Flint Hills/Fort Riley Joint Land Use Study (JLUS)

The Flint Hills Joint Land Use Study (pdf) (JLUS 2005) and the Flint Hills/Fort Riley JLUS Update (2017) are both the outcome of a collaborative planning effort among the local governments of Clay, Geary and Riley Counties; the cities of Grandview Plaza, Junction City, Manhattan, Milford, Ogden, Wakefield and Riley; and Fort Riley representatives in an effort to increase awareness of growth and development plans and issues in the areas around Fort Riley.  Both studies help to ensure growth in the surrounding areas is compatible with the operations on Fort Riley.

One of the main issues of concern is that military operations at Fort Riley create noise. The noise created is not continuous and different kinds of noises are created by different military operations (e.g. aircraft rotor noise, vehicle engine noise and large caliber weapons firing noise). All noise is measured in decibels (dB), but there are a variety of descriptors for the various kinds of noises. One widely accepted descriptor of noise created by large caliber weapons firing and other loud blast noise is the Impulsive Day-Night Level (CDNL) metric. 

Blast noise from large caliber weapons is noise of short duration (typically less than one second) of especially high intensity, with abrupt onset and rapid decay. Noise generated by firing large weapons systems is measured by using a 'C-weighting.' Though the impulsive noise associated with large weapons systems can cause vibration that may make nearby buildings shake, the noise is air-borne. Vibration is not transmitted through the ground as a result of mortar or artillery impact on Fort Riley, but instead travels through the air as a shock wave. It is this wave that causes vibration and windows to rattle. People tend to find large caliber blast noise more annoying that small arms noise.

Blast noise from large caliber weapons is created both during the day and during the night at Fort Riley as the large weapons are sometimes fired around the clock. To account for that, blast noise from large caliber weapons averaged over all hours of the day is frequently described using the day-night level (DNL) of that noise. The DNL adds a 10 dB penalty to blast noise created at night because the large caliber weapons fired at night are frequently more easily heard than those firing during the day when there is more other noise that partially masks the sound of the large caliber weapons being fired.

Thus a widely accepted measurement of blast noise is its dB CDNL. The Environmental Noise Program, US Army Public Health Command used Fort Riley's weapons firing data to create the Fort Riley Noise Contour Map (pdf). The noise zones on this map represent the average noise levels (i.e. the average dB CDNL) expected to be generated by large caliber weapons firing at Fort Riley over the course of an entire year. The zones reflect that there are times of relative quiet - periods when weapons are not being fired - as well as times when weapons are fired on Fort Riley, sometimes 24 hours a day, seven days a week.

The following provides an explanation of the various noise zones shown on the 'Fort Riley Average Noise Levels' map:

Noise Zone III – the area around a noise source in which the C-weighted day-night sound level (CDNL) is greater than 70 dB (demolition and large caliber weapons), the A-weighted day-night level (ADNL) is greater than 75 dB (aviation), or the dB Peak is greater than 104 (small caliber weapons). The average large caliber weapons firing noise level in this zone is generally considered to conflict with almost all activities and to, particularly conflict with sensitive land uses, such as housing, schools, medical facilities, and places of worship.

Noise Zone III currently does not occur off the installation.

Noise Zone II – the area around a noise source in which the CDNL is 62-70 dB (demolition and large caliber weapons), the ADNL is 65-75 dB (aviation), or the dB Peak is 87-104 (small caliber weapons). The Army recommends limiting the use of land in this to activities that are not noise-sensitive - such as industry, manufacturing, transportation and agriculture.

Noise Zone I – included all areas around a noise source in which the CDNL is less than 62 dB (demolition and large caliber weapons), the ADNL is less than 65 dB (aviation), or the dB Peak is less than 87 (small caliber weapons). This area is usually suited for all types of land use activities.

Land Use Planning Zone (LUPZ) - The noise environment at the installation varies daily and seasonally because operations are not consistent 365 days a year. To provide a planning tool that can be used to account for days of higher than average operations, a LUPZ is included on this noise zone map. The LUPZ is 5 dB lower than Zone II and encompasses areas where, during periods of increased military operations, community annoyance levels can reach those associated with Zone II. The LUPZ can offer a prediction of noise impacts when levels of operations are above average. While residential and other noise sensitive land uses may generally be compatible with the typical noise levels present within a LUPZ, potential increased annoyance levels during training operations may warrant the utilization of design and structural noise level reduction measures, to reduce interior noise levels during periods of increased military operations. Additionally, low residential densities are warranted within the LUPZ to reduce the likelihood of potential future land use conflicts.

In 2019, a document entitled “Noise Attenuation Guidelines”, prepared for the Flint Hills Regional Council by Henderson Engineers, Inc., was completed and adopted. The document includes a discussion of the type of noise generated by Fort Riley and suggestions for building methods that could help reduce the noise impacts. It is recommended by local authorities that property owners consider using these construction methods in new construction or remodeling projects.

For more information, contact Monty Wedel at 785-537-6332.