Atwood North_Comment Response MassDEP 2-27-20.pdf
53 Southampton Road • Westfield, MA 01085-5308 • Tel 413.562.1600
www.tighebond.com
N5037001
February 27, 2020
Mark Stinson, Wetlands Circuit Rider
Massachusetts Department of Environmental Protection
Western Region, Bureau of Water Resources
Division of Wetlands and Waterways
436 Dwight Street
Springfield, MA 01103
Re: Northwood Development II Project
23 Atwood Drive, Northampton, Massachusetts
Response to Comments
Dear Mark,
In November 2019, Tighe & Bond submitted to your office a Notice of Intent for the Northwood
Development II Project located at 23 Atwood Drive in Northampton, Massachusetts. A
Notification of Wetlands Protection Act File Number with comments was issued on November
25, 2019. On January 28, 2020, Tighe & Bond submitted to your office a revised Notice of
Intent.
This letter summarizes Tighe & Bond’s responses to MassDEP’s comments regarding the
Notice of Intent for the above referenced project. MassDEP’s comments are listed below in
Italics, followed by the response in bold font.
Project Description
Comment 1: What is the current status of compliance with the previous Orders on the site?
T&B Response: We understand that the previous Order of Conditions expired as of
June 2018. At the recommendation of Sarah LaValley, Northampton Conservation
Agent, a new Notice of Intent has been filed in order to permit the outstanding
work required to complete the project and comply with the original Order of
Conditions, as well as any new Conditions requested of the Commission.
Comment 2: Plans should state which elevation datum is being used. The NOI narrative
states all elevations are based on NGVD29 but that should also be on the plans if not already
there.
T&B Response: The vertical datum, NAVD88, is indicated on Sheet G-100 of the
permit drawings. Limits of 100-year flooding established by the flood insurance
study of the Connecticut River are at elevation 123 feet NGVD29. This value was
converted from 123 feet NGVD29 to 122.33 feet for use in the NAVD88 datum.
Additional clarification of the required datum and elevation conversions will be
provided on the revised drawings.
Comment 3: The commission should review the filing fee. Each activity is its own fee.
T&B Response: We acknowledge that the revised scope of work may require an
additional filing fee. We default to the Commission for resolution.
Comment 4: All stormwater BMP’s must be designed, constructed, operated and maintained
per the Stormwater Handbook, Volume 2, Chapter 2. The simplest thing to do is to cut and
- 2 -
paste the relevant pages of the Handbook into the Stormwater Report and use that to
describe compliance.
T&B Response: The Operations and Maintenance manual previously approved by
the City of Northampton under the Stormwater Management Permit is still valid,
and no changes to that manual are proposed at this time.
Comment 5: The MASTEP web site is no longer available for review of alternative BMPs.
MassDEP suggests that a comparable alternative resource that may be considered to
demonstrate compliance with TSS removal may be found at the following link:
https://www.nj.gov/dep/stormwater/treatment.html
T&B Response: Based on information provided through the New Jersey
Corporation for Advanced Technology (NJCAT), the Continuous Deflective
Separator (CDS) Unit by CONTECH Stormwater Solutions, Inc. provides a certified
TSS removal rate of 50%. This value is reflected in our TSS removal calculations.
The CDS verification report is attached to this response.
If you have any questions, or if you require additional information, please contact me at (413)
875-1301.
Very truly yours,
TIGHE & BOND, INC.
Brian Huntley, P.E.
Senior Project Manager/Senior Associate
Enclosures: NJCAT CDS Verification Report
Copy: Travis Ward, Development Associates
Sarah LaValley, Northampton Conservation Agent
\\tighebond.com\data\data\projects\h\h1363\atwood north\permits\response to comments february 2020\atwood
north_comment response massdep 2-24-20.docx
NJCAT TECHNOLOGY VERIFICATION
Continuous Deflective Separator (CDS®)
Stormwater Treatment Device
(For Models that meet New Jersey’s Unique Sizing Requirements)
Contech Engineered Solutions LLC
September, 2014
(Revised Table A-2 January 2017)
i
TABLE OF CONTENTS
List of Figures ii
List of Tables iii
1. Description of Technology 1
2. Laboratory Testing 2
2.1 Test Setup 2
2.2 Test Sediment 6
2.3 Removal Efficiency Testing Procedure 7
2.4 Scour Testing Procedure 8
3. Performance Claims 9
4. Supporting Documentation 9
4.1 Test Sediment PSD Analysis - Removal Efficiency Testing 10
4.2 Removal Efficiency Testing 11
4.3 Test Sediment PSD Analysis - Scour Testing 23
4.4 Scour Testing for Online Installation 24
5. Design Limitations 26
6. Maintenance Plans 28
7. Statements 29
8. References 37
Verification Appendix 38
ii
List of Figures
Page
Figure 1 Schematic Representation of the CDS Solid Separation Mechanism ................1
Figure 2 Graphic of Typical Inline CDS Unit and Core Components .............................2
Figure 3 Schematic of Test Unit.......................................................................................3
Figure 4 Schematic of TSS Removal Efficiency Laboratory Setup .................................4
Figure 5 Schematic of Scour Testing Laboratory Setup ..................................................6
Figure 6 Comparison of the Mean Contech Test Sediment PSD to the NJDEP Removal
Efficiency Test Sediment PSD Specification ..................................................11
Figure 7 Comparison of Contech Scour Test Sediment PSD to NJDEP Scour Sediment
PSD Specification ............................................................................................24
iii
List of Tables
Page
Table 1 Removal Efficiency Sediment Particle Size Distribution Analysis .................10
Table 2 Summary of CDS-4 25% MTFR Laboratory Test ...........................................12
Table 3 CDS-4 25% MTFR Feed Rate Calibration Sample Results ............................12
Table 4 CDS-4 25% MTFR Background and Effluent Sample Results ...................... 13
Table 5 CDS-4 25% MTFR QA/QC Parameters ......................................................... 13
Table 6 Summary of CDS-4 50% MTFR Laboratory Test .......................................... 14
Table 7 CDS-4 50% MTFR Feed Rate Calibration Sample Results ........................... 14
Table 8 CDS-4 50% MTFR Background and Effluent Sample Results .......................15
Table 9 CDS-4 50% MTFR QA/QC Parameters ......................................................... 15
Table 10 Summary of CDS-4 75% MTFR Laboratory Test ...........................................16
Table 11 CDS-4 75% MTFR Feed Rate Calibration Sample Results ............................16
Table 12 CDS-4 75% MTFR Background and Effluent Sample Results ...................... 17
Table 13 CDS-4 75% MTFR QA/QC Parameters ......................................................... 17
Table 14 Summary of CDS-4 100% MTFR Laboratory Test ........................................ 18
Table 15 CDS-4 100% MTFR Feed Rate Calibration Sample Results ......................... 18
Table 16 CDS-4 100% MTFR Background and Effluent Sample Results .....................19
Table 17 CDS-4 100% MTFR QA/QC Parameters ....................................................... 19
Table 18 Summary of CDS-4 125% MTFR Laboratory Test ........................................ 20
Table 19 CDS-4 125% MTFR Feed Rate Calibration Sample Results ......................... 20
Table 20 CDS-4 125% MTFR Background and Effluent Sample Results .....................21
Table 21 CDS-4 125% MTFR QA/QC Parameters ....................................................... 21
Table 22 Annualized Weighted TSS Removal of the CDS-4 Tested in Accordance with the
NJDEP HDS Protocol at a MTFR of 0.93 cfs ................................................ 22
Table 23 Results of Scour Testing Sediment Particle Size Distribution Analysis......... 23
Table 24 Concentrations of Background Samples during CDS Scour Testing ............. 25
iv
Table 25 Results of CDS-4 Online Scour Testing at 201% of the MTFR .....................26
1
1. Description of Technology
The CDS is a stormwater treatment device intended to remove pollutants, including suspended
solids, trash and debris and floating oils from stormwater runoff. The CDS unit is typically
comprised of a manhole that houses flow and screening controls designed around patented,
continuous deflective separation technology. Figure 1 is a schematic representation of the solid
separation mechanism of the CDS technology.
Figure 1 Schematic Representation of the CDS Solid Separation Mechanism
Stormwater runoff enters the CDS unit’s diversion chamber where the diversion weir guides the
flow into the unit’s separation chamber and pollutants are removed. The separation and
containment chamber consist of a containment sump in the lower section and an upper separation
section. Gross pollutants are separated within the chamber using a perforated screen plate
allowing the filtered water to pass through to a volute return system and thence to the outlet pipe.
The water and associated gross pollutants contained within the separation chamber are kept in
continuous motion by the energy generated by the incoming flow. This has the effect of
preventing the separation plate (screen) from being blocked by the gross solids separated from
the inflow. The heavier solids ultimately settle into the containment sump. Figure 2 is a
schematic representation of a typical CDS unit including critical components. For more details
on the functionality of the CDS including drawings, videos and maintenance procedures please
visit http://www.conteches.com/Products/Stormwater-Management/Treatment/CDS.aspx
The primary purpose of this verification testing was to establish the ability of the CDS to remove
suspended solids from runoff as specified in the testing requirements detailed in the “New Jersey
Department of Environmental Protection Laboratory Protocol to Assess Total Suspended Solids
Removal by a Hydrodynamic Sedimentation Manufactured Treatment Device” (NJDEP HDS
Protocol) dated January 25, 2013 (NJDEP 2013a). In particular, the CDS was tested to
determine the maximum operating rate that would enable retention of more than 50% of the
“NJDEP Particle Size Distribution” as calculated using the weighted annualized formula that is
described in Appendix A of the NJDEP HDS Protocol. Since the CDS is most effective at
removing the coarser fraction of the suspended solids load it is recommended that the CDS be
used as the first component of a treatment train.
