N.J. Admin. Code § 7:13-12.7

Current through Register Vol. 56, No. 24, December 18, 2024

Section 7:13-12.7 - Requirements for a bridge or culvert

(a) This section sets forth the design and construction standards under which the Department will issue an individual permit for the construction or reconstruction of a bridge or culvert in any regulated area. A footbridge that does not meet the requirements of permit-by-rule 23 at N.J.A.C. 7:13-7.23 or general permit 12 at N.J.A.C. 7:13-9.12 is subject to the requirements of this section.

(b) To demonstrate compliance with this section, all calculations and analyses used in the design of a bridge or culvert shall be submitted to the Department. Applicants are encouraged to discuss prospective bridge and culvert projects with Division staff prior to undertaking detailed calculations and analyses under this section. The Department can offer assistance regarding the types of calculations and analyses most appropriate for a given site and project, and in some cases, may be able to determine that the requirements of this section are satisfied without review of detailed calculations or analyses.

1. For the purpose of determining compliance with this section, all calculations shall be rounded to the nearest 0.1 feet.

(c) The Department shall issue an individual permit to construct a new bridge or culvert or to reconstruct an existing bridge or culvert only if the bridge or culvert and any associated construction, such as embankments, abutments, footings, and travel surfaces, are designed to remain stable, scour resistant, and resistant to displacement and/or damage during the flood hazard area design flood. At a minimum, a bridge shall have stable abutments, a culvert shall have stable headwalls, and any abutment and headwall shall have footings that extend no less than three feet below the invert of the channel.

(d) In addition to meeting the requirements at (c) above, the Department shall issue an individual permit to construct a new bridge or culvert only if the following requirements are met:

1. The anticipated impacts to offsite flooding associated with the construction of the bridge or culvert comply with (d)1i and ii below for each flood event described at N.J.A.C. 7:13-12.1(i):

i. The proposed construction does not subject any offsite habitable building, railroad, roadway, or parking area to increased depth or frequency of flooding; and

ii. For all areas not identified in (d)1i above, the proposed construction does not increase offsite flood depths by more than 0.2 feet at any location;

2. It is demonstrated, through one or more of the following hydrologic and hydraulic analyses comparing existing and proposed conditions, that the bridge or culvert complies with (d)1 above, unless it is demonstrated that alternate methods would more accurately model the existing and/or proposed conditions:

i. A standard step backwater analysis, which is generally capable of modeling both existing and proposed conditions, provided the area upstream of the project is not a permanent impoundment of water or would become a level pool during the flood being analyzed;

ii. A hydrologic routing, which is generally capable of modeling only proposed conditions; and

iii. An inlet/outlet control analysis, which is generally capable of modeling only proposed conditions; and

3. Where a new bridge or culvert and/or the railroad or roadway it serves would cause fragmentation of habitat for terrestrial threatened or endangered species and/or any terrestrial species of special concern, the bridge or culvert incorporates a preserved or restored natural bank of sufficient width to allow the species to pass through the structure. Where a natural bank is not present or feasible to preserve or restore, the applicant shall create an artificial bank or shelf of sufficient width to allow the species to pass through the structure. The applicant shall additionally adopt appropriate measures where necessary to encourage the species to pass through the structure.

(e) In addition to meeting the requirements at (c) above, the Department shall issue an individual permit to reconstruct an existing bridge or culvert only if the following requirements are met:

1. The anticipated impacts to offsite flooding associated with the reconstruction of the bridge or culvert comply with (e)1i through iii below for each flood event described at N.J.A.C. 7:13-12.1(i):

i. The proposed construction does not subject any offsite habitable building, railroad, roadway, or parking area to increased depth or frequency of flooding;

ii. The proposed construction does not increase offsite flood depths within 500 feet upstream and downstream of the project by more than 0.2 feet, unless compliance with (e)3 below necessarily results in greater increases. In no case shall the project increase offsite flood depths by more than one foot within 500 feet upstream and downstream of the project; and

iii. The proposed construction does not increase offsite flood depths in areas located more than 500 feet upstream and downstream of the project.

