In a large mixing bowl, combine the water, pickle brine, active sourdough starter or levain, and olive oil. Stir until the starter is evenly dispersed. Add the bread flour, whole wheat flour, salt, dried dill weed, garlic powder, and thoroughly drained and dried chopped dill pickles. Mix by hand, with a dough whisk, or in a stand mixer until no dry flour remains and a shaggy dough forms. Cover the bowl and let the dough rest for 30 minutes to allow the flour to hydrate.

Perform three sets of stretch-and-folds or coil folds, spacing each set 30 minutes apart. Use lightly oiled hands to prevent sticking, and handle the dough gently to avoid tearing the developing gluten. After the final set, cover the bowl and continue bulk fermentation at room temperature (70–75°F / 21–24°C) until the dough has increased in volume by approximately 50%, feels airy, and shows visible signs of fermentation. Allow approximately 6–8 hours for bulk fermentation, adjusting as needed based on starter activity and room temperature rather than relying solely on the clock.

Transfer the dough to a lightly floured work surface. Gently preshape it into a loose rectangle, taking care not to press out all the accumulated gas. Let the dough rest uncovered for 20 minutes to relax the gluten before final shaping.

Shape the dough into a snug sandwich loaf by gently flattening it into a rectangle, folding the sides inward, and rolling it into a log approximately the length of the Pullman pan. Place seam-side down in a lightly greased or parchment-lined 9 x 4 x 4-inch (23 x 10 x 10 cm) Pullman loaf pan. Cover loosely and proof at room temperature for approximately 1½–2½ hours, until the dough is visibly puffy and has risen noticeably in the pan. Alternatively, refrigerate the covered dough for 8–12 hours for an overnight proof. If refrigerated, allow additional room-temperature proofing before baking if the dough has not risen sufficiently.

Preheat the oven to 375°F (190°C). Bake the loaf uncovered, without the Pullman pan lid, on the center oven rack for 40–45 minutes, until the crust is golden brown and the center registers approximately 200°F (93°C) on an instant-read thermometer. If the top begins browning too quickly, loosely tent with aluminum foil after approximately 20 minutes. Baking time may vary depending on the oven and loaf pan.

Remove the bread from the oven and carefully turn it out of the Pullman pan onto a wire rack. Allow the loaf to cool completely for at least 2 hours before slicing. Cooling allows the interior to finish setting and prevents a gummy texture when cutting the sourdough sandwich bread.