the process by which a liquid
changes into a gas.
Excavate: the process of digging out or around
something.
Exotic Disease: any disease believed to be
historically absent from the U.S. and its territories
that has a potential significant health or economic
impact.
Fill: man-made deposits of natural soils or rock
products and waste materials.
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Filter Strip: strip or area of vegetation used for
removing sediment, organic matter, and other
pollutants from runoff and wastewater.
Food Webs: the interconnected feeding
relationships in an ecosystem. These relationships
can be complex; some organisms may feed on
more than one trophic level, or changes may occur
depending on a species' life history stages or the
availability of food.
Forebay: an extra storage area provided near an
inlet of a BMP to trap incoming sediments before
they accumulate in a pond BMP.
Gambusia holbrooki (niosquitofish): a species
of freshwater fish. It is a member of the family
Poeciliidae of order Cyprinodontiformes. It is
important in mosquito control, with G. holbrooki
being the native mosquito fish of the eastern U.S.
along the Atlantic and Gulf coasts (G. qffinis is a
more western and inland species of niosquitofish that
should no longer be introduced or used for mosquito
control along the Atlantic or Gulf coasts).
Genera: in biology, a genus (plural genera) is a
grouping in the classification of living organisms
having one or more related and morphologically
similar species. In the common binomial
nomenclature, the name of an organism is composed
of two parts: its genus (always capitalized) and a
species modifier. An example is Homo sapiens, the
name for the human species which belongs to the
genus Homo.
Geomorphic: relating to the way the land is formed
(rock, soil, and water).
Grade: to finish the surface of a canal bed, roadbed,
top of embankment, or bottom of excavation, or
other land area to a smooth, even condition.
Gravel: 1) aggregate consisting of mixed sizes of
1/4 inch to 3 inches which normally occur in or
near old streambeds and have been worn smooth by
the action of water. 2) a soil having particle sizes,
according to the Unified Soil Classification System,
ranging from the No. 4 sieve size, angular in shape,
as produced by mechanical crushing.
Gravity and/or Swirl Separators: a group of
stormwater treatment technologies that includes
a wide variety of proprietary devices that have
been developed in recent years. These devices
are modifications of traditional oil/particle
separators that commonly rely on vortex-enhanced
sedimentation for pollutant removal. They are
designed to remove coarse solids and large oil
droplets and consist primarily of cylindrical-shaped
devices that are designed to fit in or adjacent to
existing stormwater drainage systems. In these
structures, stormwater enters as tangential inlet flow
into the cylindrical structure. As the stormwater
spirals through the chamber, the swirling motion
causes the sediments to settle by gravity, removing
them from the stormwater. Some devices also have
compartments or chambers to trap oil and other
floatables.
Green Infrastructure: the ecological processes,
both natural and engineered, that act as the natural
infrastructure. It includes ditches, creeks, wetlands,
parks, open space, trees, green roofs, gardens,
working lands, aquifers and watersheds that supply
drinking water.
Ground Water: the supply of fresh water found
beneath the Earth's surface, usually in aquifers,
which supply wells and springs. Because ground
water is a major source of drinking water, there is
growing concern over contamination from leaching
agricultural or industrial pollutants or leaking
underground storage tanks.
Groundwater Discharge: the flow or pumping of
water from an aquifer.
Groundwater Recharge: the natural process of
infiltration and percolation of rainwater from land
areas or streams through permeable soils into water-
holding rocks that provide underground storage (i.e.,
aquifers).
Habitat: the place where a population (e.g.,
human, animal, plant, microorganism) lives and its
surroundings, both living and non-living.
Homeowners' Association: a group that governs a
subdivision, condominium, or planned community.
The association collects monthly fees from all
owners to pay for common area maintenance, handle
legal and safety issues, and enforce the covenants,
conditions, and restrictions set by the developer. It
operates under authority of state laws.
Hydrocarbons (HC): chemical compounds that
consist entirely of carbon and hydrogen.
Hydrodynamics: that part of the science of
mechanics which deals with the dynamics of water
and of the effects of the motion of water past bodies
on its surface or immersed in it.
