20110081 Ver 1_More Info Received_20110706

HensonFoley
Landscape Architecture 1 Civil Engineering
10224 Hickorywood Hill Avenue, Suite 101 A
Huntersville, North Carolina 28078
704-875-1615 ph. 704-875-0959 fx.
Letter of Transmittal
11- 0081
To:NCDENR/NCDWQ Date: 7-6-11 Job #: 2933
Attn: Annette Lucas, P.E. Phone: [phone]
Dept: Re: Boone Dollar General
Address: 512 N. Salisbury Street
Raleigh, NC 27604
We are sending you: X Attached _ Under separate cover via
_ Shop drawings _ Prints _ Plans _ Samples
_ Copy of letter _ Change Order _
_ Specifications
Copies Pages Description
1 14 Sets of plan
1 Calculation book
1 Operation and Maintenance Manual

These are transmitted as checked below:
_ For approval
_ For your use
_ As requested
For review and comment
Remarks:
[2@2U l:J R
JUL062011
DENR - WA7 R AL
_ Approved as submitted -Resubmit copies for approval
_ Approved as noted _ Submit copies for distribution
_ Returned for corrections _ Return corrected prints
Signed: v?
rim Foley
StormFilter Inspection and
Maintenance Procedures
I ht. m""TAAv rr %l4 war ^
StorrnFilter
Maintenance Guidelines
The primary purpose of the Stormwater Management
StormFilter' is to filter out and prevent pollutants from entering
our waterways. Like any effective filtration system, periodically
these pollutants must be removed to restore the StormFilter to its
full efficiency and effectiveness.
Maintenance requirements and frequency are dependent on the
pollutant load characteristics of each site. Maintenance activities
may be required in the event of a chemical spill or due to
excessive sediment loading from site erosion or extreme storms. It
is a good practice to inspect the system after major storm events.
Maintenance Procedures
Although there are likely many effective maintenance
options, we believe the following procedure is efficient and
can be implemented using common equipment and existing
maintenance protocols. A two step procedure is recommended
as follows:
1. Inspection
Inspection of the vault interior to determine the need for
maintenance.
2. Maintenance
Cartridge replacement
Sediment removal
Inspection and Maintenance Timing
At least one scheduled inspection should take place per year with
maintenance following as warranted.
First, an inspection should be done before the winter season.
During the inspection the need for maintenance should be
determined and, if disposal during maintenance will be required,
samples of the accumulated sediments and media should be
obtained.
In addition to these two activities, it is important to check
the condition of the StormFilter unit after major storms for
potential damage caused by high flows and for high sediment
accumulation that may be caused by localized erosion in the
drainage area. It may be necessary to adjust the inspection/
maintenance schedule depending on the actual operating
conditions encountered by the system. In general, inspection
activities can be conducted at any time, and maintenance should
occur, if warranted, in late summer to early fall when flows into
the system are not likely to be present.
Maintenance Frequency
The primary factor controlling timing of maintenance of the
StormFilter is sediment loading.
A properly functioning system will remove solids from water by
trapping particulates in the porous structure of the filter media
inside the cartridges. The flow through the system will naturally
decrease as more and more particulates are trapped. Eventually
the flow through the cartridges will be low enough to require
replacement. It may be possible to extend the usable span of the
cartridges by removing sediment from upstream trapping devices
on a routine as-needed basis in order to prevent material from
being re-suspended and discharged to the StormFilter treatment
system.
Site conditions greatly influence maintenance requirements.
StormFilter units located in areas with erosion or active
construction may need to be inspected and maintained more
often than those with fully stabilized surface conditions.
The maintenance frequency may be adjusted as additional
monitoring information becomes available during the inspection
program. Areas that develop known problems should be
inspected more frequently than areas that demonstrate no
problems, particularly after major storms. Ultimately, inspection
and maintenance activities should be scheduled based on the
historic records and characteristics of an individual StormFilter
system or site. It is recommended that the site owner develop
a database to properly manage StormFilter inspection and
maintenance programs.
Prior to the development of the maintenance database, the
following maintenance frequencies should be followed:
Inspection
One time per year
After major storms
Maintenance
As needed, based on results of inspection (The average
maintenance lifecycle is approximately 1-3 years)
Per Regulatory requirement
In the event of a chemical spill
Frequencies should be updated as required. The recommended
initial frequency for inspection is one time per year. StormFilter
units should be inspected after major storms.
Second, if warranted, a maintenance (replacement of the filter
cartridges and removal of accumulated sediments) should be
performed during periods of dry weather.
Sediment removal and cartridge replacement on an as needed
basis is recommended unless site conditions warrant.
Once an understanding of site characteristics has been
established, maintenance may not be needed for one to three
years, but inspection is warranted and recommended annually.
Inspection Procedures
The primary goal of an inspection is to assess the condition of
the cartridges relative to the level of visual sediment loading as
it relates to decreased treatment capacity. It may be desirable to
conduct this inspection during a storm to observe the relative
flow through the filter cartridges. If the submerged cartridges
are severely plugged, then typically large amounts of sediments
will be present and very little flow will be discharged from the
drainage pipes. If this is the case, then maintenance is warranted
and the cartridges need to be replaced.
Warning: In the case of a spill, the worker should abort
inspection activities until the proper guidance is obtained.
Notify the local hazard control agency and CONTECH
Stormwater Solutions immediately.
To conduct an inspection:
Important: Inspection should be performed by a person who
is familiar with the operation and configuration of the
StormFilter treatment unit.
1. If applicable, set up safety equipment to protect and notify
surrounding vehicle and pedestrian traffic.
2. Visually inspect the external condition of the unit and take
notes concerning defects/problems.
4. Without entering the vault, visually inspect the inside of the
unit, and note accumulations of liquids and solids.
5. Be sure to record the level of sediment build-up on the floor of
the vault, in the forebay, and on top of the cartridges. If flow
is occurring, note the flow of water per drainage pipe. Record
all observations. Digital pictures are valuable for historical
documentation.
6. Close and fasten the access portals.
7. Remove safety equipment.
8. If appropriate, make notes about the local drainage area
relative to ongoing construction, erosion problems, or high
loading of other materials to the system.
9. Discuss conditions that suggest maintenance and make
decision as to weather or not maintenance is needed.
Maintenance Decision Tree
The need for maintenance is typically based on results of the
inspection. The following Maintenance Decision Tree should be used as
a general guide. (Other factors, such as Regulatory Requirements, may
need to be considered)
a. If >4" of accumulated sediment, maintenance is
req u i red.
2. Sediment loading on top of the cartridge.
a. If > 1/4" of accumulation, maintenance is required.
3. Submerged cartridges.
a. If >4" of static water in the cartridge bay for more
that 24 hours after end of rain event, maintenance is
req u i red.
4. Plugged media.
a. If pore space between media granules is absent,
maintenance is required.
5. Bypass condition.
a. If inspection is conducted during an average rain fall
event and StormFilter remains in bypass condition
(water over the internal outlet baffle wall or submerged
cartridges), maintenance is required.
6. Hazardous material release.
a. If hazardous material release (automotive fluids or other)
is reported, maintenance is required.
7. Pronounced scum line.
a. If pronounced scum line (say >_ 1/4" thick) is present
above top cap, maintenance is required.
8. Calendar Lifecycle.
a. If system has not been maintained for 3 years
maintenance is required.
1. Sediment loading on the vault floor.
3. Open the access portals to the vault and allow the system vent.
Assumptions
• No rainfall for 24 hours or more
• No upstream detention (at least not draining into StormFilter)
• Structure is online
• Outlet pipe is clear of obstruction
• Construction bypass is plugged
Maintenance
Depending on the configuration of the particular system,
maintenance personnel will be required to enter the vault to
perform the maintenance.
Important: If vault entry is required, OSHA rules for confined
space entry must be followed.
Filter cartridge replacement should occur during dry weather.
It may be necessary to plug the filter inlet pipe if base flows is
occurring.
Replacement cartridges can be delivered to the site or customers
facility. Information concerning how to obtain the replacement
cartridges is available from CONTECH Stormwater Solutions.
Warning: In the case of a spill, the maintenance personnel
should abort maintenance activities until the proper
guidance is obtained. Notify the local hazard control
agency and CONTECH Stormwater Solutions immediately.
To conduct cartridge replacement and sediment removal
maintenance:
1. If applicable, set up safety equipment to protect maintenance
personnel and pedestrians from site hazards.
2. Visually inspect the external condition of the unit and take
notes concerning defects/problems.
3. Open the doors (access portals) to the vault and allow the
system to vent.
4. Without entering the vault, give the inside of the unit,
including components, a general condition inspection.
5. Make notes about the external and internal condition of
the vault. Give particular attention to recording the level of
sediment build-up on the floor of the vault, in the forebay,
and on top of the internal components.
6. Using appropriate equipment offload the replacement
cartridges (up to 150 lbs. each) and set aside.
7. Remove used cartridges from the vault using one of the
following methods:
Method 1:
A. This activity will require that maintenance personnel enter
the vault to remove the cartridges from the under drain
manifold and place them under the vault opening for
lifting (removal). Unscrew (counterclockwise rotations)
each filter cartridge from the underdrain connector.
Roll the loose cartridge, on edge, to a convenient spot
beneath the vault access.
Using appropriate hoisting equipment, attach a cable
from the boom, crane, or tripod to the loose cartridge.
Contact CONTECH Stormwater Solutions for suggested
attachment devices.
Important: Note that cartridges containing leaf media (CSF) do
not require unscrewing from their connectors. Take care
not to damage the manifold connectors. This connector
should remain installed in the manifold and could be
capped during the maintenance activity to prevent
sediments from entering the underdrain manifold.
B. Remove the used cartridges (up to 250 lbs. each) from the
vault.
Important: Care must be used to avoid damaging the
cartridges during removal and installation. The cost of
repairing components damaged during maintenance
will be the responsibility of the owner unless CONTECH
Stormwater Solutions performs the maintenance activities
and damage is not related to discharges to the system.
C. Set the used cartridge aside or load onto the hauling
truck.
D. Continue steps a through c until all cartridges have been
removed.
Method 2:
A. Enter the vault using appropriate confined space
protocols.
B. Unscrew the cartridge cap.
C. Remove the cartridge hood screws (3) hood and float.
D. At location under structure access, tip the cartridge on its
side.
Important: Note that cartridges containing media other than
the leaf media require unscrewing from their threaded
connectors. Take care not to damage the manifold
connectors. This connector should remain installed in the
manifold and capped if necessary.
D. Empty the cartridge onto the vault floor. Reassemble the
empty cartridge.
E. Set the empty, used cartridge aside or load onto the
hauling truck.
Continue steps a through e until all cartridges have been
removed.
8. Remove accumulated sediment from the floor of the
vault and from the forebay. This can most effectively be
accomplished by use of a vacuum truck.
9. Once the sediments are removed, assess the condition of the
vault and the condition of the connectors. The connectors
are short sections of 2-inch schedule 40 PVC, or threaded
schedule 80 PVC that should protrude about 1 " above the
floor of the vault. Lightly wash down the vault interior.
a. If desired, apply a light coating of FDA approved
silicon lube to the outside of the exposed portion of
the connectors. This ensures a watertight connection
between the cartridge and the drainage pipe.
b. Replace any damaged connectors.
10. Using the vacuum truck boom, crane, or tripod, lower and
install the new cartridges. Once again, take care not to
damage connections.
11. Close and fasten the door.
12. Remove safety equipment.
13. Finally, dispose of the accumulated materials in accordance
with applicable regulations. Make arrangements to return the
used empty cartridges to CONTECH Stormwater Solutions.
Related Maintenance Activities -
Performed on an as-needed basis
StormFilter units are often just one of many structures in a more
comprehensive stormwater drainage and treatment system.
In order for maintenance of the StormFilter to be successful, it
is imperative that all other components be properly maintained
The maintenance/repair of upstream facilities should be carried
out prior to StormFilter maintenance activities.
In addition to considering upstream facilities, it is also important
to correct any problems identified in the drainage area. Drainage
area concerns may include: erosion problems, heavy oil loading,
and discharges of inappropriate materials.
A RECYCLED
s`O PAPER
Material Disposal
The accumulated sediment found in stormwater treatment
and conveyance systems must be handled and disposed of in
accordance with regulatory protocols. It is possible for sediments
to contain measurable concentrations of heavy metals and
organic chemicals (such as pesticides and petroleum products).
Areas with the greatest potential for high pollutant loading
include industrial areas and heavily traveled roads.
Sediments and water must be disposed of in accordance with
all applicable waste disposal regulations. When scheduling
maintenance, consideration must be made for the disposal of
solid and liquid wastes. This typically requires coordination with
a local landfill for solid waste disposal. For liquid waste disposal
a number of options are available including a municipal vacuum
truck decant facility, local waste water treatment plant or on-site
treatment and discharge.
NATM
STQ9NEddNV NA
4Z ?.
800.925.5240
contechstormwater.com
Support
• Drawings and specifications are available at contechstormwater.com.
• Site-specific design support is available from our engineers.
©2007 CONTECH Stormwater Solutions
CONTECH Construction Products Inc. provides site solutions for the civil engineering industry. CONTECH's portfolio includes
bridges, drainage, sanitary sewer, stormwater and earth stabilization products. For information on other CONTECH division
offerings, visit contech-cpi.com or call 800.338.1122
Nothing in this catalog should be construed as an expressed warranty or an implied warranty of merchantability or fitness for
any particular purpose. See the CONTECH standard quotation or acknowledgement for applicable warranties and other terms
and conditions of sale.
Inspection Report
Date: Personnel:
Location: System Size:
System Type: Vault ? Cast-In-Place ? Linear Catch Basin El Manhole ? Other El
Date:
Sediment Thickness in Forebay:
Sediment Depth on Vault Floor:
Structural Damage:
Estimated Flow from Drainage Pipes (if available):
Cartridges Submerged: Yes ? No ? Depth of Standing Water:
StormFilter Maintenance Activities (check off if done and give description)
? Trash and Debris Removal:
? Minor Structural Repairs:
I-1 Drainage Area ReDort
Excessive Oil Loading: Yes ? No ? Source:
Sediment Accumulation on Pavement: Yes ? No ? Source:
Erosion of Landscaped Areas: Yes ? No ? Source:
Items Needing Further Work:
Owners should contact the local public works department and inquire about how the department disposes of their street waste
residuals.
Other Comments:
w???%u?ewu®
mho? %6V
STORMWATER
SOLUTIONSN.
Review the condition reports from the previous inspection visits.
Date: Personnel:
Location: System Size: _
System Type: Vault ? Cast-In-Place ?
List Safety Procedures and Equipment Used:
System Observations
Months in Service:
Oil in Forebay:
Sediment Depth in Forebay:
Sediment Depth on Vault Floor:
Structural Damage:
Drainage Area Report
Excessive Oil Loading:
Sediment Accumulation on Pavement
Erosion of Landscaped Areas:
Yes ? No ? Source:
Yes ? No ? Source:
Yes ? No ? Source:
StormFilter Cartridge Replacement Maintenance Activities
Remove Trash and Debris: Yes E] No ?
Replace Cartridges: Yes El No D
Sediment Removed: Yes ? No ?
Quantity of Sediment Removed (estimate?):
Minor Structural Repairs: Yes ? No ?
Residuals (debris, sediment) Disposal Methods:
Notes:
^aIAaU'*IEwu®
WVQ -4
STORMWATER
SOLUTIONSN?.
Linear Catch Basin ? Manhole ? Other ?
Yes ? No R
Details:
Details:
Details:
Details:
Storm Drainage, Water Quality and Erosion Control Calculations for:
Dollar General
Boone, NC
C
FES p ..
SEAL
23557
-ZA6(
1O F?GINE? ??
Prepared by:
HensonFoley
Landscape Architecture I Civil Engineering
10224 Hickorywood Hill Ave.
Suite IOIA
Huntersville, NC 28078
704-875-1615 ph
704-875-0959 fax
timghensonfoley.com
Project Description
The purpose of the project is to construct a Dollar General Retail Store and the associated
parking field. Approximately 1.2 acres will be disturbed during this construction period.
The site is 1.3 acres located in Boone, NC at the southwest corner of East King Street and
Forest Hills Drive.
Site Description
The site has hilly topography with slopes in excess of 30% in a few areas in the south east
portion of the site. There is a perennial stream located on the property. The owner has
contracted Wetland and Natural Resources, Inc. to evaluate the stream and to obtain
permits for disturbance associated with the driveway crossing and parking field. These
permits were obtained through US Army Corp and NCDWQ. This site will incorporate a
proprietary device by Contech Construction Products to achieve the 85% TSS Removal
required by NCDWQ permit. A letter from NCDENR representative is included for
information in regards to the state working with Contect on this product.
Soils
Please see soils report attached in the calculation book for soil summary.
Detention
The site was analyzed in context with the overall drainage basin that travels through the
pipe installed under King Street. The site is located at the most downstream portion of
the 24.5 acres drainage basin. When analyzing the site after the impervious cover is in
place the 10 year peak discharge decreases. The stormwater from the developed site
leaves the drainage basin before the stormwater from the rest of the drainage basin has
traveled to the pipe under King Street. Therefore no detention structure is in place.
There is strictly a water quality structure that will detain water for small storms and
release at such a slow rate for those storms the upper drainage area will be out of the
basin before they can combine. There are no calculations for peak flows for smaller
storms because Boone's ordinance currently is written to evaluate the 10 year storm.
Below you will find a summary for the 10 year storm calculations for the entire 24.5 acre
drainage basin.
10 year storm 10 year storm (Post
Predevelo ed Developed)
Entire 24.5 acre drainage 84.82 cfs 82.88 cfs
basin
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Hydrologic Soil Group-Watauga County, North Carolina
Hydrologic Soil Group
Hydrologic Soil Group- Summary by Map Unit - Watauga County, North Carolina
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
Puc Porters loam, 8 to 15 percent B 4.6 24.3%
slopes, stony
PuD Porters loam, 15 to 30 B 6.2 32.4%
percent slopes, stony
PuE Porters loam, 30 to 50 B 5.7 30.0%
percent slopes, stony
SnC Saunook loam, 8 to 15 B 2.3 12.3%
percent slopes
Ur Urban land 0.2 1.0%
Totals for Area of Inter est 19.1 100.0%
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive precipitation
from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly
wet. These consist mainly of deep, well drained to excessively drained sands or
gravelly sands. These soils have a high rate of water transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well drained
soils that have moderately fine texture to moderately coarse texture. These soils
have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of water
transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay layer
at or near the surface, and soils that are shallow over nearly impervious material.
These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in their
natural condition are in group D are assigned to dual classes.
USDA Natural Resources Web Soil Survey 5/4/2011
Conservation Service National Cooperative Soil Survey Page 3 of 4
. Hydrologic Soil Group-Watauga County, North Carolina
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff.- None Specified
Tie-break Rule: Lower
lJ? Natural Resources Web Soil Survey 5/4/2011
Conservation Service National Cooperative Soil Survey Page 4 of 4
Precipitation Frequency Data Server
NOAA Atlas 14, Volume 2, Version 3
Location name: Blowing Rock, North Carolina,
US*
Coordinates: 36.1414, -81.6709
Elevation: 3488ft* %m w ,?'
* source: Google Maps
POINT PRECIPITATION FREQUENCY ESTIMATES
G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley
NOAA, National Weather Service, Silver Spring, Maryland
PF tabular I PF graphical I Maps & aerials
PF tabular
Page 1 of 4
P DS-based point precipitation frequency estimates with 90% confidence intervals (in inches)'
Avera ge recurrence interval (years)
Duration ? 2 ? 10 25 50 100 200 500 1000
0.411 0.494 0.575 0.642 0.732 0.804 0.880 0.960 1.07 1.16
5-mIn (0.380-0.449) (0.457-0.539) (0.529-0.627) (0.588-0.700) (0.663-0.803) (0.719-0.887) (0.775-0.979) (0.830-1.08) (0.900-1.22) 1(0.957-1.35)
1
28 1
40 1
52 1
69
10-min 0.657 0.790 0.921 1.03 1.17 . . . . M
(1.51-2.13)
1
16 1
30 1
48 1
62 1
77 1
92 2
13 2
30
15-min 0.821 0.993 . . . . . . . .
(0.758-0.897) (0.918-1.08) (1.07-1.27) 1 1 (1.19-1.42) 1 1 (1.34-1.62) (1.45-1.79) (1.56-1.97) (1.66-2.16) (1.79-2.44) (1.89-2.67)
2
1 2
44 2
71 2
99 3
39 73
3
30-min 1.13 1.37 1.65 1.88 .
9 . . . . .
(1.04-1.23) (1.27-1.50) (1.52-1.81) (1.72-2.05) (1.98-2.40) (2.18-2.69) (2.38-3.01) (2.59-3.36) (2.85-3.88) (3.06-4.33)
92
2 3
31 73
3 4
19 4
86 44
5
60-min 1.40 1.72 2.12 2.45 . . . . . .
(1.30-1.53) (1.59-1.88) (1.95-2.31) (2.24-2.67) (2.64-3.20) (2.96-3.65) (3.28-4.15) (3.63-4.72) (4.09-5.56) (4.47-6.31)
2
60 03
3 3
66 4
20 4
79 5
46 48
6 7
40
2-hr 1.69 2.09 . . . . . . . .
(1.55-1.84) (1.91-2.27) (2.38-2.83) (2.76-3.29) (3.29-3.99) (3.72-4.61) (4.19-5.32) (4.68-6.13) (5.40-7.40) (6.03-8.57)
1
8 2
28 84
2 3
30 4
00 4
61 5
28 05
6 22
7 29
8
3-hr .
5 . . . . . . . . .
(1.70-2.02) (2.10-2.49) (2.60-3.10) (3.01-3.62) (3.60-4.41) 1 1 (4.09-5.11) (4.61-5.91) (5.18-6.85) (6.00-8.33) (6.72-9.70)
3
69 4
27 5
12 5
85 6
66 7
57 8
95 10
2
6-hr 2.44 3.00 . . . . . . . .
(2.26-2.65) (2.76-3.26) (3.39-4.02) (3.90-4.66) (4.63-5.63) (5.23-6.48) (5.86-7.45) (6.55-8.58) (7.53-10.3) (8.40-12.0)
3
24 3
96 4
85 5
53 6
49 7
28 8
13 9
06 10
4
12-hr . . . . . . . . .

