eHT developed a hydraulic computer model for the City of Albany with Innovyze’s H2OMap Water GIS Suite 8.0, based on available water distribution system maps, “as-built” construction plans, operational data provided by City Staff and field survey data. The model was created based on several assumptions including the following:

• It was determined that modeling only water lines 6-inches in diameter and greater was necessary to evaluate the interaction between the two tanks and the general movement of water across the system.
• Information provided by the City indicated a total of 1,200 service connections on the system. Each water service connection on the system was assigned a demand of 1.0 gallon per minute (gpm). Demands were applied at nodes across the system, with higher concentrations placed in the more populated areas as determined using aerial photographs.
• The model was set up with four different demand scenarios including low flow (0.10 gpm/conn.), average daily flow (0.25 gpm/conn.), maximum daily flow (0.45 gpm/conn.), and the Texas Commission on Environmental Quality (TCEQ) peak hour demand of 1.50 gpm/conn. While these demand scenarios are not based specifically on current water use records, they are a reflection of typical water use patterns in smaller rural communities.
• The actual operational settings for the pumps and tanks were incorporated into the model for greater accuracy. These settings included water surface elevations in the tanks, manufacturer pump curve information, and the pump on/pump off settings currently programmed into the system.

The modeling observations also highlighted potential water quality issues both in the ground storage tank (GST) and in the distribution system immediately downstream of the GST.  These issues can be attributed to the common inflow/outflow piping configuration, as well as to the large volume and low turnover rate present in the GST. Once treated water enters the distribution system, it has a limited “shelf life” before the disinfectant residual begins to decline, which can result in microbial regrowth within the tank and/or distribution system, creating “stale” water.  Dead-end lines and other isolated areas within the system tend to have longer water ages, often requiring periodic line flushing and/or additional chemical injection points to maintain the required disinfectant residual in the system.

eHT recommended replacement of inflow/outflow piping on the EST and GST, replacement of various water lines and transfer of the high service pump station control to the GST.