United States 

Environmental Protection 

Agency 

Office of Water EPA 833-D-91-100 

4203 June 1991 

EPA CONSTRUCTION SITE STORMWATER 

DISCHARGE CONTROL 

AN INVENTORY OF CURRENT 

PRACTICES 
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 

KE# 91521.03 
Table of Contents 

1.0 Introduction ................................................... 1 

2.0 Construction Site Stormwater Discharges ............................... 2 

21 Construction Stages ......................................... 2 

2.2 Erosion and Sediment Control ................................. 3 

2.3 Construction Site Housekeeping ................................ 4 

3.0 Stormwater Management Theory and General Design Basis ................... 6 

4.0 Stormwater Management Planning Considerations ......................... 8 

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 
1.0 Introduction 
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 systemwide 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. 

KE# 91521.00 - 1 - KAMBER ENGINEERING 
2.0 Construction Site Stormwater Discharges 
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 arc implemented to protect offsite 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 

the devices. 

KE# 91521.00 -2- KAMBER ENGINEERING 
Stage 4 Installation of Storm Drainage System 

Storm water management facility construction is compictc and storm drains are installed and 

gradually connected to concentrate and divert runoff lo the structure or structures. Erosion 

continues to be moderate to high, and stoRn water runoff volume continues to increase as 

disturbed areas become more compacted. 

Stage 5 Aaivc 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 Stabiiization 

Disturbed areas are stabilized with vegetation or other suitable. non-erosive cover, and erosion 

rates deciine. 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. 

3 a. 

_ 3 . 

4. 

d. 5 

6. 

Perimeter controls 

Slope protection 

Sediment traps and basins 

Drainageway and stream protection 

Temporary stabilization 

Permanent stabilization. 

KEX 91521.00 -3- KAMBER ENGINEEIUSC 
These measures are described in an inventory prepared under Task 2 of this work assignment 

entitled Qdimeot 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 he 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 

23 Constn~ction Site Housekeeping 

Non-structural storm water controls on construction sites focus on methods of preventing nonsediment 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, 

inchde gasoline, oils, grease, paints, raw materials used in the manufacture of wnaete in&ding 

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 schedulu. 

. 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. 

KE# 91521.00 -4- KAMBER ENGINEERING 
. Water used during dust wntrol activities discharged only to on-site 

retention-type sediment ~ntrd devices. 

. Adequately maintained sanitary facilities. 

Routine site housekeeping in accordance with a wnstruction site management plan can minim& 

non sediment related pollutants from cntexing storm water runo& Sediment which enters storm 

water during raintall events, washdown of wnstxuction equipment, or from dust control activities 

can be controlled by properb maintained sediment control dtvices. The remaining sections of this 

report focus on tbc purpose and general design basis of stotm water management facilities which 

control storm water discharges after construction is completed and includes the technology 

inventory of current storm water management practice. 

KEX 91521.00 -5. Kaem ENGINEERING 
3.0 Stormwater Management Theory 

And General Design Basis 
3.0 Stormwater Management Theory And General 

Design Basis 

Water flowing over the land during and immediately following a rainstorm is called stormwater 

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 infiltrate through 

the soil column to replenish groundwater supplies, and increase the amount of rainfall converted 

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 

KE# 91521.00 -6- KAMBER ENGINEERING 
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 qua1 to or less than 

the peak runoff rate that would havt been generated by the site under the predevelopmcnt 

conditions. The volume of storage provided within the facility is controlled by the design storm 

(the amount of rainfall) assumed for calculation of the predevelopment and post-development 

site runoff. and the criteria which specify the allowable release rate. Many localities specify the 

lO-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 IOyear predevelopment. 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 ftrst l/? 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 refened to as BMPs may provide only water quality control. or both quantity 

and quality control within the same facility. 

KE# 91521.00 -7 . KAJ~BER ENCINEERJSC 
4.0 Stormwater Management Planning 

Considerations 
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 infiltration-type 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 are 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. 

