It is under construction at the moment. We are working with our EPC contractor, GR Engineering. GRES a re, in short, one of the best in the business at this. This is their bread and butter. A 1.5 million tonne per annum CIL plant in the Goldfields is their bread and butter. They're doing a fantastic job at the moment. Currently ahead of schedule, bang on costs. We're looking forward to working with GRES and getting this project delivered. It is a 1.5 million tonne per annum plant that we're building. We thought that was the appropriate size to start. However, there are significant elements of this plant that are actually already designed and being built as a 2.5 million tonne per annum plant.
We wanted to have that upside optionality for us as a business, that when we get this project into cash flows and into production, we can look at project expansions, we can look at exploration through that Goldfields district, and potential for other inorganic opportunities. The DNA of this business in the early years has been underpinned by M&A. I think we've done five or six M&A transactions over this journey to deliver this portfolio. We are now very focused on execution. As always, the job for us ahead of us is to build this project, get it up and running, get it cash flow funded. We better use those cash flows to deploy across the portfolio. That expansion case is important for us. We think it's a real neat and novel way to grow the production from 75,000 oz to something north of 100.
In terms of a traditional risk profile for a single asset developer like Brightstar as we are, there's a lot of key features here that we believe means that it's a significantly de-risked opportunity. All these ounces and projects have been mined before in the past. We've got production records. We know how they've reconciled. We've personally been mining some of them for the last few years. We built the Fish Mine last year. We've been recently mining and toll treating that through Genesis under an ore purchase agreement. We know how that mine performs. We are an owner-operator business. We've been running those undergrounds ourselves. We have a lot of IP in the business about actually running a mining organization. That's everything from your finance function, your maintenance, your HR, your health and safety, all your systems and your processes. All the things a mining business needs.
Brightstar doesn't need to deliver them. We've already got them and we're operating. That's a big reason why this is not a conventional single asset developer. We're not five employees in West Perth trying to build a mine. We've got 150 miners in this business. We are simply looking to build another open pit mine and a processing plant where we've partnered with the best in the business. We think this is, as a single asset developer, quite a unique proposition. All of these mines have been previously mined, as I mentioned. We do have a great knowledge base for all these projects, which just goes to that de-risking approach. We are looking at pouring first gold in less than 12 months. June next year, we will be commissioning.
We do have that sort of gray line through the middle there, sort of brown, for that potential expansion case. We do see that opportunity coming early in that mine life. Once we're into cash flows, to cash flow fund that expansion is a relatively modest amount of capital. We'd look to put an additional ball mill and two more leach tanks in, and we could be taking this to north of 100,000 oz per annum. The economics, as I mentioned, made sense. This is a project that we were very focused on getting funded, permitted, and into production. You can see here the economics. Pick a gold price, borderline around spot, making about AUD 160 million-AUD 180 million a year of free cash flow. The opportunity for us is to use those cash flows to redeploy towards Sandstone and also expanding Goldfields.
All-in sustaining costs are about AUD 3,000 an ounce. You're talking almost 100% margins at current spot. This is a project that got funded. It is a great cash flow producer, and we'll certainly be looking at ways to make this project a lot better than what it might be looking like. Changing tack now to the Sandstone project. This is our flagship project. We acquired three different companies and assets to kind of get this portfolio. We really liked it for two reasons. When you looked at this district before Brightstar's entry, it was characterized by fragmented ownership. There was about 7 million or 8 million ounces of gold controlled by ASX juniors, private companies, and they all lacked systematic exploration. They lacked access to capital, and the reality was none of them were going to get developed in and of themselves.
We saw this opportunity as a fantastic consolidation opportunity to come in and buy these projects, give us that footprint in the district to build a business on the back of. The second reason why we really like the Sandstone district in general was due to the lack of that systematic exploration history. When you look at when this business was mined in the early 2000s, gold price was less than AUD 1,000 an ounce. The previous operator only looked at taking the oxide material at a very small processing plant on site. They did no exploration. Of that resource base there, we've delivered 2.9 million ounces. About 1.8 million of that is in the top 150 m.
When you look at the geology of this system, what's been mined, what's still in the resources here, it'd be extremely uncommon in the context of the Eastern Goldfields, greenstone belts like this, to have 5 million, 6 million, 7 million ounces of global endowment just in the top 150 m-200 m and for there to be no exploration at depth and for there to be no resources at depth. That's why we kind of look at this opportunity. We know right now that this is a very substantial development project. There's a critical mass to take it towards production. We've got over 1,800 sq km of fertile greenstone belt, we think there's real opportunities for discoveries. I'll touch on the hole we announced on Monday, which we think is potentially a game changer for some of these Sandstone deposits.
We are looking at having another resource upgrade out in November of this year, contemporaneous with our pre-feasibility study. For us, we think that study should show something that is a very material Western Australian gold development project that really will set it in rarefied air. When you look at what we're trying to achieve here at the Goldfields, we are trying to get this project into development as quick as possible. It is slightly further back in the development queue than Goldfields. We are going through a pre-feas at the moment, rolling straight into a definitive feasibility study for next year. Approvals and permitting is going on at the same time.
