--- title: "Soil drainage class vs hydrologic soil group" description: "Distinguish natural drainage class from hydrologic soil group. Read dual groups and missing values before preparing questions for a foundation inspection." canonical: "https://scalewithsearch.com/articles/soil-drainage-class-hydrologic-group-inspection-context" --- ## Site navigation - [Scale With Search](https://scalewithsearch.com/) - Services - Services - [AI systems](https://scalewithsearch.com/ai-systems) - [Site build](https://scalewithsearch.com/work#site-build) - [Whole website fix](https://scalewithsearch.com/work#whole-website-fix) - [Content library with SEO](https://scalewithsearch.com/work#content-library) - [Working session](https://scalewithsearch.com/audit) - Start here - [Send your brief](https://scalewithsearch.com/work#send-your-brief) - [Example scope](https://scalewithsearch.com/work#review-the-example-scope) - [Prices and terms](https://scalewithsearch.com/work#prices-and-terms) - Industries - Real estate - [Real estate agents and teams](https://scalewithsearch.com/for/real-estate) - [Platforms, ownership, and IDX](https://scalewithsearch.com/for/real-estate/real-estate-website-platforms-ownership-idx) - [Search, content, and AI](https://scalewithsearch.com/for/real-estate/real-estate-search-content-ai) - [Inquiries, campaigns, and handoffs](https://scalewithsearch.com/for/real-estate/real-estate-website-inquiries-campaigns-handoffs) - [Buyer, seller, and local pages](https://scalewithsearch.com/for/real-estate/real-estate-buyer-seller-local-resources) - [Rules, privacy, and trust](https://scalewithsearch.com/for/real-estate/real-estate-website-rules-privacy-trust) - Browse by business - [Trades and home services](https://scalewithsearch.com/for/#group-trades) - [Health, wellness, and animal care](https://scalewithsearch.com/for/#group-practices) - [Law, finance, and IT](https://scalewithsearch.com/for/#group-professional) - [Marketing and SEO agencies](https://scalewithsearch.com/for/#group-agencies) - [Shops and manufacturers](https://scalewithsearch.com/for/#group-manufacturing) - [Restaurants, shops, studios, and nonprofits](https://scalewithsearch.com/for/#group-local-services) - Chiropractic practices - [Chiropractic and wellness practices](https://scalewithsearch.com/for/chiropractic-and-wellness-practices) - [Chiropractic and physical therapy clinics](https://scalewithsearch.com/for/chiropractic-and-physical-therapy-clinics) - [All industries](https://scalewithsearch.com/for/) - Resources - Free tools - [AI readiness check](https://scalewithsearch.com/check) - [Free tools](https://scalewithsearch.com/tools/) - [Free Starter Kit](https://scalewithsearch.com/kit/business-memory-starter-kit.zip) - Guides - [AI-native library](https://scalewithsearch.com/ai-native) - [Industry intelligence](https://scalewithsearch.com/intelligence) - [Office job guides](https://scalewithsearch.com/guides/) - [Business memory](https://scalewithsearch.com/articles/business-memory-for-ai-agents-guide) - [Agent governance](https://scalewithsearch.com/articles/ai-agent-governance-guide-small-business) - [Migration and ownership](https://scalewithsearch.com/articles/leaving-vendor-ai-memory-guide) - Articles - [All articles](https://scalewithsearch.com/articles/) - [What changed](https://scalewithsearch.com/changes/) - About - Evidence - [Proof](https://scalewithsearch.com/proof) - Scale With Search - [About](https://scalewithsearch.com/about) - [How it works](https://scalewithsearch.com/how-it-works) # Drainage class and hydrologic soil group: read two separate soil-survey fields Natural drainage class and hydrologic soil group answer different soil-survey questions. Keep both labels when preparing an inspection handoff. Neither field reports today's conditions beneath a particular building. A coordinator's useful task is to preserve the values, explain their source meanings, and identify unanswered questions. The inspection lead decides how that context relates to the job. This guide uses fictional records to demonstrate that handoff. The [foundation and home repair overview](/for/foundation-and-home-repair) explains the wider office workflow. Here, the scope is narrower: read two attributes without merging them into a drainage verdict. ## Start with the definition of natural drainage class The manual defines natural drainage class through the frequency and duration of wet periods under conditions resembling those in which the soil developed. Human drainage or irrigation changes are excluded unless they have materially changed soil morphology. [Soil