training agenda engineer module – september 21, 2005 afternoon session: 1:30 pm to 4:00 pm...

TRAINING AGENDA Engineer Module – September 21, 2005

Afternoon Session: 1:30 pm to 4:00 pm

Engineers Training Exercise

Break: 2:15 – 2:30pm

– LID Project Objectives

– Master Planning Process• Integration into Site Analysis, Benefit Analysis, Site

Design Selection, Plan Development• Green Roof

– Discuss Traditional Site Plan vs. LID Approach

LID Project Objectives

LID Project Objectives

• LID approaches and techniques for the design of the MARFORLANT headquarters facility

– Feasibility– Potential effectiveness

LID Project Objectives

• Utilizing LID techniques and practices to meet:– Regulatory requirements– Federal government program goals

• Water conservation• Energy conservation• Environmental stewardship

– Natural resource program management objectives

MARFORLANT: Master Planning Process

• Meet Virginia Department of Conservation and Recreation (VDCR) stormwater management regulations.

• rainfall used for non-potable uses– irrigation or toilet flushing

• Ancillary benefits energy conservation – vegetated roof– strategic siting of vegetation.

MARFORLANT: Master Planning Process

• “GOVERNMENT BY EXAMPLE”

• Eliminate pond option by replacing the hydrologic and hydraulic functions with LID practices such as bioretention. – eliminating pond maintenance – pond vector issues.

Master Planning Process:Case Study MARFORLANT

• Integration into:–Site Analysis–Benefit Analysis–Site Design Selection–Plan Development

Master Planning Process: Site description

• 7.1 acres in size.• Site slopes gently

from the north and south

• Low point in the center of the property.

• mix of woods and grass

• The soils on site are compacted.

Master Planning Process: Proposal

• 55,000 sq. ft. building northern portion of site

• 280 parking spaces• Future building

planned western side of proposed facility.

• Conventional stormwater on western edge

• Woods should remain undisturbed

Master Planning Process: Hydrologic Analysis

• The Commonwealth of Virginia requires peak runoff post-development condition to equal or be below the discharge from the pre-development condition for:– 2-year 24-hour storm (with a six-inch depth )

• LID practices is three (3) percent, or 0.2 acres– 10-year 24-hour storm event for urban areas

• LID practices is eight (8) percent, or 0.6 acres

• Pre-and Post-development conditions are compared to determine a storage volume

Master Planning Process: Non-potable water

• Secondary non-potable usage – toilet flushing, cooling, irrigation

• Daily water demand 4,500 gpd for 300 office workers (15 gal per person per day)

• Cistern size of 14 diameter and height of 37 ft to capture and reuse water.

Master Planning Process: Non-potable water

LID Site Design

• Requirement of 8% of the site in LID features (10 yr 24 hr storm)– Runoff will sheet flow to a centralized

bioretention facility with several perimeter bioretention facilities

– Permeable surfaces on walkways– Green roof

Master Planning Process

Green Roof

Green Roof

• Conditions that have spurred green roof development– Prevalence of combined sewer systems– Antiquated and over-taxed sewer and waste

treatment facilities– Widespread pollution of rivers and estuaries– Frequent nuisance flooding– Limited space for instituting large

management facilities

Green Roof (continued)

• Driving factors for Green roof at MARFORLANT facility– Mitigate water runoff impacts – Compensate for the loss of green space – Limited treatment options for site are limited

• due to location of low point and high water table– Increases service life of roofing system– Reducing energy cost

Layers of Green Roof

• Waterproofing membrane• Root barrier (if the waterproofing is not

certified as root resistant)• Drainage layer• Separation layer• Growth media layer• Plants

Green Roof: Pollution Removal

• It is estimated 30% of all nitrogen and phosphorus in local streams is from roof runoff

• Green roof have demonstrated the removal of:– 68% of total phosphorus – 80% of total nitrogen

Green Roof Benefits: Energy

• Estimated 10% reduction in air-conditioning related energy costs

• Roofing system is expected to last 2-3 times longer than normal

Traditional Site Plan vs. LID Approach

Traditional Site Plan vs. LID Approach

Conventional

• large capital investments in complex and costly engineering strategies

• pipes water to low spots as quickly as possible

LID Design

• Integrates, green space, native landscape, natural hydrology functions to generate less runoff.