-3.50)
(3.66-4.29)
(4.46-5.26)
(5.07-6.02)
(5.90-7.11)
(6.55-8.03)
(7.21-9.04) 1
1(7.92-10.2)
(8.93-11.9) (9.82-13.5)
3
79 4
59 5
86 6
90 8
41 9
68 11
1 12
6 7 F 7
14
8
7
16
F
24-hr . . . . . . . . . .
(3.48-4.13) (4.23-5.02) (5.39-6.40) (6.32-7.56) (7.63-9.22) (8.71-10.7) (9.84-12.3) (11.0-14.0) (12.7-16.7) (14.1-19.1)
4
56 5
51 7
00 23
8 10
0 11
6 13
3 15
1 17
9 2
0
2-day . . . . . . . . . .
4
( .21-4.96)
(5.10-6.00)
(6.46-7.63)
(7.56-8.98)
(9.14-11.0)
(10.4-12.7)
(11.8-14.7)
(13.2-16.8)
(15.3-20.2) )
(16.9
-23.2
4.88 5.89 7.42 8.68 10.5 12.0 13.7 15.5 18.2 20.5
3-day
(4.53-5.29)
(5.47-6.39)
(6.87-8.06)
(8.01-9.43)
(9.60-11.4)
(10.9-13.2)
(12.2-15.1)
(13.7-17.2)
(15.7-20.5) (
)
17.3-23.3
5.21 6.28 7.85 9.13 11.0 12.5 14.1 15.9 18.5 20.7
4-day (4.85-5.63) (5.84-6.79) (7.29-8.48) (8.45-9.88) (10.1-11.9) (11.4-13.6) (12.7-15.5)
(14.1-17.6)
(16.1-20.7) (
17.7-23.5)j
94
5 7
12 78
8 10
1 12.0 13.6 15.2 17.0 19.5
7-day .
-6.39) .
(6.67-7.65) .
(8.19-9.42) )
.
(9.41-10.9 (
)
11.1-13.0
(12.4-14.7)
(13.8-16.6) )
(15.2-16.7
(17.1-21.8) (18.7-24.4)
6
75 8
06 9
74 11
1 12
9 14
4 15
9 17.4 19.6 21.6
10-day .
(6.35-7.21) .
(7.57-8.59) .
(9.14-10.4) .
(10.4-11.8) .
(12.0-13.8) .
(13.2-15.4) .
(14.5-17.2) (15.8-19.0) (17.5-22.0) (19.0-24.6)
8.99 10.6 12.6 14.3 16.5 18.3 20.1 22.0 24.6 26.7
20-day (8.51-9.52) (10.1-11.3) (12.0-13.4) (13.5-15.1) (15.4-17.5) (17.0-19.5) (18.5-21.6) 1 1(20.1-23.8) (22.1-26.9) (23.7
-29.5)1
11
1 13
1 15
4 17
2 19
6 21.4 23.3 25.2 27.8 29.8
30-day .
(10.5-11.7) .
(12.4-13.9) .
(14.5-16.3) .
(16.1-18.2) .
(18.3-20.8) (19.9-22.8) (21.5-25.0) 1 1(23.1-27.2) (26.7-32.7)
13
9 16
3 18
8 20
8 23
5 25
5 27
5 29.6 32.3 34.4
45-day .
(13.2-14.7) .
(15.5-17.2) .
(17.8-19.9) .
(19.6-22.0) .
(22.0-24.8) .
(23.9-27.1) .
(25.6-29.4)
(27.3-31.7)
(29.5-35.0) )
-37.5
(31.1
16
6 19
4 22
2 24
3 27
1 29
3 31,4 33
4 36.0 38.0
60-day .
(15.7-17.4) .
(18.4-20.4) .
(21.1-23.3) .
(23.1-25.6) .
(25.7-28.6) .
(27.6-30.9)
(29.3-33.2) .
(31.1-35.6)
(33.3-38.7) )
(
34.9-41.2
Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS).
Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates (for a
given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are not
checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values.
Please refer to NOAA Atlas 14 document for more information.
Back to Top
PF graphical
http://hdsc.nws.noaa.gov/hdsc/pfdslpfds_printpage.html?lat=36.1414&lon=-81.6709&data=... 5/4/2011
Precipitation Frequency Data Server
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US Department of Commerce
National Oceanic and Atmospheric Administration
National Weather Service
Office of Hvdrolooic Development
1325 East West Highway
Silver Spring, MD 20910
YT1 421
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Page 3 of 4
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Precipitation Frequency Data Server
Questions?: HDSC.Questions(a)noaa.aov
Disclaimer
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HensonFoley
Landscape Architecture i Civil Engineering
Boone Dollar General INPUT
Watauga
EROSION CONTROL TRAP NO.
SEDIMENT TRAP CALCULATION DRAINAGE AREA
REF: N.C. EROSION AND SEDIMENT CONTROL DISTURBED AREA
PLANNING AND DESIGN MANUAL C
TIME OF CONC.
INTENSITY
1. TRAP NO. 1 ALLOW. WEIR DEPTH
WEIR LENGTH
2. DETERMINE RUNOFF FOR 10-YEAR STORM
DRAIN. AREA (AC.) 1.00 ACRES
DIST. AREA (AC.) 1.00 ACRES
C 0.5
TIME OF CONC. 5.00 MINUTES
INTENSITY (10 YR.) 7.26 IN./HR. FIG. 8.03(g) CHARLOTTE, NC
Q = CIA 3.6 C.F.S.
3. DETERMINE STORAGE CAPACITY REQUIRED:
3600 CF/AC x DIST. AREA = STORAGE VOLUME
STORAGE VOLUME = 3600
4. SIZE BASIN:
Surface Area = (Q 10 x 0.01) Acres = 0.04 Ac. = 1581.23 sf
Length = 2 x Width
WIDTH 28.1 FEET
LENGTH 56.2 FEET
DEPTH 2.28 FEET
VOLUME= 3600 CUBIC FEET
5. EMBANKMENT
DEPTH TO WEIR 3 FEET
DEPTH TO TOP OF EMBANKMENT 4 FEET
2:1 SIDE SLOPES
5' TOP WIDTH
6. SPILLWAY: FROM NC EROSION AND SEDIMENT CONTROL PLANNING
AND DESIGN MANUAL, TABLE 6.60A
WEIR LENGTH = 4 FEET
7. STONE SIZE: USE CLASS B EROSION CONTROL STONE WITH D50
EQUAL TO 9". PLACE NCDOT 457 STONE ONE FOOT THICK
ON THE FACE OF THE DAM.
8. FILTER CLOTH: PLACE EROSION CONTROL FILTER CLOTH BENEATH
DAM TO PREVENT PIPING.
1
1
0.5
5.00
7.26
3
4
Calculate Skimmer Size
Basin Volume in Cubic Feet
Days to Drain*
NC assume 3 days to drain
3,650 Cu.Ft
3 3 Days
Estimate Volume of Basin Length Width
Top of water surface in feet Feet
Bottom dimensions in feet Feet
Depth in feet Feet
Skimmer Size 1.5 Inch
Orifice Radius 0.6 Inch[es]
Orifice Diameter 1.3 Inch[es]
VOLUME 0 Cu. Ft.
Z N O
0
m (
O
W N W A 01 0 V 0 O O

to W
g

N m
C
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W
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7 p A W N p O V O) O (O W
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N O O .
O O O O O O p
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7
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01
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? 7 (9
0 co 0 O O co 0 co 0 W O O (011 0)
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m
(O
HensonFoley
Landscape ArchitectLre Civil Engineering
10224 Hickorywood Hill Avenue, Suite 101 A, Huntersville NC 28078
p:704.875.1615 I f:704.875.0959 I www.hensonfoley.com
15
0
z
0
v
W
N
f 10
d
z
5
0L
0
5 10 15
DIAMETER OF PIPE IN FEET
ZONE APRON
MATERML CLASS
OF
STONE SIZE
OF
STONE LENGTH
OF
APRON MIN"
THICIOM
OF STONE
1 SM FIE 3' 4 X D
2 STONE UGHT 8' 6 X D 12'
3 STONE MEDLW 13' 8 X D 18'
4 STONE HEM 23' 8 X D 30'
5 STONE HEAVY 23' 10 X D 30'
6 SRME HEMIY 23' 12 X D 30'
REQIM LARGER SIM OR ANOM TYPE OF
7 DEVICE. DESIGN IS MW THE SCOPE OF THIS
PROCOLIF E.
WOM - DMMETER + 0.4 (LENGM) : 6, LEmMN
• LENGM TO PREVENT SCOUR HOLE
NAME WEIGHT 9ZE SPECiI MNS

