March 23, 2010 Planning Commission - Parking Maximums

On March 23 at 7:30pm, Planning Commission will continue their discussion on LID. This month, staff are following up on questions and issues raised by Commission at the last meeting about parking maximum standards.

Cities frequently have minimum parking standards for commercial and office uses, to ensure that sufficient parking is provided for each new use and avoid overflow parking in nearby neighborhoods. The problem with minimum parking standards is that they are often exceeded by 30-50% (Schueler, 1995), leaving large expanses of parking in commercial areas which is infrequently used. These "extra" spaces may only be used during peak times, such as the holidays. All of those underutilized parking stalls mean that there are large expanses of impervious surface (asphalt and concrete), which creates stormwater runoff that pollutes the Puget Sound.

In response to the large, underutilized parking areas, many jurisdictions set parking maximum standards to cap the number of spaces that can be provided for each new use. Parking maximum standards are not very common, but are beginning to be used more and more.

Planning Commission will discuss the parking maximum standard issue at their regular meeting this month. For more information and to get a copy of Planning Commission materials, please see the "Events" sidebar on this blog.

Impervious Surfaces, Streets, and Parking Facilities

Hard surfaces, also called “impervious surfaces,” generate stormwater runoff. This stormwater has negative environmental impacts because it channels pollution into the Puget Sound. In addition, costly public infrastructure is required to treat this stormwater. Reducing the amount of impervious surface can reduce the amount of stormwater, and therefore, pollution going into the Puget Sound.

The following policy issues are currently being discussed by the Planning Commission. The City welcomes your comments and thoughts on these issues. You can post your comments on these topics by clicking on the “comments” hyperlink below.

Limits on Impervious Surface
The existing code does not place limits on the amount of impervious surface. This means that new developments can, in theory, pave over most of the project site.   If the City places limits on the amount of impervious surface in new developments, developers will be required to use pervious pavements, which absorb stormwater or could leave part of their property undeveloped called "native vegetation areas." Private property owners would be required to maintain pervious pavements and native vegetation areas.   

Policy question: Should the City place limits on the amount of impervious surface in new developments? Should these limits be voluntary, incentive-based, or mandatory?

LID Streets
Streets make up the largest portion of impervious surface in urban areas. Local streets comprise 60-80% of all road surfaces alone. As a result, streets create higher stormwater volumes and pollutants than any other source. The LID discussion on how to make streets more stormwater-friendly is focused on the following factors: road layout, road width, and road surface.

Maintenance is the central issue with LID streets. City staff anticipate that pervious pavements used in LID streets will require more maintenance than streets currently do. In addition, rain gardens (bioretnetion facilities), which collect and treat stormwater, will also require more maintenance. The rain gardens will need to be maintained either by the City or by property owners.

Policy Question: Should LID streets be voluntary, incentive-based, or mandatory in new developments? Positive environmental impacts increase when LID streets become mandatory. However maintenance costs for the City or property owners also increase.

LID Parking Facilities
In terms of the total amount of impervious surface in urban areas, commercial parking areas are second only to streets. The LID discussion focuses on reducing the amount of impervious surface in parking lots by addressing the following three issues: pervious surfaces, rain gardens, and setting parking maximums.

We can expect reduced environmental impacts when LID (pervious surfaces and rain gardens) are installed in new parking lots. Since commercial parking lots are maintained by tenants or owners, staff does not expect an increase in City costs by requiring LID parking facilities. There may be a small increase in maintenance costs to property owners, if pervious pavements and raingardens are required in commercial parking lots. Although, there would also be some cost savings to property owners since the on-site stormwater pond would be smaller.

Most cities use parking minimum requirements as a way of ensuring that there is enough parking for each use. Over time, studies have shown that a large portion of commercial parking facilities, like the kind you would see in shopping centers, go unused. That is to say, at least 20% of the spaces are vacant most of the time, except when stores are busy, such as during the holidays. Because there is so much unused parking, many cities now set a limit on the number of parking spaces non-residential uses can have. Minimum parking requirements may stay in place, so that there is a range of parking requirements for each use (a minimum AND a maximum). This reduces the amount of impervious surface in urban areas, and therefore stormwater runoff. It also makes more property available for other uses, such as building area and landscaping.

