SWPPP Glossary

Plain-language definitions for every term you will encounter in stormwater compliance — from Administrative Continuance to WOTUS.

A

Administrative Continuance: A legal mechanism under 40 CFR Part 122.6 that preserves an expired NPDES permit's terms and conditions in full force when the permit holder submitted a timely renewal application and the permitting authority has not yet issued the new permit. The permit effectively continues until the replacement is issued. Administrative continuance is not a compliance holiday — all inspection, monitoring, and reporting obligations remain active.; See also:CGP MSGP NPDES
ADEQ: Arizona Department of Environmental Quality. The state agency that administers the AZPDES (Arizona Pollutant Discharge Elimination System) program, including the AZPDES Construction General Permit governing construction site stormwater discharges in Arizona.; See also:AZPDES CGP
AZPDES: Arizona Pollutant Discharge Elimination System. Arizona's state-delegated NPDES program, administered by ADEQ. The AZPDES Construction General Permit governs stormwater discharges from construction sites disturbing one acre or more in Arizona. Notable for monsoon season provisions and a post-storm inspection trigger tied to any discharge event rather than a fixed rainfall amount.; See also:ADEQ CGP NPDES

B

Benchmark Monitoring: Under the EPA Multi-Sector General Permit (MSGP), sector-specific chemical or physical parameters that industrial stormwater operators must measure in collected stormwater samples and compare against EPA-established numeric benchmarks. Benchmark exceedances trigger Tier 1 (investigate and implement corrective action) or Tier 2 (develop a NAL Exceedance Response Action Plan) obligations. Benchmark monitoring is not required under the Construction General Permit.; See also:MSGP NAL DMR
Best Management Practice (BMP): Any structural, non-structural, or procedural measure used to prevent, reduce, or control stormwater pollution. BMPs fall into two broad categories: Erosion Control BMPs (prevent soil from detaching — seeding, blankets, construction entrances) and Sediment Control BMPs (capture soil that has detached before it leaves the site — silt fence, sediment basins, inlet protection). The SWPPP must identify and describe every BMP to be implemented, including its location, installation specifications, and maintenance requirements.; See also:Erosion Control Sediment Control SWPPP

C

CGP (Construction General Permit): The EPA permit governing stormwater discharges from construction activity disturbing one acre or more of land. The federal CGP applies in states without EPA-delegated NPDES authority; states with delegation (New Mexico, Arizona, Texas, most others) issue their own equivalent construction general permits. The CGP is temporary — it begins with NOI acceptance and terminates when the operator files a Notice of Termination upon achieving final stabilization.; See also:NPDES NOI NOT SWPPP MSGP
Clean Water Act (CWA): The primary federal law governing water pollution in the United States, enacted in 1972 (33 U.S.C. § 1251 et seq.). Section 402 establishes the NPDES permit program under which the CGP and MSGP are issued. Section 311(j)(1)(C) establishes the SPCC plan requirement. Violation of a CWA permit condition can result in civil penalties up to $64,618 per day per violation and criminal penalties including imprisonment.; See also:NPDES CGP MSGP SPCC
Common Plan of Development: A development concept under which multiple individual construction activities are considered a single project for NPDES permit coverage purposes. If a master plan, approved subdivision plat, or phased development plan will ultimately disturb one or more acres in total, every individual construction activity within that plan requires stormwater permit coverage — even if the individual work area disturbs less than one acre. This provision is the most frequently misapplied threshold rule in construction stormwater compliance.; See also:CGP NPDES NOI
Concrete Washout: The process of cleaning concrete from mixers, trucks, tools, and equipment. Concrete washout water is highly alkaline (pH 11–13) and considered a pollutant under NPDES permit programs. The SWPPP must designate specific concrete washout areas, and washout water must be contained — never discharged to a stormwater conveyance or surface water. New Mexico (NMPDES) explicitly prohibits any discharge of concrete washout water to surface water or stormwater conveyances, which is more stringent than the federal standard.; See also:BMP SWPPP NMPDES