• Uses micro-scale techniques to manage precipitation close to where it hits the ground

Traditional Site Plan vs. LID Approach

Conventional vs. LID:

Comparision of CN and Peak Discharge

0102030405060708090

CN () Peak Discharge(CFS) 2-year Storm

3” Depth

Peak Discharge(CFS) 10-year Storm

5” Depth

Conventional CN ()LID DesignExisting Condition

Conventional vs. LID

Volume Comparision

0

0.5

1

1.5

2

2.5

3

3.5

4

Volume (Depth in Inches) 2-YearStorm Event

Volume (Depth in Inches) 10-Year Storm Event

Volu

me

(dep

th in

) Conventional CN

LID Design

Existing Condition

Conventional vs. LID Total costs

Cost per length of pipe per ftC = 0.54D1.3024

for D = $14.40 (12in) D = $30.10 (24 in)

C ($/ft) = 14.45 (12 in) – 37.77 (24 in)

1999 dollars

Cost of grass swale per ft

C/L = K

K = 5-14

C ($/ft) = 5 - 14

No land cost where considered, but could be significant

Cost Savings of LID Techniques

• Reduced downstream erosion and flood control. – preventing costly clean up and stream bank

restorations.

• Infrastructure and development costs. – LID techniques reduces infrastructure

requirements • decreases the amount of pipes, roadways,

detention facilities

Cost Savings of LID Techniques

• Improved groundwater recharge, drinking water, and decreased treatment costs. – Atlanta’s tree cover has saved over $883

million by reducing the need for stormwater facilities.

– forest cover in the source area can reduce treatment cost 50 to 55%

– Every 10% increase in forest cover • treatment and chemical costs decreased

approximately 20%

Funding Aspects

Funding

• Joint Effort – Department of Energy National Renewable

Energy Research Laboratory (NREL)– Federal Management Program (FEMP)– Atlantic Division of the Naval Facilities

Engineering Command (LANTDIV)

Design Exercise

•H and H methods•Strategies and Techniques•Results

Picture NRCL Norfolk

VS/VR

Solution of Runoff Equation

PG Chart

Filterra Sizing/Freq DistRainfall

Runoff Volume (cu ft

/ hr)

Runoff Treated (cu ft / hr)

Cumulative Frequency

Probability Frequency

(c) x (e) (cu ft / hr)

(b) x (e) (cu ft / hr)(in / hr)

0.02 17 17 0.421 0.4205 7.25 7.25

0.04 34 34 0.603 0.1822 6.28 6.28

0.06 52 52 0.713 0.1106 5.72 5.72

0.08 69 69 0.785 0.0717 4.95 4.95

0.10 86 86 0.835 0.0502 4.33 4.33

0.13 108 108 0.875 0.0393 4.24 4.24

0.15 129 129 0.903 0.0285 3.69 3.69

0.20 172 172 0.938 0.0352 6.07 6.07

0.25 216 216 0.957 0.0188 4.05 4.05

0.30 259 259 0.969 0.0117 3.03 3.03

0.35 302 302 0.976 0.0069 2.08 2.08

0.40 345 303 0.981 0.0054 1.64 1.86

0.45 388 303 0.986 0.0046 1.39 1.78

0.50 431 303 0.988 0.0025 0.76 1.08

0.55 474 303 0.990 0.0018 0.55 0.85

0.60 517 303 0.992 0.0019 0.58 0.98

0.65 560 303 0.993 0.0012 0.36 0.67

0.70 603 303 0.994 0.0012 0.36 0.72

0.75 647 303 0.995 0.0008 0.24 0.52

0.80 690 303 0.996 0.0007 0.21 0.48

0.90 776 303 0.997 0.0014 0.42 1.09

1.00 862 303 0.998 0.0008 0.24 0.69

1.50 1293 303 1.000 0.0020 0.61 2.59

2.00 1724 303 1.000 0.0001 0.03 0.17

Totals 1.0000 59.07 65.17

Simple Method

L = 0.226 x R x C x A

Where: L = Annual load (lbs) R = Annual runoff (inches) C = Pollutant concentration (mg/l) A = Area (acres) 0.226 = Unit conversion factor

Simple Method

D = L x (1-E)

Where: D = Annual load reduction (lbs) L = Annual load (lbs) E = Pollutant removal efficiency

(fraction)