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Hydrogeomorphic Classification: emphasizes the
hydrologic and geomorphic controls that influence
many wetland functions. The HGM Approach
focuses on the location of a wetland in a watershed
(its geomorphic setting), its sources of water, and its
hydrodynamics. The HGM approach first classifies
wetlands based on their differences in functioning,
second it defines functions that each class of wetland
performs, and third it uses reference to establish
the range of functioning of the wetland. A series of
geographically based models or "functional profiles"
for various wetland types are being created for
use in functional assessments. The classification
is designed for onsite application and requires
considerable field effort for model development. The
HGM models could help broaden our understanding
of the range in performance of selected functions by
different wetland types.
Impervious: not capable of being passed through,
damaged, or disturbed. Water is not able to flow
through impervious surfaces, such as asphalt roads
and concrete sidewalks.
Impervious Surface: a hard surface area which
either prevents or retards the entry of water into
the soil mantle as under natural conditions prior
to development; and/or a hard surface area which
causes water to run off the surface in greater
quantities or at an increased rate of flow from
the flow present under natural conditions prior to
development. Common impervious surfaces include,
but are not limited to, rooftops, walkways, patios,
driveways, parking lots or storage areas, concrete
or asphalt paving, gravel roads, packed earthen
materials, and oiled, macadam, or other surfaces
which similarly impede the natural infiltration of
surface and stormwater runoff. Open, uncovered
flow control or water quality treatment facilities
shall not be considered impervious surfaces for
determinations of thresholds. For the purpose of
modeling though, onsite flow control and water
quality ponds are modeled as impervious surface per
Chapter 3 of the King County Surface Water Design
Manual.
Infiltration: 1) the penetration of water through
the ground surface into sub-surface soil or the
penetration of water from the soil into sewer or
other pipes through defective joints, connections, or
manhole walls. 2) the technique of applying large
volumes of waste water to land to penetrate the
surface and percolate through the underlying soil.
Infiltration basin: the holding of runoff in a basin
without release except by means of evaporation,
infiltration, or emergency bypass.
Integrated Mosquito Management Methods: an
effective and environmentally sensitive approach
used to manage mosquitoes, relying upon a
combination of scientific knowledge and common
sense. The practice of an integrated mosquito control
program requires that a number of parameters
must be included in the decision making process,
including: current, comprehensive information
about the life cycles of the numerous mosquito
species inhabiting a given area, and the interaction
of those mosquitoes with people, other animals
and the surrounding environment; a knowledge of
mosquito BMPs, including but not limited to source
reduction, mosquito habitat modification and the use
of biological and/or chemical products to control
larval and adult mosquitoes; mosquito control
decisions based upon surveillance results, habitat
inspections and a rigorous sanitation program; and
a strong educational component for staff members
and the community at large that emphasizes the
elimination of potential sources of public health
nuisances and possible disease transmission.
Integrated Pest Management (IPM): based
on ecological, economic and social criteria and
integrates these multidisciplinary methodologies
to develop pest management strategies that are
practical and effective to protect public health and
the environment.
Interstices: spaces, especially small or narrow
ones, between things or parts (e.g., the tiny spaces
within streambed sediments).
Invasive Species: introduced by human action
to a location, area, or region where it did not
previously occur naturally (i.e., is not native). These
species become capable of establishing a breeding
population in the new location without further
intervention by humans, and become pests in the
new location, threatening local biodiversity.
Invertebrate: an animal without a backbone.
Invertebrates include insects, arachnids (spiders
& ticks), gastropods (snails & slugs), crustaceans
(crayfish & isopods), centipedes, worms, and others.
Land Use: the way land is developed and used in
terms of the types of activities allowed (agriculture,
residences, industries, etc.) and the size of buildings
and structures permitted. Certain types of pollution
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problems are often associated with particular land
uses, such as sedimentation from construction
activities.
Landform: any feature of Earth's surface having a
distinct shape and origin. Landforms include major
features (such as continents, ocean basins, plains,
plateaus, and mountain ranges) and minor features
(such as hills, valleys, slopes, drumlins, floodplains,
and dunes). Collectively, the landforms of Earth
constitute the entire surface configuration of the
planet.
Landscape Connectivity: the degree to which
the structure of a landscape helps or hinders the
movement of wildlife species. A landscape is
considered "well connected" when organisms (or
natural processes) can readily move among habitat
patches over the long term.
