Site Surveying Toys

Chris evaluating site from above.

Last week I joined engineer Chris Rollins and University of Rwanda architecture student Christian "Kara" to do some surveying for a project in Kigali. Chris has done a lot of construction work throughout Africa and has been a great source of information for my UNICEF projects. The construction manual I've drafted is inspired by something similar he produced for projects in South Sudan. During this visit, we were able to play with a number of toys I don't usually have access to. Here's a quick summary with photos of the equipment.

We started off by marking a 10 meter by 10 meter grid pattern over the entire site with flags. Chris brought a Keson MP401E measuring wheel to get the distances, so no need to deal with standard tapes. A measuring wheel makes surveying a site much quicker and easier on the back. We used the same tool to measure distance to services (water, electric, paved road, etc.). It has a pause button on it, so when we'd run up on a large obstacle, we could pause it, move to the side, and restart to continue our reading. The handle folds down and Chris was able to fly with this and the other equipment. Chris is actually pictured in the Keson catalogue using one of these wheels for Engineers Without Borders in Malawi.

Chris using the measuring wheel.

 

Chris centering the bubble.

Once we had the grid laid out, we used a DeWALT DW090PK builders level to take elevations at each point. The builders level was set up at one of our grid points and all other points were measured compared to this point by having somebody stand at the point with the aluminum grade rod to get a reading. Chris will put the points as X, Y, Z coordinates into a spreadsheet, export as comma separated variable file, and import into AutoCAD Civil 3D and create a topographic map of the site, which will later be used to design the building, estimate cut and fill, etc.




Chris on the smart end, Kara holding the grade rod.



Kara trying his hand at the smart end of the level.

Kara about to drop the hammer.

Finally, to evaluate soil conditions, we used a Kessler K-100 dynamic soil penetrometer to get representative samples across the site. The DCP test uses an weighted hammer dropped from a set distance to pound a drive rod into the soil. Once you know the general soil type, the rate of rod penetration is entered into a computer and the CBR (California Bearing Ratio) value for the soil at different depths is given. CBR is a penetration test for evaluating the load bearing capacity of soils originally developed for road construction by the California Department of Transportation. Crushed California limestone is the reference value with a CBR of 100. Our site was getting values between 4 and 40 depending on where and how deep we were testing. These values will influence building foundation design and influence what type of construction can be built on site. This is the first time I've seen the DCP in use and I can think of many times when it would have been useful for one of my projects, especially those that have a lot of cut and fill (almost all projects in Rwanda, "Land of 1,000 Hills"). It would be good to sample un-disturbed soil and then compare that to the compacted backfill to make sure we get sufficient compaction to avoid settling and cracking concrete. The Kessler version we used even comes in a durable Pelican carrying case, perfect for flying around Africa.

Chris explaining the DCP.

Kara dropping hammer, Chris entering values into computer.

All of the survey data collected will be used to develop site plans for the client. Having accurate data means they'll know exactly what they're getting into if they choose to move forward. I've "surveyed" dozens of project in Rwanda, but this was the most thorough to date and had the best toys by far. Thanks Chris and Kara.

Making Gravel

In order to make concrete, first you need aggregate (gravel). At all of my projects in Rwanda, this means getting a delivery of large rocks and chipping away with a hammer until you get a pile of small rocks. They usually set the rocks on a circular pillow made of woven grass (the same pillows they use to carry stones on their heads). It is typically women and older men that get gravel duty, though this time there was also a younger man. This video is from a visit to the Mugombwa refugee camp on November 20, 2014. The aggregate will be used in construction of an early childhood development center (pre-school).

Site Clearing a Big Rock

Site clearing for the new Early Childhood Development & Family Centre in Mbuye Sector, Ruhango District (Rwanda). Unfortunately, there is a big rock in the top part of the site, much of which has to be removed. Very slow and strenuous work. Here's a video showing some of the effort. Not too much mechanical equipment (like jack hammers) in Rwanda.

 

Community Engagement Exercise

On June 28^th, we held a community charrette for a new Early Childhood Development and Family Centre in Mbuye Sector, Ruhango District. The event was organized as part of “umaganda”, the monthly day of service that occurs on the last Saturday of every month across Rwanda. We started with two hours of community work to start leveling the site and prepare it for construction. Approximately 300 people, mostly men, showed up to work each with his own shove, hoe, or rake. The architects and myself had already staked out the site and were around to help direct the work as well as lend a hand with the digging. There is about 5 meters of elevation change from the top of the site to the bottom, which is about 25 meters away. The community is going to remove 2.5 meters from one side and add it to the other side before construction starts. The district will hire a contractor to build retaining walls at the top and bottom of the slope and then UNICEF will execute construction of the facility via an agreement with a partner organization.

  

 

 

After site leveling, we gathered for some dancing and then community engagement activities. UNICEF partnered with Imbuto Foundation to assist with these activities and they started by explaining the idea of the Early Childhood Development and Family Centre, which incorporate health, nutrition, and sanitation programmes to benefit young children, their families, and the community at large. When complete, the centres will belong and be operated by the community, with support from UNICEF and Imbuto for training and developing an operating plan.