We would like to get this project development ready coming into calendar year 2028. That is the same time that the Goldfields project's humming, it's commissioned, it's producing free cash flow, we think there's a real opportunity for us to finance a lot of the equity components for this particular project out of operational cash flows. As a junior developer, that is rarefied. We think that the portfolio approach that Brightstar has taken, yes, it's taken a few years in terms of all our M&A, aggressive exploration, building out the portfolio. To go from 400,000 oz to 4.5 million in three years really just shows you how aggressive we are with growth and where we think we can take this business. Looking at Sandstone, it is a genuine camp of deposits. We had a material exploration result at our Two Mile Hill deposit earlier on Monday.
We announced the intersection of 305 m at 1.82 g/ ton. For us, that was a really important hole in that extended the known mineralization, or the perceived or interpreted edge of the host tonalite, we think that's a real opportunity to add some significant ounces. We've got two diamond rigs back on there drilling right now. We expect to be able to report results over the coming weeks. For us, that's a hugely important milestone and really exciting for the business. As a hub here, we know there's critical mass. We've got 2.9 million ounces. We spent the last two years really improving the quality of these resources. We've gone back to every single deposit, everything from the geological interpretations and the wireframing, all new resources, all Brightstar drilling into it. We know that this is a dependable and robust resource.
This is going to get mined by Brightstar. We wanted to make sure we did it well. There's 2.9 million ounces there where we've done a lot of diamond drilling for the geotech, for the met, for geological structural understanding. We're trying to do the basics well here. We're now really starting to look at the growth opportunity for us. We haven't even really started asking ourselves how big could Sandstone be. What does that mean for us? We know we've got critical mass for development. We don't really need any exploration, further success, even though we're pretty confident it's coming, we also don't need to look at other M&A. We've got the critical mass for a business that could be a 200,000 oz per annum producer in its own right.
We do have ongoing infill drilling at our couple deposits here at Bull Oak, Indomitable, and Two Mile Hill. Those three deposits alone have over 1 million ounces of inferred resources. Key target for us is to convert more of that into indicated for the Pre-Feasibility Study. We've got 1.1 million ounces of indicated at the moment at a very healthy 1.5 g/ ton. We think there's real opportunity to grow that again materially. That M&I component grew 100% since the last resource update. We think there's real opportunities to keep pushing that number up. When you look at what we're trying to achieve as a business, look, we're not a single asset miner. We always wanted to be a multi-asset producer. We think there's a real opportunity to be a 200,000 oz - 300,000 oz producer in the coming years.
We know that the resources that underpin that are in the business today. We don't need any more wild exploration successes or M&A. This business portfolio is set. We've got the team that's built mines. We've been running mines for the last few years. We think it's a real opportunity to build a genuine mid-tier miner. When you look at the context of the WA gold sector, there is clearly a wave of M&A that's been coming and arguably will continue. We think that what we've got as a business is a very material asset in the context of WA gold developments. Just on that chart there on the right has shown our resource growth over the last few years. We've delivered that through M&A and also aggressive exploration.
We've spent tens of millions of dollars and hundreds of thousands of meters of RC and diamond drilling, doing all these resources and growing it. Where is this going to be in the next couple of years? We'd like to think we can continue that trajectory. When you look at where we sit in terms of WA gold developers, it's really Brightstar and Minerals 260 with their Bullabulling project as clear standout projects with developers of scale. That's something that's really important to us as a business. It's important that you've got to attract that institutional capital. You need to be relevant to the mid-tier sector. We were very focused as a company not to be a 60,000 oz- 80,000 oz producer. We really wanted to make sure that we had aspirations underpinned by the assets to genuinely build a mid-tier scale business.
In summary, we are a developer. The Goldfields project is in construction at the moment. It is real. It's happening. We are pouring first gold in less than 12 months. We've got the very material Sandstone project. We've made an economics to come out with a Pre-Feasibility Study in November of this year. Don't get caught sleeping on Sandstone. I genuinely think it's probably the best development asset in Western Australia. We've got a great team to be able to execute this. We've got a team of genuine mine builders. We've been very successful in attracting a lot of talent out of the mid-tier mining sector to want to come and build a business. It's very rare that you get afforded the opportunity to be able to build something from scratch. This company had one employee three years ago. That opportunity attracts really high caliber talent.
It has been awesome, it's really exciting to work alongside some awesome professionals. Drill, drill. It is a motto internally. We're very focused on capturing the organic value in the portfolio. We think there's opportunities to grow this resource materially with just ongoing good exploration and good science. We think there's a real opportunity for this to re-rate and capture that value as you migrate from being an explorer/developer into a producer. Looking at cash flow multiples, looking at EV on production ratios, there's just no way that this business can't re-rate materially on execution, and that's what we're focused on. Of course, we need to make sure that we're doing all the right things with our community engagement and our social license to operate. We are operating in some of the best gold towns in Western Australia. Menzies, Laverton, Sandstone. These are all storied mining towns.
Hundreds of years of mining history here. We're very proud to be able to try and rebuild some of these towns and some of these mining districts that have sat unloved for decades. Thank you very much.