Nj Treatment Design Manual

New Jersey Treatment Design Manual Screening Products

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NJ Manual

New Jersey Stormwater Treatment Design Manual

CONTECH Construction Products Inc. is a progressive, innovative company with a mission to preserve and protect water resources worldwide. We help customers achieve their water quality goals by providing treatment technologies that remove a variety of pollutants from stormwater runoff. These environmentally sound stormwater treatment products are specifically designed to meet National, State and Local regulations. This New Jersey Stormwater Treatment Design Manual was created as a guide to assist the design engineer in identifying and sizing the CONTECH Stormwater Solutions product(s) that best fit their site needs. This manual is to be used as a guide for design that complies with the April 2004 New Jersey Department of Environmental Protection (NJDEP) Best Management Practices (BMP) manual. Direct engineering support is available during all stages of project design. When one of our systems is specified, we can provide a complete technical design review. Due to the nature of continually evolving regulations, the information in this Manual may be changed periodically and updated as products are improved and new approvals are gained.

Support our Internal Engineering Team Provides Our internal team of engineers provides full support throughout all stages of project design and construction. Contact a CONTECH Stormwater Design Engineer (SDE) for assistance with any of the following needs:

• • • • • • • • • •

NJDEP water quality design storm hydrologic modeling Recommendation of the appropriate level of treatment for your site Stormwater treatment system sizing support and design documentation Design assistance with underground detention/infiltration system layout and sizing Engineering cost estimates for our treatment and detention systems H  ydraulic analysis of stormwater treatment system at both water quality design storm and peak storm flows Standard detail drawings or customized, site-specific detail drawings Specifications Operations and maintenance information Support through construction stage - submittal drawings, fabrication drawings, and installation guidelines

CONTECH Support Ron Long Stormwater Design Engineer P: 443.457.1508 E: [email protected]

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Nick Burns Stormwater Design Engineer P: 443.457.1533 E: [email protected]

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NJ Manual

Modeling the NJDEP Water Quality Design Storm

The first step in sizing any water quality structure is to model the water quality design storm. In New Jersey, the water quality design storm is defined in Chapter 5 of the NJDEP Stormwater BMP Manual. The water quality design storm is a variabledistribution storm, with a total rainfall depth of 1.25” and a total duration of two hours. The water quality design storm can be modeled using several methodologies, as outlined below.

NRCS Methodology Use the NRCS Methodology, with a TR-20 Runoff Method, to compute the water quality design storm peak runoff flow rate and/or total runoff volume. The rainfall distribution is defined on page 5-7 of the NJ Stormwater BMP Manual (shown below). For small, mostly impervious sites, it is recommended to separately calculate runoff rates from impervious drainage area and pervious drainage area. Using a weighted curve number is typically not appropriate, as it will result in artificially low runoff flow rates. The NRCS Methodology may be used to model the water quality design storm as routed through a detention facility.

Rational Method Use the rational method to compute the water quality design storm peak runoff flow rate. An IDF curve of the curve provided on page 5-8 of the NJ Stormwater BMP Manual (shown below). For most small sites, where the time of concentration is 10 minutes or less, a rainfall intensity of 3.2 inches per hour should be used. Q = C * i * A, where:

Q C i A



= peak runoff flow rate [cfs] = Rational method weighted runoff coefficient = rainfall intensity [in/hr], from IDF curve, based on time of concentration = total drainage area [acres]

Modified Rational Method Use the modified rational method to compute the water quality design storm total runoff volume. A common mistake is using the modified rational method to compute a peak runoff flow rate. An average rainfall intensity of 0.625 inches is not appropriate to use to calculate a peak water quality design storm runoff flow rate.

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NJ Manual

Filtration: StormFilter

StormFilter has received Final Certification from NJDEP as a stand-alone treatment device. StormFilter TSS removal rate as certified by NJDEP: 80% Number of Cartridges

Typical Structure Size

0.03

1

48" Manhole

0.06

2

48" Manhole

0.10

3

48" Manhole

0.13

4

72" Manhole

0.16

5

72" Manhole

0.20

6

72" Manhole

0.23

7

72" Manhole

0.26

8

8'x6' vault / 96" Manhole

StormFilter Sizing Table - 15gpm Cartridge1

Water Quality Treatment Flow Rate (cfs)