KE# 91521.00 -8- KAMBER ENGINEERING 
The concept site plan indicates the proposed location of structuru 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, wnveyance 

and management in control stntcturti, 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 inftuenced 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 wnveyance 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 

impenious 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 ark 

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 

KE# 91521.00 -9- KAMBER ENGINEEJWG 
conveyance of site storm water runoff can be provided to the regional facility. 
5.0 Stormwater Management Practice Inventory 
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. 

5.2 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. 

KE# 91521.00 - 11 - KAMBER ENGINEERING 
pond vttms designed primarily as volume control structures provi& minimal pollutant removal 

capabilities and cannot be considered water quality controls, or BMP facilities. However, pond 

systems can be designed with mended detention, sediment forebays, planted wetlands basins and 

permanent pools, which improve water quality performan= 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 storagcdispmal 

altcrnativts which direct rooftop’ruuoff to underground facilities which discharge to the surroundig 

soils, Infiltration devices are all considered BMI% 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 througb 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 

storagedisposal 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 commerciatindustrial 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 sedimefiration 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 rcicase rate to receiving streams, but provide only minimal pollutant 

removal benefits. These facilities are also not considered BMP facilities. 

KE# 91521.00 - 12 - CAMBER ENGICEFUSG 
APPENDIX 

KE# 91521.00 - 13 - KAMBER ENGINEERING 
NON STRUCTURAL 

STORMWATER MANAGEMENT PRACTICES 

KE# 91521.00 - 14 - KAMBER ENGINEERING 
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 

costly land area necessary for volume controls. 

management BMP. 

Disadvantages: 

storm water runoff quality without committing 

Can be implemented as a retrofit storm water 

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. 

KE# 91521.00 - 18 - KAMBER ENGINEERING 
Fertilizer and Pesticide Application Controls 

Definition 

Managing the application of fettiiizers and pesticides to encourage proper application. 

purpose 

To reduce pesticides and fertilizxxs 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. 

KE# 91521.00 - 19 - K,MBER ENGMEEIWG 
Vegetative Practices 

Description 

Grass filter strips, wooded filter strips, preservation of wooded areas, reforestation areas and treeshrub landscaping instead of “turkaping”. 

To provide vegetated areas between sttuctural development and receiving streams to pdde a 

filtering area for storm water and to promote inftitration 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 appiications 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 filter 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 

Fitter strips are considered BMPs, but provide limited storm water volume control and are usually 

implemented in combination with other volume control storm water management faciiities. 

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 

KE# 91521.00 - 20 - CAMBER ENGINFZRMG 
retrofit situations. 

KE# 91521.00 - 21 - GMBER ENGNEEJUNG 
Schematic of a Fibr Strip 

Reference: 

Metropolitan Washington Council of Governments, Controllinp Urban Runoff: A Practical Manual 

for Plannine and Desimine Urban BMFs, Thomas R. Schueler, July, 1987. 
Grassed Swales 

Description 

Grassed lined channels used to collect and convey storm water t-unofL 

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 physic4 filtration through standing vegetation, with some 

infiltration into undertying 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 tlow 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. 

KE# 91521.00 _ 22 _ k&am ENGI~~EERING 
Schmmatic of a Grassad Swalo 

I 

Reference: 

Metropolitan Washington Council of Govcmmcnts, Controlline Urban Runoff: A Practical Manual 

for Planninn and Desknine Urban BMP’s, Thomas R. Schuclcr, July, 1987. 
Structural Stormwater Management Practices 

KEt 91s21.00 - 3 - KAMEER ENGINE&RING 
Stormwater Detention Wetpond 

Description 

Wetponds are natural or man made depressions which provide storage.of the permanent pool and 

stotm water runoff from a site or drainage area, and allows gradual release of the postdevelopment peak runoff from the site to down stream at-c& 

Wctponds regulate the discharge of post-development site nmo& 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 

Wctponds are appropriate where the contributing drainage area provides sufkient 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 gencralty 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 

preciudes 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. 

