Fair Share Contribution Calculation
Subdivisions and commercial developments are required to provide paved access to their developments. However, the St. Lucie County Land Development Code states that small traffic generators (developments that generate less than 100 vehicle trips per day) may request that only a contribution towards the paving of an unimproved roadway be required.
This Technical Memorandum is intended to address the protocol of the requirements of the Chapter 7.05.07 -Fair Share Contribution for small traffic generators. This procedure has changed over time and will continue to do so.
The Fair Share Contribution is calculated in two parts. First, the overall cost of paving a roadway to County standards is calculated then proportionate amount of the total cost is evaluated based upon the specific site plan.
The paving construction is evaluated assuming full County standards are implemented. These standards dictate that all metal pipe culverts beneath asphalt are replaced with reinforced concrete pipe (rep). Canal crossings must also be upgraded to rep and cast-in-place headwalls. Guardrail must be installed along canals that will pose a hazard to drivers that will invariably be traveling at higher speeds. Road rights-of-way must be acquired to meet the County standard right-of-way widths (70 feet for open drainage designs). Unit prices for work items must be comparable to those received in our own bidding. Right-of-way acquisitions must utilize 120% of the current property appraiser values or a current appraisal acceptable to St. Lucie County. The second step in the process is for the proportionate amount of the total figure to be evaluated by analyzing three methodologies: vehicle trips, driveways, and road frontage. Each of these will be discussed further.
Vehicle trips are calculated by using the Institute of Transportation Engineering (ITE) formulas. ITE trip generation formulas have been developed for a number of residential and commercial development models and are the industry-accepted standards. It is important to note that the existing zoning of properties is used to evaluate potential development and not future land use classification. The ratio of the site's trips divided by the total trips generated by all properties along the roadway is multiplied by the construction cost to determine the proportionate amount.
In a similar fashion, existing zoning is also used to evaluate the total number of driveways a property may eventually possess at maximum development. The site's total driveways divided by all of the potential driveways along the roadway is the multiplier in this case.
Finally, road frontage is self-explanatory. It is important to remember however that a property generally only fronts along half of a road. In instances where this is not the case, both sides of the right-of-way must be included in the cost calculation. The development total roadway frontage measurement divided by the total length (of both sides of the roadway) is the multiplier in the road frontage case.
All three of these methods are evaluated. Often times the dollar values from each calculation are within a reasonable range. In those cases, the most appropriate methodology is selected and the value derived is identified as the Fair Share Contribution. Sometimes though, the evaluation will yield widely varying values. Judgment must be used in selecting the best methodology. In cases where the developer's consultant and County staff cannot agree, the average of all three may be utilized. In the end though, it is the County Engineer's decision on what figure is presented to the Board.
Following is an example of a Fair Share Contribution calculation is provided. (Design example to follow.)
