United States
Environmental Protection
Agency
Office of Water
4203
EPA 833*5-91-100
June 1991
c/EPA
CONSTRUCTION SITE STORMWATER
DISCHARGE CONTROL
AN INVENTORY OF CURRENT
PRACTICES
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Prepared for
Mr. Mike Mitchell
Work Assignment Manager
U.S. EPA
Office of Water Enforcement & Permits
Washington, D.C. 20460
By
Kamber Engineering
Civil - Environmental - Surveying
818 West Diamond Avenue
Gaithersburg, MD 20878
(301) 840-1030
DRAFT
Construction Site Stormwater
Discharge Control
An Inventory of Current Practices
EPA Contract No. 68-C8-0052
June 26, 1991
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Table of Contents
1.0 Introduction 1
2.0 Construction Site Stonnwater Discharges 2
2.1 Construction Stages 2
22 Erosion and Sediment Control 3
23 Construction Site Housekeeping 4
3.0 Stonnwater Management Theory and General Design Basis 6
4.0 Stonnwater Management Planning Considerations g
5.0 Stormwater Management Practice Inventory 11
5.1 Non-Structural Storm Water Management 11
5.2 Structural Storm Water Management Facilities 11
Appendix 13
Non-Structural Storm Water Management Practices
Structural Storm Water Management Practices
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1.0 Introduction
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1.0 Introduction
The information presented in this report has been prepared to assist municipalities in preparing
the Stormwater Management and Sediment and Erosion Control program portions of their system-
wide National Pollutant Discharge Elimination Service (NPDES) Stormwater permit applications.
This report discusses the Stormwater discharges of construction sites and provides an inventory of
Stormwater management technologies currently implemented to control both the quantity and
quality of post-construction storm water discharges. The inventory is intended to be
comprehensive; providing general information including technology description, application,
advantages, and disadvantages for structural and non structural methods of storm water
management. The inventory also addresses methods considered "Best Management Practices", i.e.,
storm water management practices which provide pollutant removal benefits, and methods
considered primarily quantity control measures. In addition to the inventory, this report discusses
a variety of planning considerations which influence the selection and design of storm water
management facilities on an individual site or within a particular drainage area or watershed.
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2.0 Construction Site Stormwater Discharges
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2.0 Construction Site Stormwater Discharges
The quantity and quality of storm water discharged from a construction site varies according to the
stage of construction and the effectiveness of measures implemented on-site to control the quality
of storm water discharges. These controls include structural measures such as erosion and sediment
control practices which control the discharge of sediment related pollutants, and non-structural
measures such as site management or housekeeping plans which control non-sediment related
pollutants on the construction site.
2.1 Construction Stages
Typical construction stages and the changes in site erosion potential and storm water runoff that
accompany each stage are described below:
Stage 1 Pre-Construction
Storm water runoff from the site is at predeveloped levels, erosion is minimal. Site perimeter
erosion controls should be installed for initial disturbed areas.
Stage 2 Clearing and Grading for Access
Clearing and grading is accomplished for access only. Measures are implemented to protect off-
site properties, including installation of inlet protection measures in the downstream storm drain
system, and the installation of construction entrances (large aggregate aprons which transition from
the construction site to paved off:site roadways). Erosion from the site increases to moderate
levels, and storm water runoff volume begins to increase as vegetation is removed and site areas
become compacted by heavy equipment. At this stage, the installation of sediment controls and
storm water management facilities should occur.
Stage 3 Full Clearing and Grading
Full clearing and grading results in moderate to high levels of erosion. Major storms can wash
away sediment control structures, and can deposit substantial sediment in control structures,
significantly reducing capacity. Runoff volume is increasing as disturbed area increases. Regular
inspection and maintenance of sediment control practices is essential to maintain effectiveness of
ihe devices.
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Stage 4 Installation of Storm Drainage System
Storm water management facility construction is complete and storm drains are installed and
gradually connected to concentrate and divert runoff to the structure or structures. Erosion
continues to be moderate to high, and storm water runoff volume continues to increase as
disturbed areas become more compacted.
Stage 5 Active Construction of Structures
Construction is at its peak. Moderate to high erosion rates continue, and storm water runoff
volumes approach maximum. The impact of high erosion rates can be significant if sediment
control practices have not been maintained during previous stages of construction and are clogged
or have inadequate capacity to control site storm water discharges.
Stage 6 Site Stabilization
Disturbed areas are stabilized with vegetation or other suitable, non-erosive cover, and erosion
rates decline. Once all areas of the site are stabilized, temporary sediment control measures are
removed from the site, and sediment collected during the construction phase is removed (dredged)
from permanent storm water control structures to restore design capacity, if necessary. Storm
water runoff volume reaches post-development rates and may be less than the volume that
occurred in stage 5, due to areas of the site that are stabilized with vegetation.
2.2 Erosion and Sediment Control
The overall plan of erosion and sediment control for a construction site includes implementation
and regular maintenance of sediment control practices. These practices include various erosion and
sediment control measures that can be categorized as follows;
1. Perimeter controls
2. Slope protection
3. Sediment traps and basins
4. Drainaeeway and stream protection
5. Temporary1 stabilization
6. Permanent stabilization.
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These measures are described in an inventory prepared under Task 2 of this work assignment
entitled "Sediment and Erosion Control Measures, An Inventory of Current Practice". Perimeter
controls, slope protection, and sediment traps are temporary forms of stabilization that are
generally removed from the construction site at the end of the construction period. These facilities
are usually replaced with permanent stabilization measures such as vegetation or other permanent
(non eroding) surfaces. The sediment and erosion control measure most often converted to a
permanent structure for storm water management is the sediment basin. The sediment basin can
often be dredged to remove sediment accumulated during the project construction phase, and with
minor improvements including the installation of an appropriate outlet structure, can be converted
to provide long-term storm water management for the
site.
