Sewer lagoon value to a city that may want to use it

I own a park on the edge of a large metro area but in an area there is no city sewer so I’m on a lagoon. Today I got a call from the city asking if I would be interested in letting the lagoon be used by others so there can be some commercial development in the area. I have no desire to be a sewer company so my first thought was to offer to give them the lagoons in exchange for free usage as log as I own the park (or maybe even for as log as the park exists). The lagoons cost me about $2000 a year for DEQ fees, mowing and a jet truck to clean a clog a few times a year. The city is also who I get my water from. So depending on how much the lagoon is worth, maybe I can get them to take over my water system also saving me the hassle of water testing every month (down side is I installed water meters to bill back water 2 years ago, but I could move meter to new property in the future).

I don’t want to be greedy with this as development will help my park and if something ever goes wrong, I’m not on the hook for repairs. But I don’t want to short change my self either.

I’m sure it will cost $500K to $1M for the developers to connect to my system as its about 2 miles from where they will be building.

Land value for the 8 acres is maybe $50k.

I’d like to hear any suggestions for negotiating a fair deal if this actually comes through.

A few questions:

Is it Technically feasible i.e. do you have any spare treatment capability?
I would need to know the following:
How many spaces is your park?
How many acres of lagoon do you have?
How many cells i.e ponds are in your lagoon system?
What state you are in?
Is it a total containment system(evaporation), irrigation with the treated water, infiltration, or sent to a stream?
Do you have additional land to add more lagoon cells or replace a failed one?

Practical considerations:
What kind of commercial activities would happen (certain uses might kill your lagoon microbes)?
If you could get the city to take over complete operation and be liable for all upkeep and maintenance it could be a great idea. I highly doubt they will sign up for taking over all liabilty associated with your lagoon and guarantee to treat the sewer from your park for ever at no cost.

4 cells that cover about 5 of the 8 acres. The city owns the land around it. I only use 2 cells as it was originally designed for expansion, but I have no plans or specs as to how much. My expectation is if the city wants to use it, they will have to take it over as I do not want the liability for others using it.

My question here is not about what capacity will it handle, but how much is it worth to me and ideas of how to hand it over to the city.

At my other park that is on city water and sewer, my sewer portion is about 1/3 of the bill. If I use that as a comparison to this park just to get a $ value, my water bill is about $36,000 a year. So that would be about $12,000 for sewer. So over 10 years that would be a value of $120K. Replacement, from what Dave says is $250K or more.

If I sell it to them and then get charged for using it, I don’t think that would be a win for me as I’m at their mercy for paying what they want to charge.

I think if you off loaded the lagoon and got free waste water treatment that would be a good deal. Any thing above that would be a great bonus.