I don't have a water report but Baltimore, Columbia and Ellicott City's water comes from the same source as Heavy Seas. I contacted the brew master and he responded with this.
"We use a blend of salts, but to answer your question...yes we use Baltimore City municipal water. The salts we use are Calcium Sulfate and/or Calcium Chloride."
I take it a step further by filtering the water first with this.
I've attached the water profile in this PDF. I live in Fed Hill, I think same water supply as HoCo and Heavy Seas. Also, I too only adjust water with Calcium Chloride and Calcium Sulfate (Gypsum). Occasionally, I will add in some backing soda when using roasted grains to keep my mash pH from going too low.
The filter my water through a carbon block filter. The test results were straight from the tap, though. Although, a filter shouldn't have any impact on minerals, etc.
To make a very pale ale, SRM 1-6, add about 2-4 grams (1/2-1 teaspoon) gypsum per gallon of mash water, which will raise the calcium content of the water by 60-120 ppm; or you can add 4-6 grams (1-1.5 teaspoons) of Calcium Chloride for the same effect (raises calcium by 80-120 ppm).
To make a darker beer, you'll need to raise the alkalinity. Add either Chalk (1.5-3 grams, or 3/4-1.5 teaspoons) or Baking Soda (8-12 grams or 1-1.5 teaspoons) to raise the residual alkalinity by about 180-200 ppm of bicarbonate.