13 Construction Site Housekeeping
Non-structural storm water controls on construction sites focus on methods of preventing non-
sediment related pollutants from entering storm water runoff, sediment control structures, the down
stream storm drain system, and receiving streams. Pollutants that may be generated on a
construction site, and could potentially enter storm water runoff from the site if not controlled,
include gasoline, oils, grease, paints, raw materials used in the manufacture of concrete including
sand, aggregate, cement, water and admixtures, solvents, paper, plastic, styrofoam, aluminum cans,
glass bottles, and other forms of liquid and solid wastes. Construction site management plans
should include the following elements to prevent these .pollutants from entering site storm water
discharges:
Designated areas for equipment maintenance and repair which
include appropriate waste recepticals for spent oils, gasoline, grease
and solvents, and regular collection and disposal schedules.
• A site solid waste plan which provides waste receptacles of adequate
capacity at convenient locations to site workers and provides regular
collection of accumulated wastes.
Equipment washdown areas located on-site only in areas which drain
to regularly maintained sediment control devices designed to
accommodate such discharges.
Storage areas protected from storm water in accordance with the
manufacturers guidelines for storage of chemicals, paints, solvents
acids, pesticides, fertilizers or other potentially toxic water pollutants.
Storage areas for raw materials used in construction which can be
carried by storm water runoff located only in drainage areas
controlled by retention-type sediment control devices.
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Water used during dust control activities discharged only to on-site
retention-type sediment control devices.
Adequately maintained sanitary facilities.
Routine site housekeeping in accordance with a construction site management plan can
non sediment related pollutants from entering storm water runoff. Sediment which enters storm
water during rainfall events, washdown of construction equipment, or from dust control activities
can be controlled by property maintained sediment control devices. The remaining sections of this
report focus on the purpose and general design basis of storm water management facilities which
control storm water discharges after construction is completed and includes the technology
inventory of current storm water management practice.
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3.0 Stormwater Management Theory
And General Design Basis
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3.0 Stormwater Management Theory And General
Design Basis
Water flowing over the land during and immediately following a rainstorm is called stormwatcr
runoff. The characteristics of stormwater runoff in an urbanizing watershed change substantially
in terms of quantity, quality, and timing of the discharge to the natural hydrologic system, during
and after construction activities. Prior to construction, stormwater runoff is managed by a natural
hydrologic system created by the vegetation, soils, geology and topography of the watershed.
Rainfall enters the hydrogic system via a number of routes:
• a portion falls on leaf or plant where it eventually evaporates;
* a portion is absorbed into the ground near the surface, to ultimately be
absorbed through the root systems of vegetation and returned to the
atmosphere through transpiration;
• a portion percolates through surface soils to replenish groundwater;
a portion collects into rivulets which flow down gradient to natural
depressions and ultimately to receiving waters; i.e., tributaries, streams, rivers,
lakes, and the sea. This portion is termed storm water runoff.
The quantity of storm water that will be converted to runoff on a given site is a function of the
storm event (the quantity of rainfall delivered to the system), vegetative cover, soil type, and
topography. Construction activities remove vegetation and create impervious surfaces such as
streets, parking areas, sidewalks and roofs, and the change in land use created by the construction
results in changes in the natural hydrologic system. These changes reduce the amount of rainfall
that evaporates from plant surfaces, is absorbed and transpired by vegetation, or infiltrates through
the soil column to replenish groundwater supplies, and increase the amount of rainfall convened
to direct surface runoff. Post-construction runoff is often concentrated in peaks that are sharper,
faster and higher than those produced by the undeveloped site. The concentrated, faster moving
runoff dislodges and dissolves pollutants which build up on the impervious land surfaces between
storm events and thus create changes the quality of storm water runoff discharged to surface
waters.
The cumulative effects of these changes can be observed in receiving streams where the increased
peak discharges create unstable and unvegetated stream banks, scoured or heavily deposited stream
channels, accumulations of in-stream trash and debris, reduced base-flow (non-storm flow), and the
regular disruption or absence of aquatic communities. Storm water management facilities are
intended to reduce the impact of the long term changes in the site storm water runoff
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characteristics by controlling the quantity, and in some facilities, the quality of post-construction
storm water discharges.
In order to address the impacts of the increased peak storm water discharges in receiving streams,
storm water management facilities are designed to retain the peak storm water runoff from the
developed site within the structure and control the release rate to a level equal to or less than
the peak runoff rate that would have been generated by the site under the predevelopment
conditions. The volume of storage provided within the facility is controlled by the design storm
(the amount of rainfall) assumed for calculation of the pre-development and post-development
site runoff, and the criteria which specify the allowable release rate. Many localities specify the
10-year design storm as the design basis for storm water management structures to protect
downstream drainage structures such as road crossing culverts originally designed to pass a 10-
year pre-development storm. In the metropolitan Washington area, most jurisdictions require
control of the 2 and 10 year return interval storms to predevelopment release rates. In areas
where downstream flooding is an existing problem, control may be required for the 25, 50 and 100
year storms to reduce downstream effects of these major storms. In general, the larger the storm
event controlled within the structure and the slower the allowable release rate, the greater the
storage volume and cost of the facility.
