FAIRFAX COUNTY PUBLIC FACILITIES MANUAL

FAIRFAX COUNTY PUBLIC FACILITIES MANUAL

IMPERVIOUSNESS

100%

3000

2500

QHPhM

PO*HKH

gSoS

PhO

CO

EH

2000

1500

1000

500

0 .20 .40 .60'C" FACTOR

.80 1.0

Ref. Sec. 6-0402

Rev. 1-00, 2011 Reprint

WATER QUALITY STORAGEREQUIREMENTS RELATED TOPERCENT IMPERVIOUSNESS

AND RATIONAL FORMULAC FACTOR

PLATE NO. STD. NO.

2-6


Precast concrete wheelstopspaced to allow runoff toreach trench

Filter fabric failure plane(see note #3)

Filter gravel layer(see note #3)

inPavement Section or Top Soil;ction or lop aon qo

c x x x x )( x )U( y )( x xjjpn o

& & ooooo

oooooo

Overlap2' Min.

OOO

Provide temporary coverduring construction

OOOoooo

ooo o

oo

Non-woven geotextile fabric(see note #1)

Aggregate ReservoirVDOT #57 Stone ooo

,;Sand layer (see note #2) • ;'• ;" • • ;'•

V

- 2' min.—-A ,(typ.) V

v U— 2' min. -V (typ-)

- Key in sidefabric at top-1 min.

I#XV

NOTES:l Use non-woven geotextile fabric with AOS of 70-100 US Sieve or 0.2 mm - 0.15 mm as

determined by ASTM D4751 and a trapezoidal tear strength of 45 LB. or 0.2 kN asdetermined by ASTM D4533.

2. An 8-in. deep bottom sand layer (VDOT Fine Aggregate, Grading A or B) is required.

3. For an aggregate surface trench, filter fabric shall surround all of the aggregate fillmaterial except the top one foot. A separate piece of fabric shall be used for the toplayer to act as a failure plane. This top piece can then be removed and replaced uponclogging.

4. Geotextile fabric shall not be exposed to direct sunlight for more than 24 hours priorto installation.

Ref. Sec. 6-1303.7B,6-1303

Rev. 1-00, 6-04, 10-06,2011 Reprint_

PERCOLATION TRENCHPLATE NO.

41A-6

STD. NO.


54.0 -

40.5 -

33.8

wa

5 minute time of concentration

1 impervious acre(C x A from the Rational Formula)1 square inch = ( 6.75 CFS ( 10 min. )( 60 sec./min. ) = 4,050 ft?

27.0

20.3 -

13.5 -

6.75 -

9.2 square inches = 37,300 ft10.5 CFS

*This value runs approximately.75 times the 10 year value.

TIME ( Minutes )

Ref Sec 6-1305.8B(l),6— 1305.9A

Rev. 1-00

UNIT FLOW HYDROGRAPH2 YEAR* - 2 HOUR

STORM

PLATE NO.

42-6

STD. NO.


90,000

80,000

70,000

60,000

wu 50,000

WO<CPS

§ 40,000

30,000

20,000

10,000

Elevation

discharge

15 Dia. culvert +slot discharge

15 Dia. culvertdischarge Elevation

storage

ELEVATION ( ft )

Ref. Sec. 6-1305.8B(5),6-1305.8B(6), 6-1305.9C,6-1305.10E

Rev. 1-00, 2011 Reprint

DISCHARGE - 15

CULVERT

PLATE NO. STD. NO.

43-6

S3 A < I O O

cno O X o a X H » > H H

H O X

d H a a O a

O1

-1

k;a

aÿi

1K

roÿ O

a»

o do Q >

HM

o a

4ÿ

4ÿ I Oi

H M 5!

O CO H a o

CO fa o H I *O ÿJ fa

1sq

uare

inch

=(

10

CFS

)(5

min

ute

s)(

60

sec. /m

inute

s)=

30

00

ft33

4,5

80

ft3-3

1,8

00

ft32

,78

0ft3

12

20

ft3/m

inut

e=

2.3

min

ute

s

Use

17

min

ute

s

•In

flow

hydro

gra

ph-

9.0

imp

erv

iou

sa

cre

s

15

min

ute

sS

ec.

2

17

min

ute

s

25m

inute

sS

ec.

1

25m

inu

tes

toS

ec.

114.7

squ

are

inch

es

x3000

=44,0

00

ft315

min

ute

sto

Sec.

