RAINWATER HARVESTING – WHAT STANDS IN ITS WAY?

With water shortages and the longer-term security of water supply being a serious concern for South Africans, one would think that every business, school and home would have a rainwater harvesting system. Justin Kretzmar, Sales Engineer at Rocla and Technicrete, explains why this is sometimes not the case.

“When constructing new commercial, residential and public buildings, a rainwater harvesting system is one of the last elements to install. At this stage, many projects are either over budget or have run out of money completely, and so the idea is often abandoned or a cheaper, shorter life span option adopted.

“Another reason is that rainwater harvesting systems are still being underquoted in South Africa at tender phase. If the requirement is for 50,000 litres of harvesting, we often note at a later stage that 10 of 5,000 litre plastic, above ground, storage tanks have been used as the pricing guideline. Consideration might not have been given to the site plans and hence an understanding as to where the engineers envisaged these tanks to be placed. On sites where the tanks are designed to be placed below ground, due to durability, overall size and/or space requirements, the plastic guideline pricing can be out by a factor of 10 or even 20 once you include below ground installation work.

Mr Kretzmar maintains that rainwater harvesting is also sometimes viewed as a nice-to-have as opposed to a necessity and hence gets dropped at the final stages due to updated overall cost implications.

“There is little financial incentive, and no legislation that forbids the use of potable water when non potable water could be used. However, with parts of our country either suffering from drought, or experiencing water shortages and restrictions, there has been an increased interest in residential rainwater harvesting. Unfortunately, many people only consider rainwater harvesting in times of drought, which of course, is too late. There has to be rain to fill the tanks and we hence, need to embrace a longer-term philosophy.” says Kretzmar.

Product offering

Technicrete and Rocla, part of the Infrastructure Specialist Group, both offer different water harvesting friendly options that can be used independently or combined for a holistic solution. These include permeable paving solutions to capture surface water and below ground concrete collection tank systems for roof water capture.

Rocla offers two concrete rainwater harvesting solutions that are both installed underground:

  • A (smaller) modular system, made up of 6,000 litre units that can accommodate storage requirements from about 24KL up to hundreds of thousands of litres.
  • A (larger) modular made up of 60KL rectangular tanks. These are more cost effective than the smaller modular option but installations must be increments of 60,000 litres.

Below ground concrete tanks are considerably more hygienic when compared to above ground plastic alternatives due to the naturally cool and dark environment where most micro-organisms cannot survive. Being underground and out of site, vandalism is reduced and as they are not exposed to sunlight, problems associated with UV reducing overall lifespan are alleviated. 

Technicrete’s Aqua range of permeable paving products subscribe to a methodology whereby vertical ‘slots’ between adjacent pavers provide drainage channels allowing storm water to flow from surface, through the paving and bedding layers, into suitably designed stone layer works below.  This stone layer becomes the storage ‘tank’ with the captured water replacing air cavities between adjacent stones. It is interesting to note that these air cavities can be up to 40% of the overall volume of this layer, or 40 litres of water stored per square meter in every 100mm thick stone layer. Whilst permeable paving is most frequently used as a water attenuation facility, it can also be used for rainwater harvesting, by placing an impervious membrane at the base of the layer works, capturing the water instead of infiltrating it. This water would typically be used for reuse in greywater and irrigation systems. 

Potential problems

“While permeable paving technology has been around for well over 40 years (locally for over 20 years), some engineers are still hesitant to make use of this option. Permeable paving can and does fail when it has been designed or installed incorrectly or has been placed in unsuitable locations,” says Kretzmar.

For instance, one should probably not use permeable paving in places where there is a lot of fine dust and pollution that can be expected to blow over an area on a regular basis. As such, there is justifiable concern about the long-term clogging of permeable paving. With the finest material at the top, grading to larger stones at the bottom, clogging occurs when tiny particles being transported by storm water get caught by the smaller gravel at the top of the pavement layers and hence reduce the filtration capacity through the paving layer. This reduces the filtration capacity through the paving layer and the functionality of permeable paving.

Other causes of failure include design and installation shortcomings where the permeable layer must contend with more surface water than it can physically process. One should ensure there is a limit to a ratio of 2:1 ratio of impermeable to permeable layering. Furthermore, contractors often do not follow correct installation instructions with regards to contamination and compaction.

