20001195 Ver 4_Approval Letter_20070322

e~,~
NCDENR
North Carolina Department of Environment and Natural Resources
Division of Water Quality
Michael F. Easley, Governor William G. Ross, Jr., Secretary
Alan W. Klimek, P.E., Director
March 22, 2007
DWQ Project # EXP 06-1195v4
Mecklenburg County
Charlotte Douglas International Airport
Attn: Mr. Jerry Orr, Airport Director
P.O. Box 19066
Charlotte, NC 28219
Subject Property: Charlotte-Douglas International Airport, 3~d Parallel Runway,Taxiway
and Wallace Neel Road Relocation
APPROVAL OF STORM WATER MANAGEMENT PLAN
Dear Mr. Orr:
The Division of Water Quality (DWQ) has reviewed the Storm Water Management Plan dated March 15,
2007 (received March 19, 2007) prepared by your engineer, Mr. Patrick E. Turney, P.E. of Talbert and
Bright, Inc. This plan has been approved the DWQ and satisfies the stormwater conditions required by
the Modification to the Individual Water Quality Certification issued on March 1, 2007.
You are required to meet the following conditions:
1. DWQ considers the Vortechs system and the vacuum truck to be non-approved stormwater Best
Management Practices (BMPs).
a. Charlotte-Douglas International Airport will be responsible for conducting monitoring
according to recognized protocols (see attached). Similar monitoring will be required to
evaluate the effectiveness of the vacuum truck.
b. You must submit monitoring reports to both the NCDENR-DWQ Stormwater and
General Permits Unit (as described in Item 6.£) as well as to the DWQ Express Review
Program at the letterhead address).
2. The storm water treatment system consisting of the weekly vacuum truck, Vortechs units, grass
swales, grass filter strips, and extended dry detention basins, and the signed and notarized
Operation and Maintenance Agreement, as approved by this Office, and the drainage patterns
depicted on the plan sheets, must be maintained in perpetuity.
a. In the event that this stormwater treatment system does not provide the total suspended
sediment (minimum 85% TSS) and nutrient removal capabilities as described in the
March 15, 2007 stormwater management plans submitted and approved by DWQ,
Charlotte-Douglas International Airport will be required to re-submit a stormwater
management plan for re-approval by DWQ. This may include, but is not limited to,
retrofitting sand filter(s) and/or bioretention cells in order to treat the stormwater runoff
from the 3`d Parallel Runway, Taxiway, Wallace Neel Road project.
b. No changes to the structural stormwater practices shall be made without written
authorization from the Division of Water Quality. The stormwater easements shall allow
for the ability to maintain the structures, perform corrective actions, and shall provide
401 Wetlands Certification Unit
1650 Mail Service Center, Raleigh, North Carolina 27699-1650 One
2321 Crabtree Boulevard, Suite 250, Raleigh, North Carolina 27604 NorthCaTOlina
Phone: [phone] FAX [phone] / Internet: http://h2o.enr.state.nc.us/ncwetlands ~~~~~~~/~
An Equal OpportunitylAffirmativeAaion Employer - 50% Recycled110% Post Consumer Paper `

Charlotte-Douglas International Airport, 3`d Runway Stormwater Management Plans
DWQ Project No. 06-1195v4
Page 2 of 2
March 22, 2007
protection of the structures from potential alternations by future property owners or
managers.
3. The applicant and/or authorized agent shall contact the DWQ Express Review Program in writing
at the letterhead address within ten (10) days of the commencement of construction.
This letter completes the review of the Division of Water Quality under Section 401 of the Clean Water
Act. If you have any questions, please contact Cyndi Karoly at 919.733.9721 or Cynthia Van Der Wiele,
Ph.D. at 919.715.3473.
Sincerely,
~~' - ~--,
Cyndi Bell Karoly, Program Manager
401 Oversight, Express Review Program
CBK/cvdw
Attachments: NCDENR Memorandum describing device and protocol with Attachments 1 - 5.
cc: USACE Asheville Regulatory Field Office
DWQ Mooresville Regional Office
Bradley Bennett, DWQ Stormwater Permitting Unit
Ken Pickle, DWQ Stormwater Permitting Unit
Annette Lucas, 401 Oversite Unit
File Copy
Central Files
Patrick E. Turney, P.E., Talbert & Bright, 4944 Parkway Plaza Blvd., Suite 350, Charlotte, NC
28217
Ronald E. Geiger, P.E., HDR, 128 South Tryon St., Suite 1400, Charlotte, NC 28202-5004
Joseph G. Battiata, P.E., Regional Regulatory Manager, 8005-C Creighton Parkway, Suite 711,
Mechanicsville, VA 23111

