New street construction for Main Street in downtown Fort Morgan, Colorado reduced the street's crown from 8 to 2 percent. The city installed 18,000 square-feet of permeable concrete interlocking pavers (PCIP) from Pavestone for the designated angle parking areas on both sides of the street. The permeable pavers allow average storm rainfall to drain before reaching the curbs. Different color pavers define the parking stalls. Contrasting white pavers were placed to create striping between the parking spaces, obviating the upkeep costs of painted lines.

Located on the northeast plains of Colorado about 80 miles northeast of Denver, Fort Morgan (pop. 11,000) offers residents a beautiful, quaint setting and a historic downtown business and entertainment district. As a "home-rule municipality" Fort Morgan owns and operates all utilities; electric, natural gas, water, wastewater and sanitation. After years of repeated flooding damage to storefronts, the city executed a downtown infrastructure improvement project in 2009. The downtown infrastructure project significantly upgraded important structural and aesthetic city elements critical to the overall downtown experience: roads, sidewalks and surrounding landscaping vulnerable to damage from uncontrolled flooding. The first step was replacing a 40-plus year-old storm drainage system that was significantly undersized for the area.

"The main objective of our downtown infrastructure project was to resolve recurring flooding by replacing the aging underground infrastructure in one of the oldest streets in the city," explained Brad Curtis, PE, the city's public works director. "We elected to incorporate permeable interlocking concrete pavers into the design to help reduce the need for peaks and valleys along the roadway normally required for positive drainage flow. We assumed these would also reduce the potential for icing, while enhancing the downtown aesthetics. We installed 18,000 sq. ft. of permeable interlocking concrete pavement (PICP) from Pavestone for the designated angle parking areas between the street and sidewalks."

In addition to directing rain and melted snow and ice to underground drain collection the PICP design has aggregate layers in the permeable paving that help filter contaminants from the water before discharging into the storm water system.

Curtis explained the city eliminated the eight percent crown on Main Street that had accrued from multiple pavement overlays throughout the years, scaling back to the traditional two percent. The pavers allow for proper drainage for smaller rains without the need for multiple inlets. Lighter rains never bring runoff to the gutter.

Pooling water was a problem with the old parking stall pavement, and ice build up made it difficult for cars to safely back out. With the permeable pavers, water pooling is not a problem. During extremely heavy rains, water may go over the curb line, but it quickly drains.

An impermeable liner below the permeable pavement directs stormwater drainage from Main Street and adjacent parking areas in downtown Fort Morgan to an underdrain that channels to the storm sewer. During extremely heavy rains water may breach the curb, but it quickly drains and is not a constant occurrence as it was in the past.

Incorporating permeable pavers in the street design reduced the need for peaks and valleys along the roadway normally required for positive drainage flow. The permeable pavers also reduce the potential for icing, while enhancing the downtown aesthetics. The colored pavers provide clear separation of the street and sidewalk. While the curb-to-curb width of the street and parking remained the same, the street appears narrower to drivers, which has been a traffic calming effect.

The wearing course of the permeable pavers leaves voids when placed together. The voids, or joints, which typically range from 1/18 to ???(R)???AE? inch, have fine aggregate to allow stormwater to infiltrate. A soldier course of uncut pavers, with joint spacing, borders a concrete strip that separates it from the walkway. The border spacing prevents damage to the pavers. Public works crews vacuum the PICPs once a week, adjusting the sweeper controls to avoid retracting sand from between the pavers.

Fort Morgan sweeps 54 miles of city streets each week with street vacuums. Taking this diligent approach has successfully maintained the integrity of the system, including cleaning the permeable pavers without removing any joint aggregate, which could otherwise jeopardize infiltration. In addition, Fort Morgan is among the leaders of municipalities in Colorado to take the thoughtful foresight to use polyurethane blades rather than steel ones on all of its snow removal equipment. While preserving the city's asphalt and concrete roadways, the polyurethane blades also help avoid scratching or chipping the pavers. Keeping the PICP and other surfaces clean, along with the use of colored pavers for the striping of parking spaces will reduce long-term maintenance costs for Fort Morgan.

The downtown infrastructure work has proved a huge success. Business owners no longer have to spend dreary hours removing snow and ice, and pushing customers' cars from parking spaces. They no longer have to fret a customer might slip and fall, nor worry that flooding will make the street impassable for customers. According to one shop owner, a 45-minute downpour this summer produced 2.5 inches of rain, but caused no flooding, and the pavers quickly dried.

While no permeability testing on the streets has taken place, visual observance shows nearly a 100 percent rain capture, i.e., no runoff from minor storms. City Manager Jeff Wells believes the permeable pavement is a perfect pilot project for the city. "Although this was mainly an infrastructure project, it has enhanced the attractiveness, convenience and functionality of the downtown, while improving pedestrian access and safety," Wells said.