Virginia Administrative Code › Title 12 - HEALTH › Agency 5 - DEPARTMENT OF HEALTH › Chapter 610 - SEWAGE HANDLING AND DISPOSAL REGULATIONS › Part IV - General Criteria for the Selection of a Wastewater Treatment and Disposal System Based on Site Conditions › Article 3 - Systems Using Fill Material › Section 12VAC5-610-597 - Fill systems

Current through Register Vol. 40, No. 24, July 15, 2024
A. Fill systems
					 are systems where the infiltrative surface and some portion of the treatment
					 medium is comprised of fill material and not a naturally occurring undisturbed
					 soil. Fill systems may be located in-ground, shallow-placed, or above ground.
					 Fill systems addressed in these regulations are the Wisconsin Mound system, the
					 noncarbonaceous mountain colluvium system, and the sand-on-sand
					 system.
B. Elevated Sand Mounds.
					 Septic tank effluent may be utilized with elevated sand mounds. Pretreatment
					 shall be required when effluent strength exceeds residential strength
					 wastewater and may be required where hydrologic conditions meet the minimum
					 criteria contained in this chapter. For the purpose of siting an elevated sand
					 mound, the criteria in Table 4.4 shall apply. For the purposes of establishing
					 minimum setback distances between an elevated sand mound and various structures
					 or topographic features, the mound shall be considered an absorption field and
					 distances shown in Table 4.2 utilized.
C. Sand-on-sand systems. Sand-on-sand is a
					 process of modifying a soil absorption system site using fill material which is
					 similar in texture to the original, naturally occurring material. Filling is
					 accomplished in accordance with
					 12VAC5-610-965.
1. Criteria for utilizing septic effluent.
					 Septic tank effluent may be utilized with sand-on-sand systems. For the purpose
					 of siting a sand-on-sand system, the criteria in Table 4.4 shall apply.
					 Sand-on-sand systems may be utilized with septic tank effluent when the
					 following criteria are met:
a. Soil texture.
					 In order to assure effluent dispersal under adverse conditions, while
					 maintaining adequate treatment capacity, shallow-placed systems are limited to
					 Texture Group I and IIa soils. The use of Texture Group IIb, III and IV soils
					 for sand-on-sand systems is prohibited.
b. Soil structure. Sand-on-sand is restricted
					 to soils classified as entisols (i.e., a young soil with no horizon
					 development) and which have a texture of sand, loamy sand, coarse sandy loam,
					 or sandy loam texture.
c. Depth of
					 soil. A minimum of 18 inches of naturally occurring undisturbed soil, measured
					 from the ground surface, is required before encountering soils with bedrock, or
					 a seasonal or permanent water table. Additionally, to assure adequate hydraulic
					 dispersal capacity, no restrictive horizons may occur within 30 inches of the
					 ground surface.
d. Separation
					 distances. Table 4.2 contains the minimum setback distances between an
					 absorption field and various structures or topographic features.
e. Estimated or measured infiltration rates.
					 When siting a sand-on-sand system, the estimated or measured infiltration rate
					 shall not exceed 30 minutes per inch within the sidewall area of the trench or
					 within 18 inches of the infiltrative interface where effluent encounters
					 undisturbed soil.
f. Slope.
					 Sand-on-sand is prohibited where the slope of the original site exceeds
					 5%.