The capital investment required for the development of TREDA (Tumen River Economic Development Area) depends upon the set of parameters. We analyzed the relationship between the required investment and sets of basic parameters of the supposedly integrated TREDA: targeted per capita income, population (size or growth rate), depreciation rate of the capital stock, and the introduced ODA in conjunction with the assessment of the ‘country’ risk. Current TREDA economy has a population of 4.4 million, with an average income of approximately 1, 000, endowed with an attributed 0.6 billion dollars of ODA outstanding and 9.8 billion dollars of capital stock in an area of 54, 704 km². For this economy to grow to 2, 500 in per capita income in 30 years under the assumptions of 3% annual population growth rate and 8% ODA (outstanding) growth rate, the GDP must grow at 6.1%. This requires a total gross investment of 92 billion dollars, out of which infrastructure investment will be 24 billion dollars. Required capital investment depends on a combination of various economic parameters. It will be 121 billion, 100 billion, and $93 billion, respectively, if population growth rate is 4%, depreciation rate is assumed to be 6% and ODA growth rate is 9%, in tern. We speculate that for the city is to be viable against expected strong backwash effects from existing big cities in the vicinity, the planned core city must be of rank one or two in population size. This implies that this envisioned development mucleus must have a population of 4.0 millions as rank 1 or 1.5 millions as rank 2 in 30 years when calculated from the current rank-size distribution of cities in the TREDA. In our calculation, TREDA will be allowed to absorb six to nine billion dollars of ODA for its ‘public sector’ to maintain its ‘country risk’ at a healthy twenty to thirty percent of its GDP. The extra ODA investment reflects the TREDA's favored position to be allowed by the respective countries due to the external economy, reduction of income differentials within the respective countries, and the assessed value of strengthened security among the concerned countries.