; (B) within which are located a military installation or other facility relating to national security concerns; or (C) that have a population that is highly vulnerable to urban flooding and have an uneven capacity for flood mitigation and response efforts resulting from socioeconomic factors. (g) Amount (1) Considerations In determining the amount of grant under the pilot program under this section, the Administrator shall consider the population of the grant recipient, which may be considered in terms of the tier under subsection (e)(2) of the recipient. (2) Federal share The amount of a grant under the pilot program under this section may not exceed 75 percent of the total cost of the activities under subsection (b) to be carried out using the grant amounts. (h) Duration The Administrator shall require each recipient of a grant under the pilot program under this section to complete the activities under subsection (b) to be carried out using the grant amounts before the expiration of the 18-month period beginning upon the initial receipt of grant amounts under the pilot program. (i) Use of census data The Administrator shall make all determinations under the pilot program regarding population using the most recent available data from the decennial census. (j) Grantee reports to FEMA Each recipient of a grant under the pilot program under this section shall, not later than the expiration of the 30-month period beginning upon the initial receipt of any such grant amounts, submit to the Administrator a report that describes— (1) the activities carried out with amounts from the grant; (2) how the activities carried out with such grant amounts have met the objectives described in subsection (b)