coalition for the delaware river watershed presents: 2nd annual delaware river watershed forum
TRANSCRIPT
Coalition for the Delaware River presents:
2nd Annual Delaware River Watershed Forum
Geoff Reese, PE
Travis Bartholomew, PE
October 22, 2014
Hotel Bethlehem
Act 167 Overview
• Pennsylvania Stormwater Management Act of 1978
• Major Components• Places responsibility on counties to prepare watershed plans.• Outlines 13 plan requirements.• Authorizes DEP to prepare guidelines to assist counties.• Authorizes DEP to designate watersheds.• Authorizes grant program to reimburse counties.• Places responsibilities on land developers.
• Purposes• Encourage the sound planning and management of storm runoff.• Coordinate the storm runoff management efforts within each
watershed.• Encourage the local administration and management of storm
runoff.
1. Survey of existing runoff characteristics
2. Survey of obstructions3. Assessment of projected
land development
4. Analysis of Flood Hazard Area development
5. Survey of existing drainage problems
6. Survey of existing and proposed storm sewers
7. Assessment of alternative runoff controls
13 Plan Requirements
13 Plan Requirements
8. Identification of future flood control projects
9. Designation of future storm sewer areas
10.Identification of floodplains
11.Development of runoff control criteria
12.Development of implementation priorities
13.Development of plan review/revision process
Prior Land Developments
• Act 167 does not attempt to regulate past development
• Plan requirements only apply to land developments proposed since the adoption date of the plan
• Focused on preserving “status quo” - the state of the watershed at time of plan development
Act 167 Responsibilities
• County Responsibilities• Develop an Act 167 Plan for
each watershed within its boundaries.
• Consult with municipalities through the Watershed Plan Advisory Committee.
• Adopt the plan by resolution after holding a public hearing and making the appropriate changes.
• Submit adopted plan to DEP.
• Lehigh and Northampton counties have delegated plan preparation to the LVPC
Act 167 Responsibilities
• Municipal Responsibilities• Participate in the plan
development through the Watershed Plan Advisory Committee.
• Review the draft plan and provide comments.
• Adopt the necessary ordinances to control storm runoff after the plan is approved by DEP.
• Implement the plan through the enforcement of the new stormwater ordinance.
Act 167 Modeling
• The LVPC creates hydrologic models to test proposed control strategies against existing stream flows
• Model input data and sources include:• Geology and soils data – Existing mapping
• Existing land use data – GIS and field data
• Future land use data – Current zoning
• Stream channel geometry – Aerial photography and field data
• LVPC also collects data on existing drainage problems• Obstruction documentation – Field data
• Existing problem area documentation – Municipal questionnaire
Geology for Lehigh and Northampton Counties
Saucon Creek Watershed
Existing Land Use
Saucon Creek Watershed
Future Land Use
Release Rate Development
• Release Rates control runoff based on its impact on the flood peak
• Expressed as a percentage of the existing runoff that can be discharged after development
• Ranges from 30% to 100%
• Goal to allow development, but not increase peak flow at any point in the watershed
Saucon Creek Release Rates
Water Quality
• In general:• Quantity control =
manage large events• Quality control = manage
small events
• Pre-2004 Act 167 Plans controls only addressed water quantity
• Peak rate control• Severe flooding
• New plans must also address water quality
• Channel erosion• Nutrient loading• Temperature control
Return Periods
•Return periods describe the rarity/magnitude of large rainfall events
•2-year event is approximately a “bankfull” event
•100-year is usually the largest controlled
Return
Period
Annual %
Exceedance
2-year 50%
10-year 10%
25-year 4%
100-year 1%
Water Quality• Since 2004, new plans have
incorporated elements of NPDES and MS4 programs
• Requiring runoff treatment with Best Management Practices (BMPs)
• Promoting runoff volume reduction (infiltration and capture/reuse)
• Indirectly promoting Low Impact Development (LID) practices
• Most recent Act 167 ordinances attempt to maintain the natural “water balance”
• Post-development runoff, infiltration, and evapotranspiration should match pre-development
• DEP standard is no increase in 2 year volume pre- to post-development
LVPC Review Function
• LVPC review provides evaluation of watershed-level impacts
• Provides consistent review process independent of municipal boundaries
• LVPC interaction in the review process provides first-hand feedback for strengths and weaknesses of the ordinance
• Feeds into development of new plans and plan updates
Ordinance Cycle
Create and
adopt
ordinance for
new plan
Implement ordinance through
engineering reviews
Special Studies
- CN & Rational “c”
- Erosion issues
- Minimum orifice
- Water quality