D

Dewatering: The removal of groundwater, stormwater, or process water accumulated in an excavation or construction area. Dewatering discharges to surface water are regulated separately from construction stormwater discharges under most state programs. In New Mexico, construction dewatering that discharges to surface water requires a separate NMPDES permit — it cannot be covered under the construction CGP alone. This is one of the most commonly overlooked permit requirements on excavation-heavy projects.; See also:NMPDES CGP NOI
Disturbed Area: Any area where construction activity has exposed soil or altered the existing ground surface through clearing, grading, excavation, filling, demolition with earthwork, stockpile creation, or utility trenching. The total acreage of disturbed area determines permit coverage requirements and, under New Mexico's proposed tiered system, the applicable compliance tier. Off-site borrow areas used for the project count toward the project's total disturbed acreage.; See also:CGP Common Plan of Development Final Stabilization
DMR (Discharge Monitoring Report): The standard EPA form used to report monitoring results (benchmark monitoring data, stormwater sample results) to the permitting authority. Under the MSGP, all DMRs must be submitted electronically via EPA's NeT-MSGP system. Paper DMR submission is not permitted. DMRs are publicly available in EPA's ECHO (Enforcement and Compliance History Online) database.; See also:MSGP Benchmark Monitoring NeT-MSGP
303(d) List: The list of water bodies that each state must identify under Section 303(d) of the Clean Water Act as failing to meet applicable water quality standards, for which Total Maximum Daily Loads (TMDLs) must be established. Construction sites whose stormwater discharges reach a 303(d)-listed impaired water body face heightened requirements: longer NOI waiting periods (30 days under the federal CGP), enhanced BMP requirements in the SWPPP, and in some states, additional monitoring and reporting obligations.; See also:TMDL CGP NOI ONRW

E

Erosion Control: BMPs designed to prevent soil from detaching in the first place — protecting the soil surface from raindrop impact, overland flow, and wind. Contrast with sediment control, which captures soil that has already detached. Common erosion control BMPs include temporary seeding and mulching, erosion control blankets, construction entrance pads, and phased grading to minimize the duration of soil exposure. SWPPP regulations generally require that disturbed areas not graded again for 14 or more days be temporarily stabilized with erosion control measures.; See also:BMP Sediment Control Final Stabilization
E&O Insurance (Errors & Omissions): Professional liability insurance that covers a consultant or firm against claims arising from errors, omissions, or negligent acts in the delivery of professional services. In SWPPP consulting, E&O coverage protects project owners from financial losses caused by plan deficiencies, incorrect NOI filings, or inspection documentation errors that lead to regulatory action. E&O coverage is not required by any SWPPP permit program as a condition of consulting work — it must be independently verified by the project owner before engaging a consultant. Many solo practitioners operate without E&O coverage.; See also:General Liability

F

Final Stabilization: The condition under which a construction site has achieved permanent protection from erosion and no further land-disturbing activities are expected. Achieving final stabilization is a prerequisite for filing a Notice of Termination (NOT). The standard varies by state and climate: under the federal CGP, final stabilization requires 70% uniform perennial vegetative cover across all disturbed areas, or equivalent non-vegetative permanent stabilization (pavement, riprap). Under NMPDES for arid and semi-arid areas, final stabilization requires 70% of the pre-disturbance native species density — a significantly more difficult standard to achieve in desert environments, where native species establishment can require 1–2 growing seasons.; See also:NOT NMPDES SWPPP

G

General Liability Insurance: Insurance coverage that protects against claims of bodily injury and property damage arising from business operations. For SWPPP consultants who are physically present on active construction sites, general liability coverage protects both the consultant and the project owner against claims arising from on-site incidents. Distinct from E&O insurance, which covers professional service errors rather than physical harm. Project owners should verify both types of coverage before engaging any consultant performing on-site inspection or BMP installation work.; See also:E&O Insurance