2
Figure 2 Graphic of Typical Inline CDS Unit and Core Components
2. Laboratory Testing
All TSS removal efficiency testing for this project was carried out at Contech’s Scarborough,
Maine laboratory under the direct supervision of FB Environmental Associates Inc. (FB). FB is
a Portland, Maine based environmental consulting firm with past experience in a diverse suite of
stormwater quality projects including past oversight of manufactured BMP testing initiatives. All
water quality samples collected during this testing process were analyzed by Maine
Environmental Laboratory, which is an independent analytical testing facility. Since Maine
Environmental Laboratory does not conduct particle size analysis, and an alternate qualified
facility was not identified locally, all particle size distribution (PSD) analysis was completed in-
house at Contech’s laboratory under the direct supervision of FB for the duration of all PSD
analysis.
2.1 Test Setup
A CDS-4 Model (4 ft. diameter) unit was tested in accordance with the NJDEP HDS Protocol. A
schematic of the CDS-4 unit is shown in Figure 3. The CDS-4 test unit did not have a sediment
weir, as traditionally units sold in NJ have had in the past. (Note: Contech plans to move away
from units with a sediment weir.) The CDS-4 is a commercially available unit with a 2 ft
diameter x 1.5 ft high 2400 micron perforated screen plate and is offered in New Jersey and other
3
Figure 3 Schematic of Test Unit
4
areas that formally adopt New Jersey’s unique sizing requirements. Since New Jersey has very
specific criteria in place that govern scaling and determination of treatment flow, as well as a
unique weighted 50% removal efficiency calculation tied to historical New Jersey rainfall
measurements, CDS models have been specifically tailored to comply with these requirements.
Like many technologies, different CDS model configurations are available in different regions
depending on local sizing and performance criteria.
Total Suspended Solids Removal Efficiency Laboratory Setup
The laboratory CDS-4 prototype is housed in a 4 ft. diameter cylindrical aluminum tank with a
depth of 4.7 ft. below the inlet and outlet inverts to the sump floor. These dimensions are
consistent with the commercially available CDS-4. The CDS-4 was TSS removal efficiency
tested in a closed loop, re-circulatory laboratory system that is detailed in Figure 4. Inlet and
outlet piping consists of 12 in. diameter schedule 40 PVC. Water enters the inlet pipe 12 ft.
upstream from the test unit and the test sediment is dry fed through a 6 in. port located 6 ft.
upstream from the test unit. Treated effluent is able to freely discharge through a downturned 90
degree elbow into an aluminum catch tank. The catch tank is configured with two filter
partitions that filter remaining fines from the effluent prior to recirculation in order to maintain
background concentrations at levels less than 20 mg/L. The first partition consists of 24-1 um
nominal rated pre-filter bags while the second partition consists of 24-0.5 um rated primary filter
bags. Filtered water is re-circulated into the 12 in. inlet pipe through a 6 in. schedule 40 PVC
line via a 10 hp pump. Flows are controlled by a 6 in. gate valve and monitored by a SeaMetrics
Online Magmeter (model WMX104) coupled with SeaMetrics model EX201 flow computer.
CDS-4
Figure 4 Schematic of TSS Removal Efficiency Laboratory Setup
5
Scour Test Laboratory Setup
Concerns were raised during the public comment review process on the CDS December 2013
posted verification report relative to the online scour testing procedure followed for the CDS-4
during testing originally completed and submitted to NJCAT in 2013. As a result, Contech
agreed to alter the scour testing procedure and repeat the scour testing requirements described in
the NJDEP laboratory protocol for hydrodynamic separators. Specifically, commenters
questioned whether in addition to the dedicated sedimentation sump, sediment may also
accumulate in the annular area outside of the screening chamber. Contech’s experience with the
CDS has demonstrated that sediment accumulation in this area is generally minimal. Since the
possibility of some sediment accumulating in this area during low flows could not be ruled out,
Contech agreed to repeat the scour testing procedure after preloading scour testing sediment in
the sedimentation sump as well as on top of the annular area outside of the screening chamber.
The scour testing and associated procedures described herein were completed at Contech’s full
scale laboratory in Portland, Oregon since the Scarborough Maine laboratory was no longer
available. All testing and procedures conducted at Contech’s facility in Portland were overseen
by Dr. Chris Berger, PhD., a colleague of Dr. Scott Wells, from Portland State University who
has an extensive background in water quality research. Samples prepared for particle size
analysis were sent to Apex Labs in Tigard, Oregon. Apex Labs is an independent certified
analytical laboratory. All background and effluent samples collected during the scour testing
procedure were also sent to Apex Labs for SSC analysis.
Testing was conducted on a full scale 4 ft. diameter (CDS-4) laboratory unit consistent in all
dimensions with the commercially available CDS-4. The CDS-4 unit was housed in a 4 ft.
diameter cylindrical aluminum tank. The 50% sediment storage capacity is defined as a
sediment depth of 1 ft. and a vertical distance of 1 ft. from the bottom of the 6-inch separation
slab. To simulate this condition a false floor was constructed eight inches from the sump floor
and covered with four inches of the scour test sediment.
The scour testing on the CDS-4 was completed on a closed loop, re-circulatory laboratory system
that is detailed in Figure 5. Water is provided to the unit via a 10 HP pump that pulls water from
the HDPE open source tank and directs the water into a 12 in. diameter pipe 11.25 ft. upstream
from the test unit. Flow is controlled through three 4 in. actuated valves, and one 4 in. manual
bypass valve. Flow is monitored by a SeaMetrics Online Magmeter (model WMX104) coupled
with a SeaMetrics FT420 rate indicator and a SeaMetrics DL76 data logger. Treated effluent is
able to freely discharge through a downturned 90 degree elbow into an HDPE catch tank
(discharge tank). A second 10 HP pump moves water from the discharge tank through two in-
line filters of 5um and 1um respectively to remove particulate from the effluent prior to
recirculation.
6
Figure 5 Schematic of Scour Testing Laboratory Setup
2.2 Test Sediment
Test Sediment Feed for Suspended Solids Removal Efficiency Testing
Sediment used for all solids removal testing was high purity silica (SiO2 99.8%) material (Sp. gr.
-2.65) with a particle size distribution (PSD) approximating 55% sand, 40% silt, and 5% clay.
Sediment for the entire project was supplied by an outside vendor, blended together in a single
batch and then packaged and shipped in fifty 50- lb. bags to Contech. Batch PSD was confirmed
by Contech prior to testing by collecting subsamples from 20% of the bags (10 bags/subsamples)
and compositing the subsamples into a single sample for PSD analysis. Each of the 50 bags was
numbered 1-50 prior to subsample collection. The numbers 1-50 were then written on individual
slips of paper and placed into a container. Numbers were pulled from the container at random to
determine which of the 10 bags subsamples would be collected from. This process was repeated
three times for a total of three separate PSD analyses, each of which was comprised of 10
subsamples.
The mean of the three PSD samples was calculated and plotted as a single PSD curve
representing the batch of material. Sediment sampling for PSD analysis was conducted in-house
with oversight from FB Environmental Associates, Inc. The three PSD analyses were also
carried out in-house under the direct supervision of FB in accordance with ASTM D422-63
(reapproved 2007).
7
Scour Test Sediment
Prior to the start of testing, Contech procured a batch of scour sediment manufactured to be
compliant with the scour sediment PSD specification defined in the NJDEP laboratory protocol.
The scour sediment was packaged by the manufacturer into 50 lb. bags for delivery and storage.
To ensure that the scour sediment was compliant with the PSD specifications, three composite
samples comprised of 12 randomly pulled subsamples were collected and analyzed for PSD. The
compositing procedure was as follows: 59 bags of washout sediment were numbered 1-59 prior
to subsample collection. Microsoft Excel randomizer function was used to determine 3 sets of 12
randomly determined values using the RANDBETWEEN (x, y) function, where x = 1, and y=
59. Bags with numbers matching each set of randomly determined values were well mixed and
then subsamples were collected and mixed together into a sample jar. Each subsample consisted
of two level tablespoons of material with a combined weight of approximately 50 grams. The 3
composite samples were sent to Apex Labs in Tigard, Oregon for PSD testing following ASTM
D422-63 (Reapproved 2007).
2.3 Removal Efficiency Testing Procedure
Removal efficiency testing utilized the “Effluent Grab Sampling Method,” as described in
section 5D of the NJDEP HDS Protocol. FB Environmental provided third party oversight for
the duration of all testing. Prior to each test, the flow rate was stabilized at the desired test rate.
Once the flow rate was stabilized dry feed of the surrogate test contaminant commenced
subsequently initiating the testing procedure. A vibratory hopper and auger (manufactured by
Vibra-Screw Inc.) was used to meter solids into the flow stream at a rate calculated to yield 200
mg/L (±10%). Target feed rate (mg/min) was determined by the following formula:
The grab sampling method was used to directly obtain each effluent, background and feed rate
calibration sample. Effluent samples were collected by sweeping bottles in a circular motion
through the freely discharging effluent stream. The duration required to obtain each feed rate
sample was measured and recorded to the nearest second. The first effluent and background
sample were collected simultaneously three detention times after the target flow rate was
achieved. Detention time of the test unit was determined through the following formulas:
Volume of CDS-4 =
Detention time:
Collection of the first feed rate calibration sample occurred immediately following the collection
of the first effluent and background samples. Since the feed rate sampling procedure temporarily
disrupts the introduction of solids, a period of three detention times was allowed to elapse before
obtaining the second effluent sample. Since feed rate and background samples were collected
immediately following and during collection of each odd numbered effluent sample, the
collection interval for treated effluent consisted of three detention times after odd numbered
8
effluent samples and one minute after even numbered effluent samples. After the sixth and final
feed rate sample was collected, sampling continued in one minute increments for the remainder
of the test until a total of 15 effluent samples were collected.
