City of Mexico Stormwater Management Plan
2021 STORMWATER MANAGEMENT PLAN UPDATE
The City of Mexico is seeking public input on revisions to its Stormwater Management Plan (SWMP). As a regulated Municipal Separate Storm Sewer System (MS4) community, the City is required to develop Best Management Practices that mitigate pollutants entering the storm sewer system. A draft of the City’s SWMP may be obtained in-person at City Hall or by viewing the PDF here. Comments may be provided via the online form here, emailing email@example.com, or by calling 573-581-2100 (ext. 3). Please submit all comments to the City’s Engineering Division no later than 5pm on March 8th. A public hearing for the proposed SWMP will be held during the City Council Meeting on March 8th at 6pm where an opportunity for further comment will be provided. Once all comments have been reviewed, and the Stormwater Management Plan has been finalized, the document will be sent to the Missouri Department of Natural Resources (MDNR) for final review and approval. The proposed City MS4 Permit, issued to the City by MDNR, has also been posted here for reference when reviewing the SWMP.
The City of Mexico is a regulated small Municipal Separate Storm Sewer System (MS4) community. As such, the City works alongside the Missouri Department of Natural Resources and the Environmental Protection Agency to prevent and/or minimize stormwater pollution. To learn more about the MS4 Program, please visit the Missouri Department of Natural Resources' MS4 Webpage.
There are many parts, often referred to as Best Management Practices (BMPs), that make up the City's Stormwater Management Plan. These parts range from public education and outreach to storm sewer mapping and good housekeeping. The City's Stormwater Management Plan has been made available as a PDF for download here.
Provide Your Input:
Input from the public is a critical step to the City's Stormwater Management Plan. Please feel free to submit any questions, comments, or concerns using the online stormwater form here or by calling 573-581-2100 ext. 3.
What you need to know if you're building in Mexico:
Is the City's MS4 Program relevant to your construction site?
Please review Chapter 16 Article II of the Mexico City Code to determine if your site meets the criteria adopted through the City's MS4 program and associated Stormwater Ordinances. A link to Section 16-21 (Applicability) of the City's Stormwater Ordinances may be found here. If you have further questions about applicability, please contact the Engineering Division.
What if your construction site meets the City's MS4 applicability criteria?
Certain design requirements, calculations, and documentation will need to be submitted for review prior to the start of construction. More details on these requirements may be found in subsequent tabs above.
What if your construction site does NOT meet the City's MS4 applicability criteria?
The stormwater design requirements, calculations, and documentation outlined in Chapter 16 Article II, and III will not be required. This does not negate the need for good workmanship and personal responsibility on-site. Should off-tracking of debris occur, pollution be found on-site, or other environmental concerns be noted, the City's Engineering Division will conduct an investigation of the construction site to determine what efforts may be needed for mitigating stormwater pollutants. All other permits for the site will still be required and the contractor, as well as all subcontractors, must meet the City's Business License Requirements (contact the City Clerk for more details on Business License Requirements). Examples could range from Building/Demolition Permits to a Floodplain Development Permit.
What City permits are needed as part of the MS4 Program?
- Land Disturbance Permit - This is required for any work which disturbs one acre or more of ground (i.e. disturbing the root structure of vegetation of one acre of more). The permit application may be found here.
- Stormwater Discharge Permit - This is required to discharge stormwater to the City MS4. The permit application may be found here.
What other City permits may be needed as part of the construction project?
- Building and Demolition Permits - Obtained from Community Development Department.
- Floodplain Development Permit - Obtained from the Engineering Division of Public Works.
- Right of Way Permit - Obtained from the Engineering Division of Public Works.
What documents does the City Clerk need prior to start of construction?
- Business License - This is required for both the general contractor and all subcontractors working on the project.
- Proof of Insurance - Standardized insurance coverage is required for all contractors obtaining business licenses within the City of Mexico. Workman's Compensation is also a requirement of the Proof of Insurance Process.
If you have any questions about these requirements, please feel free to contact the City Clerk by phone at 573-581-2100 ext. 220 or by email at firstname.lastname@example.org.
Are there other documents required to be submitted as part of the MS4 Program?
- Stormwater Maintenance Agreement (SWMA) - This document is required to be executed by the owner of the land for which the stormwater facilities are being constructed. The document is recorded with the Audrain County Recorder of Deeds and runs with the land to provide a basis of operating, inspecting, and maintaining on-site stormwater facilities (e.g. detention basin, rain garden, vegetative swale, etc.). A link to this document may be found here.
- Stormwater Pollution Prevention Plan (SWPPP) - This document details how the contractor shall maintain stormwater quality and quantity controls throughout construction. It designates an on-site responsible party, sets an inspection schedule, provides inspection checklists, and more. Additional details for the SWPPP may be found in Section 184.108.40.206 of the Stormwater Design Guide here.
The above permits are in addition to any permits required by State, Federal, or other governing authorities applicable to the construction site.
How does the design process work into the City's MS4 Program?
The City requires a set of Civil Plans and Stormwater Calculations be submitted for review prior to the start of construction. These plans and calculations must be signed and sealed by a professional engineer licensed in the State of Missouri.