0.30

9

8'x6' vault / 96" Manhole

0.33

10

8'x6' vault / 96" Manhole

0.36

11

8'x11' vault / 96" Manhole

0.40

12

8'x11' vault / 96" Manhole

0.43

13

8'x11' vault / 96" Manhole

0.46

14

8'x11' vault / 96" Manhole

0.50

15

8'x11' vault

0.53

16

8'x11' vault

0.56

17

8'x11' vault

0.60

18

8'x11' vault

0.63

19

8'x11' vault

0.66

20

8'x11' vault

0.70

21

8'x11' vault

0.73

22

8'x11' vault

0.76

23

8'x14' vault

0.80

24

8'x14' vault

0.83

25

8'x14' vault

0.86

26

8'x14' vault

0.90

27

8'x14' vault

0.93

28

8'x14' vault

0.96

29

8'x14' vault

1.00

30

8'x14' vault

1.03

31

8'x14' vault

1.06

32

8'x16' vault

1.10

33

8'x16' vault

1.13

34

8'x16' vault

1.16

35

8'x16' vault

1.20

36

8'x16' vault

1.23

37

8'x16' vault

1.26

38

8'x18' vault

1.30

39

8'x18' vault

1.33

40

8'x18' vault

1.50

45

8'x20' vault

1.67

50

8'x24' vault

1.83

55

8'x24' vault

2.00

60

8'x24' vault

2.00+

60+

CONTACT CONTECH SDE

1For proper operation of the 15 gpm cartridge, CONTECH recommends 2.0’ of drop from system inlet pipe invert to outlet pipe invert.

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NJ Manual

Filtration: StormFilter Typical Structure Size

Water Quality Treatment Flow Rate (cfs)

Number of Cartridges

Typical Structure Size

0.02

1

48" Manhole

0.05

1

48" Manhole

0.04

2

48" Manhole

0.10

2

48" Manhole

0.06

3

48" Manhole

0.15

3

48" Manhole

0.08

4

72" Manhole

0.20

4

72" Manhole

0.11

5

72" Manhole

0.25

5

72" Manhole

0.13

6

72" Manhole

0.30

6

72" Manhole

0.15

7

72" Manhole

0.35

7

72" Manhole

0.17

8

8'x6' vault / 96" Manhole

0.40

8

8'x6' vault / 96" Manhole

0.20

9

8'x6' vault / 96" Manhole

0.45

9

8'x6' vault / 96" Manhole

0.22

10

8'x6' vault / 96" Manhole

0.50

10

8'x6' vault / 96" Manhole

0.24

11

8'x11' vault / 96" Manhole

0.55

11

8'x11' vault / 96" Manhole

0.26

12

8'x11' vault / 96" Manhole

0.60

12

8'x11' vault / 96" Manhole

0.28

13

8'x11' vault / 96" Manhole

0.65

13

8'x11' vault / 96" Manhole

0.31

14

8'x11' vault / 96" Manhole

0.70

14

8'x11' vault / 96" Manhole

0.33

15

8'x11' vault

0.75

15

8'x11' vault

0.35

16

8'x11' vault

0.80

16

8'x11' vault

0.37

17

8'x11' vault

0.85

17

8'x11' vault

0.40

18

8'x11' vault

0.90

18

8'x11' vault

0.42

19

8'x11' vault

0.95

19

8'x11' vault

0.44

20

8'x11' vault

1.00

20

8'x11' vault

0.46

21

8'x11' vault

1.05

21

8'x11' vault

0.48

22

8'x11' vault

1.10

22

8'x11' vault

0.51

23

8'x14' vault

1.15

23

8'x14' vault

0.53

24

8'x14' vault

1.20

24

8'x14' vault

0.55

25

8'x14' vault

1.25

25

8'x14' vault

0.57

26

8'x14' vault

1.30

26

8'x14' vault

0.60

27

8'x14' vault

1.35

27

8'x14' vault

0.62

28

8'x14' vault

1.40

28

8'x14' vault

0.64

29

8'x14' vault

1.45

29

8'x14' vault

0.66

30

8'x14' vault

1.50

30

8'x14' vault

0.69

31

8'x14' vault

1.55

31

8'x14' vault

0.71

32

8'x16' vault

1.60

32

8'x16' vault

0.73

33

8'x16' vault

1.65

33

8'x16' vault

0.75

34

8'x16' vault

1.70

34

8'x16' vault

0.77

35

8'x16' vault

1.75

35

8'x16' vault

0.80

36

8'x16' vault

1.80

36

8'x16' vault

0.82

37

8'x16' vault

1.85

37

8'x16' vault

0.84

38

8'x18' vault

1.90

38

8'x18' vault

0.86

39

8'x18' vault

1.95

39

8'x18' vault

0.89

40

8'x18' vault

2.00

40

8'x18' vault

1.00

45

8'x20' vault

2.25

45

8'x20' vault

1.11

50

8'x24' vault

2.50

50

8'x24' vault

1.22

55

8'x24' vault

2.75

55

8'x24' vault

1.33

60

8'x24' vault

3.00

60

8'x24' vault

1.33+

60+

CONTACT CONTECH SDE

2.00+

60+

CONTACT CONTECH SDE

StormFilter Sizing Table - 27” Tall 22.5gpm Cartridge3

Number of Cartridges

StormFilter Sizing Table - Low Drop 10gpm Cartridge2

Water Quality Treatment Flow Rate (cfs)

