Soil Evaluation Process

Once the proper application forms and fees are submitted, and a backhoe operator has been hired, the procedure for a soil evaluation normally goes as follows:

Marking the test hole locations
  1. The designing engineer and/or soil evaluator visits the site in order to decide where the soil evaluation test holes should be dug, and mark two location with stakes, paint, or flagging tape. Two soil test holes must be dug (one uphill, one downhill), and the soil evaluation test holes must be located in the area of the proposed leaching field. Although the soil evaluation takes place before the septic system design, it is best to discuss with an engineer the general location of the house and/or other structures to be built so that the septic system is located correctly on the landscape. A land surveyor may have already located and marked the property boundaries at the site, which can be very useful.The proximity of other landscape features, such as wetlands (including rivers, streams, and ponds), drinking water wells & reservoirs, and other site restrictions are also investigated at this time due to regulatory requirements. In any instance, a USGS topographic maps and the soil survey of the property, should be studied before arriving on-site.
    USGS Topographic Map Soil Survey
    Digging the test holes
  2. On the day of the evaluation, the soil evaluator and backhoe operator arrive on-site before the inspector arrives (in Rhode Island, this is a DEM representative) to conduct the evaluation. Inspections by DEM personnel may be waived at their discretion. The backhoe operator then digs two “shallow” holes in the predetermined locations to a depth of 5-feet, if possible.
  3. The soil evaluator then enters the test holes and performs the soil evaluation.
    Performing the soil evaluation
  4. Discussing the soil evaluation with an inspector

    The inspector arrives and reviews the soil evaluation form for accuracy. Since soil conditions vary, the soil evaluator and inspector may discuss the findings of the evaluation and come to a conclusion about the soil conditions. If the soil evaluator and inspector agree, parameters such as seasonal high water table and perc rate are finalized then and there. However, in certain cases, additional testing may be required. If the soil evaluator and inspector do not reach an agreement about the depth to the seasonal high water table, or the soil is difficult to interpret (certain soils are identified in the ISDS regulations that fit this description), a wet season determination is necessary.

  5. Once the soil evaluator and inspector come to a conclusion, the “deep” test holes are excavated. This is done by digging the “shallow,” 5-foot holes to a depth of 10-feet, if possible. Neither soil evaluator nor inspector enters the hole at this depth due to danger concerns, but observe from the ground surface for evidence of water tables, water seepage, limiting layers such as ledge or hardpan, etc.
    Digging the “deep” hole Backfilling the test hole
  6. Once the deep hole is finished, a 10-foot long, 4-inch diameter perforated PVC pipe is installed in the hole, and backfilled. The field portion of the soil evaluation is now complete.
  7. Handing the completed soil evaluation to RIDEM

    The soil evaluator then takes the information gained from the evaluation, transfers it to a clean sheet (dirt normally stains the field copies), and either mails or hand delivers copies to the Rhode Island DEM. The DEM will then send signed copies to the soil evaluator and the applicant. Once this accomplished, copies of the soil evaluation may be sent to the designing engineer.

    For more information about soils, septic systems, and permitting in Rhode Island, visit the following web sites:

    URI Onsite Wastewater Training Center
    Rhode Island Department of Environmental Management ISDS Program
    Rhode Island Home *A* Syst (click on Septic Systems under Topics)
    EPA Septic System Overview