United States marines only spent $1,164 each during their time on rotation in the Northern Territory, or less than $7 per day during a six-month rotation, a KPMG study commissioned by the Australian Defence Department has found.

Key points: The US marines training rotation was touted as a boost to the NT's ailing economy but only delivered $7.5m in 2016, according to KPMG

The US marines training rotation was touted as a boost to the NT's ailing economy but only delivered $7.5m in 2016, according to KPMG A colossal spend of $250m is forecast for 2020/21, mainly to be spent on capital works, but there is little detail on specifics

A colossal spend of $250m is forecast for 2020/21, mainly to be spent on capital works, but there is little detail on specifics The report found fears of increased anti-social behaviour and sexual assaults had not been borne out

The new report also found that very few choose to holiday in the Northern Territory when on leave.

Last year, 1,250 marines spent up to six months in the Top End as part of a deal signed by Julia Gillard and Barack Obama in 2011, which expected to see a full complement of 2,500 marines each year by 2017.

It is now expected that numbers will increase to between 1,600 and 2,500 each dry season by 2020.

The training rotations have been promoted by the Federal Government as a boost to the ailing NT economy, but the overall presence of the marines and aircraft has delivered just $7.5 million a year to the NT in 2016.

However, the KPMG report predicts a massive increase in spending by US forces in the NT next year, with an expected quarter of a billion dollars to be invested in capital works — but very little detail has been offered on what those works will entail.

The US Marines spend up to six months each year in the Top End. ( Supplied: Australian Defence Force )

Marines spend 'small'

Analysing the economics of the 2016 rotation of 1,250 troops, KPMG found that in total, the US Posture Force Initiative (USPFI) marines spent an estimated $7.5 million on service contracts for things including food, accommodation and transport hire.

"At $7.5m, the contribution made to the local economy by the USFPI in 2016 was relatively small, yet positive," the report stated.

The consultancy "conservatively" estimated the marines spent about $1,164 each, mostly on food and drink, in the Territory during their recreation leave, and on evenings and weekends off, for a total of $1.45 million.

"When on liberty, local spending by US marines is mainly limited to purchases of consumables," the report found.

"In addition to liberty, US marines can also choose to take recreation leave in Australia. However, uptake of recreation leave is limited since days of leave taken are counted against the 30 annual days of leave that each US service member is entitled to annually.

"Of those that do take recreation leave, few do so in the Northern Territory."

The marines only spent $55,647 on shopping on items to take home or for use in Australia, at an average of $44.52 per person over their stay.

US marines run through smoke and dust as they breach an enemy position during training. ( ABC News: Steven Schubert )

Local businesses waiting for $2b from Defence

KPMG said the total Australian and US Defence forces' combined contribution to the Territory's 2016 $25.2 billion gross state product (GSP) was $704 million, or 2.8 per cent.

That was compared to the Territory's major economic sectors — public administration (13.9 per cent of GSP), mining (13.5 per cent), construction (12.5 per cent), housing sales (10.7 per cent) and health care (7.3 per cent).

Many of the Territory's struggling economic sectors, including construction and the property industry, have been hanging out for the $2 billion spend on infrastructure promised by both the Australian and US Governments at RAAF Base Darwin, RAAF Base Tindall in Katherine, Robertson Barracks in Palmerston, Kangaroo Flats, and Mount Bundey.

That includes runway strengthening and more fuel storage facilities, and accommodation, gyms, and mess eating areas for the marines, particularly at Robertson Barracks.

A media release from Prime Minister Scott Morrison said last month that "the US Force Posture Initiatives have already proved to be a boon for local Territory businesses who have supported the rotations or been involved in part of the $2 billion being invested by Australia and the United States in Infrastructure and facilities to support the initiatives".

Massive ramp-up in US capital works

KPMG estimated the US marines' spend in the NT would be worth about $250 million in GSP in 2020/21, more than 30 times the $7.5 million they spent in 2016.

The majority of that is capital works projects, but what those projects will actually be has not yet been articulated.

It's forecast that the US will spend $250m on capital works in 2020/21. ( Supplied: Australian Defence Force )

"Under the potential future impact scenario, the contribution of the USPFI to the Northern Territory ramps up significantly when future capital works [capital investment] are considered," the report stated.

"Capital works, which include upgrades to existing Defence bases and training areas, provide a solid boost to the local economy, particularly the construction and professional services sectors."

It said that "nearly all sectors" would get a boost as jobs were created households spent more.

"It is important to note that these impacts are during the construction of the USFPI-related capital works in the Northern Territory, and as such will not continue indefinitely," the report said.

Without the capital works spent, the consultant found the boost in the marines' numbers from between 1,600 and 2,500 personnel could be worth between $12 million to $14 million in NT GSP for the same period.

KPMG estimated that the increase in the marines' rotations and the accompanying air base works needed for the US-Australian Air Force exercises would increase the number of people directly and indirectly employed by the United States Force Posture Initiatives from 45 in 2016 to 1,062 in 2020, but only temporarily, while projects are completed.

The Coalition announced last week that if it is re-elected, all companies tendering for work from that budget, valued at $7.5 million or more, will have to demonstrate they have a local industry capability plan showing how local businesses have been engaged and what work they have gained from the projects.

US marines numbers in Darwin will eventually reach 2,500 per rotation. ( ABC News: Steven Schubert )

'Sexual assault concerns not borne out'

KPMG also carried out a social impact assessment of the marines' rotations.

It has reported that the results from phone surveying 408 residents in the greater Darwin area and holding two public consultations were that 51 per cent felt positively about the rotations, 43 per cent were neutral, and 6 per cent did not support their presence.

Forty-seven per cent of the people surveyed felt safer as a result of the US military presence, while 6 per cent felt less safe.

KPMG noted that the 2013 social impact study commissioned by Defence "identified concerns regarding the potential for increased alcohol-related behaviour and sexual assault in Darwin as a result of the US marine rotations".

It found in its latest report that anti-social behaviour by the marines had not been a problem, and that "during stakeholder and public consultations in 2018 … respondents were mostly in agreement that any fears of increased sexual assault prevalence had not been borne out".

'Localised noise'

KPMG said increased Air Force cooperation had accompanied the marines' rotations since 2017, with 13 aircraft including four MV-22 Ospreys, five AH-1W Super Cobra helicopters, and four UH-1Y Venom helicopters taking part in US-Australian air exercises, along with a squadron of F-22 Raptors in 2017.

A third of people KPMG surveyed felt noise levels had increased because of the US military presence, while almost two-thirds felt the noise was localised.

Almost half of residents felt the marines had had no impact on Australia's relationship with neighbouring countries. ( ABC News: Steven Schubert )

The exercises included training on aeromedical evacuation, combat mobility, and expanding air to air refuelling capabilities.

KPMG's phone survey also asked Territory residents what effect they thought the US presence had had on Australia's relationship with neighbouring countries — 17 per cent said the impact was negative, 27 per cent thought it was positive, and 43 per cent said they thought there had been no change.

KPMG also reported in 2017 that US marines made 69 visits to 17 schools, attended 88 community events and volunteered 1,500 hours of their time.

In 2018 they also helped remove fallen trees throughout Darwin after Cyclone Marcus.