CHAPTER 5 - CAPITAL IMPROVEMENT PLAN

This Capital Improvement Plan (CIP) presents the problems, alternatives, and recommendations identified in the study to improve storm drainage in the City of West Jordan. The CIP was developed from the hydrologic models, deficiency analysis, and workshops with City personnel.

PREFERRED DRAINAGE PLAN DEVELOPMENT

Which resolution a deficiency merits is based on what type of deficiency it is. Some deficiencies such as maintenance or replacement have a straightforward linear resolution. Resolving a deficiency related to flooding has more than a singular solution option. Where these deficiencies existed, HAL evaluated possible alternatives and whether it could be resolved with upstream detention and/or required a pipe or inlet improvement. Selection of the preferred alternative for each problem was a process of evaluation and refinement rather than a simple choice between alternatives.

The process of selecting a preferred alternative included:

∙   reviewing the list of storm drainage inadequacies,

∙   brainstorming possible solutions,

∙   screening alternatives based on feasibility and public acceptance,

∙   developing alternatives,

∙   coordinating phasing of other master planned projects (water, sewer, transportation)

∙   comparing cost, function, human safety, and damage prevention, and

∙   selecting the preferred alternative.

Design criteria included:

∙   10-year minimum capacity

∙   100-year capacity where homes may be frequently flooded

∙   100-year capacity on regional detention basins (limited to hydraulic capacity of existing pipe)

∙   100-year capacity for natural drainages as defined in Chapter 2

PRECISION OF COST ESTIMATES

When considering cost estimates, there are several levels or degrees of precision depending on the purpose of the estimate and the percentage of detailed design that has been completed. The following levels of precision are typical:

Type of Estimate      Precision

Master Planning      ±50%

Preliminary Design      ±30%

Final Design or Bid      ±10%

For example, at the master planning level (or conceptual or feasibility design level), if a project is estimated to cost $1,000,000, then the precision or reliability of the cost estimate would typically be expected to range between approximately $500,000 and $1,500,000. While this may seem very imprecise, the purpose of master planning is to develop general sizing, location, cost, and scheduling information on several individual projects that may be designed and constructed over a period of many years. Master planning also typically includes the selection of common design criteria to help ensure uniformity and compatibility among future individual projects. Details such as the exact capacity of individual projects, the level of redundancy, the location of facilities, the alignment and depth of pipelines, the extent of utility conflicts, the cost of land and easements, the construction methodology, the types of equipment and material to be used, the time of construction, interest and inflation rates, permitting requirements, etc., are typically developed during the more detailed levels of design.

At the preliminary or 10% design level, some of the aforementioned information will have been developed. Major design decisions such as the size of facilities, selection of facility sites, pipeline alignments and depths, and the selection of the types of equipment and material to be used during construction will typically have been made. At this level of design the precision of the cost estimate for a $1,000,000 project would typically be expected to range between approximately $700,000 and $1,300,000.

After the project has been completely designed and is ready to bid, all design plans and technical specifications will have been completed and nearly all of the significant details about the project should be known. At this level of design, the precision of the cost estimate for the same $1,000,000 project would typically be expected to range between approximately $900,000 and $1,100,000.

The flows and pipe diameters provided in the following Capital Improvement Plan (CIP) descriptions are approximate and are for planning purposes only. A detailed hydrologic and hydraulic analysis shall be performed during the design process of the projects to identify final design and sizing.

ESTIMATED CONSTRUCTION COSTS

Cost estimates are based on conceptual-level engineering. Unit construction costs were estimated based on construction cost indices (ENR 2022), communication with material suppliers, heavy construction data references (RSMeans 2022), and HAL's experience with similar construction. Engineering cost estimates given in this study should be regarded as conceptual and appropriate for use as a planning guide. Only during final design can a definitive and more accurate estimate be provided. A detailed cost estimate of each alternative is provided in Appendix B.