Be st Ma na g e me nt Pra c tic e s fo r Sto rmwa te r Qua lity T - - PowerPoint PPT Presentation

Be st Ma na g e me nt Pra c tic e s fo r Sto rmwa te r Qua lity T re a tme nt in Urb a n Se tting s

Lower Mississippi River WMO – September 2017

Sto rmwa te r 101

– Impervious surfaces (pavement, parking lots, etc.): quickly produce large volumes of runoff, causing erosion and flooding – Runoff carries pollutants (e.g., sediment, phosphorus) to surface waters – “First flush” runoff contains higher concentrations of pollutants

• Nutrients (phosphorus, nitrogen)

‒Can cause excess algae growth

• Total suspended solids

(particulate material such as sediment) ‒Impacts water clarity

• Chloride (salt)

‒Can affect aquatic life

Co mmo n sto rmwa te r runo ff-re la te d wa te r q ua lity impa irme nts

Stormwater BMPs

Traditional Engineering

Wet Ponds Infiltration Basins Stormwater Wetland Swales

Green Infrastructure

Rain Gardens Tree Trenches Bioinfiltration Basins Permeable Pavement Green Roofs Stormwater Planters

Structural BMPs

Underground Infiltration Vaults Chambers

Perforated Pipes Filtration/ Sedimentation

In-Catch-Basin Devices Sedimentation Filtration Media Beds Iron-Enhanced Sand

Spent Lime Systems

Good Housekeeping

BMP fa mily tre e

Not all best management practices (BMPs) work for every site; not all BMPs created equal

Go o d ho use ke e ping (po llutio n pre ve ntio n)

• Non-structural programs/action
• Street sweeping
• Salt/chemical storage practices
• Training and education
• Maintenance/operation

procedures

T ra ditio na l e ng ine e ring

• Proven design techniques that

provide effective water quality treatment

• Often requires significant footprint
• Easy to implement at time of

development

• Difficult to retrofit

Traditional Engineering

Wet Ponds Infiltration Basins Stormwater Wetlands Swales

T ra ditio na l e ng ine e ring : we t po nds

• Popular in early 1990s
• Proven design techniques (NURP)
• ~50% total phosphorus reduction
• ~85% total suspended solids reduction
• Easy to implement at time of

construction

• Provide water quantity benefits
• Large footprint

Image: Minnesota Pollution Control Agency

T ra ditio na l e ng ine e ring : sto rmwa te r we tla nds

• Constructed BMP (not discharge to

existing wetland)

• Treatment concept/performance

similar to wet ponds

• Education and habitat value
• Pretreatment is recommended
• Water quantity benefits
• Large footprint

Image: Minnesota Pollution Control Agency

Sto rmwa te r pre -tre a tme nt

• Reduce maintenance and preserve long-term functionality
• Remove trash, debris, and coarse sediments, organic materials
• Various pretreatment types:

Images: Minnesota Pollution Control Agency

Sediment Forebays Screens Sump Manholes Vegetated Filter Strips

T ra ditio na l e ng ine e ring : infiltra tio n b a sin a nd swa le s

• Various types
• Dry pond
• Trench
• Swale
• Pretreatment is recommended
• Requires permeable soils
• Limited water quantity benefits

Image: Minnesota Pollution Control Agency

• Mimics natural hydrology
• Science is still developing
• Retrofit opportunities
• Lower impact/more sustainable

Gre e n infra struc ture

Green Infrastructure

Bioinfiltration Basins Rain Gardens Green Roofs Tree Trenches Permeable Pavement Stormwater Planters

Gre e n infra struc ture : ra ing a rde ns a nd b io infiltra tio n

Image: Living Streets project, Maplewood

• Variety of applications

‒Small scale ‒Retrofit potential

• Visually appealing
• Treat small volumes
• Requires permeable soils
• Maintenance often delegated

Gre e n infra struc ture : ra ing a rde ns a nd b io infiltra tio n

Images: Burnsville and Minneapolis

Gre e n infra struc ture : g re e n ro o fs

Image: Minneapolis College of Art and Design

• Layered substrate supporting

plant growth

• Volume reduction through

evapotranspiration

• Filtration through substrate
• Retrofit opportunities
• Maintains usable space

Gre e n infra struc ture : tre e tre nc he s a nd tre e b o xe s

Image: Green Line tree trenches, St. Paul

• Often use engineered

substrate or structural cells

• Filtration through substrate

with underdrain

• Pretreatment recommended
• Maintains usable space
• Aesthetically pleasing

Gre e n infra struc ture : pe rme a b le pa ve me nt

Image: Minnetonka Civic Center

• Many types
• Pervious concrete
• Porous asphalt
• Permeable pavers
• Reduces runoff by replacing

impervious surface

• Maintains usable space
• Requires frequent maintenance

Structural BMPs Underground Infiltration

Chambers Vaults

Struc tura l BMPs: unde rg ro und infiltra tio n

Perforated Pipes

Image: Minnesota Pollution Control Agency

• Variety of shapes and sizes

‒Vaults ‒Chambers ‒Perforated pipe networks

• Can store/infiltrate large volumes
• Requires permeable soils
• Relatively expensive
• Allows for land use above

