Rinse all of the vegetables well, including the kombu.
In a large stockpot, combine all of the vegetables, kombu, and spices. Fill the pot with the water to 2 inches below the rim (at least 8 quarts), cover, and bring to a boil
Remove the lid, turn the heat to low, and simmer, uncovered, for at least 2 hours (my broth simmered as long as 8 hours).
(As it simmers, some of the water will evaporate. Ad more as you go if it looks like it's getting low in comparison to the veggies)
Also, taste as you go. The richness of the vegetables will become more and more pronounced.
Strain the broth through a large, coarse-mesh sieve (remember to use a heat-resistant container underneath)
Let cool to room temperature before refrigerating or freezing.