senior engineer water resourcesstormwatersymposium.org/sites/default/files/pdfs/6.3_north...

Jadene Torrent Stensland, PE Senior Water Resources Engineer

North Bethany Area

Storm Implementation Plan

Jadene Torrent Stensland, PE

Senior Engineer

Water Resources

OBJECTIVES

• BACKGROUND

• HISTORY

• DRAINAGE MASTER PLAN

• IMPLEMENTATION PLAN

• DESIGNS

• LIDA REDUCTIONS

• COST ESTIMATES

BACKGROUND

• Clean Water Services

Washington County Special Service District

Over 40 years of service

Urban Sanitary and Stormwater Management

Natural Resource Management

Serve population 527,000+ residents

BACKGROUND

• North Bethany Sub Area

Planning began over 10 years ago

800 acres, rural and ag

458 developable acres

3650 – 4750 new dwelling units

Area of Distinction

Sustainability

Parks and Trails

Utilities Planning

North Bethany Area Map

History

• Drainage Master Plan

Complete in December 2010

Concept Planning Document

Design Criteria

Storm System concept layout

Preliminary Cost Estimates

Linear Storm Water System and Trails

Otak 2010 DMP

Greenworks 2009 Sketch

Implementation Plan

• North Bethany Implementation Plan

Regional Facilities

Major Conveyance System

30% Designs

Cost Estimates

Regional Facility Sizing

Facility Concepts 1. Conventional Extended Dry Basin (round design)

2. Linear Extended Dry Basin (cascade design)

3. Implementation Options for Upstream LIDA

Conventional Extended Dry Basin

Regional Stormwater Facility Design Criteria

Design Criteria* District

Maximum Depth 4.0 feet

Maximum Ponding Depth 3.0 feet

Freeboard 1.0 feet

Amended Soils 1.0 feet

Side Slopes (in treatment area) (H:V) 3:1

Overflow (Y/N) Y

Native Plantings Y

Fencing Y

* Locate facilities outside of the

stream and vegetated corridor

(vc).

Extended Dry Basin

Facility Design Alternatives

Conventional Extended Dry Basin

Linear Extended Dry Basin

Regional Stormwater Facility Design Criteria

Design Criteria Value

Maximum Depth 4.0 feet

Maximum Ponding Depth 3.0 feet

Freeboard 1.0 feet

Amended Soils 1.0 feet

Minimum Bottom Width 8 feet

Side Slopes (in treatment area) (H:V) 3:1

Bottom Slope 0.5%

Overflow (Y/N) Y

Native Plantings Y

Fencing Y

Cascade Storm Water System

Otak 2010 DMP

Greenworks 2009 Sketch

Facility Design Alternatives

Linear Extended Dry Basin Example (cascade)

Facility Design Alternatives

Linear Extended Dry Basin Example (cascade)

3. Credit for Upstream LIDA

Areas Where Site LIDA is Required

3. Credit for Upstream LIDA

Assumptions for LIDA

3. Credit for Upstream LIDA

Impact to Regional Facility Size

2

0

10000 15000 20000 25000 30000 35000 40000

7. LIDA Planter with Orifice to Meet Hydromod Stds. (100% LIDA)

6. LIDA Planter Current Requirements (100% LIDA)

5. LIDA Planter with Orifice to Meet Hydromod Stds. (Mandatory LIDAAreas Only)

4. LIDA Planter With Deeper Growing Medium (Mandatory LIDAAreas Only)

3. LIDA Planter Current Requirements (Mandatory LIDA Areas Only)

2. LIDA Swale (Mandatory LIDA Areas Only)

1. Regional Facility Only (No LIDA)

Regional Facility Surface Area (sq-ft)

3. Credit for Upstream LIDA

Regional Facility Sizing Reduction Factors

2

1

Round Extended Detention Facility

Subbasin

Impervious Area Treated

by Mandatory LIDA

(acres) Facility Size (ft2)