Bioretention Files

AB = area of bioretention, ft2

C = rational c coefficientI = rainfall intensity, in/hrA = drainage area, acresTc = time of concentration, minDs = storage depth in

bioretention, in.Db = bioretention media depth,

ftIr = soil infiltration rate, in/hr

Low Impact Development Objective

Flat

ten

Slop

e

Incr

ease

Flo

w P

ath

Incr

ease

She

et F

low

Incr

ease

Rou

ghne

ss

Min

imiz

e D

istu

rban

ce

Lar

ger

Swal

es

Flat

ten

Slop

es o

n Sw

ales

Infil

trat

ion

Swal

es

Veg

etat

ive

Filte

r St

rips

C

onst

rict

ed P

ipes

D

isco

nnec

ted

Impe

rvio

us A

reas

R

educ

e C

urb

and

Gut

ter

Rai

n B

arre

ls

Roo

ftop

Sto

rage

B

iore

tent

ion

Re-

Veg

etat

ion

Veg

etat

ion

Pre

serv

atio

n

Increase Time of Concentration X X X X X X X X X X X

Increase Detention Time X X X X

Increase Storage X X X X X X

Lower Post Development CN X X X X X

LID Techniques and ObjectivesLow-Impact Development Technique

Maintain Time ofConcentration (Tc)

Low Impact Developmentobjective to Maintain Time ofConcentration (Tc) B

alan

ce c

ut a

nd fi

ll on

lot.

Net

wor

k Sm

alle

r Sw

ales

Clu

ster

s of

Tre

es a

ndSh

rubs

in F

low

Pat

h

Prov

ide

Tre

eC

onse

rvat

ion

on L

ots

Elim

inat

e St

orm

Dra

inPi

pes

Dis

conn

ect I

mpe

rvio

usA

reas

Save

Tre

es in

Sm

alle

rC

lust

ers

Ter

race

Yar

ds

Dra

in fr

om H

ouse

and

then

Red

uce

Gra

des

Minimize Disturbance X X X X X

Flatten Grades X X

Reduce Height of Slopes X X

Increase Flow Path (Divert andRedirect)

X X X X

Increase Roughness “n” X X X X X

X

X X

X

X

X X

Low-Impact Development Technique

Example Retrofit: Anacostia Annex of the Washington Navy Yard

• Currently no stormwater management – quantity or quality controls

• Replacement of the parking area is required. • Drainage inlets and old brick drainage

structures need to be replaced. • Sidewalk needs to be replaced • The site does not comply with Americans with

Disabilities Act (ADA) Standards.

PROJECT OBJECTIVES

• Integrate LID practices into the repaving of parking areas

• Repair the sidewalks• Re-landscape Pollutants of concern for this watershed are:

– oils and grease– total suspended solids– nitrogen and phosphorus.

RANK AND PRIORITIZE OPPORTUNITES

• Greatest potential to reduce non-point source pollutant loads

• Minimal costs for new materials • Minimal maintenance cycles, costs, and

training• Ancillary benefits (landscaping, energy

conservation, water conservation)

SITE CONDITIONS• The site has minimal

topographic relief. • groundwater table is

approximately 3 feet below the surface.

• soils have poor infiltration rates.

• There is an existing drainage system below the buffer.

LID Site Conditions

Results

MWR Pics

Addressing Drainage (1-5)

• Drainage Areas One through Three: – three bioretention cells, a bioretention swale, and a

footpath using permeable pavers.

• Drainage Area Four: – A tree box filter

• Drainage Area Five: – Permeable pavers will be constructed in the existing

valley

Addressing Drainage (6-9)• Drainage Area Six: A bioretention cell will be

constructed within a vegetated island.

• Drainage Area Seven: Pavement will be removed and replaced with a bioretention cell.

• Drainage Area Eight: Permeable pavers will be constructed, a sand layer may be incorporated to increase efficiency.

• Drainage Area Nine: A bioretention cell will be located to the east of the access road.

LID Site Design

Site

Proposed Conventional

Composite Curve Number Calculation for Existing Condition

Weighted CN = Sum of Products ÷ Drainage Area

Curve Number Existing Condition and Proposed Condition

Condition Runoff (in)

Existing (CN = 63) 1.5

Proposed (CN = 80) 2.9

Proposed LID

Conventional vs. LID

Condition CN Tc

Peak Discharge (CFS) Runoff depth (in.)

2-year (3” depth)

10-year (5” depth)

2-year

10-year

Existing Condition 63 0.24 2 10 0.4 1.5

Proposed Condition – conventional CN

80 0.22 9 23 1.3 2.9

Proposed Condition using LID site design

73 0.24 6 17 0.9 2.3

Conventional

LID

Conventional

LID