Section 250-RICR-150-10-6.16 - Soil EvaluationA. Soil Evaluation Required - A soil evaluation shall be required for an OWTS Application for New Building Construction, for an OWTS Application for Alteration of a Structure, and for an OWTS Application for Repair for non-residential uses in accordance with § 6.18 of this Part.B. Validity of Field Data - Field data shall be considered valid for a period of five (5) years from the time of initial certification by the Department or five (5) years from the date of initial approval of any OWTS application, design, or subdivision suitability where the data were used, whichever occurred most recently. Field data older than five (5) years may be used provided that §§ 6.16(B)(1) through (3) of this Part are met. Field data cannot be renewed independent of an OWTS application or subdivision site suitability certification application. 1. The field conditions are essentially unchanged;2. The field data was initially compiled and certified after July 20, 1987 for subdivisions or after December 31, 1992 for individual lots; and3. Its continuing validity is properly certified on the OWTS application or Application for Subdivision Site Suitability Certification.C. Soil Evaluation Requirements - The soil evaluation shall be prepared on forms approved by the Director. The soil evaluation shall contain a site sketch and the information in §§ 6.16(C)(1) through (6) of this Part. The information in §§ 6.16(C)(1) and (2) of this Part shall be completed by a Soil Evaluator, and may be required to be witnessed by the Director in accordance with § 6.16(E) of this Part. The information in items §§ 6.16(C)(3) through (6) of this Part shall be determined by a Class II or III Licensed Designer or a Soil Evaluator. The test holes excavated for the soil evaluation shall be within the area of the proposed leachfield as described in § 6.16(I) of this Part. 2. Identification of the seasonal high groundwater table in accordance with § 6.16(M) of this Part; 3. General description of slope;4. Presence of any watercourse within two hundred feet (200') of the proposed leachfield;5. Presence of any drains that may influence the seasonal high groundwater table; and6. Approximate location of property lines.D. Soil Evaluation Application - An application form shall be submitted to the Director by the Soil Evaluator prior to conducting the soil evaluation field work on the site. Such application will be on forms approved by the Director and will require, at a minimum, a locus map and photocopy of the relevant page or section thereof from the U.S. Department of Agriculture Soil Survey with the site location marked. The Director shall determine if the soil evaluation must be witnessed by the Department. The Director shall notify the applicant within ten (10) business days of receipt of the application as to whether or not the soil evaluation must be witnessed by the Department.E. Soil Evaluation Witnessed by the Department1. At the time of the notification in § 6.16(D) of this Part, an appointment will be scheduled for the Department to witness the soil evaluation. This appointment shall be within fifteen (15) business days of the Director's notification in § 6.16(D) of this Part.2. Requests for cancellation of the soil evaluation appointment will be accepted by the Director a minimum of twenty-four (24) hours in advance of the scheduled appointment, and if requested, will be rescheduled for the next available date. All other cancellations, including instances where the Director is onsite and the Licensed Designer or Soil Evaluator is not present, will require reapplication to the Director. If the Director is not onsite for the scheduled appointment, the completed soil evaluation shall be submitted to the Director prior to the submission of the application for an OWTS permit.3. The Soil Evaluator shall complete the soil evaluation form prior to the arrival of the Director onsite for the scheduled appointment with the Department. While in the field, the Director shall determine which of the following apply:a. The Director concurs with the determination of the soil evaluation. The soil evaluation form shall be submitted to the Department within ninety (90) days of the scheduled appointment and may be submitted concurrently with the OWTS Application;
b. The Director and the Soil Evaluator concur that results of the seasonal high groundwater table determination are inconclusive, and a determination will have to be made during the wet season in accordance with § 6.16(M)(4) of this Part; orc. The Director does not concur with the soil evaluation. If soil conditions are in dispute, the Department, upon request of the Soil Evaluator, shall provide an additional field review in an effort to resolve the dispute. (1) If the determination of the seasonal high groundwater table remains in dispute after the additional field review and all other elements of the soil evaluation are agreed upon, the Soil Evaluator has the option to conduct a wet season determination of the seasonal high groundwater table in accordance with § 6.16(M)(4) of this Part.(2) If elements of the soil evaluation other than the seasonal high groundwater table remain in dispute after the additional field review, the Department shall disclaim the determinations of the soil evaluation and provide an explanation for not accepting it.F. Soil Evaluation Not Witnessed by the Department - If the Director determines that the Department need not witness the soil evaluation, the Licensed Designer or Soil Evaluator shall notify the Department during normal business hours by telephone of the date and time of the soil evaluation at least twenty-four (24) hours prior to conducting the soil evaluation. The Department, at its discretion, may make unannounced inspections of any soil evaluation. The soil evaluation form shall be submitted to the Director prior to the submission of the application for an OWTS permit and within ninety (90) days of the day the soil evaluation was conducted. 