“Maintenance and cleaning of permeable paving is therefore very important. Maintenance should include annual sweeping of the paved area, prior to the rainy season as this will remove most of the silt that has settled onto the area over the dry season – therefore avoiding contamination at the top grit layer.  Typical cleaning regimens should be carried out every five to ten years or as and when as system is no longer functioning as required. A high pressure spray will loosen the upper 25mm of clogged, polluted gravel/grit, followed by a high strength vacuum to remove this material. The fine grit layer between pavers must then be reinstated with new, clean and washed material.” adds Kretzmar.

Kretzmar concludes that rainwater harvesting tanks and permeable paving have been used very successfully internationally and moderately so in South Africa, “However, both systems have been very successful in other countries, especially where the requirement has been driven by local legislation and municipalities.”

Source: Water & Sanitation Africa Mar/April 2021

ROCLA SUPPLIES 19KM’S OF HDPE PIPES FOR POLOKWANE WATER TREATMENT PLANT

Waste water treatment plants play a crucial role in the removal of contaminants from wastewater and sewage in order for its conversion into an effluent that can be returned to the water cycle in an environmentally friendly way or to be reclaimed for other purposes. It is a critical process in the supply of safe water to local communities.

Rocla’s HDPE vertical cast pipes were specified for two phases of the Polokwane Waste Water Treatment Project due to the quality of the pipes and the technical support Rocla provides. The project commenced in 2018 and was completed at the end of December 2020.

The project, which was subdivided into three phases, is based in the Seshego area in Polokwane. It was initiated to upgrade existing sewerage system, to meet the increased requirements of the Seshego local communities. Each phase of the project had a separate starting point with a common joining at a single point.

Rocla, Regional Sales Manager, Andrew Kruger said “The project was commissioned by the Polokwane Municipality to upgrade a now outdated sewerage system which no longer met the local community’s requirements in the Seshego area of Polokwane. We worked closely with site contractor Safcrete Construction so that the quality of the pipes would be to the standard required and delivery scheduling would be as seamless as possible”.

“The pipes were 2.5m Silica Rolling Joint Pipe, comprising a 3mm sacrificial layer. Five sizes of pipe were required, namely 900mm, 1000mm, 1200mm, 1400mm and 1500mm, which if placed end-to-end, the HDPE piping would be over 19 km’s in length. The placement of each pipe required the insertion of a rubber ring and the welding of a ‘capping strip’ on the inside of each individual joint to ensure proper sealant” said Kruger.

Rocla’s HDPE lining offers water and sewer projects advantages such as a surface smoother than concrete, enabling smaller internal diameter piping to be utilised. The long-term pullout strength of the lining anchors is able to cope with a ground water pressure in excess of 10m.

Mr Thaver, Safcrete Construction’s Contracts Manager commented that he had worked with Rocla and their engineers on many projects over the years and had always been impressed with the quality of the end product supplied. “The Rocla HDPE pipes were specified for this project because they offer the best solution to waste and stormwater plant and projects of this nature. Their attention to customer requirements, in this case, an exceptionally challenging delivery schedule, is also a feather in their cap”.

Kruger added “In order for our Polokwane factory to manufacture the various sizes of pipes and the required quantities, Rocla Polokwane underwent an overhaul in terms of the manufacturing sections needed to accommodate the upgraded equipment. We also made use of special Vertical Cast (VC) moulds which were required for use with the insertion of the sacrificial layer within the pipes. It was these changes that enabled us to meet the quantities of HDPE pipes required for the Polokwane Waste Water Treatment Plant projects as they enabled us to increase our production schedules and deliver to site timeously”.

Concrete pipe with a cast in HDPE lining has all the advantages of a strong rigid pipe that keeps its shape as well as those of a plastic pipe that is inert to acid attack.  It is the best pipe for large diameter gravity pipelines in almost any condition. Standard HDPE lining is light green and 3mm thick. Different colours and thicknesses can be supplied.

The range of products that Rocla offers in terms of sewer reticulation are:

a) Reinforced concrete pipes with a HDPE lining.

b) Reinforced concrete pipes with a sacrificial layer.

c)  Reinforced concrete pipes with Xypex BIO-SAN C500 (300mm – 600mm diameter pipes.

