February 11, 2015 Dear Sir/Madam, I manage a group of computer modelers who run simulations of the physical, chemical, and biological processes that occur in the rivers impacted by Philadelphia’s pollution. As a utility which relies on our local rivers for drinking water, these models are critical to our mission to protect public health and promote environmental sustainability. We were extremely fortunate that Saadat Khan served as our co-op intern from September 2014 – February 2015. Saadat was an extremely bright and talented young engineer who contributed meaningfully to our group. He was diligent and persistent in all the tasks assigned to him. His strong attention to detail aided us in quality checking our model input files, and he discovered more than a few important errors which we then repaired. He completed a number of programming assignments in both Matlab and R. His work encompassed creating statistical summaries of pollutant loadings, and automating a time series analysis method that elucidated the groundwater component of local stream flow. Besides advancing his Matlab and R programming skills, Saadat also learned ESRI ArcMap software and created several maps of a dye study we performed. Saadat has a bright future ahead of him. His warm personality and maturity made him an enjoyable presence to work with on a daily basis. I highly recommend him for acceptance into your engineering program. Please contact me at 215-685-4960 or josef.kardos@phila.gov if you have any questions. Sincerely,

Josef Kardos, PhD Manager, Water Quality Compliance Modeling Office of Watersheds Philadelphia Water Department

The ARAMARK Tower 1101 Market Street Philadelphia, Pennsylvania 19107-2994

Howard M. Neukrug Commissioner