State of North Carolina
Department of Environment
and Natural Resources
Division of Water Quality
Michael F. Easley, Governor
William G. Ross, Jr., Secretary
Kerr T. Stevens, Director
1 • •
NORTH CAROLINA DEPARTMENT OF
ENVIRONMENT AND NATURAL RESOURCES
DRAFT
MEMORANDUM
TO: Regional Office Water Quality Supervisors
Branch Heads
FROM: Kerr T. Stevens
SUBJECT: Preliminary Evaluation Period for Vortechs Stormwater Treatment System
Technology
cc w/attach: Coleen Sullins
Bradley Bennett
Steve Zoufaly
Steve Giffin, Stormwater Management
Vortechs System Technology
The Vortechs System is essentially an on/grit separator designed to remove and retain sand,
hydrocarbon-laden sediment, metals, petroleum-based liquids and other floating debris from
stormwater runoff. A typical design for a Vortechs System uses four chambers which are a
circular grit chamber, an oil chamber (which includes the grit chamber), a flow control chamber,
and an outlet chamber. These chambers are encased in a precast concrete subsurface box with
appropriate manhole covers. (See Attachment 1)
The tangential inlet to the trap's circular oil and grit chamber channels stormwater into avortex-
like flow path. This swirling action directs sediment into the center where it accumulates in a
stable pile. The submerged oil barrier then traps oily contaminants floating in the grit chamber.
The center barrier traps floatables in the oil chamber. As the storm event builds in intensity the
capacity of the internal low flow control is exceeded, submerging the inlet and thus preventing
stormwater from impinging on previously captured floatables. The Vortechs System is designed
to keep captured pollutants in the trap by abating forces that encourage resuspension and
washout.
To facilitate maintenance, treated water drains out of the trap after the rain subsides, exposing
accumulated sediment and captured floatables for inspection. The volume of water remaining in
the trap is as much as 80% less than with conventional oil and grit separators -which means
fewer gallons to dispose of and lower clean-out costs.
1617 Mail Service Center, Raleigh, North Carolina 27699-1617 Telephone [phone] FAX [phone]
An Equal Opportunity Affirmative Action Employer 50% recycled/ 10% post-consumer paper