Water quality controls address the impacts of increasing the amount and type of pollutants
discharged to receiving streams via storm water. The National Urban Runoff Project (NURP)
studies found that the majority of pollutants discharged to receiving streams via storm water are
washed from impervious land surfaces during the early stages of a storm, and are contained within
the first 1/2 to 1 inch of runoff from the contributing drainage area. To reduce the impact of
these "first flush" discharges on receiving streams, storm water management facility designs can be
modified to improve discharge quality by providing treatment within the structure. Additionally,
a number of structural and nonstructural facilities and management practices have been developed
to remove or reduce pollutants in storm water runoff and in discharges from storm water
management facilities. These methods are termed "Best Management Practices", or BMPs. The
facilities and methods referred to as BMPs may provide only water quality control, or both quantity
and quality control within the same facility.
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4.0 Stormwater Management Planning
Considerations
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4.0 Stormwater Management Planning Considerations.
Stormwater management facilities control the volume, quality and release rate of storm water
runoff from the developed site once construction is complete and the site is stabilized The
development of a storm water management plan for a site includes the selection of the most
appropriate type of facility, method or combination of methods to provide quantity and water
quality control and is influenced by the physical site conditions, the size of the contributing
drainage area, and the water quality and classification of the receiving stream.
Site conditions include topography, soils, slopes, geology, and the location of on-site surface waters
including intermittent and flowing streams and drainageways, ponds, lakes and wetlands. In
addition to the natural features, the site conditions includes the existing zoning designation and
the land use proposed by the owner/developer.
The size of the site and the contributing drainage area influence the selection of control structures.
In general, the use of inGltration-typc storm water management structures is limited to smaller
drainage areas (generally less than ten acres), while the use of pond type facilities, particularly
wetponds, is limited to larger drainage areas (generally greater than 10 acres) where sufficient base
flow to support the permanent pool is available. In addition to size of the site and contributing
drainage area, soils and topography influence selection of control methods. For example,
infiltration-type structures arc limited to sites with sandy, or sandy loam soils which are capable of
infiltrating the required volumes, and grassed swale type conveyance systems are only appropriate
on sites with gentle slopes so that erosive velocities do not scour the bottom of the swale. These
types of constraints are addressed in the inventory provided in the appendix.
Site planning techniques are used to develop a concept plan for a proposed construction activity
which accomplishes the long-term land-use change objectives of the development within the
framework of existing site conditions. Site planning which minimizes disturbed area, reduces the
need for mass grading of the site, and preserves, to the maximum extent practicable, the natural
site topography and drainage features, can reduce the number of sediment control structures and
practices necessary to protect receiving waters during construction, and can reduce the volume of
storage necessary in storm water management structures. Site planning which clusters development
in areas most suited to construction allows preservation of more sensitive areas such as on-site
streams and wetlands, and areas of unstable soils and steep slopes. Cluster development techniques
also increase the opportunity to provide undisturbed buffer areas adjacent to on-site streams which
can provide water quality benefits.
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The concept site plan indicates the proposed location of structures including buildings, roadways
and parking facilities. Using this information, and a rough grading plan of the site, storm water
management options can be developed.
The plan for managing site storm water will include methods of storm water collection, conveyance
and management in control structures, and may include additional control measures which provide
water quality improvement as well as quantity control The selection of the appropriate facility
for a given site is influenced by size of the receiving drainage area and other site specific
considerations. For example, a proposed large-lot single-family residential development storm water
management concept plan may include storm water collection and conveyance by a combination
of grassed swales and enclosed pipes which discharge to a central storm water management wet
pond. Quantity control would be provided by the storm water management wetpond, which
controls the discharge of the two and ten year return interval storms from the developed site to
predevelopment levels. Quality control would be provided by the grassed swales ( with check dams
) which provide some physical filtering of storm water runoff and encourage infiltration, and by the
design of the pond which provides at least 24 hours of detention for the mean storm event A
commercial site in the same watershed might implement a completely different set of management
practices.
The inventory of storm water management practice provided in the Appendix addresses site
conditions most appropriate for each of the practices, and other application considerations.
In addition to selection of storm water management practices appropriate to site conditions, the
overall plan for storm water management must consider the water quality and existing storm water
management practices of the entire watershed. Watershed conditions can affect the selection of
the method of storm water management quantity control and the level and type of water quality
protection provided by the facility. The storm water management plan for the residential
subdivision described above would be designed as a dry pond, not a wetpond, if it were discharging
to a watershed protected for trout propagation to minimize the potential for thermal impacts.
Development within the protected watershed would likely have to conform to standards which limit
impervious area and establish stream setbacks for water quality and aquatic habitat protection.
Similarly, if the storm water management facility discharged to receiving waters protected for water
supply, the facility might include extended detention features and a planted wetlands permanent
pool to provide maximum removal of pollutants in storm water discharges. If the proposed
development were located in the lower reaches of a drainage basin where quantity controls are
least effective, the proposed storm water management plan might focus on quality controls, and
provide minimal quantity control within the structures. Similarly, if the site is located immediately
upstream of a proposed major regional storm water management facility, a waiver of on-site storm
water management" quantity and quality control might be appropriate in the event that acceptable
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conveyance of site storm water runoff can be provided to the regional facility.
