Location of pond
A site investigation before design and construction is important to ensure the pond built is structurally sound and meets regulations, says DairyNZ.
The system, used in Waikato and Canterbury, is accurate to 0.8mm says the supplier, Opus Rural Services.
The Opus Pond Drop Test (OPDT) system was developed by engineer Dr Marc Dresser, a rural consultant with the company. Dresser designed, built and tested the OPDT with engineer colleague Andy Johnson (CPEng). Dresser now builds the equipment and trains national operators.
“The test provides clear, industry accepted results that indicate with scientific precision whether a pond is leaking and by how much,” Opus says.
“It does this using a 48 hour test calibrated on site in specific test liquid and data logs pond information every ten seconds, taking into account rainfall, evaporation and atmospheric pressure change. Such precision testing helps ensure dairy effluent systems are compliant and efficient, while offering farmers accurate information to help make informed decisions as to pond replacements or repairs.”
The OPDT can be used on all liners, pond types and with many liquids, providing results in line with or above regional council requirements and industry standards.
The test is approved by Waikato Regional Council, Environment Canter-
bury, dairy companies
and DairyNZ.
Opus last month met with 30 people from local council and dairy industry agencies to mark the launch of OPDT in Southland. Dresser told the group the OPDT is “desperately needed technology” because regional councils are demanding proof of pond integrity.
The OPDT is calibrated on site in specific test liquid; results are logged in every 10 seconds. Results take into account rainfall, evaporation and atmospheric pressure change.
There are some prerequisites for OPDT to work. The pond must be at least 75% full. Dresser says this ensures most of the wetted area of pond sealing surface is tested. There should be no crusting in the pond and there is a wind limit.
Waikato Regional Council says evidence provided by the OPDT satisfies its requirements and “is accepted as an appropriate test for assessing effluent pond sealing”.
Environment Canterbury says it has been impressed. “We are satisfied that the OPDT satisfies the requirement for Canterbury Regional Council in that it provides an acceptable effective standard for monitoring pond level change.”
