According to Superior - which has the ASX ticker SUP - the proposals range from US$50-70 million.
A bankable feasibility study is said to be imminent, with a "restart" study late last year estimating start-up capital of $75 million.
That same study estimated the project had a post-tax net present value of A$158.5 million and internal rate of return of 48%, though inputs used featured zinc and copper prices well above current levels (mitigated to an extent by us of a 0.75 exchange rate).
Also of interest in the upcoming feasibility study will be the TC/RC charges used for Superior's concentrates, given recent decade high costs levelled by smelters at zinc producers.
Superior raised $3.8 million late in June when it issued new shares priced at 1.75c each.
Shares in Superior were up 13% to 1.7c, capitalising the company at $18 million.
The stock has steadily declined from levels around 5c last October.