The City’s Post- Construction Stormwater Management Program addresses the following primary objectives for controlling stormwater runoff: (1) stable conveyance and channel protection; (2) flood control; (3) groundwater recharge; and (4) water quality.
As urban areas continue to develop and sites redevelop the volume of runoff rises because of the increase in impervious areas. Previously, stormwater management philosophy concentrated on only addressing the effects of the additional volume of flow being generated. However, with the enactment of the NPDES Phase II Stormwater Permit regulations the current philosophy of stormwater management now focuses on a more integrated approach that acknowledges the aspects of volume, rate and quality as well as the relationship between ground water and surface water.
In 2015, the City received its individual NPDES Permit authorizing discharge from the City’s MS4. The permit establishes the following Post Construction Storm Water Runoff guidelines for the minimum treatment volume standard and the channel protection criteria:
“a) Water Quality Treatment Performance Standard Treat the first one (1) INCH of runoff from the entire site. BMPs shall be designed on a site-specific basis to achieve a minimum of 80 percent removal of total suspended solids (TSS) as compared with uncontrolled runoff or a discharge concentration of TSS not to exceed 80 milligrams per liter (mg/l).
b) Channel Protection Performance Standard The post-construction runoff rate and volume of discharge shall not exceed the predevelopment rate and volume for the project site for all storms up to the two-year, 24-hour storm.”
The City’s "Post-Construction Guidance Manual (PDF)" was developed as a means for providing standards to assure quality and consistency in the permitting, design, construction and maintenance of all stormwater infrastructure facilities constructed within the City of East Lansing.
This “Post-Construction Stormwater Management Guidance Manual” is divided into three separate sections. Chapter I is the City of East Lansing “Post Construction Stormwater Management Ordinance (PDF)” which provides the regulatory legal foundation for administering and enforcing the specific elements of the stormwater program. The ordinance was based in part on the model ordinance originally developed as part of the “Low Impact Development Manual for Michigan”.
The ordinance provides the regulatory structure necessary for establishing, implementing and enforcing those requirements of the City of East Lansing’s Post Construction Stormwater Management Program contained within its NPDES Permit. The ordinance specifies the overall design criteria for complying with the City’s Post Construction Stormwater Management Program.
The overall goal of Chapters II and III is to provide the guidelines and technical tools necessary to meet the requirements of the Ordinance; to promote uniformity, consistency and efficiency throughout the permit and enforcement process; to provide opportunities to reduce the impacts of the stormwater requirements through offsets and credits; and to ensure that developers adhere to the minimum standards set forth in the Ordinance for impacting watersheds throughout the City of East Lansing.
Chapter II of this document, the City of East Lansing “Stormwater Policy & Procedures Manual”, outlines the administrative process and procedures for the stormwater plan review, inspection, and maintenance processes.
Chapter III of this document, the City of East Lansing “Stormwater Design Manual”, contains detailed standards and practices that may help designers and plan reviewers select, design, review, and approve both structural and non-structural stormwater BMPs for their development sites.
The City’s Post Construction Stormwater Management Ordinance shall be applicable to all land development (new development and redevelopment), including but not limited to, site plan, plot plan and plat applications as well as any grading applications, that meet one or more of the following criteria unless exempt pursuant to Section 34-302:
(i.) Projects that disturb one (1) acre or more.
(ii.) Projects less than one (1) acre that are part of a larger common plan of development or sale that would disturb one (1) acre or more.
(iii.) Projects less than one acre with special circumstances such as development in floodplains, wetlands, or other critical areas and any development or redevelopment that may have a significant downstream impact.