- Is mining sea sand for construction a sustainable alternative to mining river sand?
In an attempt to bring sustainability to Sri Lanka’s construction industry, Prime Minister Mahinda Rajapaksa recently requested that the use of sea sand be expedited by beginning processes at the Muthurajawela Sand Yard, an area of coastline that has been designated for sand mining.
The story behind the Muthurajawela Sand Yard
The mining of sea sand for construction and the Muthurajawela Sand Yard is not a new concept. The Muthurajawela Sand Project was launched over 16 years ago, and has pumped over four million cubes of sand each year it was active. Sea sand is pumped to the yard through selected contractors and is stored in open-air sand dunes, inserted into the sand machine, washed, cleaned, selected, and dried. The project also avoids the use of chemicals when washing the sand, by using cold water only. The sea sand in stock now is currently being supplied for the construction of the Central Expressway.
From a state perspective, speeding up the process of sea sand preparation from the Muthurajawela Sand Yard is an alternative to the mining of river sand, which will ultimately serve to prevent damage to our river beds and protect the environment.
The 70-acre sea sand yard has also been the recipient of multiple sustainability awards, which include the Green Label for sand by the Green Building Forum for eco-friendly products. According to the Marketing Division of the sand project, customers buying sea sand from these yards save around Rs. 4,000 per cube of sand.
University of Moratuwa Civil Engineering Senior Prof. Priyan Dias, who has done work relating to the engineering properties of the Muthurajawela Sand Yard, explained that when a study was done in 1999, the mining of river sand was completely unsustainable from an environmental standpoint for a number of reasons; at the same time, offshore dredging of marine sand, or cutter-suction dredging as the process is called, doesn’t affect coastal sand budgets, provided the dredging takes place at a certain distance and depth away from the coast.
In fact, the greater the depth of water where sand is dredged, the less impact there is environmentally on the coastline, especially when dredging takes place beyond the breaker zone. Prof. Dias did note, however, that the actual depth of scraping, or the amount of sand that is dredged, should ideally be limited to a layer of 0.5 m.
Sea sand’s capability as a river sand alternative has also been further proved by engineers who ran tests on the remaining sea sand from the Katunayake-Colombo Expressway construction project. This sand, which has been rain-washed and sun-dried for years, showed a similar quality to river sand.
Prof. Dias also explained that when initial studies into alternatives to river sand were conducted, other alternatives like manufactured sand (or artificial sand) were considered, but the properties of such manufactured sand were not as desirable as natural sand, and might require other measures like additional use of cement, which also has a harmful impact on the environment.
Sea sand vs. river sand for use in construction
But is mining sea sand the way to go, or is it opening the door to a whole new range of ecological problems?
According to data from the Ministry of Environment, the annual national demand for sand from the construction industry is an estimated seven million cubic metres. Typically, much of this sand is mined from riverbanks and riverbeds, which has a serious ecological impact on the environment. The government has imposed several restrictions on the mining of river sand over the years, and while the efficacy of such restrictions is the subject of strong debate among conservationists, these restrictions have created a scarcity that consequently pushed up its prices in the market. In fact, during the last eight years, the price of river sand has doubled, making it almost unaffordable to the majority of the general public.
Prof. Dias shared that the mining of river sand is unsustainable for many reasons; it contributes to the collapse of river banks; it causes deepening of river beds, which leads to saltwater intrusion and increased salinity levels in the river; and it results in less sediment being transported by rivers to the sea to supplement sand along our coastlines, thus increasing coastal erosion.
Commenting on dredging sea sand from an environmental perspective, Prof. Dias explained that dredging and mining sand in areas off the coast, and both below and up to a certain depth, could arguably cause only a temporary disturbance to the marine environment that could be recovered from relatively quickly once mining stops.
In any case, sediment washing into the sea alone from rivers can have an impact on marine life in the area because of the suspended and settling sand particles. “In my opinion, most people would consider moving sand-mining offshore,” Prof Dias said. “Since any environmental impact from offshore sand dredging would be much less than mining river sand.”
Brunch also spoke with environmentalist and Rainforest Protectors Convenor Jayantha Wijesingha for his views on the potential ecological impacts of expedited and increased sea sand mining.
While noting that it isn’t possible to directly say that mining sea sand for construction is sustainable, Wijesingha did note that if sand was taken from the ocean in a sustainable way, which is to say, from a clearly designated area where it is clear just how deep you can go when dredging up sand and from an area that is not home to marine biodiversity (hatching areas, breeding areas, coral reefs, and so on), it is possible for there not to be a severe ecological impact from mining sea sand. This is, however, strictly contingent on mining being carried out carefully and systematically.
Wijesingha did stress that uncontrolled or irresponsible sea sand mining can throw off the sand account (the ecological balance of the ocean bed), and have multiple adverse ecological impacts, most notably soil and coastal erosion.
“As a conservationist, I prefer sand being mined from the oceans rather than from the rivers because mining from rivers is much more harmful than the dredging of sea sand,” Wijesingha said, adding: “But on the other hand I must emphasise that marine sand must only happen if mining river sand is strictly limited. Many river banks, like the Deduru Oya, for example, are mined despite strict orders and regulations.”
Understanding the potential for disaster
Bearing in mind the struggle to control river sand mining, Wijesingha shared that the combination of marine sand mining with continued irresponsible river sand mining can have disastrous consequences like drastic increases in coastal erosion.
Explaining that healthy riverbeds will be crucial to balancing the marine sand account because the sediment in rivers will be washed out to estuaries and then out to sea and work to balance out the gap left by the sand mined from the sea, Wijesingha stressed that the irresponsible mining of both sea sand and river sand could see escalated examples of situations, like the one in Kalutara where salinity levels in the Kalu Ganga increased to the point that freshwater had to be transported in because the natural freshwater supply had too much salt to be potable. This salinisation of the water was a direct result of irresponsible river sand mining along the Kalu Ganga.
“Realistically, if the Government wants to promote sea sand mining, and restrict riverine mining, then they have strong control on riverine mining,” Wijesingha said, stressing that things like deregulating sand mining, and allowing things like special licenses and allowing people to mine sand without appropriate clearance, would need to be completely stopped.
Wijesingha also spoke about other measures that can be taken to balance the sand that is mined on the coast, pointing out that the Netherlands has developed technology and machinery that allows them to replace sand mined closer to shore with sand from further offshore. The Government has had this technology temporarily imported at one point to aid with filling the Mount Lavinia beach with sand. Wijesingha said that investment in technology and expertise might be prudent if mining sea sand is to be promoted as an alternative to mining river sand.
Stuck between the devil and the deep blue sea?
Wijesingha also pointed out that while promoting marine sand mining may fix the issue of riverine sand mining now, it may well create larger problems in the future that we don’t anticipate. It all boils down to a sense of choosing the lesser of two evils, with Wijesingha saying that when balancing the two options, mining sea sand has less of an environmental impact. “I firmly believe that riverine sand dredging has significantly larger impacts than marine sand dredging. So in that aspect, marine sand dredging is good. We can’t oppose it because then we are promoting riverine sand dredging.”