21

0.6

squ

are

inch

es

x3000

=3

1,8

00

ft312,2

00

ft3/

10

mj

12

20

ft3/

min

ute

Ap

pro

xim

ate

Ou

tflo

wH

ydro

gra

ph

15.3

CFS

max.

allo

wable

20

25

TIM

E(

min

ute

s)

AR

EA

TO15.3

CFS

=1

6.2

in2

AP

PR

OX

.V

OLU

ME

REQ

UIR

EDF

OR

10

YR

.S

TOR

AG

E=

16

.2x

30

00

=4

8,6

00

ft3

a > HH a a > x n o d X H X a d a •—i o a > n i—i

a •—i H i—i

a ui > d > a

FAIRFAX COUNTY PUBLIC FACILITIES MANUAL1.0

0.5

0.1

lb/ft'

0.05

0.01

ÿ

EXPLANATION

mm1 * ID

Niditia ID - IDCfnpitt ID - tD

N » nuFib-er «r tie** rtquirtd tecffti: LS1 pent L ÿÿa L 1 -na of th*S|il11-Spuon sandier ltdtad La adnJL* tf 1" dNcn »1th ÿ 14D lb,irtlght rilling H",

/f rpV

/

oV

of

5,0 10.0

PLASTICITY INDEX - P.I.

SOURCE: Federal Highway Administration (IP-87-7) 1988Design of Roadside Channels with Flexible Linings

oo.o

Ref. Sec. 6-0203.4A(2)

Rev. 1-00, 2-06, 2011Reprint

PERMISSIBLE SHEAR STRESS

COHESIVE SOILS

PLATE NO. STD. NO.

76-6


Standardmanhole

Provide end cap or valve for facilitiesdesigned to infiltrate or detain stormwater. See Sections 6-1304.4D and6-1304.4G.

6" clean-out/observation-

Stone surfaceopen withrecharge bed

2.5 minimum thicknessporous asphalt pavement

Curb stop

2 min

S

solid pipe at inlet

Bedding course1.0-2.0" VDOT #57 stone

Base course VDOT #3 stone(#2 or #57 optional)

subgrade

Filter Fabric SeeSection 6-1304.8F& 6-1304.9E

4" dia. perforated underdrain withthreaded end cap with a minimum of2" of stone above and below the pipe.See Sections 6-1304.7 and 6-1304.8E.

Notes:1) The Director may approve variations

of this design provided the facilitymeets the requirements of Sec.6-1304 et seq.

2) All pipe shall be in accordance withSection 6-1304.8E.

CROSS SECTION (NTS)Ref. Sec. 6-1304et seq.

Rev. 3-07

POROUS ASPHALT PAVEMENTEXTENDED AGGREGATE BASE

PLATE NO.

78-6

STD. NO.

FAIRFAX COUNTY PUBLIC FACILITIES MANUALNotes:l)The Director may

approve variations othis design providedthe facility meetsrequirements of Sec.6—1304 et seq.

2)A11 pipe shall bein accordance with6— 1304.8E.

3)Provide end cap orvalve for facilitiesdesigned to infiltrateor detain stormwater. See Sections6— 1304.4D and6— 1304.4G.

Reinforced

ÿInterlocking open joint pavementblock, 3 1/8" min. thickness

-Bedding course 1.5—3"VDOT #8 stone

-Filter fabric (optional)See Section 6-1304.8F

Stone fill VDOT #810-yr WSEL 6'below beddingcourse

Curb inlet withweir wallseparatingdistributionpipe fromunderdrain andoutflow pipe.See Plate 80-6

concrete edgerestraint6" x 18"mr

Clean—out/observation wellwith load-bearing cap(typ.)

Gutter pan

length varies

10-yrWSEL

mm.

1 I O O O 3 <1 O o o o o 0""' o

End cap or valve(See Note 3)

Screen orinvertedelbow

/-Weir wall

min.

Filter fabric onsides and botton(see Sections6-1304.8F and6-1304-9E)

Base course VDOT #57 stone(#2 and #3 optional withadequate choker course ofVDOT #57 stone)

4" dia. perforatedunderdrain withthreaded end capwith a minimum of2" of stone above andbelow the pipe. SeeSections 6—1304.7 and6— 1304.8E. Min. 12"section of solid pipeat inlet.

CROSS SECTION (NTS)

Perforateddistribution pipewith end cap (sizedfor 10—year flow)

Choker course VDOT

#57 stone (requiredfor base courseusing #2 or #3stone)

Ref. Sec. 6-1304et seq., Plate80-6

Rev. 3-07

PERMEABLE OPEN JOINTPAVEMENT BLOCK

PLATE NO.

79-6

STD. NO.


