Use cement blocks for egress window well surrounding

Question

I need to make an egress window and the depth below grade is 24".

However, most egress window wells at home improvement stores are 20" in height and I need to buy 2 of them which made the cost double.

I am thinking about using cement blocks to make the well like so

It may cost me only $200 vs $800.

My questions: 1. Is this allow by code (in general)? I am in Washington State

2. How to prevent water leakage inside the well? Basically do I need to seal it (like bathroom)?

Thanks.