2 For proper operation of the 10 gpm cartridge, CONTECH recommends 1.5’ of drop

3 For proper operation of the 22.5 gpm cartridge, CONTECH recommends 2.75’ of drop

from system inlet pipe invert to outlet pipe invert.

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from system inlet pipe invert to outlet pipe invert.

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NJ Manual

Filtration: StormFilter

Typical StormFilter Off-line Layouts Vault and Manhole Configurations

Multiple off-line configurations are available. Contact a CONTECH SDE for assistance.

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NJ Manual

Filtration: StormFilter

StormFilter Sizing Methodologies Flow-based Design

As stand-alone treatment, the StormFilter system may be designed as a flow-based system, sized to treat the water quality design storm peak runoff flow rate. Use the following equation to determine the number of StormFilter cartridges required to treat a given water quality flow rate:

(round up to the nearest cartridge)

Qcartridge refers to the operating flow rate of the StormFilter cartridge. Typically, the cartridge operating flow rate is 15 gallons per minute per cartridge. There are applications where a different cartridge operating flow rate may be recommended. A Contech Stormwater Design Engineer will assist you in selecting the appropriate cartridge operating flow rate.

Downstream of Quantity Detention / Mass Load Sizing Design

When a detention basin is being designed for quantity control, it is ideal to place the StormFilter downstream of the detention basin. The StormFilter will only need to be sized to treat the peak water quality design storm discharge flow rate from the basin, which will be substantially less than the water quality design storm peak runoff flow rate flowing in to the basin. When placed downstream of detention, it is important to check the estimated annual sediment mass load contributing to the StormFilter. This mass load is important to check to ensure minimum operating life cycle of the StormFilter. The mass load can be estimated based on a contributing impervious drainage area, land use, average annual rainfall depth, and level of pretreatment provided. The StormFilter cartridge mass load capacity may vary depending on the selected cartridge operating rate. Contech recommends providing an adequate number of cartridges for a minimum of a 12-month maintenance cycle. Contact a Contech Stormwater Design Engineer to assist with the mass load sizing.

Routing Design Using Minimum Detention

Providing detention upstream of the StormFilter is beneficial, even when quantity control is not required. The detention system may be designed solely for the purpose of detaining the water quality design storm. Since the New Jersey water quality design storm has such a high peak rainfall intensity, a relatively small amount of detention storage can provide a significant reduction in the peak flow rate to be treated. Upsize the conveyance pipe a few diameters, or design a small detention facility to attenuate the water quality design storm peak flow rate. A Contech Stormwater Design Engineer can model your site hydrology and provide a routing design recommendation.

Use as Pretreatment in a Treatment Train

Multiple treatment systems may be used in series to achieve higher TSS removal rates, as per equation 4-1 on page 4-3 of the NJ Stormwater BMP Manual. BMPs must be arranged in order of ascending TSS removal. An HDS system, rated at 50% TSS removal, can be placed upstream of an extended detention basin, rated at 60% TSS removal, for a total calculated 80% TSS removal.

Volume-based Design

There are some situations where a flow-based StormFilter design is not feasible, typically when hydraulic constraints exist. When these conditions occur, the StormFilter may be designed as a volume-based system. Using this design method, the entire volume generated by the water quality design storm must be captured in a storage facility upstream of the StormFilter. The absolute minimum number of cartridges will be necessary – only enough to meet the desired maintenance interval.

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NJ Manual

Filtration: StormFilter

Recommended Design Practices Provide Adequate Physical Drop

In order for the StormFilter cartridge’s siphon to activate, the water elevation within the StormFilter cartridge bay must rise up to the top of the cartridge. However, it is important to minimize the volume required to activate the cartridge. In order to minimize this activation volume, it is recommended to design the StormFilter system with physical drop between the inlet pipe invert and outlet pipe invert. The drop requirement varies depending on the cartridge operating flow rate. Refer to the StormFilter Sizing Table for recommended drop for each cartridge operating flow rate. There are situations where less than the recommended drop will be acceptable. Contact a Contech SDE to discuss options when there is limited drop available.

