MONTE CARLO ANALYSIS OF POINT SOURCE LOADINGS OF OXYGEN DEMANDING SUBSTANCES TO THE HOUSTON SHIP CHANNEL

A Monte Carlo model of point source waste loadings to the Houston Ship Channel was developed using the Texas Natural Resource Conservation Commission's (TNRCC) self-monitoring database for the 410 active point source dischargers. A dry weather point source database was developed and then statistically analyzed to estimate the distribution parameters (mean and standard deviation) for each of the municipal and industrial point sources. The resulting distribution parameters were used in the Monte Carlo analysis to calculate the individual ultimate oxygen demand (UOD) loading for each point source for each iteration of the waste load estimation model.The Monte Carlo analysis of the UOD waste loadings to the Houston Ship Channel demonstrated that even if the municipal waste loads increased by 200% compared to current levels, there is a less than 1 in 10,000 chance that the total allowable UOD loading predicted by the state's steadystate waste load allocation model would be exceeded. At current loadings, the percentiles of UOD loading predicted by the Monte Carlo model were consistent with those derived from the TNRCC self-monitoring database, demonstrating that the modeling approach is reliably simulating the variability of the individual point source loadings. The current median UOD load is about 28% of the allowable UOD load. This evaluation demonstrates that the existing permitted loadings of UOD do not jeopardize continued compliance with the dissolved oxygen criteria for the Houston Ship Channel.