A civil engineer will have to create a topographical survey showing the elevation changes on the property.

They will be able to calculate and determine drainage requirements whether it goes to a storm drainage system the city has in place, or to a containment tank/seepage tank buried on your property.

The reason to create a plan like this, is to ensure water does not collect on an area on your property that could potentially damage your home, or create a problem with run off to your neighbor's property causing damage.

In my area, a topographical survey is customary when installing a swimming pool and a patio. Adding impervious materials, such as a patio, changes the dynamics of water containment on the property. Grass or dirt that once absorbed water, is now replaced with an impervious material that does not absorb water.

That topo plan must submitted to the town's engineer for approval. The contractor performing the work, must follow it exactly as shown.

Wow, thank you for all the info, it makes more sense now. Is this something that is typically included in a pool/spa/patio installation or is it something I would have to do on my own and then provide the plans to the architect to include in their drawings?

Depends on the town's/city's requirements. Towns we build pools in require a an updated site plan with the proposed work and any impervious coverage calculations. These are very detailed.

Conversely, some towns accept a hand sketch indicating the pool size and it's location in relation to the house and the property line.

We deal with several engineering firms and we reach out to them for these services, This is part of the service we provide to our clients. We charge for our time to facilitate all this paperwork as it does take time. Clients pay for any permit costs also.

You could research a local engineer to produce a site plan and drainage plan. Yes, you would have to provide the proposed work from an architect, designer, whoever has the pool plan.

Perhaps the pool builder can recommend someone. Maybe the town can also. They may have an in house engineer or some towns contract an engineering firm to review plans, etc.. That should be listed on the town's website in the building dept section.

A current project we are on, I reached out to the engineering firm that generated the site plan when the house was built 5 years ago. Since they had all the property information on file, we just had to submit the proposed pool plan and they did the rest.

Since we use a design program that can generate plan views and 3D, we always submit any renderings when a hand sketch is allowed. It's just the way we do things. Just plain professional.

Thank you again for the detailed info. I will look into this in my area.