"It's close to the end, but it's a day-to-day assessment."
There are still 20 personnel involved in the search at the landfill.
Sweeney said six officers were working fulltime on the case with a "wider team completing day-to-day inquiries".
Police have searched areas in Ellesmere, including a gravel pit and forest in Birdlings Flat, Lincoln and Halswell based on new information gathered during the investigation.
Police also carried out extensive searches of the Halswell Quarry and ponds in the surrounding area using a dive squad earlier in the investigation.
It has been reported the landfill became a focus of the search after corrections officer David Benbow dropped off material at the Parkhouse Road Refuse Station.
Material from that station is taken to the Kate Valley Landfill.
Benbow and McGrath were childhood friends who attended Hillmorton High School together.
Benbow was named as a person of interest early in the investigation with police refusing to say if he was still a person of interest or not.
His Candys Rd home in Halswell was also searched by police.
"Michael McGrath is still missing and the case remains in the same status," Sweeney said.
If you have information which you believe could assist the search, phone 0800 FINDMICHAEL (0800 346 364).