?CE# 91521.00 - 24 - KAMBEF~ ENGINEERING 
WET DETENTION SYSTEM 

I’OND CONFIGUFIAT ION - A 

-3 BAFFLE On fl SKIMMEn 7l1CAlMChlf 0 A 

--- 

INFLOW 

-- 

---\ 

- - 

SLOPE IDEStRAEILE) 

w 

SEDIMENT SUMP 

\ ,f (4: 1 MINIMUM) 

LEPER mua 

Source: Southwest Florida Water Management Oirtrict 

Management and Storage of Surface Waters, Permit Information 

Manual, Vol.1, March 1988. 
hbthods For Extending Detmntion Times In Wet Ponds 

- 

kLa 

FW 

. . -. . .’ 

‘.:. 

. ._ 

..-*. -.c 

- 

Front Vhw Side view 

. Metropolitan Washington Council of &wcrtuttcn~ CootrQuiop Urban Runoff. A Pta ctical Manual 

for Plannine and Desknine Urban BMP’s, Thomas R. Scfiueicr, July, 1987. 
WET DETENTION SYSTEM 

POND CONFlGUf-lAl ION - 8 

: 1 SLOPE (I)ESIfIABL E ) 

: 1 MINIMUM) 

SEOIMENT SUMP [JEEl’EfI AllEA 

Source: Southwest Florida Water Management District 

Management and Storage of Surface Waters, Permit Informat!on 

Manual, Vol. 1, March 1988. 
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. 

Dry ponds contain post-development storm water runoff and control the release to pr+evelopmcnt 

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. Additionaity. 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. 

KEI 91521.00 -25- bJdBER ENCWEERING 
Porous Asphalt Pavement 

Definition 

Pavement alternative which allows infiltration of storm water to gravel and soil layers underlying 

tbe pavement surface. 

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. 

Advan tagts 

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 pavementIi.E# 91521.00 -26- UMBER ENGINEERING 
Methods For Extending Detention Times in Dry Ponds 

Acol~cwol* crc 

I01 CI*an-oul 

stow 

., ‘.‘. _‘, 

: .‘T.‘. 

.,..:,:.* ., 

. _. Grarw .‘. 

.,. 

_: 1 .-;.. i . 

Referem 

. Metropolitan %‘asbingtoa thmfd of -0. Con- Utim. A P mafor Planning and Desiminn Urban BMP’s, ‘Thomas R. Schueler, Jub, 1987. 
PERVIOUS CONCRETE PAVEHENT 

TVPICAL mTm --- 

\ PERY/QUS SUBGRADE 

A dose+p via- 04 mdinu wnuwte 

Rcferencc: 

Florida Department of Environmental Regulation. The Florida DcvcloDmcnt Manual: A Guide TO 

Sound Land And Water Manaeement, June, 1988 
4 

4 

4 

4 

rl 

POROUS ASPHALT SURFACE COURSE 

I/2" to 3/4* Aggregate 

asphal tic mfx 

2.5 to 4' thickness typical 

F-lrTCIWRSE 

l/2” Aggretate 

2" Thickness 

RESERVOIR BASE COURSE 

l* to 2” Aggregate 

Vulds volume IS deslgned for 

runoff Retention 

Thickness is based on s toraye 

required 

EXISTING SOIL 

Minimal compaction to retain 

porosity and permeabl I i ty 

POROUS ASPIIALT PAVfNG TYPICAL SECllON 

Modlfled after Dinir, 1980 and City of Aockville, Maryland, 1982 
Infiltration Trenches and Basins 

Description 

Infiltration facilities collect. store and infiltrate runoff through gravel areas and underlying soils. 

To provide both volume control and water quality control, and replica& as much as pms&le, 

predevelopmcnt hydrologic conditions. 

Conditions Where Practice Applies 

Infiltration devices are most applicable on smaller development situ, 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 to 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 ytems can only be implemented on sites with suitable soil and ground water 

conditions. 

