retention ponds - .net framework

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Retention Ponds

Florida-Friendly Landscaping™ Hillsborough County Extension

University of Florida, IFAS

Retention Ponds – Quick Facts

Legislation was enacted in the 1980’s, which required treatment of stormwater

Most were built within the past 20 years Largest number in Florida Commonly referred to as “lakes”

Image source: Winnipeg.ca.

Retention vs. Detention Ponds

Retention ponds are designed to RETAIN water. – Permanent pool of water – Water level fluctuates in response to precipitation

and runoff from the contributing areas.

Retention vs. Detention Ponds

Retention ponds are designed to RETAIN water.

Detention ponds are designed to DETAIN water. – Slows down water flow – Holds stormwater for a short period of time – Usually dry, except for during or after rain

Watersheds

It’s All Connected - Even if you don’t live on the waterfront, your land is still directly connected to a nearby waterbody.

Like a Bowl - A Watershed is the area of land where all of the water that is under it or drains off of it goes into the same place.

Aquifer Connection – All watersheds are connected to the underground aquifer, which supplies most of Florida’s drinking water.

Image source: Marmaton Wraps.

Stormwater Ponds

Water after a storm or heavy rain event either:

Percolates (i.e. sinks into) through soil, recharging groundwater (or the aquifer) directly

Original image source: FAO – United Nations.

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Stormwater Ponds

Water after a storm or heavy rain event either:

Percolates (i.e. sinks into) through soil, recharging groundwater (or the aquifer) directly OR Runs off of impervious surfaces, where excess water is collected in the retention pond

Original image source: FAO – United Nations.

Stormwater Management Systems

Prevents flooding by detaining stormwater after a storm event

Improves water quality by providing a natural filter for pollutants

Wildlife habitat Recreational activities and

a neighborhood amenity

Image source: University of Florida.

Pond Maintenance - Now What?

Turned over to communities to maintain Responsibility applies to all homeowners Ignorance of the importance of pond

maintenance Affects pond lifespan, future maintenance

costs and property values Communities and environment downstream

Retention Ponds – Sad Reality

In the process of dying Will have to be re-dredged Lifespan: 20 – 25 years

Lake or Pond Eutrophication Process of nutrient

enrichment of lakes – Nitrogen and Phosphorus stimulate

the growth of aquatic plants, including algae.

Caused by natural and human factors – Wastewater disposal – Agricultural practices – Urban run-off (From yards, golf

courses, shopping centers and roads)

Repercussions downstream – Flooding – Pollution discharge


Eutrophication Affects: Algae Quantity and type of aquatic

plants Water quality Water clarity and depth Fish populations Note: Sometimes Beneficial

Original image source: University of Florida.

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Pollution Point Source

– Readily identified source – Contribution greatly lessoned, due to

environmental regulations

Non-Point Source – Not easily traced to source

Pollution Sources – Urban Settings Construction activities Degrading roads/pavement Emissions from motor vehicles Vegetation, which as leaves,

grass and other yard debris Litter and trash, including pet

wastes Chemicals

– Fertilizers – Pesticides – Herbicides

Wastewater, including overflow from septic systems

Algae Single celled, almost

microscopic organism Live in large colonies Not exactly a terrestrial plant –

No roots, stems or leaves Performs photosynthesis Similar growth requirements as

plants – Nutrients – Light

30,000 species

“Good” vs. “Bad” Algae 4 Types

– Cyanobacteria – blue-green – Chrlorophyta – green – Phaephyta – brown – Rhodophyta - red

“Good” algae – Includes many types of green algae – Indicates a healthy water system

“Bad” algae – Includes red, brown and blue-green

varieties – System is out of balance

“Good” Algae - Chara Attaches to pond sediments Found 2 – 3’ below surface Indicator of clear water Forms mats when free-floating Helpful to stormwater systems Take care not to kill off Phosphorus is key:

– In waters with low levels of P (< 20 micrograms/L)

– Filamentous green algae requires high P levels

Stormwater Pond Best Management Practices (BMP’s)

General definition: Methods or techniques found to be the most effective and practical means in achieving an object (such as preventing or minimizing pollution) while making the optimum use of available resources.

In terms of stormwater management: Both structural or engineered control devices and systems (e.g. retention ponds) to treat polluted stormwater, as well as operational or procedural practice (e.g. minimizing use of chemical fertilizers and pesticides).

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Stormwater Pond Best Management Practices (BMP’s)

Keep inflow and outflow structures clear Weed control, including invasive vegetation Shoreline stabilization Pollution prevention - Keep anything other than

water from entering the stormwater system Establish a maintenance-free buffer zone Dredging and repair Monitoring

BMP’s – Public Acceptance is Key

Come to consensus – Serves/benefits all members of a community – Can adversely affect all

Prioritize intended uses for ponds – Top priorities – flood prevention and pollution control – Other uses – irrigation, recreation and marketability

Create community-wide awareness of the program Explain how individuals can help implement the plan Monitor the program and obtain feedback

BMP’s – Dredging

Definition: To remove sand, silt, mud, muck, etc. from the bottom of a stormwater pond or other waterbody.

