Isle of Man Ronaldsway Airport

Project summary

Isle of Man Ronaldsway Airport issued a tender for a contractor to engage in an ECI contract for the upgrade and refurbishment of the airport’s ground services and operating surfaces. The scope of the works entailed the resurfacing of the crosswind runway 03-21, the overlay of a portion of taxiway Alpha, the construction of widened starter strips on both ends of runway 08-26 as well as some minor upgrades to other portions of the airfield. New AGL fixtures and fittings were to be installed as appropriate to the pavement works.

Scope of services

A thorough review of the project specification was undertaken, the airport’s likely trafficking requirements, the existing PCN, ground conditions and existing pavement construction make-up. The material requirements for the taxiway and runway elements called for a Stone Mastic Asphalt (SMA) running surface but in reviewing the permissible materials within Defence Estate’s Specification 12, both Hot Rolled Asphalt (HRA) and a Heavy-Duty Macadam (HDM) could be considered as a surface course for the lightly trafficked pavements.

Given the site information and the declared AIP runway/taxiway strengths supplied, as well as pavement cores, the review led to further analysis of the overall inlay or overlay required. Given the early stages of the project and the potential scope for conducting further site investigations at a later stage, a sensitivity analysis was undertaken on CBRs of 6% and 15% to ascertain the most optimistic and pessimistic outcomes.

Scope of works

Sensitivity analysis results

The results showed that for a design aircraft of an A320-200 and a CBR of 6%, some strengthening may have been required to runway 03-21 north of the intersection with 08-26 as well as that portion of taxiway Alpha west of 08-26. However, if long term CBR values were consistent with the likely ground conditions associated with sands and gravels (circa 15%), then an asphaltic inlay in all areas could be sufficient to satisfy the design objectives.

Benefit

The technical evaluation performed at this early stage permitted the tendering contractor to put forward alternative design solutions which had the potential to offer both material and programme savings. In addition, the sensitivity analysis performed allowed quantification of potential ground condition risks that could be encountered based on local testimony at the airport. The pavement investigation information supplied, as well as an uncertain groundwater table, also provided some insight to the nature of additional site investigation data required to finalise the basis of design.