NAC445A.9674. Calculation of required size of effluent absorption area.

     1. The required size of the effluent absorption area for an on-site sewage disposal system must be calculated based on the long-term acceptance rate of the soil at the site, unless the system uses an elevated mound system or an intermittent sand filter system for effluent absorption. An elevated mound system or an intermittent sand filter system must use the table set forth in NAC 445A.9686 for determining the size of the absorption area. The long-term acceptance rate, as determined by either the percolation rate of the soil or soil texture, must be determined in accordance with the following table:

Long-Term Acceptance Rates (LTAR) for Wastewater

Application to Soil Absorption Systems

Percolation Rate (minutes/inch)	Typical Soil Textures	Maximum Loading Rate/LTAR (gallons/square foot/day)
≤ 5	Gravel to Coarse to Medium Sand	See NAC 445A.9666
6-10	Fine Sand to Loamy Sand	1.1
11-20	Sandy Loam to Loam	1.0
21-30	Loam	0.7
31-40	Loam to Silty Loam	0.5
41-60	Clay Loam to Clay	0.4
Over 60	Silty Clay Loam/Silty Clay	0.2

     2. The absorption area required for an on-site sewage disposal system, unless an elevated mound system or intermittent sand filter system is used, must be calculated as Q/LTAR=A, where:

     (a) “A” is the absorption area required;

     (b) “Q” is the average projected daily sewage flow based on septic tank or other treatment unit size; and

     (c) “LTAR” is the long-term acceptance rate of the soil at the site.

Ê For example, if a 3,000 gallon septic tank is proposed and the site consists of loam with a long-term acceptance rate of 0.7 gallons per square foot per day, the calculation would be 3,000 gallons per day divided by 0.7 gallons per square foot per day for a total required absorption area of 4,286 square feet. Thus, the required septic tank capacity determined from the table set forth in NAC 445A.9656 must be divided by the long-term acceptance rate from the table set forth in this section to determine the minimum absorption area required.

     (Added to NAC by Environmental Comm’n by R194-07, eff. 8-26-2008)