Bench scale tests of the system indicate removal rates of more than 80% TSS during typical
monthly rainfall activity. It is also reported that over 80% of sediment is removed during the
"first flush".
Each system is custom-designed by Vortechnics engineers using local precipitation data to ensure
optimum performance during the full range of storm events.
Annlication of the Vortechs System in Other States
Providence, Rhode Island - A Vortechs System was installed at the intersection of Routes 6/10
and I-95 in downtown Providence. During the passage of Hurricane Floyd in September 1999,
over 5 inches of rain fell in two days at intensities up to 2 inches per hour. On a volume basis,
this storm was ranked as a 25-year event. Upon inspection of the Vortechs System a few days
after the rainfall, 6 inches of sediment and a significant amount of floating debris had been
captured. Watermarks within the Vortechs System revealed that all flows were treated at less
than half the peak flow capacity of the system. The system demonstrated it's ability to retain
contamination during intense storm activity.
Town of Seabrook, NH -During the spring rainy season, silted-up catch basins and high tides
often led to surface flooding which sometimes took days to subside and kept owners from getting
to their homes. The Town of Seabrook authorized the installation of two Vortechs Systems, each
designed to treat 8000 gpm during peak flow conditions.
Warwick, Rhode Island -Expansion of the local airport included the addition of a 1000-space
parking lot. Runoff from this impervious surface discharges to freshwater wetlands that became
subject to Rhode Island state stormwater quality criteria. The parking lot area is approximately 7
acres and produces a 2-year design storm flow rate of 17.7 cubic feet per second. The original
drainage plans called for the installation of five stormwater treatment tanks placed throughout the
area. After further consideration, it was decided that one Vortechs System could replace the five
smaller tanks at a substantial cost savings.
State of Connecticut -The Vortechs System has been ~approved for use in Connecticut
Department of Transportation projects. Personnel contacted at the Department of Transportation
indicated that the Vortechs System has operated as designed and has experienced no maintenance
problems. Although no specific removal efficiencies were available at the time of the
conversation, the contacted personnel stated that TSS removal efficiencies of 85% had been
achieved.
State of Mississippi - Personnel at the Mississippi Department of Environmental Quality were
contacted to discuss past performance of the Vortechs System as permitted in the state.
Contacted personnel stated that the Vortechs System has operated according to design and has
presented no operation or maintenance problems. Although no specific removal efficiencies
could be recalled by the contacted personnel, they stated that TSS removal efficiencies of 85%
had been achieved.

The Vortechs Stormwater Treatment System has been installed in numerous states including
Connecticut, Massachusetts, Maine, Ohio, New York, Kansas, Mississippi, Michigan and Rhode
Island.
Product Studies
Data published by Vortechnics, based on bench-scale testing, indicate that the Vortechs System
can achieve up to 30% removal of silty sediment and up to 54% removal of the medium-to-
coarse sand fraction at their recommended peak loading rates (e.g. 10-year or 25-year storms)
when designed according to recommended sizing criteria. Vortechnics also claims that removals
on the order of 90% are achieved in 2-month storms. A 2-month storm, according to
Vortechnics, represents a "90`h percentile" level of rainfall intensity. This assumption means that
90% of all rainfall falls at an intensity that is less than the so called 2-month. Removal of other
pollutants is not documented by their literature at this time. Long-term performance needs to be
studied, to determine whether resuspension of accumulated sediments occurs over time, although
Vortechnics reports that this problem has been overcome by the Vortechs System as evidenced
by systems that have been closely monitored for up to 3 years.
Laboratory tests conducted by Vortechnics, Inc. indicate that a TSS removal efficiency of 85%
can be maintained for operating rates of approximately 22 gpm/sgft using a particle size
gradation characterized in the National Urban Runoff Program. For a particle size of 150
microns, the 85% TSS removal efficiency can be maintained up to an operating rate of
approximately 55 gpm/sgft.
DeLorme Publishing Company, Yarmouth, Maine - A Vortechs System was installed at the
subject site to treat stormwater runoff from a 300-car, 4 acre parking area that combines with
discharge from a nearby interstate highway. Following the Vortechs System in the treatment
train are vegetated detention ponds and swales. Vortechnics conducted atwo-month `trial run'
monitoring period at the end of 1998, without the benefit of a flow meter. The `trial run'
monitoring consisted of the collection of influent grab samples to determine TSS removal
efficiency. Preliminary in-field data from this trial run showed an 84% removal of TSS by the
system. Sediment accumulation data illustrated the ability of the system to trap and retain fine-
grained sediments throughout all rainfall intensities, including two 100-year storms. Preliminary
monitoring was suspended in December 1998 at the request of the responsible party to
accommodate winter snow removal operations. Monitoring with automatic grab samplers and a
flow meter resumed in May 1999. Seven months of the monitoring program have been
completed, spanning 20 storms from May to November 1999. The net removal efficiency for
the 20-storm, 7-month period was approximately 80% TSS.
The University of Connecticut is currently studying and monitoring the Vortechs System's
performance. The results are tentatively scheduled to be released in Fa112002.
Design Criteria and Site Application
Vortechs Systems have been designed for a variety of residential, commercial and municipal
applications. Typical treatment capacities range from 3 to 21 cfs. Various models are available