RIP-RAP
30% SHALL WBOH AT LUST 100
LBS EACH. NO MORE THAN 10%
CLASS 1 5 -200 SHALL W9GH LESS THAN 15 LBS.
EACH.
60% SHALL WEIGH AT LEAST 100
CLASS 2 25 -250 LBS EACH. NO MORE THAN SX
SHALL WEIGH LESS THAN 50 LK
EACH.
EROSION CONT ROL STONE
CLASS A 10% TOP R BOTTOM SIZES.
NO GRADATION SPEf M.
CLASS 8 15 -300 NO GRADATION SPECM.
SIRUCW Q-FLOW WAM OF OURET DEPM ZONE APRON APRON APRON STONE REMMNS
(as) I
PPE VEICCOY OF FLOW LENGTH WIDTH 7HU0ESS CLASS
(IN.) (FPS) (Fr.) (Fr.) (Fr.) (1)
4
98 24 4.40 1 1 10 6 12 B
FES 13 .
SOURCE: %AW R CHANNEL LINING PROCEDl1R . NEW YORI( DEPARTMENT OF TRANSPORTATION, DMSION OF DOM AND CONSTRUCT 1971.
???I??UTCwu• The Stormwater Management
••?' 10 StormFilter'° Sizing Summary
CONSTRUCTION PRODUCTS INC.
Dollar General - Boone
Stormwater Treatment System - Sizing Proposal
Boone, NC
Information provided:
• Total contributing area = 0.93 acres
• Impervious area = 0.65 acres
• Water Quality Volume (to be stored) = 1,720 ft3
• Presiding agency = NCDENR
Assumptions:
• Mass load design method
• Design runoff volume =1.0"
• Cartridge operating flow rate = 1 gpm/sf (7.5 gpm or less using 18" cartridges)
• Media = Perlite/Zeolite/GAC (ZPG)
• Drop required from inlet to outlet = 2.0' (using 18" cartridges)
Size and cost estimates:
The Stormwater Management StormFilter® is a passive siphon-actuated, flow-through, stormwater filtration
system consisting of a structure that houses rechargeable, media-filled filter cartridges. The StormFilter works by
passing stormwater through the media-filled cartridges, which trap particulates and adsorb pollutants such as
dissolved metals, nutrients, and hydrocarbons.
The StormFilter system is sized to treat the first 1.0" volume of runoff from the site. The system is sized according
to the annual mass load method as described in the Stormwater Management, Inc. design manual. Essentially, this
method models the total mass load of TSS, in pounds, generated from the site on an annualized basis, using the
information above. The number of cartridges required to meet this mass load requirement is then calculated, as a
function of the total mass than can be removed per cartridge prior to required filter changeout.
The StormFilter for this site was sized to provide (7) 18" cartridges in order to meet the mass load requirement.
CONTECH can accommodate 7 cartridges using a precast 6'x12' StormFilter (see attached drawing). The 18" cartridge
contains 7.5 sf of media surface area with a 7" media depth radially around the circumference of the cartridge. The
estimated cost of this system, complete and delivered to the jobsite, is available upon request. The contractor is
responsible for installing the vault and all external piping.
The water quality volume must be stored upstream of the StormFilter. CONTECH recommends using a
minimum of 61 linear feet of 72" CMP for this volume. A low flow water quality pipe is placed at the bottom of
the system to direct the water quality volume to the StormFilter. A high flow weir set at the water quality
volume elevation to divert larger storms to outfall. See the attached layout for more information.
Maintenance:
The StormFilter requires regular maintenance to operate effectively. The expected maintenance interval is
12-18 months, but may vary depending on weather and site conditions. Please contact CONTECH or navigate to
contechstormwater.com for more information in this regard.
521 Progress Drive, Suite H, Linthicum, MD 21090
Toll-free: 886-740-3318 Fax: [phone]
A???/??T?wV® Determining Number of
7 Cartridges for Volume-Based
??j???? ¦ rte...
CONSTRUCTION PRODUCTS INC. Design in NC
CONTECH Stormwater Solutions Inc. Engineer:
Date
ATM Blue Cells = Input
5/13/2011 Black Cells = Calculation
Site Information
Project Name
Project State
Project Location
Drainage Area, Ad
Impervious Area, Ai
Pervious Area, Ap
% Impervious
Runoff Coefficient, Rv
Water Quality Volume Calculations
Design storm rainfall depth, Rd
Water quality volume, WQV
Storage Component Calculations
Capture 75% of WQV
Storage pipe diameter, D
Length of pipe required, L
Pretreatment credit (estimated or calculated), %pre
Mass loading calculations
Mean Annual Rainfall, P
Agency required % removal
Percent Runoff Capture (% capture)
Mean Annual Runoff,Vt
Event Mean Concentration of Pollutant, EMC
Annual Mass Load, Mtota
Filter System
Filtration brand
Cartridge height
Specific Flow Rate, q
Cartridge Quantity Calculation
Mass removed by pretreatment system, Mpre
Mass load to filters after pretreatment, Mpass,
Estimate the required filter efficiency, Efl,ter
Mass to be captured by filters, Mfiter
Cartridge Flow rate, Qcart
Mass load per cartridge, Mca,t (Ibs)
Number of Cartridges required, Nmass
Treatment Capacity
Dollar General - Boone
North Carolina
Boone
0.93 ac
0.65 ac
0.28
70%
0.68 =0.05+0.9*(Ai/Ad)
1.0 in
2292.3 ft' =Ad*Rv*Rd"(43560/12)
1719.3 ft' =0.75*WQV
72 in
60.8 ft =WQV/(PI*(D/(2*12))^2)
30%
45 in (45" Raleigh)
85%
90%
92,840 ft' =P*Ad*Rv*(43560/12)*%capture
70.0 mg/I
405.46lbs =EMC*Vt*(28.3)*(0.000001)*(2.2046)
StormFilter
18 in
1 gpm/ftz
122 Ibs =Mtotal * %removal
284 Ibs =Mtotal - Mpre
79% =1+(%removal - 1)/(1 - %pre)
223 Ibs =Mpass1 * Efilter
7.5 gpm =q * (7.5 ft2/cartridge)
36 Ibs =lookup mass load per cartridge
7 =ROUNDUP(Mfilter/Mcart,O)
0.12 =Nmass*(Qcart/449)
SUMMARY
Treatment Flow Rate, cfs 0.12
Cartridge Flow Rate, gpm 7.5
Number of Cartridges
7
02008 CONTECH Stormwater Solutions
contechstonnwater.com
1 of 1
re
tea'

SThe Stormwater Management StormFilter®
for the North Carolina
Division of Water Quality STORMWATER
INC.

