Drupal and Project Watershed

In my "spare" time, I've been doing some volunteer work for Project Watershed, a 501c(3) group that promotes water quality awareness and education in schools in and around Syracuse. A look at their map of sampling locations gives a good impression of the area they cover.
I was introduced to Project Watershed on my first day at the Living SchoolBook and I attended bi-monthly board meetings for the group on and off for my entire eight years there. I enjoyed the intermingling of environmental science, education and the web. Now I am helping them redesign their site for the fourth time since I've been affiliated with the group. I am using Drupal once again for the site. Some of the goals of the project are obvious, while others are slowly emerging out of our discussions:

• redesign the site to reflect its new funding source (the Izaak Walton League of America) and give it a fresh new look
• rearchitect the message and information to best address its target audiences of teachers, student and adult monitors and the general public
• present a single site for accessing both descriptive information and water quality data (in the past a separate database and site were used to manage and display the oodles of data that the group has collected over the past 10-ish years)

One of the biggest challenges of the project will be to display the water quality data that the group typically collects during its sampling events. I've been storing them as normalized data in a separate database, but to do something analogous in Drupal will be a project in itself. I am wondering if I should just leave the data in the existing database and just display it with a custom Drupal module.