Survey Manual, chapter 3, page 213, accessed 2026.10.28](https://www.nrcs.usda.gov/sites/default/files/2022-09/SSM-ch3.pdf#page=131). The manual's descriptions include well drained, moderately well drained, somewhat poorly drained, and poorly drained. These are defined soil terms. They are not instructions for selecting a repair or approving a site. [Chapter 3, pages 214–215, accessed 2026.10.28](https://www.nrcs.usda.gov/sites/default/files/2022-09/SSM-ch3.pdf#page=132). Preserve the complete class name. “Moderately well drained” should not become “well drained” in a shortened note. Likewise, do not replace “somewhat poorly drained” with an informal label such as “bad drainage.” The shortened label loses the source's distinction and adds an unsupported judgment. Ask whether the value belongs to a component or to a summarized map display. Record that level beside the value. If the report does not make the level clear, keep that uncertainty in the handoff. Avoid attaching an observation date to the class unless the source supports it. A report downloaded this morning is still a source report. Its download time is not a measurement of current moisture at the inspection location. ## Read hydrologic soil group as a separate classification Hydrologic soil groups describe estimated runoff potential under stated conditions. The manual describes infiltration when soil is thoroughly wet, lacks vegetation protection, and receives precipitation from long-duration storms. It identifies groups A, B, C, and D. [Soil Survey Manual, appendix 4, page 580, accessed 2026.10.28](https://www.nrcs.usda.gov/sites/default/files/2022-09/SSM-appendix.pdf#page=26). Those reference conditions belong with the definition. Do not translate a group letter into an observed water level or a current inspection finding. Do not turn the classification into a grade for a building's condition. A report can therefore contain two useful values without either replacing the other. Read the drainage class in its own column. Read the hydrologic group in another. Any technical interpretation needs to state which attribute it uses and why. The manual provides a concrete example of that separation. Its Olton map-unit description lists natural drainage class as well drained and hydrologic soil group as C. [Soil Survey Manual, appendix 2, page 562, accessed 2026.10.28](https://www.nrcs.usda.gov/sites/default/files/2022-09/SSM-appendix.pdf#page=8). That example demonstrates that the labels can coexist. It does not establish either value for your property. Use it to challenge a mistaken one-to-one translation between the fields, then return to the actual retained report. ## Keep dual groups intact The manual lists A/D, B/D, and C/D as dual hydrologic soil groups. The first letter represents drained conditions. The second represents undrained conditions. Dual groups apply to soils assigned D in their natural condition. [Soil Survey Manual, appendix 4, pages 580–581, accessed 2026.10.28](https://www.nrcs.usda.gov/sites/default/files/2022-09/SSM-appendix.pdf#page=26). Preserve the slash and both letters. B/D is not an average between B and D. It is not uncertainty about which letter the source intended. The two letters retain the definition's conditional distinction. Do not select B because someone mentions an installed drain. That mention does not establish the conditions needed for a technical use of the classification. Ask the responsible specialist what evidence supports the condition they intend to use. Also avoid choosing D solely because the office lacks a maintenance record. Missing documentation is an unresolved question. It does not prove the property's drainage condition. A coordinator should preserve B/D until a qualified interpretation supplies a documented basis for further use. Keep a homeowner's statement, an installation record, and a specialist's conclusion in separate entries. Each may contribute evidence. None should silently change the value returned by the survey source. ## Compare a fictional record with known and missing fields Every value in the following table is invented. Cedar and Elm are fictional component labels. These combinations illustrate reading decisions and do not describe a real survey unit. | Fictional component | Natural drainage class | Hydrologic soil group | Site evidence in this exercise | | --- | --- | --- | --- | | Cedar loam | Well drained | C | No current observation supplied | | Elm loam | Poorly drained | B/D | Homeowner mentions a drain; no supporting record supplied | | Urban land | Not supplied | Not supplied | No soil investigation