Title/Name/Summary
Lot Coverage - 3+ Car Driveways & Accessory Structures
History
This is a follow up to the discussion during the June 22, 2009 Development Services Committee regarding swimming pools and lot coverage related to stormwater. During this discussion, staff was asked to investigate how the requirement of side-loaded three (3) car garages (further abbreviated as “3CSLG”) vs. a typical three (3) car front-loaded garage (“3CFLG”) affects lot coverage, in terms of driveway lot coverage.
Staff investigated the actual sizes of constructed driveways for houses with a typical 3CFLG design and a typical 3CSLG design via the plats of survey for various houses in the Brook Hills, Ishnala, Evergreen View, Colette Highlands and Sterling Ridge subdivisions. These plats were used to determine an average driveway square footage for a front-loaded driveway and a side-loaded driveway. These subdivisions were chosen because Brook Hills & Ishnala are areas where three (3) car garages became quite common, and Evergreen View, Colette Highlands and Sterling Ridge are three of the more current residential developments where three (3) car garages are the status quo, but side-load garages were not necessarily a requirement.
The average area of the 3CSLG driveways surveyed from Evergreen View, Sterling Ridge and Colette Highlands is ~1288 square feet. The average area of the 3CFLG driveways surveyed from Brook Hills and Mallard Landings is ~ 950 square feet. Therefore the general average difference between a 3CSLG garage and 3CFLG can be estimated as 338 square feet- quite a large increase when a side-load driveway is required. The lot size in R-3 zoning is 10,000 to 12,000 square feet (minimum = 80 ft. wide by 125 ft. deep = 10,000 square feet) and 338 square feet of driveway area would equate to approximately three percent (3%) additional lot coverage on account of using a 3CSLG garage design.
Additional Lot Coverage Options
Stormwater management/lot coverage is a tenuous subject, and therefore staff has reviewed and considered additional options that could be made available to property owners in order to gain additional lot coverage. In summary, if a homeowner were to provide additional types of stormwater management best practices then they could gain additional percentage(s) of lot coverage. Such best practices would include:
• Porous Pavers* (the true porous brick system similar to the new Police Station parking lot)
• Porous Concrete*
• Porous Asphalt*
• Cisterns
• Rain Gardens
• Bio-swales
• Rain Barrels
*All porous-type systems used for lot coverage crediting would be similar to commercial systems where subsurface stone void storage and an effective underdrain system is used.
Staff feels these extra measures provide an offsetting benefit by offering a storage or treatment of stormwater with their use, and these measures do not place an undue burden on a property like a true detention pond does. Each lot coverage situation and any proposed best management practice system would be reviewed on a case-by-case basis and credit would be given for systems meeting certain design criteria based on known performance and effectiveness. Practicality and reasonable implementation will also be considered. For instance, 14 rain barrels would not be allowed. The maximum allowable lot coverage for any residential property would be capped at 50%, regardless of the number or complexity of the best management systems employed.
Further analysis is required for staff to establish coverage numbers to be associated with the respective management system. For instance, four (4) rain barrels may be equivalent to allowing one percent additional lot coverage; a 10 ft. by 10 ft. (100 square feet) rain garden may allow two (2) percent additional lot coverage; or a 200 gallon cistern serving the property’s sprinkling system may allow three percent additional lot coverage. At this time, more research is needed to establish reasonable equivalencies for the amount of best management practice equating to how much additional percent lot coverage would be granted. It was also noted at the committee meeting that removable items (such as rain barrels or rain gardens) may not be good candidates for credits. Staff plans to return its findings to this committee within a few months.
On July 27, 2009, the Development Services and Planning Committee moved 3-0 to recommend to the Village Board of Trustees approval of a code amendment that will allow an additional 3% lot coverage for three car side-loaded garages.
This is now before the Village Board for consideration.
Recommended Action/Motion
I move to approve of a code amendment that will allow an additional 3% lot coverage for three car side-loaded garages.