Following each test all feed rate calibration samples were weighed to the nearest milligram in-
house on a calibrated balance. The resultant mass of each sample was divided by the duration
required to obtain the sample. FB Environmental oversaw all in-house measurements and
calculations. After each test, effluent and background samples were packed for delivery and sent
to Maine Environmental Laboratory for analysis in accordance with ASTM D3977-97 (SSC) (re-
approved 2007).
The test procedure was repeated for each flow rate corresponding to 25%, 50%, 75%, 100% and
125% of the target MTFR.
2.4 Scour Testing Procedure
Prior to the start of testing, sediment was loaded into the sedimentation sump and leveled at a
depth of 4 inches bringing the top of the sediment pile to an elevation consistent with 50% of the
maximum sediment storage capacity (12 inches below separation slab). In order to be
conservative, 4 inches of sediment was also loaded onto the top surface of the separation slab
and leveled accordingly. To gain access to the top of the separation slab the screen and upper
internals were temporarily removed from the test unit. After loading and leveling the sediment
on the separation slab, the screen and internals were carefully installed to insure minimal
disturbance of the pre-loaded sediment.
After sediment had been loaded into the sedimentation sump and onto the separation slab and the
unit was fully assembled, the CDS-4 was filled with water using a spray nozzle adjusted to a
gentle spray and attached to a garden hose. Water was directed into the center of the sump and an
effort was made to minimize disturbance of the sediment. The unit was filled with water to the
invert of the inlet and outlet pipe which is consistent with the dry weather condition of the CDS.
Filling was terminated just before water reached the height of the inverts. The scour test was
carried out 68 hours after filling the unit with water. During testing, the flow was monitored and
recorded using a SeaMetrics Online Magmeter (model WMX104) coupled with a SeaMetrics
FT420 rate indicator and a SeaMetrics DL76 data logger.
Testing commenced by gradually introducing and increasing flow into the system until a
minimum 200% MTFR was achieved. The target tested flow rate was achieved (+/- 10%) within
four minutes of introducing flow to the system. The first background and effluent samples were
collected five minutes after the introduction of water to the system. Effluent samples were
collected by sweeping the sample container through the free discharge of the outlet pipe.
Effluent grab sampling continued in two minute increments until a total of 15 samples were
obtained. Background samples were collected in new 500ml HDPE bottles through a sample
port in the influent pipe upstream of the test unit in evenly spaced intervals throughout the
duration of the test. A total of 8 background samples were collected. At the conclusion of
testing the effluent and background samples were sent to Apex Laboratories in Tigard, Oregon
for suspended solids concentration (SSC) analysis in accordance with ASTM D3977-97.
9
3. Performance Claims
Per the NJDEP verification procedure document (NJDEP, 2013a), the following are the
performance claims made by Contech and/or established via the laboratory testing conducted.
Total Suspended Solids Removal Rate
Based on the laboratory testing conducted, the Contech Continuous Deflective Separation (CDS)
Stormwater Treatment Device achieved greater than 50% removal efficiency of suspended
solids. In accordance with the NJDEP procedure for obtaining verification of a stormwater
manufactured treatment device from NJCAT (NJDEP 2013a) the TSS removal efficiency is
rounded down to 50%.
Maximum Treatment Flow Rate (MTFR)
For all of the commercially available model sizes, the hydraulic loading rate used to calculate the
MTFR is 33.2 gpm/ft2.
Maximum sediment storage depth and volume
The maximum sediment storage depth for each CDS model is one foot. One-foot represents 50%
of the 2 ft. sediment sump that is part of each CDS standard model. The available volume is
dependent on the size of the manhole. The CDS-4 tested (4’ diameter manhole) has 25.1 cubic
feet of available storage volume.
Effective treatment area
The effective treatment area is dependent on the size of the CDS model used and is the surface
area of the CDS model selected.
Detention time and volume
The CDS-4 detention time at the MTFR is 50 seconds and the total wet volume including
sediment sump is 50.3 ft3.
Effective sedimentation area
The effective sedimentation area and effective treatment area for the CDS Stormwater Treatment
System are identical.
Online installation
Based on the testing results shown in Section 4.4 the CDS Stormwater Treatment System
qualifies for online installation.
4. Supporting Documentation
The NJDEP Procedure (NJDEP, 2013a) for obtaining verification of a stormwater manufactured
treatment device (MTD) from the New Jersey Corporation for Advanced Technology (NJCAT)
requires that “copies of the laboratory test reports, including all collected and measured data; all
10
data from performance evaluation test runs; spreadsheets containing original data from all
performance test runs; all pertinent calculations; etc.” be included in this section. This was
discussed with NJDEP and it was agreed that as long as such documentation could be made
available by NJCAT upon request that it would not be prudent or necessary to include all this
information in this verification report.
4.1 Test Sediment PSD Analysis – Removal Efficiency Testing
Prior to the start of removal efficiency testing Contech procured 2500 pounds of test sediment
deemed compliant with the PSD specification detailed in the NJDEP HDS Protocol and had it
packaged into fifty 50 lb bags for delivery and storage. To ensure that sediment was uniformly
mixed across the entire batch, three composite samples were created and analyzed for PSD. Test
sediment batch PSD for the project was verified by collecting subsamples from 20% of the bags
(10 bags/subsamples per composite) and compositing the subsamples into a single sample for
PSD analysis. Each of the 50 bags was numbered 1-50 prior to subsample collection. The
numbers 1-50 were then written on individual slips of paper and placed into a container.
Numbers were pulled from the container at random to determine which of the 10 bags
subsamples would be collected from. This process was repeated three times to create a total of
three separate composite samples for PSD analyses, each of which was comprised of 10
subsamples from 10 different bags. Sediment sampling for PSD analysis was conducted in-house
with oversight from FB Environmental Associates, Inc. The three PSD analyses were also
carried out in-house under the direct supervision of FB in accordance with ASTM D422-63
(reapproved 2007).
Results of the three PSD analyses completed on the batch of test sediment are provided in Table
1. The median particle size (d50) of the test material is less than 75 microns for all three samples.
Table 1 Removal Efficiency Sediment Particle Size Distribution Analysis
Particle Size
(µm)
Percent
Finer
Particle Size
(µm)
Percent
Finer
Particle Size
(µm)
Percent
Finer
Particle
Size (µm)
Percent
Finer
2000 100.0 2000 100.0 2000 100.0 2000 100.0
1000 99.6 1000 99.7 1000 99.6 1000 99.7
500 96.2 500 96.1 500 96.1 500 96.1
250 87.9 250 87.6 250 93.4 250 89.6
212 83.7 212 83.4 212 89.9 212 85.7
150 74.2 150 73.6 150 80.1 150 76.0
125 67.9 125 67.6 125 73.9 125 69.8
106 62.0 106 61.8 106 68.0 106 63.9
75 51.9 75 51.4 75 57.7 75 53.7
53 45.8 53 45.4 53 51.6 53 47.6
32.9 44.0 32.9 44.0 32.7 45.0 32.8 44.4
21.2 38.0 21.2 38.0 21.2 38.4 21.2 38.2
12.5 32.0 12.5 32.0 12.5 32.0 12.5 32.0
9.1 27.0 9.0 27.0 9.1 26.0 9.0 26.7
6.4 22.0 6.4 23.0 6.4 22.0 6.4 22.3
3.3 15.0 3.3 14.0 3.2 14.0 3.2 14.3
1.4 7.0 1.4 8.0 1.4 8.0 1.4 7.7
Contech Mean PSD
Contech Test Sediment Particle Distribution Results
Contech PSD Sample 1 Contech PSD Sample 2 Contech PSD Sample 3
11
The mean PSD for the 3 samples was also calculated and presented in Table 1. As described in
the NJDEP HDS Protocol the mean PSD serves as the PSD of the batch of test sediment.
The mean PSD of Contech’s test sediment complies with the PSD criteria established by the
NJDEP HDS protocol. Figure 6 plots the Contech PSD against the NJDEP PSD specification.
The Contech sediment gradation is equivalent to or finer than the NJDEP gradation at all points
along the curve. Overall, the Contech sediment blend contains more fines than the NJDEP
gradation, particularly below 50 microns. The median particle size of the Contech gradation is
approximately 60 microns.
Figure 6 Comparison of the Mean Contech Test Sediment PSD to the NJDEP Removal
Efficiency Test Sediment PSD Specification
4.2 Removal Efficiency Testing
In accordance with the NJDEP HDS Protocol, removal efficiency testing was executed on the
CDS-4 laboratory unit in order to establish the ability of the CDS to remove the specified test
sediment at 25%, 50%, 75%, 100% and 125% of the target MTFR. Prior to the start of testing
Contech reviewed existing data and decided to utilize a target MTFR of 0.93 cfs. This target was
chosen based on the ultimate goal of demonstrating greater than 50% annualized weighted solids
removal as defined in the NJDEP HDS Protocol. The Mean Influent Concentration was
12
calculated from the mean feed rate and the mean flow rate; while the mean effluent concentration
was adjusted by subtraction of the background concentration.