Provide Adequate Depth

The StormFilter system requires personnel entry for maintenance. At a minimum, Contech Stormwater Solutions recommends providing 4.0’ of internal height from the finished floor to the inside ceiling within the cartridge bay. Due to the thickness of the cartridge bay floor, concrete top slab, and access frames, it is recommended to provide a minimum of 5.5’ of depth from the lowest grade elevation to outlet pipe invert. There are several options available when depth is limited. These options include large access doors, casting access frames into the top slab of the vault, or even using a different StormFilter configuration. Please contact a Contech Stormwater Design Engineer to discuss options when there is limited depth available.

Reduce Water Quality Flow Rates Using Upstream Storage Facility

If depth is available, oversize stormwater conveyance pipes and design an outlet control structure to attenuate the water quality design storm peak flow rate. Even when quantity control is not required, design a small detention facility designed just for the water quality design storm. This will ensure that the full volume generated by the water quality design storm is treated, yet it will also allow for a smaller, and more cost-effective, treatment system.

Design in an Off-line Configuration

In order to prevent washout of captured sediment during storm events greater than the water quality design storm, it is recommended to design a high-flow bypass structure. A bypass structure will allow the design treatment flow rate to flow to the StormFilter, yet direct higher flows to a bypass pipe. There are several bypass structure configurations available, including a high/low pipe configuration, or a diversion weir wall configuration, such as the StormGate. Contact a Contech Stormwater Design Engineer to provide assistance modeling the StormFilter system hydraulics, and provide a recommended bypass weir elevation.

Pre-Treat Subsurface Infiltration Basins

Per NJDEP requirements, subsurface infiltration basins must be pretreated to 80% TSS removal (page 9.5-6 of the New Jersey Stormwater BMP Manual). The StormFilter will provide this level of treatment. Note that rooftop runoff is considered clean and does not require pretreatment. When recharge is required, target rooftop runoff for infiltration and reduce or eliminate the treatment system.

Consider System Maintenance Design Life Cycle and Accessibility

The StormFilter requires regular inspection and maintenance to ensure optimal performance. Consider the system location within the site plan to ensure maintenance vehicles/crew accessibility to the system. In most design scenarios, the expected StormFilter maintenance cycle is approximately 18-36 months. The minimum recommended design maintenance life is 12 months. Actual maintenance frequency will ultimately depend on rainfall and site pollutant loading. Additional maintenance information is available through a Contech Stormwater Design Engineer.

Important Links StormFilter NJDEP Final Certification Letter: http://www.njstormwater.org/docs/treatment_final_cert_stormfilter.pdf

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NJ Manual

Hydrodynamic Separation: CDS/Vortechs/VortSentry

TSS Removal Credit Certified by the NJDEP: 50%

Water Quality Treatment Flow Rate (cfs)

HDS Model

Internal Structure Size W x L (ft) or Diameter (ft)

Maximum Pipe Size (in)

Minimum Depth Rim to Invert *

Typical Depth Invert to Bottom of Structure

Vortechs System 0.63

Vortechs 1000

3x9

15

3' - 6"

3' - 6"

1.12

Vortechs 2000

4 x 10

18

3' - 9"

3' - 6"

1.75

Vortechs 3000

5 x 11

24

4' - 3"

3' - 6"

2.52

Vortechs 4000

6 x 12

30

4' - 9"

3' - 6"

3.43

Vortechs 5000

7 x 13

36

5' - 3"

3' - 6"

4.48

Vortechs 7000

8 x 14

36

5' - 3"

3' - 6"

5.67

Vortechs 9000

9 x 15

36

5' - 3"

3' - 6"

7.00

Vortechs 11000

10 x 16

36

5' - 3"

3' - 6"

10.08

Vortechs 16000

12 x 18

36

5' - 3"

3' - 6"

11.82

Vortechs: PC 1319

13 x 19

CONTACT SDE

CONTACT SDE

3' - 6"

13.71

Vortechs: PC 1421

14 x 21

CONTACT SDE

CONTACT SDE

3' - 6"

CDS System 0.70

CDS2015-W

5

30

3' - 0"

5' - 2"

1.10

CDS2020-W

5

36

3' - 6"

5' - 9"

1.60

CDS2025-W

5

36

3' - 6"

6' - 1"

2.00

CDS3020-W

6

48

4' - 0"

5' - 9"

3.00

CDS3030-W

6

48

4' - 0"

6' - 9"

4.50

CDS4030-W

8

48

4' - 0"

7' - 9"