Preliminary Evaluation Period
March, 2008; REVISED July, 2008
521 Progress Drive, Suite H, Linthicum, MD 21090 Tel:[phone] contechstormwater.com
CONTENTS
THE STORMWATER MANAGEMENT STORMFILTER® ...............................................................1
DESCRIPTION ......................................................................................... ........................................1
STORMFILTER OPERATION ...................................................................... ........................................2
CARTRIDGE OPERATION .......................................................................... ........................................2
ADJUSTABLE FLOW RATE ........................................................................ ........................................3
FILTER MEDIA ......................................................................................... ........................................4
STORMFILTER SYSTEM SIZING OPTIONS FOR NORTH CAROLINA ........................................4
FLOW-BASED SIZING .......................................................................................................................4
VOLUME-BASED SIZING ...................................................................................................................5
MASS-LOAD ANALYSIS ............................................................................ ........................................ 5
RECOMMENDED STORMFILTER SIZING .............................................................................................6
STORMFILTER PERFORMANCE EVALUATION ...........................................................................8
LABORATORY PERFORMANCE ................................................................. ........................................8
FIELD PERFORMANCE ............................................................................. ......................................10
FIELD PERFORMANCE -WASHINGTON ..................................................... ......................................10
FIELD PERFORMANCE - NEW JERSEY ...................................................... ......................................10
EXPECTED PERFORMANCE - NORTH CAROLINA ....................................... ......................................11
PRELIMINARY EVALUATION PERIOD REMEDIAL ACTION PLAN ...........................................12
PROJECT PLAN ....................................................................................... ......................................12
TECHNICAL ADVISOR ............................................................................... ......................................12
REMEDIAL ACTIONS ......................................................................................................................13
OPERATION AND MAINTENANCE ..............................................................................................14
REFERENCES ...............................................................................................................................15
APPENDICES
Appendix 1 StormFilter System Schematic Configurations
Appendix 2 Mass Load Design Example Calculation
Appendix 3 StormFilter Maintenance and Inspection Procedures
Appendix 4 Agency Approvals and Parameter Briefs
Appendix 5 StormFilter System Patents
CONTECH Stormwater Solutions StormFilter PEP NCDWQ March, 2008, Revised July, 2008
The Stormwater Management StormFilter®
DESCRIPTION
The Stormwater Management StormFilter® (StormFilter) is a passive, flow-through, stormwater
filtration system that improves the quality of stormwater runoff from the urban environment before
it enters receiving waterways by removing and sequestering non-point source pollutants, including
sediment (Total Suspended Solids - TSS), oil and grease, soluble metals, nutrients, organics, and
trash and debris.
The StormFilter is typically comprised of a concrete vault that houses rechargeable, media-filled,
filter cartridges. Stormwater from storm drains or surface runoff is conveyed to the structure where
it is percolated through these media-filled cartridges. Once filtered through the media, the treated
stormwater is directed to a collection pipe or discharged to an open channel drainage way.
The StormFilter is offered in a variety of configurations or containers depending on the specific
application and site conditions: precast vault, box culvert vault, panel vault, manhole, and cast-in-
place concrete. The StormFilter is also offered in a steel catch basin or a concrete curb inlet
configuration. The precast, manhole, and inlet configuration models utilize standard pre-
manufactured units and arrive at the construction site with the filter cartridges and other internal
components already in place to ease the installation process; the box culvert, panel vault, and
cast-in-place units are customized for larger flows and require installation of cartridges at the site.
Figure 1 shows a typical precast StormFilter unit. Additional figures representing different design
configurations are provided in Appendix 1.
OVERFLOW RISER AND HOOD
INLET ENERGY DISSIPATER
Figure 1. A typical precast StormFilter.
CONTECH Stormwater Solutions StormFilter PEP NCDWQ March, 2008, Revised July, 2008 1 of 15
The Stormwater Management StormFilter®
STORMFILTER OPERATION
The typical StormFilter unit is composed of an inlet energy dissipater, the filtration bay which
includes the under drain (referenced as conduit in Figure 1), and the overflow riser and hood. It is
important to note, however, that the overflow riser will be sealed on the design configuration
proposed for North Carolina. This is generally referred to as a Volume-Design, and forces all water
to leave the system through the filters, preventing re-suspension and washout of previously
trapped pollutants.
Stormwater first enters the system through an inlet pipe which is plumbed from catch basins
throughout the drainage area. Stormwater is directed through the inlet energy dissipater and into
the filtration bay where treatment will take place. Once in the filtration bay, the stormwater begins
to pond and fills the vault. As the depth of the stormwater nears the top of the cartridge, the runoff
begins to percolate horizontally through the media contained in the StormFilter cartridges'. After
passing through the media, the treated water in each cartridge collects in the cartridge's center
tube' from where it is directed into the outlet sump by an under-drain manifold. The treated water
in the outlet sump is then discharged through a single outlet pipe to a receiving waterway,
groundwater recharge system, water harvesting system, or other stormwater conveyance.
CARTRIDGE OPERATION
As the incoming stormwater fills the filtration bay, it also fills the voids in the filter media within
each cartridge. The air under the cartridge hood and within the media voids is displaced by the
incoming water and purged from beneath the hood through the one-way check valve located in the
cap at the top of the cartridge center tube'. Once the center tube is filled with water, there is
enough buoyant force to cause the center tube float valve' to rise, opening the cartridge orifice' at
the bottom of the center tube. The float valve in the open position also causes the check valve in
the air lock cap' to close. The combination of the open float valve at the bottom of the cartridge,
and the closed check valve at the top 1) allows water to percolate horizontally through the media'
and into the center tube, and drain out of the cartridge at the bottom of the center tube into the
under drain manifold; and 2) prevents air from coming back in through the top of the cartridge,
effectively creating a siphon'.
The siphon equalizes the hydraulic head differential between the upper and lower vertical surfaces
of the filter media. This serves to draw the stormwater through the media equally throughout the
full surface area and volume of the filter. Thus, the entire filter cartridge is used to filter water
throughout the duration of the storm, even as the water surface elevation in the filtration bay
begins to recede.
Siphonic filtration continues until the water surface elevation drops to the elevation of the
scrubbing regulators located around the bottom edge of the hood'. At this point, the siphon breaks
and air is quickly drawn beneath the hood through the scrubbing regulators, causing high-energy
turbulence between the inner surface of the hood and the outer surface of the filter media. This
turbulence agitates the surface of the filter media, releasing accumulated course sediments on the
outer screen, flushing them from beneath the hood, and allowing them to settle to the vault floor.
This surface-cleaning mechanism maintains the permeability of the filter surface and enhances the
overall performance and longevity of the system.
After the water has been filtered and the vault has drained, the float valve returns to its original
closed position and is ready for the next storm event. The vault is generally dry between storm
events.
' Patented components of the StormFilter System. Refer to Appendix 5 for StormFilter System technology
patents.
CONTECH Stormwater Solutions StormFilter PEP NCDWQ 3/2008; Revised July, 2008 2 of 15
The Stormwater Management StormFilter®
AIR LOCK CAP WITH CHECK VALVE / LIFTING TAB
FILTER MEDIA I`-
f
CENTER TUBE
ICI .,_- ---
i
SCRUBBING REGULATOR
FLOAT VALVE
OUTER MESH
/ MOOD
UNFILTERED WATER UNFILTERED
FtLTERED WATER
UNDER-DRAIN MANIFOLD
FILTERED WATER
VAULT FLOOR
UNDER-DRAIN MANIFOLD
CAST INTO VAULT FLOOR
Figure 2. The StormFilter Cartridge.
ADJUSTABLE FLOW RATE
The StormFilter cartridges contain a calibrated restrictor disc at the bottom of the center tube' that
serves as a hydraulic control. This serves to throttle the flow through the cartridge at a constant
flow rate for the entire maintenance cycle. In contrast, the flow rate of typical media filters, such as
a sand filter, is controlled by the media surface, and is therefore variable, depending on the
condition (cleanliness) of the media. The StormFilter system specific flow rate, defined as the flow
per unit surface area of media, ranges from 0.3 to 2 gallons per minute per square foot of media
surface area (gpm/ft). The specific flow rate represents the critical sizing standard, and can be
correlated to the demonstrated performance of the system. A slower specific flow rate results in a
slower velocity of water through the system and longer contact time between the media and
stormwater, and thus yields better performance (CONTECH 2004a, 2006a).
The cartridge flow rate is the product of the specific flow rate and the surface area of the cartridge.
Therefore, a standard 18" tall cartridge with a specific flow rate of 1 gpm/ft2 and a media surface
area of 7.5 ft2 (and a media volume of 2.6 ft3) has a cartridge flow rate of 7.5 gpm. Similarly, a 27"
tall cartridge with a specific flow rate of 1 gpm/ft2 and a media surface area of 11.3 ft2 (and a media
volume of 3.9 ft3) has a cartridge flow rate of 11.3 gpm. The taller cartridge offers the option of
more surface area of media in the same horizontal footprint, thus allowing the overall system
footprint to be reduced. However, the critical performance related design variable, the specific flow
rate (gpm/ft2), is held constant, ensuring consistent performance between the two sized cartridges.
System sizing in North Carolina is based on the designation of a specific flow rate. Table 1
provides a summary of the cartridge specifications.
CONTECH Stormwater Solutions StormFilter PEP NCDWQ 3/2008; Revised July, 2008 3 of 15
The Stormwater Management StormFilter®
FILTER MEDIA
The filter media for the StormFilter can be selected based on the needs of the site. Different media
have demonstrated an ability to capture and sequester different urban pollutants. The following
media are generally available for use in North Carolina. The designation of a specific media for
use in certain watersheds or design situations is discussed further in the Design and Sizing
section.
Perlite is a naturally occurring puffed volcanic ash. The large volume of interstitial pore
spaces make it very effective for removing TSS, oil, and grease.
Zeolite is a naturally occurring mineral used to remove soluble metals, ammonium and
some organics. It can be sieved to provide a fine zeolite grade of media that can be
considered as a substitute for sand.
- Granular Activated Carbon (GAC) has a micro-porous structure with an extensive
surface area to provide high levels of adsorption. It is primarily used to remove oil and
grease and organics such as herbicides and pesticides.
- ZPG is a combination of media to target several different pollutants common in the
urban setting. An outer ring of perlite provides the "heavy lifting" for the removal of
solids (TSS), oil, and grease. This is backed by an inner concentric ring of a mixture of
zeolite and GAC.
- CSF8 Leaf Media and MetalRxTm are created from deciduous leaves processed into
granular, organic media. CSF is most effective for removing soluble metals, TSS, oil
and grease, and neutralizing acid rain. MetalRx, a final gradation, is used for higher
levels of metal removal. (These compost media are not necessarily recommended for
nutrient limited watersheds since there may be an export of nutrients during the initial
break-in of the media.)
StormFilter System Sizing Options for North Carolina
The StormFilter system can be configured in different ways to meet a variety of different site
conditions. The system sizing in terms of cartridge count (or surface area/volume of media),
however, is determined by the specific flow rate within one of two sizing methods: flow-based
sizing or volume-based sizing. Both methods are checked for adequacy based on a mass-load
analysis for a minimum one-year service life.
FLOW-BASED SIZING
A flow-based StormFilter system is sized to provide enough filter cartridges to pass the design
peak flow rate from the contributing drainage area. Flows in excess of the design peak are
bypassed either internally over a weir wall, or externally through an upstream bypass or diversion
structure. Depending on the stormwater requirements, the design peak discharge may be
calculated as the peak flow rate associated with the one inch (or 1.5 inch in Coastal Counties)
water quality volume or the design peak discharge associated with a drawdown requirement from
a detention structure. In either case, the size of the StormFilter system is determined by dividing
the calculated peak flow rate by the individual cartridge flow rate to determine the total number of
cartridges required. The system is then configured to hold the required number of cartridges.
This design typically requires a large number of cartridges since the flow rate of each cartridge,
and therefore the system as a whole, is relatively slow compared to the design peak discharge of
the water quality volume coming from the contributing drainage area. CSS has verified through
CONTECH Stormwater Solutions StormFilter PEP NCDWQ 3/2008; Revised July, 2008 4 of 15
The Stormwater Management StormFilter®
testing that adequate contact time between the stormwater and filter media requires specific flow
rates in the range of 1 to 2 gpm/ft2, maximum. A mass-load design check of the system is then
conducted to ensure that the number of cartridges provides enough filter media to meet a
minimum one-year service life. Typically, the flow-based design will require more cartridges than
that needed for the one-year service life. (Refer to the Mass-Load Analysis description below.)
VOLUME-BASED SIZING
A volume-based StormFilter system is designed in conjunction with upstream storage. This design
utilizes the total cartridge discharge (cartridge flow rate times the number of cartridges) as the
outlet control structure of the detention system. This is considered a "catch and treat" design
where the required volume is held in the upstream detention and slowly drained down by the
cartridges. The number of cartridges is determined by the mass-load analysis and will typically
require fewer cartridges than the flow based sizing since the system is not required to pass a
design flow rate from the drainage area. The benefit of a volume design is the ability to slow the
specific flow rate of the cartridge down to a minimum to provide a greater level of performance.
(CONTECH 2004a, 2006a)
Figures in Appendix 1 provide schematic plans and profiles of flow-based and volume-based
systems.
MASS-LOAD ANALYSIS
The mass-load analysis consists of predicting the total mass of solids coming off of the
contributing drainage area within a set time period and determining the number of filter cartridges
required to effectively capture the predicted mass load. This analysis is based on assumptions of
the unit load (Event Mean Concentration - EMC) of solids coming off the drainage area, the time
period (typically assumed to be a minimum one year service life of the BMP), and the anticipated
rainfall for that time period. Most importantly, the analysis requires accurate data with regard to the
loading capacity of the filter media and cartridges.
The mass-load capacity of the StormFilter cartridge is a function of the type of media, the volume
(and surface area) of media, and the specific flow rate of the cartridge. The type of media
represents the coarseness and the capacity to hold sediment and other solids. Physical straining is
the primary removal mechanism for total suspended solids and promotes solids removal by
trapping of suspended particles within the interstitial spaces of the media matrix either in
microchannels or dead end pores. The mass load analysis provides a method for determining how
fast those spaces will become clogged such that the filtration rate is reduced to less than the
design flow rate or specific flow rate of the cartridge.
Perlite is an example of a coarse media with a large volume of interstitial spaces to hold solids and
still allow water to pass through it. Though perlite is a coarse material with a high permeability, the
hydraulic control, or restrictor disc, in the bottom of the cartridge limits the filtration rate in order to
take full advantage of the full depth of the media, and maximize the contact time between the
stormwater and the media. Sand, on the other hand, is a much finer gradation of filter media,
which makes it very effective but also limits it loading capacity. Finer media relies primarily on
straining the stormwater at the media surface, commonly referred to as cake filtration, which limits
the effective service life of the system. The surface of the media quickly becomes the hydraulic
control for the system, and results in a variable and gradually declining filtration rate.
The volume and surface area of the media is a measure of how much media is available to
sequester pollutants. The taller cartridge has a greater surface area and volume, and therefore
can hold more mass of pollutants before reaching the end of its service life.
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The Stormwater Management StormFilter®
The specific flow rate represents the design flow per surface area of media (gpm/ft2) as controlled
by the restrictor disc at the bottom of the cartridge. A slower specific flow rate or cartridge flow rate
means it will require a greater mass load of solids to effectively reduce the media filtration rate to a
rate less than that of the restrictor disc. CSS has carefully studied the load capacity of different
media at various specific flow rates in order to support this analysis and life cycle modeling. (SMI
1999, CONTECH 2005,). For example, a 2 gpm/ft2 specific flow rate on an 18" cartridge (15 gpm
cartridge flow rate) can sequester a total of 22.5 pounds of sediment before the cartridge filtration
rate is reduced to less than 15 gpm. The same cartridge with a 1 gpm/ft2 specific flow rate can
sequester up to 36 pounds of sediment. This load consists of the solids filtered and sequestered
within the media, the material which is settled within the vault during the filtering cycle, and the
material which is released to the vault floor by the surface cleansing mechanism of the cartridge
after each filtering cycle.
Table 1 below provides a summary of the different cartridge sizes and geometry (surface area and
volume of media) and specific flow rates, and the corresponding mass load capacities. Appendix 2
provides an example mass load analysis calculation.
Cartridge Flow Rate

(gpm/cart) 5 10 7.5 15 11.3 22.5
Surface Area of Media (ft2) 5 5 7.5 7.5 11.3 11.3
Volume of Media (ft) 1.73 1.73 2.6 2.6 3.9 3.9
Surface Area Specific Flow

Rate m/ftz 1 2 1 2 1 2
Volumetric Specific Flow

Rate (gpm/ft3) 2.9 5.8 2.9 5.8 2.9 5.8
Flow per inch height of

cartridge (gpm/in) 0.42 0.83 0.42 0.83 0.42 0.83
Media Bed Depth (inches) 7 7 7 7 7 7
Mass Loading Capacity

(lb/cart) 24 15 36
1 22.5 54 33.75

System Head Loss (ft)
1.8
1.8
2.3
2.3
3.1
3.1
-1
Table 1 - Summary of StormFilter Cartridge Specifications using ZPG media
RECOMMENDED STORMFILTER SIZING
CSS conducted the first PEP monitoring study of the StormFilter at the Currituck Gas House in
Barco, NC. (CONTECH 2007a) While the results of that monitoring study were encouraging, very
specific elements of the design were identified for improvement. Since the PEP program is
designed to allow DWQ an opportunity to evaluate the performance of a technology and develop
appropriate permitting criteria, conclusions from the Currituck monitoring study, combined with
conclusive results derived from numerous other monitoring studies, helped derive the following
design and sizing changes for meeting the treatment objectives and performance goals of the NC
Stormwater program.
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The Stormwater Management StormFilter®
Total Suspended Solids
The Currituck Gas House system is an off-line flow-based design with both an external by-pass
(diversion manhole) and an internal bypass (downstream weir wall) for allowing large or intense
storms to bypass treatment. An internal bypass of any BMP potentially allows for the re-
suspension and washout of previously trapped materials, especially the silt sized sediment and
organic material particles that are easily mobilized. Therefore, future designs are recommended
to be volume-based designs with a full height downstream wall to prevent any trapped
sediment material from being transported out of the system.
Further, a review of available data can provide insight into the StormFilter design criteria that
directly influences performance: specific flow rate. Performance studies have demonstrated that
slowing the system specific flow rate from 2 gpm/ft2 to 1 gpm/ft2 will yield a significant improvement
in the removal of silt sized particles (CONTECH 2004a, 2006a). The increased performance
associated with the slower specific flow rate has been further validated through field monitoring
studies as providing comparative performance consistent with the North Carolina Stormwater
Program performance goals for the removal of TSS (CONTECH 2007b). Therefore, in addition to
the volume-based sizing recommended above, future designs are also recommended to be
sized with a 1 gpm/ft2 specific flow rate.
The following represent specific sizing and design standards for the StormFilter System for
meeting the North Carolina TSS performance goals:
- Volume-based sizing;
¦ 1 gpm/ft2 specific flow rate
¦ ZPG media
¦ Full height downstream wall (no internal bypass)
- Downstream of detention;
¦ Detention sized for 75% of the WQv "
¦ Dead storage sump for sediment retention
- Mass-Load Analysis to determine the minimum number of cartridges;
¦ Annual Rainfall per Appendix 2
¦ Mass load EMC per Appendix 2
¦ 1" (or 1.5") WQv representing 90% of the total annual rainfall/runoff volume
¦ Pre-treatment load reduction credit of 30% (based on typical sand fraction of
a silt loam soil material)
* Detention designs may also provide for minimum drawdown time requirements.
Project specific designs will address each requirement as needed.
Nutrients
One of the notable advantages of an engineered system such as the StormFilter is the ability to
modify the design to address site or watershed specific treatment objectives and/or performance
goals. As noted above, a design enhancement such as reducing the cartridge flow rate can
improve system performance. Similarly, the selection of alternate filter media can likewise improve
performance. Alternate media such as sand, fine zeolite, or other reactive fine media, along with a
further reduction in the specific cartridge flow rate has been shown to be effective at removing
nutrients from stormwater (CONTECH 2006b; 2006c). Therefore, as a continuation of the
CONTECH Stormwater Solutions StormFilter PEP NCDWQ 3/2008; Revised July, 2008 7 of 16
The Stormwater Management StormFilter®
StormFilter PEP process, additional monitoring sites in the piedmont area of the state will be
identified for further system monitoring and performance evaluation relative to nutrient treatment
objectives.
The criteria listed above for the TSS performance goals will be modified to further reduce the
cartridge flow rate to 0.3 gpm/ft2. In addition, depending on site conditions, and the status of
ongoing research, alternate media will be recommended at the outset, with the option to further
modify the media as measured performance may justify.
StormFilter Performance Evaluation
BMP verification programs around the country have incorporated both laboratory testing and field
monitoring into the analysis of BMP performance. In most cases, the use of laboratory testing is to
provide confidence that the system can in fact meet the performance goals once it is installed in
the field. Equally important, the lab testing helps establish the sizing criteria so that as multiple
installations are allowed in order to target appropriate development sites for field monitoring, all of
the systems are appropriately and consistently sized in accordance with the approved criteria. The
following provides a brief overview and summary of the testing and field monitoring data that has
been reviewed and accepted by the regulatory agencies noted. Appendix 4 provides a Total
Suspended Solids Parameter Brief providing more detail of the laboratory testing.
LABORATORY PERFORMANCE
CSS has had performance claims for suspended solids (sandy loam and silt loam particle size
distributions) verified by New Jersey Corporation for Advanced Technology (NJCAT) using
laboratory data. These claims were used to obtain a Conditional Interim Certification from the
State of New Jersey Department of Environmental Protection (NJDEP) in September 2002.
Similar to the NJCAT verification, the State of Washington Department of Ecology (Ecology) used
field and lab data (SIL-CO-SIL 106 particle size distribution) to provide a short-term Conditional
Use Designation (CUD) for the StormFilter in October 2002. Please refer to the Field Performance
- Washington section below to see the results that led to the General Use Level Designation
(GULD) in Washington. Summaries of particle size distribution and TSS removal investigations by
Stormwater Management have been included in Tables 2 and 3. In addition, Figure 3 shows the
sediment texture of the Ecology laboratory testing standard.
Table 2. Sediment Particle Size Distributions.
Percent by mass (atmroximate''
Particle Size
(microns) Sandy
loam a Silt
loam a SIL-CO-SIL
106 b
500 -1000 5.0 5.0 0
250 - 500 5.0 2.5 0
100 - 250 30.0 2.5 0
50-100 15.0 5.0 20.0
2-50 40.0 65.0 80.0
1-2 5.0 20.0 0.0
a Stormwater Management tested Oregon silt and sandy loams for New Jersey Corporation for Advanced Technology
verification of TSS performance claims.
b Stormwater Management tested SIL-CO-SIL 106 for Washington State Department of Ecology per the Technology
Assessment Protocol - Ecology (2001).
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The Stormwater Management StormFilter®
Table 3. TSS Removals in the Laboratory Using Different Particle Size Distributions
Cartridge Percent Removal (%)
Flow Rate Sandy Silt SIL-CO-SIL
Media Type (gpm) loam a loam a 106 a
Coarse Perlite 15 77 - 80 72 - 77
Coarse Perlite 7.5 76 - 78
Coarse Fine Perlite 15
Coarse Fine Perlite 7.5 68 - 75 79 - 82
Fine Perlite 15 73 - 78
Fine Perlite 7.5 85 - 88
CSF® leaf b 15 68 - 79
Coarse Perlite/Zeolite ` 15 63 - 84
ZPG d 7.5 86 - 89
a Linear regression was used in the data analysis, the table presents the upper and lower 95% confidence limits.
Data was collected in the Stormwater Management laboratory using simulated stormwater for TSS concentrations
between 0 - 350 mg/L. Silt and sandy loam performance data was NJCAT-verified.
b Performance of the CSF leaf media was tested using both field and laboratory investigations. Laboratory studies
used a Palatine loam sediment. Field data is from the Pacific Northwest.
Performance of the coarse perlite / coarse zeolite media was tested using a Palatine loam sediment. Reported in
Total Suspended Solids Removal using StormFilter® Technology.
d ZPGTM is a trademarked blend of perlite, zeolite, and granular activated carbon.
SCS106 Sil-CO-Sil106
OK110 OK-110
LSN Lake Stevens North (WA)
HMP Heritage Marketplace (WA)
GYS Greenville Yards (NJ)
% Clay
5o
40
0
100
10
90
20