Once Imbuto explained the goal of the project, the architecture firm ASA described the current design using a wooden model as a visual aid. Since the site provided is long and narrow, the seven buildings will have to be oriented in an S-shape instead of the circular orientation used in areas with larger sites. The idea is to provide three stimulation rooms for the young children (ages 0 to 6), a covered multipurpose room, demonstration kitchen with storage area, an administration building with two offices, and an “ecosan” toilet that separates solids from liquids and uses both as soil amenities. The entire site is fenced in to provide security and children are provided with custom playground equipment. Rainfall from the roofs of all buildings are piped to a 30,000 liter underground masonry tank, similar to what is commonly used for methane digesters.

 

After hearing of the basic design, community members were broken into small groups and given a series of cards showing related images side-by-side. One card for example showed a built-in masonry stove for the kitchen as well as a free standing metal and concrete stove. Other topics included the finishes on the walls (exposed bricks vs. plaster), ground covering for the central courtyard (exposed soil, grass, brick pavers, or gravel), and even the animal they’d like to see incorporated into the design of the slide (elephant vs. cow). The groups were asked to review the two or four pictures on each card, select the one they would most like to see in their ECD&F centre, and fold the card so that image was face-up. All selections were set on the ground when the group was finished and our team walked around taking photos of the selections and the people in the group. Everybody seemed very excited to be able to contribute to the eventual ECD&F design and there was lots of great conversation about what would be best for their children. There were groups of men, women and children participating in a total of approximately 26 groups.

 

 

Once preferences of all groups had been recorded, we explained how the information would be used to improve the ECD&F design and customize it for their preferences. ASA compiled the results to share with the team and will finalize the design based on this feedback. A copy of the results is included below. Many of the results confirmed what we had already assumed, for example 88% of respondents indicated they prefer a built-in masonry stove over a free-standing traditional stove, 92% prefer the latrine to be located far from the front entrance, and 89% would like to have a dedicated water fountain. There were also some results that may necessitate design changes. When asked about preferred landscaping options, the majority of groups preferred brick pavers, which were not included in any of the initial designs. Almost three-fourths of the respondents preferred an option for playground equipment than what we used in this first round of ECD&F construction. Nearly two-thirds of people would rather have a reed ceiling in the stimulation rooms instead of the exposed clay tile roof we’ve been providing. Perhaps most surprising, the majority of groups preferred the S-shaped site orientation over the circular shape because of the feeling of it being more open and inviting. Our initial thought was to always provide the circular shape unless space constraints forced the S-shape. This valuable feedback will help us tailor the design to the local context while also encourage a sense of empowerment and ownership to the community.

 
The District and Sector officials were extremely happy with the event and took a large group out to a celebratory lunch during which they indicated their excitement about the project and appreciation for employing such a participatory process. We committed to sharing the results of the charrette and having ASA visit the site on a weekly basis to direct the site leveling works. UNICEF and the District representative will visit at least monthly to monitor progress.

Quality Control - Fired Brick Masonry

Working on early childhood development centers in Rwanda has had me inspecting a lot of masonry construction. There was very little quality assurance put in place when the projects began, so for the most part it has been regular inspections, identifying mistakes, demolishing parts of walls, and re-building correctly. Going forward, a robust total quality management plan will be introduced form the beginning, complete with minimum qualifications, written instructions and signage, assigned people responsible for quality, checklists (pre-construction, during construction, and post), mock-ups, etc. Here are some of the most common errors.

 

 

This wall shows what is supposed to be a Flemish bond, but the header bricks (the single brick running perpendicular to the wall) are cut. The masons do this because the dimensions are bad / inconsistent. If they put the headers in so they are flush with the outside of the building, then there are large divots on the inside where the brick isn't long enough. Ideally, the bricks would be long enough to be flush on the inside and outside (as long as two brick widths plus mortar). We've asked them to pre-select the longest bricks and use them for headers and then to center the headers so there is a small divot on either side. Once Identified as a problem, I prepared signage to have on sites as a teaching tool / prompt, but more needed to happen at the beginning of construction.

 

Another common mistake is bad grout. We're getting very inconsistent mixes (bricks can often be easily removed from walls after the grout is dry). One reason is nobody uses lime, so it is just a small amount of cement and some very dirty sand (often not river sand and they haven't been washing). Regardless of the mix, instead of 1 cm mortar joints, we're seeing as much as 5 cm. This is partly because of un-skilled / un-trained masons, but also because of bricks with different dimensions than assumed by the architects. The architects have shown every single brick in their drawings and when foremen see a certain number of rows of brick under the window sill with specific dimensions given, they are increasing the amount of mortar per row to get the bricks to the level shown on the plans. Going forward, we need to clarify that the mortar joint dimensions are critical (1 cm) and that heights and number of brick courses shown on the drawings for some items, like window heights, have some flexibility.

 

Finally, the rebar in masonry buttresses and columns is new for most masons and we've seen lots of problems. Ideally, the two rebar are spaced 10 cm apart, centered over the buttress or column, and the bricks are woven between the rebar. We're getting rebar poorly set in the foundation, so getting bricks between them / incorporating them into buttresses is difficult. Often, the masons will push the two rebar together and treat them as one because it is easier to lay brick around, though much less structurally secure. Even when it is pointed out that rebar are in the wrong position within a column foundation, we have seen the masons bend the rebar at the bottom to get them where they should be so the entire column becomes wobbly as there is slack in the rebar (and the grout isn't very sticky).