supplied | Begin with Cedar. The record gives two survey values and no current site observation. Copy both values. Record the absent observation separately. Do not describe Cedar's row as contradictory because its hydrologic group is C. For Elm, retain the full B/D value. Put the homeowner's statement in a reported-information column. Ask what record or investigation the technical lead requires before using a drained-condition assumption. Do not rewrite the source group in response to the statement. For Urban land, preserve both missing fields. Neither of the neighboring rows provides a substitute value. Record that the retained example supplies no attribute, then ask whether the full source description explains the omission. The [SSURGO component guide](/articles/ssurgo-map-unit-components-foundation-inspection-questions) explains why each row also needs its map-unit context. A table of component attributes does not locate those components beneath a selected wall or footing. ## Separate the meaning of a blank from the reason for it Use “not supplied in this report” when that is all the evidence establishes. If an official description says a field is not applicable, preserve that wording and reference. Without that explanation, leave the reason unknown. Distinguish three preparation problems. A field may be blank in the retained source. A copied excerpt may omit the field. Or the preparer may not yet have requested the relevant report. Each problem requires a different next step. For a source blank, ask whether the publisher provides an explanation. For an incomplete excerpt, obtain the complete report. For a missing report, record that no value has yet been retrieved. Do not collapse these states into a favorable or unfavorable rating. This distinction matters in the fictional Urban land row. The coordinator can complete the source note while keeping the attribute unresolved. The inspection lead can then decide what additional information the job requires. A filled spreadsheet cell is not the objective. ## Check the report's level and settings Web Soil Survey can summarize component attributes for a map display. The manual describes methods such as dominant component and dominant condition. It also documents settings that can exclude components below a percentage cutoff. [Soil Survey Manual, appendix 4, table A-4, pages 576–577, accessed 2026.10.28](https://www.nrcs.usda.gov/sites/default/files/2022-09/SSM-appendix.pdf#page=22). If a map shows one color and a component table lists several values, inspect the report description. Ask whether a summary method produced the map label. Retain the method and any stated cutoff with the output rather than treating the color as every component's value. Do not assume which method an unfamiliar export used. Ask for its description or settings. If they cannot be recovered, mark the displayed summary as insufficiently documented for the intended comparison. For the fictional table, there is no calculated map summary. It shows the rows directly. If someone creates a one-line office summary, require that person to state what was included and omitted. Keep the complete table attached so the inspection lead can review the choices. ## Prepare a handoff with three evidence sections Use three sections: survey attributes, site information, and questions for professional review. This structure prevents a copied source label from becoming an apparent field finding. In the survey section, record the survey area, map-unit reference, component, attribute names, and exact values. Add the report edition when supplied. Record the retrieval date separately. Include the report description when it explains a summary method or missing field. In the site section, retain observations only as documented. Name the observer, date, location, and source record. Keep reported statements visibly attributed. If the exercise supplies no observation, say so. In the review section, name the question and responsible reviewer. For fictional Elm, ask what evidence would support any use of the drained condition. For Cedar, ask which site information remains necessary for the inspection. For Urban land, ask how the missing survey attributes affect preparation. An example handoff could read: “Elm's survey record lists poorly drained and B/D. A homeowner mentions a drain. Its presence, condition, and relevance remain unverified. The technical lead must identify the evidence needed before selecting a condition for further interpretation.” That note preserves the source values and the reported statement. It also identifies the