Section 410IAC6-10.1-79. Subsurface trench on-site sewage system type selection criteria

   (a) On-site sewage system feasibility, location, and selection shall be based on the:

(1) site evaluation;

(2) information obtained from the on-site soils evaluation; and

(3) DDF.

  (b) A subsurface trench gravity system may be constructed if the:

(1) DDF of the project is equal to or greater than four hundred fifty (450) gallons per day;

(2) soil loading rate of the site is equal to or greater than twenty-five hundredths (0.25) gallons per day per square foot and equal to or less than seventy-five hundredths (0.75) gallons per day per square foot, as determined from Table V in section 78(b)(8) of this rule;

(3) trench bottoms will be at least thirty (30) inches above any horizon with:

(A) a soil loading rate less than twenty-five hundredths (0.25) gallons per day per square foot or greater than seventy-five hundredths (0.75) gallons per day per square foot;

(B) any soil horizon in a soil developed from Wisconsin glacial till that shows effervescence when treated with a ten percent (10%) hydrochloric acid solution, unless:

(i) the on-site soils evaluation report shows that the presence of the horizon is not detrimental to the proper functioning of an on-site sewage system; and

(ii) the determination in item (i) is made using the guidelines as set forth in the soil manuals, technical bulletins, and handbooks of the NRCS guidelines and as approved by the department;

(C) less than twenty percent (20%) clay by volume and greater than thirty-five percent (35%) coarse fragments by volume; or

(D) greater than or equal to twenty percent (20%) clay by volume and greater than sixty percent (60%) coarse fragments by volume; and

(4) soil absorption system, including either half of a subsurface trench alternating field on-site sewage system, is designed with a total absorption trench length that does not exceed five hundred (500) lineal feet.

  (c) A subsurface trench gravity on-site sewage system may also be constructed if the:

(1) DDF of the proposed on-site sewage system is less than four hundred fifty (450) gallons per day;

(2) site has a soil loading rate of equal to or greater than twenty-five hundredths (0.25) gallons per day per square foot and equal to or less than seventy-five hundredths (0.75) gallons per day per square foot, as determined from Table V in section 78(b)(8) of this rule;

(3) trench bottoms will be at least twenty-four (24) inches above any horizon with:

(A) a soil loading rate less than twenty-five hundredths (0.25) gallons per day per square foot or greater than seventy-five hundredths (0.75) gallons per day per square foot;

(B) any soil horizon in a soil developed from Wisconsin glacial till that shows effervescence when treated with a ten percent (10%) hydrochloric acid solution, unless:

(i) the on-site soils evaluation report shows that the presence of the horizon is not detrimental to the proper functioning of an on-site sewage system; and

(ii) the determination in item (i) is made using the guidelines as set forth in the soil manuals, technical bulletins, and handbooks of the NRCS guidelines and as approved by the department;

(C) less than twenty percent (20%) clay by volume and greater than thirty-five percent (35%) coarse fragments by volume; or

(D) greater than or equal to twenty percent (20%) clay by volume and greater than sixty percent (60%) coarse fragments by volume; and

(4) soil absorption system, including either half of a subsurface trench alternating field on-site sewage system, is designed with a total absorption system trench length that does not exceed five hundred (500) lineal feet.

  (d) A subsurface trench on-site sewage system that utilizes alternating fields or is dosed using pump assisted distribution may be constructed if the:

(1) soil loading rate of the site is equal to or greater than twenty-five hundredths (0.25) gallons per day per square foot and equal to or less than seventy-five hundredths (0.75) gallons per day per square foot, as determined from Table V in section 78(b)(8) of this rule; and

(2) trench bottoms will be at least twenty-four (24) inches above any horizon with:

(A) a soil loading rate less than twenty-five hundredths (0.25) gallons per day per square foot;

(B) any soil horizon in a soil developed from Wisconsin glacial till that shows effervescence when treated with a ten percent (10%) hydrochloric acid solution, unless:

(i) the on-site soils evaluation report shows that the presence of the horizon is not detrimental to the proper functioning of an on-site sewage system; and

(ii) the determination in item (i) is made using the guidelines as set forth in the soil manuals, technical bulletins, and handbooks of the NRCS guidelines and as approved by the department;

(C) less than twenty percent (20%) clay by volume and greater than thirty-five percent (35%) coarse fragments by volume; or

(D) greater than or equal to twenty percent (20%) clay by volume and greater than sixty percent (60%) coarse fragments by volume.

  (e) If any soil absorption system, including either half of an alternating field on-site sewage system, is designed with a total absorption trench length greater than five hundred (500) lineal feet, the absorption system shall be dosed using pump assisted distribution.

  (f) If any soil horizon within twenty-four (24) inches of the proposed trench bottom has a soil loading rate of one and twenty-hundredths (1.20) gallons per day per square foot as determined from Table V in section 78(b)(8) of this rule, the on-site sewage system shall utilize pressure distribution. (Indiana State Department of Health; 410 IAC 6-10.1-79; filed Oct 19, 2012, 2:07 p.m.: 20121114-IR-410120157FRA)