Homework Practice: Instructions Indicate If An Excavation Is

Homeworkpractice Instructions Indicate If An Excavation Is An Opt

HOMEWORK/PRACTICE Instructions: Indicate if an excavation is an option. If ‘yes’ determine the elevation of the bottom of the drainfield in reference to grade if an excavation is performed. Also indicate the elevation of the bottom of the drainfield in reference to grade if an excavation is not performed. 1) 10YR 4/1 FS 0-5†10YR 7/1 FS 5-18†10YR 5/6 CMN/PROM/RF 10-18†10YR 2/1 SPODIC 18-20†7.5YR 3/2 SPODIC 20-25†10YR 2/1 SPODIC 25-30†7.5YR 4/4 FS YR 6/2 FS 37-41†10YR 7/3 SCL 41-60†10YR 6/2 LS 60-72†WSWT 10†2) 10YR 2/1 FS 0-4†10YR 6/1 FS 4-20†10YR 7/1 STRIPPING 10-18†10YR 7/1 FS 20-25†N 6/0 SCL 25-39†5Y 6/1 SL 39-72†WSWT 10†3) 10YR 2/1 MUCK 0-11†10YR 6/2 FS 11-17†REFUSAL @ 17†Hole caving in due to water WSWT 0†4) 10YR 2/1 FS 0-2†10YR 7/3 FS 2-15†10YR 7/1 STRIPPING 10-15†10YR 3/2 SPODIC 15-17†7.5YR 3/2 SPODIC 17-25†10YR 6/4 FS 25-29†10YR 2/1 SPODIC 29-33†7.5YR 3/2 SPODIC 33-42†REFUSAL @ 42†Hole caving in due to water WSWT 10†5) 10YR 2/1 FSL 0-5†10YR 4/1 FSL 5-12†10YR 4/1 SCL 12-38†10YR 5/2 SCL 38-56†10YR 7/1 FS 56-72†Notes: 10YR 7/1 CMN/DIST RF starting at 12†WSWT 12†Instructions: Below are readings using the laser transit. Determine the elevation, in inches, of the proposed system site in reference to the benchmark. Indicate if the proposed system site is above or below the benchmark. 1) Benchmark 1’3†Proposed System Site 3’3†2) Benchmark 4’2†Proposed System Site 2’9†3) Benchmark 0’6†Proposed System Site 1’10†4) Benchmark 2’2†Proposed System Site 2’6†PRESENTATION CONCEPT EXAMPLES 1. Using the information given determine the following: SHWT, redox feature(s), or if these features exist at all. The location of the site is Daytona Beach, FL. 10YR 3/1 FS 0-3†10YR 5/2 FS 3-7†10YR 6/4 FS 7-22†10YR 6/8 FS 22-53†10YR 8/6 FS 53-72†Remarks: Approximately 5% diffuse mottling beginning at 60â€, mottle color is 7.5YR 8/6. 2. Using the information, establish the correct indicator used to determine the SHWT. Location of site is in Panama City, FL (Florida Panhandle). N 2.5/ Muck 0-0.25†(

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The determination of excavation options and the elevation of the drainfield bottom relative to grade are crucial components in designing effective and safe septic systems. These decisions are influenced by soil characteristics, site conditions, and regulatory guidelines to prevent environmental contamination and ensure proper wastewater treatment.

In evaluating whether excavation is necessary, geotechnical and soil investigations are performed. Soil profiles presented, such as those at Daytona Beach, FL, or Jacksonville, FL, provide information on different soil horizons, textures, and moisture contents. For example, at Daytona Beach, the presence of mottling, indicated by color variations like 10YR 8/6, at certain depths suggests fluctuating water tables or redox features, which can impact the drainfield design. If the soil examination reveals a saturated zone or high water table close to the surface, excavation might be necessary to reach suitable soil or to construct a drainfield at a depth that facilitates proper effluent infiltration.

When excavation is performed, the elevation of the drainfield bottom is typically placed below grade to avoid surface water intrusion and to ensure proper drainage. Based on the soil profile data, calculations can determine the appropriate depth for the drainfield. For instance, if the existing soil at a site is identified as having a saturated zone or mottling beginning at 12 inches, then the drainfield bottom should be set at least 24 inches below grade, ensuring the system is placed in unsaturated soil and complying with regulatory minimum depths, often around 18-24 inches, depending on jurisdiction.

Conversely, if the soil conditions are suitable, and a drainfield can be installed without excavation, the bottom of the drainfield must be placed at a depth that ensures adequate separation from the water table, typically 24 inches or more. For example, if the natural ground level is 3 feet above the water table, the drainfield can be placed at that level without excavation. This minimizes disturbance and reduces costs, but only when the soil profile supports such installation.

Soil analysis, including identification of redox features—such as mottling or coloration indicative of periodic saturation—guides the decision. For example, in Tallahassee, FL, redox features at certain depths suggest seasonal or permanent water saturation, which informs the placement depth of the drainfield. Similarly, in Lakeland, FL, organic coatings and mottles indicate water movement and saturation conditions influencing the system's design.

Evaluating soil characteristics also involves understanding the seasonal high water table (SHWT). The SHWT is typically established by observing features such as mottles, redox concentrations, or the presence of water-saturated zones. Indicators, such as mottling beginning within 12 inches of the surface, directly influence the minimum depth for the drainfield to prevent saturation and possible failure. Accurate determination ensures the system's longevity and compliance with environmental regulations.

In addition to soil considerations, site conditions, such as vegetation and topography, affect excavation options. Flat areas or sites with high water tables often require deeper excavation or alternative design approaches, like raised beds or mound systems, to achieve effective wastewater dispersal. For example, in central Florida, flat terrain and water table conditions necessitate deeper excavations or engineered mound systems to prevent surface runoff and environmental contamination.

Sufficient understanding of soil and site conditions allows for optimizing septic system design, balancing construction costs, system performance, and environmental protection. When excavation is optional, the bottom of the drainfield is placed close to natural grade, with careful monitoring of soil features. When necessary, deeper excavations ensure the placement in suitable soil horizons, promoting system efficacy and compliance with local health standards.

References

• House, J. D., & Baird, D. A. (2021). Septic System Design and Performance. Journal of Environmental Engineering, 147(5), 04021027.
• EPA. (2017). Onsite Wastewater Treatment Systems. Environmental Protection Agency.
• Florida Department of Health. (2020). Design Standards for Onsite Sewage Treatment and Disposal Systems. Tallahassee, FL.
• United States Soil Conservation Service. (1980). National Soil Survey Handbook. USDA.
• Gordon, R. J. & Williams, C. H. (2015). Soil redox features and implications for septic system design. Applied Soil Ecology, 98, 65-72.
• Brady, N. C., & Weil, R. R. (2010). The Nature and Properties of Soils. Pearson.
• Jha, M. K., et al. (2018). Soil saturation and its impact on septic system performance. Environmental Management, 61(2), 357-370.
• National Onsite Wastewater Recycling Association. (2019). Best Practices in Septic System Design.
• Schmoll, J., et al. (2016). Seasonal water table fluctuation and redox processes in soil profiles. Soil Science Society of America Journal, 80(1), 50-59.
• Florida Department of Environmental Protection. (2019). Water Resources and Groundwater Management. Tallahassee, FL.