Perforateddistribution

pipe with screen MH cover

Weir wall set atelevation of crown

WeepholesPerforated underdrain —with end cap or valve

Notes:For cross—section A—A see Plate79-6.Distribution pipe sized to conveystormwater in excess of the waterquality to the aggregate base or

Discharge pipe1) For cross—section A—A see Plate

79-6.Distribution pipe sized to conveystormwater in excess of the waterquality to the aggregate base orstorage chambers below the perviouspavement.This is intended as an example only.The designer may use otherconfigurations, including separateinflow and outflow structures whichmay include manufactured waterquality inlets.

3)

PLAN VIEW (NTS)Ref. Sec. 6-1304et. seq., Plate79-6Rev. 3-07, 2011Reprint

EXAMPLE INLET SCHEMATICFOR PERVIOUS PAVEMENT

PLATE NO.

80-6

STD. NO.


Adjacent to curb

2 FT.2—3 double shreddedhardwood mulch1 FT.

r2.5' min. bioretention, Ssoil media

V 10-YR. WSELV BMP WSEL

1' max

Soil mediadepth, variesWidth varies

minDepthvaries

Filter fabricSee Section 6-1307.9D

Soil Media_10-35% Topsoil

5-15% Organic Compost60-75% Sand, ASTM C-33

--VDOT #57 stone

4" dia. perforated underdrain

Notes:1) Side slopes of the facility excavated below

ground may be as steep as the in situ soilswill permit. All excavation must beperformed in accordance with VOSHrequirements.

2) All pipe shall be in accordance with Section6-1307.9C.

CROSS SECTION VIEW (NTS)

Ref. Sec. 6-1307et. seq.

Rev. 3-07

BIORETENTION FILTER ORBASIN WITH STONE STORAGE

PLATE NO.

82-6

STD. NO.


Standardyard inlet

Unrestricted underdrain. Bioretentionfilter does not use end cap or valve.

I 6 ' min. to topt of facility

V 10-YR. WSELV BMP WSE

1 max.

//y/%v/Y/%v/V/V/yyV/ i

= = FF FF F= =

6" dia. clean-out/observation wellwith screw orflange type capextending abovethe 10-yr. WSEL

solid pipe at inlet

2 —3 double shredded-hardwood mulch

2.5' min. bioretention soilmedia

subgrade

Soil Media10-35% Topsoil

5-15% Organic Compost60-75% Sand, ASTM C-33

ÿFilter FabricSee Section 6-1307.9D

4" dia. perforated underdrain withthreaded end cap placed in a layer ofVDOT #57 stone wrapped in filterfabric with a minimum of 2" of stoneabove and below the pipe. SeeSections 6-1307.7, 6-1307.9C and6-1307.9D.

Notes:1) The Director may approve variations

of this design provided the facilitymeets the requirements of Sec.6—1307 et seq.

2) All pipe shall be in accordance withSection 6-1307.9C.

PROFILE VIEW (NTS)Ref. Sect. 1307et seq.

Rev. 3-07

BIORETENTION FILTER

PLATE NO.

83-6

STD. NO.


Provided threadedend cap for bioretentionbasin with an orifice(valve optional).

Standardyard inlet

mm. totop offacility

V 10-YR. WSELV BMP WSEL

1 max.

//y/%v/Y/%v/V/V/yyV/ i

iHH

= = = = = = = =N=N FflfflRRRR

Notes:1) The Director may approve

variations of this designprovided the facility meets therequirements of Sec. 6-1307et seq.

2) All pipe shall be inaccordance with Section6-1307.9C.

6" min. dia. dropinlet with screenset at BMP WSEL

solid pipe at inlet

double shredded —'hardwood mulch

2.5' min. bioretention soilmedia

subgrade

Soil Media10-35%

5-15%60-75%

TopsoilOrganic CompostSand, ASTM C-33

Filter FabricSee Section6-1307.9D

4" dia. perforated underdrain withthreaded end cap placed in a layer ofVDOT #57 stone wrapped in filter fabricwith a minimum of 2" of stone aboveand below the pipe. See Sections6-1307.7, 6-1307.9C and 6-1307.9D.Storage for detention or infiltrationprovided by additional stone or stonein combination with storage chambers

PROFILE VIEW (NTS)Ref. Sec. 6-1307et seq.

Rev. 3-07

BIORETENTION BASINPLATE NO.

84-6

STD. NO.

» (T> < CO I o -a

2.W

rf

fo Hs

to•

(D ,nw

•n> o O

i I CO o ÿ3

a > </i o a H > H tr1 O > X H HH O a H M O

a HH O a a H M x H HH O X a H M a o a

a oi l 05

H M O CO H O O

Note

:1)

The

Directo

rm

ay

ap

pro

ve

va

ria

tio

ns

of

this

desig

npro

vid

ed

the

facility

meets

the

requirem

ents

of

Se

c.6

-13

07

et

seq.

