A symbol detection scheme based on the Viterbi algorithm that simultaneously processes subsets of 2-D data in the presence of Gaussian noise was recently proposed for binary 2-D optical storage (TwoDOS). In the case of multilevel TwoDOS, a straightforward full-fledged maximum likelihood symbol detector, or even the previous Viterbi-based algorithm, is not an ideal solution due to complexity restrictions. We propose a suboptimum low complexity symbol detector, which still performs within the accepted performance bound for optical storage. We describe the procedures involved in designing and developing a practical symbol detection scheme for multilevel TwoDOS by analyzing the signal values generated by a linear channel model in the presence of Gaussian noise. Our proposed detection scheme exploits the properties of the 2-D data format on the disk, and is flexible enough to accommodate performance and complexity restrictions for optical storage applications.