I

Impaired Water: A water body listed on a state's 303(d) list as failing to meet applicable water quality standards. Construction sites whose stormwater discharges reach an impaired water body face heightened SWPPP requirements and longer NOI waiting periods. In New Mexico, sites within 300 feet of an impaired water body may require Tier 3 classification under the proposed 2026 rule, triggering weekly inspections and discharge monitoring requirements.; See also:303(d) List TMDL ONRW

L

Land Disturbance: Any construction activity that exposes soil or alters the ground surface. Activities that constitute land disturbance for permit threshold purposes include clearing and grubbing, grading, excavation, filling, foundation work, utility trenching, road base preparation, demolition involving earthwork, and creation of stockpiles. The acreage of land disturbance — including all phases and the common plan of development if applicable — determines whether NPDES stormwater permit coverage is required.; See also:Common Plan of Development CGP Disturbed Area

M

MSGP (Multi-Sector General Permit): The EPA permit governing stormwater discharges from industrial facilities across 29 industrial sectors. Unlike the CGP, which is temporary and tied to construction activity, the MSGP is permanent — it applies to the ongoing operations of industrial facilities and renews every five years. MSGP SWPPPs require annual review and recertification, and the permit imposes sector-specific benchmark monitoring with laboratory analysis of stormwater samples. The 2021 EPA MSGP expired February 28, 2026 and is currently operating under administrative continuance.; See also:CGP SWPPP Benchmark Monitoring Administrative Continuance
MS4 (Municipal Separate Storm Sewer System): A publicly owned conveyance system (pipes, channels, culverts, gutters) that discharges stormwater to waters of the United States and is operated by a municipality, county, state agency, or other public entity. Operators of regulated MS4s must obtain NPDES permits and implement stormwater management programs. Construction projects that discharge into an MS4 may be subject to additional local stormwater requirements beyond state and federal NPDES obligations — particularly in urbanized areas.; See also:NPDES CGP

N

NAL (Numeric Action Level): Under the MSGP, the threshold benchmark concentration for a specific pollutant parameter. Exceeding a NAL triggers escalating response requirements: Tier 1 (investigate and implement corrective action), Tier 2 (develop and implement a formal NAL Exceedance Response Action Plan). NAL exceedances that persist across multiple monitoring periods can result in mandatory implementation of additional BMPs and notification to the permitting authority.; See also:MSGP Benchmark Monitoring
NMED: New Mexico Environment Department. The state agency that administers the NMPDES program, including the NMPDES Construction General Permit governing stormwater discharges from construction activity in New Mexico. NMED's Surface Water Quality Bureau processes NOI applications via the ePASS online system and issues written permit authorization letters before construction can begin.; See also:NMPDES ePASS
NMPDES: New Mexico Pollutant Discharge Elimination System. New Mexico's state-delegated NPDES program, administered by NMED. NMPDES is an authorization-required permit program — construction cannot begin until the operator receives a written permit authorization letter from NMED, regardless of how long ago the NOI was submitted. Key NMPDES-specific requirements include an arid final stabilization standard (70% of pre-disturbance native species density), prohibition on concrete washout discharge to surface water, and a separate permit requirement for construction dewatering.; See also:NMED NOI CGP Final Stabilization
NOI (Notice of Intent): The application document submitted to the permitting authority (EPA, NMED, ADEQ, TCEQ, or other state agency) to obtain coverage under a Construction General Permit or Multi-Sector General Permit. The NOI identifies the operator, the project location and acreage, the receiving water, and certifies that a SWPPP is in place. In authorization-required states (New Mexico, Arizona), construction cannot begin until a written authorization is received in response to the NOI. In automatic-coverage states (Texas, Colorado, federal EPA states), coverage begins after the applicable waiting period (typically 7 calendar days) without any action from the agency.; See also:CGP NMPDES AZPDES SWPPP NOT
NOT (Notice of Termination): The document filed with the permitting authority to close out NPDES permit coverage upon completion of construction and achievement of final stabilization. Filing the NOT terminates the operator's inspection obligations, recordkeeping requirements, and ongoing permit compliance duties. Operators who complete construction without filing the NOT remain under active permit coverage with continuous inspection obligations — a common compliance gap that generates NOVs months after a project is physically complete.; See also:CGP Final Stabilization NOI
NOV (Notice of Violation): A formal regulatory communication from EPA or a state environmental agency identifying a specific violation of an NPDES permit or applicable regulation. An NOV is typically the first formal enforcement action before penalty assessment. NOVs require a written response within a specified timeframe, a corrective action plan, and documentation of compliance restoration. Failure to respond adequately to an NOV escalates to administrative or judicial enforcement with formal civil penalty assessment.; See also:NPDES Civil Penalty
NPDES (National Pollutant Discharge Elimination System): The federal permit program established under Clean Water Act Section 402 that regulates the discharge of pollutants from point sources to waters of the United States. The Construction General Permit (CGP) and Multi-Sector General Permit (MSGP) are both issued under NPDES authority. Most states have been authorized by EPA to administer their own state NPDES programs (NMPDES in New Mexico, AZPDES in Arizona, TPDES in Texas); in these states, the state permit — not the federal CGP — governs construction stormwater.; See also:CGP MSGP Clean Water Act

