sewage smell in sump pit

I get A sewage smell coming from the sump pit when it rains real heavy the water in the pit at that time is also very cloudy. A day or two after the rain stops the smell and the cloudy water go away. I have a septic system, there is no standing water or wet areas over the field I get the tank pumped every year. I installed a bathroom in the basement 2 years ago with a new sewage pit with ejector pump.