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  • Stormwater

    Sabino Canyon CreekManaging runoff from our homes and businesses into roadways and drainageways keeps surface water clean, which in turn supports riparian areas and preserves our high quality groundwater. Strategies to reduce pollutants, like bacteria and copper, from flowing into our surface waters include the following:

    Outreach & Participation: Encourage clean-up of key pollutants & engage the community in on-going projects like Adopt-A-Road.
    Illicit Discharges: Pick up pet waste. Toss trash in the right place. Recycle auto fluids.
    Homes & Businesses: Keep oils, anti-freeze, fertilizers & pesticides away from runoff.
    Industrial Facilities: Organize chemicals, equipment and work processes to keep chemicals out of the rain. Weed with care. Prevent spills. Clean-up spills.
    Construction Sites: Minimize wastewater from washout of concrete, stucco, and paint as well as fuels, oils, soaps, solvents and trash from flowing into stormwater.

    Construction General Permits (CGPs)

    Obtain your CGP NOI from ADEQ before construction activity begins, like breaking ground or disturbing land on a project one acre or larger. Land disturbance includes clearing, grading, excavating, and stockpiling fill material for building roads, homes, and buildings as well as demolition activities. The permit functions to prevent construction pollutants from being transported into desert washes, intermittent streams, lakes, wetlands, tributaries, and county-maintained roadways.
    1. Plan and Develop Control Measures for Construction Site Activities

      Schedule construction activities and the installation of control measures to limit soil disturbance and the potential for stormwater pollution. The ADOT Erosion and Pollution Control Manual, CALTRANS Construction Manual, and AASHTO Construction Stormwater Field Guide provide guidance on the uses, limitations, design considerations and, maintenance needs of control measures.

    2. Obtain a (CGP) Notice of Intent (NOI)

      To obtain a CGP from ADEQ, register for a free myDEQ Account and then apply for a CGP NOI. Referring to ADEQ's 2020 CGP, EPA's 2017 CGP or ADEQ's SWPPP template are helpful while completing the NOI. PimaMaps may be used to prepare the general map and site map (PimaMaps Quick Start Guide).

    3. Manage Site During Construction

      Keep an updated SWPPP on-site identifying the stormwater team, sequence of construction activities, control measures, a summary of potential pollutants, waste management procedures, and a record of 1) inspections, 2) maintenance actions, 3) corrective actions, 4) rain log using an on-site rain gage or information from a Pima County weather station, and 5) other information required by the permit

    4. Follow Local Ordinances

      In addition to following the CGP, operators are also required to follow Pima County Ordinances. These ordinances require a clean site, stormwater conveyance, proper grading, and minimization of both fugitive dust and erosion.

    5. When the Project is Complete

      The site operator(s) closes the NOI by submitting an electronic Notice of Termination (NOT) via myDEQ. The NOT certifies the following:
      • Final stabilization is complete
      • Temporary erosion and sediment controls have been removed.
      • Another operator has filed an NOI and is responsible for compliance at the site.
      Note: Check to see if these additional Pima County Permits are needed for the project:
      Fugitive Dust Activity Permit
      Grading, Hillside and Native Plant Preservation Ordinance (NPPO) Permits

    Multi-sector General Permits (MSGP) for Industrial Facilities

    Obtain your MSGP from the Arizona Department of Environmental Quality (ADEQ) for industrial activities with selected Standard Industrial Classification (SIC) codes. This permit functions to restore and maintain the chemical, physical, and biological integrity of the Nation’s waters, such as desert washes, intermittent streams, lakes, wetlands, and tributaries.
    1. Obtaining an MSGP from ADEQ

      To obtain an MSGP from ADEQ, register for a free myDEQ Account and then apply for an AZPDES Industrial Stormwater MSGP. Refer to ADEQ's 2019 MSGP or EPA's website for industrial activities. EPA has additional guidance for Stormwater Pollution Prevention Plans (SWPPP) and sampling and monitoring plans. Applicants need to identify their primary SIC code. For more information to determine an SIC Code contact NAICS Association, US Census Bureau or US Department of Labor, OSHA . Pima County MapGuide may be used to prepare the general map and the site map (Tips for Using MapGuide).