Larvae: immature, often wormlike stage of insect
development, after the egg and before the pupa
(cocoon) and adult. Larvae is the plural; larva is the
singular.
Larvicide: a class of pesticides used to kill insect
larvae and other immature forms (nymphs). Usually
refers to insecticides used for controlling mosquito
larvae, but also to chemicals for controlling
caterpillars on crops.
Life Cycle: the natural process of stages that an
organism goes through as it ages. For example,
human stages are birth, infant, toddler, kid, pre-
teen, teenager, young adult, adult and death. Insects
go through a life cycle that begin with the egg and
eventually result in the adult form. Mosquitoes,
butterflies, and moths go through complete
metamorphosis, with four different life stages:
the egg, larva (caterpillar), pupa, and adult. Other
insects undergo incomplete metamorphosis, where
the juvenile (the nymph) is not very different from
the adult form.
Localized: confined or restricted to a particular
location.
Low Impact Development (LID): has emerged
as a highly effective and attractive approach to
controlling stormwater pollution and protecting
developing watersheds and already urbanized
communities throughout the country. Instead
of large investments in complex and costly
engineering strategies for stormwater management,
LID strategies integrate green space, native
landscaping, natural hydrologic functions, and
various other techniques to generate less runoff from
developed land. LID is different from conventional
engineering. While most engineering plans pipes
water to low spots as quickly as possible, LID uses
micro-scale techniques to manage precipitation as
close to where it hits the ground as possible. This
involves strategic placement of linked lot-level
controls that are "customized" to address specific
pollutant load and stormwater timing, flow rate, and
volume issues. One of the primary goals of LID
design is to reduce runoff volume by infiltrating
rainfall water to groundwater, evaporating rain water
back to the atmosphere after a storm, and finding
beneficial uses for water rather than exporting it
as a waste product down storm sewers. The result
is a landscape functionally equivalent to pre-
development hydrologic conditions, which means
less surface runoff and less pollution damage to
lakes, streams, and coastal waters.
Ludwigia species (water primrose, primrose
willow): a perennial herb that can be found creeping
along the shoreline, floating on the water surface,
or growing upright. It is a robust plant with bright
yellow, showy flowers and willow-like leaves. It is
a non-native species originally from South America
and the southern U.S. and has been introduced into
Europe and northern North America. It favors the
margins of lakes, ponds, ditches, and streams. These
plants are very invasive and aggressive and will
form very dense mats of vegetation.
Marsh: a type of wetland, featuring grasses,
rushes, reeds, cattails, sedges, and other herbaceous
plants (possibly with low-growing woody plants
or shrubs) in a context of shallow water. A marsh
is different from a swamp, which is dominated by
trees rather than grasses and low herbs. The water
of a marsh can be fresh, brackish, or saline. Coastal
marshes may be associated with estuaries and along
waterways between coastal barrier islands and the
inner coast.
Media: specific environments—air, water, soil—
which are the subject of regulatory concern and
activities.
Metals: an element that readily forms ions (cations)
and has metallic bonds. Metals are sometimes
described as a lattice of positive ions (cations) in
a cloud of electrons. The metals are one of the
three groups of elements as distinguished by their
ionization and bonding properties, along with the
metalloids and nonmetals. On the periodic table, a
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diagonal line drawn from boron (B) to polonium
(Po) separates the metals from the nonmetals.
Methoprene: an insecticide that inhibits the growth
of certain insects in their immature or larval and
pupal stages. When mosquito larvae are exposed to
methoprene, they do not immediately die. The effect
of the product usually shows in the pupal stage. In
this stage, without exposure to methoprene, the
immature mosquitoes normally develop into adult
insects and immerge to start their biting, reproducing
life cycle. However, the young insects that have
come in contact with methropene will not survive
past the pupal stage and never become adult biting
pests.
Metropolitan Area: a large population nucleus,
together with adjacent communities having a high
degree of social and economic integration with that
core. Metropolitan areas comprise one or more entire
counties.
Micropool: a smaller permanent pool used in a
stormwater pond due to extenuating circumstances,
i.e., concern over the thermal impacts of larger
ponds, impacts on existing marshes, or lack of
topographic relief.
