BuildCraft version: Any (Applies to all current versions)
Forge version: N/A
Link to crash report or log: N/A
Singleplayer or multiplayer: Both
Additional information: This is more of an enhancement than an issue, posted here for discussion.

At current, the quarry will mine all blocks in a layer, skipping lava blocks and any block below lava blocks. This results in the area under the lava (AND where the lava flows) being missed. Because it mines one layer at a time, it will often guarantee the MAXIMUM possible space will be missed as the lava spreads. This also has a secondary issue when it comes time to clean up the mess - there's nowhere to stand. You need to turn off the quarry and branch out from the side to get to the lava sources.

Assume you start with this 4x4 patch of lava

current behavior lets the lava spread out, making the quarry less effective AND making it an ass to clean

MY suggestion is to make it check adjacent blocks for lava, and if an adjacent block is lava then skip that column. The result would look like this:

not only letting it mine more area (since there's no lava spread) but also ensuring there's a lip to stand on so cleaning up the lava is much easier.

on one hand this is a serious mechanics change that needs some discussion, on the other this might be a great performance improver in some cases where there is a lavapool at the top layer in the overworld as well

for full opinions feel free to leave coments here or if you want to chat/discuss them more feel free to join the discord and got to the sugestions channel (https://discord.gg/v4geqgA)

if someone wants to have a go at implementing and submitting a PR so this can be tested out feel free to do so