Ann Arbor logo
Share to Facebook Share to Twitter Bookmark and Share
File #: 16-0890    Version: 1 Name: 6/20/16 - Developer Offset Mitigation Ordinance
Type: Ordinance Status: Passed
File created: 6/20/2016 In control: City Council
On agenda: 7/7/2016 Final action: 7/7/2016
Enactment date: 6/20/2016 Enactment #: ORD-16-13
Title: An Ordinance to Amend Sections 2:42.5 and 2:42.6 of Chapter 28 (Sanitary Sewer) of Title II of the Code of the City of Ann Arbor (Ordinance No. ORD-16-13)
Sponsors: Christopher Taylor
Attachments: 1. 16-13 dom ordinance 6-10-16 Briefed and Approved.pdf, 2. 16-13 dom ordinance 6-10-16 Briefed.pdf, 3. dom ordinance 6-10-16.pdf, 4. DM_Guidelines_DRAFT 2016 06 14.pdf


An Ordinance to Amend Sections 2:42.5 and 2:42.6 of Chapter 28 (Sanitary Sewer) of Title II of the Code of the City of Ann Arbor (Ordinance No. ORD-16-13)


The purpose of the proposed code amendment is to modify the code provision relating to requirements for new connections made to the City’s sanitary sewer system.   The code amendment will incorporate the City’s Developer Offset Mitigation (DOM) Program requirements which were initially established by Council Resolution in 2003.


The City of Ann Arbor created the Developer Offset Mitigation (DOM) Program to protect the health and safety of our community and the environment, using a city-wide approach.  The DOM Program was established on August 18, 2003 by Council Resolution R-362-8-03 (and most recently modified on June 15, 2015 by Council Resolution R-15-213) to reduce the potential for development sites to exacerbate sanitary sewer backups or sanitary system surcharging during wet weather rain events.  At the time DOM was established, the City was removing wet weather flows from the sanitary system in response to sanitary basement backups that occurred in various locations during large storm events in 1998 and 2000. This effort was mainly implemented through the City’s Footing Drain Disconnection (FDD) program, which occurred between 2001-2012.

DOM requires developments that are adding new flow into the City’s sanitary system to effect a net reduction in overall flow to the sanitary system.  Applicable development projects must mitigate 110% of the estimated net new flow contribution from the development into the sanitary system.  DOM aids in protecting the health and safety of our community and environment by not allowing new development to exacerbate sewage collection system capacity issues or “MDEQ permitted” overflows of partially treated sewage by our wastewater treatment plant to the Huron River. 


The City recently completed the Sanitary Sewer Wet Weather Evaluation (SSWWE) project.  Using more than ten years of data, the SSWWE project evaluated the effectiveness of the FDD program at removing wet weather flows, assessed the future risk of basement backups, evaluated alternatives, and set direction for addressing the identified future basement backup risk. Among the project’s findings was that the FDD program has significantly reduced the risk of basement backups in the five target, or focus areas, of the program.  The evaluation also identified five additional potential wet weather risk areas in the system.  Preliminary engineering efforts are underway for addressing these areas (Capital Improvement Projects UT-SN-16-03 through UT-SN-16-07).


With the findings, the SSWWE project’s Citizens Advisory Committee (SSWWE CAC) recommended to the City that the DOM Program should continue, but with modifications.  Some of the recommended modifications were adopted by Council Resolution R-15-213 in 2015.  One of the remaining recommendations from the SSWWE CAC is expanding the mitigation alternatives to allow for a payment-in-lieu option.  The proposed code amendment will amend the current DOM program to allow payment in-lieu as an acceptable flow mitigation alternative.  The payment will be used by the City to fund future sanitary sewer wet weather capacity improvement projects, which include a variety of on-going efforts performed by the City to reduce storm or groundwater inflow and infiltration from the sanitary sewer system.  A resolution to establish the base payment in-lieu amount will be presented to City Council at the regular Council meeting when the ordinance is before Council for second reading.


Approximately twenty members of the development community attended a public meeting held on June 6, 2016 where staff presented this ordinance and provided an opportunity for discussion and questions from the attendees.