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5.0 Stormwater Management Practice Inventory
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5.0 Stormwater Management Practice Inventory
As noted in previous sections of this report, storm water management facilities are installed during
the construction phase to control the quantity and/or quality of storm water discharged from the
site once construction is completed. The storm water management inventory provided in the
appendix is addresses structural and non structural methods of storm water management, and
identifies which methods are considered "Best Management Practices", or storm water management
methods which provide water quality control
5.1 Non-structural Storm Water Management
Non-structural storm water management methods include vegetation practices designed to limit site
impervious area and reduce the need for volume control storm water management facilities, and
pollution prevention techniques designed to control pollutants prior to contact with storm water
and discharge in storm water runoff.
Vegetation practices include grassed swales and grassed and wooded filter strips, and various
landscaping techniques which encourage the preservation of existing woodlands, and the replanting
of woodlands where preservation is not possible. These practices are often used in combination
with other quantity control based storm water management practices to improve the quality of
storm water discharged from the site. In addition to swales, filter strips, and landscaping techniques
used individually as water quality control methods, vegetation plantings are often proposed within
the basins of volume control storm water management facilities such as dry ponds and wetponds
to improve the pollutant removal capabilities of these facilities.
Non-structural storm water management practices include housekeeping practices such as street
sweeping, urban litter control programs, and fertilizer and pesticide control programs. These storm
water management methods focus on controlling the build-up of pollutants on the land surface
in between storm events to prevent pollutants from entering storm water runoff.
S3. Structural Storm Water Management Facilities
Structural storm water management facilities described in the inventory provided in the appendix
are grouped in three categories; pond systems, infiltration-based systems, and underground and
other storage systems.
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Pond systems designed primarily as volume control structures provide minimal pollutant removal
capabilities and cannot be considered water quality controls, or BMP facilities. However, pond
systems can be designed with extended detention, sediment forebays, planted wetlands basins and
permanent pools, which improve water quality performance significantly by creating conditions
within the basin for physical and biological treatment of pollutants in storm water runoff.
Infiltration -based storm water management facilities include infiltration basins and trenches,
pavement alternatives including porous asphalt and grid pavers, and rooftop storage-disposal
alternatives which direct rooftop runoff to underground facilities which discharge to the surrounding
soils. Infiltration devices are all considered BMPs because they treat storm water by filtration
through gravel and the soil column, and discharge treated storm water to ground water. In
addition to the treatment provided by percolation through the soil column, infiltration devices are
particularly favored because storm water replenishes groundwater and thus replicates as much as
possible the predevelopment hydrology of the site. Pavement alternatives reduce site impervious
area, and thus reduce the need for volume control storm water management facilities. Rooftop
storage-disposal facilities are similar to infiltration trenches and basins in that ultimate disposal of
storm water is to on-site soils and ultimately to local groundwater.
Underground storage facilities include vaults and pipe storage systems that are typically installed
on urban and suburban commercial/industrial sites where site area is limited. These systems are
typically designed as volume control facilities only, and provide only temporary detention for time
periods insufficient to provide for significant sedimentation or removal of other storm water
pollutants. For this reason, underground vaults and pipe storage facilities are not considered BMP
facilities. Similarly, parking lot storage, and rooftop storage facilities provide temporary storage of
storm water and a controlled release rate to receiving streams, but provide only minimal pollutant
removal benefits. These facilities are also not considered BMP facilities.
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APPENDIX
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NON STRUCTURAL
STORMWATER MANAGEMENT PRACTICES
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Street Sweeping
Definition:
Regular sweeping of urban areas to remove accumulated debris including sediment, trash, materials
From atmospheric deposition and motor vehicle sources.
Purpose:
To remove accumulated materials between storms to prevent the dislodge and transport of these
pollutants to surface waters during storm events.
Conditions Where Practice Applies:
Urban areas and particular industrial sites where accumulation of materials on paved surfaces is
significant
Effectiveness:
The practice has received limited application in urban areas that has been monitored to provide
data sufficient to estimate effectiveness.
Advantages:
Can be implemented in urban areas to improve storm water runoff quality without committing
costly land area necessary for volume controls. Can be implemented as a retrofit storm water
management BMP.
Disadvantages:
Method is labor and equipment intensive. In addition to purchase/rental of the street sweeping
equipment, operators are necessary, and schedules must be developed which do not conflict with
periods of high use/ activity by pedestrian and motor vehicle traffic. Equipment is noisy, and may
generate complaints from residential portions of the urban area.
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Fertilizer and Pesticide Application Controls
Definition
Managing the application of fertilizers and pesticides to encourage proper application.
Purpose
To reduce pesticides and fertilizers in storm water runoff from residential, commercial and
industrial land uses.
Condition Where Practice Applies
Suburban and urban areas including residential lots, common areas, recreation areas, parks, roadway
right of ways, commercial sites, industrial sites, cemeteries, and other institutions and public
facilities.
Effectiveness
Unknown
Advantages
A storm water management BMP that can be applied on a system-wide or jurisdiction basis to
reduce nutrient loadings and pesticides in receiving waters from the entire system.
Disadvantages
Implementation of a public information program to encourage proper application of pesticides and
fertilizers would be costly, and estimates of effectiveness would be conjecture at best.
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Vegetative Practices
Description
Grass filter strips, wooded filter strips, preservation of wooded areas, reforestation areas and tree-
shrub landscaping instead of "turfscaping".
