stormwater drainage report
TRANSCRIPT
STORMWATER DRAINAGE REPORT
Prepared for:
BAYONNE EQUITIES BII URBAN RENEWAL, LLC
Proposed Mixed-Use Development
9-11, West 12th Street & 281, 283-287, 289 Broadway
Block 264, Lots 15, 16, 17, & 18
City of Bayonne
Hudson County, New Jersey
Prepared by:
245 Main Street, Suite 110
Chester, NJ 07930
(908) 879-9229
________
Joseph C. Sparone, PE, PP NJ Professional Engineer License #47204
March 2020
Revised August 2021
DEC #2838-99-001
Bayonne Equities BII, LLC
DECPC #2838-99-001 2 August 2021
TABLE OF CONTENTS
I. Introduction ............................................................................................... 3
II. Existing Site Conditions ............................................................................. 3
III. Proposed Site Conditions ........................................................................... 4
IV. Stormwater Management Basin Design ...................................................... 4
V. Runoff Rates …… .................................................................... …………....5
VI. Water Quality Storm …… ........................................................ …………....5
VII. Groundwater Recharge ………................................................. …………....5
VIII. Conclusion……… .................................................................... …………....6
APPENDIX
• NRCS Web Soil Survey
• Runoff Curve Number (CN) Calculations
• Existing & Proposed Hydrographs - Hydrograph Summary Reports for 2yr,
10yr, 25yr & 100yr Design Storms (Hydrographs created using Hydroflow 2007
by Intelisolve Computer Software)
• Drainage Area Maps
Bayonne Equities BII, LLC
DECPC #2838-99-001 3 August 2021
I. INTRODUCTION
The intention of this study is to analyze the stormwater drainage conditions that will occur as a result of the
proposed construction of a mixed-use (residential and commercial) building containing ground floor retail space
and multiple levels of parking. The subject site is located at 9-11West 12th Street & 281, 283-287 Broadway City
of Bayonne, Hudson County, New Jersey. The site is identified as Block 264; Lots 15, 16, 17, & 18 on the City
of Bayonne Tax Maps. The subject site is currently developed with a two (2) mixed-use buildings (one 2-story
and one 3-story) with an asphalt parking area on the southern portion of the property. The scope of this report
focuses on the overall drainage conditions within the Drainage Study Area.
The primary design constraints for this project are based on requirements established in the Amendments to 8th
Street Station Rehabilitation 281-295 Broadway, Lots 13-23 Rehabilitation Site #7 block 264, City of Bayonne
Land Development Ordinance, and the State of New Jersey Stormwater Regulations outlined in NJAC 7:8. In
general the stormwater management design will serve to maintain the existing drainage patterns while reducing
post-development site runoff rates when compared to pre-development runoff conditions.
The limit of disturbance for the project is approximately 23,007SF (0.53 acres); therefore, the project does not
meet the definition of a “major development” under NJAC 7:8 since less than one acre of disturbance and less
than a quarter acre of additional impervious surfaces are proposed. However, since the site is tributary to a
combined sewer conveyance system located within Broadway, stormwater reductions are required by the
Bayonne Department of Public Works.
II. EXISTING SITE CONDITIONS
The subject site consists of 18,827 SF (0.43 acres) the majority of which is developed as two (2) mixed-use
buildings with associated site improvements. The southern portion of the site is currently an asphalt parking
area. The site currently consists of 91.4% (0.4 acres or 17,224 SF) of impervious surface. The majority of the
runoff generated by the subject site, travels via overland flow to the intersection of West 12th Street & Broadway.
Where it is collected by an existing ‘B’ inlet and conveyed to the City’s storm system. The existing conditions
have been evaluated using single sub-watershed area ‘Ex DA-1’ as depicted on the existing conditions drainage
area map included within the appendix of this report. A minimum time of concentration of ten (10) minutes has
been utilized for the above drainage area.
Based upon the Hudson County Soil Survey, the soil types native to the site include:
SOIL TYPE SOIL TYPE NAME HYDRAULIC
SOIL GROUP
URTILB Urban Land, Till Substratum, 0 to 8 percent slopes D
Bayonne Equities BII, LLC
DECPC #2838-99-001 4 August 2021
III. PROPOSED SITE CONDITIONS
The proposed site improvements include the construction of a mixed-use building and shall result in an increase
in impervious coverage of 1,603 SF (0.04 acres). A stormwater management system is proposed to detain
stormwater runoff generated by the subject site in accordance with the stormwater runoff reduction requirements
set forth under NJAC 7:8 and by the Bayonne Department of Public Works. The existing drainage patterns will
be maintained to the extent possible.
