£28,000 was spent on the pollution investigation at Elizabeth Marina.
Contractors Legendre, who are building the Horizon apartments on the Waterfront, were last month fined £10,000 for breaching the water pollution law.
Reports surfaced in February of contaminated tidal water at the Marina, prompting an investigation by Environment Protection Officers.
Legendre then pleaded guilty to causing the pollution - as suspended solids were entering or being disturbed in the Marina because of seawater flowing from the development site.
A Freedom of Information Request has revealed that £25,000 of the £28,000 went on staff costs. Water and sediment analysis cost nearly £2,500, with £435 spent on a marine survey.
Those costs included visiting the sites, collecting samples, interviewing people, getting statements and CCTV footage along with preparing the prosecution file.
Registration open to build own F1 car!
Haut du Mont trial: Island Energy 'placed health and safety at risk'
Deportation recommended after sex-demanding attacker jailed
Teenage boy arrested on suspicion of sexual touching at Millbrook Park
Eyes up! It's Air Display day...
Haut Du Mont Trial: 'It could explode', jury hears 999 calls
Haut Du Mont Trial: Worker checking gas valves spent almost 'entire' time on his phone
Red Arrows still expected for Jersey Air Show