70 /
60
30
20
Source: Brady N C, b Nkd R R (iM)
hue Nahas OW Ropeaw of SW (! 2th ad)
Upper saWria RIYW NJ ProMros-ho
30
40
% Sitt
50
60/65%

70
80
10 90
GYS
2%- flu - 0 LSN SCS14H 100
100 90 80 70 60 50 40 ?30 20 10 0
% Sand \ %
Figure 3. Ternary plot of sediment textures (USDA). Determination of texture for the Lake Stevens
North (LSN) site is provided as an example.
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FIELD PERFORMANCE
The StormFilter has a proven track record and a demonstrated capability of meeting the
stormwater management goals for which it has been intended. The StormFilter has been in use
for over ten years, and as of April 2005 over 35,000 cartridges have been installed in over 400
cities in the United States. The StormFilter has been thoroughly evaluated in the field and the
summaries of two of these field investigations - in Washington, and New Jersey - are summarized
here as a demonstration of the performance of the system. The investigations in Washington and
New Jersey were conducted under the oversight of the verification programs referenced in the
Laboratory Performance section above, and meet the typical monitoring criteria for BMP
demonstration studies, namely: at least 15 storm events were sampled for each; the studies were
independently verified; monitoring was conducted using standard protocols which require
proportional sampling; concentrations in the study were flow-weighted; and the systems were in
place for at least one year prior to monitoring. Summary documentation of these studies is
attached in Appendix 4.
FIELD PERFORMANCE - WASHINGTON
Pursuant to a Conditional (short-term) Use Designation, multiple StormFilter installations in the
Pacific Northwest were monitored for a 12-month period using the Guidance for Emerging
Stormwater Treatment Technologies, Technical Assessment Protocol - Ecology (TAPE).
Following a year of study, data collected from two StormFilter system installations configured with
ZPG media and operating at a design filtration rate of 28 L/min (7.5 gpm) per cartridge, a specific
flow rate of 1 gpm/ftz, were evaluated and submitted to Ecology for review. (CONTECH 2004b). It
is important to note that even as the rainfall patterns are extremely different in the pacific
northwest, the system performance was measured at the same design specific flow rate and
therefore represents a comparable system and system performance data.
Over the course of a year, the two systems demonstrated satisfaction of the Ecology Basic
Treatment Performance Goal (Table 4). Thirty-three storm events were captured, of which 22
qualified according to the TAPE storm event criteria. The qualified storm events document system
performance over a peak operating rate range of 56% to 257%. Figure 3 shows the reconstructed
influent sediment textures for the two sites, Lake Stevens North and Heritage Marketplace.
Washington defines TSS as sediment less than 500 microns using the Suspended-Sediment
Concentration method (ASTM 3977-97), and it is referred to as TSS-WA. As a whole, the TSS-
WA data for these qualifying events are characterized by: 1) a silt to silt loam texture; 2) an
influent EMC range of 7 to 519 mg/L that was not normally distributed and skewed sharply to the
right; and 3) an average influent EMC of 114 mg/L and a median of 83 mg/L. Satisfactory
performance was demonstrated by an average effluent TSS-WA EMC of 20 mg/L for influent TSS-
WA EMCs less than 100 mg/L and an aggregate pollutant load reduction of 89% for influent TSS-
WA EMCs greater than 100 mg/L using data from qualifying storm events. TSS-WA removal was
found to be significant at the >99% level. It was concluded that the StormFilter operating at 28
L/min per cartridge with ZPG media meets the Ecology requirements for Basic Treatment.
Stormwater Management was awarded a General Use Level Designation for Basic Treatment by
Ecology on January 26, 2005, and updated December, 2007 to reflect the design specific flow rate
of 1 gpm/ftz rather than a specific cartridge size.
FIELD PERFORMANCE - NEW JERSEY
Similar to the Ecology emerging technology program, Stormwater Management has completed a
field performance evaluation for the New Jersey Department of Environmental Protection
(NJDEP). (CONTECH 2006d). NJDEP in partnership with the New Jersey Corporation for
Advanced Technology (NJCAT) use the Technology Acceptance Reciprocity Partnership (TARP)
CONTECH Stormwater Solutions StormFilter PEP NCDWQ 3/2008; Revised July, 2008 10 of 16
The Stormwater Management StormFilter®
Tier II Protocol for Stormwater Best Management Practice Demonstrations as the guidance
document for demonstrating compliance and obtaining Final Certification. A StormFilter
installation in Jersey City, New Jersey was monitored over an 18-month period with 16 qualified
storm events consisting of more than 15 inches of rainfall captured. The StormFilter system was
configured with fine perlite media and operates at a design filtration rate of 56 L/min (15 gpm) per
cartridge with a specific flow rate of 2 gpm/ft2.
TSS-WA (< 500 microns) was evaluated for comparative purposes and the qualifying events have
been characterized as: 1) a sandy loam texture (based on filter autopsy at closure of
investigation); 2) an influent EMC range of 11 to 462 mg/L that is not normally distributed; 3) a
median influent EMC of 56 mg/L; and 4) a median effluent EMC as listed in Table 4.
Table 4 Summarized Performance for the StormFilter Field Evaluations in Washington and New
Jersey