The proposed site conditions have been evaluated using single sub-watershed area ‘ DA-1 Detained’ as depicted
on the Proposed Conditions Drainage Area Map included within the Appendix of this report. This area contains
the proposed building roof area that encompasses the majority of the overall site. The stormwater runoff
generated by this area shall be collected and conveyed to the stormwater management basin proposed within
the building. Stormwater will then be detained within the basin and released at a controlled rate to a proposed
inlet located at the intersection of West 12th Street and Broadway. Ultimately, stormwater runoff is conveyed to
the existing combined sewer system within Broadway similar to existing conditions.
IV. STORMWATER MANAGEMENT BASIN DESIGN
The intention of the design of the proposed stormwater management facilities is to provide measures as required
to address applicable aspects of the City of Bayonne Land Development Ordinance and N.J.A.C. 7:8. In order
to prepare the stormwater management design for the subject project, extensive initial investigation of the
property and a topographic survey was performed. On-site review of the tract was performed by a Dynamic
Engineer to verify existing site conditions and land cover characteristics. A Boundary and Topographic Survey
of the subject site was also prepared by Dynamic Survey, LLC to depict the existing conditions.
Based on our review of the existing site conditions, review of the survey, and establishment of the Drainage Area
Maps for the existing and proposed site conditions, the calculations as defined within this Report were
established. A Grading Plan and Drainage design was also developed for the proposed site improvements with
consideration to the existing drainage patterns. This design was prepared to ensure runoff from the proposed
development could be directed to the proposed stormwater management facility and reduce existing peak flow
rates.
Stormwater runoff rates for the site were modeled utilizing Hydraflow by Intelisolve computer software using
the Urban Hydrology for Small Watershed TR55 method for the applicable design storms. The 2-, 10-, and 100-
year design storms are based upon the New Jersey 24-Hour Rainfall Frequency Data for Hudson County as
published by the USDA NRCS utilizing a Type III rainfall distribution. Curve number calculations have been
included within the Appendix and are based upon HSG D as identified by the Hudson County Soil Survey. A
minimum time of concentration of ten (10) minutes was assumed for the existing and proposed conditions per
Bayonne Equities BII, LLC
DECPC #2838-99-001 5 August 2021
TR-55 and pervious and impervious areas were modeled separate as per the NJDEP Stormwater Management
Best Management Practices (BMP) Manual.
The stormwater management system will consist of a single concrete structure designed to detain the tributary
stormwater runoff generated by the roof area. Detained runoff will discharge at a controlled rate via the outlet
control structure that contains a weir wall, and ultimately is conveyed to the existing 24” Clay sewer main
located within Broadway.
Associated calculations are included in the Appendix of this report and details have been provided on the
accompanying engineering drawings.
V. RUNOFF RATES
The following is a comparison of pre- and post- development runoff rates:
Existing vs. Allowable Runoff Rates
Existing
Runoff
(CFS)
Required
Reduction
(%)
Allowable
Runoff
(CFS)
Proposed
Runoff
(CFS)
2 Year 0.98 50% 0.49 0.47
10 Year 1.52 25% 1.14 1.13
100 Year 2.56 20% 2.05 2.04
Per the above chart, the post-development rates are substantially reduced when compared to the pre-
development rates.
VI. WATER QUALITY STORM
The proposed development will not increase impervious coverage on-site by more than ¼ acre, therefore,
compliance with the stormwater quality standards under NJAC 7:8 is not required. However, it is important to
note that the majority of the stormwater runoff generated by the site is from the building roof area which is void
of vehicular traffic and can be considered ‘clean’.
VII. GROUNDWATER RECHARGE
The proposed project is located on a previously developed parcel located within the Metropolitan Planning Area
(PA-1) therefore, this project is exempt from the Groundwater Recharge requirements set forth by the City of
Bayonne and NJAC 7:8.
Bayonne Equities BII, LLC
DECPC #2838-99-001 6 August 2021
VIII. CONCLUSION
The proposed project has been designed in a manner so that it will not adversely impact the existing drainage
patterns, adjacent roadways or adjacent parcels. Further, stormwater runoff rates for the 2, 10 and 100 year
design storms will comply with the runoff rate reduction requirements set forth in NJAC 7:8 and by the city of
Bayonne. With that stated, it is evident that the proposed development will not have a negative impact on the
existing stormwater management system on-site or within the vicinity of the subject parcel.
