It's the environmental protection agency. 

How do you prevent or insure against environmental contamination.   

I believe that I can rehab this place for 30K.If I’m right, I can flip it for 35K profit, or buy and hold for an ultimate cash on cash between 10 and 15 cap.What are the environmental risks involved with railroad sidetracks (I’m thinking repair and refueling, possibly herbicides or cargo)?

There are going to be some obvious and not so obvious problems, especially in the environmental area. 3)If you are serious, get someone out there that does fire restoration construction.

Environmental bills I believe are under Housing, but no one at housing will be able to help You need to go to the environmental control board. 

In Texas for example there are restrictions that there can be no more than 7 homes per acre as a means to ensure that septic will not cause pollution (some counties restrict one septic per acre, but you can get around this with a larger commercial system for multiple homes...).  

The state Department of Environmental Quality and the Oregon Health Authority plan to announce that DEQ data indicate a monthly average of 49 times the state air-safety benchmark level for the neurotoxin and carcinogen cadmium, and 159 times DEQ's air-safety goal for the carcinogen arsenic."

Environmental risk is considerably higher too.....failed tenants frequently leave behind nasty messes.

I know many of you may think how can you do that ,well fortunately  we happen to be in an extremely relaxed lending environment ,ive been in this business for 30 years and this is only the 2nd time i;ve seen real estate lending this relaxed ,for you old timers ,i know you can remember when their was no seasoning of title , in that period i was able to acquire 20 properties in 6 months ,moving right along ,heres the formula 1) find a property that needs a rehab in a b or c+ neighborhood,determine that after the rehab you will be at a 65 to 70% arv,next after you've acquired and rehabbed the property refinance it ,heres the example ,$45,000 purchase ,$30,000 rehab ,finished value $125,000,now you have a couple of options,you can refinance the property in 30 days at a 70% ltv,or you can refinance it later at an 80% ltv in 90 days,,using the example at 70% your cash out is $87,500,lets assume that your settlement costs were $8000 per transaction for the intial purchase and refinance,this equals $16,000 ,your cash out is $12,000,which leaves your out of pocket at $4000,this would be your total outlay,assuming that you rented the property and had net revenues of $500 a month your total return yearly would be $6000 monthly,your roi is 50%,now if your roi wasn't this high ,let say 30% annual return ,i don't think you would be too mad ,however you have another option and if you are not in a hurry you can refinance in 90 days at 80% ,when you refinance your cash out would be $125,000x80=$100,000-$75,000=$$25,000-$16,000 would be $9000,,so the $64,000 question would be how much did this really cost you,rinse and repeat this formula over and over  and you will be a happy camper              

No affiliation, but https://www.oeservices.net/environmental-site-asse...https://www.wh-m.com/service/phase-1-environmental...I have used Terracon for my clients and very pleased with their work in Texas.https://www.terracon.com/services/environmental/environmental-site-assessments-and-investigations/