Purpose
To provide vegetated areas between structural development and receiving streams to provide a
filtering area for storm water and to promote infiltration into the soil
Conditions Where Practice Applies
Mostly applies to developing areas, but in some instances can also be used as a water quality BMP
in retrofit situations.
Effectiveness
Treatment of storm water in filter strip applications is accomplished physically by a combination
of filtration through the standing vegetation and infiltration into the underlying soils. In order to
treat storm water effectively, filter strips must be designed to function as overland flow systems
where storm water is evenly distributed. There is a high potential for short circuiting and reduced
pollutant removal from these systems.
Advantages
In addition to water quality benefits provided by vegetative filler and infiltration, vegetative
practices, particularly those involving preservation of woodlands, reforestation, or tree-shrub
landscaping provide aethetic features for the community, and provide wildlife habitat in urban and
suburban areas.
Disadvantages
Filter strips are considered BMPs, but provide limited storm water volume control and are usually
implemented in combination with other volume control storm water management facilities.
Sufficient land area must be available for grassed and woodland filter strips and woodland
preservation areas and reforestation areas. Land availability constrains application of this BMP in
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rctroGt situations.
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Schematic of a Filtar Strip
Bonus Ptocod PirponAcMtar
to lop of Strip Prcvont
Concomraiod Flows
Acts as
Lr**l Spr«sd«r
5% Strip Slop* or L»s»
Reference:
Metropolitan Washington Council of Governments. Controlling Urban Runoff- A Practical Manual
tor Planning and Designing Urban BMPV Thomas R. Schueler, July, 1987. ~
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Grassed Swales
Description
Grassed lined channels used to collect and convey storm water runofL
Purpose
An alternative to closed pipe systems which provides opportunities to reduce storm water velocity
and promote infiltration.
Conditions Where Practice Applies
Low density development and in medians and adjoining roadways. Soil and slope conditions dictate
application.
Effectiveness
Treatment of pollutants is primarily physical filtration through standing vegetation, with some
infiltration into underlying soils. By slowing velocity of runoff and providing some infiltration,
grassed swales reduce the time of concentration (the time it takes runoff to reach the receiving
stream).
Advantages
Provides a low cost alternative to enclosed pipe systems which offers some water quality benefits
if properly designed.
Disadvantages
Although grassed swales provide some flow attenuation, they are not considered volume control
storm water management facilities. Pollutant removal effectiveness is a function of proper design
and application, and can be variable.
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Schematic of a Grassad Swal«
SwatoStopc*
•» QOM to
Zero at Drainage
RariraadTi*
Ch#efc-dam
(lncrMS*> tnMMtwn)
Dans* Growth :^$?5S&3
ot Grass ( R«*d --V^-M-l
CanaryoU™ ''^feS
TailfMctMl TSft-»-ss?i
Slon* Pr*v«nt«
Downstream Scouf
Reference:
Metropolitan Washington Council of Governments, Controlling Urban Runoff: A Practical Manual
for Planning and Designing Urban BMP's. Thomas R. Schueier, July, 1987.
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Structural Stormwater Management Practices
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Stormwater Detention Wetpond
Description
Wetponds are natural or man made depressions which provide storage of the permanent pool and
storm water runoff from a site or drainage area, and allows gradual release of the post-
development peak runoff from the site to down stream areas.
Purpose
Wetponds regulate the discharge of post-development site runoff, and provide water quality control
by providing physical settling of storm water pollutants and by providing an aquatic system for
biological treatment
Conditions Where Practice Applies
Wetponds are appropriate where the contributing drainage area provides sufficient base flow to
support the permanent pool area of the wetpond. Generally, the minimum contributing drainage
area for wetponds is about 10 acres unless a known water source such as a spring is present.
Larger ponds are preferred.
Advantages
Wetponds provide both volume and water quality control, and provide additional advantages by
offering opportunities for recreation and wildlife habitat in the community. Water quality
performance of wetponds is variable, but generally high. Extended detention and other design
features such as sediment forebays and permanent pool areas managed as shallow wetland marshes
improve water quality performance.
Disadvantages
Permanent pool areas can dry up during periods of drought in marginal watersheds, creating odors
and nuisance. Wetponds are typically placed in stream valleys which meet the regulatory definition
of wetlands and require U.S. Corps of Engineers and State water quality certification approvals
for construction. Pond construction in the stream valley alters riparian wetland habitat and
precludes the migration of aquatic species through the pond. Wetponds can present safety hazards
in residential communities. Fencing can control access but affects aesthetics of the pond.
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WET DETENTION SYSTEM
POND CONFIGUFW ION - A
BAFFLE OR
SEDIMENT SUMP
TMENT
UMl; 5T
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Methods For Extending Detention Times In Wet Ponds
ncr Pond Orampia* vrtti V>ta*
Concrvi* Boi A««r
Front Vi«iM
Side Vt*w
Reference:
Metropolitan Wsshington Council of Governments, Controlling Urban Runoff: A Practical
for Planning and Designing Urban BMP's. Thomas R. Schueier. July, 1987.
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WET DETENTION SYSTEM
POND CONFIGURATION - B
TREATMENT
VOLUME
10:1 SLOPE (DESIRABLE)
(4:1 MINIMUM)
SEDIMENT SUMP
DEEPER AREA
Source: Southwest Florida Hater Management District
Management and Storage of Surface Waters, Permit Information
Manual, Vol.1, March 1988.
