A. Soil Investigation. Determination of soil characteristics on sites proposed for development with private sewage disposal systems shall be based on soil boring data collected by a soil classifier. Each property owner or applicant shall contract with a soil classifier, to identify soil characteristics and classifications for the purpose of reporting soil suitability potential for soil absorption systems. The Department shall utilize NRCS for periodic quality control sessions with all classifiers available for the performance of on-site soil evaluations, and for needed soils expertise to the Department in connection with the needs of this Ordinance.
B. Boring Criteria. There shall be a minimum of three (3) suitable borings per soil absorption system site. More soil borings may be necessary for accurate and appropriate evaluation of a site where there is some concern about the consistency of the soil materials. One of the borings shall be made at the lowest portion of the proposed absorption field area. Such borings shall extend at least five (5) feet below the natural ground surface or greater if needed, based on the proposed system design. The proposed subsurface seepage system shall be located within the area of the soil borings. Soil borings shall be valid for one year after the test date, after which time an update is required by the soil classifier.
C. Soil Pits. Observation and determination of soil characteristics may also be determined from a pit dug by a backhoe or other excavating equipment. Soil pits (backhoe excavation) shall be required in cases where ground is frozen, where the soil materials are considerably varied in texture, where there has been filling or proposed cutting of soils, or where trenches are proposed deeper than normally considered, etc. Such soil pits shall be prepared at the perimeter of the expected soil absorption area to minimize damage to natural soil distribution network that may be caused by settling after installation of the system. Soil pits shall be at least two (2) feet wide and five (5) feet deep.
D. Site Characteristics. Site characteristics to be described include zones of seasonal and permanent water saturation, depth to bedrock, USDA/NRCS soil texture, USDA/NRCS soil structural features of note, slope, compaction and depth, soil coloration, depth of soil mottling, permeability range, and other limiting soil characteristics that may reduce permeability.
E. County Review. The County reserves the right to review site soil characteristics with assistance from a certified NRCS soil classifier. In the process, the County reserves the right to witness any such tests. If conflicting soils investigation is provided about a given site, a certified NRCS soil classifier will be requested to provide professional information.
F. Site Evaluation. On-site sewage disposal systems may be utilized where lots or parcels are in compliance with the applicable County Ordinances in effect on the date of permit application and all of the criteria for site consideration in Table I (See Appendix B) are satisfied.
G. Minimum Depth to Limiting Layer. In no case shall the depth to any limiting layer be less than 12 inches from the natural soil surface (see next paragraph). Providing this can be met, the separation below the bottom surface of the soil absorption system and the top of any limiting layer (i.e. seasonal groundwater, impermeable strata, bedrock, etc.) shall be as follows:
1. Rapidly Permeable Soils. Soils having rapid to very rapid permeability (> 6.0 in./hr.) shall have at least 4 feet of separation (or as allowed in Table I).
2. Moderately Rapid Soils. Soils having a permeability rate between 2 in./hr. and 6.0 in./hr. shall have at least 3 feet of separation (or as allowed in Table I).
3. Moderate Soils. Soils having a permeability rate slower than 2 in./hr. shall have at least 2 feet of separation (or as allowed in Table I).
4. Creviced Limestone Formations. A subsurface seepage system shall not be constructed in an area where there is less than 4 feet of soil between the lowest point in a subsurface seepage system and the top of a creviced limestone formation. In areas where creviced limestone is known to occur, a soil boring to a depth of at least 4 feet below the bottom of the subsurface seepage system shall be made to verify that creviced limestone is not present.
H. Setbacks. All setbacks and horizontal distances in Table IV shall be satisfied.
I. Surface Water Overflow. The site of the installation shall not be subject to saturation from surface water overflow from natural or artificial drainage of ground surfaces, driveways, roads or roof drains.
J. Flood Hazard Area. The land elevation at the site of the proposed system installation shall not be subject to flooding, (i.e. shall not be within the 100 year flood hazard area as defined by the base flood elevation of the closest stream or body of water). Such elevation shall be provided in USGS/MSL (United States Geological Survey Mean Sea Level) datum.
K. Future Replacement Area – Non Residential Properties. In all cases where non-residential properties are proposed for development, an area for a full-size replacement system shall be provided. The area shall be suitable for septic installation as confirmed by onsite soil investigation and designated for future septic system replacement. This replacement area shall be kept free of development, traffic or soil modification on all properties.
L. Slope Restrictions. Private sewage disposal systems shall not be permitted on slopes exceeding 25 % (reference Table I on slope limitation).
M. Septic Suitability on New Land Parcels. Parcels of less than 10 acres created on or after September 1, 1990 will be required to demonstrate (via on-site soils evaluation procedures) one-half acre of contiguous, non-critical soils within the boundaries of the parcel(s), or designated subsurface seepage and future replacement subsurface seepage areas in compliance with § 8.04.650 Platting of New Subdivisions, before a permit will be issued for installation of a septic system. The septic system must be installed within an area of non-critical soils, or the designated subsurface seepage area. This is to ensure that all new parcels being created are being developed in a manner that is consistent with § 8.04.650. On all lots within a subdivision recorded after the date of February 1, 2003, the 1/2 acre of contiguous, non-critical soils, or the designated subsurface seepage area on each lot shall not be altered or modified until a septic system permit has been issued.
N. Water Table Monitoring Wells. Water table monitoring may be utilized when the property owner feels that the results of the soil test conducted do not accurately reflect present day seasonal water tables. The following requirements will be used when a request is made to use observed water tables in lieu of soil borings. Please Note: Monitoring in itself does not ensure approval to install a soil absorption system. Once monitoring is completed, a request for a variance from the use of soil mottling as an indicator of high groundwater or seasonal saturation must be made in writing to the Public Health Administrator.
1. Installation Approval. Written approval will be given by the Department after all the required data listed below has been received and reviewed. Construction of monitoring wells shall not start until this approval has been received.
2. Soil Boring Logs. Detailed soil boring logs of the area to be monitored are to be submitted with the proposal.
3. Number of Monitoring Wells. No less than two (2) monitoring wells shall be present in the area of the proposed private sewage disposal system. One (1) of the monitoring wells shall be located in the lowest portion of the proposed subsurface seepage area. Monitoring wells shall be present to accurately portray seasonal groundwater conditions.
4. Location and Design. The location and design of the monitoring wells shall be drawn to scale on a plot sheet. The design shall be based upon Illustration 3 (Appendix C.), or other design as approved by the Department.
5. Monitoring Data Format. The monitoring data shall be recorded by a licensed professional engineer or soil classifier.
6. Monitoring Period. The wells will be required to be monitored for a period of one (1) year with precipitation amounts of plus or minus 15% of the average. Rainfall during the Spring season (March 21 to June 21) must be equal to or greater than the normal amount for that period. The precipitation amounts will be taken from the closest reporting weather station.
7. Monitoring Frequency. The observations shall be made within two (2) weeks after the frost is absent and thereafter every seven (7) days until July 1st until the test year is complete, the frequency shall be once a month. However, if there is a heavy rainfall (1/2 inch or more within a 24 hour period) the monitoring well shall be checked within 24 hours.
8. Monthly Precipitation Totals. Precipitation totals are to be recorded daily and reported with monitoring well levels monthly.
9. Site Approval. If no two (2) consecutive observations show the presence of water above the critical depth, the site will be considered acceptable.
(Ord. O-201711-51-031, passed 11-14-2017)