USDA SEPTIC TANK ABSORPTION FIELD RATING: SELECTED NC183 EXAMPLE Pillar team | Retrieved November 10, 2026 (US Pacific) Public source extract and reproducible retrieval notes; no parcel, site evaluation or engineering assessment. SOURCE AND ACTUAL RETRIEVAL Service: https://sdmdataaccess.sc.egov.usda.gov/Tabular/post.rest Method: POST with a JSON body containing query and format. Format: JSON+COLUMNNAME. First response row is the source column header. Started: 2026-11-11T01:27:44.456724+00:00 Retrieved: 2026-11-11T01:27:45.198878+00:00 (The UTC timestamps fall on November 11; the retrieval was made on the evening of November 10, 2026, US Pacific time.) Observed HTTP status: 200 Response: 14 data rows plus one header row. The downloadable CSV preserves the fifteen source column names and their returned text values. CSV: /research/usda-septic-rating-nc183-2026-11-10.csv CSV encoding: UTF-8, LF newlines, header included. No added derived columns. CSV SHA-256: 329da0d3592e09911011d289d166ff97a99df6d5fed2b062436bc5926154ca16 SELECTION AND LIMITS The SQL selects two map units in survey NC183 (Wake County, North Carolina) by map-unit key: 2538475 (CrD) and 2538476 (CrB). They are the same two units used in /research/usda-map-unit-components-2026-10-31.txt, where they were chosen as the first two string-ordered map-unit keys in the survey. They are a teaching selection, not a statistical sample, a parcel, a project area of interest or a finding about any property. The query returns every component interpretation row for those units where the main rule name is 'ENG - Septic Tank Absorption Fields'. No major-component filter or percentage cutoff was applied. Both units returned two components, each marked Yes as major. No geometry, parcel boundary, area calculation, horizon data or onsite test was requested. Component percentages do not locate soil components within a property. HOW TO READ THE ROWS ruledepth 0 is the overall rating for the component: interphr is the rating index and interphrc is the rating class. ruledepth 1 rows are the rating reasons: rulename is the sub-rule, interphr its index from 0 to 1, and interphrc the reason label shown in Web Soil Survey. What the 14 rows show: - CrB, "Creedmoor-Green Level complex, 2 to 6 percent slopes": Creedmoor (60) and Green Level (40) are each rated Very limited (1). Reasons for each: Depth to saturated zone (1) and Slow water movement (1). - CrD, "Creedmoor-Green Level complex, 10 to 15 percent slopes": Creedmoor (60) and Green Level (40) are each rated Very limited (1). Reasons for each: Depth to saturated zone (1), Slow water movement (1) and Slope (0.633). These are mapped soil survey interpretations. They are not a percolation test, a soil evaluation by a permitting authority, or a statement that any lot can or cannot have a septic system. SOURCE VINTAGE Returned saversion: 29. Returned saverest, preserved verbatim: 9/3/2026 1:43:46 PM. The service did not state the timezone in that value. It is the survey-area version date, which is distinct from this retrieval date and from any date of field observation at a building site. Live data may change; compare a later retrieval by the same keys and record its actual version and values rather than silently replacing this snapshot. NRCS DESCRIPTIONS RETRIEVED THE SAME DAY Two description fields were read from the same service on November 10, 2026. Excerpts below are verbatim. 1. Table sdvattribute, attributename = 'Septic Tank Absorption Fields', column attributedescription (the description Web Soil Survey shows with the rating): "Septic tank absorption fields are areas in which effluent from a septic tank is distributed into the soil through subsurface tiles or perforated pipe. Only that part of the soil between depths of 24 and 60 inches is evaluated. The ratings are based on the soil properties that affect absorption of the effluent, construction and maintenance of the system, and public health. Saturated hydraulic conductivity (Ksat), depth to a water table, ponding, depth to bedrock or a cemented pan, and flooding affect absorption of the effluent." "The ratings are both verbal and numerical. Rating class terms indicate the extent to which the soils are limited by all of the soil features that affect the specified use. "Not limited" indicates that the soil has features that are very favorable for the specified use. Good performance and very low maintenance can be expected. "Somewhat limited" indicates that the soil has features that are moderately favorable for the specified use. The limitations can be overcome or minimized by