why is storm water a problem?

Stormwater, Floodplain and Wetlands

Newly Elected Officials Course

January 28, 2006

Andrew W. Blenko, P.E., J.D.

Why is Storm Water a Problem?

Increased runoff due to development (quantity and flooding)


Development =

Impervious Surfaces =

Increased Runoff =

Flooding


Damage to your infrastructure:

Damage to your residents:


Pollution from contaminants


Pollution from illicit discharges


Erosion and Sedimentation


Reduced Groundwater Recharge

Persons who develop land must:• Assure the maximum rate of runoff is no greater after

development than before OR;

• Manage quantity, velocity and direction of resulting storm water runoff in a manner which otherwise adequately protects health and property from possible

injury.

Act 167 of 1978Pa. Stormwater Management Act

Reading a Stream Hydrograph A hydrograph presents a picture of what is happening to the volume of

water in a stream during and after a rainfall event.

Development increases the Amount of Runoff and Decreases Infiltration

Development Increases the Velocity (Rate) of Runoff

Development increases the Peak Flow Rate and decreases the Travel Time

Traditional Approach has been to Detain Runoff so Peak Rate of Runoff is Maintained

Traditional Approach has been to Detain Runoff so Peak Rate of Runoff is

Maintained

New Approach Looks at Reducing Runoff Volume and Maintaining Quality of Stormwater

Runoff

What is a Watershed?

• A contiguous land area that drains to a common point

• A Geographic Boundary, not a Political Unit

• Encompasses all water systems• Storm Water• Sanitary• Water Supply

Watershed Characteristics:

• Slopes

• Vegetation

• Land Cover• Forest• Meadows• Pavement• Floodplains• Wetlands

•

• Hydrology

• Soils

• Land Use• Agriculture• Residential• Industrial• Open

Many Municipalities are Living with Recurring Problems due to Poor

Stormwater Management in the Past –

Solutions must involve all communities in a watershed since

the problems cross municipal boundaries.

Maintain Stream Capacity

Stormwater Management Philosophy

Comprehensive

• Based on a Plan• Preventative• Multi-Purpose• Volume and Rate

Control Oriented

Traditional

• Remedial• Site Oriented• Conveyance

Oriented• Single

Purpose• Piecemeal

Alternative Management Techniques

Municipal and Regional PlanningMunicipal and Regional Planning• Comprehensive Planning

• Open/Green Space• “Stormwater Space”• Acknowledge Act 167 SMPs in Plans• Regional Stormwater Facilities

• Zoning and Ordinances• Long-Term Property Buy-Out Plans in Floodplains• Law Suits over Upstream Stormwater Management

Practices

Making Up for Past Sins:

Penn Township, Westmoreland County

Berlin Road Dam• Built to alleviate flooding of

approximately 20 homes, (including first floor flooding of 5 homes)

• Phase I included elliptical drainage pipes and wetland mitigation; construction costs were $238,000

• Phase 2 included a 5-acre detention facility to control stormwater from approximately 100 upstream acres

• Total Phase 2 construction cost of $451,000

• One of the first stormwater projects funded by PennVest

• Completed in 2002


Penn Township, Westmoreland County

Cortina Marie Detention Pond

• Resulted from a law suit by 9 property owners repeatedly flooded

• Township purchased 5 acres of prime real estate for $404,000

• Total project cost including land acquisition, engineering, and permitting - $1.14 million

• Funded with a PennVest loan

• Completed in 2003


Kennedy Township, Allegheny County

Pine Hollow Detention Basin• Protects the Township of Stowe

and the Borough of McKees Rocks

• Constructed 1998-99

• Cost $237,000

• Financed by the Allegheny County Authority for Improvements in Municipalities

• 5-year term

• All costs born by the Township of Kennedy

Good Stormwater Management Saves Money!!!

We Need to be Creative and Think Outside the Box

Stormwater Phase II Program

(Cities with <100,000 Population)

•MS4 – Municipal Separate Storm Sewer System

•Storm Sewer Discharges must be Permitted in Urban Areas

•Requires General or Individual Permit from PADEP


Six Minimum Controls:

• Public Education and Outreach

• Public Participation and Involvement

• Illicit Discharge Detection and Elimination

• Construction Site Runoff

• Post-Construction Runoff

• Pollution Prevention/Good Housekeeping


Public Education, Participation & Outreach


Illicit Discharge Detection and Elimination


Post-Construction Runoff Controls


Municipal Good Housekeeping

Wetlands

Rule One: Avoid Them!

• Wetland issues are regulated jointly by PADEP and the USACOE

• Wetlands are Beneficial

• Even a small disturbance requires regulatory review

• 100 and 500-Year Floodplains delineated by FEMA in Flood Insurance Rate Study Maps

• Original maps in our area done in late 1970s

• Generally Updated every ten years

Floodplains

LOMR – Letter of Map Revison

LOMA – Letter of Map Amendment

Floodplains

• Issued by FEMA as a result of Changed Condition

• Requires a HEC-RAS or other hydraulic study to Justify

Floodway – cross section needed to convey runoff from design storms

Floodplain – Areas inundated with water during design storms

Floodplains

Never build in Floodway; Okay to build in Floodplain as long as first floor is above flood elevation and structure designed to withstand flooding

Questions?

Thank you for your interest in serving your communities and making them a

better place to live and work!

why is storm water a problem?

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