A Stormwater Design Manual has been developed to assist with the design process and meet the City's MS4 requirements. Links to each chapter of this manual may be found below:
Chapter 1 - General Information
- 1.1 Introduction
- 1.2 Purpose/Background
- 1.3 Goals
- 1.4 Chapter Summaries
- 1.5 Requirements of Other Agencies
Chapter 2 - Plan Requirements
- 2.1 Scope
- 2.2 Permit Applications
- 2.3 Development Review Process
- 2.4 Concept Review
- 2.5 Pre-Application Meeting
- 2.6 Preliminary Plat/Plan Review
- 2.7 Construction Plan Review
- 2.8 Final Plat Submittal
- 2.9 Modifications to Plans
- 2.10 General Plan Requirements
Chapter 3 - Hydrology and Hydraulics
- 3.1 Scope
- 3.2 Computation Methods for Runoff
- 3.3 Water Quality Hydrology Methods
- 3.4 Hydraulic Calculations for Pipes, Culverts, and Open Channels
- 3.5 Hydraulic Analysis of Systems by Computer Models
Chapter 4 - Enclosed Systems
- 4.1 General Guidance
- 4.2 Existing Drainage System
- 4.3 Inlet Design
- 4.4 Gutter Flow
- 4.5 Protection for Streets
- 4.6 Enclosed Pipe Systems
- 4.7 Overflow Provisions
- 4.8 Easements
Chapter 5 - Open Channels
- 5.1 Natural Streams
- 5.2 Engineered Channels
- 5.3 Easements
Chapter 6 - Stormwater Quality and Quantity
- 6.1 Introduction
- 6.2 Runoff Reduction
- 6.3 Treatment of the Water Quality Volume
- 6.4 Channel Protection and Flood Control
- 6.5 Operation and Maintenance Plan Requirements
Chapter 7 - Environmentally Sensitive Areas
- 7.1 Introduction
- 7.2 Protection and Hazard Minimization Approach
- 7.3 Buffer Requirements for Environmentally Sensitive Areas
- 7.4 Wetland Protection
- 7.5 Water Body Identified as Critical Habitat for Endangered Species
- 7.6 Class P Stream
Chapter 8 - Erosion and Sediment Controls
- Document providing standards to typical Erosion and Sediment Control BMPs.
What documents must be submitted to begin the MS4 Plan Review process?
Not all documents listed in the Permits tab above must be submitted to begin the review process. At a minimum, the City must have the following documents to proceed in a thorough review of the Civil Plans and Stormwater Calculations:
- Land Disturbance Permit Application and Fee
- Stormwater Discharge Permit Application and Fee
- A Fully Signed and Sealed Civil Plan Set
- A Fully Signed and Sealed set of Stormwater Calculations
- Stormwater Pollution Prevention Plan
- Stormwater Maintenance Agreement
Other required documents may be submitted later; however, they must still be submitted prior to start of construction.
How long does the MS4 Plan Review process take?
This can vary depending on the size and complexity of the project. The Engineering Division strives to provide the first round of comments on the above documents within two weeks from the received date.
What is reviewed during the MS4 Plan Review process?
The Engineering Division conducts a review to be sure the plans and calculations meet all criteria in the Stormwater Design Manual and City Ordinances. This is a comprehensive process and usually involves communication with the Design/Consulting Engineer. Communication is a key part of this review and can contribute to a faster turn-around in review time for the project.
What should you expect while your site is under construction?
The Engineering Division conducts a monthly inspection on each site under construction which meets the MS4 Program applicability criteria. This inspection is conducted to ensure compliance with Land Disturbance Permit requirements, City Stormwater Ordinances, and the on-site Stormwater Pollution Prevention Plan (SWPPP).
What should you expect with a monthly MS4 Inspection?
- Review of Each On-Site Best Management Practice (BMP)
- This could include checking silt fence for proper embeddment/installation or reviewing a fueling station for spills/leaks.
- General Site Walk Through
- This is conducted to ensure the overall site, including perimeter controls, is in compliance with its SWPPP. A significant emphasis is placed on reviewing perimeter controls to ensure sediment, or other pollutants, are not traveling off-site.
- Review of Stormwater Inspection Paperwork
- A review of the paperwork for each stormwater inspection conducted by the contractor is made to ensure the inspection schedule put into place by the SWPPP is followed.
What should you expect after construction is complete?
The Engineering Division will work with the Engineer, Contractor, and Owner to close out the Land Disturbance Permit for the site and move it into the Stormwater Management phase. A Land Disturbance Permit cannot be closed until a viable stand of vegetation has been established and the overall site is considered stable. Until this point is reached, the Land Disturbance Permit holds the Contractor responsible for any stormwater related issues unless first agreed upon, in writing, by the Owner.
How does the Stormwater Maintenance Agreement factor into the MS4 Program?
Inspection and Maintenance procedures in the Stormwater Maintenance Agreement (SWMA) should be followed as soon as the site's Land Disturbance Permit is closed. Once the Land Disturbance Permit is closed, the responsibility for any stormwater related issues will fall on the Owner. The SWMA includes an inspection and maintenance schedule, as well as inspection sheets to be used for the site detailing what facilities to inspect. The SWMA is recorded at the Audrain County Recorder of Deeds and runs with the land - preserving the operation of on-site stormwater facilities should the ownership of land change.