RECONNAISSANCE SOIL & SITE EVALUATION

Transcription

1 RECONNAISSANCE SOIL & SITE EVALUATION Porter-Bradford Tracts Orange County, NC Three Oaks Job # Prepared For: Beth Porter Tommie Bradford Prepared By: 324 Blackwell Street, Suite 1200 Durham, NC Tel (919) August 17, 2017 John C. Roberts

2 INTRODUCTION & SITE DESCRIPTION A Reconnaissance Soil & Site Evaluation was performed on two tracts located off US HWY 70, Orange County, NC (PINs: and ). Three Oaks Engineering (Three Oaks) was retained to identify areas suitable for placement of on-site wastewater systems for single-family residences. The property was evaluated in accordance with Orange County and North Carolina statutes for waste disposal ( Orange County Regulations for Wastewater Treatment and Disposal Systems, effective February 26, 2015 and Laws and Rules for Sewage Treatment and Disposal Systems, amended July 1, 2016). There is an existing house located in the middle of the larger tract. The septic tank was located in the front yard and a well in the rear. Two streams features were located in the southern area of the properties. The tract is mature forest with very little understory. Property boundaries and corners were not visibly marked on the day of the investigation. INVESTIGATION METHODOLOGY The field survey was conducted on August 8, 2017 by John Roberts, LSS and Evan Morgan, LSS-IT. Soil borings were advanced with a hand-auger and soil color was determined using a Munsell Soil Color Chart. Observations of the landscape (slope, drainage patterns, etc.) and soil properties (depth, texture, structure, soil wetness, restrictive horizons, etc.) were recorded. Soil borings were flagged at the site with blue flagging and located with a handheld GPS unit. FINDINGS Thirty-four (34) soil borings were advanced and their locations noted on Figure 1. Detailed soil boring descriptions are attached. Soil borings rated as Provisionally Suitable for Conventional Systems typically exhibited a friable, silt loam or silty clay loam textured surface horizon with weak, medium, subangular blocky structure ranging in depth from 2 to 12 inches. Upper subsurface (argillic) horizons exhibited a friable or firm silty clay loam, clay loam, or clay texture with moderate, medium, subangular blocky structure ranging in depth from 5 to 36 inches. Lower subsurface horizons exhibited firm, clay loam, or clay textures with weak or moderate, medium, subangular blocky structure ranging in depth from 30 to greater than 36 inches. The recommended longterm acceptance rate (LTAR) for these borings is 0.3 gallons per day/sq-ft. Soil borings rated as Provisionally Suitable for Modified/Alternative Systems typically exhibited a friable, silt loam textured surface horizon with weak, medium, subangular blocky structure ranging in depth from 4 to 8 inches. Upper subsurface (argillic) horizons exhibited a friable or firm silty clay loam, clay loam, or clay texture with moderate, medium, subangular blocky structure ranging in depth from 24 to 29 inches. Lower subsurface horizons were limited by greater than 50% parent material and deemed unsuitable. The recommended LTAR for these borings is 0.25 gallons per day/sq-ft. Porter-Bradford Tracts 1 August 17, 2017

3 Soil borings rated as Unsuitable were due to auger refusal occurring within 24 inches of the surface. Soil in these areas could possibly be reclassified as Provisionally Suitable for Modified or Conventional Systems but would need to be further investigated with a backhoe. Several drainageways deemed unsuitable were located toward the north and east of the tracts. DISCUSSION The tracts were dominated by soil rated as Provisionally Suitable for Conventional and/or Modified/Alternative Systems (Figure 1). The recommended long-term acceptance rate (LTAR) for these soils ranges from 0.25 to 0.3 gal/day/sq-ft. It is anticipated approximately 10,000 to 12,000 sq-ft would be required to support the initial system and repair area system utilizing conventional gravel drainline for a four-bedroom house. The initial system for a four-bedroom house would require 640 feet (0.25 LTAR) or 533 feet (0.3 LTAR) of gravel drainline. A 25% reduction in the drainline length can be achieved by utilizing Accepted Systems drainline. This length can be reduced to 480 feet (0.25 LTAR) and 400 feet (0.3 LTAR) of drainline of Accepted Systems drainline. Borings rated as Provisionally Suitable for Modified/Alternative Systems were so rated due to greater than 50% parent material occurring between 24 and 29 inches below the existing surface. Septic systems sited in these soils will require an additional soil capping placed over the entire drainfield to maintain a minimum of six inches. In order to subdivide the tract with the existing house, regulations require 100% repair area has to be allocated for the existing septic system. It appears adequate area and suitable soil exists in the vicinity of borings J4 and J5 in the front of the house to allocate as repair for the existing house and system. The existing system will need to be located via push probes or soil augers. A 100-ft setback will have to be maintained from the well located in the rear of the existing house to new septic systems on proposed lots. There are two stream features noted in the southern portion of the tracts. These features are likely jurisdictional streams and may include adjacent wetland areas that will need to be delineated if the tracts are to be developed. The tracts are located in the Lower Eno Protected watershed and will require a 100-foot buffer from these surface waters. CONCLUSIONS The findings presented herein represent Three Oaks professional opinion based on our Reconnaissance Soil and Site Evaluation and knowledge of the current laws and rules governing on-site wastewater systems in Orange County and North Carolina. Soil areas rated as Provisionally Suitable for Conventional and/or Modified Systems were identified throughout the tract. Based on the soil and site characteristics, lots will require at least 10,000 sq-ft to 12,000 sq-ft of usable soil to be completely available for septic system installation. It appears adequate area exists in the front of the existing house to allocate as 100% repair area for the initial system. The existing system will need to be located to show the extent of the system and verify it will not be included into any new lot. An additional soil evaluation is recommended once a subdivision site plan has been created. A jurisdictional Porter-Bradford Tracts 2 August 17, 2017

4 delineation of existing surface water (streams and wetlands) will be required to ensure compliance with both state and federal regulations. Soils naturally change across a landscape and contain many inclusions. As such, attempts to quantify them are not always precise and exact. Due to this inherent variability of soils and the subjectivity when determining limiting factors, there is no guarantee that a regulating authority will agree with the findings of this report. An Improvement Permit for each new residence and repair area for the existing residence would be issued by Orange County Environmental Health. Porter-Bradford Tracts 3 August 17, 2017

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