25% MTFR Results
To establish the performance of the CDS-4 at 25% MTFR a test was conducted in accordance
with the criteria in the NJDEP HDS Protocol at a target flow rate of 0.23 cfs. Table 2 provides
an overview of the test conditions and a summary of the results for the 25% MTFR test. The
feed rate calibration sample results are provided in Table 3. Background and effluent sampling
results for the trial are presented in Table 4. The CDS-4 removed 67.0% of the test sediment at
an operating rate of 0.24 cfs. Each of the QA/QC parameters that pertain to sampling and flow
measurement are presented in Table 5 and are in compliance with the thresholds defined in the
NJDEP HDS Protocol.
Table 2 Summary of CDS-4 25% MTFR Laboratory Test
Trial Date Target Flow (cfs)Detention Time
(sec)
Target Sediment
Concentration (mg/l)Target Feed Rate (mg/min)Test Duration
(Min)
4-Apr-13 0.23 199 200mg/l 78,547 83.73
Mean Flow
Rate (cfs)
Mean Influent
Concentration
(mg/l)
Mean Water
Temperature F
Mean Adjusted Effluent
Concentration (mg/l)Average Removal Efficiency QA/QC
Compliance
0.24cfs 194 52 64 67.0%Yes
CDS-4 25% MTFR Trial Summary
Measured Values
Table 3 CDS-4 25% MTFR Feed Rate Calibration Sample Results
Target
Concentration 200 mg/l
Sample ID Sample Time
(min)
Sample
Weight
(mg)
Sample
Duration
(sec)
Feed
Rate
(mg/min)
Calculated
Influent
Concentration
(mg/L)
Feed Rate 1 9.96 84605 60.31 84170 205
Feed Rate 2 21.92 79959 60.28 79588 193
Feed Rate 3 33.88 78509 60.25 78183 190
Feed Rate 4 45.85 77831 60.25 77508 188
Feed Rate 5 57.81 77270 60.31 76873 187
Feed Rate 6 69.77 82288 60.47 81648 198
Mean 79662 194
CDS-4 25% MTFR Feed Rate Calibration Sample Results
Target Feed Rate 78,547 mg/min
13
Table 4 CDS-4 25% MTFR Background and Effluent Sample Results
Sample ID Time (min)Concentration (mg/L)
Background 1 9.96 2
Background 2 21.92 2
Background 3 33.88 2
Background 4 45.85 2
Background 5 57.81 2
Background 6 69.77 2
Background 7 81.73 2
Background 8 83.73 2
Sample ID Time (min)Concentration (mg/L)
Associated
Background
Concentration
(mg/l)
Adjusted
Concentration
(mg/l)
Temperature
F
Effluent 1 9.96 67 2 65 61
Effluent 2 20.92 68 2 66 57
Effluent 3 21.92 68 2 66 56
Effluent 4 32.88 62 2 60 55
Effluent 5 33.88 65 2 63 55
Effluent 6 44.85 63 2 61 54
Effluent 7 45.85 71 2 69 53
Effluent 8 56.81 66 2 64 50
Effluent 9 57.81 66 2 64 51
Effluent 10 68.77 67 2 65 48
Effluent 11 69.77 68 2 66 48
Effluent 12 80.73 71 2 69 47
Effluent 13 81.73 63 2 61 47
Effluent 14 82.73 63 2 61 47
Effluent 15 83.73 66 2 64 47
Mean 66 2 64 52
Note that the analytical laboratory established a limit of quantification (LOQ) for SSC of 4mg/l. Values below this threshold are
reported as non detect (ND) by the laboratory. In following standard reporting practices ND values have been reported at 1/2 the LOQ
which is 2mg/l for this study.
CDS-4 25% of MTFR Test Background and Effluent Sample Results
Table 5 CDS-4 25% MTFR QA/QC Parameters
Target (gpm)Mean (gpm)Coef. of Variance Acceptable Parameters Target
Acceptable Parameters Coef. Of
Variance
103.75 108.7 0.01 <0.03
Target (mg/min)Mean (mg/min)Coef. of Variance Acceptable Parameter Target
Acceptable Parameters Coef. Of
Variance
78547 79662 0.04 <0.1
Target (mg/L)Mean (mg/L)Coef. of Variance Acceptable Parameter Target
Acceptable Parameters Coef. Of
Variance
200 194 0.04 <0.1
Low (mg/L)High (mg/L)Mean (mg/L)
2 2 2
Flow Rate
CDS-4 25% of MTFR QA/QC Parameters
Background Concentration
Acceptable Threshold (mg/L)
<20
Influent Concentration
Feed Rate
14
50% MTFR Results
To establish the performance of the CDS-4 at 50% MTFR a test was conducted in accordance
with the criteria in the NJDEP HDS Protocol at a target flow rate of 0.46 cfs. Table 6 provides
an overview of the test conditions and a summary of the results for the 50% MTFR test. The
feed rate calibration sample results are provided in Table 7. Background and effluent sampling
results for the trial are presented in Table 8. The CDS-4 removed 54.3% of the test sediment at
an operating rate of 0.46 cfs. Each of the QA/QC parameters that pertain to sampling and flow
measurement are presented in Table 9 and are in compliance with the thresholds defined in the
NJDEP HDS Protocol.
Table 6 Summary of CDS-4 50% MTFR Laboratory Test
Trial Date Target Flow (cfs)Detention Time
(sec)
Target Sediment
Concentration (mg/l)Target Feed Rate (mg/min)Test Duration
(Min)
4-Apr-13 0.46 100 200mg/l 157,095 48.87
Mean Flow
Rate (cfs)
Mean Influent
Concentration
(mg/l)
Mean Water
Temperature F
Mean Adjusted Effluent
Concentration (mg/l)Average Removal Efficiency QA/QC
Compliance
0.46cfs 195 48 89 54.3%Yes
CDS-4 50% MTFR Trial Summary
Measured Values
Table 7 CDS-4 50% MTFR Feed Rate Calibration Sample Results
Target
Concentration 200 mg/l
Sample ID Sample Time
(min)
Sample
Weight
(mg)
Sample
Duration
(sec)
Feed Rate
(mg/min)
Calculated
Influent
Concentration
(mg/L)
Feed Rate 1 4.98 103404 40.32 153875 196
Feed Rate 2 11.96 104049 40.28 154989 198
Feed Rate 3 18.94 105251 40.59 155582 199
Feed Rate 4 25.92 107070 40.32 159330 203
Feed Rate 5 32.90 97634 40.35 145181 185
Feed Rate 6 39.88 99647 40.32 148284 189
Mean 152873 195
CDS-4 50% MTFR Feed Rate Calibration Sample Results
Target Feed Rate 157,095 mg/min
15
Table 8 CDS-4 50% MTFR Background and Effluent Sample Results
Sample ID Time (min)Concentration (mg/L)
Background 1 4.98 2
Background 2 11.96 2
Background 3 18.94 2
Background 4 25.92 2
Background 5 32.90 2
Background 6 39.88 2
Background 7 46.87 2
Background 8 48.87 2
Sample ID Time (min)Concentration (mg/L)
Associated
Background
Concentration
(mg/l)
Adjusted
Concentration
(mg/l)
Temperature
F
Effluent 1 4.98 83 2 81 52
Effluent 2 10.96 87 2 85 49
Effluent 3 11.96 91 2 89 49
Effluent 4 17.94 91 2 89 48
Effluent 5 18.94 88 2 86 48
Effluent 6 24.92 88 2 86 49
Effluent 7 25.92 92 2 90 49
Effluent 8 31.90 87 2 85 48
Effluent 9 32.90 94 2 92 47
Effluent 10 38.88 95 2 93 47
Effluent 11 39.88 99 2 97 47
Effluent 12 45.87 86 2 84 47
Effluent 13 46.87 92 2 90 47
Effluent 14 47.87 102 2 100 46
Effluent 15 48.87 93 2 91 46
Mean 91 2 89 48
CDS-4 50% of MTFR Background and Effluent Sample Results
Note that the analytical laboratory established a limit of quantification (LOQ) for SSC of 4mg/l. Values below this threshold are
reported as non detect (ND) by the laboratory. In following standard reporting practices ND values have been reported at 1/2 the LOQ
which is 2mg/l for this study.
Table 9 CDS-4 50% MTFR QA/QC Parameters
Target (gpm)Mean (gpm)Coef. of Variance Acceptable Parameters Target
Acceptable Parameters Coef. Of
Variance
207.5 205.3 0.01 <0.03
Target (mg/min)Mean (mg/min)Coef. of Variance Acceptable Parameter Target
Acceptable Parameters Coef. Of
Variance
157095 152873 0.03 <0.1
Target (mg/L)Mean (mg/L)Coef. of Variance Acceptable Parameter Target
Acceptable Parameters Coef. Of
Variance
200 195 0.03 <0.1
Low (mg/L)High (mg/L)Mean (mg/L)
2 2 2
Background Concentration
Acceptable Threshold (mg/L)
<20
Influent Concentration
Feed Rate
Flow Rate
CDS-4 50 % of MTFR QA/QC Parameters
16
75% MTFR Results
To establish the performance of the CDS-4 at 75% MTFR a test was conducted in accordance
with the criteria in the NJDEP HDS Protocol at a target flow rate of 0.69 cfs. Table 10 provides
an overview of the test conditions and a summary of the results for the 75% MTFR test. The
feed rate calibration sample results are provided in Table 11. Background and effluent sampling
results for the trial are presented in Table 12. The CDS-4 removed 45.7% of the test sediment at
an operating rate of 0.71 cfs. Each of the QA/QC parameters that pertain to sampling and flow
measurement are presented in Table 13 and are in compliance with the thresholds defined in the
NJDEP HDS Protocol.
