bringing science to stormwater implementation · 2020-06-12 · herbert, rowland & grubic, inc....
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Bringing Science to Stormwater
Implementation
www.PaSTW.org
•Discuss the Need for a New Manual
VUSP October 17, 2013
A Public/Private Partnership with PADEP formed to update the
Pennsylvania Best Management Practices Manual
•Independent workgroup •Began in 2009 at PADEP Southcentral •To strengthen the Pa BMP Manual •145 +/- engineers, scientists, academics •PADEP & Conservation Districts members •Some conservation groups
Sub-Committees •Integrating Stormwater Management into the Site Design Process •Stormwater Management Standards •Non-structural / LID Practices •Runoff Volume Reduction - Vegetated •Runoff Volume Reduction - Stored Infiltration •Peak Reduction BMPs •Capture and Reuse
Sub-Committees •Runoff Water Quality Treatment •Special Management Areas •Redevelopment •Stormwater Calculations and Methodologies •Soils and Infiltration •Maintenance and Operations •Case Studies
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Robert Traver, PhD, PE, D.WRE Michele Adams, PhD, PE Mark Bowen, PE, CFM Bud Newton, ME, PE, PLS, CPSWQ Frank Browne, PhD, PE Russ Losco, MA, PG, CPSS Gary Kribbs, PG Jeff MacKay, MS, PG, CPESC Al Brulo, PE Keith Lieberman MS, PE Tom Gillespie, PG Katie Blansett, PhD, PE Shirley Clark, PhD, PE Paul DeBarry, PE, PH, GISP, D.WRE
Team Leader email
Incorporate Science • Use research to update Manual. • Cross-reference new data and information emerging in the industry. • Make specific recommendations for scientific research. • Better utilize existing technology and scientific knowledge. • Provide a system for peer review of recommendations. • Provide experts to help with design and review.
•Proposing an alternative LID Control Guidance •Adopted an alternative design calculation method •Adopted a reorganization of the manual
•Includes chapters on site design process & LID •Some appendices competed
Manual will Include appendices on Inf., ET, Water Balance, Training, Funding, Perpetual Maintenance
•Regrouped BMPs – combined structural and non •Developing a BMP matrix •Adopted a standard format for BMPs
•Includes technical specs., inspection, long-term issues
Green Infrastructure Volume CG 1) Undisturbed natural and restored compacted areas (BMP6.7.3)
are not included in water quality or volume requirements. 2) Runoff from all impervious and non restored pervious areas
shall be treated by / routed through Green Infrastructure (GI) stormwater control measures (SCM’s). GI is defined as SCM’s that address both volume and quality that are
selected and designed to treat pollutants of concern. Detention systems are allowed as part of a treatment train that
includes water quality / volume reduction SCMs SCMs are to be designed to safely bypass flows that exceed the design
capacity. 3) The Runoff volume from the EISA (2009) rain event will be
captured and removed through reuse, infiltration, ET, or slow release. Runoff from impervious and unrestored areas are included in the small storm capture area.
Green Infrastructure Volume CG 4)The small storm capture volume routed through Green
Infrastructure SCM’s may be managed through capture and reuse, infiltration, and through ET and slow release systems. For GI Vegetated / Soil SCM’S designed for slow release and ET
ET volume can be credited when designed in accordance with BMP XXXX
Slow Release can be credited when designed in accordance with BMP XXXX\
5). Flow rates generated by impervious surfaces for the 2 year 24 hour storm will not exceed the predevelopment condition. For waters identified as having an impairment caused by “Water Flow
Variability,” the peak flow rate for the 2 year 24 hour storm event shall be reduced to 50 percent of the pre-development value.
Proposed Chapter 4: Integrating Stormwater Management
into the Site Design Process
• Pre-application meeting with design engineer, district and
municipality • Improve communications between developer and review agencies • Improve integration of design process between Conservation District
and Municipality • Improved flow chart for more efficient/economical site design &
approval process • Improved checklist for pre-application meeting
Chair: Keith Lieberman
Proposed Chapter 5: LID Approach to Stormwater Management Design
Totally new chapter resulting from the consolidation of chapters on structure & non-structural BMPs (original Chapters 5 & 6)
Purpose of proposed Ch 5 is to incentivize Low Impact Development and tie the process of stormwater design to the site evaluation process
Chair: Paul DeBarry & Katie Blansett
• Subgroup has been meeting monthly since inception • Early draft distributed in early 2011 to other subgroups for peer-
review • New Draft Appendix A has been complete for approx. 1 year • Draft meets the goals as stated • Available on the share point for final peer-review
• Infiltration Subgroup is now engaged in:
• Writing the standards for the Infiltration BMP’s • Writing section 5.2 “Site Evaluation for Stormwater Management” • Adding to the Glossary • Intent is to finalize these within the next 30-60 days and upload to
the share point
Infiltration Subgroup
Progress: • Expanded scope of work to include all special management areas
(subgroup previously only addressed linear projects) • Revised outline to include new special management areas and expand
on current topics • Added new members to assist with additional workload • Subgroup is now engaged in:
• Drafting revised Ch. 7 for review by entire group • Adding to the Glossary • Intent is to finish draft in next 60 days
Special Management Areas Subgroup
Chair: Gary Kribbs Looking for new members Create a matrix of options that encourages the redevelopment
Encouraged to limit green field development Make up for past sins 20% meadow
Addressing issues with contaminated sites before/during construction
Brownfields are often high density retail, office or other Use density incentives How do we factor in special protection or impaired?
