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The use of mechanical rock grinding to remove rock pinnacles and outcroppings, considered to be navigation hazards in the Mississippi River, was evaluated as a less damaging alternative when compared to the more conventional use of drilling and blasting. The project area contains the federally endangered pallid sturgeon ( Scaphirhynchus albus) and there was concern that intense sound pressure levels ( SPLs) could impact the species. SPLs were measured during production rock grinding ( January 2012, just north of Thebes, Illinois) and compared to those values with SPLs known to cause fish mortality, hearing damage, temporary hearing threshold shifts ( TTS), and stress. The source SPLs' maxima for each time block analyzed ranged from 160-172 d B (re 1 μPa @ 1 m) at frequencies ranging from 100-1250 Hz (1/3-octave band). The highest source SPL maximum recorded for the sound recording session was 172 dB (re 1 μPa @ 1 m) at 1250 Hz. These SPL levels at 1 m from the grinder were well below levels responsible for mortality or noise induced hearing damage. The impact zone for stress (increases in cortisol) was calculated to be within a 9 m radius of the grinder, while the impact zone for TTS was calculated to be within 31 m of the grinder. Considering the small impact zones and continuous noise production during grinding, there is a strong possibility that sturgeon would either avoid or move out of the impact zone. [ABSTRACT FROM AUTHOR]