Facility Area

Reduction/Impervious Acre

Treated by LIDA (ft2)

BT3

0 20,146

582 7.0 16,074

BT2 and BT3

0 45,705

554 11.0 39,611

Linear Detention Facility

Subbasin

Impervious Area Treated

by Mandatory LIDA

(acres) Facility Size (ft2)

Facility Area

Reduction/Impervious Acre

Treated by LIDA (ft2)

BT3

0 28,758

423 7 25,800

BT4

0 4,816

406 3.4 3,440

Facility

ID

Subbasin

name

Total

contributing

area,

acres

Impervious

area,

acres

RSF top area

at 4-foot

depth,

sq ft

RSF top area

50% Implementation of

LIDA

sq ft

RSF top area

100% Implementation of

LIDA

sq ft

1 AB1 34.7 18.4 33,024 30,261 27,499

2 AB2 32.0 17.8 19,772 16,265 12,759

3 AB4 42.1 21.0 25,613 21,441 17,268

4 AB6 29.9 14.3 25,800 23,965 22,130

5 AB8 33.3 22.4 15,612 13,690 11,767

6 AB9 59.8 40.1 22,708 18,932 15,155

7 AB10 19.4 10.2 15,480 13,692 11,905

8 AB11 33.7 16.8 33,540 30,352 27,164

9 AB12 28.4 14.7 25,800 23,855 21,909

10 BT2 & BT3

combined 46.5 28.0 39,611 35,316 31,021

11a BT3 26.8 16.4 16,074 13,663 11,252

11b BT3 26.8 16.4 25,800 24,046 22,293

12 BT4 14.9 6.8 3,440 2,749 2,058

13 BT5 7.3 5.0 4,472 4,092 3,712

14 BT6 16.4 8.5 5,848 4,448 3,048

15 BT8 9.4 4.6 3,096 2,297 1,498

16 RU3 71.3 37.7 44,340 35,617 26,894

17 RU5 29.8 18.6 19,850 16,975 14,100

3. Credit for Upstream LIDA

Sizing Reduction Factors

4. Analysis of Alternative LIDA

Configurations

2

3

4. Analysis of Alternative LIDA

Configurations

2

4

LIDA

Configuration

LIDA Planter as

Shown in the

Manual

LIDA Planter

Plus Additional

Growing Media

LIDA Planter

Plus Additional

Ponding

LIDA Planter Plus

Ponding and

Growing Media and

Unlined

LIDA Planter

Plus Growing

Media and

Unlined

LIDA Planter

Plus Ponding

and Growing

Media and Dead

Storage and

Unlined

LIDA Planter

Plus Ponding

and Growing

Media and No

Underdrain and

Unlined

Max Ponding

Depth (in) 6 6 12 12 6 12 12

Growing Media

Depth (in) 18 24 18 24 30 30 30

Drain Rock Layer

Depth (in) 12 12 12 12 12 15 12

Dead Storage (in) 3 3 3 3 3 6 12

Lined Yes Yes Yes No No No No

INFILT Value for

Facility (in/hr) NA NA NA 0.2 0.2 0.2 0.2

Sizing Factor

(%Impervious

Area) 31.5% 12% 16.5% 8.5% 7.25% 6.75% 6.4%

Total Facility

Depth (ft) 3.17 3.67 3.67 4.17 4.17 4.92 4.67

5. Results - Overview of Regional

Facility Layout

• Required design elements:

Must meet District D&C Standards.

Footprint must match preliminary design.

Outflow restriction (orifice) must match

preliminary design.

• Flexibility in design:

Location of facility.

The District is open to alternative designs that

meet minimum requirements.

Modified LIDA to address water quantity.

5. Results

5. Results (example Preliminary Design)

5. Results (preliminary design)

5. Results - Costs

Questions and

General Discussion

Contact:

Jadene Stensland, PE

Phone: 503-681-3662

Email: stenslandJ@CleanWaterServices.org