PARK AND CEMETERY. 
67 
DEERING'S OAKS, CONCRETE BRIDGE, PORTLAND. ME. 
$22.10; mixer (transporting), $12. Total, 
$3,816.74, or $883.26 less than estimated 
cost if contracted. 
The quantity of concrete was 435 cubic 
yards. For the arch a mix of 1 :2 :4 was 
left open under the floor to relieve weight 
on foundations. Floor slab was reinforced 
with steel rods and “Hy-Rib.” Balustrade 
rails and posts were poured in place. The 
entire structure was finished by rubbing 
surfaces with carborundum brick. Conduits 
were placed for electric wiring and lamp 
posts of special design erected . on piers. 
The work was designed and supervised by 
Engineer William O. Thompson of the de- 
partment and built under contract by H. P. 
Converse & Co. of Boston, Mass. The 
total cost of the bridge was $3,547.04. 
The concrete for the structure was mixed 
in the proportion of one part (Alpha) 
Portland cement, two parts sand and four 
parts broken stone. For work not exceed- 
ing 12 inches in thickness the maximum 
size of stone used was 1 inch ; for work 
exceeding 12 inches in thickness the max- 
imum size of stone used in concrete mix 
was 2p2 inches. Quarry stone was used in 
piers and abutments when such stones were 
completely surrounded by not less than 2 
inches of concrete. 
The forms were made of planed lumber, 
tongued and grooved, and all inside sur- 
faces next to concrete were coated with 
paraffine oil to prevent concrete from ad- 
hering to forms when stripped. 
Steel used for reinforcement was of 
square section, twisted cold. Three-quarter 
inch rods were used in the arch ring, 
used, while for the sidewalks this was 
changed to 1 :3 :7. The entire mass was 
left in the forms for sixty days. 
About 800 cubic yards of back filll was 
placed and water settled. This was shipped 
in by teams at $6 per day. Final cleaning 
up and completion will be done this sum- 
mer at an added cost to figures given of 
about $300. 
An Interesting Concrete Foot Bridge. 
The Deering’s Oak bridge in Portland, 
Me., was built to replace a wooden struc- 
ture and was designed for foot travel only. 
The length, including approaches, is 80 
feet, with a 40-foot span and a clear width 
on floor of 8 feet 1 inch. The material 
underlying the foundation is soft blue clay. 
The concrete is reinforced throughout and 
the space between spandrel walls over the 
arch and in the abutment approaches was 
SECTION OF INTERLAKEN BRIDGE. 