with grit chamber diameters ranging from 4-10 feet, sediment storage ranging from 1.5-10 cubic
yards, and total volume ranging from 2100 to 11,100 gallons.
Vortechs Systems incorporate anenergy-dissipating swirl concentrator and engineered flow
controls to ensure that contaminants captured during routine storm activity are not washed out
during peak flow periods. In order to achieve an overall removal efficiency of 80% TSS for a
wide range of flow rates, Vortechs Systems must be sized so that during the 2-month storm the
flow rate through the system does not exceed 24 gpm/sq.ft. of grit chamber surface area.
The two principal design criteria for the Vortechs System are:
1. The 2-month flow rate: The 2-month storm operating rate is preferably about 15
gpm per square foot of grit chamber surface area and never more than 24 gpm/sf. The
2-month flow rate will cause the water level in a Vortechs System to rise to a level
sufficient to submerge the inlet pipe thereby reducing inflow velocity to less than one
foot per second and minimizing turbulence.
2. The peak flow rate: The peak design storm (typically the 10-year or 25-year storm)
operating rate is preferably 100 gpm/sf.
Since 2-month storm rainfall data is not as widely available as data for more sever storms, the
peak design storm may be used for preliminary sizing. This usually causes the 2-month storm
operating rate to fall within the desired range. The manufacturer, Vortechnics, should provide
design and engineering services for the Vortechs system.
In Vortechs installations where the risk of large oil or fuel spills is small, the liquid contaminants
will not accumulate as quickly as the sediments. Vortechs Systems can be designed to trap
catastrophic spill events, but are more commonly configured with sump depths of 2-4 feet -
providing for oil storage of one to three feet.
Typically, this system would be installed close to the source, before pollutants are conveyed to
storm sewers or as pretreatment for other BMPs. The Vortechs System is acceptable for use in
areas with high traffic or high potential for petroleum accumulations such as parking lots, gas
stations, roads and large impervious areas.
Manufacturers sizing and installation guidelines should be followed. In order to achieve a net
annual TSS removal efficiency of 85%, Vortechs Systems must be sized appropriately. A design
ratio is determined by dividing the peak operating rate of a Vortechs System (based on the peak
runoff rate of the design storm) by the peak intensity of the design storm. The design ratio
should be less than or equal to 20 in order to achieve the 85% TSS removal rate. The adequate
grit chamber area is then determined by dividing the peak flow rate from a design storm by the
peak intensity of the design storm multiplied by the design ratio. Attachment 2 demonstrates the
sizing criteria for achieving the 85%TSS removal efficiency.
A general sizing chart is provided by Vortechnics. The chart lists models and flow rates for
various Vortechs Systems (See Attachment 3). Once the model size has been determined, the
user completes the Specifier's Worksheet to provide details regarding site and application data
(See Attachment 4). This data sheet should be submitted with all permit applications.

