Civil Engineering August 2021 | Vol 29 No 7

10 August 2021 Civil Engineering Env i ronmental Eng i neer i ng T he management of the Vergelegen Wine Estate in Somerset West is very proud of their farm’s heritage and take great care of the environment. At their own cost they have cleared more than 2 000 hectares of alien vegetation to create a fynbos reserve. Following the 2013 storms which flooded the Vergelegen Mediclinic Hospital, the appearance of a small gulley on the wine farm caused concern. From 2017 onwards, this gulley suddenly accelerated in size as the dispersive weathered Cape Granite soils below were exposed and rapidly eroded. Between 2017 and 2018 the gulley increased from 30 m to 400 m long, and from 2 m to 6 m deep. Downstream from the gulley an area of Lourens River fynbos was smothered by the sediment. LEGISLATIVE CHALLENGES Plans to rehabilitate the gulley using cascades of weirs and other measures were prepared in early 2018 and the lengthy environmental approval process was started. An attempt was made to recognise the gulley as a disaster in terms of the NEMA regulations and shorten the approval process, but because the damage began in 2013 this was not allowed. The approval process took close on a year, during which time the gulley grew even longer and deeper. TECHNICAL PROJECT CHALLENGES The first challenge to the project design was the wetland specialist’s requirement to restore the area’s natural water table to as close to its original level as possible. This would ensure that the natural vegetation in the areas adjacent to the gulley would not be negatively impacted by the drying out of the soil. The impli- cation of this was that the floor of the rehabilitated gulley had to be as close to the original ground level as possible, which necessitated the construction of Hans King Pr Eng Director Hans King SRS hans@hanskingsrs.com Innovative rehabilitation of a deep gulley in dispersive soil When a gulley opened up on the Vergelegen Wine Estate, an innovative solution incorporating the soil stabilising properties of natural vegetation was developed. PROJECT DETAILS Client Vergelegen Wines Project design Hans King SRS Construction Martin and East Year of construction 2020/2021 The extent of the erosion in the gulley Gabion packing underway at the site of Weir 1