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Waste Management Division > Programs/Bureaus/Units > Solid Waste Technical Assistance Section >

Frequently Asked Questions

The questions below relate to Stormwater.

Do I discharge to a Municipal Separate Storm Water System? What is Sheet Flow? What should I do if all I have is sheet flow on my facility or if my facility is located such that water does not run into the surface waters? What types of endangered species must I be concerned about? We share our facility with the Town Public Works Department. Do we need to file multiple NOIs and develop plans for each?

Do I discharge to a Municipal Separate Storm Water System? A Municipal Separate Storm Water System is defined as a publicly owned conveyance or system of conveyances from ditches, curbs or underground pipes that divert storm water into the surface waters of the state. Technically, this means that the town drainage ditches on the side of the road will count as a storm water system if they drain to a brook, marsh, stream or river. If your facility drains to this "system", you need to check box 5b as a "YES" and fill in the name of the town.

What is Sheet Flow? Sheet flow is flow over a plane surface at shallow depths of about 1-inch or less. For natural watersheds, sheet flow occurs in the upper reaches of the watershed, does not exceed 300 feet in length, and generally does not exceed 100 feet in length (after this point, it has channelized into what is referred to as shallow concentrated flow. On large pavement surfaces flow could remain as sheet flow for greater lengths than described above but it would be such a rare occurrence that you probably shouldn’t consider it. The key to this is that after about 100 feet, the flow channelizes enough that a grab sample could be obtained. Once this becomes the case, the facility would fall under the requirements of the NPDES Storm Water Permit system and a Notice of Intent or a Non-exposure Certification would need to be filed and a Storm Water Pollution Prevention Plan would need to be developed and implemented. If it is impossible to obtain a sample, even during a very intense rain storm, all you have is sheet flow."

What should I do if all I have is sheet flow on my facility or if my facility is located such that water does not run into the surface waters? If you can make an assessment of your facility and all you have is sheet flow that does not enter the surface water and there is no place you can reasonably sample the flow, you are exempt from filing under the NPDES permit. Any flow percolates into the ground. An example would be a facility built in an old gravel pit or on sand. You may need other permits but you would not need a Storm Water Permit. This is not to say that you should not do anything. You will not have to submit a Notice of Intent or a No Exposure Certification. However, it is a good idea to document your reasoning for exclusion in a memorandum or letter and place the signed letter in a file. This will allow anyone that may inspect your facility to understand that you have at least considered the need to apply for a Storm Water Permit.

What types of endangered species must I be concerned about? The NPDES permit system in New Hampshire is administered by the United States Environmental Protection Agency and not the New Hampshire Department of Environmental Services. Because of this, you need only to be concerned about federally listed endangered species. In New Hampshire, these are the Dwarf Wedge Mussel and the Shortnose Sturgeon. However, the best management practices you will put in place to comply with the permit will also help ensure protection of the New Hampshire listed species.

We share our facility with the Town Public Works Department. Do we need to file multiple NOIs and develop plans for each? No. The primary activity at the site is required to file the NOI and a single SWPPP must be developed by the town. In the NOI, the town must list the additional SIC codes and Sectors in Parts C.6. and C.7. for additional activities occurring at the site. Similarly, the SWPPP must address the requirements of all sectors in the MSGP that have activities present at the site.

NH Department of Environmental Services | 29 Hazen Drive | PO Box 95 | Concord, NH 03302-0095
(603) 271-3503 | TDD Access: Relay NH 1-800-735-2964 | Hours: M-F, 8am-4pm