Mid-Atlantic States: the Mid-Atlantic region of
the U.S., located in the northeastern section of the
country, includes the following states and district:
Delaware, Maryland, New Jersey, Pennsylvania,
Virginia, and Washington, D.C. Sometimes on the
northern end, New York is added to this region,
sometimes on the western end, West Virginia is
added, and sometimes on the southern end, North
Carolina is added.
Mitigation: measures taken to reduce adverse
impacts on the environment. These measures might
involve taking actions to avoid adverse impacts, or
taking steps to reduce adverse impacts, or taking
actions to help compensate for any adverse impacts
that could not be avoided or lessened.
Mosquito Abundance: the number of mosquitoes
relative to a particular area.
Mosquitoes: members of the family Culicidae in
the order Diptera (true flies). Adult mosquitoes are
distinguished from other flies by the presence of a
long proboscis and scales on the margins and veins
of the wing. Males differ from females by having
feathery antennae and mouthparts not suited for
piercing skin. Mosquitoes are the most prominent
bloodsucking insects that as a group, annoy humans
and other warm-blooded animals. Not only are their
bites (and subsequent itching welts) annoying, but
mosquitoes can transmit several serious diseases
to humans and animals, including malaria, yellow
fever, dengue fever, filariasis, several types of
encephalitis viruses and canine heartworm.
Naiad: the immature, or nymph, stage of some
aquatic insects, such as dragonflies, that undergo
incomplete metamorphosis; these organisms have
three life stages: egg, naiad, adult; the naiad looks
entirely different from the adult.
National Pollutant Discharge Elimination System
(NPDES): a provision of the Clean Water Act
which prohibits discharge of pollutants into waters
of the U.S. unless a special permit is issued by EPA,
a state, or, where delegated, a tribal government on
an Indian reservation.
National Wetlands Inventory (NWI): produces
information on the characteristics, extent, and status
of the Nation's wetlands and deepwater habitats.
Nutrient: any substance assimilated by living
things that promotes growth. The term is generally
applied to nitrogen and phosphorus in wastewater,
but is also applied to other essential and trace
elements.
Ochlerotatus japonicus: an invasive mosquito
species that has been found with WNV and is
capable of transmitting the virus. It is difficult
to sample and does not appear to be particularly
aggressive. Its importance, or lack thereof, as a
vector is not yet understood. It is not known to be
an EEE vector. Ochlerotatus japonicus are found
in rock pools, tree holes and containers. They over
winter in the larval stage and could be among first
larvae collected in spring. The adults are active
during the day and will bite humans. They are
attracted to carbon dioxide, and have a flight range
up to 600 feet.
Offline: a type of pond design where the design
treatment volume is diverted offline to a treatment
pond by a control structure. When the offline pond
becomes full, the remaining runoff bypasses the
pond. This approach allows for the segregation of
the "first flush" of runoff, which may contain the
majority of pollutants.
Online: a type of design where all of the runoff
from a storm routes through a pond. This method
may have a lower pollutant removal efficiency than
offline ponds if the pond volume is not large enough
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to hold all the runoff from a significant rain event.
This is because the most polluted volume is mixed
with the remainder storm volume, and excess flows
dilute the concentrations and leave the pond with
the mixed polluted water. If the online pond is sized
properly, it can treat the entire runoff volume.
Open Space: a portion of a site which is
permanently set aside for public or private use and
will not be developed. The space may be used for
passive or active recreation, or may be reserved to
protect or buffer natural areas.
Organic: 1) referring to or derived from living
organisms. 2) in chemistry, any compound
containing carbon.
Orthophosphate: a commonly used corrosion
inhibitor that is added to finished drinking water.
Orthophosphate works by forming a protective
coating inside of pipes in the distribution system and
in customer homes to prevent lead from leaching
into drinking water.
Outfall: the place where effluent is discharged into
receiving waters.
Outlet: the point at which water discharges from
such things as a stream, river, lake, tidal basin, or
pipe.
Pavers: bricks in numerous sizes and shapes that
are used for constructing sidewalks, patios, and
driveways.
Peat: an accumulation of partially decayed
vegetable matter. Peat forms in wetlands.
Percolate: to drain or seep through a porous
substance (e.g., when water passes through the
grains of soil).
