Measuring pH of Construction Site Stormwater


Stormwater is a term for the runoff water resulting from a precipitation event such as rainfall in urban areas. Urban areas tend to have large amounts of impervious surfaces, resulting in large volumes of runoff. As stormwater flows over these impervious surfaces, chemicals, pollutants, debris, and sediment are gathered. This pollutant and nutrient-rich stormwater ultimately drain into sewers, where it continues to a wastewater plant for treatment or into a natural water body such as rivers, lakes, wetlands, and estuaries. Rainfall events and the associated stormwater can cause surface water pollution and is therefore monitored and regulated.

In Australia, sampling and testing requirements differ based on the location of runoff. Most authorities dictate that stormwater leaving a construction site must be within a pH range of 6.5 to 8.5. The pH of the stormwater is typically measured at the point of discharge to the waterway or at the point that it leaves the construction site. Measurement can be performed either directly in the flow or storm water or in a sample that has been collected in a bottle. When a pH reading is outside this range, treatment is required. Additionally, the onsite source of pollution must be identified and remedied. At construction sites, pollutants can come from a variety of sources. Best management practices (BMPs) such as silt fences, retention ponds, and hay bales are often utilised to catch and filter stormwater runoff, but damaged silt fences or high sediment build up reduce the efficiency of BMPs.


hi98190_600x600A construction company contacted Hanna Instruments about an instrument to measure the pH of their stormwater onsite. The customer was required to measure heavy metals and pH in their stormwater runoff for their local permit, and had been previously sending samples to a lab for analysis. Because measurements for pH must be reported within 12 hours of the rainfall event, the customer wanted to be sure that they were getting an accurate reading within the specified time frame. The construction company specialises in pre-planned neighbourhoods and therefore works with large amounts of concrete. The customer was required to report their stormwater pH as concrete is strongly alkaline can strongly influence stormwater pH if the proper BMPs are not in place. The customer was looking for a rugged meter that came with a carrying case for easy field use.

Hanna Instruments recommended the HI98190 Waterproof Portable pH/ORP Meter. The customer appreciated that the HI98190 was waterproof and came supplied with the HI12963 titanium bodied pH electrode. The durability of both the meter and electrode, along with the rugged carrying case, gave the customer peace of mind that the equipment would have a long lifespan, even when used in stormy conditions. The CAL Check™ feature of the HI98190 allowed the customer to view and report when the meter was last calibrated to ensure compliance in their pH reporting. The log-on-demand feature allowed the customer to log the pH reading, date, and time of each measurement for ease of reporting later. The HI98190 provided the customer a convenient and valuable solution for their pH measurement needs.


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