next decision without supplying the answer. The responsible reviewer can close the question with a dated reference after reviewing appropriate evidence. ## Compare two reports without confusing their levels Suppose a colleague supplies a second fictional report labeled “group C.” The original table includes Cedar at C, Elm at B/D, and an unknown Urban land value. Before calling the reports inconsistent, ask what each report describes. The second report might be a component entry, a map summary, or an incomplete excerpt. Its label alone does not resolve that question. Ask for the map-unit identifier, component reference, report description, and edition. Keep the second result separate until its meaning is documented. If both reports describe the same component under the same conditions, ask the source preparer to explain the difference. If they summarize different selections, retain those selections beside the values. Neither case justifies selecting whichever result looks more favorable. Write the comparison outcome as a record question: “These reports have not yet been matched by component and method.” Assign someone to recover the missing references. That gives the inspection lead a clear unresolved task without inventing a change in the soil. ## Review the wording before the inspection Read the handoff as if you had never seen the source. Can you distinguish a survey attribute from an observation? Can you identify which condition a dual group describes? Can you find every missing field without opening a separate email? Remove wording that exceeds the evidence. “The survey lists group C” describes a source. “The foundation has a drainage defect” asserts a technical conclusion. The second statement cannot come from the first field alone. Neither survey field diagnoses seepage or foundation movement. Neither establishes fill, bearing capacity, drainage design, or repair scope. Keep those conclusions with the responsible specialists and their supporting site evidence. For wider context, read [public signals for foundation and home repair](/intelligence/foundation-and-home-repair). For retaining source versions and corrections, use the [business memory guide](/articles/business-memory-for-ai-agents-guide). Keep the final accepted interpretation attached to the evidence that supports it. This guide uses USDA Handbook 18, issued March 2017. The [manual hub](https://www.nrcs.usda.gov/resources/guides-and-instructions/soil-survey-manual) identifies that edition and its chapter downloads. Its [January 2019 errata](https://www.nrcs.usda.gov/sites/default/files/2022-09/SSM-Errata-2019.pdf) corrects a separate free-water table on page 215. Both were checked on 2026.10.28. No values from that table are used here. Scale With Search can discuss organizing approved source reports and inspection questions into a repeatable handoff. Bring the current example and the person responsible for checking it. [Discuss the scope](/work) Continue the website review: [AI-native foundation and home repair: first functions](/articles/ai-native-foundation-home-repair-first-functions); [Foundation Contractor Review Replies: Keep Facts Private](/articles/foundation-contractor-negative-review-replies); [Foundation, Crawl Space, and Drainage Service Pages](/articles/foundation-crawl-space-drainage-service-pages); [Foundation and home repair AI rules: data, approvals, spend](/articles/foundation-home-repair-ai-rules-data-approvals-spend); [Foundation Reports on Google: Check PDF Access First](/articles/foundation-inspection-report-pdf-search-privacy); [Foundation Inspection Requests: Plan the Website Page](/articles/foundation-inspection-request-website-page); [Foundation Inspection Videos: Plan Captions and Text](/articles/foundation-inspection-video-website-captions); [Foundation Repair AI Answers: Publish Checked Facts](/articles/foundation-repair-ai-answer-business-facts); [Foundation Repair Financing Pages: Review the Terms](/articles/foundation-repair-financing-website-copy); [Free Foundation Inspection: Check Your Website Offer](/articles/foundation-repair-free-inspection-website-copy); [Foundation Repair Case Studies: Show the Recorded Work](/articles/foundation-repair-project-case-study-page); [Foundation Repair Service Area Pages That Earn a Place](/articles/foundation-repair-service-area-pages); [Foundation Repair Warranty Pages: Publish Exact Terms](/articles/foundation-repair-warranty-website-page); [Soil map-unit components: prepare foundation inspection questions from SSURGO](/articles/ssurgo-map-unit-components-foundation-inspection-questions). [foundation and home repair contractors](/for/foundation-and-home-repair): website and search resources. ## Related: foundation and home repair contractors - [Soil map-unit components: prepare foundation inspection questions from SSURGO](/articles/ssurgo-map-unit-components-foundation-inspection-questions) - [AI-native foundation and home repair: first functions](/articles/ai-native-foundation-home-repair-first-functions) - [Foundation Contractor Review Replies: Keep Facts Private](/articles/foundation-contractor-negative-review-replies) ---- ```text .