Stormwater Management Design Standards

In 2002, the State of Michigan began to implement the second permit phase of  the National Pollutant Discharge Elimination System, authorized by the Clean Water Act.  This permit, informally called 'Phase ll', requires municipalities and other governmental agencies with separated stormwater sewer systems to regulate both the quantity and quality of stormwater runoff discharging into state waters.  To accomplish this task, the Macomb County Public Works Office (MCPWO) has updated its stormwater engineering standards, the first major revision of the rules since 1967.  The new standards, adopted July 30, 2008 and effective August 1, 2008, will be used to evaluate development proposals that discharge stormwater into County drains.

 

Three meetings were held in April to solicit comments from local communities, developers and engineers on the new stormwater engineering standards.  The meetings focused on the incorporation of the new water quality requirements, as well as changes to the existing requirements.  MCPWO reviewed all of the comments received and made several changes to the draft standards.  Most of the changes involved removing requirements that were deemed outside of the MCPWO's jurisdiction.

A Technical Reference is currently under development to aid users in the implementation of the new standards.  The difference between the standards and the reference is that the reference includes guidance rather than requirements.

Projects that have already started the review process in the MCPWO before the effective date will continue to be reviewed under the old standards.  Projects that arrive on or after the effective date will be reviewed using the new standards.

Copies of the new engineering standards are available for download FREE from this website or can be purchased from the MCPWO for $15 dollars, after September 1, 2008. If you have any questions regarding the new engineering stormwater standards, please contact the Engineering Division at 586-469-5910.

 

Click here to download Procedures and Design Standards for Stormwater Management

(Standards printed from this website are formatted for double-sided printing.)

                

       Please check the website periodically for any changes or corrections made to the stormwater standards.  The link below  will display any changes or corrections made, along with the effective date.

MCPWO Amendments to the Procedures and Design Standards for Stormwater Management

SITE EVALUATION TOOL  (SET)

The Site Evaluation Tool  (SET) is a Microsoft Excel spreadsheet, and is designed to aid in the assessment of development plans and available Best Management Practices (BMPs) to achieve water quality objectives.  The BMPs incorporated within the model address the most important current and future water quality issues that development can potentially influence.  In addition, the Macomb County SET calculates the site's Water Quality Volume (WQv) and Channel Protection Volume (CPv), two of the Stormwater Criteria which a development site is required to meet under design standards adopted by Macomb County in 2008.  The SET also provides a means to easily calculate the benefit of Stormwater Credits for reducing the required WQv and CPv treatment volume.  The Stormwater Criteria and Stormwater Credits are discussed in detail in Macomb County's Procedures and Design Standards for Stormwater Management.

The SET may be a useful resource for many in the development community.  Developers can use it as a screening tool for testing various site configurations to find ways of helping a site achieve water quality goals and reduce pollutant loads in a cost-effective manner, through the judicious use of both structural BMPs and Stormwater Credits.  A completed SET can be submitted with a site plan as part of a development approval process.  Municipal staff can use the tool to determine compliance with water quality regulations.  A community interested in pursuing a 319 grant for funding assistance for an innovative site design could use the SET to demonstrate pollutant removal benefits.  Other practitioners may find it useful as an educational tool for providing a better understanding of the water quality impacts of development and the benefits of  BMPs.

Additional Resources available for the Macomb County Site Evaluation Tool  (SET):

The User's Manual discusses in detail the use of the SET, includes screen shots and descriptions of required inputs, and gives an example of its application.

The Model Documentation document discusses the underlying models and methodologies used in the Macomb County SET.  It provides details on key assumptions used by the SET, including parameters used to calculate pollutant loads, BMP pollutant removal efficiencies, methods used to calculate Macomb County's Stormwater Criteria for Water Quality Volume (WQv) and Channel Protection Volume (CPv), and calculations for implementing Stormwater Credits for reducing the required WQv and CPv.