I think it has several problems. First, what does "event" refer to? What do you mean by "event." Does it refer to the party? If so, that does not make much sense. Does event refer to "the construction progress."? Also, I am not sure what "the engineering department" is doing in this sentence. Is the engineering department the department that is giving the party? Or has the engineering department received much of "your" concerted effort"? We also do not know the status of the construction progress. Is it complete? Has it even started? Is it still going on? There are also other confusing things.
But if interpret the sentence as the best guess of what I think you want it to mean, then I would rewrite it as:
The "Thank You Party" is for the tremendous effort you have contributed towards this project, especially to the Engineering Department--which has invested a lot to ensure the construction progress.
It might be better to express your idea in two sentences. Because you are trying to say a lot in one sentence. That is part of the reason the sentence is confusing.