Field Evaluation
Description GYS HMP and ESN
(pooled data
Land Use Commercial Commercial and Roadway
Location NJ WA
Soil Texture Sandy loam Silt loam
Specific Flow Rate (gpm/ft2) 2 1
Qualifying Storm Events n = 16 n = 22
D ata Summar y
TSS Influent EMC Media n Effluent EMC (mg/L)
< 100 mg/L 12 19
100 mg/L 25 33
Suspended Solids Reduction (%)
All 80* 82
< 100 mg/L 73 61
a 100 mg/L 82 89
* NJCAT verified regression of EMC (P < 0.001)
EXPECTED PERFORMANCE - NORTH CAROLINA
In the North Carolina Piedmont and Mountain regions, the particle size distribution is expected to
be most similar to that in Washington, namely a silt loam, with a rainfall distribution most similar to
that in New Jersey. It is notable that the ZPG with a specific flow rate of 1 gpm/ft2 as provided in
Washington achieved an 89% solids reduction when influent loads were above 100 mg/I, and a
median effluent of 19 mg/I when influent concentrations were below 100 mg/I. Therefore, as based
on the field performance exhibited in Washington and New Jersey, CSS proposes that the
StormFilter can achieve an 85% sediment removal efficiency when configured with the ZPG media
(consisting of an outer ring of fine perlite or perlite-blend media) and operating at a maximum
design filtration rate of 28 L/min (7.5 gpm) corresponding to a specific flow rate of 1 gpm/ft2.
Further CSS recommends that the treatment benchmark of 85% TSS be clarified to reflect low
influent concentrations and the difficulty in achieving an 85% removal of concentrations less than
100 mg/I.
CONTECH Stormwater Solutions StormFilter PEP NCDWQ 3/2008; Revised July, 2008 11 of 15
The Stormwater Management StormFilter®
Note that the proposal for the Coastal Counties of North Carolina will consist of a 15 gpm cartridge
flow rate, and ZPG filter media.
Preliminary Evaluation Period Remedial Action Plan
The basis for the Preliminary Evaluation Period (PEP) process for innovative and/or proprietary
stormwater treatment technologies is outlined in the North Carolina Administrative Code: 15A
NCAC 02H .1008 Design of Stormwater Management Measures. This Code section includes
provisions for ensuring that the technology meets the intent of the North Carolina stormwater
management program and any watershed specific treatment objectives and performance goals. In
addition, the code, as well as the subsequent DWQ implementation policy as documented in
agency memorandum (dated 6/13/2001) and in the NC Stormwater Best Management Practices
Manual (July 2007, Updated 9/28/07), requires remedial action or some other alternative in the
event that the technology fails to substantially fulfill the requirements it was permitted to meet.
The first StormFilter System PEP evaluation at the Currituck Gas House (CONTECH 2007a) and
DWQ's favorable interpretation of the performance data has allowed the StormFilter to continue in
the PEP program with additional installations for compliance with TSS performance goals. The
process of evaluating the performance of the StormFilter System has provided CSS and DWQ with
a foundation on which to evaluate and establish StormFilter system sizing methodologies, design
loading limitations, and other design particulars as outlined herein. As such, the design and sizing
criteria for future installations is based on this StormFilter PEP documentation.
CSS also recognizes the importance in maintaining the integrity of the PEP process by ensuring
compliance on future StormFilter PEP installations. Therefore, the following process and
accompanying remedial actions are designed to provide progressively improved performance in
the event that the StormFilter System fails to substantially fulfill the requirements as outlined in the
project specific Project Plan described below.
PROJECT PLAN
CSS will develop a project specific Quality Assurance Project Plan (QAPP) that includes a Project
Description, Conditions and Definitions, and a Quality Assurance Plan. This document will identify
all the roles and responsibilities of the Project Team, monitoring protocols, data quality objectives
in compliance with any permit requirements, and most importantly the treatment benchmark for
measuring compliance or substantial fulfillment of the permit requirements. The Project Team
includes, but is not necessarily limited to the CSS Project Manager, Lead Researcher, and Chief
Technology Officer, the local regulatory authority, the State regulatory authority (DWQ), the site
owner or owner's representative, the analytical laboratory, and the project Technical Advisor.
TECHNICAL ADVISOR
CSS will secure the services of a Technical Advisor to review the QAPP for compliance with
standard monitoring protocols and the NC stormwater program treatment objectives and
performance goals. This is a very important role because the traditional regulatory compliance
measure of percent removal efficiency as identified in the NC stormwater program, as well as most
state stormwater programs, has been documented as very problematic and not an appropriate
CONTECH Stormwater Solutions StormFilter PEP NCDWQ 3/2008; Revised July, 2008 12 of 15
The Stormwater Management StormFilter®
performance measure for BMPs'. Therefore, a treatment benchmark that allows for compliance
with the North Carolina stormwater program's percent removal standard, and more importantly
provides a reasonable and scientific assessment for the evaluation of system performance must
be developed and approved for each monitoring project.
CSS has utilized the services of the NC State Biological and Agricultural Engineering Stormwater
Design Group on previous PEP monitoring projects to serve as the initial reviewer of the QAPP,
provide technical and quality assurance oversight of the monitoring, and review and approve
periodic progress reports, and the final report and conclusions. It is our intent to continue to utilize
these services to the extent possible, or an approved alternate if necessary.
REMEDIAL ACTIONS
The decision to initiate remedial action will not be taken without consultation with the Project
Team. The contributing drainage area, weather conditions, or other factors that could influence the
monitoring data will be evaluated to determine if the lack of performance is a function of the
system design and/or sizing, or other external factors. If it is determined by the Project Team that
external factors, including insufficient influent loads, are the cause for the inadequate or
indeterminable performance, then the Project Team will also evaluate the options of continued
monitoring at that particular site, or relocating the monitoring equipment in order to continue
monitoring at an alternate site. In either case, the Project Team will also evaluate the proposed
remedial action(s) and verify that they represent an appropriate course of action to address the
issues for the particular project.
The current StormFilter System design proposal for compliance with the requirement for 85%
average annual removal of Total Suspended Solids (TSS) has been established as a volume-
based design consisting of cartridges filled with ZPG media and operating at a specific flow rate of
1 gpm/ft2. The following represents a progression of remedial actions aimed at adjusting the
system function in order to improve the overall performance of the system:
1. Reduce the specific flow rate to 0.27 gpm/ft2 (2 gpm/cartridge). Laboratory and field
monitoring studies of the StormFilter have demonstrated that reducing the flow rate yields
longer residence time and longer contact time between the stormwater and the media, and
results in improved performance. (CONTECH 2004a, 2006a, 2007b ). Reducing the
specific flow rate is accomplished by replacing the 1 gpm/ft2 restrictor disc in the bottom of
each cartridge with a smaller 0.27 gpm /ft2 restrictor disc.
2. Replace the ZPG media with progressively finer media. This can represent at least two
remedial actions with alternate media specifications: i) fine perlite to replace regular perlite,
and ii) fine zeolite to replace the regular grade of zeolite. Again, monitoring studies have
demonstrated that the StormFilter performance improves with a finer gradation of media.
(CONTECH 2006b).
3. Replace the ZPG media with sand (or fine zeolite with a comparable size gradation), and
provide a site specific Inspection and Maintenance Compliance Service to the owner to
ensure ongoing compliance of the system.
The final remedial action of replacing the ZPG media with sand or comparable zeolite will
generally turn the StormFilter into a vertical siphon actuated sand filter. However, the surface area
I NC State CTE National Broadcast Series Presentation of International Stormwater BMP Database: A Resource for
BMP Selection and Design Guidance, November 29, 2006; Partners: Water Environment Research Foundation (WERF),
Federal Highway Administration (FHWA), American Society of Civil Engineers - Environmental & Water Resources
Institute (ASCE-EWRI), American Public Works Association (APWA), Environmental Protection Agency (EPA)
CONTECH Stormwater Solutions StormFilter PEP NCDWQ 3/2008; Revised July, 2008 13 of 15
The Stormwater Management StormFilter®
requirement for sand filters as required in the NC BMP Manual is larger than that of a typical
StormFilter. This is due to the sand filter design criteria being based on the permeability of clogged
sand (K = 3.5 ft/day). This is appropriate since the media is placed in a horizontal filter bed
geometry that is susceptible to clogging from not only from the filtered material, but also unsettled
material in suspension that that comes to rest on the sand bed surface as the water slowly filters
down (commonly referred to as cake filtration, which often leads to the occlusion of the sand
surface).
The StormFilter, on the other hand, utilizes a hood over the cartridge to protect the vertical
geometry of the filter media, allowing material in suspension to come to rest harmlessly on the
vault floor. In addition, the surface cleansing mechanism of the falling siphon (described in detail in
the Cartridge Operation section) serves to help keep the surface of the media from occluding.
Therefore, while the calculated surface area of the Sand StormFilter System is less than that of the
traditional sand filter, the system performance is comparable to an appropriately sized sand filter
(as a result of comparable media gradation and specific flow rate). The difference in the systems,
however, is potentially realized in the service life of the media. While the hood and surface
cleansing mechanism may serve to equalize the difference in surface area, CSS will develop an
Inspection and Maintenance Compliance Service to ensure continued operation of the system.
These Remedial Actions are focused on the application of StormFilter Systems for compliance
with the TSS performance goals. Alternate Remedial Actions will be developed and submitted to
DWQ and the local permitting authority for any systems proposed in Nutrient Sensitive
Watersheds
Operation and Maintenance
Maintenance is crucial to the ongoing effectiveness of all stormwater treatment solutions. CSS
provides detailed operation and maintenance guidelines with each system. Standard operation
and maintenance guidelines are provided in Appendix 3. Owners can contract directly with CSS
for maintenance, or CSS will train another company's personnel to perform the maintenance.
Stormwater Management tracks each StormFilter and notifies the owner regarding maintenance
needs. We also work with owners to implement source control measures, when requested, that
improve site stormwater management and lower overall maintenance costs.
Once maintenance to a system has been completed, we provide a Certificate of Compliance that
verifies maintenance has been performed and that the system continues to meet the original
design standards. This certificate is sent to the owner, and a copy can be sent to the relevant
local stormwater authority upon request.
CONTECH Stormwater Solutions StormFilter PEP NCDWQ 3/2008; Revised July, 2008 14 of 15
The Stormwater Management StormFilter®
References
CONTECH Stormwater Solutions Inc. (2004a) Evaluation of the Stormwater Management
StormFilter® for the removal of SIL-CO-SIL®106, a standardized silica product: ZPGTM
StormFilter cartridge at 28 L/min (7.5 gpm) (Report No. PE-E062)
CONTECH Stormwater Solutions Inc. (2004b) Performance of the Stormwater Management
StormFilter Relative to Ecology Performance Goals for Basic Treatment (Report No. PE-E072)
Portland, Oregon: Author.
CONTECH Stormwater Solutions Inc. (2005) Evaluation of the Lifecycle Loading Characteristics of
the Stormwater Management StormFilter® Cartridge: ZPG StormFilter cartridge at 28 L/min (7.5
gpm) and Sandy Loam (Report No. PE-F090). Portland, OR: Author
CONTECH Stormwater Solutions Inc. (2006a) Evaluation of The Stormwater Management
StormFilter® for the removal of Sil-Co-Sil®106, a standardized silica product: ZPGTM StormFilter
cartridge at 56 L/min (15 gpm) (Report No. PE-G011)
CONTECH Stormwater Solutions Inc. (2006b) Statistical Comparison of Perlite/CSF,
Perlite/MetalRx, and ZPGTM Combination Media for Suspended Solids Removal at 28
Umin/cartridge (Report No. PE-F060) Portland, Oregon: Author
CONTECH Stormwater Solutions Inc. (2006c) Airport Way Volume StormFilter Field Evaluation
Quarterly Performance Summary: November 2006 through January 2007 (Report No. PE-1-1010)
CONTECH Stormwater Solutions Inc. (2006d) Greenville Yards Stormwater treatment System
Field Evaluation. Stormwater Management StormFilter with ZPG media at 57 L/min/cartridge
(Report No. PE-G081) Portland, OR: Author.
CONTECH Stormwater Solutions Inc. (2007a) The Stormwater Management StormFilter
Preliminary Evaluation Period, Currituck Gas House Final Report. Portland, OR: Author.
CONTECH Stormwater Solutions Inc. (2007b) Summary of Field Performance Evaluation of the
Stormwater Management StormFilter for Removal of Total Suspended Solids (Report No. RS-
0231) Portland, Oregon: Author. Copy enclosed in Appendix 4.
North Carolina Department of Environment and Natural Resources Division of Water Quality
(NCDWQ). (2005) Updated Draft Manual of Stormwater Best Management Practices.
Stormwater Management Inc. (SMI 1999) Sediment Loading on a Perlite Filled StormFilterTM
Cartridge. B. Wigginton; S. De Ridder
CONTECH Stormwater Solutions StormFilter PEP NCDWQ 3/2008; Revised July, 2008 15 of 15
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April 19, 2009
Mr. Ken Pickle
Stormwater and General Permits Unit
North Carolina Department of Environment & Natural Resources
Division of Water Quality
1617 Mail Service Center
Raleigh, NC 27699-1617
RE: Stormwater Management StormFilter® (StormFilter) Preliminary Evaluation Period
Documentation
Thank you for your on-going assistance in our continued efforts to gain approval for the
StormFilter in the North Carolina Division of Water Quality Preliminary Evaluation Period
(PEP) program for Innovative or Proprietary Stormwater Treatment Technologies.
Recently, we have had several inquiries regarding the availability and approval status of
the StormFilter in this program. However, without exception, municipalities have
expressed concerns regarding the ambiguity of the StormFilter's current conditional
approval status and potential impacts to their permit compliance if they allow an
installation prior to full final approval. We are very anxious to coordinate efforts with your
office to address these municipal concerns related to further installations of the
StormFilter under the conditional PEP approval. As discussed in our recent meeting
these concerns include:
1. DWQ permissibility of limited simultaneous installations with only one site
undergoing active monitoring,
2. DWQ concurrence with CONTECH Stormwater Solutions (CONTECH) proposed
remedial action plan,
3. compliance considerations in situations where 85% reduction is impracticable due
to low influent concentration but an irreducible effluent concentration has been
achieved by the StormFilter,
4. and, most specifically, DWQ's willingness to concur with solutions to these issues
in writing.
This document presents CONTECH's understanding of our agreed upon solutions, most
of which are more fully outlined in the most recent PEP submittal which was revised in
July 2008 upon the successful completion of the first PEP performance monitoring project
at the Currituck Gas House in Barco, NC, under the coverage of a Division of Water
Quality (DWQ) Stormwater Permit as required by the PEP program. In addition, updated
sizing recommendations and modifications to the sampling protocol as discussed in our
meeting have been included. This updated information reflects a better understanding of
the StormFilter System performance as learned through the analysis of the data obtained
at the Currituck Gas House, as well as from several otlier monitoring projects around the
country. See last page of this document for signed concurrence by both parties.
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It is our understanding that with DWQ's favorable interpretation of those results and the
growing body of evidence that the StormFilter system can "substantially" meet the
requirements of the PEP program that the StormFilter has been granted approval to
continue in the program with additional installations. The goal is to continue to collect
data in order to support the approval of the StormFilter and inclusion into the NC
Stormwater BMP Manual. CONTECH will actively monitor at least one installation until
the approval process is complete. Data from the active monitoring project will be shared
with all simultaneous installation permit holders and the DWQ on a periodic basis until the
completion of the monitoring. The systems may be modified in the event that monitoring
demonstrates that the system, as designed, fails to substantially fulfill the state
requirements. If the active monitoring indicates the need for system modification/remedial
action, the same action will either be considered at each installation site or individual
sampling will be performed to confirm that individual site performance expectations have
been met. System modification can include a further reduction in the specific flow rate,
the replacement of the media with a finer gradation media, etc.
Remedial action plan
The basis for the PEP process for innovative and/or proprietary stormwater treatment
technologies is outlined in the North Carolina Administrative Code: 15A NCAC 02H.1008
Design of Stormwater Management Measures. This Code section includes provisions for
ensuring that the technology meets the intent of the North Carolina stormwater
management program and any watershed specific treatment objectives and performance
goals. In addition, the code, as well as the subsequent DWQ implementation policy as
documented in agency memorandum (dated 6/13/2001) and in the NC Stormwater Best
Management Practices Manual (July 2007, Updated 9/28/07), requires remedial action or
some other alternative in the event that the technology fails to substantially fulfill the
requirements it was permitted to meet.
CONTECH also recognizes the importance in maintaining the integrity of the PEP process
by ensuring compliance on future StormFilter PEP installations. Therefore, the following
process and accompanying remedial actions are designed to provide progressively
improved performance in the event that the StormFilter System fails to substantially fulfill
the requirements as outlined in the project specific Project Plan described below.
Project Plan
CONTECH will develop a project specific Quality Assurance Project Plan (QAPP) that
includes a Project Description, Conditions and Definitions, and a Quality Assurance Plan.
This document will identify all the roles and responsibilities of the Project Team,
monitoring protocols, data quality objectives in compliance with any permit requirements,
and most importantly the treatment benchmark for measuring compliance or substantial
fulfillment of the permit requirements. The Project Team includes, but is not necessarily
limited to the CONTECH Project Manager, Lead Researcher, and Chief Technology
Officer, the local regulatory authority, the State regulatory authority (DWQ), the site owner
or owner's representative, the analytical laboratory, and the project Technical Advisor.
Technical Advisor
CONTECH will secure the services of a Technical Advisor to review the QAPP for
compliance with standard monitoring protocols and the NC stormwater program treatment
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objectives and performance goals. This is a very important role because the traditional
regulatory compliance measure of percent removal efficiency as identified in the NC
stormwater program, as well as most state stormwater programs, has been documented
as very problematic and not an appropriate performance measure for BMPs (CONTECH
2008a). Therefore, a treatment benchmark that allows for compliance with the North
Carolina stormwater program's percent removal standard, and more importantly provides
a reasonable and scientific assessment for the evaluation of system performance must be
developed and approved for each monitoring project.
CONTECH has utilized the services of the NC State Biological and Agricultural
Engineering Stormwater Design Group on previous PEP monitoring projects to serve as
the initial reviewer of the QAPP, provide technical and quality assurance oversight of the
monitoring, and review and approve periodic progress reports, and the final report and
conclusions. It is our intent to continue to utilize these services to the extent possible, or
an approved alternate if necessary.
Remedial Actions
The decision to initiate remedial action will not be taken without consultation with the
Project Team. The contributing drainage area, weather conditions, or other factors that
could influence the monitoring data will be evaluated to determine if the lack of
performance is a function of the system design and/or sizing, or other external factors. If it
is determined by the Project Team that external factors, including insufficient influent
loads, are the cause for the inadequate or indeterminable performance, then the Project
Team will also evaluate the options of continued monitoring at that particular site, or
relocating the monitoring equipment in order to continue monitoring at an alternate site. In
either case, the Project Team will also evaluate the proposed remedial action(s) and verify
that they represent an appropriate course of action to address the issues for the particular
project.
The current StormFilter System design proposal for compliance with the requirement for
85% average annual removal of Total Suspended Solids (TSS) has.been established as a
volume-based design consisting of cartridges filled with ZPG media and operating at a
specific flow rate of 1 gpm/ft2. The following represents a progression of remedial actions
aimed at adjusting the system function in order to improve the overall performance of the
system:
1. Reduce the specific flow rate to 0.27 gpm/ft2 (2 gpm/cartridge). Laboratory and
field monitoring studies of the StormFilter have demonstrated that reducing the
flow rate yields longer residence time and longer contact time between the
stormwater and the media, and results in improved performance. (CONTECH
2004a, 2006a, 2007b). Reducing the specific flow rate is accomplished by
replacing the 1 gpm/ft2 restrictor disc in the bottom of each cartridge with a smaller
0.27 gpm /ft2 restrictor disc.
2. Replace the ZPG media with progressively finer media. This can represent at least
two remedial actions with alternate media specifications: i) fine perlite to replace
regular perlite, and ii) fine zeolite to replace the regular grade of zeolite. Again,
monitoring studies have demonstrated that the StormFilter performance improves
with a finer gradation of media. (CONTECH 2006b).
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3. Replace the ZPG media with sand (or fine zeolite with a comparable size.
gradation), and provide a site specific Inspection and Maintenance Compliance
Service to the owner to ensure ongoing compliance of the system.
The final remedial action of replacing the ZPG media with sand or comparable zeolite will
generally turn the StormFilter into a vertical siphon actuated sand filter. However, the
surface area requirement for sand filters as required in the NC BMP Manual is larger than
that of a typical StormFilter. This is due to the sand filter design criteria being based on
the permeability of clogged sand (K = 3.5 ft/day). This is appropriate since the media is
placed in a horizontal filter bed geometry that is susceptible to clogging from not only from
the filtered material, but also unsettled material in suspension that that comes to rest on
the sand bed surface as the water slowly filters down (commonly referred to as cake
filtration, which often leads to the occlusion of the sand surface).
The StormFilter, on the other hand, utilizes a hood over the cartridge to protect the vertical
geometry of the filter media, allowing material in suspension to come to rest harmlessly on
the vault floor. In addition, the surface cleansing mechanism of the falling siphon
(described in detail in the Cartridge Operation section) serves to help keep the surface of
the media from occluding. Therefore, while the calculated surface area of the Sand
StormFilter System is less than that of the traditional sand filter, the system performance
is comparable to an appropriately sized sand filter (as a result of comparable media
gradation and specific flow rate). The difference in the systems, however, is potentially
realized in the service life of the media. While the hood and surface cleansing mechanism
may serve to equalize the difference in surface area.
This final stage of remediation should therefore be considered an equivalent to a
traditional sandfilter with no further sampling requirements. CONTECH will develop an
Inspection and Maintenance Compliance Service to ensure continued operation of the
system. The remedial action provides for a BMP replacement to a sandfilter within
StormFilter vault. Therefore, the requirement to provide space for an alternative BMP
should the innovative technology fail is accomplished within the vault footprint.
Irreducible concentration benchmark
In order for permit compliance to be achieved at sites where influent concentrations are
less than 100 mg/l CONTECH recommends that the treatment benchmark of 85% TSS be
clarified to reflect low influent concentrations and the difficulty in achieving an 85%
removal of concentrations less than 100 mg/l. The achievement of an effluent
concentration at or below typical effluent thresholds for waste\ water treatment (20 mg/L)
should not be considered a stormwater permit failure. Performance expectations should
be qualified for the potential for low influent concentrations which will often yield effluent
concentrations near what is considered the irreducible influent concentration for
stormwater treatment practices, generally accepted to be in the range of 20 to 40 mg/I
(Center for Watershed Protection, 2000). The Comparative Performance Summarization,
described below, is one method for providing realistic and appropriate performance
expectations at lower influent concentrations.
Comparative Performance Summarization
Comparative performance summarization evaluates the measured performance of a
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system with respect to BMP performance expectation that take into account reduced
removal efficiencies associated with low influent concentrations. Examples of this method
are found in the Washington State Department of Ecology Guidance for Evaluating
Emerging Stormwater Treatment Technologies (WADOE 2002) and BMP Performance
Expectation Functions (Lenhart, 2007). This guidance specifies the basic treatment
performance goal for TSS as 80 percent removal for influent concentrations that are
greater than 100 mg/I. For influent concentrations less than 100 mg/I, the performance
goal is an effluent concentration of 20 mg/I. This reflects the observed performance of
stormwater treatment practices where removal efficiencies measured as percent will
gradually decrease corresponding to a comparable gradual decrease in the influent EMC
from 100 mg/I to the irreducible concentrations referenced above.
100
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60
40
20
20 40 60 80 100 120 140 160 180 200
Influent TSS EMC (mg/L)
Figure 3. BMP Performance Expectation Function analysis comparing paired efficiency observations to a
line defining expected performance reflecting lower efficiency expectations at low influent
concentrations.
Figure 3 from the Wilmington International Airport General Aviation Apron Expansion Final
Report represents the BMP Performance Expectation Function corresponding to the North
Carolina Coastal Counties performance requirement of 85% removal of TSS. Influent
concentrations of approximately 120 mg/I will reflect performance expectations of 85%
removal, and a corresponding effluent concentration of approximately 20 mg/I. Similarly,
influent concentrations of approximately 40 mg/I will reflect performance expectations of
50% removal, and a corresponding effluent concentration of approximately 20 mg/I,
representing the irreducible load. In North Carolina, the recommended TSS mean EMC
for commercial and services land uses is 54.2 mg/I (NCDWQ 2005). In relation to the goal
for a 70% reduction in TSS (performance expectation at this site), this would yield an
effluent concentration of 3.3 mg/l, which is well beyond the performance capabilities of
any stormwater treatment practice traditional or manufactured. In contrast, an effluent
goal of 20 mg/I would generally represent the limits of treatment to the "maximum extent
practical." Utilizing this comparative performance summarization method, and considering
the measured influent TSS median EMC of 11 mg/I for this study period and
corresponding median effluent EMC estimate would represent acceptable performance
with respect to the performance goals.
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The first StormFilter System PEP evaluation at the Currituck Gas House (CONTECH
2007a) and DWQ's favorable interpretation of the performance data has allowed the
StormFilter to continue in the PEP program with additional installations for compliance
with TSS performance goals. The process of evaluating the performance of the
StormFilter System has provided CONTECH and DWQ with a foundation on which to
evaluate and establish StormFilter system sizing methodologies, design loading
limitations, and other design particulars as outlined herein. As such, the design and sizing
criteria for future installations is based on this StormFilter PEP documentation.
Recommended StormFilter sizing
CONTECH conducted the first PEP monitoring study of the StormFilter at the Currituck
Gas House in Barco, NC (CONTECH 2007a). While the results of that monitoring study
were encouraging, very specific elements of the design were identified for improvement.
Since the PEP program is designed to allow DWQ an opportunity to evaluate the
performance of a technology and develop appropriate permitting criteria, conclusions from
the Currituck monitoring study, combined with conclusive results derived from numerous
other monitoring studies, helped derive the following design and sizing changes for
meeting the treatment objectives and performance goals of the NC Stormwater program.
Total Suspended Solids
Future designs are recommended to be volume-based designs with a full height
downstream wall to prevent any trapped sediment material from being transported
out of the system. In addition to the volume-based sizing recommended above,
future designs are also recommended to be sized with a 1 gpm/ftz specific flow rate.
The following represent specific sizing and design standards for the StormFilter System
for meeting the North Carolina TSS performance goals:
Volume-based sizing;
¦ 1 gpm/ft2 specific flow rate
¦ ZPG media
¦ Full height downstream wall (no internal bypass)
Downstream of detention;
¦ Detention sized for 75% of the WQv
¦ Dead storage sump for sediment retention
- Mass-Load Analysis to determine the minimum number of cartridges;
¦ Annual Rainfall per Appendix 2 of StormFilter submittal (CONTECH
2008a)
¦ Mass load EMC per Appendix 2 of StormFilter submittal (CONTECH
2008a)
¦ 1" (or 1.5") WQv representing 90% of the total annual. rainfall/runoff
volume
¦ Pre-treatment load reduction credit of 30% (based on typical sand fraction
of a silt loam soil material)
* Detention designs may also provide for minimum drawdown time requirements. Project
specific designs will address each requirement as needed.
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Nutrients
One of the notable advantages of an engineered system such as the StormFilter is the
ability to modify the design to address site or watershed specific treatment objectives
and/or performance goals. As noted above, a design enhancement such as reducing the
cartridge flow rate can improve system performance. Similarly, the selection of alternate
filter media can likewise improve performance. Alternate media such as sand; fine zeolite,
or other reactive fine media, along with a further reduction in the specific cartridge flow
rate has been shown to be effective at removing nutrients from stormwater (CONTECH
2006b; 2006c). Therefore, as a continuation of the StormFilter PEP process, additional
monitoring sites in the piedmont area of the state will be identified for further system
monitoring and performance evaluation relative to nutrient treatment objectives.
The criteria listed above for the TSS performance goals will be modified to further reduce
the cartridge flow rate to 0.3 gpm/ft2. In addition, depending on site conditions, and the
status of ongoing research, alternate media will be recommended at the outset, with the
option to further modify the media as measured performance may justify.
Sampling criteria
We are currently in the very early stages *of working with at least one locality on a
monitoring project plan that will require careful consideration of alternative monitoring
protocols in order to accommodate the site conditions. Again, we are committed to
continuing the communication with your office to ensure that, as much as possible, we
maintain consistency with the DWQ PEP requirements as we move forward. Therefore,
we would like to respectfully request the following changes to the StormFilter Preliminary
Evaluation Period Requirements as discussed in our recent meeting.
1. make first flush and grab samples an option, and not a requirement. These
samples are logistically difficult to obtain given the on-site manpower
requirements. Also, the collection of these samples may negatively impact the
ability to obtain adequate storm coverage with the automated flow-paced
composite sampling. Finally, these samples are of limited value in measuring the
performance of a BMP with regard to influent and effluent sampling. These
samples, on the other hand, can be very useful in characterizing the condition of
the contributing drainage area or a snapshot assessment of the BMP effluent.
Therefore,.this should be an optional sampling criterion to be considered on a case
by case basis during the development of the monitoring Project Plan.
2. the list of required monitored parameters is to be determined by the specific
treatment objectives and performance goals of the project. Additional parameters
can be added on a case by case basis through negotiations with the permit
authority. CONTECH will often choose to analyze for all the listed parameters
regardless of the project requirements. However, there are times when this can
lead to added costs with very little benefit (i.e. bacteria sampling).
3. make the 72 hour antecedent dry period a guideline and not a requirement.
Smaller low intensity events that do not generate measureable runoff should not
inhibit the sampling of larger measurable runoff generating storms events.
Thank you in advance for your consideration of this submittal and concurrence with the
items identified throughout and discussed in our meeting last month. The StormFilter has
www. contechstormwater.com
The Stormwater Management Vf CON SPANe
CMP DETENTION SYSTEMS C61 StormFilter VOrteChS° C E rENTION SY97EMS
SMRIVP,, °rE
SbLUTIQNSI?.
been actively engaged in several performance verification and testing protocols, and is the
only system approved through both the Washington (Technology Assessment Protocol -
Ecology) and New Jersey (Stormwater BMP Demonstration Tier II Protocol for Interstate
Reciprocity - TARP) programs. We are extremely confident that we will achieve the North
Carolina stormwater treatment performance goals and look forward to our next
installations and the ultimate completion of the PEP program requirements.
As always we are happy to provide any necessary support and look forward to answering
any and all questions that may arise as you review this document. Please feel free to
contact us at anytime.
Respectfully,

