Va. Code § 21-405
When the fund in the custody of any county treasurer shall be exhausted in the payment of annual assessments against such lands, or there shall not be a sufficient sum to pay the next annual assessment, such treasurer shall immediately give written notice to that effect to the chairman of the board of viewers of the county in which the petition was filed, and to the clerk of the board, and also to the clerk of the circuit court of the county for which he is treasurer, whereupon the board of viewers for the county in which the petition was filed shall institute an investigation of the tract or tracts of land to determine the market value thereof, and if they shall find the market value of the tract or tracts is not equal to all the future annual assessments to cover its share of installments of principal and interest on the outstanding bonds, they shall proceed to make new assessment rolls on all the remaining lands in the project and increase the sum in sufficient sums to equal the deficit thereby created, and such new assessment rolls shall constitute the future assessment rolls until changed, according to law, and shall be certified to the proper county treasurer or treasurers as herein provided in lieu of the former assessment rolls.
However, the tract or tracts of land which have been so sold by any county treasurer shall continue on the assessment rolls in the name of the new owner, but reassessed upon the new basis, and the drainage tax collected at the same time and in the same manner as other lands, so long as the lands may have sufficient market value out of which to collect the annual drainage tax, and when such lands shall fail to have such value, or shall be abandoned by the person claiming title thereto, the board of viewers may omit the same from the assessment roll; but the lands may in the same manner at any time in the future be restored to the assessment rolls.
Va. Code § 21-405