Maintenance
Routine inspections of the Vortechs system are necessary to schedule cleanings when the unit is
full. In the first year of operation, the Vortechs System should be inspected monthly for the first
six months and quarterly for the remainder of the year. During quarterly monitoring periods, a
monthly inspection should also be performed if a heavy contaminant loading event occurs (e.g.
winter sandings, soil disturbances or oil/fuel spills). The system should be inspected following all
major storm events (> 1 inch). Following the first year, the inspection schedule can be modified
in according to experience or to meet specific stormwater permit requirements.
Inspections shall include a visual observation of sediment accumulation, confirmation that the
system appears to be operating properly, and removal of any accumulated trash, vegetation or
debris. Sediment accumulation is most easily determined by slowly lowering a measuring stick
into the center of the grit chamber until it contacts the top of the pile. The system is full and
should be cleaned out when the top of the pile is approximately one foot below the dry weather
water level. The dry weather water level is the level at which water is retained in the unit and
will not flow out, over the lowest weir plate.
Clean-out of the Vortechs System with a vacuum truck is generally the best and most convenient
method. Only the manhole cover above the grit chamber needs to be opened to remove water
and contaminants. As the grit chamber is pumped out, the oil and water drain back into it, so that
oil scum, particulates and floatables are removed along with accumulated sediments. With the
Vortechs System, a pocket of water between the grit chamber and flow controls seals the bottom
of the oil barrier and prevents the loss of floatables to the outlet during cleanings. Manhole
covers should be securely seated following cleaning activities to ensure surface runoff does not
leak into unit from above.
The accumulated sediment removed from the system must be disposed of properly. Both liquid
and solid waste should be disposed of in a manner that prevents potential impacts to surface
water and groundwater.
Preliminary Evaluation Period Requirements
Based upon the information contained herein and the best professional judgement of Division
staff, the following requirements shall be maintained for all Vortechs System installations during
this Preliminary Evaluation Period.
1. The assumed average annual TSS removal efficiency for the Vortechs System (with
pretreatment, if necessary) shall be 85%. Appropriate pretreatment shall be determined on
a case-by-case basis.
2. All approved systems shall be designed and sized in accordance with the manufacturers
specifications.

3. No Vortechs System shall be permitted in areas draining to ORW, HQW, WS-II or SA
waters.
4. The Director shall sign all permits issued during the Preliminary Evaluation Period.
5. A copy of all application and supporting documentation shall be provided to the
Stormwater and General Permits Unit for incorporation into a database and for use in
overall evaluation of the technology.
6. Analytical Monitoring
a. The applicant shall submit a monitoring plan for approval and incorporation
by reference as an enforceable part of the permit. Particular attention should
be paid to the accuracy of proposed flow monitoring, effect of any bypass on
monitoring results, type of composite sampling specified, and the parties
responsible for implementing the plan.
b. All permits shall require quarterly analytical monitoring of both the influent
and effluent and concurrent documentation of a system inspection. Samples
shall consist of a grab sample of the first flush (within the first 15 minutes of
discharge from the unit) and flow-paced composite samples collected, at a
minimum, over the first three hours of the event. Samples must be collected
in each of the four seasons. Monitoring parameters shall, at a minimum,
include:
• Total Suspended Solids
• Oil and Grease
• TKN
• Ammonia Nitrogen (NH3)
• Nitrate-nitrite
• Total Phosphorus
• Total Coliform ~.
• Fecal Coliform
• Enterococcus
• Flow
Additional monitoring parameters shall be included on a case-by-case basis to
address water quality issues within the project area.
c. Storm event date, total rainfall and duration must be recorded for both the
storm event prior to the sampled event and the sampled event.
d. All samples shall be collected from a representative storm event. A
representative storm event is an event that measures greater than 0.1 inches of
rainfall and that is preceded by at least 72 hours during which no storm event
measuring greater than 0.1 inches has occurred. A single storm event may
contain up to 10 consecutive hours of no precipitation. For example, if it rains
for 2 hours without producing any collectible discharge, and then stops, a