6.00

CDS4040-W

8

48

4' - 0"

8' - 9"

7.50

CDS4045-W

8

48

4' - 0"

9' - 5"

9.00

CDS5640-DW

8 (+ diversion box)

CONTACT SDE

CONTACT SDE

9' - 5"

14.0

CDS5653-DW

8 (+ diversion box)

CONTACT SDE

CONTACT SDE

11' - 2"

19.0

CDS5668-DW

8 (+ diversion box)

CONTACT SDE

CONTACT SDE

12' - 7"

25.0

CDS5678-DW

8 (+ diversion box)

CONTACT SDE

CONTACT SDE

13' - 7"

VortSentry System 0.46

VortSentry VS30

4

12

4' - 0"

5' - 11"

1.10

VortSentry VS40

4

18

4' - 6"

7' - 0"

2.15

VortSentry VS50

5

18

4' - 6"

7' - 6"

3.71

VortSentry VS60

6

24

5' - 0"

8' - 11"

5.90

VortSentry VS70M

8

30

5' - 6"

10' - 2"

8.80

VortSentry VS80

8

30

5' - 6"

10' - 2"

* For Higher Flow Rates Call a CONTECH SDE

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NJ Manual

Hydrodynamic Separation: CDS/Vortechs/VortSentry

Typical Offline Layouts

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Hydrodynamic Separation: CDS/Vortechs/VortSentry

Recommended Design Practices No Physical Drop Required

HDS technologies require no physical drop; therefore, the inlet and outlet pipe inverts may be set to the same elevation. For shallow sites, HDS systems are easily implemented within the drainage system.

Consider Hydraulic Impact

HDS systems require hydraulic head to operate at design flow rate. Typical head loss through an HDS system may range from 0.5’ to 2.0’ at the water quality flow rate, and potentially up to 4.0’ at peak storm flow rate for larger systems. A Contech SDE can prepare a stage-discharge curve for the design engineer to model within the stormwater conveyance system.

Design in an Off-line Configuration

In order to prevent washout of captured sediment during storm events greater than the water quality design storm, it is recommended to design a high-flow bypass structure. A bypass structure will allow the design treatment flow rate to flow to the treatment system, yet direct higher flows to a bypass pipe. There are several bypass structure configurations available, including a high/low pipe configuration, or a diversion weir wall configuration, such as the StormGate. Contact a Contech Stormwater Design Engineer to provide assistance modeling the treatment system hydraulics, and provide a recommended bypass weir elevation.

Use as Pretreatment in a Treatment Train

Multiple treatment systems may be used in series to achieve higher TSS removal rates, as per equation 4-1 on page 4-3 of the NJ Stormwater BMP Manual. BMPs must be arranged in order of ascending TSS removal. An HDS system, rated at 50% TSS removal, can be placed upstream of an extended detention basin, rated at 60% TSS removal, for a total calculated 80% TSS removal.

Avoid Placing Downstream of Detention

HDS system are ideally located upstream of a detention basin. Pre-treating the stormwater flow prior to discharge into a detention basin will result in an increased maintenance interval for the basin. Contrarily, if the HDS system is located downstream of a detention system, most of the sediment will fall out in the basin, and the HDS system will not provide significant treatment. In addition, due to operating head loss, an HDS system located downstream of a detention basin will cause a backwater condition on the basin outlet control structure, potentially altering the stage-discharge relationship of the basin.

Provide Systems in Parallel, Avoid Systems in Series

Two systems can be designed in parallel to treat a water quality flow rate that is twice what one system can handle. A splitter structure can be used to evenly split the flows to the two parallel HDS systems, and also provide high-flow bypass. However, use of two or more HDS systems in series is discouraged. Two like systems in series does not meet the criteria of a treatment train.

Consider System Maintenance Design Life Cycle and Accessibility

HDS systems do not require personnel access for maintenance. However, consideration should be taken to locate the system within the site plan so a vacuum truck can easily operate within range of the system. On average, HDS systems require annual removal of accumulated pollutants. Actual maintenance frequency will ultimately depend on rainfall and site pollutant loading. Additional maintenance information is available through a Contech SDE.

Important Links CDS NJDEP Conditional Interim Certification Letter: http://www.njstormwater.org/docs/treatment_int_cert_higheffcds_contech.pdf

Vortechs NJDEP Conditional Interim Certification Letter: http://www.njstormwater.org/docs/treatment_vortech_cic.pdf

VortSentry NJDEP Conditional Interim Certification Letter: http://www.njstormwater.org/docs/treatment_vortsentry_cic.pdf

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