Table 10 Summary of CDS-4 75% MTFR Laboratory Test
Trial Date Target Flow (cfs)Detention Time
(sec)
Target Sediment
Concentration (mg/l)Target Feed Rate (mg/min)Test Duration
(Min)
5-Apr-13 0.69 66 200mg/l 235,453 37.26
Mean Flow
Rate (cfs)
Mean Influent
Concentration
(mg/l)
Mean Water
Temperature F
Mean Adjusted Effluent
Concentration (mg/l)Average Removal Efficiency QA/QC
Compliance
0.71 198 59 108 45.7%Yes
CDS-4 75% MTFR Trial Summary
Measured Values
Table 11 CDS-4 75% MTFR Feed Rate Calibration Sample Results
Target
Concentration 200 mg/l
Sample ID Sample Time
(min)
Sample
Weight
(mg)
Sample
Duration
(sec)
Feed Rate
(mg/min)
Calculated
Influent
Concentration
(mg/L)
Feed Rate 1 3.32 118724 30.28 235252 195
Feed Rate 2 8.65 120157 30.29 238013 197
Feed Rate 3 13.97 120241 30.34 237787 197
Feed Rate 4 19.29 117986 30.31 233559 194
Feed Rate 5 24.62 124367 30.47 244897 203
Feed Rate 6 29.94 121793 30.34 240856 200
Mean 238394 198
CDS-4 75% MTFR Feed Rate Calibration Sample Results
Target Feed Rate 238,394 mg/min
17
Table 12 CDS-4 75% MTFR Background and Effluent Sample Results
Sample ID Time (min)Concentration (mg/L)
Background 1 3.32 2
Background 2 8.65 4
Background 3 13.97 2
Background 4 19.29 5
Background 5 24.62 8
Background 6 29.94 9
Background 7 35.26 14
Background 8 37.26 14
Sample ID Time (min)Concentration (mg/L)
Associated
Background
Concentration
(mg/l)
Adjusted
Concentration
(mg/l)
Temperature
F
Effluent 1 3.32 98 2 96 66
Effluent 2 7.65 99 3 96 63
Effluent 3 8.65 104 3 101 63
Effluent 4 12.97 101 3 98 61
Effluent 5 13.97 106 3 103 61
Effluent 6 18.29 107 5 102 60
Effluent 7 19.29 117 5 112 60
Effluent 8 23.62 118 7 111 59
Effluent 9 24.62 115 7 108 58
Effluent 10 28.94 122 9 113 57
Effluent 11 29.94 122 10 112 56
Effluent 12 34.26 118 12 106 55
Effluent 13 35.26 134 13 121 54
Effluent 14 36.26 137 14 123 54
Effluent 15 37.26 125 15 110 54
Mean 115 7 108 59
CDS-4 75% of MTFR Background and Effluent Sample Results
Note that the analytical laboratory established a limit of quantification (LOQ) for SSC of 4mg/l. Values below this threshold are
reported as non detect (ND) by the laboratory. In following standard reporting practices ND values have been reported at 1/2 the LOQ
which is 2mg/l for this study.
Table 13 CDS-4 75% MTFR QA/QC Parameters
Target (gpm)Mean (gpm)Coef. of Variance Acceptable Parameters Target
Acceptable Parameters Coef. Of
Variance
311 318.4 0.01 <0.03
Target (mg/min)Mean (mg/min)Coef. of Variance Acceptable Parameter Target
Acceptable Parameters Coef. Of
Variance
235453 238394 0.02 <0.1
Target (mg/L)Mean (mg/L)Coef. of Variance Acceptable Parameter Target
Acceptable Parameters Coef. Of
Variance
200 198 0.02 <0.1
Low (mg/L)High (mg/L)Mean (mg/L)
2 14 7
Background Concentration
Acceptable Threshold (mg/L)
<20
Influent Concentration
Feed Rate
Flow Rate
75% of MTFR QA/QC Parameters
18
100% MTFR Results
To establish the performance of the CDS-4 at 100% MTFR a test was conducted in accordance
with the criteria in the NJDEP HDS Protocol at a target flow rate of 0.93 cfs. Table 14 provides
an overview of the test conditions and a summary of the results for the 100% MTFR test. The
feed rate calibration sample results are provided in Table 15. Background and effluent sampling
results for the trial are presented in Table 16. The CDS-4 removed 39.2% of the test sediment at
an operating rate of 0.93 cfs. Each of the QA/QC parameters that pertain to sampling and flow
measurement are presented in Table 17 and are in compliance with the thresholds defined in the
NJDEP HDS Protocol.
Table 14 Summary of CDS-4 100% MTFR Laboratory Test
Trial Date Target Flow (cfs)Detention Time
(sec)
Target Sediment
Concentration (mg/l)Target Feed Rate (mg/min)Test Duration
(Min)
3-Apr-13 0.925 49.8 200mg/l 314,189 31.43
Mean Flow
Rate (cfs)
Mean Influent
Concentration
(mg/l)
Mean Water
Temperature F
Mean Adjusted Effluent
Concentration (mg/l)Average Removal Efficiency QA/QC
Compliance
0.93 198 67 120 39.2%Yes
CDS-4 100% MTFR Trial Summary
Measured Values
Table 15 CDS-4 100% MTFR Feed Rate Calibration Sample Results
Target
Concentration 200 mg/l
Sample ID Sample Time
(min)
Sample
Weight
(mg)
Sample
Duration
(sec)
Feed Rate
(mg/min)
Calculated
Influent
Concentration
(mg/L)
Feed Rate 1 2.49 107412 20.25 318258 202
Feed Rate 2 6.98 102117 20.28 302121 192
Feed Rate 3 11.47 104403 20.35 307822 195
Feed Rate 4 15.96 105087 20.43 308626 196
Feed Rate 5 20.45 109563 20.72 317267 201
Feed Rate 6 24.94 105835 20.19 314517 200
Mean 311435 198
CDS-4 100% MTFR Feed Rate Calibration Sample Results
Target Feed Rate 314,189 mg/min
19
Table 16 CDS-4 100% MTFR Background and Effluent Sample Results
Sample ID Time (min)Concentration (mg/L)
Background 1 2.49 2
Background 2 6.98 6
Background 3 11.47 10
Background 4 15.96 9
Background 5 20.45 13
Background 6 24.94 11
Background 7 29.43 13
Background 8 31.43 14
Sample ID Time (min)Concentration (mg/L)
Associated
Background
Concentration
(mg/l)
Adjusted
Concentration
(mg/l)
Temperature
F
Effluent 1 2.49 101 2 99 78
Effluent 2 5.98 119 6 113 75
Effluent 3 6.98 120 7 113 74
Effluent 4 10.47 127 8 119 72
Effluent 5 11.47 127 9 118 71
Effluent 6 14.96 128 10 118 69
Effluent 7 15.96 135 10 125 69
Effluent 8 19.45 138 11 127 66
Effluent 9 20.45 132 11 121 65
Effluent 10 23.94 136 12 124 64
Effluent 11 24.94 129 12 117 63
Effluent 12 28.43 134 13 121 61
Effluent 13 29.43 143 13 130 60
Effluent 14 30.43 142 13 129 59
Effluent 15 31.43 144 13 131 59
Mean 130 10 120 67
CDS-4 100% of MTFR Background and Effluent Sample Results
Note that the analytical laboratory established a limit of quantification (LOQ) for SSC of 4mg/l. Values below this threshold are
reported as non detect (ND) by the laboratory. In following standard reporting practices ND values have been reported at 1/2 the LOQ
which is 2mg/l for this study.
Table 17 CDS-4 100% MTFR QA/QC Parameters
Target (gpm)Mean (gpm)Coef. of Variance Acceptable Parameters Target
Acceptable Parameters Coef. Of
Variance
415 416.1 0.01 <0.03
Target (mg/min)Mean (mg/min)Coef. of Variance Acceptable Parameter Target
Acceptable Parameters Coef. Of
Variance
314189 311435 0.02 <0.1
Target (mg/L)Mean (mg/L)Coef. of Variance Acceptable Parameter Target
Acceptable Parameters Coef. Of
Variance
200 198 0.02 <0.1
Low (mg/L)High (mg/L)Mean (mg/L)
2 14 10
Flow Rate
100% of MTFR QA/QC Parameters
Background Concentration
Acceptable Threshold (mg/L)
<20
Influent Concentration
Feed Rate
20
125% MTFR Results
To establish the performance of the CDS-4 at 125% MTFR a test was conducted in accordance
with the criteria in the NJDEP HDS Protocol at a target flow rate of 1.16 cfs. Table 18 provides
an overview of the test conditions and a summary of the results for the 125% MTFR test. The
feed rate calibration sample results are provided in Table 19. Background and effluent sampling
results for the trial are presented in Table 20. The CDS-4 removed 25.1% of the test sediment at
an operating rate of 1.18 cfs. Each of the QA/QC parameters that pertain to sampling and flow
measurement are presented in Table 21 and are in compliance with the thresholds defined in the
NJDEP HDS Protocol.