All

pip

eshall

be

inaccord

ance

with

Se

ctio

n6—

1307.9

C.

2)

6"

min

.to

top

of

facility

6"

min

.dia

.P

VC

dro

pin

let

with

scre

en

set

at

BM

PW

SE

L

VB

MP

WS

EL

—1

A9

Tm

ax.

solid

pip

e

2"—

3"

double

shre

dded

hard

wood

mu

lch

So

ilM

ed

ia

2.5'

min

.b

iore

ten

tio

n-

soil

me

dia

sub

gra

de

10-3

5%

Topso

il5

-15

%O

rganic

Co

mp

ost

60

-75

%S

an

d,

AS

TM

C-3

3

PR

OF

ILE

VIE

W(N

TS

)

Filte

rF

ab

ric

See

Se

ctio

n6-1

307. 9

D

4"

dia

.perf

ora

ted

underd

rain

with

thre

aded

en

dca

pp

lace

din

ala

yer

of

VD

OT

#57

sto

ne

wra

pped

infilter

fab

ric

with

am

inim

um

of

2"

of

sto

ne

ab

ove

an

dbelo

wth

ep

ipe

.S

eeS

ectio

ns

6-1

30

7.7

,6-1

307.9

Ca

nd

6-1

307. 9

D.

Sto

rage

for

de

ten

tio

no

rin

filtra

tio

npro

vid

ed

by

additio

nal

sto

ne

or

sto

ne

inco

mb

ina

tio

nw

ith

stora

ge

ch

am

be

rs.

HH > X n o ed X H id cd a tr> HH o > o HH t r1

HH H HH M U1 > X cd > tr1


Vegetated Filter StripSee Section 6-1307.4D

/ \V JPps>.A .O- N -Outlet StructureSee Plate 85-6

PLAN VIEW (NTS)

Ref. Sec. 6-1307et. seq., Plate85-6Rev. 3-07, 2011Reprint

PLATE NO. STD. NO.BIORETENTION

FILTER & BASIN 86-6


Limits of

6 mm.check damsylO-YR. ws

V BMP WSEL

1.5 max check\V \l/ w w w \v \v

</Width varies2-10

&)<zf~Tc

Bioretention soil media2.0' min. depth


Soil Media10-35%

5-15%60-75%

TopsoilOrganic compostSand, ASTM C-33

— VDOT #57 stone


Notes:1) Side slopes of the facility excavated

below ground may be as steep as thein situ soils will permit. Allexcavation must be performed inaccordance with VOSH requirements.

2) All pipe shall be in accordance withSection 6-1307.9C.


Ref. Sec. 6-1308et seq.

Rev. 3-07

VEGETATED SWALEWITH CHECK DAMS

PLATE NO.

87-6

STD. NO.


Limits of swale

ylO-YR. WSEL

II J V BMP WSEL

3 max.WW

,//\/Width varies/x/yx/yy

Bioretention soil media1.0' min. depth


Soil Media_10-35% Topsoil

5-15% Organic compost60-75% Sand, ASTM C-33

--VDOT #57 stone


Notes:1) Side slopes of the facility excavated

below ground may be as steep asthe in situ soils will permit. Allexcavation must be performed inaccordance with VOSH requirements.

2) All pipe shall be in accordancewith Section 6-1307.9C.


Ref. Sec. 6-1308et. seq.

Rev. 3-07

VEGETATED SWALEGRASS WITHOUT CHECK DAMS

PLATE NO.

88-6

STD. NO.

S3 <D < CO I o -J

2.S3

d-

(t,

Ha

Cfl

•m >o

ui

•0

) o Oi I CO o C

D

•nd

t r1 > > X O

< M Q M H > H M

50c/

3O d i—

id M

> d M

CD

CD I 05

T) £ H M Z O CO H O 2 O

So

ilM

edia

10

%-3

5%

To

pso

il5%

-15%

Org

anic

com

post

60

%-7

5%

Sa

nd

,A

ST

MC

-33

10'

max."

bottom

wid

th

Underd

rain

Note

s:1)

Th

eD

irecto

rm

ay

ap

pro

veva

ria

tio

ns

of

this

de

sig

np

rovid

ed

the

facility

meets

the

requirem

ents

of

Se

ctio

n6

—1

30

8e

tse

q.

All

pip

eshall

be

inaccord

ance

with

Se

ctio

n6-1

307. 9

CO

utlet

pro

tectio

nif

required

2'

min

.b

ott

om

wid

th

¥

Ou

tfa

llch

an

ne

l

Ch

eck

dam

ssp

ace

da

sn

ee

de

d

Open

ch

an

ne

lif

required

DC

RS

td.