APPENDIX
NRCS WEB SOIL SURVEY
Dep
th to
Wat
er T
able
—H
udso
n C
ount
y, N
ew J
erse
y
Nat
ural
Res
ourc
esC
onse
rvat
ion
Serv
ice
Web
Soi
l Sur
vey
Nat
iona
l Coo
pera
tive
Soil
Surv
ey3/
2/20
20Pa
ge 1
of 3
450098045009904501000450101045010204501030450104045010504501060
450098045009904501000450101045010204501030450104045010504501060
5739
2057
3930
5739
4057
3950
5739
6057
3970
5739
8057
3990
5740
0057
4010
5740
2057
4030
5740
4057
4050
5739
2057
3930
5739
4057
3950
5739
6057
3970
5739
8057
3990
5740
0057
4010
5740
2057
4030
5740
4057
4050
40° 3
9' 2
5'' N
74° 7' 32'' W40
° 3
9' 2
5'' N
74° 7' 26'' W
40° 3
9' 2
2'' N
74° 7' 32'' W
40° 3
9' 2
2'' N
74° 7' 26'' W
N
Map
pro
ject
ion:
Web
Mer
cato
r C
orne
r coo
rdin
ates
: WGS
84
Edge
tics
: UTM
Zon
e 18
N W
GS84
030
6012
018
0Feet
05
1020
30Met
ers
Map
Sca
le: 1
:624
if pr
inte
d on
A la
ndsc
ape
(11"
x 8
.5")
shee
t.
Soi
l Map
may
not
be
valid
at
this
sca
le.
MA
P LE
GEN
DM
AP
INFO
RM
ATIO
N
Are
a of
Inte
rest
(AO
I)Ar
ea o
f Int
eres
t (AO
I)
Soils So
il R
atin
g Po
lygo
ns0
- 25
25 -
50
50 -
100
100
- 150
150
- 200
> 20
0
Not
rate
d or
not
ava
ilabl
e
Soil
Rat
ing
Line
s0
- 25
25 -
50
50 -
100
100
- 150
150
- 200
> 20
0
Not
rate
d or
not
ava
ilabl
e
Soil
Rat
ing
Poin
ts0
- 25
25 -
50
50 -
100
100
- 150
150
- 200
> 20
0
Not
rate
d or
not
ava
ilabl
e
Wat
er F
eatu
res
Stre
ams
and
Can
als
Tran
spor
tatio
nR
ails
Inte
rsta
te H
ighw
ays
US
Rou
tes
Maj
or R
oads
Loca
l Roa
ds
Bac
kgro
und Ae
rial P
hoto
grap
hy
The
soil
surv
eys
that
com
pris
e yo
ur A
OI w
ere
map
ped
at
1:12
,000
.
War
ning
: Soi
l Map
may
not
be
valid
at t
his
scal
e.
Enla
rgem
ent o
f map
s be
yond
the
scal
e of
map
ping
can
cau
se
mis
unde
rsta
ndin
g of
the
deta
il of
map
ping
and
acc
urac
y of
soi
l lin
e pl
acem
ent.
The
map
s do
not
sho
w th
e sm
all a
reas
of
cont
rast
ing
soils
that
cou
ld h
ave
been
sho
wn
at a
mor
e de
taile
d sc
ale.
Plea
se re
ly o
n th
e ba
r sca
le o
n ea
ch m
ap s
heet
for m
ap
mea
sure
men
ts.
Sour
ce o
f Map
: N
atur
al R
esou
rces
Con
serv
atio
n Se
rvic
eW
eb S
oil S
urve
y U
RL:
C
oord
inat
e Sy
stem
: W
eb M
erca
tor (
EPSG
:385
7)
Map
s fro
m th
e W
eb S
oil S
urve
y ar
e ba
sed
on th
e W
eb M
erca
tor
proj
ectio
n, w
hich
pre
serv
es d
irect
ion
and
shap
e bu
t dis
torts
di
stan
ce a
nd a
rea.
A p
roje
ctio
n th
at p
rese
rves
are
a, s
uch
as th
e Al
bers
equ
al-a
rea
coni
c pr
ojec
tion,
sho
uld
be u
sed
if m
ore
accu
rate
cal
cula
tions
of d
ista
nce
or a
rea
are
requ
ired.
This
pro
duct
is g
ener
ated
from
the
USD
A-N
RC
S ce
rtifie
d da
ta a
s of
the
vers
ion
date
(s) l
iste
d be
low.
Soil
Surv
ey A
rea:
H
udso
n C
ount
y, N
ew J
erse
ySu
rvey
Are
a D
ata:
Ve
rsio
n 9,
Sep
16,
201
9
Soil
map
uni
ts a
re la
bele
d (a
s sp
ace
allo
ws)
for m
ap s
cale
s 1:
50,0
00 o
r lar
ger.