BMP’s – Dredging

Inevitable Expensive Long and complicated permitting process Harmful to fish and wildlife Dredged “muck” is harmful to environment

Stormwater Pond Restoration Treatments

(Buying time before re-dredging)

Aeration


Aeration Floating Wetland

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Aeration Floating Wetland Grass Carp


Aeration Floating Wetland Grass Carp Copper Sulfate


Aeration Floating Wetland Grass Carp Copper Sulfate Dye

Restoration Treatments - Aeration

Oxygenates water Mixes water to prevent stratification Controls accumulation of pond bottom muck Can add 20 – 25 years to life of pond Fountain ≠ Aeration Should be run 24 hours a day Most effective treatment method High cost

Restoration Treatments – Floating Wetland

Plastic grid filled with native aquatic plants and anchored in place within the pond

Competes with algae for pond nutrients Harvesting of plants, necessary to remove

accumulated nutrients Aesthetically pleasing Effective

Restoration Treatments – Grass Carp

Biological control – herbivorous fish Sterile – live 10 years “Grazer” – feeds on surface and shallow water plants Not effective in controlling “bad” algae Prefers Hydrilla and Chara Effective on certain types of nuisance plants Low cost

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Restoration Treatments – Copper Sulfate

pH of water needs to be measured prior to treatment

Can cause Oxygen concentrations to drop Can cause fish kills Linked to methylmercury Short-term - Can be effective Long-term - Starts a negative self-feeding cycle Relatively inexpensive Not recommended for low alkalinity or low oxygen

ponds

Restoration Treatments - Dyes

Darkens the water Reduces sunlight penetration Limits plant growth Safe for aquatic wildlife Spreads readily Effective Inexpensive

Key to Pond Maintenance – Control What Enters the Pond

Proper disposal of trash and waste


Proper disposal of trash and waste Appropriate use of pesticides, herbicides and

fertilizers



fertilizers Apply fertilizer only when grass is actively

growing




growing Use fertilizer formulations that are at least

50% slow release

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50% slow release Enforce municipal “illegal dumping”

ordinances






ordinances Post “No littering” signs that include a phone

number






ordinances Post “No littering” signs that include a phone

number Periodic street sweeping

Maintenance-Free Zone

Create a low maintenance buffer zone – At least 10 feet wide – Can include low maintenance plants – Remove invasive species

Purpose – Natural filter – Attracts wildlife – Prevents erosion

Buffer Zone Considerations

Never grow grass to the edge of pond (or stormwater drain)

Don’t mow, fertilize or apply pesticides Don’t apply irrigation (after plants are established) Avoid loose grass clippings Prevent pet wastes from reaching water body

Aquascaping

Practice of using aquatic and wetland plants to landscape in and around water.

Many counties in Florida promote and require Aquascaping of stormwater ponds.

Maintenance – Aquascaping, like gardening and landscaping, must be maintained.

Image source: Orange County, FL.

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Aquascaping - Purpose

Pollutant filtration Erosion control Wildlife habitat Invasive plant species

control Aesthetic value


Aquascaping

Determine average water level on a yearly basis Measure maximum depth in the planting areas Start in deepest zone and work toward shore Marginal and transitional plants in buffer zone

Aquascaping – Plants

Submersed – grow entirely under water – cannot survive out of water.

Bacopa caroliniana, Lemon Bacopa


Submersed – grow entirely under water and – cannot survive out of water.

Ludwigia repens, Red Ludwigia


Floating – float free on the water – rooted in the ground with leaves floating on the surface

Nelumbo lutea, American Lotus


Floating – float free on the water – rooted in the ground with leaves floating on the surface

Nymphaea odorata, Fragrant Waterlily

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Emergent - rooted in the ground – Aquatic plants

need to be rooted in the water leaves and flowers project above the water

– Canna flaccid, Golden Canna

Aquascaping – Emergent Plants Aquatic

– need to be rooted in the water – leaves and flowers project above the water

Iris virginica, Blue Flag Iris



Pontederia cordata, Pickerelweed



Sagittaria lancifolia, Duck Potato

Aquascaping – Emergent Plants Aquatic Short-stemmed marginal plants

– low growing bog-type plants that grow well on wet mud or sand Drosera cappillaris, Pink Sundew

Aquascaping – Emergent Plants Aquatic Short-stemmed marginal plants

– low growing bog-type plants that grow well on wet mud or sand Eriocaulon spp., Pipeworts

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Aquascaping – Emergent Plants Aquatic Short-stemmed marginal plants Marginal or transitional plants

– grow on the interface of wetland and upland habitats

– prefer changing water levels Cephalanthus occidentalis, Buttonbush



– prefer changing water levels Helianthus angustifolius, Swamp Sunflower



– prefer changing water levels Muhlenbergia capillaris, Gulf Muhly Grass



– prefer changing water levels Zephyranthes atamasco, Rain Lily



– prefer changing water levels Taxodium distichum, Bald Cypress

Retention Ponds In the process of dying Will have to be re-dredged Lifespan: 20 – 25 years Buy time by:

– Aeration system – Do not grow grass up to water’s edge – Establish maintenance-free zone – Prevent pollutants from entering

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Resources Adopt-A-Pond Program, Hillsborough County – http://www.hillsborough.wateratlas.usf.edu/AAP/ Center for Aquatic and Invasive Plants, University of Florida Institute of Food and Agricultural Sciences – http://plants.ifas.ufl.edu/ Clemson Cooperative Extension – http://www.clemson.edu/extension/natural_resources/water/stormwater_ponds/ The Florida-Friendly Landscaping Guide to Plant Selection and Landscape Design – Southwest Florida Water Management District – http://www.swfwmd.state.fl.us/publications/type/all The Florida Yards & Neighborhoods Handbook – Florida-Friendly Landscaping™ – http://fyn.ifas.ufl.edu/publications.htm

Resources (cont.) IslandWalk Community DVD – Dr. Herb Schuchman, Co-chair, Lake Committee – email: [email protected] Stormwater Systems in Your Neighborhood brochure – Southwest Florida Water Management District - http://www.swfwmd.state.fl.us/publications/type/all

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