sample may be collected if a rain producing a discharge begins again within
the next 10 hours.
e. The permittee shall be required to split samples with DWQ for at least one
event if the permit writer deems this necessary to verify the accuracy of
monitoring results. This is a case-by-case requirement based upon the
proposed analytical monitoring.
£ Within 30 days of receiving laboratory results monitoring data should be
submitted to:
NCDENR-DWQ
Stormwater and General Permits Unit
1617 Mail Service Center
Raleigh, NC 27699-1617
All submitted data shall reference the project name, location and permit number.
7. The permittee may petition to have monitoring requirements modified, reduced, or
eliminated after 10 valid data points have been submitted for each system. A facility may
opt to monitor more frequently than quarterly to generate 10 data points from 10 different
storm events as long as data is collected over the course of at least one full year with
samples collected in each season. Modifications shall be determined on a case-by-case
basis. Upon modification of monitoring requirements, the permit writer shall review
documented system inspections and maintenance activities and shall modify the permitted
inspection and maintenance schedule as appropriate.
All permits shall require that another treatment method be installed in the event that the
Vortechs System fails to substantially fulfill the state requirements it was permitted to
meet.
9. An executed Operation and Maintenance Agreement shall be required. Maintenance
requirements shall be in accordance with the following guidelines:
The Vortechs System should be inspected monthly for the first 6 months and quarterly
thereafter. The system should also be inspected after every major storm event (>1
inch and following any major sediment loading events (e.g. winter sandings, soil
disturbances or oil/fuel spills). Inspections shall include a visual observation of
sediment accumulation, confirmation that the system appears to be operating properly,
and removal of any accumulated trash, vegetation or debris.
The Vortechs System shall be inspected during a representative storm event at least
once per year to verify the system is operating properly.
• A system inspection shall be performed concurrently with each monitoring event.
• All inspections and maintenance activities shall be documented using a standardized
form which is used for each visit.

• Maintenance shall be performed in accordance with the manufacturers
recommendations unless otherwise specified in this PEP document.
• Sediment shall be removed, at a minimum, annually and when the top of the sediment
pile is approximately one foot below the dry weather water level of the system. The
depth of sediment can be measured without entry into the unit via a diptstick.
• Oil levels greater than 1.0 inch shall be removed immediately by a licensed waste
management firm. The oil accumulation can be determined using a conventional
dipstick tube.
• During each inspection or monitoring visit, any accumulated trash, vegetation or
debris should be removed and properly disposed of.
10. An annual report shall be submitted by March 1 of each year. The report shall document
the inspection, maintenance and monitoring activities performed during the previous
calendar year and summarize overall system performance. The annual report shall be
submitted to:
NCDENR-DWQ
Stormwater and General Permits Unit
1617 Mail Service Center
Raleigh, NC 27699-1617
Attachments:
Attachment 1 Vortechs System Design
Attachment 2 Sizing Criteria for 85% TSS Removal
Attachment 3 Sizing Chart
Attachment 4 Vortechs System Specifiers Worksheet
Attachment 5 Policy Memorandum: Permitting New Stormwater Treatment Technologies

ATTACHMENT 1

s
~:wc ConCentre:~r ~,ii 5arner ~•. _ r , ~3te5
`\
~~ •~
:~. __

~. • ••
\
I' •. ~
'
•
. •.
i:•: ~
~~:
;.. .: •.
I•
`_`'/ATiCN VIEW ~
F c.•. ;,ontroi
Gnt Oil FioW Control OuUe!
Chamber Chamber Chamber Chamber

t ~._o,
~ ~~
Seal-see 6" Concrete typical
note below

Seal with
30'
~
caulk inside
i and outside
1/4"Aluminum i L-10" 1'-9" t -9~

i ;
i o
I
.-. I
-~---~ - •- •-•-•- •- •- •-- + + o
---
- = , ~ i r
~ _
- _ -- ---

