LARE Section 3 cheat sheet

Design-bid-build: owner contracts separately with designer and contractor; lowest responsive bidder wins; longest duration, clearest single point of responsibility for design.

Design-build: single entity holds design and construction risk; owner states performance criteria; faster delivery, fewer owner change orders, but reduced owner control over design detail.

CM at risk: CM holds a GMP and subcontracts trade work; owner gets early cost input and schedule overlap; CM carries construction risk above the GMP.

Agency CM: CM acts as owner's adviser with no construction risk and no GMP; fee-based, so owner retains all cost overrun risk.

Pay items are measured by unit (CY, SY, LF, EA, AC); lump-sum items are paid on percentage complete; unit-price contracts shift quantity risk to the owner.

Retainage commonly 5-10% of each payment; released at substantial completion or per contract; retainage reduces contractor cash flow and raises bid prices.

Critical path: longest continuous path through the network; zero float; any delay on it delays project completion unless the schedule is compressed.

Float (slack) = late start minus early start = late finish minus early finish; total float is shared, free float is path-specific.

Change order vs. construction change directive: a CCD directs work before price agreement; a change order is a signed agreement on scope, price, and time.

Slope in percent = (rise ÷ run) × 100; a 2% slope drops 2 ft per 100 ft. Slope ratio 4:1 equals 25%; 3:1 equals 33%.

Maximum accessible running slope for an accessible route is 1:20 (5%); steeper than that it is a ramp, requiring landings and handrails.

Accessible ramp: maximum running slope 1:12 (8.33%), maximum rise per run 30 in., landing at top and bottom at least 60 in. long.

Cross slope on an accessible route: maximum 1:48 (about 2%); steeper cross slopes cause wheelchair drift and are a common compliance failure.

Universal access clear width: 36 in. minimum continuous; 60 × 60 in. passing space at intervals where width is less than 60 in.

Drainage: minimum 1-2% slope on paved surfaces, 2% on turf; swales carry concentrated flow; use level spreaders to convert concentrated flow to sheet flow.

Cut and fill balance: sum cut volumes and fill volumes separately; net difference times a shrinkage or swell factor gives haul or borrow volume.

Contours crossing a slope run perpendicular to the fall line; closely spaced contours mean steep grade; contours that touch or cross indicate an overhang or error.

Sun angles: summer sun is higher and north of east/west; winter sun is lower and south of east/west; use these to size overhangs and shade.

Concrete: 1:2:3 cement:sand:aggregate by volume is a common site mix; water-cement ratio governs strength and durability - lower w/c means higher strength.

Concrete cure: keep moist and above about 50°F; 7 days for normal cement, 3 days for high-early-strength; cold weather slows strength gain.

Asphalt pavement: base course, then binder course, then surface course; compaction in lifts, with a prime coat between base and asphalt.

Segmental retaining wall: geogrid reinforcement length typically 60-70% of wall height; granular drainage fill and perforated drain at the base.

Wood preservative: pressure-treated lumber for ground contact; stainless or hot-dip galvanized fasteners to avoid corrosion from preservative salts.

Specification divisions follow MasterFormat: Division 01 general requirements, 02 existing conditions, 03 concrete, 31 earthwork, 32 exterior improvements, 33 utilities.

Drawing set order: cover, general notes, demolition, site plan, grading and drainage, planting, details, sections, schedules.

Shop drawings are contractor-prepared, showing fabrication and installation detail; submittals include product data, samples, and mockups.

Punch list: items of incomplete or defective work identified at substantial completion; the contractor corrects them before final completion and final payment.

Rational method: Q = CiA; Q in cfs, C is a runoff coefficient (0-1), i is rainfall intensity in in./hr, A is area in acres.

Runoff coefficients: lawn 0.15-0.35, gravel 0.35, asphalt 0.90-0.95, roofs 0.90-0.95; composite C is area-weighted.

Time of concentration: the time for runoff from the most hydraulically remote point to reach the design point; it sets the rainfall intensity used in the rational method.

Detention vs. retention: detention holds stormwater temporarily and releases it slowly; retention holds it permanently (infiltration or permanent pool).

Pre-development vs. post-development peak flow: detention must be sized so post-development peak discharge does not exceed pre-development peak.

Bioretention: engineered soil media, surface ponding depth, underdrain, and overflow; treat the water-quality volume first, then attenuate larger storms.

Grass swale: side slopes 3:1 or flatter, longitudinal slope 1-4%, check dams to slow flow and promote infiltration.

Manning's equation: V = (1.486/n) R^(2/3) S^(1/2); n for concrete pipe about 0.013, for grass channels 0.03-0.04.

Storm sewer design: minimum pipe slope typically 0.5%, minimum velocity 2 ft/s to avoid sediment, maximum velocity about 10 ft/s to limit scour.