Balancing Wetland Protection with Stormwater Management - a Case Study

Balancing Wetland Regulation
with Stormwater Management:
A Case Study.
Mid-Atlantic Wetlands - CLE International
November 7, 2008, Baltimore, MD

Andrew T. Der
Associate and Director of Environmental Sciences
Loiederman Soltesz Associates, Inc.

2 Research Place
Rockville, MD 20850

Telephone 301 948 2750
Email ader@LSAssociates.net
Web site www.LSAssociates.net

Current Issues in Stormwater Regulation in Maryland | April 22, 2005

Effects of Stormwater

• Hydrology

• Geomorphology

• Habitat

• Water Quality


What Happens

Runoff from
1” Rain Event


Hydrology

• Increase in flow and
velocities

• Increase in flooding

• Increase in frequency

• Increase in bankfull flows


Geomorphology

• Stream Widening

• Channel Instability

• Erosion


Habitat

• Fish Barriers

• Loss of Substrate

• Loss of Riparian Zone

• Loss of Micro-topography


Water Quality
• Sediments
- Channel erosion can be the
primary sediment source!

• Nutrients
- Maintained vegetated areas

• Temperature
- Warm pavements and
pond pools

• Other
- Oils, Greases, heavy metals, toxics


Instability


Water Resource Regulatory
Processes Applicable to
Development
Streams and Wetlands
• Nontidal Wetlands: Jurisdictional Areas per 1987 Corps Manual and 25'
Buffer

• Tidal Wetlands: Tidally Influenced Open (navigable) Water and Their
Wetlands

• Streams: Activities Which Alter Flow, Current or Cross-section of
Streams & 100 Year Floodplain

• §404 Corps Nontidal and Tidal Waters: All waters, no Floodplain

• §401 State Water Quality Certification


Water Resource Regulatory
Processes Applicable to
Development
Stormwater
• NPDES Phase I and II

• Most construction permitted under NPDES State GP

• Stormwater Management Regulations – determined by State and
locality – New Maryland 2007 Stormwater Managemetn Act

• Erosion and Sediment Control Regulations

• Coastal Zone Management Act

• Chesapeake Bay Critical Area Law

• Special County requirements


Classification of
Maryland’s Waters

• Use I & I-P: Water Contact Recreation and
Protection of Aquatic Life

• Use II: Shellfish Harvesting Waters

• Use III & III-P: Natural Trout Waters

• Use IV & IV-P: Recreational Trout Waters


Maryland’s Water Quality
Standards
• Numerical: Dissolved Oxygen, Temperature, pH,
Turbidity, Fecal Coliform, Toxics

• Narrative: ...Protection of Aquatic Life ...Fishable
...Swimmable...Includes EPA Anti-Degradation Policy:
“...To accomplish the objective of maintaining
existing water quality...Nonpoint sources shall
achieve all cost effective and reasonable best
management practices for nonpoint source
control...”


What is a Best Management
Practice (BMP)?
• Early Planning

• Low Impact Development
– “LID-like” or Better Site Design

• Impervious limitations

• Sheet flow management – open section pavement

• Local stream buffers and setbacks

• Devices
Most significant factor affecting performance is
construction and maintenance


Common Engineered
Practices
Smaller Volumes Larger Volumes
Most compatible with ESD When preferred is
goals of 2007 SWM Act – Insufficient
Central Locations
At Source & Pretreatment
For Quantity and Quality
Quality Control Only Control
• Infiltration • Stormwater Ponds
– trench/basin – wet pond
– wet ED pond
• Filtering – dry ED pond (for cold
– sand filter/bioretention water w/ pre-treatment
– multiple pond system
• Hydrodynamic Devices
• Stormwater Wetlands
– shallow marsh
• “New” Technology – ED shallow wetland
– pervious surfaces/green – pond/wetland system
roofs

