#611 ON-SITE TESTING AND EVALUATION

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1 OBJECTIVES: After completing this chapter, you will be able to... Establish the number of soil test probes necessary to adequately evaluate a site. Determine where to place the soil test probes for conventional onlot systems. Revised MEETING THE CERTIFICATION, TRAINING, AND RESOURCE NEEDS OF PENNSYLVANIA S SEWAGE ENFORCEMENT OFFICERS

2 Soil Test Probe Once isolation distances have been established and suitable slopes are measured, the location and number of soil test probes may be selected. The soil test probe is used to characterize the actual soil conditions throughout a proposed absorption area. Within the probe, soil profi le descriptions are prepared and limiting condition depths are noted. Individual onlot system designs are most often based upon limiting zone depths. The local agency SEO must conduct suffi cient testing to assure that the minimum required soil depths for the absorption area can be maintained. Every absorption area type has its own specifi c size and dimension. Data collected from each test probe determines site suitability and system design options. The number and placement of the soil test probes will vary for each site. The soil test probe is used to characterize the soil conditions within a proposed absorption area. MEETING THE CERTIFICATION, TRAINING, AND RESOURCE NEEDS OF PENNSYLVANIA S SEWAGE ENFORCEMENT OFFICERS

3 Number of Probes Title 25, Chapter The number of soil test probes required to evaluate a potential absorption area is determined by several factors: Whether the site is evaluated for planning or permitting. Whether a specifi c number of probes are required by the standards for a specifi c onlot system and/or any additional local agency requirements. Whether variable soil conditions exist that require further review. Multiple probes may be required to properly evaluate a proposed absorption area. MEETING THE CERTIFICATION, TRAINING, AND RESOURCE NEEDS OF PENNSYLVANIA S SEWAGE ENFORCEMENT OFFICERS

4 Probe Placement According to the regulations, a soil test probe must be located within 10 feet of the absorption area. The number and distribution of soil probes are typically based upon the proposed absorption area type. This spacing will vary for individual site conditions and specifi c absorption area options. CONVENTIONAL ABSORPTION AREAS This chapter provides a review of the number and placement of soil test probes for conventional onlot absorption areas and spray fi elds. These are identifi ed in Chapter 73 as bed, trench, or elevated sand mound absorption areas and the spray fi eld for an individual residential spray irrigation system (IRSIS). Soil probe placement for alternate technology absorption areas that differ from conventional absorption area proposals will be covered in Chapter 9. For more information on the construction of conventional absorption area types, review Sections through of the regulations for beds, trenches, and elevated sand mounds. Review Section for spray fields. Table B in Section lists the required spray field areas (square footage) that correspond to the slope and soil characteristics on a site. MEETING THE CERTIFICATION, TRAINING, AND RESOURCE NEEDS OF PENNSYLVANIA S SEWAGE ENFORCEMENT OFFICERS

5 Probe Placement CONVENTIONAL ABSORPTION AREAS (continued) The SEO will usually anticipate the type of absorption area proposed before selecting the location for individual soil test probe excavations. This may be based upon previous testing in the area or soil survey data mapping projections. The placement of the soil test probes at each site is generally infl uenced by the following: Estimated soil limiting condition depths Actual slope measured Projected system design fl ows Although the regulations only require one soil test probe for some conventional absorption areas, most SEOs will evaluate two or more for each system. Most often, a proposed absorption area is bracketed by these probes. A backhoe excavation is frequently made at both ends of a site situated along ground surface contours. Beds, trenches, and sand mound systems may require an average length of 60 to 80 feet. Multiple probes must accommodate both the length and width of the absorption area at each site. The number of required soil test probes is often associated with the SEO s familiarity with the local soil conditions and the type of proposed absorption area. The objective is to accurately characterize the soil conditions, regardless of how many holes are necessary. Excavate enough probes to assure that the proposed absorption area is consistent with the soil conditions noted. MEETING THE CERTIFICATION, TRAINING, AND RESOURCE NEEDS OF PENNSYLVANIA S SEWAGE ENFORCEMENT OFFICERS

6 Probe Placement IRSIS SPRAY FIELDS The placement of soil test probes for most conventional system absorption areas is primarily based upon the local agency SEO s recommendation. The location and placement of test probes for an IRSIS spray fi eld are more specifi - cally established by the regulations. Section 73.14(b)(2) requires at least four soil test probes evenly spaced throughout spray fi elds up to 20,000 square feet. Section 73.14(b)(3) requires that probes are evenly spaced at intervals of 100 feet or less for spray fi elds in excess of 20,000 square feet. Table B of Section of the regulations presents the required IRSIS spray fi eld square footage for various site conditions. The total required area for each spray fi eld is based upon the following: Number of bedrooms Slope Depth to water table Depth to rock MEETING THE CERTIFICATION, TRAINING, AND RESOURCE NEEDS OF PENNSYLVANIA S SEWAGE ENFORCEMENT OFFICERS

7 Probe Placement The SEO considers many factors when selecting the locations for the soil test probes. Before excavating any probes for an onlot system absorption area, the following must always be addressed: Horizontal isolation distances Slope within absorption area Proposed design fl ows Type of absorption area Estimated permeability Ground surface contours Using multiple probes is encouraged, and bracketing the proposed absorption area with probes is recommended for most conventional technologies. Conventional absorption areas are most often installed along ground surface contours, perpendicular to slope. IRSIS spray fields take up a much larger area and do not need to be placed along contour. Go to Chapter 5 Workbook to complete the following exercises: Exercise 5-1: Absorption Area Probes Exercise 5-2: IRSIS Spray Field Probes MEETING THE CERTIFICATION, TRAINING, AND RESOURCE NEEDS OF PENNSYLVANIA S SEWAGE ENFORCEMENT OFFICERS

8 KEY POINTS: Before any soil test probes are excavated, the SEO should determine the required number and location. Soil test probe locations are often based upon the proposed absorption area type. Ground surface contours will affect most absorption area installations. Suffi cient testing should ensure the proposed system will correspond to the soil conditions on site. Go to the #611 Chapter 5 materials to print and complete the Chapter 5 Quiz. This quiz was designed to check your understanding of the chapter materials. MEETING THE CERTIFICATION, TRAINING, AND RESOURCE NEEDS OF PENNSYLVANIA S SEWAGE ENFORCEMENT OFFICERS