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Consultants, Builders and Developers Informational Meeting Stormwater Design Requirements Monday, December 4, 2017 9:00 AM – 11:00 AM Public Utilities Operations Multipurpose Rooms 3500 Dam Neck Road Virginia Beach, VA 23453

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Page 1: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

Consultants, Builders and Developers Informational Meeting

Stormwater Design Requirements

Monday, December 4, 20179:00 AM – 11:00 AM

Public Utilities Operations Multipurpose Rooms3500 Dam Neck Road

Virginia Beach, VA 23453

Page 2: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

December 5, 2017 Consultants, Builders and Developers Meeting 2

MEETING AGENDA

1. Welcome, Introduction of Speakers and Facilitator, Meeting Agenda – J. Barry Frankenfield, Director

2. Introduction of the Public Works Stormwater Engineering Center – Toni Alger, P.E., SWEC Administrator

3. Public Works Stormwater and Sea Level Rise Update – C. J. Bodnar, P.E. and Greg Johnson, P.E.

4. Preliminary Stormwater Analysis; Projects needing City Council Approval – Seth Edwards, P.E., DSC Engineering Supervisor

5. FINAL Stormwater Engineering Submittal/Review – Seth Edwards, P.E., DSC Engineering Supervisor

6. Final Stormwater DESIGN COMPONENTS – Seth Edwards, P.E., DSC Engineering Supervisor

7. Questions and Answers, Comments and Suggestions Session – Bob Trahan, Facilitator, STIR Office

8. Closing Remarks - J. Barry Frankenfield, Director

Page 3: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

3 | Stormwater Design December 4, 2017

Stormwater Engineering Center

December 4, 2017

Toni Alger, P.E.C.J. Bodnar, P.E.Greg Johnson, P.E.

Page 4: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

4 | Stormwater Design December 4, 2017

Areas of Known Flooding

• Windsor Woods• Shore Drive• The Lakes• Sherwood Lakes• Princess Ann Plaza• Northgate• Ashville Park • Central Resort Area

• College Park• Level Green• Oceana Village• Lamplight Manor• Green Run• Lake Chubb/Bradford• Aragona

The City has a long and likely growing list of areas of known flooding. Public and private projects in those areas will have to consider the existing and future conditions.

Many are attributable to rising sea levels and increasing rainfalls.

Page 5: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

5 | Stormwater Design December 4, 2017

Stormwater Master Planning

Current Master Plans date from the late 1980s to early 1990s

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Page 6: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

6 | Stormwater Design December 4, 2017

Stormwater Master Plan – Why update?• Update stormwater system inventory• Create computer models of the

current stormwater system utilizing readily available software

• Assess performance of stormwater system– Flood control– Stormwater quality

• Identify deficiencies in the stormwater system

• Determine needed improvements• Provide information for project

designs• Create Comprehensive Stormwater

Management Plans where possible

Page 7: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

7 | Stormwater Design December 4, 2017

Comparison of Previous to Current

Page 8: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

8 | Stormwater Design December 4, 2017

GIS Mapping

Page 9: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

9 | Stormwater Design December 4, 2017

Comprehensive Master Plan Integration of multiple stormwater issues

• Stormwater management and flood mitigation

• 31 Watersheds • Stormwater quality

– TMDLs (TN, TP, TSS, bacteria)

• Regulatory compliance– NPDES MS4, TMDLs– System Inventory

• Sea level rise and tidal surge

• Capital improvement planning and funding

• Design Information for Projects

Page 10: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

10 | Stormwater Design December 4, 2017

Hydrologic & Hydraulic Parameters• Impervious cover

• Soil type / Land use

• Depth to groundwater

• Rainfall depth and distribution

• Boundary conditions

• Catchment geometry

• Inventory of System characteristics

• Boundary Conditions (tailwater)

Page 11: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

11 | Stormwater Design December 4, 2017

Sea Level Rise• City is developing a

Comprehensive Response Plan to Sea Level Rise

• City’s Plan is utilizing projected increases in sea level per the VIMS 2013 report to the General Assembly

• Among its many impacts, sea level rise will obviously impact drainage system performance in many, if not most areas of the City.

