Foreshore

The Swan River Improvement Act (1925) authorized the reclamation of land along the Swan River from East Perth to Maylands, as well as areas on the otherside of the river. The Public Works Department began reclamation work in 1927 but had to stop due to financial constraints brought on by the depression and wouldn’t resume until 1933.

 

Fly ash was used to reclaim the foreshore because there was so much of it available, it was cost effective and easily transported to the river. When added to soils, particularly sandy or silty soils, it binds well and increases the strength of each layer. As beneficial as it was turning a waste product into reclaimed land, environmental risks like leaching would apparently to be managed later.

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A 23m stretch of the foreshore in front of the power station was reclaimed with fly ash in the 1950's.

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The Foreshore Today

Photos of the foreshore show what appears to be consolidated ash deposits, which isn't a surprise considering reports of fly ash used for reclamation, particularly in this area.

Fly ash consists of loose grey powdery deposits in its initial state. 

Over time, it hardens like “ashstone” (a type of volcanic rock formed from fine volcanic) with sediment layers due to moisture, compaction or fill capping. It can take on the appearance of shale, especially when its been dumped in stages and covered with sand or dredged material. 

The colours and textures shown in the photos typically match fly ash that's been compacted, weathered and mixed with sand, organic matter and estuarine salt. 

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Contamination

Leeching tends to happen in the first 10-20 years, especially when trace elements like arsenic, selenium and lead is exposed to water or acid soils (low pH).

The presence and growth of vegetation like grasses and trees helps to stabilize beds of fly ash, reducing airborne dust particles. 

Contamination risks are decreased if fly ash is buried, capped, vegetated, mixed with soil, not eroded, the land isn't used for food-growing plants and it's not in contact with groundwater. 

When deposits of fly ash are uncovered, disturbed or are eroded, the risk of contamination increases. If risks aren't managed, the potential long-term effects still include heavy-metals leaching into the groundwater. 

Whilst arsenic, boron, chromium and selenium are commonly found in fly ash, usually below the acceptable limit, chronic exposure would be needed for fly ash to present a danger to the environment and human health.

Further cleanup and capping efforts is usually recommended for sites that are being developed or remediated for residential use.