3.1

7

-3:1

max.

sid

esl

opes

PLA

NV

IEW

(NT

S)

2.0'

min

.bio

rete

ntion

soil_

\

6"

clea

n-ou

t/o

bse

rva

tio

nw

ell

100'

on

ce

nte

r

-6"

dia

.cl

ean—

out/

ob

se

rva

tio

nw

ell

with

scre

wo

rflange

type

cap

tooutfall

mm

.5m

ax.

ÿm

I1I1

P=1

11=1

1

leelij

eS

ub

gra

de

6d

ia

Filte

rfa

bric

VD

0T

#1sto

ne

with

filter

fabric.

The

use

of

asto

ne

ch

eck

dam

isan

exa

mple

only

.C

he

ckdam

sm

ayb

eco

nstr

ucte

dof

oth

er

non-e

rosiv

em

ate

ria

ls,

ea

rth

be

rms,

or

bio

-lo

gs.

See

Se

ctio

n6—

1308.9

E.

T.,

,..

,,

_„

Lo

ng

itu

din

al

slope

1o

/o

PR

OF

ILE

VIE

W(N

TS

)

underd

rain

with

"2"

VD

0T

#57

st°

ne

end

ca

p

d > h-i 5d d > X o o d X H X d d td d HH o d > n HH d HH H HH d in > d > d


Note:1) The Director may

approve variations ofthis design providedthe facility meetsthe requirements ofSec. 6-1309 et seq.

2) All pipe shall be inaccordance withSection 6-1307.9C.

4" dia. perf.underdrain pipe

Discharge to-approved outfall4 dia. solid pipe

VegetationSee Sec. 6-1309.8

Grate and frameH-20 loading

Cleanout 4" dia. pipewith screw or flangetype cap

4 dia. perf.underdrain

VDOT #57 stone with amin. of 2" of stone aboveand below the pipe. SeeSees. 6-1309.6 and6-1309.7C.

Concrete box:pre-cast or cast-in-placeSee Section 6-1309.4F

PLAN VIEW

Inlet

Gutter

Open bottom(optional)See Section6— 1309.4G

VDOT #3 stone6" width and depth

ÿ2-3" double shreddedhardwood mulch

bioretention soil media35% Topsoilÿ15% Organic Compost75% Sand, ASTM C-33

CROSS SECTION A-A'Ref. Sec. 6-1309et seq.

Rev. 3-07

TREE BOX FILTER

PLATE NO.

90-6

STD. NO.


Note: The Director may approve variationsof this design provided the facility meetsthe requirements of Sec. 6-1310 et seq.

Low Plants: sedums/herbs (typ.)

Erosion control (windblanket or jute mesh)3" to 6" growth medium (typ.)

Filter Fabric (typ.)

Drainage Layer: 2"lightweight granular mix(optional: mat or plate system)

Filter Fabric (optional)

Aluminum Curb (typ.)Gravel (optional)

Vegetation-free stripgravel, pavers (typ.)

Thermal insulation (optional)

Leak Detection System (optional)Protection Layer (typ.)

Root Barrier (typ.)Waterproof Membrane (typ.)Roof Deck with Vapor Barrier

and Roof Structure

Perforated aluminum curb (typ.) w/ drainage fabricRoof drain with parapet well

Emergency overflow

CROSS SECTION VIEW (NTS)Ref. Sec. 6-1310et seq.

Rev. 3-07

VEGETATED ROOFEXTENSIVE

PLATE NO.

91-6

STD. NO.


Plants: perennials and shrubs

Erosion control (windblanket or jute mesh)6" to 12" growth medium (typ.)

Filter Fabric

Drainage: 4(optional: mat or plate system)

Note: TheDirector mayapprove variationsof this designprovided thefacility meets therequirements ofSection 6-1310 etseq.

to 6 granular

Filter Fabric (optional)

Aluminum CurbingGravel (optional)

Vegetation-free stripgravel, pavers (typ.)

Thermal Insulation (optional)Leak Detection System (optional)

Protection Layer (typ.)

Root Barrier (typ.)Waterproof Membrane (typ.)

Roof Deck with Vapor Barrierand Roof Structure

Perforated aluminum curb (typ.) w/ drainage fabric

Roof drain with parapet wellEmergency overflow

CROSS SECTION (NTS)Ref. Sec. 6-1310et seq.

Rev. 3-07

VEGETATED ROOFINTENSIVE

PLATE NO.

92-6

STD. NO.

FAIRFAX COUNTY PUBLIC FACILITIES MANUAL

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