Peri-urban: low density housing and road
development on the periphery of urban areas, still
retaining small areas of rural land within networks
of suburban building.
Permit: an authorization, license, or equivalent
control document issued by EPA or an approved
state agency to implement the requirements of an
environmental regulation; e.g., a permit to operate
a wastewater treatment plant or to operate a facility
that may generate harmful emissions.
Pesticide: substances or mixture there of intended
for preventing, destroying, repelling, or mitigating
any pest. Also, any substance or mixture intended
for use as a plant regulator, defoliant, or desiccant.
Phosphorus: an essential chemical food element
that can contribute to the eutrophication of lakes
and other water bodies. Increased phosphorus levels
result from discharge of phosphorus-containing
materials into surface waters.
Phragmites: a tall invasive reed that colonizes the
edges of salt marshes and can replace low-lying salt-
tolerant grass species.
Pollutant: Generally, any substance introduced into
the environment that adversely affects the usefulness
of a resource or the health of humans, animals, or
ecosystems.
Polymeric Materials: materials composed of large
molecules, generally based on carbon, that have
been formed from the chemical bonding of smaller
units (monomers). Commonly known as plastics.
Pond Inlet: an opening through which stormwater
enters a pond.
Pond: a still body of water smaller than a lake,
often shallow enough for rooted plants to grow
throughout.
Porous pavement: an alternative to conventional
pavement whereby runoff is diverted through
a porous asphalt layer and into an underground
tone reservoir. The stored runoff then gradually
infiltrates into the subsoil. Porous pavement is not
recommended for use in areas with high water table
conditions.
Predation: predation is an interaction between
organisms (animals) in which one organism captures
and feeds upon another called the prey.
Public Health: one of the efforts organized by
society to protect, promote, and restore the people's
health, involving a combination of sciences,
skills, and beliefs directed to the maintenance
and improvement of health through collective or
social actions. A social institution, a discipline,
and a practice with the goal to reduce the amount
of disease, premature death, and disease-produced
discomfort and disability in the population.
Putative: commonly put forth or accepted as true
on inconclusive grounds; "the foundling's putative
father"; "the reputed (or purported) author of the
book"; "the supposed date of birth".
Rats: small nearly omnivorous rodents of the genus
Rattus, which comprises 56 different species of
what are commonly known as the Old World Rats
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or true rats originating in Asia. Rats are bigger than
their relatives the mice, but seldom weigh over 500
grams.
Real Time: events that happen in real time are
happening virtually at that particular moment. When
you chat in a chat room or send an instant message,
you are interacting in real time since it is immediate.
Recovery Time: the length of time required for the
design treatment volume in a pond to subside to the
normal water level or bottom of the pond. This time
should normally be between 24 and 72 hours. This
recovery may be accomplished by either infiltration
or controlled release through an outfall structure.
Reeds: tall grass with hollow stems, often found in
or near water.
Residential: land use that is primarily for houses,
townhouses, apartments or other dwelling types.
Resmethrin: a type of pyrethroid insecticide.
Pyrethroids are synthetic versions of a natural
insecticide produced by chrysanthemum flowers.
Resmethrin is not very toxic to mammals, but it is
highly toxic to bees and fish.
Retention: onsite storage of storm water with
subsequent disposal by infiltration into the ground
or evaporation to prevent direct discharge of
stormwater runoff into receiving waters. They
usually contain some water permanently.
Riparian Habitat: areas adjacent to rivers and
streams with a differing density, diversity, and
productivity of plant and animal species relative to
nearby uplands.
Riprap: broken stone, cut stone blocks, or rubble
that is placed on slopes to protect them from erosion
or scour caused by flood waters or wave action.
Run-off: that part of precipitation, snow melt, or
irrigation water that runs off the land into streams or
other surface-water. It can carry pollutants from the
air and land into receiving waters.
Rushes: grass-like plants growing in wet places and
having cylindrical often hollow stems.
Salamander: the common name applied to
approximately 500 amphibian vertebrates with
slender bodies, short legs, and long tails (order
Caudata or Urodela). The moist skin of the
amphibians limits them to habitats either near water
or under some protection on moist ground, usually
in a forest. Some species are aquatic throughout life,
some take to the water intermittently, and some are
entirely terrestrial as adults.