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Stormwater Detention Dry Pond
Definition
Dry ponds are man made storage facilities which remain dry between storm events, and provide
temporary storage and gradual release of the post development runoff during and after storm
events.
Purpose
Dry ponds contain post-development storm water runoff and control the release to predevelopmcnt
peak levels. Unless modified to provide extended detention, dry ponds provide only minimal water
quality improvement, and are considered primarily a volume control facility.
Advantages
Dry ponds can be implemented in watersheds and drainage areas where thermal impacts are a
concern. Dry ponds are generally the least costly storm water management volume control
alternative. Additionally, recreation areas such as playing fields can be used as dry detention areas.
Disadvantages
Dry ponds provide little water quality control unless designed for extended detention.
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Porous Asphalt Pavement
Definition
Pavement alternative which allows infiltration of storm water to gravel and soil layers underlying
the pavement surface.
Purpose
To reduce the quantity of storm water runoff from paved areas and infiltrate storm water to
underlying soils. Practice is applicable only in areas with suitable subsurface soil conditions.
Advantages
Reduces the need for volume control storm water management facilities, and provides water quality
control for storm water which infiltrates through the pavement to underlying soils.
Disadvantages
Voids in asphalt fill with sediment over time and surface eventually clogs. Must be combined with
other volume control storm water management facilities. Water remaining in void areas is subject
to freeze-thaw cycle which stresses and weakens pavement
KE# 91521.00 - 26 - KAMBER ENGINEERING
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Methods For Extending Detention Times in Dry Ponds
Sid* View
D mKt CenlfoMd >«rKrx«c
E«nnd«d 0«Mn»or» Onhcoi
Tritn Reck
C»c
Sionc
Grivti
m w*«n
internal Onlm
To Low FK
*
':•-.''. ';'.'...
.
v .*'.*..'-•.'„• ? . - • • • ; • "."''•,•
o c- o z - :• :• 3 c D o c o
r
. •-.
\
1
>
— Gravel
Wrtoptd with Finer fabric
Reference:
Metropolitan Washington Council of Government!, Controlling Urban Runoff: A Practical Manual
For Planning and Designing Urban BMP's. Thomas R. Schueler. July, 1987.
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PERVIOUS CONCRETE PAVEMENT
TYPICAL SECTION
X
•--.I
COA/ORETE CURB
CALCULATED WATER STORAGE
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POROUS ASPHALT SURFACE COURSE
1/2" to 3/4" Aggregate
asphaltic mix
2.5 to 4" thickness typical
FITTER COURSE
1/2" Aggretate
2" Thickness
RESERVOIR BASE COURSE
1" to 2" Aggregate
Voids volume is designed for
runoff Retention
Thickness is based on storage
required
FITTER FAURIC
EXISTING SOIL
Minimal compaction to retain
porosity and permeability
POROUS ASPHALT PAVING TYPICAL SECTION
Modified after Dinlj, 1980 and City of Rockvllle, Maryland, 198?
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Infiltration Trenches and Basins
Description
Infiltration facilities collect, store and infiltrate runoff through gravel areas and underlying soils.
Purpose
To provide both volume control and water quality control, and replicate as much as possible,
predevelopment hydrologic conditions.
Conditions Where Practice Applies
Infiltration devices are most applicable on smaller development sites, and installation requires
careful management during the construction period to avoid clogging the structure with sediment
Advantages
Changes in down stream peak flows are minimal because storm water is infiltrated lo resupply local
groundwater. Water quality control is provided by infiltration through the soil column and is
considered high performance.
Disadvantages
Infiltration structures are costly to construct and require maintenance that eventually will involve
reconstruction of the basin to restore infiltration capacity as systems become clogged over time.
Infiltration systems can only be implemented on sites with suitable soil and ground water
conditions.
KE# 91521.00 . 27 - KAMBER ENGINEERING
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Example Application of a Vegetated Area for
Pretreatment of Runoff Prior to Exflltration in Frederick Co. HD
Dike
20' Minimum Vegetated Strip
Vegetated Area
(for Filtering)
Filter fabric
Filter Fabric
Width
Reference:
Florida Department of Environmental Regulation. The Florida Development Manual: A Guide To
Sound Land And Water Management. June, 1988.
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TYPICAL INFILTRATION TRENCH UNDER GUTTERLESS ROOF
Source: Virginia Soil and Water Conservation Commission
-------
Cross-Section of Typical InfiItration/ExfiItration
Trench System for Parking Areas or Roadways
" r^
ovim iow—-t\
Sldllt.UVAII U
iniiini I
SIORMNAIH
nun — OHIFIIW
\
now
SDMI 101
PARKING LOT
RUNOFF
> or
Wf-
10
iitr Aii.irm
ti i
nisi
MOS! fOUBIMIS
UYEM.nitJOLE. MILLS
ANDpnEcounr.iNc.
{IIGIIIfFUS S'MIVfrOFlS
SKIION * - I
IIFIITIMIIIN
nitii
Ctlll
Ctirte
Reference:
Flonda Department of Environmental Regulation. The Florid* D^lopn.ent M.m,.|. A
Sound Land And Water ManagemenL June, 1988.
-------
Examples of Typical Underground Percolation Systems
for
Retrofitting Existing Storrasewer Systems 1n Orlando, Florida
ntemc
HOCK
FOOT*II
M» fli. 56 Cr»
WASHINOTON STMCCT
4I~X •' GRATC
CIMft
PIEVIIlS NQ 9 DOT
DOW FOOT *57
Reference:
Florida Department of Environmental Regulation. The Florida Development Manual: A Qyjde To
Sound Land And Water Manaeemem. June. 1988.
