Mass Grading in the Boulder Valley

Grading decides whether a Boulder Valley project drains, stays dry and clears inspection, and it happens before anything visible rises from the ground. The 389 acre Redtail Ridge land in Louisville is a useful reminder of how large and how layered these sites can be. It was annexed as a corporate campus parcel, and the roughly 1.6 million square foot campus on it was demolished after a new owner bought it in 2008, so the earthwork there starts with finding out what the earlier use left in the ground.

That is how we approach mass grading across the metro. We strip and stockpile topsoil, build a single survey control network for the whole job, cut and fill in tested lifts, and leave a stable, proof-rolled surface for foundation and paving crews. The aim is a pad that sits at the elevation the civil drawings promised, drains where the plan says it drains, and does not move once the slab goes down.

The work suits developers assembling a parcel in Longmont or Louisville, owners clearing a former industrial site for a new building, and public agencies preparing ground for facilities. It sits right behind site development and utilities in our sequence and ahead of everything vertical, which is why we like to be involved while the grading plan is still a drawing.

What the earthwork package includes

Our mass grading scope begins with clearing, topsoil stripping and the survey control that every later trade will share. Grade stakes set from one benchmark avoid the small disagreements that turn into slab elevation problems months later. We stockpile topsoil separately from subsoil when the landscape plan calls for reuse, then cut and fill to the design surface in lifts the geotechnical engineer has approved, testing each lift before the next one goes down.

Where a parcel was developed before, the scope grows. Old pads, abandoned utilities and buried debris have to be sorted, tested for reuse and hauled out when they cannot stay. Building pads, pavement subgrades and detention basins carry different compaction and moisture requirements, so we mark those zones on the grading plan before equipment mobilizes. Fine grading and a final proof roll close the package. Where the site calls for it, we also coordinate with demolition so slabs and foundations are removed to a depth that suits the new design.

Soils reports, floodplain rules and county review

In unincorporated Boulder County the building official may ask for a soils or geologic report covering landslides, rock falls, flash flooding, subsidence or soil creep before a permit is issued, and the county floodplain rules in Section 4-400 of the Land Use Code win over conflicting building code provisions. We read the report before we price, because its recommendations on over-excavation, subgrade stabilization and drainage are the real earthwork scope.

The county's design criteria table lists a 30 inch frost line, but that figure appears in a residential table, so we confirm commercial values with the building official and the project geotechnical report instead of assuming them. Each town inside the metro runs its own grading and erosion review. We ask early what each one wants to see, and in Colorado disturbing an acre or more ordinarily brings a state construction stormwater permit and a written management plan, which we build into the schedule rather than treat as paperwork at the end.

Moisture, wind and the shape of the grading season

Boulder averages about 21 inches of precipitation a year, and Chinook winds can swing a cold week into a warm one with little warning. For earthwork that means frozen subgrade can thaw into soft, pumping ground in a few days, and a stripped site can dry into dust just as quickly. We schedule the highest-risk cuts for the windows when moisture can be managed, and we keep a water truck and a moisture-conditioning plan on the site, not on the wish list.

Sequence matters as much as season. We rough grade the whole site early enough that utilities, detention and building pads can start behind us, then return for fine grading once the underground work is in and backfilled. On phased projects we grade only what the first phase needs, stabilize the rest with seeding or mulch, and keep the later pads clean so that nobody pays to regrade ground that sat exposed for a year.

Where earthwork money goes

The biggest line in a grading budget is haul, and the best way to control it is to balance cut and fill on the site. A parcel in the 40 acre class, like the land the City of Longmont describes as available on the southwest side of Vance Brand Airport, shows why: across 40 acres, one inch of average depth is more than 5,000 cubic yards. A small change to finished floor elevation can swing the import and export numbers by a surprising amount, so we run alternatives with the civil engineer before the elevation is frozen.

Other drivers are less visible. Cobble and rock slow production, wet pockets need drying or stabilizing, and testing frequency adds cost where soil varies. Mobilization is repeated if the work is broken into several phases. We price these items separately, state the assumptions about soil conditions, and tell you which unknowns are worth a test pit before bidding. That makes a change order the exception, and it makes the bid easy to compare with anyone else's.

Dust, erosion control and the neighbors

Foothills wind is the first thing a grading crew notices and the last thing a neighbor forgives. We install perimeter controls, track-out pads and inlet protection before the first pass, keep haul routes swept, and water the site on schedule. Truck traffic is planned around the roads that serve the site, including the U.S. 36 corridor where it applies, so deliveries do not stack up at one entrance.

Equipment safety is more than a poster. Spotters work whenever trucks and people share ground, trench and slope edges are marked, and daily inspections of erosion controls are logged so the record is ready when a stormwater inspector asks. Owners of flex and light industrial buildings often move tenants in beside active earthwork on later phases, which is one more reason we treat dust and traffic control as design inputs rather than afterthoughts.

Talk through your site before the first pass

Send us the grading plan and the geotechnical report and we will walk the quantities, the haul balance and the schedule with you. Early input is when earthwork decisions cost the least.

Questions Owners Ask

Should we balance the site or plan on importing fill?

Balancing is usually cheaper, because every truckload you avoid is a cost you never pay. We run a quantity takeoff from the civil grading plan and test alternatives for finished floor elevation before the design is frozen. Importing makes sense when the native soil is too wet or too organic for a building pad, and the geotechnical report will tell you that. We show both options so the decision rests on numbers.

Do we need a geotechnical report before grading starts?

Yes, and in unincorporated Boulder County the building official can require a soils or geologic report for hazards such as flash flooding, subsidence or soil creep before a permit is issued. Even where it is not required, the report sets compaction targets, over-excavation depths and drainage recommendations that decide your earthwork price. We prefer to read it during preconstruction so the bid reflects it.

Can mass grading continue through winter?

Often it can, with limits. Frozen ground cannot be compacted to specification, so fill placement stops when the subgrade or the material is frozen. We shift to work that is not frost sensitive, such as clearing, rough cuts, stockpiling and haul-off, and then return to placing and testing fill when temperatures allow. Chinook warm-ups can reopen windows during the winter, and we watch them.

What happens if we find old foundations or debris on a previously developed parcel?

We stop in that area, document what we found with photographs and survey locations, and bring it to you and the engineer with a recommendation. Concrete can sometimes be crushed and reused as base, while contaminated or unsuitable material has to be tested and hauled. Having unit prices for unforeseen items in the bid keeps the conversation short.

Is grading priced as a lump sum or by the cubic yard?

Either works, and we explain the risk in each. A lump sum is simple when the geotechnical data is solid and the quantities are well defined. Unit prices for cut, fill, import and export make sense when soil conditions are uncertain, because you pay for what is moved. Many owners take a lump sum for the defined scope and unit prices for the unknowns.

Related

More General Contracting Services

Browse the rest of our general contracting services pages for Boulder and nearby Colorado communities, or contact us to talk through your project.