Salt Marsh: a low coastal grassland that is
regularly or irregularly covered by tidal water. Salt
marshes are found on the edges of estuaries; places
where a river flows into the ocean. In the marsh, the
water flows very slowly so sediments are dropped
from the water and build up a muddy environment
where plants can grow and small animals can live.
Sand: a soil particle between 0.05 and 2.0
millimeters in diameter.
Sedges: a group of grass-like, herbaceous plants
that, unlike grasses, have unjointed stems. Stems are
usually solid and often triangular in cross section.
Sediment: topsoil, sand, and minerals washed from
the land into water, usually after rain or snow melt.
Sedimentation Chamber: where the heavy
pollutant particles settle out of stormwater.
Silt: sedimentary materials composed of fine or
intermediate-sized mineral particles.
Soil Horizon: a layer of soil that can be
distinguished from the surrounding soil by such
features as chemical composition, color, and texture.
Source Reduction: reducing the amount of
materials entering the waste stream from a specific
source by redesigning products or patterns of
production or consumption (e.g., using returnable
beverage containers). Synonymous with waste
reduction.
Species: 1) a reproductively isolated aggregate of
interbreeding organisms having common attributes
and usually designated by a common name. 2) an
organism belonging to belonging to such a category.
Spillway: an open or closed channel, or both, used
to convey excess water from a reservoir.
Stabilization: providing vegetative and/or
structural measures that will reduce or prevent
erosion.
Stabilized: made stable or firm.
Stagnant: a body of water which is motionless or
ceases to flow.
Storm Drain: an opening leading to an under-
ground pipe or open ditch for carrying surface
runoff, separate from the sanitary sewer or
wastewater system.
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Stormceptor® Oil and Sediment Separator
for Stormwater Runoff and Spill Control: an
engineered Stormwater treatment structure that
removes oil and sediment from storm runoff.
Comprised of a round precast concrete tank and
fiberglass partition, the patented Stormceptor
replaces a maintenance hole in the storm sewer. By
capturing oil spills and suspended solids, the system
prevents non-point source pollution from entering
downstream lakes and rivers. In the Stormwater
management industry it is commonly referred to
as an: Oil-grit separator or Oil and grit separator
(OGS), or Oil-sediment separator, or Oil and
sediment separator (OSS).
Stormwater: precipitation that accumulates in
natural and/or constructed storage and Stormwater
systems during and immediately following a storm
event.
Stream Channel: the bed where a natural stream of
water runs or may run; the long narrow depression
shaped by the concentrated flow of a stream and
covered continuously or periodically by water.
Submergent: a wetland plant that has adapted to
grow underwater.
Substrate: the surface or medium (e.g., rock,
sand, mud, pilings, shells) that serves as a base for
something.
Suburban: relating to, characteristic of, or situated
in suburbs. Suburbs are inhabited districts located
either on the outer rim of a city or outside the official
limits of a city.
Sumithrin (Anvil): a pyrethroid-based pesticide
registered for use in mosquito control by EPA. It
is effective against adult mosquitoes, including the
Culex species, which transmitted West Nile virus.
Anvil is registered for use against mosquitoes
in swamps, marshes, outdoor residential and
recreational areas. It has low toxicity to humans,
mammals, and the environment.
Sump: a pit or tank that catches liquid runoff for
drainage or disposal.
Surveillance: the systematic collection, analysis,
interpretation, and dissemination of data.
Suspended Solids: small particles of solid
pollutants that float on the surface of, or are
suspended in, sewage or other liquids. They resist
removal by conventional means.
Swale: an elongated depression in the land surface
that is at least seasonally wet, is usually heavily
vegetated, and is normally without flowing water.
Swales conduct Stormwater into primary drainage
channels, may provide some groundwater recharge,
and may be a source of mosquitoes.
Swallows: Tree Swallows (Tachycineta bicolor)
are charming little birds that are found over most of
North America and Canada. They can be voracious
mosquito eaters. They have a strong preference for
mating near water such as lakes, marshes, or wet
meadows. All of these places are also great places
for mosquito breeding. They also feed on midges,
gnats, horseflies, moths, grasshoppers, dragonflies,
and mayflies.
Swamp: low, spongy land generally saturated with
water and covered with trees and aquatic vegetation.
