Stormwater Manufactured Treatment Devices

An MTD is required to be NJCAT verified and NJDEP certified when the MTD is used to satisfy the requirements of the Stormwater Management rule (N.J.A.C. 7:8) , as a result of triggering the requirements for major development.

For projects receiving New Jersey Environmental Infrastructure Financing Program (NJEIFP) funding, an MTD must be either: 1) NJCAT verified and NJDEP certified or 2) installed using the NJEIFP MTD Funding Policy.

An MTD which is not NJCAT verified or NJDEP certified may be used as long as the MTD is not intended to satisfy the requirements of the Stormwater Management rule and is not subject to NJEIFP MTD Funding Policy.

Please note that any MTD installed should be listed on the MS4 permittee’s inventory of stormwater management measures and must be properly maintained by the responsible party. Other state, federal, and local requirements may apply.

Green Infrastructure Guidance for MTDs (April 23, 2020)

For an MTD to be considered “green infrastructure” in accordance with the March 2, 2020 amendments to the Stormwater Management rules at N.J.A.C. 7:8, the MTD must meet the GI definition noted at amended N.J.A.C. 7:8-1.2.Specifically, the MTD shall (1) infiltrate into the subsoil; and/or (2) treat stormwater runoff through filtration by vegetation or soil.

A certified GI MTD that has models having maximum allowable drainage area greater than 2.5 acres shall be subject to the 2.5 acres of maximum contributory drainage area limitation as required in N.J.A.C. 7:8-5.3(b) when the model is designed to satisfy the the groundwater recharge and/or stormwater runoff quality standards at N.J.A.C.7:8-5.4 and 5.5.

An MTD that uses a bio-filtration media and can be configured “above ground” and incorporate a tree box, planter box, or shrubs, etc., would meet the GI definition. Any MTD with bio-filtration media that would be placed “below ground” as a vault without any vegetation can be considered GI (for NJ purposes) only if the device infiltrates stormwater into the subsoil. Further, the below ground device (vault) would need to meet the NJDEP BMP Manual conditions (see Appendix E) of having the soil below the MTD meet the minimum tested infiltration rate of one inch per hour, have at least two feet of separation from the seasonal high water table, and infiltrate into the subsoil.

Revised Sizing Calculation for MTDs (July 17, 2023)

Take note that the Rational Method can no longer be used in the calculation of stormwater runoff pursuant to the Stormwater Management rules at N.J.A.C. 7:8–5.7(a)1 in effect on July 17, 2023. Accordingly, the Natural Resources Conservation Service (NRCS) methodology and the MTD sizing calculations using the NRCS methodology as demonstrated in Chapter 9.5 and Chapter 11.3 of the last published NJDEP BMP Manual shall supplant the sizing calculations in all MTD certification letters that contain the Rational Method to the extent of the rule applicability set forth at N.J.A.C. 7:8–1.6.

The table below includes the listing of MTDs that are NJCAT verified and NJDEP certified under the updated procedures and protocols dated January 25, 2013. Visit the NJCAT website for more information.

The certifications below for HDS MTDs are valid only when the proposed configuration of an MTD, including all internal components, is the same as the tested configuration and the MTD is installed with the same inlet/outlet pipe angles tested. It should be further noted that multiple inlet pipes and/or grate configurations have not been verified or certified. Any deviation from the tested configuration, including the use of alternative inlet/outlet pipe angles, multiple inflow pipes, and/or grate inlets, will prevent the MTD from being awarded the certified TSS removal rate and may result in non-compliance with the Stormwater Runoff Quality Standard.

Green Infrastructure (GI) MTDs

MTDs NOT Considered GI