KE# 91521.00 - 27 - CLAMBER ENCINEENNG 
EJcample Application of 1 Vegetated Area for 

Pretreatment of Aunoff Prior to Exflltration in Frederick Co. IID 

r 

Stone SUC fdCc 

3’ Mlninua 

Oeyth 

Filter Fabric 

P- “ldth -1 

Reference: 

Florida Department of Environmental Regulation, The Florida DeveloDment Manual: A Guide To 

Sound Land And Water Manaeement, June, 1988. 
-. ___~__ -- 

TYPICAL INFILTRATION TRENCII UNDER GUTTERLESS ROOF 

Source: ilrglnta Sol1 and Yater Conservation C0mlsslon 
Cross-Section of Typical Infiltration/Exfiltration 

Trench System for Parking Areas or Roadways 

LAKE 

\ MOSI I011u11n1s 

f PARKING LOT 

f’ RUNOFF 

1; I ~11hlWA1 I It . 

ovt III I ow- I 

stflllr.l\vAll It 

--- 

) > 

lllrtltlt I v 

“sMNl 1 ” IlOX 

it I 5 

IO 

lttr nt f.trttt 

OYEII, ftItIOlE, MILLS 

AND fwEcounf, fw. 

f IlGlllfF It5 S~@llvf .clrlS 

Reference: 

Florida Department of Environmental Rtguhtion, The Florida Dcvclcmment Manual: A Guide To 

Sound Land And Water Manaeement, June. 1988. 
Examples of Typical Unde;$ound Percolation Systems 

Rettofltting Existing Stofinzcwer SyStcrPs In Orlando, Florida 

tr- aA. R.CC! 

Reference: 

Rotida Depanmcnt of Environmental Rcguiotion, Jl~e Florida Dcveto~mcnt Manuat: A Guide TQ 

Sound Land And Water Mananemct& June. 1988. 
TYYICAL SICIIIIN, SI.AU COVERED TRENCII. DADE COIINTY. FLORIDA 

LONGITUDlNAL SECTION 

NOTES: -- 

1) If material at edge of ditch is unsuitable 

for foundation underslab, clean out and backfill 

with concrete. Depth of backfill varies. 

2) Transition to trench bottom when it 

is lower than catch basin bottom. 

Rcfercncc: 

Florida Dcpmnt Of &*o~cn~ Regulation. The Florida Dcvcloumcnt Manual: A a& ho 

Sound Land And Water Manaeement, June. 1988. 
FRENCH ORAIN (EXFILTRATION TRENCH), DADE COUNTY, FLORIDA 

IOr Ptrl. W!~Open loin1 1’12”. 

Ortrlrp with Rsoling Slrle 

LO~IGITUOINAL SECTION TIIAEISVEIISE SECTIWJ 

E 10' ox tell & spigt pipe 5' lmg is not available, 

pipe, IJI to 24. in dimtm may be substituted. 

3) Tk OYWaCta has tk optiul of installing 

the follahg pipe tJpes: 

Z) Ifcnnc bell 8&pigItpipeis mtlrreda If the length 

ofpipeuwdis water thar5',Y4'smWS Shall be 

III& at Intervals of 2' thm the LppB half of pipe, 5' 

lglgthsm4ybe u5ed for vitrified clayplpe. 

4) Ho pipe perfcratlun for 10' 5 

h l/4' to 3/8" dia. klc, spaced at 2-Y4.t (minim 162 holes per Iin.ft.1 

Reference: 

Florida Department of Etwironrncnul Rcguhtioa B 9 anual: A Gu' 

Sound Land And Water Manancment, June. 1988. 
Lsttlce Unit 

TYPES OF GRI 0 AND MODULAR PAVM NlS 

Source: Vfrgfnla Soil and Water Conservat Ion ~omntsslon 

Poured-In-Place Slab 

Castcllatcd Unit 
Rooftop Runoff Disposal 

Description 

Disposal of rooftop runoff by systems and techniques which avoid or replace direct connections to 

storm or sanitary sewen. Disposal alternatives include underground vaults, cisterns, inEihraticm 

trcnchea and basins. 