A deepwater swamp, such as the cypress tupelo, has
standing water all or part of the growing season.
Bottomland hardwood forest swamps are only
flooded periodically.
Temephos: an organophosphorus insecticide of
slight toxicity which is used largely as a mosquito
larvicide.
Terraces: dikes built along the contour of sloping
farm land that hold runoff and sediment to reduce
erosion.
Tidal: the periodic rise and fall of the ocean water
masses, produced by gravitational effects of the
moon and sun on the Earth.
TMDL (Total Maximum Daily Load): a
calculation of the maximum amount of a pollutant
that a waterbody can receive and still meet water
quality standards, and an allocation of that amount to
the pollutant's sources.
Topographic Position within a Watershed:
streams are assigned a stream order number (1-3)
with respect to the topographic position within the
watershed drainage system. Tributary or headwater
streams are low-order streams (1 or 2) located at
higher elevations within the watershed.
Total Suspended Solids (TSS): a measure of the
suspended solids in wastewater, effluent, or water
bodies, determined by tests for "total suspended
non-filterable solids."
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Toxic Pollutants: materials that cause death,
disease, or birth defects in organisms that ingest or
absorb them. The quantities and exposures necessary
to cause these effects can vary widely.
Upland: dry land located at an elevation above
wetlands or waterways.
Urban: relating to or concerned with a city or
densely populated area. The "urban" category
includes those areas classified as being urbanized
(having a population density of at least 1,000
persons per square mile and a total population of at
least 50,000) as well as cities, villages, boroughs
(except in Alaska and New York), towns (except
in the six New England states, New York, and
Wisconsin), and other designated census areas
having 2,500 or more persons.
Vector: an organism, often an insect or rodent that
carries a disease agent.
Vortex: a revolving mass of water which forms a
whirlpool. This whirlpool is caused by water flowing
out of a small opening in the bottom of a basin
or reservoir. A funnel shaped opening is created
downward from the water surface.
Wastewater Treatment: the process that removes
the majority of the contaminants from wastewater
or sewage and produces both a liquid effluent
suitable for disposal to the natural environment and
a sludge. To be effective, sewage must be conveyed
to a treatment plant by appropriate pipes and
infrastructure, and the process itself must be subject
to regulation and controls. Other wastewaters require
often different and sometimes specialized treatment
methods.
Water Boatmen: aquatic bugs (Order Hemiptera)
that paddle along the water surface with oarlike hind
legs. Water boatmen occur in fresh or brackish water
throughout the world. In certain ponds or lakes they
may be extremely abundant. About 525 species are
known worldwide, 132 in North America. Water
boatmen occur most commonly in ponds and along
the edges of lakes, although a few species inhabit the
brackish waters of estuaries. Most water boatmen
eat algae and minute aquatic organisms. Some are
predaceous and feed on mosquito larvae and other
small aquatic animals; in this way, they help to
control aquatic pests. In turn, they are important
prey for many larger aquatic animals.
Water Striders: a water bug (Order Hemiptera)
that looks a lot like a big mosquito walking on
the surface of the water. Water striders live on the
surface of ponds, slow streams, marshes, and other
quiet waters. Common water striders eat living
and dead insects on the surface of the water. Some
prey are aquatic insects, such as mosquito larvae
coming up from the bottom, and others are terrestrial
(land) insects, such as butterflies or beetles that
accidentally land on the surface.
Waterfowl: any bird that spends a large portion
of their lives in wetlands, in or at the edge of lakes,
rivers, or streams.
West Nile Virus (WNV): emerged in 1937 from its
origins in Africa (Uganda) into Europe, the Middle
East, west and central Asia and associated islands.
It is a flavivirus (family Flaviviridae) with more
than 70 identified viruses. Serologically, it is within
the Japanese encephalitis virus antigenic complex
similar to St. Louis, Japanese and Murray Valley
encephalitis viruses. Similar to other encephalitises,
it is cycled between birds and mosquitoes by certain
types of mosquitoes, and transmitted to mammals
(including horses) and man by other types of
infected mosquitoes known as "bridge vectors".