-------
TYPICAL SECIION. SLAB COVERED TRENCH, OAOE COUNTY, FLORIDA
JC
"o
*«
NOTES:
E2P
SFD.
« Cl.
Mrf
M.
0
J
/
Yf*
^
\*£
>
r
t=5=3
1
/eieu
|i>.V.» .'^
'I
U a- 2" J. lime! IINCII
r
^x~ CMIIj
*--«=-»
i
.-._
-H
•-,
*i'j
>^
///AL
^L^^A»'
^^^^^^_
f »ni
^
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r S*
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-OPENING
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1
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i
fMIIIS)
M(|H(N| — . i
SUI |OI
CONC.SUIt,
*± . t • • 'A T*y; j y «?
*•.*••>»•*«•« i (• 4:
'
10 TRINCJL
!T_JiUI IAfli_
^
Nlv^
j^
i
jy»ii' iiijjLiUMUiU'JMfl
//////** A^Jr^£Affr7777//(
Scllh* ^ g^^"^
*•:*!/•• »/••• J' *''fc"ii
-*• if: « *• • J -Ji — 2VM f-
« » ,!• i ».-^ 71 » ».*'«| . i
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= IHl" ^Slli ^
; '•. c c o
i :'. - 1
fe
wi&fwitfmMifffiWX w*ww* * v0u^ *~
WW >~CONSTIHCT SUMP (Mil
ONIY If CftfCN 1 SIN
LONGITUDINAL SECTION
1) If material at edge of ditch is unsuitable 2) Transition to trench bottom when it
for foundation underslab, clean out and backfill is lower than catch basin bottom
with concrete. Depth of backfill varies.
Reference:
Florida Department of Environmental Regulation. The Florida Development Manual: A Guide To
Sound Land And Water Management. June. 1988.
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FRENCH DRAIN (EXFILTRATION TRENCH). DADE COUNTY. FLORIDA
MMOVI ior Mir or sncoi 101
toociiif 01 viiiiriiiuii rifi
-for Perl. (HP.,Open loint I1/,".
Overlap with Raofinj Slate
SEIECT -:/.
FILL v;
301 loofiie mi
tlllll Cllll
ill NlirCI
wmi Tint
LOHGITUOINAL SECTION
TRANSVERSE SECTION
NOTES;
TJTf W cone bell ft spigot pipe 5' long is not available.
pipe, tp to 24" in diareter may be substituted.
2) If cone bell ft spigot pipe is not used or if the length
of pipe used is greater than 5'. 3/4" saw cuts shall be
made at intervals of 2* thru the upper half of pipe. 5'
lengths may be used for vitrified clay pipe.
3) The contractor has the option of Installing
the following pipe types:
A. Concrete - perforated or non-perforated (bell spigot)
B. Vitrified Clay -
* C. Corrugated Metal - Bituninous coated (perforated)
* 0. Corrugated Alunlntm (perforated)
4) No pipe perforations for 10' +.
* 1/4' to 3/8" dia. hole, spaced at 2-3/4" *_ (mininun 162 holes per lln.ft.)
Reference:
Florida Department of Environmental Regulation. The Florida Development Manual: A Guide To
Sound Land And Water Management. June. 1988.
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ffifflk
Poured-In-Ptace Slab
Lattice Unit
TYPES OF GRID AND MODULAR PAVEMENTS
Source: Virginia Soil and Water Conservation ConrMsslon"
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Rooftop Runoff Disposal
Description
Disposal of rooftop runoff by systems and techniques which avoid or replace direct connections to
storm or sanitary sewers. Disposal alternatives include underground vaults, cisterns, infiltration
trenches and basins.
Purpose
To detain roof top runoff and provide opportunities for reuse and eventual infiltration to
underlying soils.
Conditions Where Practice Applies
In urban and suburban areas where space constrains use of other volume control storm water
management alternatives. Only applicable on sites where adequate storage can be provided, or
soil and ground water conditions are suitable for the infiltration of runoff.
Advantages
When used on an area wide basts, can provide effective volume and quality control for rooftop
runoff. Particularly applicable in areas where thermal impacts are a concern.
Disadvantages
Similar to other infiltration-type devices in terms of maintenance/ reconstruction requirements for
infiltration portion of the system. Roof top detention may require building structural improvement
to accommodate weight of storm water detained temporarily on roof.
KE# 91521.00 - 28 - KAMBER ENGINEERING
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INFILTRATION DRAINAGE OF ROOFTOP
.'/
P'Pe — N
)
^ <
•
AVAILABL
FLAT
PLAKf
WfcTEC.
P/PE
PLANT
WITU<^UT
"~ *="'=
Source: Virginia Soil and Water Conservation Conwission
-------
—Cleanouts
Use water for
lawn watering or
other purposes
TYPICAL RETENTION CISTERN
Source: Virginia Soil and Water Conservation Conmission
-------
Underground and Other Storage Systems
KE# 91521.00 - 29 - KAMBER ENGINEERING
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Water Quality Inlet
Description
A water quality inlet is basically a three chambered oil/grit separator provided at curb inlets in the
storm drain system which receives runoff from parking areas and access drives.
Purpose
Water quality inlets are intended to provide removal of oil and grease and gross solids from storm
water runoff entering the storm drain system. Water quality inlets provide minimal storage and are
not considered volume control facilities.
