A. Location.

1. Noise attenuating structures may be constructed only on residential properties which abut an arterial or collector street right-of-way or a public right-of-way which is classified by the city’s master transportation plan as a principal or minor arterial or a residential collector street.

2. With prior approval of the public works department, noise attenuating structures may be constructed on the public right-of-way line, if the encroachment into any drainage or utility easement does not exceed thirty (30) inches from the public right-of-way line or adjacent to streets at a point at least ten feet away from the paved portion (including curb and gutter or the nearest outer edge of the earthen ditch to the public right-of-way line) of the roadway.

3. No spread footing, post, column or berm shall be placed over an existing utility structure.

B. Definitions. For purposes of this section, the following terms shall have the following meanings:

1. “LEQ” means the equivalent steady state sound level which in a stated period of time would contain the same acoustic energy as the time-varying sound level during the same time period.

2. “dB(A)” means the sound level measure in decibels obtained through use of the A scale.

C. Noise Thresholds.

1. A noise attenuating structure may be constructed only if the proposed structure will reduce the LEQ by at least five dB(A) during the period of the highest noise level conditions, measured at a point on the property five feet above the natural grade at the principal building on the property. The duration of the test to determine whether the proposed noise attenuating structure reduces the LEQ shall be a minimum of fifteen (15) minutes.

2. A noise attenuating structure may be constructed only at locations where the LEQ equals or exceeds sixty-five (65) dB(A) during any fifteen (15) minute period within the one hour of the day that the property where the LEQ is measured experiences the highest noise levels. The hour of peak noise levels shall be determined by the city engineer, in consultation with the applicant, based on traffic studies of the adjacent roadway and other factors affecting noise levels in the area. An application for a noise attenuating structure may request the construction of the structure on or adjacent to properties which do not meet the noise level standards set forth in this subsection if the noise attenuating structure is a continuous structure and if at least fifty-one (51) percent of the properties abutting the street right-of-way where the noise attenuating structure is to be constructed meet the noise thresholds set forth in this subsection. In addition, fifty-one (51) percent of the properties along each street frontage shall meet the LEQ requirement set forth in this section for the properties along that frontage to be eligible for the construction of a noise attenuating structure.

3. In determining whether fifty-one (51) percent of the properties meet the LEQ requirement set forth in this section, a licensed acoustical engineer retained by the applicant shall establish a sampling procedure which identifies typical property conditions, in terms of distance from the public right-of-way to principal structures and traffic levels. The acoustical engineer shall conduct noise level testing at properties typifying each prototype situation for fifteen (15)-minute intervals during the hour of peak noise levels during at least one day; which day shall be chosen by mutual consent of the city engineer and the applicant.

4. To demonstrate that the reduction in LEQ will be achieved, the applicant shall submit a stamped report from a licensed acoustical engineer which shall include a model of the anticipated noise reduction. The report shall also analyze the reflective characteristics of the wall material and the possible impacts on adjacent properties of reflective noise. The cost of such analysis shall be paid by the applicant.

D. Design Standards.

1. Height.

a. Except when facing an interstate highway or a principal arterial, berms and wall panels measured together shall not exceed eight feet in height.

b. Berms or walls which face an interstate highway or a principal arterial shall not exceed twelve (12) feet in height.

c. Columns may be twelve (12) inches higher than panels but not greater in cross-sectional area than five square feet.

d. A combination of a wall on a berm shall be permitted, but the combined height of wall and berm shall not exceed eight feet or twelve (12) feet in height, as applicable.

e. If topography or construction requirements so dictate, noise attenuating structures may exceed the height limitations of this section by up to twelve (12) inches.

2. No noise attenuating structure shall be constructed in such a manner as to obstruct the sight distance of traveling motorists at roadway intersections or driveway entrances.

3. Additional Requirements. In addition to the foregoing standards, noise attenuating structures constructed as walls shall be:

a. Constructed with: brick; masonry other than cinder block; concrete in combination with brick; or concrete masonry block, such as but not limited to Unibrick (trade name), Slumpblock (trade name), Estateblock (trade name) or Soundblox (trade name);

b. Constructed with low maintenance materials, with columns located no farther apart than seventy-five (75) feet;

c. Designed, and the design stamped, by a registered professional engineer; and

d. Wherever possible, set back from the traveled portions of streets and sidewalks so as to provide an adequate pedestrian corridor for safe and convenient passage and to avoid the creation of narrow passageways between the noise wall and the street.

E. Maintenance.

1. Noise attenuating structures located on private property shall be maintained by the property owner or the homeowners’ association, as applicable.

2. Noise attenuating structures located on city-owned property or public rights-of-way shall be maintained by the city.