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Page 12: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

12 | Stormwater Design December 4, 201712 | Stormwater Design December 4, 2017

3 ft1.5 ft

Evaluate for Adaptive Capacity

Action

Selected Scenarios vs Federal Curves

Life Cycle Alignment Time Horizon/Time Period SLR Value Relevance Use

Municipal Planning 20-40 years

2035-20551.5 ft

Comprehensive Plan & Outcomes

Short end of Commercial and Utility life-cycles

Vulnerability assessment

Key planning value

Basis for evaluation of all adaptation strategies

Critical Infrastructure

Long-term awareness

Adaptive Capacity

50-70 years

2065-2085

3.0 ft

Utility Infrastructure life-cycle

Transportation infrastructure lifecycles

Residential structure lifecycles

Secondary vulnerability assessment to provide insight into long-term risk

Basis for long-term infrastructure decisions

Evaluate cost-effectiveness of additional protection for adaptable resilience strategies

Page 13: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

13 | Stormwater Design December 4, 201713 | Stormwater Design December 4, 2017

Projected Changes in Coastal Flooding

• Areas subject to flooding will increase:

• In 30-40 years: 1.5 times present area

• In 60-70 years: 2 times present area

Page 14: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

14 | Stormwater Design December 4, 201714 | Stormwater Design December 4, 2017

Combined Impact on Stormwater Analysis• Higher coastal water levels diminish stormwater system performance

• Stormwater Conveyance

• Combined Flooding

• Coastal Flooding

Page 15: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

15 | Stormwater Design December 4, 201715 | Stormwater Design December 4, 2017

Changes in Rainfall• Regional Precipitation Trends

• Heavy rainfall increasing

• Future precipitation conditions• Up to 20% increase in design rain

Page 16: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

16 | Stormwater Design December 4, 2017

Pending Updates to City Stormwater Standards

• Clarify and Consolidate in one place – easier to understand and locate

• Incorporating changes in rainfall intensities

• Adapting to sea level rise-ongoing work

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Page 17: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

17 | Stormwater Design December 4, 201717 | Stormwater Design December 4, 2017

Creating Comprehensive Stormwater Management Plans“Comprehensive stormwater management plan” means a plan, whichmay be integrated with other land use plans or regulations, that specifieshow the water quality components, quantity components, or both ofstormwater are to be managed on the basis of an entire watershed or aportion thereof. The plan may also provide the remediation of erosion,flooding, and water quality and quantity problems caused by priordevelopment. – VAC Chapter 60

Must be approved by DEQ

• Allows stormwater control measures on a watershed basis• Potential to reduce specific VSMP on-site requirements for public and

private project in an area covered by a comprehensive stormwater management plan (CSWMP)

• Individual project will still need to demonstrate that the project’s stormwater design work in the context of the CSWMP and that other requirement of VSMP and proper drainage are satisfied.

Page 18: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

18 | Stormwater Design December 4, 2017

DEQ Energy Balance Equation/CSMP

.....Reviewing the submittal as a CSMP, DEQ recognizes the use of SWMM is a valid tool to demonstrate channel and flood protection in accordance with the objectives of the VSMP regulations….

The City’s model appears to be a holistic hydraulic approach that integrates increase discharges from an individual project into the Cities stormwater network during wet weather flows and during tidal fluctuations.

The City’s model integrates the incremental difference between pre and post- developmental flows that enter into the stormwater network system during storm events, i.e. wet weather conditions.

Page 19: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

19 | Stormwater Design December 4, 2017

Important References

“The Designer must recognize that individual site development plans or a retrofits of drainage facilities in urban areas may be only a part of a larger system and that he must integrate his design into a larger system , particularly with respect to creating upstream and downstream hazards.”