Table 18 Summary of CDS-4 125% MTFR Laboratory Test
Trial Date Target Flow (cfs)Detention Time
(sec)
Target Sediment
Concentration (mg/l)Target Feed Rate (mg/min)Test Duration
(Min)
18-Apr-13 1.16 40 200mg/l 392,926 27.94
Mean Flow
Rate (cfs)
Mean Influent
Concentration
(mg/l)
Mean Water
Temperature F
Mean Adjusted Effluent
Concentration (mg/l)Average Removal Efficiency QA/QC
Compliance
1.18 207 55 155 25.1%Yes
CDS-4 125% MTFR Trial Summary
Measured Values
Table 19 CDS-4 125% MTFR Feed Rate Calibration Sample Results
Target
Concentration 200 mg/l
Sample ID Sample Time
(min)
Sample
Weight
(mg)
Sample
Duration
(sec)
Feed Rate
(mg/min)
Calculated
Influent
Concentration
(mg/L)
Feed Rate 1 1.99 140782 20.28 416515 208
Feed Rate 2 5.98 140724 20.25 416960 208
Feed Rate 3 9.97 139761 20.29 413290 207
Feed Rate 4 13.97 136840 20.25 405452 203
Feed Rate 5 17.96 136211 20.28 402991 201
Feed Rate 6 21.95 143011 19.9 431189 216
Mean 414400 207
CDS-4 125% MTFR Feed Rate Calibration Sample Results
Target Feed Rate 392926 mg/min
21
Table 20 CDS-4 125% MTFR Background and Effluent Sample Results
Sample ID Time (min)Concentration (mg/L)
Background 1 1.99 2
Background 2 5.98 7
Background 3 9.97 10
Background 4 13.97 11
Background 5 17.96 11
Background 6 21.95 15
Background 7 25.94 16
Background 8 27.94 18
Sample ID Time (min)Concentration (mg/L)
Associated
Background
Concentration
(mg/l)
Adjusted
Concentration
(mg/l)
Temperature
F
Effluent 1 1.99 130 3 127 63
Effluent 2 4.98 137 5 132
Effluent 3 5.98 171 6 165
Effluent 4 8.97 145 8 137
Effluent 5 9.97 161 9 152
Effluent 6 12.97 174 10 164
Effluent 7 13.97 176 11 165
Effluent 8 16.96 171 12 159
Effluent 9 17.96 170 13 157
Effluent 10 20.95 174 14 160
Effluent 11 21.95 162 15 147 52
Effluent 12 24.94 170 16 154
Effluent 13 25.94 172 16 156
Effluent 14 26.94 191 17 174
Effluent 15 27.94 196 17 179 50
Mean 167 12 155 55
CDS-4 125% of MTFR Background and Effluent Sample Results
Note that the analytical laboratory established a limit of quantification (LOQ) for SSC of 4mg/l. Values below this threshold are
reported as non detect (ND) by the laboratory. In following standard reporting practices ND values have been reported at 1/2 the LOQ
which is 2mg/l for this study.
Table 21 CDS-4 125% MTFR QA/QC Parameters
Target (gpm)Mean (gpm)Coef. of Variance Acceptable Parameters Target
Acceptable Parameters Coef. Of
Variance
519 528.5 0.02 <0.03
Target (mg/min)Mean (mg/min)Coef. of Variance Acceptable Parameter Target
Acceptable Parameters Coef. Of
Variance
392926 414400 0.02 <0.1
Target (mg/L)Mean (mg/L)Coef. of Variance Acceptable Parameter Target
Acceptable Parameters Coef. Of
Variance
200 207 0.02 <0.1
Low (mg/L)High (mg/L)Mean (mg/L)
2 18 11
Flow Rate
125% of MTFR QA/QC Parameters
Background Concentration
Acceptable Threshold (mg/L)
<20
Influent Concentration
Feed Rate
Excluded Data/Results
The NJDEP HDS Protocol requires that any data collected as part of the testing process that is
ultimately excluded from the reported results be discussed during the reporting process. No data
22
was excluded from the datasets that make up each of the 5 qualifying test trials reported herein
and ultimately used to determine the annualized weighted TSS Removal Efficiency.
During the testing process four trials were conducted at the target 125% MTFR flow condition
that were not included in the qualifying data set. On 4/5/2013, a trial was executed at the target
125% MTFR, but was suspended before the completion of sampling due to a pump failure in the
laboratory. On 4/9/2013, a second attempt was made to complete a 125% of MTFR test. This
data was disqualified because one of the background samples exceeded the maximum allowable
threshold of 20 mg/l. A third 125% MTFR trial was conducted on 4/9/2013 but deemed out of
compliance because an issue with the dry feed auger resulted in average influent concentrations
below 180 mg/l, which falls below the allowable range of influent concentrations. A fourth
attempt to complete the 125% MTFR testing on 4/9/2013 was quickly suspended after a circuit
breaker tripped, effectively disabling the laboratory in the middle of the test.
This disclosure represents the only data not otherwise reported and included in the calculations
herein.
Annualized Weighted TSS Removal Efficiency
The results of TSS removal efficiency testing at 25%, 50%, 75%, 100% and 125% of a target
MTFR of 0.93 cfs and reported herein were entered into the NJDEP specified annualized
weighted TSS removal efficiency calculation. The results are presented in Table 22.
Testing in accordance with all of the provisions detailed in the NJDEP HDS Protocol
demonstrate that the CDS-4 achieved 50.57% annualized weighted TSS removal at an MTFR
of 0.93 cfs (33.2 gpm/ft2). This testing also demonstrates that the CDS-4 exceeds the NJDEP
requirement for HDS devices of demonstrating greater than 50% weighted annualized TSS
Removal Efficiency at the chosen MTFR.
Table 22 Annualized Weighted TSS Removal of the CDS-4 Tested in Accordance with the
NJDEP HDS Protocol at a MTFR of 0.93 cfs.
Tested Flow
Rate as
Percentage of
MTFR
Actual Tested
Flow Rate
(cfs)
Actual
Percent
MTFR
Measured
Removal
Efficiency
Annual
Weighting
Factor
Weighted
Removal
Efficiency
25%0.24 26%67.0 0.25 16.75%
50%0.46 49%54.3 0.3 16.29%
75%0.71 76%45.7 0.2 9.14%
100%0.93 100%39.2 0.15 5.88%
125%1.18 127%25.1 0.1 2.51%
50.57%Weighted Annualized TSS Removal Efficiency
CDS-4 Annualized Weighted TSS Removal at 0.93cfs MTFR
23
4.3 Test Sediment PSD Analysis - Scour Testing
As described in Section 2.2 Scour Test Sediment, prior to the start of testing Contech procured a
batch of scour sediment deemed compliant with the scour sediment PSD specification defined in
the NJDEP HDS Protocol and had it packaged into fifty-nine 50 lb bags for delivery and storage.
To ensure that the scour sediment was uniformly mixed across the entire batch, three composite
samples were created and analyzed for PSD as previously described.
The results of the PSD analysis performed on the three samples are presented in Table 23 along
with the mean PSD for the batch of sediment used for the scour testing. This analysis confirmed
that the batch of scour test sediment procured by Contech is in compliance with the NJDEP scour
test PSD specification. A visual comparison of the Contech scour sediment PSD and the NJDEP
scour test PSD is provided in Figure 7.
Table 23 Results of Scour Testing Sediment Particle Size Distribution Analysis
Contech Scour Test Sediment Particle Distribution Results
NJDEP Specifications Contech Scour Sediment
Particle size
(um)
Percent
Finer
Particle size
(um) Percent
Finer
Sample 1
Percent
Finer
Sample 2
Percent
Finer
Sample 3
Percent
Finer Mean
Contech
Samples
1000 100 1000 100 100 100 100.0
500 90 500 92.1 91.77 91.22 91.7
250 55 250 56.37 55.28 54.44 55.4
150 40 150 42.15 41.13 40.38 41.2
100 25 106 31.44 30.58 29.97 30.7
75 10 75 11.41 11.08 10.97 11.2
50 0 63 1.64 1.59 1.54 1.6
53 0 0 0 0
24
Figure 7 Comparison of Contech Scour Test Sediment PSD to NJDEP Scour Sediment PSD
Specification
4.4 Scour Testing for Online Installation
In order to demonstrate the ability of the CDS to be used as an online treatment device scour
testing was conducted at greater than 200% of the MTFR in accordance with the NJDEP HDS
Protocol. The average flow rate during the online scour test was 838.9 gpm (1.87 cfs), which is
201% of the MTFR (MTFR = 0.93 cfs). The COV for the flow rate during the test period was
0.009, which is less than the allowable maximum COV of 0.03. The water temperature during
the testing was 73 degrees. All 8 of the background samples collected during the test were
reported as non-detect for suspended solids by the analytical laboratory. All non-detect values of
concentration have been reported as ½ of the limit of quantification herein. The limit of
quantification was calculated by the laboratory and provided in the laboratory report for each
sample. Background results and sample times are provided in Table 24. All background
concentrations are well below the 20 mg/l maximum for suspended solids.
25
Table 24 Concentrations of Background Samples during CDS Scour Testing
Sample Sample Time
(minute)
Reported
Result (mg/L)
Reporting Limit (Limit
of Quantification)
(mg/L)
Background
Concentration
(mg/l)
Background 1 5 ND 2.00 1.00
Background 2 9 ND 1.98 0.99
Background 3 13 ND 2.04 1.02
Background 4 17 ND 2.00 1.00
Background 5 21 ND 1.98 0.99
Background 6 25 ND 1.98 0.99
Background 7 29 ND 2.00 1.00
Background 8 33 ND 1.98 0.99
A total of 15 effluent grab samples were collected during the testing process. The majority of
effluent samples (10 of 15) were reported as non-detect by the analytical lab. The 5 remaining
samples all had effluent concentrations less than 5mg/l. Non-detect values were reported at ½
the limit of quantification as calculated by the analytical laboratory. The resulting effluent
concentrations were then adjusted to account for the applicable background concentration at the
time the sample was collected. The applicable background sample is defined as the background
sample/concentration associated with a given effluent sample based on sample time. Note that
there are 15 effluent samples vs. 8 background samples as a result of effluent samples being
collected more frequently. As a result, multiple effluent samples correspond to most background
samples. Since background sample concentration is essentially constant throughout the test
period the applicable adjustment to the effluent concentration is also consistent at ~1mg/l for all
samples. The resulting effluent concentrations are all 3mg/l or less and well below the 20mg/l
threshold established by the NJDEP scour protocol. All effluent sample results are presented in
Table 25.