O

ONRW (Outstanding National Resource Water): A water body designated under the Clean Water Act's anti-degradation policy as having exceptional recreational, ecological, or scenic value. ONRWs receive the highest level of water quality protection — discharges that would lower water quality are generally prohibited. Many waters in northern New Mexico (segments of the Rio Grande, mountain streams, and wilderness waters) are designated as ONRWs. Construction sites whose stormwater discharges reach an ONRW face extended NOI review periods and enhanced SWPPP requirements, regardless of the site's acreage.; See also:303(d) List NMPDES Anti-Degradation
Operator: Under the NPDES Construction General Permit, any party with (1) operational control over construction plans and specifications, or (2) day-to-day operational control over construction activities at the site. In practice, this means the project owner (always an operator) and the general contractor (almost always an operator) typically share permit obligations simultaneously. Major subcontractors performing significant earth disturbance may also qualify as operators. The operator definition is broader than most parties realize — it is a common source of enforcement exposure when permit coverage is obtained by only one party.; See also:CGP NOI SWPPP

P

Point of Discharge: A specific location where stormwater leaves the construction site boundary and enters a receiving water, storm drain, drainage ditch, or other conveyance. The SWPPP must identify all points of discharge and specify the BMPs protecting each one. Under the CGP, discharge observations (visual assessment of what is actually leaving the site during a storm) must be conducted at each discharge point during or immediately following storm events.; See also:SWPPP BMP Receiving Water

Q

Qualified Inspector: The person responsible for conducting SWPPP inspections under the CGP. The federal CGP requires the inspector to be 'knowledgeable about the CGP requirements and the SWPPP for the specific site' but does not mandate a specific credential. State programs vary: New Mexico's proposed 2026 WQCC rule would require specific credentials for Tier 2 and Tier 3 site inspectors; California requires QSP/QSD credentials; Washington requires CESCL certification. SWPPP HUB verifies inspector credentials against applicable federal, state, and local permit program requirements for every consultant in its network.; See also:CGP NMPDES SWPPP

R

Receiving Water: The water body — stream, river, lake, wetland, storm drain, or drainage channel — that ultimately receives stormwater discharges from the construction site. The SWPPP must identify the name of the receiving water and assess whether it is listed as impaired (303(d) list) or designated as an ONRW, as these designations trigger enhanced SWPPP requirements. Incorrectly identifying the receiving water — a common NOI deficiency — is one of the most frequent causes of NMED and ADEQ processing delays.; See also:303(d) List ONRW NOI SWPPP

