Engineers with Burns Cooley Dennis (BCD) performed four (4) soil borings this week to determine the characteristics of the soils along Broadway for testing.
Borings were made at depths from 3’ – 6’ deep and the results yielded that there were no heavy, expansive clays underlying the roadbed.
Following the receipt of the findings from Burns, Cooley Dennis Engineers, city leadership has presented the following plan.
Borings from the western half of Broadway Street provided that the underlying materials, down to about a 2’ depth were silty clays (good road building materials), but were extremely wet with moisture contents between 18% – 20% due to the extensive amount of water discharged during the water main break.
Borings on the eastern half of Broadway Street provided that the underlying materials were also silty clays. However that material was found to be much wetter, down to about 4’, with moisture contents as high as 29%. It is believed that the moisture content of the soil was severely impacted due to the location of this soil downhill from the water main break and the resulting pooling of water at this spot.
Optimum moisture contents for this type of material for road construction is 15% with anything greater causing instability/weakness of those soils.
Beginning today, crews from Birdsong Construction began implementing the proposed course of action to remedy the moisture content of soils and repair the roadway.
Beginning Friday, August 18, 2017, crews will focus on the area from Springridge Road to Hampstead Court so that traffic can be placed on all lanes as soon as possible from Springridge Road to Hampstead Court with the area from Hampstead Court to Hampstead Boulevard remaining closed until repaired.
That repair will include removal of approximately 2’ of material on the western end, with suitable dry material brought in to reestablish grade. Once all soils have been replaced, the asphalt layers (6” of asphalt base in 3” lifts with 2” of asphalt surface will be added to provide the driving surface.
Once the three (3) lanes that are torn out now are repaired, the asphalt will be removed on the lane now being used and a similar repair made to the eastbound lane that has remained open. Crews will work to keep access to adjacent businesses open during the repairs.
The more difficult fix will be the area from Hampstead Court to Hampstead Boulevard where at least 4 feet of material will be have to be removed and suitable dry material brought in to reestablish grade and then the same asphalt layers will be added to provide the driving surface.
Due to the wet weather it is extremely difficult to find suitable dry material to be used as backfill. With that being the case crews will be working to “dry” the 2’ of material that is removed in the first phase of construction using 6% hydrated lime. Since dry materials are in short supply, extracted soils from the existing roadbed will be taken to an off-site location for mixing with Lime to quicken the drying process. Soils will them be returned to the site and used once again in the construction process.
Once all repairs are suitably made a final 2” asphalt surface will be applied over the entire street which will match the total of 10” of asphalt which was on the roadway prior to having to be removed.
Currently, only the right eastbound lane of Broadway Street will be open for vehicular traffic. All other eastbound and westbound lanes are closed until further notice. Motorists needing to access Hampstead Boulevard are asked to detour to Broadway Street via the Intersection with Highway 80 near CSpire.
Due to the continued potential for rain over the next week, it is difficult to provide a clear timeline for completion of the project. Crews will continue to work tirelessly to complete the project as weather permits.