1. If bedrock is encountered within a test hole during a soil evaluation not witnessed by the Department, the Licensed Designer shall apply to the Department for bedrock testing.2. After review of the soil evaluation, the Director shall either:a. Accept the determination of the soil evaluation;b. Determine that the soil evaluation is not in compliance with these Rules or that more information must be collected, in which case a revised soil evaluation must be submitted to the Director; orc. Disclaim the determinations of the soil evaluation, and provide an explanation for not accepting it.G. Soil Evaluation Certification - Individuals conducting a soil evaluation shall certify that the soil evaluation was conducted in a manner consistent with these Rules and that it is an accurate portrayal of site conditions on the day and time it was conducted. If more than one (1) individual licensed under these Rules participated in the development of the soil evaluation it must be specified who prepared which part and include a certification from each licensee.H. Department Acceptance - Acceptance of a soil evaluation indicates only that the Department accepts the data for design of an OWTS, however, the Department reserves the right to question the data. This acceptance is not an indication of the correctness or quality of the soil evaluation.I. Test Hole Requirements1. A minimum of two (2) test holes within twenty-five feet (25') of the proposed leachfield, shall be excavated at least twenty-five feet (25') apart with one (1) pit on the up-gradient side and one (1) on the down-gradient side of the proposed leachfield. The Director may waive the requirement for a second (2nd) test hole where the conditions indicate that such test hole is not necessary.2. The test holes shall be excavated to a depth of five feet (5'), unless site conditions prevent doing so (e.g., a flooded pit due to a high water table) in order to allow detailed examination by the Soil Evaluator. The Soil Evaluator shall complete the soil evaluation form provided by the Director using the terminology in the DEM Soil Evaluation Guidance Document (this document can be found at: http://www.dem.ri.gov/programs/benviron/water/permits/isds/pdfs/seg0108.pdf).3. From the depth excavated for § 6.16(I)(2) of this Part to a minimum of ten feet (10'), to the extent possible, the Soil Evaluator shall provide the information requested on the soil evaluation form from material removed from the test hole without entering the test hole. This information shall include, at minimum, the soil texture, structure and consistence for each soil horizon observed. This can be done in an additional test hole, or in the test hole used to complete work for § 6.16(I)(2) of this Part after such work has been witnessed by the Department, if required.4. If a restrictive layer or bedrock is encountered or the test hole becomes unstable due to lack of soil cohesion or the presence of groundwater, the test hole may be terminated at a depth of less than ten feet (10'). Sites with test holes which have been terminated at less than ten feet (10') may require additional testing as determined by the Director.5. It is recommended that individuals performing the soil evaluation not enter into portions of a test hole that have been excavated to depths greater than five feet (5') below the surrounding ground surface. It is the responsibility of individuals performing or witnessing the soil evaluation to comply with all applicable Federal, State and local laws and Regulations governing occupational safety.J. Soil Class - The information collected from the test hole shall be used to assign the soil to one (1) of the soil classes below, except for Class G soils in which case the soil class for the substratum shall also be indicated. 1. Class A - Glacial Lodgement Till: Silt loam to loamy sand texture. Lower profiles tend to have a platy structure and are dense to very dense. Excavation is difficult. High probability of hydraulically restrictive lower layers. Angular rock fragments and occasional cobbles and stones.2. Class B - Glacial Ablation Till: Silt loam to loamy sand throughout the profile. Lower horizons tend to be more sandy. These soils tend to be looser than lodgement tills and typically do not have hydraulically restrictive layers. Lower horizons may be firm. Angular rock fragments and occasional cobbles and stones.3. Class C - Proglacial Outwash: Also referred to as stratified drift, soil textures range from silt loam to loamy sand (in the upper horizons) to a sandy/gravely substratum. Stratified layers of water sorted materials may be present. Entire profile tends to be loose and easy to dig except saturated horizons may be firm or cemented or both. Horizons of rounded rock fragments are common.4. Class D - Glacial Ice Contact Deposit: Outwash deposits of well to poorly sorted sands and gravel. Texture can be highly variable over short distances and may include pockets or lenses of silt or silt loam. Stratification may be irregular or absent. Sub-rounded to rounded stones and cobbles are possible.5. Class E - Coastal Dune: Fine to coarse sands, well sorted, often finely stratified. Little or no silt and clay. Typically no sediment larger than coarse sand. Deposited by wind action or storm overwash.6. Class F - Alluvial Deposits: Material transported and deposited by streams and rivers. Typically well sorted, stratified, fine textured sediment that may have dark layers in the substratum which were at one time surface layers. Subject to seasonal flooding.7. Class G - Eolian Deposits: Wind blown silts deposited after the retreat of the Wisconsin glaciation ranging in thickness of several inches to several feet. Underlain by outwash, ablation till, or lodgement till.K. Soil Category - Each observed soil horizon shall be assigned to one (1) of the soil categories from § 6.16(L) of this Part below. Soil category will be used to determine the minimum leaching area by the Class II or III Licensed Designer in accordance with § 6.33 of this Part.L. Soil Category Soil Category | Loading Rate (gals/sq ft/day) Pursuant to § 6.33(B) of this Part Starred items (*) are for soils with coarse fragment modifiers | Soil Texture | Soil Structure | Soil Consistence | Typical Soil Class |