Montgomery County


Piney Branch Watershed


Initial “Template” Development
at Lowest Point


Initial Wetland and
Water Quality Issues

• Purpose and Need

• Avoidance/Minimization

• Roads, Utilities, Embankments

• SWM: Quality

• SWM: Quantity

• Coordinate with County

• ADP and Instream SWM


Need to Investigate
Hierarchy of SWM Preferences

• Infiltration Trenches and Depressions

• Bioretention, Swales, Sandfilters, Filtering
Marsh

• Extended Detention (with Wetland Bottom)

• Retention (with Wetland and Forebays)


Watershed Mitigation and
BMP’s
• Wetland/stream impacts limited to roads/utilities

• In-stream SWM in marginal/poor areas

• Minimum stream buffer of 100‘

• Wetland mitigation in riparian buffer areas

• “First flush” SWM in uplands

• Infiltration/filtration where feasible

• Quantity management in “horseshoe” ponds

• Pooling areas planted with wetland vegetation


The Best BMP
Work with Forest and Wetland Conservation


Work with Site
Character


BMP’s and Mitigation


Sensitive Resources


SWM & Amenity
Not Incompatible


Transition Habitat


Bioretention
Infiltration


Landscaped Bioretention
Facility


Hydrodynamic Devices


Stream Stabilization
• Can be effective watershed sediment control practice
• Can be local approval requirement
• Can be a traded credit
• Can be out-of-kind wetland mitigation


Get Creative


Public Involvement

• Public Notice

• Use III or IV Potential

• Temperature and Ponds

• ADP

• RBA

• No Use III or IV standards but higher quality Use I


Additional Watershed
Management Practices
• Water Quality Monitoring Plan

• Stream Reach Temperature Model and Percent
Contribution of QED, 2, 10 to Stream Flow

• Maximum 20% Diversion Base Flow

• Shade Planting of SW Conveyance and Management
Areas

• Toe Drain Pipes Under Embankment Fill


Monitoring
Used also for MS4 Compliance

Can be State requirement

Preconstruction, construction
and post-construction

Macroinvertebrate Studies
(more common examples are
WWTP & mining requirements)

Chemistry

Geomorphology

Groundwater


Monitoring


Bioassessment
Rapid Bioassessment Metric Comparisons to Pre-Construction Scores
Year ST2 ST6 ST10
1993 Non Impaired ** Non Impaired **
1994 Non to Mod. Impaired Non Impaired Non Impaired **
1995 Non to Mod. Impaired Non to Mod. Impaired Non Impaired
1996 Non to Mod. Impaired Moderately Impaired Non to Mod. Impaired
1997 Non to Mod. Impaired Non to Mod. Impaired Moderately Impaired
1998 Moderately Impaired Non to Mod. Impaired
1999 Moderately Impaired Moderately Impaired Moderately Impaired
2000 Moderately Impaired Non to Mod. Impaired
2001 Non to Severely Impaired Moderately Impaired Non Impaired
2002 Non to Mod. Impaired Mod. to Severely Impaired
** Non Impaired value is given to the first (reference) date for comparison purposes;
the streams on those dates are not necessarily truly non-impaired.


Dissolved Oxygen
Piney Branch Mean Dissolved Oxygen Levels for Stations 2, 6 and 10

ST. 2 Mean D.O. ST. 6 Mean D.O. ST. 10 Mean D.O. Use I Min. D.O.

14

12

10

8
mg/l

6

4

2

0
1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
Year


Temperature
Piney Branch Instream Peak Tem pe ratures
Stations 2, 6 and 10

ST. 2 ST. 6 ST. 10

35

30

25
Temperature (oC)

20

15

10

5

0
1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
Year


State/County Watershed
Initiatives

• Biological Monitoring Workgroup

• County Special Protection Area Legislation

• Biosensitive Stream Crossing Committee

• Interagency Wetlands Coordinating Committee

• Findings input to Municipal NPDES Compliance


Balancing Wetland Protection with Stormwater Management - a Case Study

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