    2. Operating your facility with an MSGP

      Keep a current SWPPP on site identifying the stormwater team, a summary of potential pollutants, control measures, and records of inspections, maintenance actions, rainfall log using an on-site rain gauge or a Pima County weather station, and corrective actions. If you collect water samples, EPA's Monitoring and Sampling Guide (March 2009) provides instructions to collect stormwater samples and coordinate with a laboratory to analyze the sample(s) for the needed parameters. For more information see EPA Industrial Stormwater Fact Sheet Series.

    3. Transferring ownership of facility

      The facility operator(s) must submit a Notice of Termination (NOT) using their myADEQ account. The terms and conditions of the MSGP should be met until the facility's authorization has been terminated.

    Low Impact Development and Green Infrastructure

    Improvements in the quality of urban stormwater can be achieved by retrofitting the existing landscape with a variety of Low Impact Development and Green Infrastructure features. Pima County has been developing tools and resources for the public and professionals to build these features that accomplish operational goals as well as fulfill stormwater permit requirements.
    Pima County MapGuide gives access to satellite imagery, topography, roads, washes, and other important information (GIS Resources). 

    Watersheds in the Tucson Basin provides maps showing where the water flows when it rains. The Tucson Regional Watershed Map provides a three dimensional view of the Tucson Basin.

    Pima County Regional Flood Control District operates and maintains a network of real-time sensors used to collect hydrometeorological data.  This network provides information to county personnel and other agencies about precipitation, stormwater runoff, and weather conditions affecting our regional watersheds. Using radio telemetry, sensors report data in the National Weather Service Automated Local Evaluation in Real Time (ALERT) format.  The ALERT sensor data  is available via an interactive map through the Regional Flood Control District.

    History of Pima County's MS4 Permit

    Federal and State MS4 Regulations

    In 1972, the U.S. Congress passed the Clean Water Act (CWA) to protect and improve the quality of water in the United States. The CWA required the U.S. Environmental Protection Agency (EPA) to regulate the discharge of pollutants to surface waters by issuing National Pollutant Discharge Elimination System (NPDES) permits. Initially, the NPDES program focused on reducing pollutants from point source discharges such as industrial process wastewater and municipal wastewater. While the water quality improved, degraded water remained and was observed to flow from diffuse sources, or non-point sources, such as agriculture, urban areas, construction sites, industrial facilities, landfills and mining areas.

    EPA addressed pollutants from non-point sources in 1990 by establishing regulations for permitting stormwater discharges associated with industrial activities, construction activities, concentrated animal feed operations (CAFO), and municipal areas with a high likelihood of releasing pollutants. EPA developed a permit for each activity and began issuing permits in 1992.

    The State of Arizona assumed primacy, or authority, to implement the NPDES permit program at the state level on December 5, 2002 when the Arizona legislature enacted enabling legislation. The Arizona Department of Environmental Quality (ADEQ) administers the program and issues Arizona Pollutant Discharge Elimination System (AZPDES) permits to protect surface water quality.

    Pima County's Permit

    Pima County MS4 Permit AreaEPA issued an NPDES permit to Pima County in 1997. ADEQ issued Pima County’s AZPDES permit on June 16, 2011 and renewed it on December 21, 2020. The county’s new permit area consists of 2,087 miles of roadways, 39 miles of storm drains and infrastructure collecting runoff that flows into stream channels. Pima County is a Phase I medium municipal separate storm sewer system (MS4), based on a population between 100,000 and 250,000 according to the 1990 Census.

    Pima County developed a Stormwater Management Program to ensure the quality of stormwater discharges were managed to the maximum extent practicable. The program includes control measures to minimize the discharge of pollutants carried by runoff. Components of Pima County's Stormwater Management Program include the following:

