Drainage report

I am looking for assistance with developing a Drainage Report (with calculations) for the following project description:
The proposed development is the conversion of the existing open drain ditch to a piped storm sewer system.  We have prepared a topography survey of the area and a draft set of construction plans including plan and profile drawing of the proposed 42” reinforced concrete pipe, approximately 900 feet along the length of the existing ditch.
Project is located in the existing 30 foot drainage ditch right of way (see attached) along the north boundary line of Wildrose Estates Subdivision in Cameron County, Texas, which is the portion of Wildrose Lane in between Center Dr. And El Paso Rd. In Brownsville, Texas.   
We are in need of Drainage Report including Pre and Post Runoff Calculations and Hydraulic Grade Line and Energy Grade Line calculation for the proposed storm sewer pipe.
If this is something you can produce, please advise of the following:
1)    How long will it take for you to complete the job.
2)    What is your fee?
3)    Will you provide native files?
I look forward to hearing from you soon.
Thank you.