NPWS wished to remove vegetation and debris from the ‘Outer defensive ditch’ located at the Middle Head Military Fortifications within Sydney Harbour National Park. The fortifications are listed on the NSW State Heritage Register and recognised as the most complete and representative complex of military fortifications in NSW. MTS Heritage was commissioned to prepare a Statement of Heritage Impact (SOHI) report to support a S.60 Application to Heritage NSW to undertake the restoration works.

Preparation of the SoHI involved a comprehensive literature review. This review confirmed that the defensive ditch, associated defensive position, and nearby sandstone wall were constructed as part of the fortifications at Middle Head in the 1880s, during a period of transition when the colonial military forces expanded and became more unified. The defensive ditch and position were designed to be open structures, built to deter enemy troops from breaching the complex and to allow for surveillance. Aerial imagery confirmed that vegetation within the ditch and the defensive position has only encroached on the elements since the 1950s. Given its open nature and late vegetation growth, the historical archaeological potential of the ditch was assessed to be low.

Due to the considered and careful methods proposed by NPWS, it was concluded that the proposed removal of vegetation, debris and slope wash from the defensive ditch was unlikely to impact on any heritage fabric or the broader heritage significance of the military complex. By removing the vegetation, the ditch would be restored to its original open state. Visitors to the National Park would be able to appreciate the views from the headland and the immense scale and labour required to construct and defend the nearby fortifications. This would result in a positive impact on the heritage values of the defensive ditch and broader military complex.

Following the issue of a S.60 Approval, MTS Heritage recommended a heritage induction for contractors and photographic archival recording prior to, during and following the completion of works.