ROCLA MANUFACTURES LARGEST CUSTOM DESIGNED JACKING CULVERTS IN SOUTH AFRICA

When the local municipality of Tshwane required 3m x 3m custom-made jacking box culverts for a service delivery project at Iscor Heights, in Pretoria West, the only company in South Africa who was able to design and manufacture culverts to such large specifications was Rocla. The culverts were manufactured with an in-the-wall joint that can be sealed with a rubber ring if required.

The project, which required 90 large sized culverts to create two 50m long under-road tunnels 6m below the road surface in order to provide new water services to the area, commenced in January 2020.

Brendan van Vuuren, Sales Consultant for Rocla said “We have been involved with the Iscor Heights project since the inception of the tender, and we worked closely with Esor Ltd, one of South Africa’s benchmark and civil engineering groups, who was the project’s sub-contractor, in order to ensure that their specifications for these very large jacking culverts were met. The largest jacking pipe Rocla had manufactured in the past was a 3000mm x 2500mm, which was too small for the project. After all of the specifications were finalised, the designing process began, which included manufacturing the mould for this specially sized culvert”.

Esor Ltd, Director, Len Nel commented “We have worked with Rocla on various projects over the years, so we knew that these large jacking culverts would have to be specifically designed and manufactured, and that Rocla was the only company who had that kind of creative capability”.

“After many meetings to discuss the design and verify the technical requirements of the jacking culverts to ensure that the final product would meet the loading requirements, the final culvert weighed in at an excess of 10 tons per product – a major design and manufacturing coup for Rocla” Nel added.

The timeframe from approved product specification and design to mould completion was only 16 weeks for the 90 culverts.

Due to the enormous size of the culverts, the delivery to site required an abnormal load permit and they were offloaded into the pit at site with a Side boom Crane.

“Rocla is extremely proud to have been involved with this unique project. It tested our design team’s expertise and our manufacturing processes to the limit, but showed that no project is too big for Rocla to collaborate on. It will certainly become one of Rocla’s historical milestones” concluded van Vuuren.

Rocla manufactures various culvert designs and culvert base slabs, along with stormwater pipes and other infrastructure products such as HDPE and pressure lined sewage pipes, concrete poles, manholes, bus shelters, sanitation units and concrete cabins.

12 METRE FULLY INSULATED CONTAINERISED OPEN PLAN OFFICE UNIT AND PAVING DONATED TO MPUMULANGA PRIMARY SCHOOL BY ROCLA AND TECHNICRETE

The Infrastructure Specialist Group (ISG), which comprises Technicrete and Rocla has donated a 12 metre fully insulated containerised open plan office unit as well as paving to the Sifunindlela Primary School, based at Kabokweni in Mpumalanga Province. The office unit will be used by the school’s principal, Mr Ndhlovu and some of the school’s administration staff.

The 1 x 12.22 m x 2.44 m x 2.59 m container is fully insulated with 40mm polystyrene, has four aluminium sliding windows (900 mm x 1200 mm) – complete with fitted burglar bars – and a steel panel entrance door with a lock set.

Principal Ndhlovu explained “Sifunindlela Primary School has never had offices for staff, staff have in the past, met for meetings in passages or under the Lapa. Now, with the donation of this containerised office unit we have privacy for meetings with staff and visitors. It enables us to house school records and confidential correspondence properly. We are very grateful to Rocla and Technicrete for these donations. It creates a proper working environment for myself and members of my team, making a difference to how we work and giving us all a sense of pride in the school we are managing”.

“In 2019 ISG donated 16 sanitation units manufactured by Rocla to the Sifunindlela Primary School, because we believe that proper sanitation in schools provides human dignity. It was during this project that we became aware of the fact that Principal Ndhlovu had no dedicated office space not only for himself but also for some of his administrative staff “commented ISG Group Marketing and Communications Manager, Malebusa Sebatane.

“ISG decided to donate this fully insulated open plan office space to the school to assist in providing a secure and stable office environment for Principal Ndhlovu to carry out his duties” said Sebatane, adding

“Technicrete has also donated 2,574 m2   of our Double Zig Zag 60 mm grey paving and financed a local contractor to clear the ground work and install the paving around the school and new office”.