~

1 +
°
+
~ ~~ r
~ ~ „' 4" Conc.
~~~-
I /~ Typical
"
I a

O

`Q
1 c
v
__ --
30 - -
y, _

Centerlines of Inlet
and Aluminum Chamber
Opening to match. -
Manhole frame and
perforated cover.
Rim Elev. -]

Seal-see
Hole below
PLAN VIEW B - B
J
Manhole Irame and
perforated cover, (Typ. of ?1
Rim Elev.
6" Concrete reinforced for ~....d J~
r,-_0 loafing.- s-~=----- ~'
I
r :~
Seol~
~ 6
~ +o
i
I

Weir i
N
,
Seal with step ~ and
ifi
o! Butvl rubber ------J Or
ce
Plates O
i i
compound .

~' 0"
+ o
I i

-+
t
_'i
z i
~

~

+ ~ +
i +
i i
~
~

~ I

'a

~
1

'~
i ~ Caulk-see -
^ote above ~
~+

i n
SECTION A - ~'
STORMWATER TP,EATME~JT S'rSTEN1
VORTECHSTM MODEL # 9000 PATENT PENDING
SCALE: t/a' t'-0-
INV.

ATTACHMENT 2 ,

Sizing Criteria for 85% Net Annual TSS Removal Efficiency
In order to achieve a net annual Total Suspended Solids (TSS) removal efficiency of 85%
for the Mid-Atlantic Seaboazd, Vortechs Systems must be sized so that the design ratio is
less than or equal to 20.
Design Ratio = ~Rd ;20
d
Where
ORd =Peak operating rate of a Vortechs System on your site based on the peak runoff
rate from your design storm (gpm/ftZ)
Id =Peak intensity of design storm (in/hr)
This design ratio is multiplied by various rainfall intensities to get a Vortechs System
operating rate at that intensity. Based on historical rainfall records, eve calculate the
percentage of rainfall in an average year that falls at each intensity. ~~'e multiply that
percentage by the TSS removal efficiency at the corresponding operating rate, resulting
in a relative TSS removal efficiency. The sum of the relative removal efficiencies for
each intensity is the net average annual TSS removal efficiency. A tti-pical net annual
TSS removal efficiency calculation sheet is attached.
~, !•~,1
In order to select the proper size Vortechs System for your site use•the followins ,
equation, which will yield a design ratio less than or equal to 20. < "' V ~'
C ~ ~~~ ^~IJ• • j\
Where '` _ ,;;~~.
A =Minimum Grit chamber area (ft') ~-~.~,~"~"'
O =Peak flow rate from your design storm (cfs)
C = 450 gpm/ft3 -Conversion factor _,
1 =Peak intensity from your design storm (in/hr)
For example, a 10 year design storm might produce a peak intensity of 5"/hr and a peak
runoff rate of 10 cfs on a 1 acre site. Using the preceding equation we would find that a
Vortechs Model 7000 would be appropriate.
10 j-~ * 450 g•5
A = f ~,~n• j~' = 45 ft'
S h~ * 20 g'''r
min• jr' •in
From the chart on the specifying page of the Vortechs System Brochure we see that the
Mode17000 has a grit chamber area of 50 ft` and therefore would be accurately sized.

~ortechnicsTM
-~ Engineered Products
FOR STDRMWATER TREATMENT
~_
~~'
VORTECHST"" SYSTEM NET ANNUAL TSS REMOVAL EFFICIENCY
Parking Lot Construction
_ Anytown, USA
Model 5000
S stem No. 1
Design Ratio' = 100 gpm/sf 15 in/hr = 20.0
Rainfall Intensity Operating Rate % Total Rainfall Rmvl. Effcv R el
Effcv
"/0.25 hr "Ihr g m/sf Volume' (%) .
(%)
0.02 0.08 1.6 35.8% 92.0% 32.9%
0.04 0.16 3.2 19.5% 92.0% 18.0%
0.06 0.24 4.8 10.2% . 92.0% 9.4%
0.08 0.32 6.4 6.5% 91.2% 5.9%
0.10 0.40 8.0 4.6% S3.3°o 4.0°0
0.12 0.48 9.6 3.0% 87.1% 2.6%
0.14 0.56 11.2 1.8% 84.0% 1.5%
0.16 0.64 12.8 2.3% 82.2% 1.9%
O.1S 0.72 14.4 1.6% 79.1°0 1.3%
0.20 0.80 16.0 1.3% 7~.8% I.0%
0.22 0.88 17.6 1.4% 74.0% 1'.0%
0.24 0.96 19.2 0.7% 70.9% 0.~°0
0.26 1.04 20.8 1.1% 69.7% 0.8%
0.28 1.12 22.4 0.9% 67.0% 0.6%
0.30 1.20 24.0 1.1% 64?% 0.7°/a
0.3~ 1.40 23.0 1.2% ~9.~% ~ 0.7°'0
0.40 1.60 32.0 1.0% ~~.0%. 0.5%
0.4~ 1.30 36.0 0.3% X0.7°.0 0.4%
0.~~ 2.20 44.0 1.4% 41.1% 0.6%
0.6~ 2.60 2.0 1.8°0 31.0% 0.5%
Subtotal 84,8%
rain falling at >2.6"/hr
Assumed Removal Efficienc}• of remaining %
Cumulative Removal Efficiency = 2.3%
0.0%
85% _
1 -The Design Ratio is the Design Flow Rate divided by the area of the grit chamber divided by the intensity.
- The Design Flow Rate is specified by the site engineer.
- The intensity is derived from the Rational Method: Q=CIA where:
Q = Design Flow Rate (cfs)
C = Runoff coefficient = 1 for impervious surfaces
I = Average rainfall intensity ("/hr)
A =Drainage area (acres)
2 -Operating Rate (gpm/sf =intensity ("/hr) x Design Ratio
3 -Based on 11 years of 15-minute rainfall data from NCDC Station 1995 in College Park, MD.
4 -Based on Vorteehnics laboratory verified removal of 50 micron arricles (see Technical Bulletin #1)
Calculated bv: VPA 4/10/2000 Checked bv: 4/10/2000
f:\data\vortechn\projectsUcxxinp.xls AP 4/10/2000

ATTACHMENT 3

`~~~rt~~•h~T" i
`lui{rl Crit
Chainl~~•-•
Dian~t~t~•r I
I••1,~~~•
~ I~ut~~
Tr>t<<I
~~~liini~~
' ~,•,lin~,~nt
~t„ra,_,~
(:l,•aii Opit
1„I~in-,•
. ' .` 2000 4 3.U/1.3UU '?. l UU 1.."~ :,r,n ~

