During soil removal work, the operator of a Cat 330C excavator dumps soil into a truck. Approximately 3,000 cu. yd.
(2,300 cu m) of soil was removed
while preparing the base of
the construction site for
the new addition.
Challenged by some extreme topographical conditions and tight, urban space while battling a hearty, Minnesota winter, RJM Construction and its sub-contractors are now making up for lost time to complete an addition for the Hmong College Prep Academy (HCPA), a popular and growing St. Paul based charter school.
Forging through snow and cold, ironworkers recently completed the steel skeleton for the new building and are now hanging decorative metal sheeting for the outside walls while other crews are moving into the interior phase of construction.
Though tough soil and noise management during sheet piling operations along with sub-zero temperatures and snow slowed construction a bit, the contractor is closing in on the half-way point of the construction schedule.
Crews are catching up on lost time and are still shooting to open the new addition in time for the start of school this September, said Mike Seigley, construction superintendent of RJM Construction.
RJM Construction won the $12.7 million contract to build the three story, 78,000 sq. ft. (7,250 sq m) addition to the school. With two offices in Minneapolis, one in Denver and one in Phoenix, the company specializes in general contracting, construction management, design/build and pre-construction services.
When RJM crews and their excavating contractor Carl Bolander and Sons Company based in St. Paul, Minn., hit the site in early October of last year, they faced some daunting site conditions that complicated the construction and limited options for site access and staging areas for materials and equipment.
Tucked away on a small piece of land near the Minnesota State Fairgrounds, the main entrance to the school on the building’s south side sits across the street from a sprawling school bus terminal. Along the north side, a steep hill rises 25 ft. (7.6 m) above street level to a residential neighborhood packed with homes and apartment buildings.
On the other two sides, it sits between another small, charter school and an asphalt lot on the other end set aside for staff and visitor parking located near a high volume, four lane, city arterial.
With the footprint of the building taking up most of the construction site and no space to work with, the contractor rented several hundred ft. of parking lane space from the city of St. Paul on the top side of the bluff and on the street below for equipment staging areas and deliveries.
Since construction began in early October, 2012, construction has been going well despite the challenges and battling the cold and snow, according to Seigley.
“It’s been going pretty well though it’s been a challenge,” Seigley said. “We might be a little behind but we should be able to make up for it now that we’re pouring the floors and getting the exterior going, we’ll make up some time so the completion date still stands.”
A fast growing student population sparked the need for the addition to the charter school that focuses on a college prep program. Established in 2004, the original, 78,000 sq. ft. (7,250 sq m) building quickly outgrew its capacity. Starting with a student population of 200, it has now grown to 930 and has modular classrooms on the school’s parking lot to keep up with the fast growth.
The new addition will increase school capacity to 1,500 students. At the same time, it will eliminate the need for the modular classrooms and add parking capacity on the lot at the building’s west side, said Pao Yang, chief operating officer of the school.
Teaching kindergarten through the senior level of high school, the new addition under construction on what was formerly a spare parking lot for the school, will double the school’s size and add 28 classrooms.
The new space also will house a second lunchroom, a second gymnasium, a new performance space featuring a high tech auditorium/theater with a seating capacity for 500 guests and a state of the art technology lab and library according to the school Web site.
Outside, a canopy covering a recessed opening between the existing building and the new one will serve as the main entrance. On the third level above the canopy, several hundred sq. ft. of glass will cover the building and bring daylight into the open atrium down to the first floor inside the lobby and to the doors of the new auditorium.
On the third level, an emergency exit featuring twin doors will lead to a pair of short bridges outside to span the gap between the school and the top of the hill on the north side of the building.
Also included in the contract are interior renovations to the existing building and the construction of a much smaller addition on the west side of the building that will house an upgraded, state of the art commercial kitchen.
The proposed expansion also will feature a number of green energy initiatives.
A school press release stated that “compared to a typical school design, the HCPA addition will reduce overall power consumption by 10 to 15 percent, reduce water use by up to 40 percent, capture and clean 100 percent of storm water that falls on the site, and use environmentally friendly interior materials to promote the health of students, staff, and faculty.”
The students are seeing their new addition take shape and have been following the construction closely.
“The students are very excited about the construction but the noise bothers them sometimes because it is so close,” Yang said. And since the addition will house mainly the high school students “all the students are excited about getting a new auditorium because we don’t have one for them now and they will also be getting a new gym and a new lunchroom.”
When construction began last October, Bolander crews rolled onto the site to cut down the trees and thick brush covering the plunging hill side.