WNV might be described in one of four illnesses:
the least severe manifestations known as West
Nile Fever, is characterized by fever, headache,
tiredness and aches or a rash, which may last a few
days or several weeks. The other manifestations
are more severe and are grouped as "neuroinvasive
disease" which affects the nervous system; West
Nile encephalitis affects the brain, and West Nile
meningitis (meningoencephalitis) is an inflammation
of the brain and membrane around it.
Western Equine Encephalitis: an avian disease
that is spread to horses and humans by infected
mosquitoes. It is one of a group of mosquito-borne
virus diseases that can affect the central nervous
system and cause severe complications and even
death. Other similar encephalitis diseases are eastern
equine encephalitis, St. Louis encephalitis, and
LaCrosse encephalitis. Western equine encephalitis
is found in North, Central, and South America,
but most cases have been reported from the plains
regions of the western and central United States.
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Wetlands: an area that is saturated by surface or
ground water with vegetation adapted for life under
wet soil conditions, including swamps, bogs, fens,
marshes, and estuaries.
Wildlife: living organisms that are not in any way
artificial or domesticated and which exist in natural
habitats. Wildlife can refer to flora (plants) but more
commonly refers to fauna (animals). Wildlife is a
very general term for life in various ecosystems.
Deserts, rainforests, plains, and other areas—
including the most built-up urban sites—all have
distinct forms of wildlife.
Woodland: a vegetation community that includes
widely spaced large trees. The tree crowns are
typically more spreading in form than those of forest
trees and do not form a closed canopy. Grass, heath,
or scrub may develop between the trees.
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Appendix D
Sources of Information
American Mosquito Control Association : www.mosquito.org
Banks, K.E. 2003. Integrating stormwater management and vector control in a phase II city. In
Meeting the challenges of stormwater management and vector control at: www.stormh2o.com/
sw_0403_meeting.html
Delaware Department of Natural Resources and Environmental Control. Surface Water Discharges
Section Web site: www.dnrec.state.de.us/water2000/Sections/SurfWater/DWRSurfWat.htm
Gingrich, J.B., R.D. Anderson, G.M. Williams, L. O'Connor, and K. Harkins. 2006. Stormwater
ponds, constructed wetlands, and other best management practices as potential breeding sites
for West Nile virus vectors in Delaware during 2004. Journal of the American Mosquito Control
Association 22(2):289-291.
Maryland Department of the Environment. Maryland's Stormwater Management Program Web site:
www.mde.state.md.us/Programs/WaterPrograms/SedimentandStormwater/index.asp
Rey, J.R., G.F. O'Meara, S.M. O'Connell, and M.M. Cutwa-Francis. 2006. Mosquito production
from four constructed treatment wetlands in peninsular Florida. Journal of the American Mosquito
Control Association 22(2): 198-205.
The Center for Watershed Protection: www.cwp.org
The Stormwater Manager's Resource Center: www.stormwatercenter.net
USD A. The NRCS Interim Hydrogeomorphic Approach To Functional Assessment: What Should It
Entail? www.pwrc.usgs.gov/wli/waisl.htm
U.S. EPA Pesticides: Mosquito Control Web site: www.epa.gov/pesticides/health/mosquitoes
U.S. EPA. 2004. The Use of Best Management Practices (BMPs) in Urban Watersheds, EPA/600/R-
04/184. http://www.epa.gov/ORD/NRMRL/pubs/600r04184/600r04184.pdf
U.S. EPA. 2004. Stormwater Best Management Practice Design Guide . September 2004. EPA/600/
R-04/121. www.epa.gov/nrmrl/pubs/600r04121/600r04121.htm
U.S. EPA. 1999. Stormwater Technology Fact Sheet. Wet Detention Ponds. EPA 832-F-99-048.
www.epa.gov/owm/mtb/wetdtnpn.pdf
Walton, W.E. 2003. Managing mosquitoes in surface-flow constructed treatment wetlands.
Publication 8117, Division of Agriculture and Natural Resources, University of California
-Davis. 11 pp.
Zohrabian, A., M.I. Meltzer, R. Ratard, K. Billah, N.A. Molinari, K. Roy, R.D. Scott II and L.R.,
Peterson. 2004. West Nile virus economic impact, Louisiana, 2002. Emerging Infectious Diseases
10: 1736-1744. www.cdc.gov/eid
Proceedings of the Workshop on Stormwater Management and Mosquito Control 71
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