January 29, 2015

Building Design Branch

Huntington Levee Community Meeting

Building Design Branch

Agenda

I. Project Background & Completed Tasks

II. Interior Drainage Analysis

III. Pump Station Design

IV. Construction Access

V. Schedule and Next Steps

VI. Community Outreach

VII. Questions

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Building Design Branch

• June 2006 -160 homes were flooded from a storm event

• 2009 – US Army Corps of Engineers (USACE) completed a study to evaluate flood damage reduction measures in the Huntington Community

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Project Background

Building Design Branch

• November 6, 2012 – Fairfax County voters approved stormwater bond referendum to fund design and construction of flood damage reduction measures proposed by the USACE

• June 2013 – Fairfax County awarded the levee design contract to ARCADIS

• November 2013 – ARCADIS submitted the Phase I design package to Fairfax County

• Survey, Geotechnical Investigation, Wetland Delineation, and Conceptual Design

• January 2014 – Fairfax County and Huntington Community reach consensus on conceptual design features

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Project Background

Building Design Branch

• July 2014 – ARCADIS completed Hydraulic and Hydrologic Modelling for Cameron Run

• September 2014 – ARCADIS submitted Schematic (30%) Design package to Fairfax County

• October 2014 - Fairfax County conducted Value Engineering Workshop

• December 2014 – ARCADIS began Design Development (60%) phase

• December 2014 – Geotechnical Report submitted for Permitting

• January 2015 – ARCADIS completed the Interior Drainage Analysis

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Project Background

Building Design Branch

Project Background

• Earthen Levee/I-Wall Combination

• Collection Drains

• Pump Station Location – East end of levee

• Stormwater Diversion – Concrete box culverts

Key Design Features

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Building Design Branch

Interior Drainage Analysis

Interior Levee Exterior

Note: Exterior (Cameron Run) Modeling Completed July 2014

Building Design Branch

Interior Drainage Analysis

Purpose

• Understand how water flows on land behind levee

• Understand how adding the levee will change the water flow

• Set design water elevation

• Size pumps and interior water storage area

• Provides the data necessary for the FEMA Accreditation package and revision to the Floodplain Maps.

• Support the Floodplain Study for submission to the County Land Development Services

Building Design Branch 9

Existing 100-year Water Surface Elevation

Interior Drainage Analysis

Building Design Branch

Interior Drainage Analysis

Building Design Branch

Interior Drainage Analysis

HEC-HMS Modeling Approach

Building Design Branch

Interior Drainage Analysis

HEC-HMS Results – Hypothetical EventsClosed Drainage Structures

Peak Pond Elevation based on HEC-HMS modelling

Storm Intensity Rainfall Depth (in.) Peak Pond Elevation (ft.)

2- year 3.17 5.5

5- year 4.07 6.1

10- year 4.87 6.6

25- year 6.09 7.1

50- year 7.18 7.5

100- year 8.41 8.0

500- year 12.00 9.1

Building Design Branch

Interior Drainage Analysis

Project Cross-Section Key Elevations

Building Design Branch 14

100-year stormwater ponding at elevation 8.0’

Interior Drainage Analysis

Building Design Branch

Interior Drainage Analysis

Historical Flood Events - Cameron Run – Jones Point Rainfall

Historical Event Rainfall at Jones Point Station

(Inches)

Peak Water Surface Elevation

(Feet)

July 28, 2000 1.12 4.1

September 23, 2003* 1.80 4.6

June 25, 2006 3.51 5.1

September 6, 2008 3.40 4.4

September 8, 2011** 2.64 4.5

June 10, 2013 2.30 4.6

June 28, 2013 1.59 4.4

July 12, 2013 2.46 4.8

May 16, 2014 2.68 4.5

Peak Water Surface Elevation based on HEC-HMS modelling

* Tropical Storm Isabel

** Tropical Storm Lee

Building Design Branch

Interior Drainage Analysis

Historical Flood Events - Cameron Run – Jones Point Rainfall

Peak Water Surface Elevation based on HEC-HMS modelling

Building Design Branch 17

25-year stormwater ponding

Interior Drainage Analysis

Building Design Branch 18

10-year stormwater ponding

Interior Drainage Analysis

Building Design Branch

Interior Drainage Analysis

Interior Ponding Area

• Provides location for stormwater until it can be pumped out

• Controlled flooding area

• Coordinating with Fairfax County Park Authority on design and possible amenities

• Likely not athletic fields

Building Design Branch 20

Levee impact and storage requirements

Interior Drainage Analysis

Building Design Branch 21

Pump Station

Building Design Branch 22

Pump Station

Pump Station Equipment

• 3 Active Stormwater Pumps

• 1 Backup Stormwater Pump

• 2 Dewatering Pumps

• Generator for Emergency Power

Building Design Branch 23

Preliminary Interior Rendering

Pump Station

Building Design Branch 24

Scaled Model of PumpingConfiguration

Pump Station

Building Design Branch 25

Preliminary Exterior Rendering

Pump Station

Building Design Branch 26

Preliminary Exterior Rendering

Pump Station

Building Design Branch 27

Construction and Maintenance Access

Building Design Branch

• Phase II (January 2014-Winter 2017)

• Schematic Design (30%)

• Design Development (60%)

• Permitting

• Land Acquisition

• Construction Documents (100%)

• Bidding

• Phase III (Winter 2017-Spring 2019)

• Construction

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Schedule

Schedule

Building Design Branch

• Next Steps

• Site Permit Submission – February 2015

• Pump Station Work Session – February 2015

• Design Development Submission (60%) – April 2015

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Schedule

Schedule

Building Design Branch

Schedule

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Building Design Branch

Community Outreach

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Building Design Branch

Community Outreach

• Community Meeting notes will be placed on the web site 2 weeks after the meeting

• Quarterly emails sent out to the project listserv with progress made in the past three months and what to expect in the next three months

• Schedule – added a feature to the web site to help the Community track the progress of the active components of the project.

Communication

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Building Design Branch

Community Outreach

• Bi-annually

• Important Milestones

• Next Community meeting – July 2015

• Updates on Permitting

• Interior Ponding Development

• Pump Station

Community Meetings

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Building Design Branch

Questions

Contact Information – Huntington Levee Project Phone #: 703-324-5800

Email address: HuntingtonLevee@fairfaxcounty.gov

Contact Information – Stormwater Questions Phone #: 703-324-5821

Email address: SWPDmail@fairfaxcounty.gov

Huntington Levee Website: www.fairfaxcounty.gov/dpwes/huntingtonlevee

To request this document in an alternate format call 703-324-5800, TTY 711.

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