|########||. .|########||. .|########||. |##||. .||##|. |##||. .||##|. |##||. .||##|. |#|. .|#|. |#|. .|#|. |#|. .|#|. |#| |#| |#| |#| |#| |#| .#| |#. .#| |#. .#| |#. .#. .#| .#. .#| .#. .#| |#. .#| |#. .#| |#. .#| |# ...... #| |# ...... #| |# ...... #| .# ||#########| #| .# ||#########| #| .# ||#########| #| .#. |######||######|. .#. .#. |######||######|. .#. .#. |######||######|. .#. #. .##|###|##|#|######| .# #. .##|###|##|#|######| .# #. .##|###|##|#|######| .# || |##|#||||||||||||#||#| || || |##|#||||||||||||#||#| || || |##|#||||||||||||#||#| || # |#||||||||||||||||||||#| #. # |#||||||||||||||||||||#| #. # |#||||||||||||||||||||#| #. || |#||||||||||||||||||||||#| || || |#||||||||||||||||||||||#| || || |#||||||||||||||||||||||#| || # .#||||||||||||||||||||||||#| # # .#||||||||||||||||||||||||#| # # .#||||||||||||||||||||||||#| # || ....|||#||||||##|#|||#|#||##||||....|. || || ....|||#||||||##|#|||#|#||##||||....|. || || ....|||#||||||##|#|||#|#||##||||....|. || #. . ....|# ....#||| ||| .#||| ....#. .# #. . ....|# ....#||| ||| .#||| ....#. .# #. . ....|# ....#||| ||| .#||| ....#. .# # . ||||#| .#####|| . .#| .#||| ||||# #. # . ||||#| .#####|| . .#| .#||| ||||# #. # . ||||#| .#####|| . .#| .#||| ||||# #. .| ||||| #. |#|||||. || #. |#||. .||||| || .| ||||| #. |#|||||. || #. |#||. .||||| || .| ||||| #. |#|||||. || #. |#||. .||||| || || |.... #. ....|#. |. ...|. ....|| || || |.... #. ....|#. |. ...|. ....|| || || |.... #. ....|#. |. ...|. ....|| || #. .||||||##||||||##||####|||||||#||||||#| .# #. .||||||##||||||##||####|||||||#||||||#| .# #. .||||||##||||||##||####|||||||#||||||#| .# # .||####|###########################|. # # .||####|###########################|. # # .||####|###########################|. # # .#||||||.#.|| # |. ..# #| #|||||#| # # .#||||||.#.|| # |. ..# #| #|||||#| # # .#||||||.#.|| # |. ..# #| #|||||#| # # .#|||||| .. |# ## |#| ...#|#|||#| # # .#|||||| .. |# ## |#| ...#|#|||#| # # .#|||||| .. |# ## |#| ...#|#|||#| # # .#|||#|# .# .#| #| ##|.#..#|||||#| # # .#|||#|# .# .#| #| ##|.#..#|||||#| # # .#|||#|# .# .#| #| ##|.#..#|||||#| # # .#||||||############|######|||||#| # # .#||||||############|######|||||#| # # .#||||||############|######|||||#| # # |...||#||||||#||||#|#||||||#|||||#||| |.| # # |...||#||||||#||||#|#||||||#|||||#||| |.| # # |...||#||||||#||||#|#||||||#|||||#||| |.| # #. .. ||||# .|||##|. |#| .|| || .|||#. #| # .# #. .. ||||# .|||##|. |#| .|| || .|||#. #| # .# #. .. ||||# .|||##|. |#| .|| || .|||#. #| # .# || | ...|| ...##| | #| .|. |. ##### .. .| || || | ...|| ...##| | #| .|. |. ##### .. .| || || | ...|| ...##| | #| .|. |. ##### .. .| || || ||||| || ||||#| . |. |. |#. ||||| |#| || || || ||||| || ||||#| . |. |. |#. ||||| |#| || || || ||||| || ||||#| . |. |. |#. ||||| |#| || || .# |.....#|....|#.||||.|||##.|#|....||.#||.#. #. .# |.....#|....|#.||||.|||##.|#|....||.#||.#. #. .# |.....#|....|#.||||.|||##.|#|....||.#||.#. #. #.|||||||#############################| ||| .# #.|||||||#############################| ||| .# #.|||||||#############################| ||| .# || ##||#||#||||||#||#||#||#||##. || || ##||#||#||||||#||#||#||#||##. || || ##||#||#||||||#||#||#||#||##. || # .#|||||||||#||#|||||||||||#| # # .#|||||||||#||#|||||||||||#| # # .#|||||||||#||#|||||||||||#| # || |#||||||||||||||||||||||#| || || |#||||||||||||||||||||||#| || || |#||||||||||||||||||||||#| || .# |#||||||||||||||||||||#| #. .# |#||||||||||||||||||||#| #. .# |#||||||||||||||||||||#| #. || |#||||||||||||||||||#| || || |#||||||||||||||||||#| || || |#||||||||||||||||||#| || #. .######|#|#########| .# #. .######|#|#########| .# #. .######|#|#########| .# .#. |#####||||#####| .#. .#. |#####||||#####| .#. .#. |#####||||#####| .#. |# ||########|| #. |# ||########|| #. |# ||########|| #. |# ...... #| |# ...... #| |# ...... #| |#. .#| |#. .#| |#. .#| |#. .#. |#. .#. |#. .#. .#| |#. .#| |#. .#| |#. |#| |#| |#| |#| |#| |#| .|#|. .|#|. .|#|. .|#|. .|#|. .|#|. |##||. .||##| |##||. .||##| |##||. .||##| .||########||. .||########||. .||########||. 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