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Pollution Stop – Gross Pollutant Trap (GPT) Management

The reliability of stormwater assets is key in environments where floods are a part of life and many people live near waterways. Good infrastructure removes excess water, treats it to remove pollutants and directs it into waterways.

The first stages of most stormwater systems are Gross Pollutant Traps (GPTs) and water impoundments, such as settling ponds or artificial wetlands. If either of these fails, stormwater will either back up, overflow, or be bypassed, causing localized flooding and poor water quality. GPTs are concrete structures set in the ground, that trap large objects (typically > 5 mm) from street drains. They fill with debris over time and need to be manually emptied periodically.

A well-tested technology is used to continuously monitor the distance between ground level and the top of the debris accumulating in the GPTs. Ultrasonic sensors are widely used in industrial and domestic applications to measure distance, commonly water levels in tanks. Sensors are mounted on the undersides of covers of the GPTs. Because the lids are made of metal, that blocks radio waves, an aerial was installed on the outside. This was specially constructed to resist damage by vehicles and vandalism. Data is transmitted via LoRaWAN and the TTN network.

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