“In the past the primary school children have been subjected to high levels of dust from the dirt tracks around the premises, which the Technicrete paving will help reduce if not eliminate completely. Installation is from the entrance to the primary school, around the art class and around the netball fields. The paving will improve the health and wellbeing of these young children in a big way in addition to creating safer and more durable walkways” concluded Principal Ndhlovu.

The containerised open plan office space is fitted with a 220V Distribution Board, 4 x 4 ft vapor proof lights, 4 x double switch plugs, a single light switch, 1 x 1800 BTU type air conditioner. The unit has rubberised flooring with black pigmentation. The exterior of the unit has been wire brushed, primed and painted in A/D white enamel.

“Education in South Africa is of paramount importance, if ISG, in some way, can make a difference by providing a suitable environment for educators to perform their duties in and safe and hygienic sanitation units for learners like those we have met at Sifunindlela Primary School, then we believe we have a played a part in the general upliftment of their environment” concluded Sebatane.

EFFECTIVE SEWERAGE SYSTEMS FOR INFRASTRUCTURE DEVELOPMENT AND MAINTENANCE

Effective sewerage systems are an essential element of infrastructure planning, development and maintenance. They ensure that communities live in hygienic conditions through the collection, conveyance, treatment and disposal of wastewater in a non-hazardous manner to people and the environment. A critical function of sewerage systems is to prevent water-borne diseases from becoming active.

The success of such systems is dependent on the design of the system, good quality materials and products, good installation and construction practice and continuous monitoring and maintenance to ensure their effectiveness is not compromised during their service life.

Rocla, a leading manufacturer of precast concrete products is an ISO 9001(Quality Management System) certified company and manufactures sewerage system products carrying the CMACS Mark of Approval.

The range of products that Rocla offers in terms of sewer reticulation are:

  • Reinforced concrete pipes with HDPE lining – The HDPE lined concrete pipe offers the advantages of a conventional concrete pipe as well as a plastic pipe in that it maintains its shape under load and is inert to acid attack. They are an ideal product for large diameter gravity pipelines in almost any condition. The standard HDPE lining is light green and 3mm thick. A HDPE capping strip is welded over the joints after installation to protect the exposed concrete at the joints from corrosive products. These pipes are available from 750mm diameter pipes. 
  • Reinforced concrete pipes with a sacrificial layer – The company manufactures the following types of reinforced concrete pipes with sacrificial layer: The host pipe is manufactured from ordinary Portland cement (OPC) concrete with either dolomitic or siliceous aggregate and the sacrificial layer is manufactured with dolomitic aggregate in an OPC concrete or calcium aluminate cement (CAC) concrete.
  • Reinforced concrete pipes with Xypex BIO-SAN C500 – Concrete pipes with Xypex BIO-SAN C500 are offered for 300mm to 600 mm diameter pipes. Xypex BIO-SAN C500 is a uniquely designed
  • admixture for integral, long term protection of concrete in harsh sewerage conditions with high levels of H2S that causes microbial induced corrosion in pipelines.

Infrastructure Accessories

Supporting precast concrete sewerage accessories include:

  • Pipes with access hole
  • Bends – custom made bends of up to 30 degree can be supplied
  • Manholes – HDPE lined manhole chambers, reducer slabs and cover slabs

Rocla products have been utilised in the Waterkloof Quarry and the Nellmapius Ext 22 housing project both in Pretoria, as well as for the Polokwane Eastern Ring Road and rehabilitation of the D528 in George’s Valley and the Great North Plaza in Limpopo. Projects in Cape Town and Mozambique have also sourced the expertise that Rocla can offer when it comes to infrastructure specialist requirements.

ROCLA AND TECHNICRETE OPEN FOR BUSINESS

Rocla and Technicrete, part of the Infrastructure Specialist Group (ISG), re-open for business after the initial level 5 COVID-19 situation in South Africa.

“We are pleased to announce that our manufacturing plants are running although at a reduced capacity, and that our sales representatives are available to assist customers with technical and product advice across the entire spectrum of our standard and customer specified offerings” said Malebusa Sebatane, Marketing and Communications Manager for ISG.

