Strategy Class

Implementation Strategy

Applications

Benefits

Cost

Barriers to Implementation

Green

Bioretention planter

Local, small scale, easily implemented in developed areas

Protects property, treats runoff

$2500 ea

Limited volume disposed of, so many are needed, maintenance

Green

Tree box filter

Local, small scale, easily implemented in developed areas

Protects property, treats runoff

$2500 ea

Limited volume disposed of, so many are needed, maintenance

Green

Rainwater harvesting

Local, small scale, easily implemented in developed areas

Protects property, treats runoff

Under $5000

Limited volume disposed of, so many are needed, maintenance

Green

Vegetated roof

Specific to a building, absorbs water, reduces runoff

Protects property, treats runoff

$100/sf

Requires irrigation if insufficient rainfall occurs

Requires runoff control if too much rainfall occurs

Green

Bioswale

Parking lots, runoff from development—primarily treatment for discharge to another system

Protects property, treats runoff

$20 K/ac

Maintenance, limited volume disposed of, used mostly for treatment

Gray

Pervious paving

Parking lots, patios, driveways, anything except paved roads due to traffic loading

Reduces roadway and parking lot flooding

$10 - 20/sf, requires bumpers and sub-base to maintain paver integrity

Must be maintained via vacuuming or the perviousness fades after 2 - 3 years

Green

Detention

Common for new development, but difficult to retrofit; limited to open areas

Removes water from streets, reduces flooding

$200 K/ac

Land availability, maintenance of pond, discharge location

Uses up land that could otherwise be developed

Green

Vegetated wall

Used on walls of buildings and retaining walls

Protects property, treats runoff

$30/sf

Requires irrigation if insufficient rainfall occurs

Requires runoff control if too much rainfall occurs

Gray

Exfiltration Trench

Any low-lying area where stormwater collects and the water table is more than 3 ft below the surface; densely developed areas where retention is not available, roadways

Excess water drains to aquifer, some treatment provided

$250/ft

Significant damage to roadways for installation, maintenance needed, clogging issues reduce benefits

Green

Dry Swale

Parking lots, runoff from development—primarily treatment for discharge to another system

Protects Property, treats runoff

$200 K/mi

Maintenance, limited volume disposed of, mostly for treatment

Green

Retention Ponds

Common for new development, but difficult to retrofit; limited to open areas

Removes water from streets, reduces flooding

$200 K/ac

Land availability, maintenance of pond, discharge location

Uses up land that could otherwise be developed

Green

Rain Gardens

Local, small scale, easily implemented in developed areas

Protects property, treats runoff

$20 K/ac

Limited volume disposed of, so many are needed, maintenance

Gray

Infiltration Trench

Low lying areas that collect stormwater, but the water table is just below the surface meaning that retention and exfiltration trenches will not work properly

Excess water is drained to pump stations, creating soil storage capacity to store runoff, soil treatment

$250/ft plus pump station

Significant damage to roadways for installation, maintenance needed, clogging issues—must discharge somewhere (pump station, detention pond)

Green

Oversized pipes

Local solution—not watershed level, holds water to reduce flooding

Protects property and roadways

$350/ft of more

Sediments, maintenance needs, lack of means to flush, cost

Gray

Central sewer installation

All areas where there are septic tanks. Mostly a water quality issue

Public health benefit of reducing discharges to lawns, canals and groundwater from septic tanks

$15,000 per household

Cost, assessments against property owners, property rights issues

Green

Filter strips

Localized

Protects property, treats runoff

$50 K/mi

Does not address flooding, treatment/water quality measure

Green

Flood prone property acquisition

Regional agency—could be any low-lying areas

Removes flood prone areas from risk

$2 K - $100 K/ac depending on whether it is already developed

Difficult to implement if occupied, issues with willing sellers, cost, lack of funds for acquisition

Gray

Class I injection wells

Any low-lying area where stormwater collects, and there is sufficient land to permit, install and operate a Class I well-limited