S

Sediment Control: BMPs designed to capture soil particles that have already detached from the ground surface and prevent them from leaving the site. Contrast with erosion control, which prevents detachment in the first place. Common sediment control BMPs include silt fence, compost sock check dams, storm drain inlet protection, sediment basins, and vehicle tracking pads. Sediment control is the last line of defense — effective erosion control reduces the amount of sediment that sediment control BMPs must capture.; See also:Erosion Control BMP Silt Fence Sediment Basin
SPCC (Spill Prevention, Control, and Countermeasure Plan): A site-specific written plan required under Clean Water Act Section 311 for facilities that store oil in above-ground containers totaling 1,320 gallons or more and have a reasonable potential for a spill to reach navigable waters. The SPCC plan is distinct from a SWPPP — it covers oil spill prevention, not stormwater runoff. SPCC is administered directly by EPA (not delegated to states). A construction project or industrial facility can require both a SWPPP and an SPCC plan simultaneously. For facilities with up to 10,000 gallons of oil storage that meet certain conditions, a simplified self-certified Tier I Qualified Facility SPCC plan may be used.; See also:SWPPP Clean Water Act
SWPPP (Stormwater Pollution Prevention Plan): A site-specific written document required by the NPDES Construction General Permit (CGP) or Multi-Sector General Permit (MSGP) that describes how a facility or construction project will prevent stormwater from carrying pollutants off-site. A SWPPP must be completed before an NOI is filed and must remain on-site throughout the duration of permit coverage. The SWPPP is a living document — it must be amended whenever site conditions change materially. Under the MSGP, the SWPPP must be reviewed and recertified annually.; See also:CGP MSGP BMP NOI NOT

T

TCEQ: Texas Commission on Environmental Quality. The state agency that administers the TPDES (Texas Pollutant Discharge Elimination System) program, including the Texas Construction General Permit (TXR150000). Texas uses automatic coverage — permit coverage begins 7 calendar days after NOI submission without requiring a written authorization letter from TCEQ.; See also:TPDES CGP
TMDL (Total Maximum Daily Load): A calculation of the maximum amount of a specific pollutant that a water body can receive and still meet water quality standards. TMDLs are developed for water bodies on the 303(d) impaired waters list. When a TMDL has been established for a receiving water, construction site SWPPP requirements may include specific numeric discharge limits or monitoring obligations related to the TMDL pollutant — particularly for sediment and turbidity.; See also:303(d) List Impaired Water
TPDES: Texas Pollutant Discharge Elimination System. Texas's state-delegated NPDES program, administered by TCEQ. The Texas Construction General Permit (TXR150000) uses a 7-business-day routine inspection frequency (rather than 7 calendar days like most other programs) and provides automatic permit coverage 7 days after NOI submission.; See also:TCEQ CGP NPDES
Turbidity: A measure of water clarity, expressed in Nephelometric Turbidity Units (NTU). Turbidity is caused by suspended particles — primarily sediment — in stormwater discharges. High turbidity in receiving waters is a direct indicator of sediment pollution from construction activity and is a primary enforcement focus for regulators conducting visual inspections of construction site discharges. Under some state permits and individual permit conditions for sites near sensitive receiving waters, turbidity monitoring with numeric limits is required.; See also:Sediment Control Benchmark Monitoring 303(d) List

W

Waters of the United States (WOTUS): The jurisdictional scope of Clean Water Act protections — those water bodies over which the federal government has regulatory authority under the CWA. The precise definition of WOTUS has been subject to extensive litigation and regulatory revision; the current definition following the Supreme Court's 2023 Sackett v. EPA decision excludes wetlands without a continuous surface connection to traditionally navigable waters. WOTUS jurisdiction determines when NPDES permits are required and which discharges are regulated. State water quality programs often extend protection to intrastate waters beyond WOTUS.; See also:Clean Water Act NPDES
WQCC: New Mexico Water Quality Control Commission. The state body responsible for adopting water quality standards and regulations under the New Mexico Water Quality Act. The WQCC sets the rules that NMED administers, including the NMPDES Construction General Permit terms. The WQCC is conducting a formal rulemaking hearing June 8–18, 2026 to adopt updated NMPDES construction stormwater rules — the most significant change to the NM program in over a decade.; See also:NMPDES NMED

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