Big Box Retail is common in redevelopment
High percentages of impervious cover Volume control opportunities is limited Allow off-site wetland mitigation
Redevelopment
Chair: Bud Newton
Spray Irrigation Tried and Proven Gray water reuse
Runoff Volume Reduction – Rainwater Harvesting
1. Develop design standards to facilitate easy inspection, operation and maintenance of BMPs.
2. Determine existing triggers and who they make responsible for inspection, operation and maintenance of BMPs. Then, make recommendations to eliminate redundancy, eliminate holes and fund inspection/administration costs. Some triggers include:
3. Develop standards for inspection, operation and maintenance of BMPs. Include instructions/checklist, schedule and template agreement.
4. Determine methods of improvement/maintenance guarantees to
insure proper construction, operation and maintenance.
5. Determine how to handle failed BMPs.
Goals Inspection, Operation & Maintenance
1. Manage Runoff Volume from Disturbed Site Using 95% rainfall event (no surface discharge)
Small Storm Hydrology and Rv Values Runoff coefficient using rainfall depth and land use
Rv x Area x Rainfall depth
Rv varies by urban land use and rainfall depth
Alternate Calculation Approach
What does 95th Percentile mean in Pennsylvania?
• Based on rainfall event analysis (6-hour separation) • Data courtesy Dr. Shirley Clark and Ruth Sitler
2. Provide Peak Rate credit for volume management Adjust Curve Number using CWP “Runoff Reduction Method”
Q –R = (P – 0.2S)2 (P + 0.8S) Where R = retention storage provided by runoff reduction practices Need Guidelines to adjust Tc for LID
Suggested Alternate Calculation Approach
• Several BMPs in various stages of writing • Bioretention • Bioswales • Floodplain Restoration • Re-vegetation of Disturbed Areas • Landscape Restoration • Riparian Buffer • Evapotranspiration Wetlands
• Appendix C • Evapotranspiration and Water Balance
Chair: Mark Bowen
Runoff Volume Reduction - Vegetated
– Evaluate surrogate parameters (TSS, N, P) – are others needed to reflect real conditions?
– Consider eliminating percent removals for BMPs and replace with effluent concentration criteria for surrogate parameters
– Develop engineering design criteria for BMPs – Revise water quality work sheets – Recommend water quality storm – Recommend approach/criteria for selecting/using
manufactured products – Develop guidance for BMPs in series
Chair: Frank Browne
Runoff Water Quality Treatment
BMP Type TSS (mg/L) Median (95% Conference Interval) Grass Strip 19.1 (16.0 - 21.5) Bioretention 8.3 (5.0 - 9.0) Bioswale 13.6 (11.8 - 15.3) Composite 17.4 (12.4 -18.8) Detention Basin 24.2 (19.0 - 26.0) Green Roof 2.9 (1.0 - 3.5) Manufactured Device 18.4 (15.0 - 19.9) Media Filter 8.7 (7.4 - 10.0) Porous Pavement 13.2 (11.0 - 14.4) Retention Pond 13.5 (12.0 - 15.0) Wetland Basin 9.06 (7.0 - 10.9) Wetland Channel 14.3 (10.0 - 16.0)
Irreducible TSS Effluent Concentrations (Source: International BMP Database)
Newton Engineering Meliora Design Group
F. X. Browne, Inc. Herbert, Rowland & Grubic, Inc.
Pennsylvania State University T&M Associates
NTM Engineering The Mitman Group LLC
Lanchester Soil Consultants, Inc. PA Department of Environmental Protection
AEON Geoscience, Inc. Villanova University Gilmore Associates
Kleinschmidt PA Housing Research Center
Bringing Science to Stormwater Implementation
Three easy Steps to Apply: 1. Choose a Sub-Committee 2. Email a Team Leader 3. Provide a Resume
APPLY NOW
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www.PaSTW.org