    1. Public Education and Outreach
      1. Presentations and seminars on stormwater topics.
      2. Assist local businesses in complying with environmental requirements.
      3. Supply libraries with environmental awareness information through EcoNook for Desert Dwellers and Eco Kids Corner.
    2. Public Involvement and Participation
      1. Provide stormwater-related information on Pima County website.
      2. Sponsor the Adopt-a-Roadway program to keep roadways and public lands clean.
      3. Manage the complaint Hotline so the public can report environmental issues.
      4. Sponsor community programs encouraging recycling and conservation.
    3. Illicit Discharge Detection and Elimination (IDDE)
      1. Investigate stormwater complaints and facilitate clean-up.
      2. Screen outfalls for potential discharges.
    4. Practice good housekeeping and pollution prevention at County Facilities
      1. Implement Spill Prevention and Response Plans.
      2. Manage use of pesticides, herbicides & fertilizers in accordance with regulations.
      3. Inspect facilities to assess potential for discharge and assist managers.
    5. Residential and Commercial Control Measures
      1. Maintain drainageways and roadways
      2. Verify proper clean-up of constructions sites at end of project.
      3. Restore riparian habitats and ecosystems to maintain a full range of plants and animals.
      4. Acquire Open Space lands to preserve natural resources.
      5. Acquire floodprone properties to minimize erosion and flooding.
      6. Issue Air Quality Activity permits to reduce tracking dirt from construction sites.
    6. Industrial Facilities
      1. Inspect facilities to verify they conform with stormwater regulations.
      2. Assist business in maintaining compliance.
    7. Construction Sites
      1. Review design plans to verify they meet stormwater regulations.
      2. Inspect sites to verify erosion and sediment controls are in place and maintained.
      3. Assist construction operators in maintaining compliance.
    8. Watershed Monitoring
      1. Collect stormwater samples at 5 locations within the watershed.
      2. Characterize the discharge for consistency with state Surface Water Quality Standards.

    Helpful Tips to Maintaining Good Surface Water Quality

    1. Use stormwater as a resource to irrigate landscaping at your home or business.
    2. Apply pesticides and herbicides according to manufacturers recommendations well before a rainfall event.
    3. Properly dispose of household hazardous waste.
    4. Repair leaking vehicles.
    5. Properly dispose of pet waste.
    6. Report illegal dumping by contacting us at 520-724-7400 or on-line.

    Local, State & Federal Laws, Rules & Regulations for Municipal Separate Storm Sewer System (MS4)


    Pima County Code
    Title   7 - Environmental Quality
    Title 10 - Traffic and Highways
    Title 16 - Floodplain Management
    Title 18 - Zoning
    Pima County Environmental Policy
    Pima County Technical Policy Regulating Riparian Habitat Mitigation


    Arizona Department of Environmental Quality    
        Surface Water Protection Program 
        State Water Quality Certification (Based on CWA Section 401 - Certification)
        Stormwater protection (Based on CWA Section 402 - NPDES)
        Arizona Revised Statutes - Title 49 Environment
        Arizona Administrative Code - Title 9 Health Services (Labs)
        Arizona Administrative Code - Title 12 Natural Resources
        Arizona Administrative Code - Title 18 Environment

    Arizona Department of Agriculture
        Office of Pest Management


    Clean Water Act

    33 USC §1251 et seq. Water Pollution Prevention & Control
    33 CFR 238 Navigable Waters: Flood Damage Reduction
    40 CFR 122 402-NPDES
    40 CFR 230 404-Dredge & Fill
    42 USC 13101 et seq. Pollution Prevention Act of 1990

    Safe Drinking Water Act

    42 USC § 300f Safety of Public Water Systems
    40 CFR 141 Primary Drinking Water Regulations
    40 CFR 143 Secondary Drinking Water Regulations

    Toxic Substances Control Act

    15 USC § 2601 et seq. Toxic Substances Control
    40 CFR 300-399 Superfund & Emergency Planning & Community Right-to-know Act (EPCRA)

    Federal Insecticide, Fungicide and Rodenticide Act (FIFRA)

    7 USC § 136 et seq. Insecticides & Environmental Pesticide Control
    40 CFR 122.3NPDES Exclusions
    40 CFR 129 Toxic Pollutant Effluent Standards

    Comprehensive Environmental Response, Compensation, & Liability Act (CERCLA)

    42 USC § 9601 et seq. Comprehensive Environmental Response, Compensation, and Liability
    40 CFR 300-399 Superfund & EPCRA

    Useful links

    EPA Region 9
    U.S. Code
    Code of Federal Regulations - Title 33: Navigation and Navigable Waters
    Code of Federal Regulations - Title 40: Protection of Environment, Chapter I (EPA)

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