Thursday marks one year since heavy storms flooded the region, collapsing basements and making boats the preferred vehicle on town streets, especially in Highland and Griffith. Since then, officials have reviewed what went wrong and what can be done to prevent it from happening again.

They agree the main cause of last year's flooding was too much rain in a short amount of time.

The amount and concentration was unprecedented, Lake County Surveyor George Van Til said.

"That was a 500-year flood," he said. "You could virtually never prepare totally for a 500-year flood."

A 500-year flood is one that has a probability of happening only once every 500 years.

On Sept. 13, the west side of Griffith had 7.39 inches of rain, and the north side had 8.41 inches. Most of that rain fell in a four-hour period that morning, on top of ground already saturated with water from rain in previous days, Griffith Public Works Director Rick Konopasek said.

The Cady Marsh Ditch breached in three spots east of the EJ&E railroad, storm sewers were at capacity and sanitary sewers were at capacity because many of the older homes in town still had sump pumps connected to the sanitary system, Konopasek said.

Since then, the Cady Marsh Ditch Deep Tunnel diversion project has become operational. The 10-inch diameter concrete tunnel diverts stormwater to the Little Calumet River, Konopasek said.

The project also directly protected Highland, Munster and possibly Dyer from even more severe flooding in recent rains, he said.

"The tunnel diverted a mass quantity of water from flowing west into these communities," he said.

Griffith also completed reconstruction of the Genis pump station, which is connected to the Brinwood pump station. Both stations are connected to a new diesel-powered generator in case there is a power loss, Konopasek said.

Before last year's flood, the town had rebuilt two of the three pumps at its Landmark storm station. Since then, it has completed five storm line connections, which means existing storm sewers are connected to other nearby storm sewers. It should relieve pressure off the lines and alleviate street flooding in problem areas, Konopasek said.

Rain gauges reported 7.94 inches fell on the east side of Highland during the storm, Town Manager Richard Underkofler said.

"We would have just as much trouble if it happened again," he said. "No community in America could afford a system that could accommodate that much rainfall."

The town retained DLZ of Hammond, an engineering firm, to study its sewer systems with recommendations for system maintenance, property owner responsibilities, and cost estimates for sanitary and storm system improvements that will prevent future flooding and sewer backup.

Also, Highland proposes to spend more than $14 million during the next five years for sanitary and storm sewer work identified in the 2007 Sanitary District Capital Improvement Plan.

And, $3.5 million in bonds have been approved to help underwrite expenditures for sewer system improvements, Underkofler said.

Highland's interior drainage systems, including stormwater pipes, ditches and detention facilities, were unable to accommodate the exceptionally large volume of rainfall during the 2006 floods, he said.

Underkofler also said older storm drainage piping systems were designed to accommodate five- to 10-year storm events.

Systems constructed in more recent years include stormwater detention facilities designed to accommodate 100-year storm events. The heaviest amount of rain last year fell in older sections of town where there are few stormwater detention facilities.

The town reported 1,789 housing units had water damage from flooding, sewer backup or hydrostatic pressure, including 163 units with structural damage.

Since then, a new pump station is complete at North Drive, which has increased pumping capacity to handle a 100-year rainfall event and serve the area north of Ridge Road, Underkofler said.

And to reduce infiltration and inflow, Highland is offering grants for a portion of the costs to reimburse property owners who must disconnect foundation drain sump pumps, downspouts and stormwater drains from the sanitary sewer system in neighborhoods where storm sewers are available.

"The new pump stations and the bypass of the (Cady Marsh) Ditch made an extremely big difference," Public Works Director John Bach said. "We are continually televising sewers to make sure there are no blockages. We always have plans to make system improvements."