Consistence In-Hand Using Soil Clods | Excavation Difficulty |
1 | .70 | cos, s, lcos, ls, cosl, fs | structureless - single grain subangular blocky | loose friable | N/A | Outwash (Class C), ice contact (Class D) and coarse ablation till (Class B) deposits |
.61* |
2 | .61 | vfs, lvfs | structureless - single grain | Loose | N/A | Outwash (Class C) and ice contact (Class D) deposits |
3 | .70 | ls, sl, l | granular, subangular blocky | very friable to friable | low | Lodgement Till (Class A), Ablation Till (Class B), Outwash (Class C), or Ice Contact (Class D) |
4 | .61 | lfs, lvfs, fsl, vfs | granular, subangular blocky | very friable to friable | low | Lodgement Till (Class A), Ablation Till (Class B), Outwash (Class C), or Ice Contact (Class D) |
.70* |
5 | .52 | sil, si, vfsl | subangular blocky | very friable to friable | low | Typically Eolian deposits (Class G) |
6 | .61 | lcos, cosl, lfs, ls, sl, l | structureless massive | very friable to friable | low | Ablation till (Class B) |
.70* |
7 | .52 | fsl, vfsl, sil, si, vfs | structureless - massive | very friable to friable | low to moderate | Ablation till (Class B) |
.61* |
8 | .46 | all textures | structureless -massive | firm to very firm | moderate | Lodgement till (Class A) |
.48* |
9 | .40 | all textures | platy, structureless - massive | firm to very firm | high | Lodgement till (Class A) |
.43* |
10 | Not Allowed (Impervious) | all textures | platy, structureless - massive | extremely firm | very high to extremely high | Lodgement till (Class A) |
M. Determination of Seasonal High Groundwater Table 1. The Soil Evaluator shall use the depth to, type, location and abundance of hydromorphic features and other characteristics to determine the depth to the seasonal high groundwater table. The depth to the seasonal high groundwater table shall be measured from the original ground surface. The criteria to use in evaluating hydromorphic features include, but are not limited to, the following:a. Redox depletions and redox concentrations occupy two percent (2%) or more of the exposed horizon surface;b. Soil matrix and redox concentrations or depletions vary two (2) or more units in chroma; or c. Presence of a depleted horizon, which is a soil layer that has a chroma of two (2) or less and a value of four (4) or more that develops or maintains gleyed colors because of substantial saturation.2. In cases where the soil is Class C or D as determined in § 6.16(J) of this Part and there are no observable hydromorphic features to use to make a determination in accordance with § 6.16(M)(1) of this Part, an adjustment factor may be applied to the observed groundwater table in order to correct to the seasonal high groundwater table. This adjustment factor shall be determined by the Director. When groundwater is not encountered in a test hole at least ten feet (10') deep, the adjustment factor may be applied as measured from the bottom of the test hole.3. A perforated pipe at least four inches (4") in diameter shall be installed to the full depth of the excavation in each test hole at the conclusion of the soil evaluation, unless such requirement is waived by the Director. The pipe shall be wrapped in filter fabric that meets the requirements of § 6.33(L) of this Part, capped at the top and mounded to prevent the accumulation of surface water.4. Wet Season Determinations - Determination of the seasonal high groundwater table during the wet season shall be made by a Class II or III Licensed Designer, or a Soil Evaluator January 1 through April 1.a. The groundwater table observations shall be made using the pipe placed in the test holes in accordance with § 6.16(M)(3) of this Part or using a pipe that meets these requirements placed in a minimum of two (2) excavations to a depth of ten feet (10') within the area in § 6.16(I)(1) of this Part. Such pipe should remain in place until a permit has been issued by the Director.b. Groundwater table observations shall be made no sooner than forty-eight (48) hours after excavation and shall be verified by the Director unless otherwise waived. At least three (3) groundwater table observations shall be made and the observations shall be a minimum of five (5) days apart. The groundwater table observations shall be submitted for review by April 1 on forms approved by the Director.c. Wet season determinations are intended to measure the groundwater table at its annual highest level. Yearly fluctuations in the groundwater table may necessitate that the Department add adjustment factors to compensate for periods of low groundwater recharge that results in the seasonal high groundwater table to be lower than normal.5. The soil evaluation that is submitted to the Director by the Soil Evaluator shall include wet season data, if applicable, along with the final determination of the seasonal high groundwater table.250 R.I. Code R. 250-RICR-150-10-6.16
Amended effective 11/25/2018
Amended effective 12/28/2021
Amended effective 7/1/2022