Trucking in a Cat 330L backhoe, a Cat D6T dozer and a Komatsu backhoe, Bolander crews spared no time and in less than one week cut down 50 to 70 trees and cleared out a thick covering of mostly Buckthorn trees covering the hillside.
With the trees removed, the Cat dozer tracked up and down the 60 percent grade and pushed the remaining stumps to the base of the hill while the Cat backhoe began tearing away at the asphalt cover of the site.
Running into soil laced with a petroleum based substance below the asphalt, the backhoe operator had to dig out the past to build for the future. Digging deeper into the ground before reaching clean, native soil, the bucket hooked the rusting chassis of an old car along with several tires.
Speculation at the site was that an auto repair service of some kind once occupied the same space and that “back in the day” as Seigley said, it was most likely that the owner of the property buried the junk just to get it out of sight.
From what was left of the chassis, best estimates of its age go back more than 50 or 60 years, Yang added.
Eventually, approximately 3,000 cu. yd. (2,300 cu m) of contaminated soil was trucked out of the site.
Along with the contaminated soil found at the base of the site, the plunging hillside, tight site and noise management posed the other challenges for RJM and Bolander crews.
“We obviously had the tight site with our building at 10 ft. (3 m) off the property line so we’re right there [at the street],” Seigley said. “We also had the sheet piling operation which is a noisy process and we had to keep that down to a minimum.”
The hill on the north side left the engineers no choice but to design a sheet piling soil retention system with tiebacks to secure the hill.
After seeking a noise variance from city of St. Paul officials, RJM brought in a third party inspection team to monitor noise levels and potential seismic disturbance caused by the vibratory effects of the sheet piling work.
Attaching a MKY V-30 vibratory hammer to an American 5299 50 ton (45.3 t) crane stationed on the top of the slope, Bolander crews began vibrating in the first sheets of piling. As the sheet piling progressed, a Komatsu backhoe sitting on the back side of the wall began digging out the first of four separate bench layers to make room for the tieback installation operations.
Dropping in a drill and pumping concrete through the tieback tubes, crews drilled a series of four rows of tiebacks to anchor the retention system. Crews installed approximately 8,500 sq. ft. (790 sq m) of sheet piling and 300 tiebacks to anchor the wall.
Though sheet piling crews hit a cobble layer roughly half way into the ground that slowed the placement of the sheet piling, Seigley said “generally, they [the crews] were successful in making good time and we never exceeded the threshold for safety practices with either the seismic or sound levels.”
Passing into the new year, brick masons began laying blocks for the interior auditorium, a stair well and elevator shaft.
As the brick work continued, cold and snow blew into Minnesota’s capitol city in mid-January at the same time as truck loads of steel began arriving at the construction site from Camelot Metals Inc. located in Roseville, Minn. Picking steel at times in sub-zero temperatures and through a series of nuisance snow falls, iron workers from J and H Erectors with an office in Buffalo, Minn. bolted in the last piece of steel for the school addition in late February.
“The steel work went really well. They, [the ironworkers] worked ten hour days and Saturdays to meet the schedule,” Seigley said. Though ironworkers took a couple of days off during the more extreme winter weather conditions, they placed approximately 180 tons (164 t) of steel in just more than four weeks.
While a stubborn winter kept its hold on the region through March, RJM crews moved into the interior of the structure with deck work, siding and mechanical installations.
Concrete crews recently poured 42,200 sq. ft. (3,925 sq m) for the second and third floors of the addition. Seigley is waiting on Mother Nature for now to spring the frost from the ground before starting any concrete pours for the first floor which will take a little longer because of the multiple steps in the auditorium.
“Once we get the ground thawed, we’ll get the mechanical into the ground and then we’ll pour right behind it and then we’ll pour the auditorium seating. It’s going to take a little longer on the first floor because of the multiple pours,” Seigley said.
The siding work quickly follows.
“Once you get the concrete load to that building, you get the deflection out of the steel or bar joists. Then it’s in a state where we can actually pin the exterior walls to the building and get the roof on,” Seigley said.
Using a half dozen JLG cranes, crews are now installing the metal siding to the building while crews inside ramp up to install all the mechanical, electrical, plumbing and interior finishing in time to open the doors to the addition for the upcoming school year.
“We’re looking at roughly 90,000 sq. ft. (8,370 sq m) of finishing work. It’s a lot of work. It’s going to take a little miracle to get it done,” Seigley said. “Yet, we’ll get it done, we always do.”