Means to drain neighborhoods— potentially arge volumes

$3-6 million depending on size/depth

Needs baffle box, injection zone may not be available, requires a permit, may compete with water users

Green

Underground storage

Common for new developments, but difficult to retrofit

Storage of excess runoff from rainfall, can be used for irrigation, can sit under parking lots, unobtrusive

$2/gal

If the tank is full, there is no storage

Green

Constructed wetlands

Where there is low lying flood prone land that can be converted into wetlands

Reduces flooding by providing a low-lying area for water to go

$200 - $1 M/ac

Water quality, permitting, monitoring costs, maintenance

Gray

Pump stations

Any low-lying area where stormwater collects, and there is a place to pump the excess stormwater to such as a canal; common for developed areas

Removes water from streets, reduces flooding

Start at $1.5 to 5 million each, number unclear without more study

NPDES permits, maintenance cost, land acquisition, discharge quality

Gray

Armored sewer systems

Any area where gravity sanitary sewers are installed

Keeps stormwater out of sanitary sewer system and reduces potential for disease spread from sewage overflows

$500/manhole

Limited expense beyond capital cost

Gray

Raised roadways

Limited to areas where redevelopment is occurring areawide due to ancillary impacts on adjacent properties

Keeps traffic above floodwaters, access for emergency vehicles, commerce

$2 - 4 million/lane mile

Runoff, cost, utility relocation

Gray

Class V gravity wells

Any low-lying areas where stormwater collects and is located where saltwater has intruded the surficial aquifer beneath the site

Means to drain neighborhoods, limited volume

$250 K each

Needs baffle box, limited flow volume (1 MGD), zone for discharge may not be available, permits, water supply wells

Gray

Canals

Limited

Means to drain neighborhoods, provides treatment of water

$2 million/mile

Land area, flow volume, maintenance, ownership, capacity issues due to sea level rise pressure

Green

Aquatic zones

Any low-lying or flood-prone area that is undeveloped and can store large volumes of water

Place to store large volumes of water

$200 K/ac

Must be maintained, cost, impact on property owners

Gray

Levees

Regional issue—along rivers, lakes, impoundments

Protects widescale property

$ millions

Must be maintained, must be continuous, must be planned for extreme events (i.e. Hurricane Katrina showed that New Orleans planning horizon was not sufficient)

Gray

Lock structures

Regional (WMD) responsibility

Keeps seawater out, reduces saltwater intrusion

Up to $10 million, may require ancillary stormwater pumping stations at $2 - 5 million each

Permitting, private property rights arguments

Gray

Sea walls

Barrier islands and downtown coastal areas

Protects property

$1200/ft

Private property rights, neighbors

Green

Polders

Barrier islands and downtown coastal areas

Provides storage for coastal waters

$200 K/ac

Permitting, land acquisition

Gray

Surge barriers

Coastal communities—large footprint

Protects property

>$1 B

Cost, open ocean access challenges, property rights

Green

Enhanced

wetlands

Where there is an existing wetlands area that can be augmented

Reduces flooding by providing a low-lying place for water to go

$200 - $1 M/ac

Water quality, permitting, monitoring costs, maintenance, ecosystem impacts

Green

Revetments

Retention, helps maintain the storage volume, in conjunction with other measures

Improves walls of retainage

Varies based on material, depth, wall height

Land area, maintenance

Policy

Changes in land use

Applicable universally

Achieves flood risk mitigation by djusting permitted land use

Low but may incur private property rights conflicts and litigation

Private property rights conflicts and litigation

Gray

Roadway base protection

Low-lying areas, coastal communities

Protects roads and access routes

$1 million per lane mile

Cost, adjacent properties become uninsurable

Policy

Enhanced elevation of buildings or land abandonment

Developers would implement this for new construction

Reduced flood risk

Varies

Potential issues with building structure or latticework, and existing homes that are not elevated