Page 20: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

20 | Stormwater Design December 4, 2017

Final Thought - Plan to fail“Somehow we have to find the middle ground between dangerous rigidity and catastrophic collapse. In our organizations, social and political systems, and individual lives, we need to create the possibility for what computer programmers and disaster planners call “graceful” failure.When a system fails gracefully, damage is limited, and options for recovery are preserved. Also, the part of the system that has been damaged recovers by drawing resources and information from undamaged parts.”

Thomas Homer-Dixon

The Upside of Down

Page 21: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

21 | Stormwater Design December 4, 2017

In Summary….. Credits to Yogi Berra

“You can observe a lot by watching.”“If you don’t know where you are going, you might wind up someplace else.”“It’s deja vu all over again.”“It ain’t over till it’s over.”

Page 22: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

December 5, 2017 Consultants, Builders and Developers Meeting 22

Planning and Community Development/Development Services CenterStormwater Review

Preliminary Stormwater Engineering Analysis FAQs(Handout page 2)

1. When is this needed? 2. Why is it needed?3. What information is needed? 4. Is this required or just recommended?5. What is the Submittal/Review Process? 6. Why are two engineering teams reviewing the preliminary analysis?

Page 23: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

December 5, 2017 Consultants, Builders and Developers Meeting 23

FINAL Stormwater Management Plan Submittal and Review FAQs(Handout page 5)

1. When is a Stormwater Management Plan required?2. When is an Erosion & Sediment Control Plan and MS 19 compliance (downstream capacity and

erosion) required?3. Who reviews the stormwater management plan and supporting calculations, reports, maps,

etc.? 4. Who has the existing drainage system and watershed information needed for design?5. What does each Department review?6. How long does the review take?7. Who do I contact if I disagree with the stormwater comments, have questions, or want to

meet?8. Who approves the final stormwater management plan?9. When is a Stormwater Management Facilities Maintenance Agreement (SWMA) required?

Page 24: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

December 5, 2017 Consultants, Builders and Developers Meeting 24

Final Stormwater DESIGN COMPONENTS(Handout page 7)

• Erosion and Sediment Control - Minimum Standard 19

• Minimum Technical Criteria:

Grandfathered (IIC Design Criteria) Non Grandfathered (IIB Design Criteria)

• City Design Requirements for All Projects

Page 25: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

December 5, 2017 Consultants, Builders and Developers Meeting 25

Erosion and Sediment Control - Minimum Standard 19(from 9VAC25-840)(Handout page 7)

19. Properties and waterways downstream from development sites shall be protected from sediment deposition, erosion and damage due to increases in volume, velocity and peak flow rate of stormwater runoff for the stated frequency storm of 24-hour duration in accordance with the following standards and criteria. Stream restoration and relocation projects that incorporate natural channel design concepts are not man-made channels and shall be exempt from any flow rate capacity and velocity requirements for natural or man-made channels

Page 26: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

December 5, 2017 Consultants, Builders and Developers Meeting 26

Stormwater Management Ordinance - City Code, Appendix D(Handout page 9)

“Grandfathered” Projects

May use Part II C technical criteria (may also use Part IIB technical critieria)

Water Quality -Performance Based Criteria (old calculation forms - 4 “situations”)

Water Quantity – stream channel erosion and flooding

Page 27: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

December 5, 2017 Consultants, Builders and Developers Meeting 27

NON- “Grandfathered” Projects (Handout page 10)

• Any project not meeting the “grandfathering” conditions must use Part II B technical criteria

Water Quality – VRRM spreadsheet

Water Quantity - Channel Protection

Water Quantity - Flood Protection

Page 28: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

December 5, 2017 Consultants, Builders and Developers Meeting 28

City Design Requirements/Considerations for all Projects(Handout page 12)

Tailwater

Design methods

100-year 24-hour storm event

Site Conditions Input Data

Various other local design requirements

What is included in a typical SW Design submittal?

Page 29: Informational Meeting Stormwater Design Requirements · 04/12/2017  · 3500 Dam Neck Road . Virginia Beach, VA 23453. December 5, 2017 Consultants, Builders and Developers Meeting

December 5, 2017 Consultants, Builders and Developers Meeting 29

Experiences and Suggestions

We are listening to you!