(1) Only professional engineers, designers, or local health officers may perform soil and site evaluations. Soil scientists may only perform soil evaluations.
(2) The person evaluating the soil and site shall:
(a) Report:
(i) A sufficient number of soil logs to evaluate conditions within:
(A) The initial soil dispersal component; and
(B) The reserve area.
(ii) The groundwater conditions, the date of the observation, and the probable maximum height;
(iii) The topography of the proposed initial system, the reserve area, and those areas immediately adjacent that contain characteristics impacting the design;
(iv) The drainage characteristics of the proposed initial system, the reserve area and those areas immediately adjacent that contain characteristics impacting the design;
(v) The existence of structurally deficient soils subject to major wind or water erosion events such as slide zones and dunes;
(vi) The existence of designated flood plains and other areas identified in the local management plan required in WAC
246-272A-0015; and
(vii) The location of existing features affecting system placement, such as, but not limited to:
(A) Wells and suction lines;
(B) Water sources and supply lines;
(C) Surface water and stormwater infiltration areas;
(D) Abandoned wells;
(E) Outcrops of bedrock and restrictive layers;
(F) Buildings;
(G) Property lines and lines of easement;
(H) Interceptors such as footing drains, curtain drains, and drainage ditches;
(I) Cuts, banks, and fills;
(J) Driveways and parking areas;
(K) Existing OSS; and
(L) Underground utilities;
(b) Use the soil and site evaluation procedures and terminology in accordance with Chapter 5 of the On-site Wastewater Treatment Systems Manual, EPA 625/R-00/008, February 2002 except where modified by, or in conflict with, this chapter (available upon request to the department);
(c) Use the soil names and particle size limits of the United States Department of Agriculture Natural Resources Conservation Service classification system;
(d) Determine texture, structure, compaction and other soil characteristics that affect the treatment and water movement potential of the soil by using normal field and/or laboratory procedures such as particle size analysis; and
(e) Classify the soil as in Table V, Soil Type Descriptions:
TABLE V
Soil Type Descriptions
Soil Type | Soil Textural Classifications |
1 | Gravelly and very gravelly coarse sands, all extremely gravelly soils excluding soil types 5 and 6, all soil types with greater than or equal to 90% rock fragments. |
2 | Coarse sands. |
3 | Medium sands, loamy coarse sands, loamy medium sands. |
4 | Fine sands, loamy fine sands, sandy loams, loams. |
5 | Very fine sands, loamy very fine sands; or silt loams, sandy clay loams, clay loams and silty clay loams with a moderate or strong structure (excluding platy structure). |
6 | Other silt loams, sandy clay loams, clay loams, silty clay loams. |
7 Unsuitable for treatment or dispersal | Sandy clay, clay, silty clay, strongly cemented or firm soils, soil with a moderate or strong platy structure, any soil with a massive structure, any soil with appreciable amounts of expanding clays. |
(3) The owner of the property or his agent shall:
(a) Prepare the soil log excavation to:
(i) Allow examination of the soil profile in its original position by:
(A) Excavating pits of sufficient dimensions to enable observation of soil characteristics by visual and tactile means to a depth three feet deeper than the anticipated infiltrative surface at the bottom of the soil dispersal component; or
(B) Stopping at a shallower depth if a water table or restrictive layer is encountered;
(ii) Allow determination of the soil's texture, structure, color, bulk density or compaction, water absorption capabilities or permeability, and elevation of the highest seasonal water table; and
(b) Assume responsibility for constructing and maintaining the soil log excavation in a manner to prevent injury as required by chapter
296-155 WAC.
(4) The local health officer:
(a) Shall render a decision on the height of the water table within twelve months of receiving the application under precipitation conditions typical for the region;
(b) May require water table measurements to be recorded during months of probable high-water table conditions, if insufficient information is available to determine the highest seasonal water table;
(c) May require any other soil and site information affecting location, design, or installation; and
(d) May reduce the required number of soil logs for OSS serving a single-family residence if adequate soils information has previously been developed.