In reference to Mr. Purvis' recent posting, the Census Bureau would like to respond as follows: With regards to the amount (2,445) of invalid TAZ boundaries that are contained within Mr. Purvis' area. Large numbers of invalid boundaries may in fact represent much smaller numbers of actual boundaries since the TAZ-UP software tallies each line segment as a separate failure. Thus, a single invalid line could be responsible for many separate errors. The Census Bureau requires that participants in all of the 2000 statistical geographic programs avoid the use of features that we deem to be unsuitable for use as tabulation block boundaries. Many of these invalid TAZ boundaries are the result of 1990 census block features that have been either deleted or realigned. Most changes to the affected TAZ boundaries will involve a simple adjustment to an adjacent feature that corresponds to the original 1990 TAZ boundary feature. In a minority of situations, the TAZ boundary is on a feature that is not properly identified. In those situations the participants will maintain their TAZ boundaries on those features, and submit a sketch maps to the RCC that provide the proper identification of these features. (Please review the TAZ Program Instructions contained in the Reference Section of the TAZ-UP manual for the complete instructions for how to resolve invalid TAZ boundaries.) With regards to the identification of invalid TAZ boundaries as F84 (2000 statistical area boundary). Originally, all lines with an F84 label were labeled F72 (1990 block boundary). During the processing to create the TIGER/Line 98 files these lines were inappropriately relabeled. These lines are not 2000 statistical area boundaries (census tracts, block groups, census designated places, and census county divisions), but are the invalid boundaries of the 1990 statistical areas. Participants in the Participant Statistical Areas Program (PSAP), just like in the TAZ program, are required to move the boundaries off of these invalid lines. In addition, none of the current boundaries of legal entities (incorporated places and minor civil divisions) are identified as invalid boundaries. TAZ boundaries may follow the boundaries of these entities. However, the boundaries of these legal entities are subject to change. Changes to these legal entities may require changes to the TAZ boundaries. With regards to Mr. Purvis' need to know the 2000 census tract and block group boundaries. The Census Bureau recommends the following to all TAZ participants that need to know the 2000 census tract and block group boundaries. Contact the PSAP participant and request that they furnish you with a copy of the PSAP proposal that they submitted to the Census Bureau, or a copy of the approved plan if that is available. The regional census center (RCC) staff can furnish you with the PSAP contacts for your area. Please DO NOT request the RCC's to provide 2000 census tract and block group boundary information. (The RCCs will supply an addition set of PSAP annotation maps to a PSAP participant that requests the maps for the purpose of furnishing 2000 census tract and block group information to a TAZ participant). Adjust your TAZs where necessary to the proposed or approved census tracts and block groups, and also ensure that your TAZ plan conforms to all requirements including the elimination of the use of invalid boundaries. During the verification phase of the TAZ program, the Census Bureau will furnish participants with TIGER/Line files that contain the approved 2000 census tracts and block groups. Participants can make the necessary changes to the TAZs in order to realign them to the approved boundaries, and then resubmit their TAZ plan to the Census Bureau. Again, TAZ plans must conform to all requirements. (Concurrently, the PSAP participants also will be going through a verification phase of their program in which they are allowed to make adjustments to their census tracts and block groups. Contact them and inquire if are making any changes at this time.) If you have any questions or comments regarding this information, please contact Dave Aultman. His telephone number is (301) 457-1099, and his e-mail address is: daultman(a)geo.census.gov