Unde rg ro und infiltra tio n syste ms

Image: Minnesota Pollution Control Agency

• Large pre-cast concrete vaults
• Customizable sizes, modular design
• Used for infiltration, storage, reuse
• Requires pretreatment chambers

Images: StormTrap Stormwater Management; 37th Avenue, Minneapolis

Unde rg ro und infiltra tio n: va ults

Triton Stormwater Chamber

• Plastic dome chambers of

various sizes –Grid pattern with multiple layers possible to accommodate large storms –Requires “header row” for sedimentation and clean-out

Images: Triton Stormwater Solutions

Unde rg ro und infiltra tio n: c ha mb e rs

Struc tura l BMPs: filtra tio n/ se dime nta tio n

Structural BMPs Filtration/ Sedimentation

Sedimentation In-Catch-Basin Devices Filtration

In-catch-basin device

• Inserted into or replaces stormwater catch basin
• Uses a variety of treatment mechanisms

‒ Filtration (screens/cartridges filter suspended pollutants) ‒ Settling (water movement/detention used to settle/capture pollutants)

• Best used for retrofit/where space is limited

Requires regular inspection and maintenance to remain effective!

• Several proprietary technologies
• Stormceptor
• Downstream Defender
• Used as pretreatment for

downstream infiltration BMPs

• Alternative to sump catch basins

Image: Hydro International

Se dime nta tio n: Hydro dyna mic se pa ra to rs

• Effective at removing

large particles

• Ineffective at removing

dissolved nutrients/very fine particulates

• Requires yearly inspection

and regular maintenance

• Relatively expensive

Images: Hydro International

Se dime nta tio n: Hydro dyna mic se pa ra to rs

• Several proprietary

technologies

• Stormceptor
• Downstream Defender
• Effective at removing

large particles

• Ineffective at removing

dissolved nutrients/very fine particulates

• Requires yearly inspection

Images: Hydro International

Se dime nta tio n: Hydro dyna mic se pa ra to rs

• Large pre-cast concrete

chamber with multiple removal mechanisms

• Uses gravity, hydrodynamic

separation, adsorptive filtration

• Filtration accomplished via

porous concrete elements that last approximately 5 years

• Proven effective for TSS, heavy

metals, and dissolved nutrients

Image Credit: Watertectonics

F iltra tio n: E c o Sto rm Plus b y Wa te rte c to nic s

• Effective, but relatively

expensive

• Requires a small footprint, but

can be scaled to treat a larger watershed

Image: Watertectonics

Removal Efficiency

Total suspended solids (TSS) >80% Zinc (Zn) >90% Lead (Pb) >95% Copper (Cu) >80% Phosphorus >60%

F iltra tio n: E c o Sto rm Plus b y Wa te rte c to nic s

F iltra tio n: SAF L Ba ffle b y Upstre a m T e c hno lo g ie s

• Perforated screen inserted in to

catch basin

• Prevents resuspension and

wash out of sediments previously captured by sump catch basin

• Allows for the retrofitting of

most existing sump catch basins

• Designed to be maintained

twice per year

Image: Upstream Technologies

Structural BMPs Filtration/ Sedimentation

Iron-Enhanced Sand Filter Media Beds Spent-Lime Filter

F iltra tio n: Me dia b e ds

Image: Ramsey-Washington Metro Watershed District Image: Minnesota Pollution Control Agency

Iron-Enhanced Sand Filter Spent-Lime Filter

Image: MPCA

F iltra tio n: I ro n-e nha nc e d sa nd

Iron-enhanced sand filter media Filter media drain tile to outlet structure Overflow outlet structure to storm sewer Perimeter underdrain to

• utlet structure

(to prevent ground water intrusion)

• Filtration basin similar to rain garden or modified wet pond
• Employs underdrains embedded in sand mixed with iron

(filings or granular)

• Numerous local examples in several

configurations

• Dissolved phosphorus bonds to

iron as it passes through the filter

• Research shows up to 90% removal
• f dissolved phosphorus
• Critical that water level draws down

within 48 hours to prevent conditions that can release bound phosphorus (filter needs to dry out)

Iron enhanced sand filter, Maplewood

F iltra tio n: I ro n-e nha nc e d sa nd

Image: Ramsey-Washington Metro Watershed District

• New technology using available

waste material—granular lime previously used to treat drinking water

• Highly effective at removing

dissolved phosphorus – up to 95%

• Effective lifespan being researched

Wakefield Lake Spent Lime Filter, Maplewood

Image: Ramsey-Washington Metro Watershed District

F iltra tio n: Spe nt-lime

Que stio ns?