Dionne Driscoll
Regional Regulatory Manager
Contech Stormwater Solutions
3640 Davinci Court, Suite 450
Norcross, GA 30092
404-561-7958
driscolldO,contech-cpi.com
www.contechstormwater.com
North Carolina DWQ concurrence:
7 iL i o 9
Mr. Kenneth B. Pickle
Environmental Engineer
Stormwater and General Permits Unit
North Carolina Department of Environment & Natural Resources
Division of Water Quality
www.contechstormwater.com
CONT ? Tho Stormwata Managomont t ?(? (?? CON SPAN`
CMP DETENTION SYSTEMS StormFilter° V,,, V(? orAlec1J CETM- ONSYSTEMS
ivv
,\ if Ur rc> lie
?' i it
STORMWATER
sal?uT?oNS,NO.
References:
Center for Watershed Protection; Schueler, T. R. "Irreducible Pollutant Concentrations Discharged
from Stormwater Practices" Technical Note #75. Watershed Protection Techniques, 2(2), 369-372.
from The Practice of Watershed Protection, 2000.
CONTECH Stormwater Solutions Inc. (2002) Influence of analytical method, data summarization
method, and Particle size on total suspended solids (TSS) removal efficiency (Report No. PE-
C063). Portland, Oregon: Author.
CONTECH Stormwater Solutions Inc. (2004a) Evaluation of the Stormwater Management
StormFilter® for the removal of SIL-CO-SIL®106, a standardized silica product: ZPGTM
StormFilter cartridge at 28 L/min (7.5 gpm) (Report No. PE-E062)
CONTECH Stormwater Solutions Inc. (2004b) Performance of the Stormwater Management
StormFilter Relative to Ecology Performance Goals for Basic Treatment (Report No. PE-E072)
Portland, Oregon: Author.
CONTECH Stormwater Solutions Inc. (2005) Evaluation of the Lifecycle Loading Characteristics
ofthe Stormwater Management StormFilter® Cartridge: ZPG StormFilter cartridge at 28 L/min-(7.5
gpm) and Sandy Loam (Report No. PE-F090). Portland, OR: Author
CONTECH Stormwater Solutions Inc. (2006a) Evaluation of The Stormwater Management
StormFilter® for the removal of Sil-Co-Sil®106, a standardized silica product: ZPGTM StormFilter
cartridge at 56 Umin (15 gpm) (Report No. PE-G011)
CONTECH Stormwater Solutions Inc. (2006b) Statistical Comparison of Perlite/CSF,
Perlite/MetalRx, and ZPGTM Combination Media for Suspended Solids Removal at 28
L/min/cartridge (Report No. PE-F060) Portland, Oregon: Author
CONTECH Stormwater Solutions Inc. (2006c) Airport Way Volume StormFilter Field Evaluation
Quarterly Performance Summary: November 2006 through January 2007 (Report No. PE-H010)
CONTECH Stormwater Solutions Inc. (2006d) Greenville Yards Stormwater treatment System
Field Evaluation. Stormwater Management Storm Filter with ZPG media at 57 L/min/cartridge
(Report No. PE-G081) Portland, OR: Author.
CONTECH Stormwater Solutions Inc. (2007a) The Stormwater Management StormFilter
Preliminary Evaluation Period, Currituck Gas House Final Report. Portland, OR: Author.
CONTECH Stormwater Solutions Inc. (2007b) Summary of Field Performance Evaluation of the
Stormwater Management StormFilter for Removal of Total Suspended Solids (Report No. RS-
0231) Portland, Oregon: Author. Copy enclosed in Appendix 4.
CONTECH Stormwater Solutions Inc. (2007c) Wilmington International Airport General Aviation
Apron Expansion Vortechs® Model 7000 Field Evaluation Project Plan . Portland, Oregon: Author.
CONTECH Stormwater Solutions Inc. (2008a) Preliminary Evaluation Period
for the North Carolina Division of Water Quality March, 2008; REVISED July, 2008
CONTECH Stormwater Solutions Inc. (2008b). Vortechs® system Guide Operation, Design,
Performance and Maintenance Portland, Oregon: Author. Available
online:http://www.contechcpi.com/medialassets/asset/file_name/461 /vx_guide. pdf
www.contechstormwater.com
1- N ¦VC i The Stormwater Managemen t
ON SY ? CCD„ ? NNortechs- CON SPAN°
CMG DETENTION SYSTEMS Sto rm Fi Iter° of TENn°N SYSTEMS
M Vft
ON ff
MATER
so?.uYic?l?s,r?.
CONTECH Stormwater Solutions Inc. (2009) The CONTECH Stormwater Solutions Vortechs®
System Preliminary Evaluation Period Wilmington International Airport General Aviation Apron
Expansion Final Report. Portland, Oregon: Author.
Lenhart, James (2007) BMP Performance Expectation Functions - A Simple Method for Evaluating
Stormwater Treatment BMP Performance Data, 9th Biennial Stormwater Research and Watershed
Management Conference, Orlando, FL, April, 2007
North Carolina Department of Environment and Natural Resources Division.of Water Quality
(NCDWQ). (2005) Updated Draft Manual of Stormwater Best Management Practices. Available
Online:
http://h2o.enr.state.nc,us/su/documents/NCDENRBMPManuaIFINAL-July2005-appendices 000.p
df
Stormwater Management Inc. (SMI 1999) Sediment Loading on a Perlite Filled StormFilterTM
Cartridge. B. Wigginton; S. De Ridder
United States Environmental Protection Agency (USEPA). (2002). Urban Stormwater BMP
Performance Monitoring: A Guidance Manual for Meeting the National Stormwater BMP Database
Requirements (EPA-821-B-02-001). Washington, D.C.: Author. Available Online:
http://epa.gov/waterscience/stormwater/montcomplete.pdf
Washington State Department of Ecology (WADOE). (2002). Guidance for Evaluating Emerging
Stormwater Treatment Technologies: Technology Assessment Protocol-Ecology (Publication
Number 02-10-037). Olympia, Washington: Author. Available Online:
http//www.ecy.wa.gov/pubs/0210037.pdf
www. con tech stormwater.com
CONTEM CCD T ta Stormwater Management Vortechs® CON SPAN'
CMPDETENTIONSYSTEMS x StormFilter DE TENTONSYSTENAS
3S
Pre-Development Dollar 5L
General Lot
Total Pre Development
1S
Post/Pre Development
By Pass
(4S
Post Development
Dollar General Lot
6L
9S
Total Post Development
Post Developed
Untreated (On Lot)
8S
Post/Pre Development
By Pass
SubCa Reach on Link Drainage Diagram for 2933 hydrocad
Prepared by HensonFoley, Printed 5/16/2011
HydroCAD®9.10 sin 06652 0 2010 HydroCAD Software Solutions LLC