Prepared by:  Abigail Elias, Chief Assistant City Attorney

Reviewed by:  Craig Hupy, Public Services Area Administrator

Approved by:  Tom Crawford, Interim City Administrator

Sponsored by:  Mayor Taylor




First Reading:                     June 20, 2016                                                               Approved:  July 7, 2016

Public Hearing:                     July 7, 2016                                                                                    Published:







The City of Ann Arbor ordains:


Section 1. That Sections 2:42.5 and 2:42.6 of Chapter 28 of Title II of the Code of the City of Ann Arbor be amended and replaced to read as follows:


2:42.5. - Capacity required for connection.


(1)                     No connection to the POTW shall be allowed unless there is sufficient available hydraulic and treatment capacity in the POTW for the additional wastewater from the proposed connection.


(2)                     All developments within the city requiring any form of site plan approval, and/or projects requiring an application for a Part 41 Permit from the Michigan Department of Environmental Quality, or a successor agency, are required to offset-mitigate estimated new sewage flows. However, if all the new sanitary system connections for the properties covered by a site plan or by a Part 41 Permit collectively add flow less than the average daily flow from a duplex residential unit, the properties shall be exempt from offset-mitigation requirements.


(3)                     The Public Services Area Administrator or designee shall be the developer offset mitigation program manager, and the Public Services Area Administrator is authorized to develop Developer Offset Mitigation Guidelines to address and govern implementation details such as procedures, flow measurements, and flow mitigation measurements and requirements.


(4)                     Properties requiring site plan approval must disconnect any existing on-site footing drains from the sanitary sewer. 


(5)                     A facility developed by a county, public schools, colleges, universities and other government on property it owns and that is located within the city also must mitigate new sanitary flows to the same extent and in the same manner as a development requiring site plan approval. 


(6)                     Calculations showing the proposed sanitary sewer flow being added by the proposed development shall be included on the utility sheet of the site plan and/or construction plan, as applicable, and be reviewed by the Developer Offset Mitigation program manager. Calculations and the design dry weather flow rates shall be in accordance with the City’s Developer Offset Mitigation Guidelines.


(7)                     Flow mitigation performed after January 1, 2015, and verified and documented by the City, but not assigned to a particular development, may be credited to a specific development without being subject to expiration unless otherwise approved by the Developer Offset Mitigation program manager.


(8)                     Method of flow mitigation alternative shall be submitted for review and approval by the Developer Offset Mitigation program manager. Common forms of mitigation will be listed in the City’s Developer Offset Mitigation Guidelines and may include, but will not be limited to:


a)                     Building removal;


b)                     Footing drain disconnection;


c)                     Plumbing fixture retrofits;


d)                     Pool filter backwash retrofits.


e)                     Sanitary sewer system inflow or infiltration removal.


(9)                     A development has the option to make a payment to the City in lieu of performing sanitary flow mitigation. Payment will be used by the City to fund sanitary sewer wet weather capacity improvement projects.


a)                     The payment amount will be per a gallon per minute of new peak sanitary flow being added to the system, will be established by city council, and may be revised by city council.


b)                     For developments subject to site plan approval, payment must be received prior to the City’s issuance of any certificate of occupancy.


c)                     For governmental facilities subject to this section, payment must be received by the City prior to the set of the first water meter.


(10)                     If a township contributes sanitary flow into the City’s sanitary sewer system at a point where adequate transport capacity within the city has not been purchased and/or constructed by the township, the township must adopt an ordinance or approve and implement a policy equivalent to the offset-mitigation requirements of this Section 2:42.5 to apply to developments and sanitary sewer connections within the areas that contribute that flow. If the mitigation takes place within the city, city staff will verify the mitigation work, but will not provide compliance tracking. The township will be responsible for coordinating a compliance tracking and reporting procedure acceptable to the city to document that the mitigation work was completed.


(11)                     New sanitary sewer system connections for single or two family homes currently using on-site sewage disposal systems shall be exempt from offset-mitigation requirements.

2:42.6 - Annexing properties; disconnection of footing drains from sanitary sewer.


Properties annexing into the city must disconnect on-site footing drains from the sanitary sewer within 90 days after notice from the City.


Section 2. That this ordinance shall take effect on the tenth day following legal publication.