MEMORANDUM To: From: Date: Re:
Branch Consulting 2000 Bonisteel Blvd. Ann Arbor, MI 48109
Glenn Wynn, Planning Director, Charter Township of Shelby Andrew Broderick, Branch Consulting March 25, 2010 Eco-friendly parking lot ordinance amendments for Shelby Township
This memo recommends an amendment to Shelby Township’s off-street parking layout standards and construction ordinance. In order to meet the township’s vision of making itself a leader in green development compared to its peers, the amendments focus on implementing eco-friendly porous paving standards and calculating parking space maximum ratios. The goal is to meet the township’s objective of reducing the negative effects of stormwater runoff. Amending the parking lot ordinance is recommended as it is a feasible first-step approach to initiate green development practices in the Township. There are several incremental steps to begin implementing the ordinance change. Green Benefits of Reduced Parking Spot Requirements and Porous Pavement The single most effective way to reduce the impact of parking lots is to limit their size.1 Impervious surfaces such as conventional asphalt parking lots and roofs generate a large amount of stormwater runoff that disrupts the hydrological cycle, increases water pollution, and can increase the chance of urban flashfloods. Some commercial land uses such as commercial strip malls are comprised of 90% impervious surface.2 The best way for township planners to limit the size of parking lots is to establish a maximum parking requirement in addition to a minimum. Porous pavement is an alternative material for parking lots that can reduce runoff and cool surfaces. The pavement, which can be asphalt or concrete is an “open-cell” material that allows for the passage of water and air from top to bottom.2 Water filters through the pavement and recharges groundwater sources while diminishing the demands on stormwater management systems such as catchment basins, detention ponds, and culverts. In turn, the natural water system’s rate of recharge is preserved. Drafting a New Ordinance Amendment for Parking Lots in Shelby Township Shelby Township can accomplish the task of limiting stormwater runoff by drafting a twopronged ordinance amendment that introduces a parking space maximum in addition to the established minimum and regulates the amount of impervious surface. The amendment should be based on a feasible calculation of the parking space ratio maximum that is similar to site design code best practice examples such as Ann Arbor’s code (see Table 1). Additionally, the amendment should recommend only porous pavement for limited building types and in strategic areas. For example, parking spaces but not the driving lanes of a parking lot (see Figure 1). Specifically, two sections of the zoning ordinance should be amended. Section 6.02 of the Shelby Township Zoning Ordinance, titled “Minimum Number of OffStreet Parking Spaces,” should be amended as follows: 1
Branch Consulting 2000 Bonisteel Blvd. Ann Arbor, MI 48109
The minimum and maximum* number of off-street parking spaces by type of use shall be determined in accordance with the following schedule.4 Section 6.01, titled “General Parking Requirements,” should add a 13th and 14th standard that read as follows: 13. Porous pavement such as porous asphalt or concrete is to be used for all parking spaces and associated drive lanes if a development exceeds the maximum number allowed by code. 14. All institutional and public recreational building types identified in the Table Inset in Section 6.02 must use porous pavement such as porous asphalt or concrete for the parking spaces but not the drive-lanes of the parking lot in accordance with the following sketch.* For the sake of brevity, however, this memo will refrain from setting a maximum for every building use specified in the code. It does set forth an example parking maximum for retail centers (see Table 2). More analysis is necessary for establishing maximum parking standards for all building uses, and you should consider seeking additional expertise to develop these standards. Costs of the New Ordinance Amendment The proposed ordinance amendments outlined above will require significant staff time as well as money and political capital in order to adopt. For example, it will take a lot of staff time to draft parking lot maximums for all building types in the township and to further delineate where porous pavement will be used. If funding is available, Figure 1: Example photograph of using porous pavers for the parking stalls and using convenconsulting an experienced parking consultant tional asphalt for the drive lanes. may be in your best interest. Eco-friendly park- Source: www.greenbuilding.com ing lot amendments are growing in popularity across the country, so more consultants are experienced with these types of regulation changes. Finally, the proposed amendments will require some political capital as well. It will be challenging for local politicians to change the status quo of conventional parking lot design in the township. However, the parking lot amendments are a great place to ‘plant the seeds’ for low-impact development in Shelby Township. Compared to other stormwater management alternatives such as bioswales or rain gardens, the parking lot amendments are more straightforward, relatively low-tech, and not as expensive or politically challenging. Initial victories in the short term can build momentum for more intense long-range regulation changes down the *Note: bold text indicates new language. Please see Table 2 and Figure 1 in lieu of full schedule and sketch.
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Branch Consulting 2000 Bonisteel Blvd. Ann Arbor, MI 48109
road.
Incremental Steps for Implementation
The feasibility of successfully implementing the proposed parking lot amendments is strong if three things happen before the amendments are introduced: 1. The Township Hall should lead by example by repaving its parking lot with porous pavement. This step will be an illustrative point of the positive effects of porous pavement, and it will help de-mystify how porous pavement actually looks, feels, and functions. 2. The planning director should work with parking lot consultants, civil engineers, and landscape architects to create parking lot maximums and porous pavement specifications that are backed by research. This step will strengthen the case for introducing the amendments to the township council. 3. Developers should be educated about the benefits of porous pavement and they are encouraged to use it. This step would ideally result in the development of some voluntary pilot studies. The steps highlighted above are ways to generate interest and demonstrate the importance of implementing new parking lot regulations. Example Space Requirments (s.f. of floor area) 100,000 200,000 300,000 Code Requirment (s.f./one space) Ann Arbor3
min max
310 265
No. Spots Total Sq Ft 323 97,581 377 114,151
Shelby Township4
current min proposed max
225 200
444 134,444 500 151,250
No. Spots Total Sq Ft No. Spots Total Sq Ft 645 195,161 968 292,742 755 228,302 1,132 342,453 889 268,889 1,333 1000 302,500 1,500
403,333 453,750
* Calculation assumes 90o parking at 302.5 sq ft per space 2
Table 1: Parking Space Ratios for Retail Centers between 30,000 and 300,000 sq. ft. Current Minimum
Proposed Maximum
J. Retail stores or shopping centers, except as otherwise One space for each 200 square One space for each 150 square specified herein, of 30,000 square feet or less feet of floor area. feet of floor area. K. Retail stores or shopping centers, except as otherwise One space for each 225 square One space for each 200 square feet of floor area. feet of floor area. specified herein, greater than 30,000 square feet
Table 2: Proposed Parking Lot Maximum for Retail Centers in Shelby Township, Parts J and K, Table Insert, Section 6.02, Zoning Ordinance, Shelby Township4
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Branch Consulting 2000 Bonisteel Blvd. Ann Arbor, MI 48109 1. Russ, Thomas H. (2009). Site Planning and Design Handbook (2nd ed.). New York: McGraw-Hill. 2. Steiner, F. & Butler, K. (Eds.). (2007). Planning and Urban Design Standards (student edition). Hoboken, NJ: J. Wiley and Sons. 3. Section 5:167. “Required Parking.” (November 2006). Chapter 59: Off-Street Parking. Ann Arbor City Ordinance. 4.Section 6.02. “Minimum Number of Off-Street Parking Spaces Required.” (July 2009). Article 6: OffStreet Parking and Loading Requirements. Zoning Ordinance Charter Township of Shelby, Michigan. Retrieved March 24, 2010 from http://library1.municode.com/default-test/home. htm?infobase=13418&doc_action=whatsnew
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