That would happen when it leaks out, so I guess monitoring for acidification as well as signs of potential impact.

The main environmental concerns have been the dredging and seismic activity on marine life as well as increased traffic. [1] I read the porous rock they're targeting is at some depth under the seabed.[2] Same info as [2] but including a map of West Peron undersea rock formation area targeted [3]

[1] https://apnews.com/article/carbon-capture-ccs-japan-australi...

[2] https://www.reuters.com/business/energy/australia-names-offs...

[3] https://www.bairdmaritime.com/offshore/renewables/other-rene...