Testing at greater than 200% of the proposed MTFR for the CDS-4 with sediment preloaded in
both the sedimentation sump and on top of the unit’s separation slab has confirmed that
previously captured sediment does not wash out and that the CDS meets the criteria for online
use.
26
Table 25 Results of CDS-4 Online Scour Testing at 201% MTFR
Sample Sample Time
(minute)
Reported
Result (mg/L)
Reporting Limit (Limit
of Quantification)
(mg/L)
Effluent
Concentration
(mg/l)
Adjusted Effluent
Concentration
(mg/l)
Effluent 1 5 3.33 2.38 3.33 2.33
Effluent 2 7 ND 3.08 1.54 0.54
Effluent 3 9 ND 2.86 1.43 0.43
Effluent 4 11 ND 2.67 1.34 0.34
Effluent 5 13 ND 2.63 1.32 0.32
Effluent 6 15 4.00 2.35 4.00 3.00
Effluent 7 17 ND 2.78 1.39 0.39
Effluent 8 19 2.41 2.41 2.41 1.41
Effluent 9 21 2.33 2.33 2.33 1.33
Effluent 10 23 3.15 2.25 3.15 2.15
Effluent 11 25 ND 2.44 1.22 0.22
Effluent 12 27 ND 2.38 1.19 0.19
Effluent 13 29 ND 2.90 1.45 0.45
Effluent 14 31 ND 3.17 1.59 0.59
Effluent 15 33 ND 2.33 1.17 0.17
5. Design Limitations
Contech’s engineering staff typically works with the site design engineer to ensure all potential
constraints are addressed during the specification process and that the CDS Stormwater
Treatment System will function as intended.
Required Soil Characteristics
The CDS is an enclosed system that is typically housed within a concrete manhole. The
functionality of the CDS system is not influenced by the existing soil conditions at the install
location and as such the CDS system can be installed in all soil types.
Slope
It is generally not advisable to install the CDS unit on steep slopes. When the CDS is being
considered on slopes exceeding 10% Contech recommends contacting their engineering staff to
evaluate the design prior to specification.
Maximum Flow Rate
The MTFR is 33.2 gpm/ft2.
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Maintenance Requirements
The CDS system must be inspected at regular intervals and maintained when necessary to ensure
optimum performance. The rate at which the system collects pollutants depends heavily on site
activities. See Section 6 for a more detailed discussion of maintenance and inspection
requirements.
Driving Head
The driving head required for a given CDS model at MTFR or greater flows (for online units) is
typically a function of the model size and storm sewer characteristics. Contech’s engineering
staff consults with the design engineer on each project to ensure there will not be any adverse
impacts to the hydraulic grade-line as a result of installing the CDS unit.
Installation limitations
Prior to installation Contech provides contractors detailed installation and assembly instructions
and is also available to consult onsite during installation. Pick weights for CDS components are
provided prior to delivery so that the contractor can secure proper equipment for lifting CDS
units into place.
Configurations
CDS units can be installed online or offline. Online units are equipped with an internal bypass to
convey extreme flows around the treatment chamber of the unit.
Structural Load Limitations
CDS units are typically designed for HS-20 loading (32,000 pounds per truck axle). If additional
loading is expected it is advisable to contact Contech to assess loading options
Pretreatment Requirements
There are no pre-treatment requirements for the CDS Stormwater Treatment System.
Limitations in Tailwater
If tail-water is present it is important to increase the available driving head within the unit to
ensure that the full MTFR is still treated prior to any internal bypass.
Depth to Seasonal High Water Table
CDS unit performance is not typically impacted by high groundwater. Occasionally, when
groundwater is expected to be within several feet of finished grade it may be necessary to add a
base extension to the unit to counter buoyant forces. If high groundwater is expected Contech’s
engineering staff can evaluate whether anti-buoyancy measures are required during the design
process, but buoyancy issues are relatively uncommon for concrete manhole structures like the
CDS.
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6. Maintenance Plans
The CDS system must be inspected at regular intervals and maintained when necessary to ensure
optimum performance. The rate at which the system collects pollutants will depend more heavily
on site activities than the size of the unit, e.g., unstable soils or heavy winter sanding will cause
the grit chamber to fill more quickly but regular sweeping will slow accumulation. Additional
information on maintenance, including a simple CDS Inspection & Maintenance Log form, can
be found in the CDS Inspection and Maintenance Guide – New Jersey at:
http://www.conteches.com/products/stormwater-management/treatment/cds.aspx#1822141-
technical-info
Inspection
Inspection is the key to effective maintenance and is easily performed. Pollutant deposition and
transport may vary from year to year and regular inspections will help insure that the system is
cleaned out at the appropriate time. At a minimum, inspections must be performed twice per year
(i.e. spring and fall) however more frequent inspections may be necessary in climates where
winter sanding operations may lead to rapid pollutant accumulations, or in equipment wash-
down areas. Additionally, installations where excessive amounts of trash are expected should be
inspected more frequently.
The visual inspection must ascertain that the system components are in working order and that
there are no blockages or obstructions to the inlet and/or separation screen. The inspection must
also identify accumulations of hydrocarbons, trash, and sediment in the system. Measuring
pollutant accumulation can be done with a calibrated dipstick such as a stadia rod, tape measure
or other measuring instrument. If sorbent material is used for enhanced removal of hydrocarbons
then the level of discoloration of the sorbent material should also be identified during inspection.
Sorbent material must be replaced when it is predominantly dark in color (similar to oil). It is
useful and often required as part of a permit to keep a record of each inspection.
Access to the CDS unit is typically achieved through two manhole access covers. One opening
allows for inspection and cleanout of the separation chamber (screen/cylinder) and isolated
sump. The other allows for inspection and cleanout of sediment captured and retained behind the
screen. For units possessing a sizable depth below grade (depth to pipe), a single access point
allows for both sump cleanout and access behind the screen.
The CDS system must be cleaned when the level of sediment in the sump has reached a depth of
18 inches or more to avoid exceeding the maximum 24 inch sediment depth and/or when an
appreciable level of hydrocarbons and trash has accumulated. If sorbent material is used, it must
be replaced when significant discoloration has occurred. Performance will not be impacted until
100% of the sump capacity is exceeded however it is recommended that the system be cleaned
prior to that for easier removal of sediment. The level of sediment is easily determined by
measuring from finished grade down to the top of the sediment pile. To avoid underestimating
the level of sediment in the chamber, the measuring device must be lowered to the top of the
sediment pile carefully. Finer, silty particles at the top of the pile typically offer less resistance to
the end of the rod than larger particles toward the bottom of the pile. Once this measurement is
recorded, it should be compared to the as-built drawing for the unit to determine if the height of
29
the sediment pile off the bottom of the sump floor exceeds 75% (18 inches) of the total height of
isolated sump.
Cleaning
Cleaning of the CDS systems should be done during dry weather conditions when no flow is
entering the system. Cleanout of the CDS with a vacuum truck is generally the most effective
and convenient method of excavating pollutants from the system. Simply remove the manhole
covers and insert the vacuum hose into the sump. The system should be completely drained
down and the sump fully evacuated of sediment. The area outside the screen should also be
pumped out if pollutant build-up exists in this area.
In installations where the risk of petroleum spills is small, liquid contaminants may not
accumulate as quickly as sediment. However, an oil or gasoline spill must be cleaned out
immediately. Motor oil and other hydrocarbons that accumulate on a more routine basis must be
removed when an appreciable layer has been captured. To remove these pollutants, it may be
preferable to use adsorbent pads since they are usually less expensive to dispose of than the
oil/water emulsion that may be created by vacuuming the oily layer. Trash can be netted out if
you wish to separate it from the other pollutants. The screen should be power washed to ensure it
is free of trash and debris.
Manhole covers should be securely seated following cleaning activities to prevent leakage of
runoff into the system from above and also to ensure proper safety precautions. Confined Space
Entry procedures need to be followed.
Disposal of all material removed from the CDS system must be done is accordance with local
regulations. In many locations, disposal of evacuated sediments may be handled in the same
manner as disposal of sediments removed from catch basins or deep sump manholes. Check your
local regulations for specific requirements on disposal.
7. Statements
The following signed statements from the manufacturer, third-party observer and NJCAT are
required to complete the NJCAT verification process.
In addition, it should be noted that this report has been subjected to public review (e.g.
stormwater industry) and all comments and concerns have been satisfactorily addressed.
30
31
32
Center for Environmental Systems
Stevens Institute of Technology
Castle Point on Hudson
Hoboken, NJ 07030-0000
September 15, 2013
Elizabeth Dragon
Environmental Engineer
New Jersey Department of Environmental Protection
Bureau of Nonpoint Pollution Control
401-02B, PO Box 420
Trenton, NJ 08625-0420
Derek M. Berg
CONTECH Engineered Solutions LLC
71 US Route 1, Suite F
Scarborough, ME 04074
Forrest Bell
FB Environmental Associates Inc.
