Septic Leachfields sizing 1

[kmx]

Hi,
I am looking at a project to replace a failed septic system for a park restroom and shower building. The current system treats the showers and sinks greywater separate from the toilets. The greywater system is the one that failed. We would like to size the new system to handle both the greywater and toilet waste. There is currently a 2700 gal septic tank we hope to continue using.

We are looking at using either a traditional pipe with gravel or a newer plastic dome type infiltration system. The soils are silty gravels. This unit has 2 urinals, 4 showers, 5 toilets, and 4 sinks. What guidelines do I use to size these systems?

Also, if excavation of the old leach line is required, what is to be done with the material? Is this considered hazardous waste?

Thankyou for any direction.

 

[snafuman]

The international private sewage disposal code has tables which will give you sizing for facilities including parks and campgrounds. 100 gallon per campsite per day. Day use is 5 gallons per person per day estimating 75 person/acre. Use 10 gallons per person if there are showers in addition to toilets.

These numbers are useful but you can end up with a system which is way too small or too big if you don't temper them with your best estimates of your peak usage days. Some judgement is required.

Percolation tests need to be done to determine the actual rate, don't depend on estimates based on soil types.

The plastic infiltration chambers are a good bet for shallow septic systems. They are much easier to install and can result in a smaller leach field than rock fill systems (depends on your governing codes and what is considered effective area). Once you figure in the cost of rock, hauling, placement, fabric and waste the price of the chambers is very competitive.

Can't answer your question about hazardous waste. If solid from the septic tank have overflowed into the leach field it is possible a landfill may not accept this.