special planning, design, or installation. Fair performance and moderate maintenance can be expected. "Very limited" indicates that the soil has one or more features that are unfavorable for the specified use. The limitations generally cannot be overcome without major soil reclamation, special design, or expensive installation procedures. Poor performance and high maintenance can be expected." "Numerical ratings indicate the severity of individual limitations. The ratings are shown as decimal fractions ranging from 0.01 to 1.00. They indicate gradations between the point at which a soil feature has the greatest negative impact on the use (1.00) and the point at which the soil feature is not a limitation (0.00)." "Other components with different ratings may be present in each map unit." "Onsite investigation may be needed to validate these interpretations and to confirm the identity of the soil on a given site." 2. Table sainterp, areasymbol = 'NC183', interpname = 'ENG - Septic Tank Absorption Fields', column interpdesc: "Soils are placed into interpretive rating classes per their rating indices. These are not limited (rating index = 0), somewhat limited (rating index > 0 and < 1.0), or very limited (rating index = 1.0)." "Septic tank absorption fields are subsurface systems of tile or perforated pipe that distribute effluent from a septic tank into the natural soil. The centerline depth of the tile is assumed to be 24 inches or deeper. Only the soil between depths of 24 and 60 inches is considered in making the ratings." "While some general observations may be made, onsite evaluation is required before the final site is selected." "The rating is for soils in their present condition and does not consider present land use." "Percolation tests are used by some regulatory agencies to evaluate the suitability of a soil for septic tank absorption fields. These tests should be performed during the season when the water table is highest and the soil is at minimum absorptive capacity." Criteria stated in the same field for the three reasons returned above: - Depth to saturated zone: limiting below 120cm, somewhat limiting from 120 to below 180cm, not limiting at 180cm or deeper. "Soil feature considered is the top depth of the first layer where soil moisture layer status is wet or saturated during any month." - Restricted permeability (shown as Slow water movement): limiting below 10.0 micrometers/sec, somewhat limiting from 10.0 to 40.0, not limiting above 40.0, for the layer deeper than 60 cm with the minimum saturated hydraulic conductivity. - Slope: limiting above 15%, somewhat limiting from 8 to 15%, not limiting below 8%. HOW TO CHECK THE EXAMPLE 1. Open https://websoilsurvey.nrcs.usda.gov/app/ and set an area of interest in Wake County, North Carolina that includes map unit CrB or CrD. 2. Soil Data Explorer > Suitabilities and Limitations for Use > Sanitary Facilities > Septic Tank Absorption Fields. 3. Compare the rating class and rating reasons with the CSV rows, and compare the survey version shown with the saversion and saverest values above. 4. Or resend the SQL below to the public tabular service and compare the rows. PUBLIC PRIMARY DOCUMENTATION https://sdmdataaccess.nrcs.usda.gov/WebServiceHelp.aspx Post.Rest Query Service and JSON+COLUMNNAME format. https://websoilsurvey.nrcs.usda.gov/app/Resources/HomePage/Soil_Explorer_Tab.pdf Lists "Septic Tank Absorption Fields" under Suitabilities and Limitations for Use > Sanitary Facilities. https://websoilsurvey.nrcs.usda.gov/app/MainHelp.htm https://www.nrcs.usda.gov/resources/data-and-reports/soil-survey-geographic-database-ssurgo EXACT SQL SENT TO THE PUBLIC TABULAR SERVICE SELECT sac.saversion, sac.saverest, l.areasymbol, mu.mukey, mu.musym, mu.muname, c.cokey, c.compname, c.comppct_r, c.majcompflag, ci.mrulename, ci.ruledepth, ci.rulename, ci.interphr, ci.interphrc FROM sacatalog AS sac INNER JOIN legend AS l ON l.areasymbol = sac.areasymbol INNER JOIN mapunit AS mu ON mu.lkey = l.lkey INNER JOIN component AS c ON c.mukey = mu.mukey INNER JOIN cointerp AS ci ON ci.cokey = c.cokey WHERE l.areasymbol = 'NC183' AND mu.mukey IN (2538475, 2538476) AND ci.mrulename = 'ENG - Septic Tank Absorption Fields' ORDER BY mu.mukey, c.comppct_r DESC, c.cokey, ci.ruledepth, ci.interphr DESC, ci.rulename; DESCRIPTION QUERIES SELECT TOP 1 attributename, attributedescription FROM sdvattribute WHERE attributename = 'Septic Tank Absorption Fields'; SELECT TOP 1 areasymbol, interpname, interpdesc FROM sainterp WHERE areasymbol = 'NC183' AND interpname = 'ENG - Septic Tank Absorption Fields';