2. It is demonstrated through one or more of the following hydrologic and hydraulic analyses comparing existing and proposed conditions, that the bridge or culvert complies with (e)1 above, unless it is demonstrated that alternate methods would more accurately model existing and/or proposed conditions:

i. A standard step backwater analysis, which is generally capable of modeling both existing and proposed conditions, provided:

(1) The area upstream of the project is not a permanent impoundment of water, or would become a level pool during the flood being analyzed. In such a case a hydrologic routing is generally more effective; and

(2) The analysis takes into account any potential downstream effect of a decrease in water surface elevations upstream of the bridge or culvert, as described in (e)2ii below;

ii. A hydrologic routing, provided the analysis takes into account any potential downstream effect of a decrease in water surface elevations upstream of the bridge or culvert under proposed conditions. A significant loss of upstream flood storage can occur in such cases, which can result in increased flow rates downstream of the bridge or culvert. Generally, such impacts can be effectively analyzed by performing a hydrologic routing of existing and proposed structures to determine downstream flow rates, modeling these flow rates in a standard step backwater analysis, and then comparing the water surface profile under existing and proposed conditions; and

iii. An inlet/outlet control analysis, provided the analysis does not indicate a decrease in water surface elevations upstream of the bridge or culvert during any flood event described at N.J.A.C. 7:13-12.1(i).

3. Where the existing bridge or culvert and/or the railroad or roadway it serves currently causes fragmentation of habitat for terrestrial threatened or endangered species and/or any terrestrial species of special concern, the bridge or culvert incorporates a preserved or restored natural bank of sufficient width to allow the species to pass through the structure. Where a natural bank is not present or feasible to preserve or restore, the applicant shall create an artificial bank or shelf of sufficient width to allow the species to pass through the structure. The applicant shall additionally adopt appropriate measures where necessary to encourage the species to pass through the structure.

(f) The Department shall issue an individual permit to construct a new bridge or culvert or to reconstruct an existing bridge or culvert only if the new or reconstructed structure is a bridge, arch culvert, or three-sided culvert that meets the requirements of (f)1 through 4 below, unless the applicant demonstrates that a circular, elliptical, or box culvert is acceptable under (g) and (h) below.

1. The bridge or culvert completely spans the regulated water and, to the extent feasible, matches or exceeds the dimensions of the existing channel so that the size and shape of the natural channel is preserved through the structure;

2. The bridge or culvert is adequately sized to convey the flood hazard area design flood without a significant increase in the velocity of water in the channel;

3. Any existing stable, natural, earthen channel with low-flow aquatic passage is preserved, to the maximum extent practicable, and stable, earthen low-flow aquatic passage is provided within the bridge or culvert as well as any section of channel disturbed to accommodate its construction; and

4. No armoring is placed under or across the channel bed, unless such armoring is necessary to prevent scour along the proposed abutments or footings. In such a case, the armoring shall be buried beneath at least two feet of native substrate, where placement of the native substrate is feasible and effective in stabilizing the channel and protecting aquatic habitat under expected flood conditions.

(g) The construction or reconstruction of a circular, elliptical, or box culvert is conditionally acceptable where one or more of the conditions listed at (g)1 through 6 below exist and the culvert meets the construction standards at (h) below.

1. The regulated water does not possess a discernible channel;

2. The channel does not contain fishery resources;

3. The channel is manmade (not including any water that historically possessed a naturally-occurring, discernible channel, which has been modified by humans);

4. The channel is fully lined with manmade impervious material such as cement or concrete;

5. The channel is less than 10 feet in width as measured between the top of bank of each side of the channel; or

6. Spanning the channel under (f) above would not be practicable due to one or more of the following physical constraints:

i. Unstable substrate, which would likely undermine any proposed footing within or adjacent to the channel;

ii. Irregular channel configuration;

iii. Anticipated adverse hydraulic impact to the channel; or

iv. Anticipated adverse impacts to offsite flooding, the environment, or public safety.

(h) Where a circular, elliptical, or box culvert is found acceptable under (g) above, the culvert shall be constructed as follows:

1. The invert of the culvert shall be installed at least two feet below the invert of the natural channel. In order to create a contiguous flow-path through the culvert that meets and matches the bottom inverts, cross-sections, and profile of the channel beyond the culvert, the culvert shall be filled with native substrate up to the invert of the natural channel; or

2. Where it is demonstrated that the culvert cannot be constructed as described at (h)1 above due to unstable substrate or other physical constraints, the floor of the culvert shall be constructed to incorporate an artificial low-flow treatment, such as a V-notch or key-notch, baffles to hold substrate in place, or a concave floor. For example, an artificial low-flow treatment can be used where the placement of two feet of substrate within the culvert would not be feasible or effective in stabilizing the channel and protecting aquatic habitat under expected flood conditions.

N.J. Admin. Code § 7:13-12.7

Adopted by 48 N.J.R. 1067(a), effective 6/20/2016