Drainage - Car Wash 2

[eelssm]

An architect wants to hire me to do the drainage plan for a car wash.

Does anyone know the tasks/items needed that are required to do a drainage plan for a double bay, automatic car wash?

Thanks a lot!

 

[dik]

Lots of floor slope, lots of pipe slope, a sand and grit trap, possibly a grease and oil interceptor and a filtering system if you are going to re-cycle the water. Also check with local municipality to see what has to be done with the effluent.

Dik

 

[msquared48]

* You will need to keep the water effluent in the carwash separate from the extefrior stormwater and discharge it to a sanitary sewer unless the sewer system is a combined one.

* You will need a mechanical oil-water filter system.

* The system will also have to clean out the grit, fines, and phosphates from the water prior to discharge to the sanitary sewer system - similar to a mechanical bioswale.

Mike McCann
MMC Engineering

 

[eelssm]

Thanks for this input.

So, for this effort, it sounds like I need to calculate the worst case amount of water that will need to be processed by the system (separator, lines, etc.) before it discharges into the sewer. Then match this up with a suitable design to make sure it can handle the amount.

It sounds like I need to design a filtering system and link it in with a oil/water separator. Then design the clean effluent to go into the sewer. Does this sound about right?

Thanks for the help!

 

[msquared48]

Yep.

Mike McCann
MMC Engineering

 

[bimr]

As dik suggested, the first thing you need to do is to check with the sewer system where you will be discharging. The requirements of the sewer system may vary greatly from location to location.

The operator of the sewer system will tell you if you have to filter, etc. The typical car wash would not require any treatment, but it will depend on the location and the car wash equipment on your project.

 

[Ron]

I would suggest the following sequence for your systems:

1. Grit separation
2. Oil/Water separation
3. Filtering or treatment before discharge.


There are proprietary package systems for each of these items. Confine your car wash effluent so that you don't cross it over with stormwater runoff on the same site. You don't want the stormwater runoff to run through your treatment systems, and the regulatory people don't want it the other way around.

 

[WL123]

You'll have to work closly with the car wash manufacturer, they have a lot of specifications that have to be met. Channel slopes length of car wash, also the amount of room you need for vehicle turning into the wash.

I don't know where your from, but you might also need paperwork from the state DEP.

The last one I worked on recycled most of the water, we had to go through oil/water separators with a filter in the tank. The water that couldn't be used went to the sewer system. In MA it's regulated locally and by the State.

 

[GoldDredger]

Seems to me the drainage plan would be completely separate from the plumbing inside the car wash. As mentioned before I think many of these car washes have proprietary designs for the inside.

If it is inside the car wash you talking about, sounds more of an MEP item, i.e. fixture units, pumps, sizing of filtering/settling tanks, etc.

If the drainage is outside the car wash, then your talking about a drainage area map and runoff coeficients based on the rational formula. Area and curb inlets, surface flows, etc.

If the site is large enough (and new, rather than infill) you might even need a detention pond, depending on the juristictional requirements.

 

[CPENG78]

As some of you have pointed out, requirements change depending on the municipality that has jurisdiction over your project. Aside from the actual engineering and calculations involved, you may also want to look into fee requirements imposed by the municipality or district as you will be discharging into their system. This may come as a one time fee and/or an annual cost that is correlated to a possible annual inspection of your car wash. Other annual costs may involve testing of water/liquids been discharged and maintenance of any structures in charge of treating the discharge into the municipality's system.

Even though the architect hired you, he or she may not be aware of such fees involved and therefore the client/owner of the car wash may not be aware of such costs. It sounds like we are talking about just one car wash but if the owner is developing a business plan whether for one car wash or 20, this will be valuable information and it will make you stand out from others that may have overlook this information.

 

[oregonaut]

there is a difference between oil-water seperators and grease interceptors. what you need is a grease interceptor. i work for a precaster and we sell lots of grease interceptors for car wash projects. all you need to let us know is the maximum capacity of discharge going into the vault and we will size it for you. go to oldcastleprecast.com and select a location near you.

 

[csd72]

You also need to make sure that the car wash water will not wash onto the streets. This may mean that your stormwater for much of the ground surface still needs to go through the sewer. This can be an issue in some municipalities.