Given these facts, there are two policy questions that need to be answered: (1) “Should LID parking facilities be voluntary, incentive-based, or mandatory? and (2) Should the City consider setting parking maximums for non-residential uses, i.e. putting a limit on the number of parking spaces for commercial, industrial, and office uses?

Project Description

Thanks for viewing the City of Oak Harbor's LID blog. This post gives a brief background of the project, information on events happening in Oak Harbor related to LID, informational resources (links to other websites and reports), and pictures of LID applications in Oak Harbor and elsewhere.

The host of this blog is Ethan Spoo, Senior Planner with the City of Oak Harbor. I am also the City's project manager for the LID code update. Feel free to tell me how I can make this blog better or ask me questions about LID. And most of all, enjoy the blog!

Late in 2007, the City applied to receive technical assistance from the Puget Sound Partnership (PSP) to help integrate LID standards into the Code. After being selected as one of the 13 Puget Sound jurisdictions to receive assistance, Oak Harbor met with PSP’s consultant, AHBL, several times during 2008. Coupeville was also selected. AHBL helped the City identify areas where LID standards could be integrated into the Code and drafted proposed LID language. The sections of the Code reviewed by AHBL were: (1) Chapter 11.17 – Street Design Standards (2) Title 12 – Stormwater (3) Title 19 – Zoning (4) Title 21 – Subdivisions and, (5) Engineering Standard Detail

Staff have reviewed the draft code and have identified policy issues which need to be considered by the Planning Comission before the code is released for public review. The policy issues and the discussion around them will be a central part of this blog.

Examples of LID

Residential Rain Garden

This is an example of a rain garden which has been built into someone's front yard.

Pacific Crest Bio-retention Area

This is an example of a bio-retention area in the Pacific Crest Development in Oak Harbor. The bioretention area allows stormwater from the adjacent road to infiltrate into the soil thereby filtering pollutants out of the stormwater.

Harbor Station Rain Garden

This is an example of a rain garden at the Harbor Station develompent in Oak Harbor. The rain garden filters stormwater from the parking lot.

Island Place Grass Pavers

This picture shows grass pavers at the Island Place development in Oak Harbor. The grass pavers are a hard plastic, honeycomb grid which allows grass to grow between the spaces, but still supports the weight of vehicles.

Bio-retention Area

This is another example of a bio-retention area along a public street.  Stormwater enters the bioretention area via the inlet in the middle of the picture.

How a Bioretention Area Works

A bio retention area also known as a rain garden is a planted depression that allows rainwater runoff from impervious urban areas like roofs, driveways, walkways, and compacted lawn areas the opportunity to be absorbed. This reduces rain runoff by allowing stormwater to soak into the ground (as opposed to flowing into storm drains and surface waters which causes erosion, water pollution, flooding, and diminished groundwater). Rain gardens can cut down on the amount of pollution reaching creeks and streams by up to 30%.

Native plants are recommended for rain gardens because they generally don't require fertilizer and are more tolerant of one’s local climate, soil, and water conditions. The plants — a selection of wetland edge vegetation, such as wildflowers, sedges, rushes, ferns, shrubs and small trees — take up excess water flowing into the rain garden. Water filters through soil layers before entering the groundwater system. Root systems enhance infiltration, moisture redistribution, and diverse microbial populations involved in biofiltration. Also, through the process of transpiration, rain garden plants return water vapor into the atmosphere. A more wide-ranging definition covers all the possible elements that can be used to capture, channel, divert, and make the most of the natural rain and snow that falls on a property. The whole garden can become a rain garden, and all of the individual elements that we deal with in detail are either components of it, or are small-scale rain gardens in themselves. Source: http://en.wikipedia.org/wiki/Rain_garden