:.`~:, -.3000 S 4.5/?.000 '?.~~UU '?.0 ~~~~~ ~

''"4000 f~ 6.0/2.800 3.i;00 3.O ~)UI) i

~• = 5000 r 8.5/3,800 -1.8Ut) ~.U. I . l i~i-

~ ~;~~~ ~ 7000 8 11.0/~.yUU ~ .~UU t>.i~ I. (ut~ j
" ~_. 9000 9 1=1.0/0,300 0.100 K.~) l .~;i~~-
~.r-11000 10 17.0/~,h00 11.100 IU.U .'.l~-i)

ATTACHMENT 4

U ? O (ND O
~, c ~ cp ire
-pvchco
to Z~com
_ ~ ~ ~ X
Q Q
W j Z N LL
W J v
O v o
a
W W
H ~
~ ~
>" Y
~ O
N
U to
w a
~ w
~ U
"~ W
d.
.~ ~~
~_
C N
a v
E' v`
U
~ X
~. LL
V) F .
C
O
.~
J
U
61
~O
a`
Z
F-
Z
0
U
Q
w
H
a
N
'$
N.
N
C
f0
ra
c .
0
U
7
Q'
c
E
N
J
c
m
0
a
U
N
O
C
N
v
C
>?'
c
0
(~
m
0
m
O1
d
N
U
d
pa m
U
d ~
~ y
a

~i
m
m
d
Q d ~
y V O
a ~
F

O

a~

v O

t m c
7 F p
N

.~ > U N
N
~ $ L
p Q U

v
m'
a
C
c
0.
c
o
N
W
E

U
d
v 2

p m m
~ c
-
w c
m
c
rn
.y ~
0

N
d
a

v
.o
p ,'m
N~ p
O

~'. ~
a ~
~ a,
c
m
Nom
d Z N ~
v m
~ ~ U
~
p
ri d
a
.
N ~ 01
F `'' P'1
Z
O
Q
U
LL
U
W
a
0
Z
Q
W
F-
z
d
W
Z
O
Y
U
W
2
.~
a~
w
c
_I
a~
N
0
U
C
W
C
Ia
d
d

N
~~.
O
Z
Ul
~+
.~.
m
O