Conditions Where Practice Applies
In urban and suburban area parking lots and streets in commercial and industrial land use areas.
Advantages
If properly maintained, water quality inlets can provide removal of solids including grit (heavy
portion of sediment load which readily settles out of the water column), and floatable trash, debris,
oil and grease. Chambers of the oil grit separator must be regularly cleaned to remove
accumulated sediment and debris to avoid wash through of these materials or clogging of the
facility during subsequent storm events.
Disadvantages
Water quality inlet provides removal of gross solids in storm water runoff only. These facilities do
not provide adequate storage to allow significant settling of solids or removal of other pollutants.
Adequate maintenance is necessary to maintain effectiveness of gross solids removal process.
Water quality inlets are an improvement over traditional storm drain inlets because they provide
for screening of gross debris and prevent debris from entering the downstream storm drain system
and receiving waters. However, water quality inlets are more costly to install and maintain and do
not provide significant pollutant removal or volume control benefits.
KE# 91521.00 - 3d - KAMBER ENGINEERING
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Side Vt«w
Acceia
Stormdram
Intel
400 Cub»e Feel
of Storage P«f
ContntoMtmg
Acre. 4 Feet
Remtorccd
Concrete
Construction
Firti Cnamoer
(Sediment Trapemq)
Second Chamber
(Oil Separation)
Third Chamber
Schematic of a Water Quality Inlet, Rockville Percolating
Inlet Design
Top View
Side View
Curb inlet to
Ptrit ChamDer
Tr»»h i p* I 6 Inert
Rack ' i-J Orifices
Outlet to
Stormorain System
Curb
Road
inlet
Manholes
Road Surface
Slormaram
Oullel
-jrvJ Gravel Layer
Source: City of RocKville
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Underground Storage
Definition:
Underground storage is the practice of storing storm water runoff in underground vaults, oversized
pipes, and other structures beneath site structures such as parking lots.
Purpose:
The purpose of underground storage is to provide volume control on space limited sites.
Conditions Where Practice Applies:
Underground storage is applicable where there is a lack of surface storage area or the land cost
is greater than that of underground storage construction.
Effectiveness:
Underground storage is effective for volume control only. Water quality control is not provided
by these facilities.
Advantages:
The advantage of underground storage is that it can be used on space limited sites and facility
location is not greatly influenced by site topography.
Disadvantages:
Cost is the major disadvantage. Underground facilities are expensive to construct and are not
easily maintained. Accordingly, underground structures are applicable only in areas where land
costs are high and space is limited.
KE* 91521.00 - 29 - KAMBER ENGINEERING
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Rooftop Detention
Definition:
Rooftop detention facilities provide temporary stormwatcr storage on flat roof surfaces allowing
gradual release of runoff to ground-level storm drain systems.
Purpose:
The purpose of rooftop detention is to provide quantity or volume control of storm water collected
on the roof of the structure.
Conditions Where Practice Applies:
Rooftop detention can be incorporated into design of most new buildings. In addition, many
existing flattop structures can be modified. Rooftop storage can be used as a quantity control
retrofit technology in urban areas.
Effectiveness:
Rooftop detention is effective for quantity control but does not provide quality control
Advantages:
Rooftop detention can be implemented in urban areas as a retrofit technology for quantity control,
and to correct existing uncontrolled connections to the storm drain system.
Disadvantages:
The building must be structurally designed to accommodate the additional weight of water storage
at the roof level Water quality control cannot be provided unless connected to a ground level
infiltration facility. Effective volume control can only be realized when applied on an area-wide
basis.
KE# 91521.00 . 30 - KAMBER ENGINEERING
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Parking Lot Detention Configurations
Overflow
/ Inlet with
Orifice Plate
Critical Ponding Depth
r; THROUGH A TYPICAL PARKING LOT STORAGE AREA
BTORM SEWER MLET RAISED
ABOVE GRADE
CURB CUTS
PARKING LOT
PERIMETER SWALE
RECESSED LANDSCAPE AREA WITH RAISED
STORM SEWER INLET AND CURB CUTS
Reference:
Florida Department of Environmental Regulation, The Florida Development Manual: A Guide To
Sound Land And Water Management. June, 1988.
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Parking Lot Storage
Description
Method of storm water management volume control which provides temporary storage (ponding)
of storm water runoff in paved parking areas an/or within landscaped islands of parking lots, and
allows a controlled rate of release to receiving streams.
Purpose
Parking lot stage is an alternative to dry pond systems,and basically provides volume control for
the post development peak storm water runoff from the contributing drainage area.
Conditions Where Practice Applies
Parking lot storage is applicable where portions of large, paved surface parking can be used for
temporary storm water storage without interfering with normal pedestrian or vehicular traffic.
Large commercial parking areas and employee parking areas have been used for this purpose.
Advantages
Parking lot storage allows the use of existing or planned parking facilities for temporary volume
control storage, and is a low cost method of providing volume controls. Parking lot storage can
be used in combination with infiltration practices to provide volume control and water quality
control for a site. Additionally, use of parking areas for temporary storage allows site open space
to be used for other purposes.
Disadvantages
Large surface areas are required to provide adequate storage volume without creating unacceptable
water depth in parking areas. Parking lot surfaces are normally subject to heating due to sun
exposure and will transfer heat to stored runoff. Practice is not appropriate where thermal impacts
are a concern.
KE# 91521.00 . 31 . KAMBER ENGINEERING
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