To detain roof top nmoff 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 prtidcd, or 

soil and ground water conditions are suitable for the infiltration of runoff. 

Advantages 

When used on an area wide basis, can provide effective volume and quatity control foor rooftop 

nmoff. Particularty 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 lop detention may require building structural improvement 

to accommodate weight of storm water detained temporarily on roof. 

KE# 91521.00 -28. UMER ENGINEERING 
INFIlTRATIoN DRAIM6E OF ROOFTOP 

II II 

. . II 

PLAN VIEW 

Source : Virginia Soil and Water Conservation Carmission 
Dounspoutj--Cl eanouts-, 

Jst water for 

lawn watering or 

3thef purposes 

7 

b ifern 0Wf J 

TYPICAL RnENTION CISTERN 

Source: Virginia Soil and Yattt Conservation Ccmnisrion 
Underground and Other Storage Systems 

KE# 91521.00 -29- KAMBER ENGINEERING 
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 -30- KAMBER ENGINEERING 
Side View 

Trmh Rack Pmtect8’ 

luo6tIuhorifMs 

Thtrd CharnOw 

Rclntofcod 

Concrora 

Conrlrucrton 

Schematic of a Water Quaiity Inlet, Rockville Percolating 

Inlet Design 

Top View 

t ouuet IO 

curb met to 

First ChamMr 

R Stofmomn System 

4 , 

Side View Inlet 

Scotmenr Chrmeer 

Slormarrtn 

Oulltl 

Gravel Layer 

SOII 
Underground Storage 

DCfidtiOn: 

Underground storage is the practice of storing storm water runoff in underground vaults, over&& 

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 Practia Appiits: 

Underground storage is applicable where there is a lack of surface storage area or the land cust 

is greater than that of underground storage construction. 

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 spaa iimitcd 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- KAMBm ENoLNEERrNc 
Rooftop Detention 

Definition: 

Rooftop detention facilities provide temporary stormwater storage on flat roof surfaces ailtig 

gradual release of runoff to ground-level storm drain systems. 

The purpose of rooftop detention is to provide quantity or volume control of storm water aAkctcd 

on the roof of the structure. 

Conditions Where Practice Applies: 

Rooftop detention can be incorporated into design of most acw buildings. In addition, many 

existing flattop structures can be modified. Rooftop storage can be used as a quantity control 

retrofit technology in urban areas. 

Effcctivcntss: 

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. 

Disadvan taga: 

The building must be structurally designed to accommodate the additional weight of water storage 

at the roof IcveL Water quality control cannot bc provided unless connected to a ground level 

infiltration facility. Effective volume control can only be realized when applied on an area-wide 

basis. 

KEN 91521.00 -M- KcrMBER ENGINEEUNG 
Parking Lot Detention Configurations 

-- . . .-- . .-SW 

. . 

. 

5 EZTIOF: THROUW A TYPICAL PARKING LOT STORAGE AREA 

BTORM SEWER HLEf RAISED 

ABOVE GRADE 

CURB CUTS 

PERMETER SWALE 

RECESSED LANDSCAPE AREA WITH RAISED 

STORM SEWER INLET AND CLIM CUTS 

PARKING LOT 

Reference: 

FIorida Department of Environmental Regulation. The Florida Dcvclooment Manual: A Guide 

Sound Land And Water Mananemcng, June, 1988. 
Parking Id 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 i&n& of parking lots, and 

allows a wmroUed rate of rckasc to receiving streams. 

Parking lot stage is an alternative to dry pond systems.and basically provides volume control for 

the post development peak storm water nmoff 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 

wnrrol for a site. Additionally, use of parking areas for temporary storage allows site open spaa 

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. 

KEN 91s21.00 - 31 - WBER ENGINEERING