97A Exchange Street, Suite 305
Portland, ME 04101
To all,
Based on my review, evaluation and assessment of the testing conducted on the Continuous
Deflective Separator (CDS®) by Contech and observed by FB Environmental Associates, the
test protocol requirements contained in the “New Jersey Laboratory Testing Protocol to Assess
Total Suspended Solids Removal by a Hydrodynamic Sedimentation Manufactured Treatment
Device” (NJDEP HDS Protocol) were met or exceeded. Specifically:
Test Sediment Feed
The mean PSD of Contech’s test sediment complies with the PSD criteria established by the
NJDEP HDS protocol. The Contech PSD was plotted against the NJDEP PSD specification.
33
The Contech sediment gradation is equivalent to or finer than the NJDEP gradation at all points
along the curve. Overall, the Contech sediment blend contains more fines than the NJDEP
gradation, particularly below 50 microns. The median particle size of the Contech gradation is
approximately 60 microns.
Prior to the start of testing Contech procured a 2500 lbs. batch of scour sediment deemed
compliant with the scour sediment PSD specification defined in the NJDEP HDS Protocol. The
results of the three scour sediment PSD analysis confirmed that the batch of scour test sediment
procured by Contech is in compliance with the NJDEP scour test PSD specification.
Removal Efficiency Testing
In accordance with the NJDEP HDS Protocol, removal efficiency testing was executed on the
CDS-4 laboratory unit in order to establish the ability of the CDS to remove the specified test
sediment at 25%, 50%, 75%, 100% and 125% of the target MTFR. Prior to the start of testing
Contech reviewed existing data and decided to utilize a target MTFR of 0.93 cfs. This target was
chosen based on the ultimate goal of demonstrating greater than 50% annualized weighted solids
removal as defined in the NJDEP HDS Protocol. The flow rates, feed rates and influent
concentration all met the Test protocol’s coefficient of variance requirements and the
background concentration for all five test runs never exceeded 20 mg/L.
Scour Testing
In order to demonstrate the ability of the CDS to be used as an online treatment device scour
testing was conducted at greater than 200% of MTFR in accordance with the NJDEP HDS
Protocol. The average flow rate during the online scour test was 1.99 cfs, which is equivalent to
214% of the MTFR (MTFR = 0.93 cfs). With the exception of one background sample and one
effluent sample that both had concentrations of 4 mg/l all background and effluent samples were
measured as Non Detect during the online scour testing. These results confirm that the CDS-4
did not scour at 214% MTFR and meets the criteria for online use.
Maintenance Frequency
The predicted maintenance frequency for all models is 96 months.
Sincerely,
Richard S. Magee, Sc.D., P.E., BCEE
34
35
36
Center for Environmental Systems
Stevens Institute of Technology
One Castle Point
Hoboken, NJ 07030-0000
August 27, 2014
Lisa Schafer
Environmental Engineer
New Jersey Department of Environmental Protection
Bureau of Nonpoint Pollution Control
401-02B, PO Box 420
Trenton, NJ 08625-0420
To all,
Based on my review, evaluation and assessment of the scour retesting conducted on the
Continuous Deflective Separator (CDS®) by Contech and observed by Dr. Chris Berger, a
colleague of Dr. Scott Wells, from Portland State University, the scour test protocol requirements
contained in the “New Jersey Laboratory Testing Protocol to Assess Total Suspended Solids
Removal by a Hydrodynamic Sedimentation Manufactured Treatment Device” (NJDEP HDS
Protocol) were met or exceeded. The scour retesting was conducted to address concerns raised
during the public comment process that sediment that may have been deposited in the annular
area outside of the screening chamber during removal efficiency testing could subsequently
washout at higher flows.
During the retesting sediment meeting the NJDEP PSD scour test requirement was loaded to a
depth of four inches in this annular region and the scour testing repeated. The results confirmed
the earlier testing that the resulting effluent concentrations are all 3mg/l or less and well below
the 20mg/l threshold established by the NJDEP scour protocol. Therefore the CDS meets the
criteria for online use.
Sincerely,
Richard S. Magee, Sc.D., P.E., BCEE
37
8. References
Contech 2013. Verification Testing Report for the CONTINUOUS DEFLECTIVE SEPARATOR
(CDS®) Stormwater Treatment Device. Prepared by Contech Engineered Solutions LLC. July 1.
Contech 2014. NJDEP Scour Testing Results for the CDS-4. Prepared by Contech Engineered
Solutions, LLC. August 1.
NJDEP 2013a. New Jersey Department of Environmental Protection Procedure for Obtaining
Verification of a Stormwater Manufactured Treatment Device from New Jersey Corporation for
Advanced Technology. Trenton, NJ. January 25.
NJDEP 2013b. New Jersey Department of Environmental Protection Laboratory Protocol to
Assess Total Suspended Solids Removal by a Hydrodynamic Sedimentation Manufactured
Treatment Device. Trenton, NJ. January 25.
38
VERIFICATION APPENDIX
39
Introduction
• Manufacturer – Contech Engineered Solutions LLC, 9025 Centre Pointe Drive, West
Chester, OH 45069. General Phone: 800-338-1122. Website: http://www.conteches.com/
• MTD – Continuous Deflective Separator (CDS®) Stormwater Treatment Device. Model
numbers verified are shown in Table A-1 and Table A-2. Other CDS models (e.g.
CDS3020) may be available, however only the models listed in Tables A-1 and A-2 are
NJCAT verified/NJDEP certified. CDS units not listed in the Tables within the CDS-4
classification family are acceptable under the verification/certification as long as they
maintain the approved hydraulic loading rate, 2400 micron screen aperture and
proportional scaling to the test unit.
• TSS Removal Rate – 50%
• On-line installation
• 2400 micron perforated screen plate
• No sediment weir
Detailed Specification
• NJDEP sizing tables attached (Table A-1 and Table A-2).
• New Jersey requires that the peak flow rate of the NJWQ Design Storm event of 1.25
inch in 2 hours shall be used to determine the appropriate size for the MTD.
• Prior to installation Contech provides contractors detailed installation and assembly
instructions and is also available to consult onsite during installation.
• Maximum sediment depth prior to cleaning is 12 inches
• See Contech CDS® Inspection and Maintenance Guide – New Jersey for New Jersey
verified models maintenance guidance at:
http://www.conteches.com/products/stormwater-management/treatment/cds.aspx#1822141-
technical-info
• A hydrodynamic separator, such as CDS, cannot be used in series with another
hydrodynamic separator to achieve an enhanced removal rate for total suspended solids
(TSS) removal under N.J.A.C. 7:8-5.5.
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Table A-1 MTFRs and Required Sediment Removal Intervals for Common CDS Models
CDS
Model
Manhole
Diameter
(ft)
Maximum
Treatment Flow
Rate (cfs)
Effective
Treatment Area
(ft2)
Hydraulic Loading
Rate (gpm/ft2)
50% Max
Sediment
Storage Volume
(ft3)
Required
Sediment
Removal Interval
(Months)
CDS-3 3 0.52 7.07 33.22 7.1 96
CDS-4 4 0.93 12.57 33.22 12.6 96
CDS-5 5 1.5 19.63 33.22 19.6 96
CDS-6 6 2.1 28.27 33.22 28.3 96
CDS-7 7 2.8 38.48 33.22 38.5 96
CDS-8 8 3.7 50.27 33.22 50.3 96
CDS-10 10 5.8 78.54 33.22 78.5 96
CDS-12 12 8.4 113.10 33.22 113.1 96
*Sediment Removal Interval Calculated Using The "Monthly" Calculation In Section B, Appendix A of the NJDEP HDS Protocol
**Note that in some areas CDS units are available in additional diameters. Units not listed here are sized not to exceed 33.22gpm/ft2 of effective treatment
during the peak water quality flow and maintain proper geometric proportioning to the tested CDS-4
*** 50% Sediment Storage Capacity is equal to manhole diameter x 1ft of sediment depth. Each CDS has a 2ft deep sediment sump
Table A-2 Dimensional Overview for Common CDS Models
(Revised January 2017)
CDS
Model
Manhole
Diameter
(ft)
Treatment
Chamber Depth*
(ft)
Treatment
Chamber Wet
Volume (ft3)
Aspect Ratio
Depth/Dia**
Detention Time
at MTFR (sec)
Sediment Sump
Depth*** (ft)
Screen Plate
Dia./Depth (ft)
50% Max
Sediment
Storage Volume
(ft3)
Total Wet
Volume Including
Sediment Sump
(ft3)
CDS-3 3 3.5 24.74 1.17 71 2 1.5/1.5 7.1 31.81
CDS-4 4 3.50 43.98 0.88 70 2 2/1.5 12.6 56.55
CDS-5 5 3.75 73.63 0.75 74 2 2.5/2 19.6 93.26
CDS-6 6 4.50 127.23 0.75 84 2 3/3 28.3 155.50
CDS-7 7 5.25 202.04 0.75 94 2 3.5/3.5 38.5 240.52
CDS-8 8 6.00 301.58 0.75 104 2 4/4 50.3 351.85
CDS-10 10 7.50 589.03 0.75 124 2 5/5 78.5 667.57
CDS-12 12 9.00 1017.85 0.75 145 2 6/6 113.1 1130.94
*Treatment Chamber Depth is defined as the depth below the invert to the top of the false floor insalled at 50% sedimentation depth
**The aspect ratio of treatment chamber depth/unit diameter for the tested unit is 0.88. Unit depth is within 85% of the depth required to maintain this ratio across all models
***Each CDS model has 2ft of sump depth below the separation slab to accommodate sediment accumulation