670 Queen Street, Brisbane, Qld. 4000
Dear Mr. Sam Clements.
As per your request an evaluation for the optimum site for the potential Gold Coast urban development retirement community was carried out. A preliminary design of the earthworks using geo-mapping with a computer model and the optimum arrangement for the urban development are the outcomes of our work. Three areas were evaluated. We recommend that the project be built upon AREA 2. AREA 2 is the least expensive site for the urban development while at the same time meeting the other requirements for earthworks. The AREA 2 site will provide enough land for the retirement community centre, recreation and activities and cover the land costs associated with the construction footprint. Below you will find a summary for the design and the outcomes that led to our recommendation.
The objectives for this project were to develop a preliminary design of the earthworks and prepare a geometric scale model of the site to test the optimum arrangement. The outcomes of the work report that the total estimated cost if the development is done on AREA 2 will be approximately $731,452.25. The total cost is based upon $20,052.25 for earthworks costs and $530,400 for land costs. A table with the breakdown for the cost figures can be found in the report. A figure depicting geometric scale model of an AREA 2 platform is included in the report; the amount of earthworks needed is less than at AREA 1 or AREA 3 due to placing the development site at the most consistently level area, therefore requiring less earthworks.
Please find attached to this letter a Statement of the Objectives and the Report.
Contact us with any questions you may have. Thank you.
STATEMENT OF OBJECTIVES
Type of Development Project: Urban beach front retirement community including a community centre providing recreational activities
Objectives:
Design the community centre earthworks
Design arrangement for the earthworks based on truncated pyramid
Construct a geometric scale model of community centre site
Determine optimum design within the initial budget for platform construction: $150,000
Determine amount of sand needed (Is enough sand on the site or will more sand need to be delivered?)
Determine amount of land needed for the community centre (including earthworks)
Leprechaun Heights Retirement Community Urban Development on the Gold Coast: Optimum Site
Introduction
The proposed development on the southern Gold Coast will provide a retirement centre in an urban area that offers adequate space for recreational activities. The report was prepared using the geophysical engineering aspects of geological mapping, landform types and depths (Day, 2010). The proposed development plan for the necessary earthworks was designed so that the natural landform is fully utilized. Three reasons are significant for taking advantage of the natural landform on the site: decrease the amount of bulk earthworks needed, decrease the need for high retaining walls and finally to decrease costs. The foundation of building is expected to last from 50 to 200 years, residential is about 100 years (Nelson, Chao et al., 2015). Other variables including type of use that need to be taken under consideration for the earthworks are the depth, elevation head depth of active zone, stress and seasonal water fluctuations (Nelson, Chao et al., 2015). For the purposes of this report the data concerning sand for fill needs and development design location for optimum use and lowest costs were the assumed limitations.
Calculations and Results
The general location for the Leprechaun Heights urban retirement community is the Gold Coast at the southern end. A scale model of the earthworks was prepared by producing computer simulation of the area at the site.
FIGURE 1 Scale model OF EARTHWORKS
1:200 sCALE
The north-south axis runs along the long axis (in figure 1 the x-axis) of the geometric earthworks model. The community centre will be constructed at a platform located at 21 m AHD in order to protect the centre from the high wind surges during cyclones Note that the platform is a truncated pyramid. (See fig. 1) The community centre will be built on a rectangular piece of land consisting of a minimum of 40.0 x 40.0 m. The real shape of the geography was simulated by the model in the above figure. Notice in figure 1 that the valley at the center of the model is the only place where fill will be needed in contrast to other areas that require more volumes of fill due to the geographic setting.
The following values were used to calculate the earthworks and land costs at AREA 2. Sand (40,000 m3) is available to use for fill from other earthworks that have taken place nearby. (See table 1) More sand will be required, approximately 12,000 m3. The cost of the extra sand and delivery is approximately $12.50/m3. Therefore the earthwork cost is expected to be about $201,052.25.
The amount of land that will be needed to hold the community centre as well as to cover the plan area (or footprint) is approximately 26,250 m2. The land cost calculated at $20/m2 will amount to about $530,400.
Therefore the total cost amount is estimated to be $731,452.25. Keep in mind that the most cost-friendly area of the available land was chosen by producing the geometric scale model. AREAs 1 and 3 are both expected to need more fill than AREA 2, which will raise the cost accordingly. The empty volume at AREA 1 is 13,201.9 cm3 and the empty volume at AREA 3 is 13,464.8 cm3. Whereas the empty volume for AREA 2 is only 7010.5 cm3 according to the calculations; meaning that AREA 2 is 6191.4 to 6454.3 cm3 less than AREA 1 and AREA 2. Therefore the savings on the earthworks is considerable The earthworks for AREA 2 provide a savings of approximately $645,500 compared to AREA 3 and about $620,000 compared to AREA 1. The savings for the earthworks is lower in AREA 2 while at the same time providing enough land for the centre and for land costs attributed to the construction footprint. AREAs 1 and 3 consist of 13440 m2, but AREA 2 land area is equal to 26,520 m2.
Further concerns
The only disturbance of the site is permitted at the location of the construction for the community centre platform. Evaluation of sea level rise and the susceptibility of the southern Gold Coast to inundation is a common factor engineered in Gold Coast projects. Major engineering factors include ensuring the minimum heights behind the dune systems are high enough and evaluating the erosion susceptibility of the sands (Ingles and Grant, 1975). The determination of the seawall placements and design is done in collaboration with the Department of Environment and Heritage Protection.
CONCLUSIONS
The outcome of the work for the final report demonstrates that the total estimated cost is $731,452.25. The total is based upon $20,052.25 for earthworks costs and $530,400 for land costs. Calculations of the land topology as well as producing a geometric scale model of the AREA 2 platform were done for the report. Both outcomes show that the argument for choosing the urban retirement community at AREA 2 is the best choice. The amount of earthworks needed is less than at AREA 1 or AREA 3 due to placing the development site at the most consistently level area, therefore requiring less earthworks; therefore the costs will be significantly less by approximately $620,000 to $645,000.
REFERENCES
Day, R. (2010). Foundation Engineering Handbook 2/E. USA: McGraw Hill.
Ingles, O.G. and Grant, K. (1975).The Effect of Compaction on Various Properties f Coarse-Grained Sediments. Chapter 6 in Developments in Sedimentology, Vol. 18, NYC: Elsevier. pp. 293-348.
Nelson, J.D., Chao, K.C. (G), Overton, D.D. and Nelson, E.J. (2015). Foundation Engineering for Expansive Soils. Hoboken, NJ: John Wiley & Sons, Inc.
