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Summary of Drain Detectives Results: Dec 2018 - May 2019

From December 2018 to May 2019, the Drain Detectives project sampled drains at beaches in Sandringham, Mentone, Mordialloc, Dromana and Rye.

Results for 2018–19 are based on:

  • trained citizen scientists sampling beach drains for ammonia (used to indicate the presence of faecal pollution).
  • reports from community using Drain Detective signs
  • EPA sampling drains.

Drain Detectives sign at Dromana Beach

Anyone can make reports by following the instructions on Drain Detectives signs. Source: EPA Victoria

What have we learnt from Drain Detectives monitoring for 2018–19?

Overall, monitoring results indicated that there was low risk of drain flows causing pollution during dry weather. However, more monitoring is needed in 2019–20 to confirm this. Results indicated:

  • most drains were either not flowing or had small flows
  • ammonia (as an indicator of faecal pollution) was not detected in most flows
  • not all drain flows enter Port Phillip Bay
  • microbial levels in flows varied
  • where flows entered the Bay, they had no impact on microbial levels monitored. This is most likely due to the small size of the flows and dilution once they enter the Bay.
  • high microbial levels were usually due to animal faeces, which poses a lower risk to human health than human faeces.

How many citizen science reports did we get in?

Key drain statistics

338 citizen science reports

57 trained citizen scientists

52 reports from community using drain signs

How many reports were received for each beach?

88 Sandringham

66 Mentone

15 Mordiallic

103 Dromana

66 Rye

Ammonia testing at Sandringham Beach

Citizen science volunteers taking ammonia samples at Sandringham Beach. Source: EPA Victoria

Citizen science monitoring – what does the data tell us about dry weather flows from drains?

  • Most citizen science reports received were for drains not flowing or that had small flows:
    • 34% drain not flowing
    • 57% small-sized drain flow
    • 6% medium-sized drain flow
    • 3% large-sized drain flow

  • Not all flows reported reached the Bay.
  • 44% of flow reports occurred during dry weather. This means these flows were not due to rain. We will investigate further what could be causing these type of drain flows.
  • Citizen scientists found that 31% of dry weather flows had ammonia detected, with only low levels of ammonia detected (ranging between 0– 0.25 mg/L). As ammonia is used as an indicator of faecal pollution, results indicated there was little or no faecal pollution in dry weather flows.

EPA monitoring of drains

  • EPA sampled drain flows and the Bay on four occasions during dry weather. Our results indicated:
    • mostly small drain flows
    • microbial indicator levels (E. coli and enterococci) varied in drain flows.
    • when the source of faecal contamination could be detected, it was from animal source rather than human. Animal faeces pose a lower risk to human health than human faeces as they are less likely to make you sick (e.g. gastroenteritis, nose and ear infections).
    • where flows entered the Bay, they had no impact on microbial levels monitored. This is most likely due to the small size of the flows and dilution once they enter the Bay.
    • low microbial levels detected were consistent with Beach Report monitoring results with little or no high microbial levels detected during dry weather.
    • low levels of heavy metals in drain flows which pose no risk to human health.

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