Rocla, an iconic South African brand, is one of the leading suppliers of precast concrete products for infrastructure, including pipes, culverts, manholes, poles and various other related products. Their products are regularly specified for public works infrastructure projects as well as commissioned by the private sector for commercial developments.

Technicrete has one of the most comprehensive range of concrete products in South Africa. Technicrete manufactures and supplies paving, erosion and drainage products, masonry and mining products.

Both Rocla and Technicrete are members of the Concrete Manufacturers Association of South Africa.

“All of our factories and staff are COVID-19 compliant, and work to a high standard of diligence and with stringent sanitising and personal protective equipment in place throughout its operations” concluded Sebatane.

All Technicrete enquiries should be directed to the sales team contacts stipulated on http://www.technicrete.co.za/physical-locations/

All Rocla enquiries should be directed similarly to contacts stipulated on: http://www.rocla.co.za/physical-locations/

REHABILITATION OF PARKTOWN STORMWATER SYSTEM

Concrete stormwater pipes have a long lifespan but it is not infinite. Ageing infrastructure and pipe erosion and corrosion are all factors that initiate the rehabilitation of stormwater piping systems. Rocla, known for its technical experience and product application analysis, was selected to design and manufacture skew culverts for the Parktown Emergency Stormwater Project in Johannesburg..

“An assessment of the relevant technical and practical factors is key to the successful design of any element of stormwater rehabilitation projects” said Civil Engineer, Muhammad Bodhania, based at Rocla’s Roodepoort offices. “There were numerous technological challenges presenting on the Parktown project, so meetings were held between PGN Civils, the site engineer and ourselves in order to ascertain the most appropriate design and product to be used for the successful installation of the replacement skew culverts and bases” said Bodhania.

“The existing stormwater channel at Parktown is a channel with a unique curvature. This is why Rocla had to design and manufacture specialised skew culverts that could be installed into this channel. We took the basic design of a standard Rocla culvert but manufactured it at an angle to create a curvature that would fit properly into the existing curved channel. We are proud to say that despite the challenges of the required angle design we met the technical specifications completely”.

Rocla supplied 42 straight 2500 x 2500 SAR Culverts, 19 skew culverts and associated bases.

“We have worked with engineers at PGN Civils and WBHO previously on specialised projects and they know of our technical, design and manufacturing capabilities, hence Rocla being chosen to assess and resolve the technological challenges of a very unique project” concluded Bodhania.

The Parktown Emergency Stormwater Rehabilitation Project started in February 2019 and is due for completion in February 2020.

ROCLA DONATES SANITATION UNITS TO MPUMALANGA PRIMARY SCHOOL

“No school should be without proper functioning and clean sanitation units. It’s called human dignity” said Albert Weber, Chief Executive Officer of the Infrastructure Specialist Group (ISG) when he recently handed over 16 Rocla precast concrete sanitation units to the Sifunindlela Primary School, based at Kabokweni in Mpumalanga Province.

“At ISG, our Corporate Social Initiative focuses on early learning development projects. At Sifunindlela Primary School, we saw a need for hygienic and safe sanitation units for their very young learners, and we knew we could assist through the expertise that Rocla has in this sector. Our belief that functional ablution facilities should be provided for young learners attending educational establishments, stems from our belief in the right to basic human dignity. We at ISG and Rocla are proud to have supplied the 16 dignified and safe sanitation units” Weber said.

 “We contracted Enviromould Product Solutions for the installation of the toilets, they supplied amenities for upstream water and downstream sewer management. The finished product comprised of two sets of toilet for both girls and boys. The seats supplied, include for a built in baby-seat to accommodate both pre-schoolers and the much older children in primary school. These sanitation units are safe, hygienic and fully functional and replace previously dangerous Pit toilet installations” commented Andre Labuschagne, Product Development Manager at Rocla. He added “The sanitation unit itself is a cost-efficient unit. There is no need for any educational establishment not to have units such as these installed for their learners and their staff “.

Enviromould supplied all associated sanitation unit fittings such as stop cocks, water connection fittings, infiltrator soak away chambers, sewer pipes, water troughs and vent valves as well as conducting the excavation, installation and backfilling of the septic tank  as well as the installation of a 5000 litre water tank on a raised platform to gravitationally feed the toilet cisterns.