2933 - Boone Dollar General
2933 hydrocad
Prepared by HensonFoley Printed 5/16/2011
HydroCADO 9.10 s/n 06652 @2010 HydroCAD Software Solutions LLC Page 2
Area Listing (all nodes)
Area
(acres) CN Description
(subcatchment-numbers)
0.500 58 Woods/grass comb., Good, HSG B (9S)
1.580 60 Woods, Fair, HSG B (3S)
45.840 68 1 acre lots, 20% imp, HSG B (1 S, 8S)
1.080 92 Urban commercial, 85% imp, HSG B (4S)
49.000 68 TOTAL AREA
2933 - Boone Dollar General
2933 hydrocad
Prepared by HensonFoley Printed 5/16/2011
HydroCADO 9.10 s/n 06652 © 2010 Hydr2CAD Software Solutions LLC Paae 3
Soil Listing (all nodes)
Area Soil Subcatchment
(acres) Group Numbers
0.000 HSG A
49.000 HSG B i S, 3S, 4S, 8S, 9S
0.000 HSG C
0.000 HSG D
0.000 Other
49.000 TOTAL AREA
2933 - Boone Dollar General
2933 hydrocad Type II 24-hr IO-Year Rainfall=6.90"
Prepared by HensonFoley Printed 5/16/2011
HydroCADO 9.10 s/n 06652 © 2010 HydroCAD Software Solutions LLC Paae 4
Time span=5.00-20.00 hrs, dt=0.05 hrs, 301 points
Runoff by SCS TR-20 method, UH=SCS
Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method
Subcatchment IS: Post/Pre Development Runoff Area=22.920 ac 20.00% Impervious Runoff Depth>3.04"
Flow Length=2,892' Tc=21.4 min CN=68 Runoff=80.94 cfs 5.811 of
Subcatchment 3S: Pre-Development Dollar Runoff Area=1.580 ac 0.00% Impervious Runoff Depth>2.29"
Flow Length=222' Slope=0.2340'/' Tc=12.7 min CN=60 Runoff=5.46 cfs 0.302 of
Subcatchment 4S: Post Development Runoff Area=1.080 ac 85.00% Impervious Runoff Depth>5.57"
Tc=5.0 min CN=92 Runoff= 10.34 cfs 0.501 of
Subcatchment 8S: Post/Pre Development Runoff Area=22.920 ac 20.00% Impervious Runoff Depth>3.04"
Flow Length=2,892' Tc=21.4 min CN=68 Runoff=80.94 cfs 5.811 of
Subcatchment 9S: Post Developed Runoff Area=0.500 ac 0.00% Impervious Runoff Depth>2.12"
Tc=5.0 min CN=58 Runoff=2.09 cfs 0.088 of
Link 5L: Total Pre Development Inflow=84.82 cfs 6.113 of
Primary=84.82 cfs 6.113 of
Link 6L: Total Post Development Inflow=82.88 cfs 6.400 of
Primary=82.88 cfs 6.400 of
Total Runoff Area = 49.000 ac Runoff Volume = 12.513 of Average Runoff Depth = 3.06"
79.42% Pervious = 38.914 ac 20.58% Impervious = 10.086 ac
2933 - Boone Dollar General
2933 hydrocad Type II 24-hr 10-Year Rainfall=6.90"
Prepared by HensonFoley Printed 5/16/2011
HydroCADO 9.10 s/n 06652 @ 2010 Hydr2CAD Software Solutions LLC Page 5
Summary for Subcatchment IS: Post/Pre Development By Pass
Runoff = 80.94 cfs @ 12.15 hrs, Volume= 5.811 at, Depth> 3.04"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs
Type II 24-hr 10-Year Rainfall=6.90"
Area (ac) CN Description
22.920 68 1 acre lots, 20% imp, HSG B
18.336 80.00% Pervious Area
4.584 20.00% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
10.3 100 0.0800 0.16 Sheet Flow, overland
Woods: Light underbrush n= 0.400 P2= 4.59"
8.4 1,780 0.0560 3.55 Shallow Concentrated Flow, SHALLOW CONCENTRATED
Grassed Waterway Kv= 15.0 fps
1.2 562 0.0820 7.70 15.40 Channel Flow, CHANNEL 1
Area= 2.0 sf Perim= 5.0' r= 0.40'
n= 0.030 Earth, grassed & winding
1.5 450 0.0580 4.86 9.71 Channel Flow, CHANNEL 2
Area= 2.0 sf Perim= 5.0' r= 0.40'
n= 0.040 Earth, cobble bottom, clean sides
21.4 2,892 Total
Subcatchment 1S: Post/Pre Development By Pass
Hydrograph
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -I- - - - - --- - - - - - - - - - - - - - - - - - - - -
90 ---- - - --------a----I ---II
----{

85 I
I
--------1-------- ----I---- 80.94 cfs I--------- I ----- I ----

80 ---II---- -II-;2?- ra -X ar--
--------- ---- ----------- Type
75 - - ---- - --I --- ---I_

I --;- I ---
- - - ----II ---, - --- RajinfalC=fi
?iO
"-
70 .
s5

----II----
- - - - - - - - --------- I --- - - _ I- - HUnoff Atea=22 X2{0 -ac- -
60
55
I unoff
Vol!ume;;
Al f
I'
I'
II
II
----
-
-
I---- ----
--- ---- ----
I-- --
I-
,
50
45 - ------1----I-- - ----IL------ ------- -Rtinoff Dep#h?.3.04"-
------------
---------- '--------------'----
- --
? 40 -II
---- --- _Flow Lengf =2}80-
---- - - - -
----- ------
1 I ? I
35
- - - { - - - -I- - - - 7 ----
- - -I- -
----- ----7----r----li- ??i?L .4 rn1rr
30 '
'

25 ___
----
----- --------- t I____-____Y_-_--___t_-- ii?/8'_
20 F

15 I_ 1- 1
--------1----'---
L --- --- -' --- --------J----

10 I
I I I I I I I I I I
---J ---- --------1----L----1- -1-- ---L--------1----'---- ----
5
0
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)
2933 - Boone Dollar General
2933 hydrocad Type II 24-hr 10-Year Rainfall=6.90"
Prepared by HensonFoley Printed 5/16/2011
HydroCADO 9.10 s/n 06652 @ 2010 HydroCAD Software Solutions LLC Page 6
Summary for Subcatchment 3S: Pre-Development Dollar General Lot
Runoff = 5.46 cfs @ 12.05 hrs, Volume= 0.302 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs
Type II 24-hr 10-Year Rainfall=6.90"
Area (ac) CN Description
1.580 60 Woods, Fair, HSG B
1.580 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
12.7 222 0.2340 0.29 Sheet Flow, Overland
Woods: Light underbrush n= 0.400 P2= 4.59"
Subcatchment 3S: Pre-Development Dollar General Lot
Hydrograph
--------------------------------------------------------------------
noff
6-
6 cfs
5.4
r---- --------- ---- ?'?----7-Type J?24-?u'1b-Year--
5 !Rainfall^6.90"
---- ---- ;---- --- -- ---- ,RunoffArea=1.5801ac--
4 Runoff Volume-0302 of
--- -- ---! --Runo#f-Dopth>1. 9"--
3 3 Flow Length=42'
---- r---- 7-------- -- --- T---- Slope=0.340 T__
2
Tc=12.7 min
-- i---- ------- --- - ---ACN=:60--
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)
2933 - Boone Dollar General
2933 hydrocad Type II 24-hr 10-Year Rainfall=6.90"
Prepared by HensonFoley Printed 5/16/2011
HydroCAD@ 9.10 s/n 06652 @ 2010 HydroCAD Software Solutions LLC Page 7
Summary for Subcatchment 4S: Post Development Dollar General Lot
[49] Hint: Tc<2dt may require smaller dt
Runoff = 10.34 cfs @ 11.95 hrs, Volume= 0.501 at, Depth> 5.57"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs
Type II 24-hr 10-Year Rainfall=6.90"
Area (ac) CN Description
1.080 92 Urban commercial, 85% imp, HSG B
0.162 15.00% Pervious Area
0.918 85.00% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry, Post Development
Subcatchment 4S: Post Development Dollar General Lot
Hydrograph
7 7-
1
10.34 cfs Runoff
- - - - - - -
- - - - - - - - - - I- - - - - -Y-ID- - - -?- - - - - - - - I - - - -
10 - ;T? a II 24-Mr 1 -Y ear
9 --- --- -- -- Ra'infaMi6.90"-
8 -- Runbff-Area=T.-0$0 ac
7 -------- ---- - --- Ru'-oif`Vol;ume_O.50taf-
6 Runoff Depth?-5.5T' -
[L- 5.
_ - ------ -- -- -- ---- ,---- TYc-3':0-rain -
---'---- ---'-- --- ---- -- ----1--- --------1---
4 OW19L
-- -
3
2
- - - - - 1 - - - - ' - - - - - - - - L - - - -'- - - - - 1 - - - - ? - - - - - - 1 - - - - - - - - - - - - -
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)
2933 - Boone Dollar General
2933 hydrocad Type II 24-hr 10-Year Rainfall=6.90"
Prepared by HensonFoley Printed 5/16/2011
HydroCADO 9.10 s/n 06652 @ 2010 HydroCAD Software Solutions LLC Paae 8
Summary for Subcatchment 8S: Post/Pre Development By Pass
Runoff = 80.94 cfs @ 12.15 hrs, Volume= 5.811 at, Depth> 3.04"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs
Type II 24-hr 10-Year Rainfall=6.90"
Area (ac) CN Description
22.920 68 1 acre lots, 20% imp, HSG B
18.336 80.00% Pervious Area
4.584 20.00% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
10.3 100 0.0800 0.16 Sheet Flow, overland
Woods: Light underbrush n= 0.400 P2= 4.59"
8.4 1,780 0.0560 3.55 Shallow Concentrated Flow, SHALLOW CONCENTRATED
Grassed Waterway Kv= 15.0 fps
1.2 562 0.0820 7.70 15.40 Channel Flow, CHANNEL 1
Area= 2.0 sf Perim= 5.0' r= 0.40'
n= 0.030 Earth, grassed & winding
1.5 450 0.0580 4.86 9.71 Channel Flow, CHANNEL 2
Area= 2.0 sf Perim= 5.0' r= 0.40'
n= 0.040 Earth, cobble bottom, clean sides
21.4 2,892 Total
Subcatchment 8S: Post/Pre Development By Pass
Hydrograph
- - - - - - - - - - - - - - - - - - - - - - - - - - - - ? - - - - I - - - - 4 - - - - - - - -I- - - - - - - -I- - - - - - - -
90
i .____----,----L--------;----I---
85 ___'___-1 1 1 1 1 ___ ¦Runoff
-- ------- 80.94 cfs -1---- ----L-------- ----1---- ----
80 , ----III---- ----III--------------III--- ---III----!1Ty0e-u-IN-ir 10-XeaK-
75 ---= --1----1-- -1,
70 ---Rain falf=fi.
----r---T----!----,----I?----II--- ---1----?----r 1 r ? ,----
65 - - - -1----------------------- --- --- Runoff -Atea-.42.92-0 -ae -
II- -
60 -- I I I I 1 1
55 ---11-Ru-off'Vol5.1' af_
50 -'--------- L 11 -- ------- ---- 1-
., 1 1 1 1 1 1 1 Runoff Depth,>8.04111
3 45 -----------------!- ------'-- -------
0 40
- '1I - - - Flb?e? L ngth=2}892' -
?- ----1----;--------------------
35 - -
-- ------------- -- -- - ,----r--- ;:4-Mn-
30
25 r--------7----r---- I-- ? -I ---- Y----r------------
----1---- -
20 \I
--------------------- L----I-- + -------------------------?----
15 _ --------1----L----1- 1- ----1---- ----1----1--------J----
1 1 1 1 1 1 1 1 1 1
--- '
1 1 1 1 1 1 I 1 1
5
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)
2933 - Boone Dollar General
2933 hydrocad Type II 24-hr 10-Year Rainfall=6.90"
Prepared by HensonFoley Printed 5/16/2011
HydroCADO 9.10 s/n 06652 @ 2010 HydroCAD Software Solutions LLC Paae 9
Summary for Subcatchment 9S: Post Developed Untreated (On Lot)
[49] Hint: Tc<2dt may require smaller dt
Runoff = 2.09 cfs @ 11.96 hrs, Volume= 0.088 af, Depth> 2.12"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs
Type II 24-hr 10-Year Rainfall=6.90"
Area (ac) CN Description
0.500 58 Woods/grass comb., Good, HSG B
0.500 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry, Real TC less than 5 min. so use 5 min
Subcatchment 9S: Post Developed Untreated (On Lot)
Hydrograph
2.09 cfs
N I I I I I
1
LL
I I I I
I I II I II
I I I
I I I I I I
I I I I I
I I I I I I
I I I I I I
III III III III III III .
---- -type ll-I IhIr-10---Y0ar
Rainfa11t6.9i0"
I
Runoff Area=0.500 'ac
Runoff! VoIIIIume=0.11086 of
Runoff Depth?2.1i2"
- - c-56 Min
I I
ON=1158
I I I I I I I
I I I I I I I
I I I I I I I
I I I I I I I
I I I I I I
I I I I I I
¦ Runoff
10 11 12 13 14 15 16 17 18 19 20
Time (hours)

2933 - Boone Dollar General
2933 hydrocad Type II 24-hr IO-Year Rainfall=6.90"
Prepared by HensonFoley Printed 5/16/2011
HydroCAD@ 9.10 s/n 06652 © 2010 HydroCAD Software Solutions LLC Paae 10
Summary for Link 51.: Total Pre Development
Inflow Area = 24.500 ac, 18.71% Impervious, Inflow Depth > 2.99" for 10-Year event
Inflow = 84.82 cfs @ 12.14 hrs, Volume= 6.113 of
Primary = 84.82 cfs @ 12.14 hrs, Volume= 6.113 af, Atten= 0% Lag= 0.0 min
Primary outflow = Inflow, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs
Link 51.: Total Pre Development
Hydrograph
I - - T -- ? --?-- ¦Inflow
- - -- --- - 432 S ------ - --- -
-- - - - ¦Primary
90

' 84.82 cfs
--- -
' '
Anftow Ar?e?la-24.5?00-a--
85 - ---- --------- -- - - - -- - -
80 - - - - -
75 -- - ---
---------- ----- ----------- ----- -
70
-
---- --------
--------------------
65 -------------------------' -- ----------------------'-
60 -------------------------- ' ---''----'-----'----'----=----'----'---
a 55 ---1--------1--------L-- ---------1--------1--------' ---
50 1--------1-------L- ---L---1 ---'- --1-- ----L---
0 45 --------1----'---- -- --- ---1----1----1-- -'---- ---
---
u- 40
35 r
30
25

20 }

15
--,- - ---- --------r--- - - -----+- -----
10

5
0
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)
r
2933 - Boone Dollar General
2933 hydrocad Type II 24-hr IO-Year Rainfall=6.90"
Prepared by HensonFoley Printed 5/16/2011
HydroCADO 9.10 s/n 06652 @ 2010 HydroCAD Software Solutions LLC Paae 1 1
Summary for Link 6l: Total Post Development
Inflow Area = 24.500 ac, 22.46% Impervious, Inflow Depth > 3.13" for 10-Year event
Inflow = 82.88 cfs @ 12.14 hrs, Volume= 6.400 of
Primary = 82.88 cfs @ 12.14 hrs, Volume= 6.400 af, Atten= 0% Lag= 0.0 min
Primary outflow = Inflow, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs
Link 6L: Total Post Development
Hydrograph

----------I-- ¦Inflow
90 ?' ¦ Primary

65 - -------------------
-
82.88 its Inflow - Area-24-5100 ac
80

75
'
:
---t----1----t----1----r-- !
.! -1----r--- ------.--r----I----r- -
70

65 '
.
, --- t ---- I----t----I----r-- _?----r--t----1----t----r--r----
60
/
i
i ----1----I----t----I---- -- --
------------------
.-. 55

v 50
?
.
i '_--i------__t--------+-- -'"---Y-'------t--'-----r.__-.
45 3 1 1
_ _ _ _ r _
LL
40

35
,
30
'
1 1

25
'
---y--------r----1---r-- --- r--r--- I----t----I----r---
20
1

15 ?
-

10 ----
r --Y
r -- - --
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)