Stormwater Atlas

applicability

Applicability and Relationship to Permits and Local Codes

When criteria apply (new development, redevelopment, thresholds) and how state/local manuals interact.

ReviewedPrevalence 39%~116 manuals tagged14 citationsModel: heuristic+editorialRegional: ms4_vs_non_ms4
Provisional practice synthesis for discussion — not a design manual or adopted regulation. Controlling state, regional, and MS4 criteria apply when more stringent. Verify citations against the linked jurisdiction manuals.

Practice

Manuals typically define when criteria apply to new development versus redevelopment, often with disturbed-area or impervious-cover thresholds tied to MS4 permits. About two-fifths of atlas corpora are tagged for applicability-style topics. Local codes frequently allow stricter thresholds than state minimums; exemptions (for example routine maintenance) appear widely but vary in scope.

Applicability checklist

Draft national guidance grounded in atlas practice — not a design manual or adopted regulation.

TopicSuggested national guidanceAtlas note
New developmentState disturbed-area or impervious thresholds that trigger post-construction criteriaApplicability framing common in purpose/scope chapters
RedevelopmentDefine partial-site or reduced WQv rules for redevelopment; prefer net reduction where feasibleRedevelopment rules vary widely by MS4
ExemptionsList exemptions narrowly (e.g. routine maintenance) so they do not undermine WQ goalsExemption lists appear widely but differ in scope
Stricter local codesAllow agencies to adopt stricter thresholds than this guidanceLocal codes frequently exceed state minimums

Guidance

State when criteria apply to new development and redevelopment, including disturbed-area or impervious thresholds. Clarify how this guidance relates to NPDES MS4 permits, construction general permits, and local codes. Allow agencies to adopt stricter thresholds. List common exemptions carefully so they do not undermine water-quality goals.

Regional notes

MS4 Phase I and Phase II programs often use different triggers. Some arid and cold-climate localities exempt small projects from retention but still require treatment or erosion controls.

Open questions

Choose default national thresholds versus guidance-only ranges. Align the exemption list with typical MS4 permits without undercutting WQ goals.

References

Numbered footnotes for guidance clauses and atlas notes. Field-verified entries come from structured atlas evidence; corpus-pattern entries are keyword-matched excerpts.

  1. [1]WashingtonWashingtonCorpus patternpages 147-147
    “development and redevelopment projects meeting the Project Thresholds in I-3.3 Applicability of the Minimum Requirements shall create an operation and maintenance (O&M) manual for all BMPs used to meet I-3.4.6 MR6: Runoff Treatment, I-3.4.7 MR7: F”
  2. [2]GeorgiaGeorgiaCorpus patternpages 116-116
    “nning through long- term maintenance of stormwater management facilities. 4.2.2 Applicability It is recommended that the stormwater man- agement standards listed below be required for any new development or redevelopment site that meets one or more”
  3. [3]VermontVermontCorpus patternpages 216-216
    “Vermont Stormwater Treatment Standards Section 6.0 Project – New development, expansion, redevelopment and or existing impervious surface that the Secretary is considering for coverage under an individual or general permit or which has”
  4. [4]Rhode IslandRhode IslandCorpus patternpages 46-46
    “he stormwater management requirements for redevelopment will be the same as for new development. The applicant, however, can meet those requirements either on-site or at an approved off-site location within the same watershed provided the applicant satisf”
  5. [5]MinnesotaMinnesotaCorpus patternpages 120-120
    “120 Minnesota storMwater Manual Applicability: Waters of the U.S. Stormwater Relationship: Discharge of dredged or fill material into waters of the U.S. Rivers and Harbors Act, Section 10 Permit Progr”
  6. [6]West VirginiaWest VirginiaCorpus patternpages 10-10
    “nation 4. Controlling Runoff from Construction Sites 5. Controlling Runoff from New Development and Redevelopment (once construction is complete) 6. Pollution Prevention and Good Housekeeping for Municipal Operations This Manual primarily provides guidanc”
  7. [7]MontanaMontanaCorpus patternpages 17-17
    “he project owner and/or design professional are responsible for determining the applicable regulatory requirements and associated permits for each individual project.”
  8. [8]IdahoIdahoCorpus patternpages 31-31
    “thority to obtain the permit application forms, design standards, and any other applicable requirements for the project site area. These requirements could include planning and building codes, flood control and water quality design standards, and s”
  9. [9]City of San DiegoCaliforniaCorpus patternpages 30-30
    “fect is to reduce the quantity of impervious area and fall below thresholds for applicability of stormwater requirements. When defining the project, the following questions must be considered: • What are the project activities? • Do they occur onsi”

Supporting jurisdictions

9 jurisdictions cited in this section (outline tags ~116 manuals; full atlas has ~299).

wa-state-westernga-statevt-stateri-statemn-state-2008west-virginia-manualbillings-mtidaho-bmp-catalogsan-diego-ca