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Pennsylvania Act 167 Stormwater Management
Planning Program

• PRESENTED AT
• NEW DIRECTIONS IN STORMWATER MANAGEMENT
• VILLANOVA UNIVERSITY
• August 8, 2002
• Durla Lathia, P.E.
• Bureau of Watershed Management

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Pa Storm Water Management Program- Background

• 1978 Legislative Findings
• Pa General Assembly found that inadequate
  management of stormwater runoff from development
  activities increases flood flows and velocities,
  adversely affects water quality of receiving
  streams and groundwater, causes stream bank
  erosion and diminishes groundwater recharge.

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Legislative Findings-Contd.

• A comprehensive Program to manage stormwater
  runoff, based on the watershed level management
  strategy, is necessary to protect public health,
  safety and welfare, and the protection of the
  people of the state and their resources and the
  environment.

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Pennsylvania Stormwater Management Program
Act 167 of 1978
Control of Stormwater Runoff from Land
Development Activities Considering Overall
Watershed Management Approach, Irrespective of
County or Municipal Boundaries
Act 167 of 1978
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STORMWATER MANAGEMENT PARTNERSHIP
Counties
Municipalities
Developers
State Agencies
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Act 167 of 1978- Requirements

• Counties with the help of municipalities prepare
  Watershed Stormwater Plans
• Municipalities Implement Plans
• DEP provides Technical, Administrative and
  Financial Assistance
• Developers Implement Stormwater controls and
  BMPs

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Stormwater Plan Elements

• Watershed Hydrologic and hydraulic evaluation
  considering existing and future land use/land
  cover, soils, slopes, stream characteristics,
  floodplains, presence of water bodies, rainfall
  and water budget
• Waterway obstructions/their capacities, and
  drainage problems
• Existing/proposed stormwater collection systems
  and their impacts
• Criteria/standards for control of stormwater
  runoff

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SW Plans-Runoff Control Requirements

• Accelerated runoff from developments to protect
  immediate downstream properties and all
  downstream areas in the watershed
• Past SW Plans focused on control of rate of
  runoff- Release rate control strategy

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Release Rate Concept

• Development sites runoff Contribution at key
  locations along the receiving water bodies prior
  to development activities(sub-area hydrograph
  peak vs total hydrograph)

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Act 167 SW Planning Status

• 80 Plans approved for 44 counties
• 709 Municipalities to enact and implement
  ordinances
• 39 Additional Plans currently under way
• 13 million appropriated to date
• FY 2002 appropriation- 1.2 million

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Traditional Stormwater Management Practices

• Collect runoff from the entire development site
  to Detention Basins and release at controlled
  rate
• Basin Outflow discharged to receiving waters or
  allowed as overland flow
• SW Mgt. Practices did not consider increase of
  runoff volume, impact on stream morphology, and
  loss of infiltration, often created drainage
  problems, and disrupted natural water balance of
  the watershed!

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Rate Volume of Stormwater Runoff
Water Quality Of SW Runoff
Infiltration/ Groundwater Recharge
Implementable Municipal Ordinance
Act 167 Comprehensive SW Planning
NPDES Phase II Construction Permit
Special Protection Waters Consideration
NPDES MS4 Permit
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This diagram shows how development and its
corresponding increase in impervious cover
disrupts the natural water balance. In the
post-development setting, the amount of water
running off the site is dramatically increased.
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ACT 167 TECHNICAL OBJECTIVES    
 
 
MAINTAIN WATER QUALITY
MAINTAIN GROUNDWATER RECHARGE
PREVENT STREAMBANK EROSION
MANAGE OVERBANK FLOODING EVENTS
MANAGE EXTREME EVENTS
QUALITY VOLUME WATER
RECHARGE VOLUME
1-YR, 24 HOUR DETAINED 24 HOURS  
2, 5, 10 -YEAR EVENTS
25-, 50-, 100- YEAR EVENTS
WQv (P)(Rv) (A)/12
Rev (S)(Rv) (A)/12
Quantity Rate, Volume Controls
P Precipitation in Inches Rv 0.05
0.009(I) A Area in Acres I the impervious
surface ratio S Soil specific recharge
factor (inches)  
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Stormwater Mgt. Preferred Implementation Strategy

• Satisfy Infiltration and Water Quality Volume
  Requirements
• Satisfy Quantity Control Requirements
• Match Post-Development Hydrograph to
  pre-Development Level
• Incorporate Low Impact Development Practices
• Preserving Natural Drainage Features
• Reduce/Disconnect Impervious Areas
• Rout Roof Runoff over Lawns
• Infiltrate Runoff
• Reduce Street Widths, Building Setbacks
• Consider Cluster Development
• Promote Environmentally Friendly Development

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Stormwater Credits

• Stormwater Facility Designs, Subject to the
  Municipal Engineers Approval, May Incorporate
  the Following Credits
• Disconnection of Rooftop Runoff
• Disconnection of Non-Rooftop Runoff
• Natural Area Conservation
• Stream Buffer Credit
• Grass Channel (Open Section Roads)
• Environmentally Sensitive Rural Development

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Post-construction Stormwater Management
Act 167 stormwater plan provide a comprehensive
model ordinance. Under the Act, municipalities
are required to either implement this ordinance,
or implement the stormwater management strategy
recommended in the plan through applicable local
regulations
Permeable pavements promote recharge
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Integrating All Water Resource Issues in SW Mgt
Planning May Be a Challenge, But Needs to be
done!!

• Durla N. Lathia
• 717-772-5661
• www.dep.state.pa.us
• For All Water Related Issues, visit
• www.pa-envirohelp.org