10/2019 – Standing Strong: Herolds Bay Sea Wall
Seashore protection with Terraforce
Herolds Bay is a small, quaint seaside village in the southern Cape Province. It is known for its sheltered location and idyllic beach, that occasionally comes under attack by the sea in winter. During these months, the homes built closely to the beach need protecting from the waves reaching all the way up their front doors, causing flooding and damage.
The former retaining structures prior to the Terraforce retaining wall installation in 2004, were structurally ineffective and not aesthetically acceptable. The client, George Municipality, therefore instructed the construction of an improved beach protection wall that would satisfy both structural and aesthetic requirements.
Project team
Engineers: Tuiniqua Consulting Engineers, George Office
Contractor: New Heights
Terraforce licensed block manufacturer: Mobicast
The upgraded and improved wall in 2019
Aesthetic but durable sea barrier
Says Paul Goedhart, Pr Eng, Tuiniqua Consulting Engineers, who conceptualised the new wall in 2004: “The old Herolds Bay beach protection wall, was up to that point a combination of various materials and construction techniques, was frequently damaged during winter storms and the Municipality wanted a new uniform wall between the beach and the road which would withstand the sea forces but would also provide an accessible and aesthetic barrier. To meet these requirements a stepped reinforced Terraforce wall was designed. The wall was founded on the underlying rock since the level of the beach sand varies due to the wave action. In so far this was possible the old wall structure was left in place.
“Where the depth of the rock level was unpractical for normal excavation the wall was built on a reinforced concrete strip footing which was founded as deep as practically possible. A reinforcement fabric was used to anchor the wall to the compacted cement stabilised backfill material behind the wall and enough drainage was provided to reduce hydrostatic pressures. The top of the wall was finished off with an in-situ concrete coping.”
Construction of the new wall was started in April 2004 and was completed in October of the same year. During that time the team was challenged by high sea levels and high-water table.
13 500 custom-made Terraforce blocks
Goedhart explains why the Terraforce retaining wall system was chosen: “Terraforce L13 blocks were chosen due to the substantial constructed mass that they offer, and 13,500 units were made with a custom-made concrete mixture – 30 MPa with a minimum of 400 kg cement per m³ of concrete – by Mobicast, Southern Cape Terraforce licensed manufacturer. The stepped wall creates an accessible interface between the beach and the roads/lawns. The blocks could also be easily secured together with reinforced concrete and the transition to ramps and stairs was easy to achieve.”
In 2008 the Municipality commissioned some upgrades and extensions to further strengthen the wall to ensure that it would weather all storms and it is now standing strong for 14 Years!
Withstanding the storms…
Project team
Engineers: Tuiniqua Consulting Engineers, George Office
Contractor: New Heights
Licensed Terraforce block manufacturer: Mobicast