Dat
e(s)
aer
ial i
mag
es w
ere
phot
ogra
phed
: Ju
l 25,
201
9—Ju
l 30,
20
19
The
orth
opho
to o
r oth
er b
ase
map
on
whi
ch th
e so
il lin
es w
ere
com
pile
d an
d di
gitiz
ed p
roba
bly
diffe
rs fr
om th
e ba
ckgr
ound
im
ager
y di
spla
yed
on th
ese
map
s. A
s a
resu
lt, s
ome
min
or
shift
ing
of m
ap u
nit b
ound
arie
s m
ay b
e ev
iden
t.
Dep
th to
Wat
er T
able
—H
udso
n C
ount
y, N
ew J
erse
y
Nat
ural
Res
ourc
esC
onse
rvat
ion
Serv
ice
Web
Soi
l Sur
vey
Nat
iona
l Coo
pera
tive
Soil
Surv
ey3/
2/20
20Pa
ge 2
of 3
Depth to Water Table
Map unit symbol Map unit name Rating (centimeters) Acres in AOI Percent of AOI
URTILB Urban land, till substratum, 0 to 8 percent slopes
>200 0.8 100.0%
Totals for Area of Interest 0.8 100.0%
Description
"Water table" refers to a saturated zone in the soil. It occurs during specified months. Estimates of the upper limit are based mainly on observations of the water table at selected sites and on evidence of a saturated zone, namely grayish colors (redoximorphic features) in the soil. A saturated zone that lasts for less than a month is not considered a water table.
This attribute is actually recorded as three separate values in the database. A low value and a high value indicate the range of this attribute for the soil component. A "representative" value indicates the expected value of this attribute for the component. For this soil property, only the representative value is used.
Rating Options
Units of Measure: centimeters
Aggregation Method: Dominant Component
Component Percent Cutoff: None Specified
Tie-break Rule: Lower
Interpret Nulls as Zero: No
Beginning Month: January
Ending Month: December
Depth to Water Table—Hudson County, New Jersey
Natural ResourcesConservation Service
Web Soil SurveyNational Cooperative Soil Survey
3/2/2020Page 3 of 3
RUNOFF CURVE NUMBER (CN) CALCULATIONS
Pro
ject:
Ba
yo
nn
e E
qu
itie
s B
II,
LL
CC
om
pu
ted
By:
JF
R
Jo
b #
: 2
83
8-9
9-0
01
Ch
ecke
d B
y:
MR
Lo
ca
tio
n:
Ba
yo
nn
eD
ate
: 3
/3/2
02
0
Exis
tin
g D
rain
ag
e A
rea
Imp
erv
iou
s
Are
a (
acre
)
Imp
erv
iou
s
Are
a (
sf)
Cu
rve
Nu
mb
er
(CN
) U
sed
HS
G D
-
Op
en
Sp
ace A
rea
(acre
)
HS
G D
-
Op
en
Sp
ace A
rea
(sf)
Cu
rve N
um
ber
(CN
) U
sed
Avg
. C
urv
e
Nu
mb
er
To
tal A
rea
(acre
s)
To
tal A
rea
(SF
)
TC
(M
in.)
EX
DA
-10.4
017,2
24
98
0.0
41,6
03
80
96
0.4
318,8
27
10
0.4
318,8
27
Pro
po
sed
Dra
inag
e A
rea
Imp
erv
iou
s
Are
a (
acre
)
Imp
erv
iou
s
Are
a (
sf)
Cu
rve
Nu
mb
er
(CN
) U
sed
HS
G D
-
Op
en
Sp
ace A
rea
(acre
)
HS
G D
-
Op
en
Sp
ace A
rea
(sf)
Cu
rve N
um
ber
(CN
) U
sed
Avg
. C
urv
e
Nu
mb
er
To
tal A
rea
(acre
s)
To
tal A
rea
(SF
)
TC
(M
in.)
DA
-1 D
eta
ined
0.4
318,8
27
98
0.0
0.0
80
98
0.4
318,8
27
10
0.4
318,8
27
UR
TIL
BH
SG
DS
oil
Urb
an L
and, till
substr
atu
m 0
to 8
perc
ent slo
pes
Descri
pti
on
Imperv
ious S
urf
ace
98
Open S
pace (
law
n)
(good)
80
Per
County
Soil
Surv
ey -
Ru
no
ff C
urv
e N
um
ber
(CN
)
(HS
G D
)
EXISTING & PROPOSED HYDROGRAPHS FOR
2YR, 10YR & 100YR DESIGN STORMS
(HYDROGRAPHS CREATED USING HYDROFLOW
2007 BY INTELISOLVE COMPUTER SOFTWARE)
DRAINAGE AREA MAPS
