The development process

A quarter section of dry cropland on the edge of a city looks simple from the road. It is flat, it has a view of the coulee, and a highway runs past it. Turning it into a neighborhood of a few hundred homes takes years of work by planners, engineers, surveyors, lawyers, lenders and council, and a geomatics engineer sits close to the center of that work. The surveyor defines the land at the start, measures the ground the designers rely on, lays out the lots and roads, stakes them for construction and, at the end, prepares the plan that creates the new parcels in law. This course follows one project from first sketch to registered plat and uses it to teach the design and approval skills that land development needs.

The project is Coulee Ridge, a 60.8-acre parcel on the east edge of Great Falls, Montana, where the prairie breaks into a steep coulee above the river. Prairie Hearth Communities, a regional developer, has an option to buy the land. Its development manager, Dana Whitford, has asked Coulee Geomatics for a feasibility study before she commits. Ruth Albrecht, the firm's principal and a licensed land surveyor, will run the job with Leah Tran on design and GIS, Theo Martel on computations and code, and Grant Okonkwo leading the field crew. Sunil Mehta of Brightwater Engineering will design the roads and pipes, and Claire Fontaine, the city's subdivision planner, will review everything that comes in.

What land development is

Land development is the process of converting land from one use to another, here from agriculture to housing, and of creating the legal parcels, public roads, utilities and open space that the new use needs. It joins three kinds of work. The planning work decides what may be built and where, through the city's plans and zoning. The engineering work designs how the land will drain, how traffic will move and how water, sewer and power will reach each lot. The legal and survey work creates new titles that can be sold, mortgaged and insured.

Each kind of work constrains the others. A road layout that looks efficient on paper may need a sewer too deep to build. A lot pattern that meets the zoning may leave a pond with nowhere to drain. A grading plan that balances cut and fill may push water onto a neighbor. Good subdivision design is the search for a layout that satisfies all of these at once and still makes money, and that search is the subject of this course.

The people involved

The developer owns or controls the land, takes the financial risk and makes the final business decisions. Lenders finance the work and watch the budget and the sales pace. The municipality approves the plans, takes over the roads, pipes and parks when they are finished, and maintains them for decades, so its standards are written with long-term cost in mind. Utility companies for power, gas and telecommunications design their own networks in coordination with the engineer.

The consultants carry out the design. Planners prepare the concept and the planning applications. Civil engineers design grading, roads, stormwater, water and sewer. Geotechnical engineers advise on soils, slope stability and groundwater, which matter a great deal beside a coulee. Environmental consultants assess wetlands, wildlife and contamination. Landscape architects design parks and streetscapes. The land surveyor provides the base survey, the legal boundaries, the plan of subdivision and the construction staking, and is often the first consultant on site and the last to leave.

The stages of a project

Every jurisdiction has its own procedure, but the sequence is broadly similar. It starts with due diligence: title searches, a review of planning documents, a look at existing services and a first estimate of how many lots the land might yield. If the numbers work, the land is bought or optioned and the planning stage begins. In a Montana city, the land must be covered by the city's land use plan and zoning before a subdivision application can go forward. A pre-application meeting with the city follows, where the planner explains what the application must include.

The subdivision application itself is supported by a tentative layout, technical studies and an engineering concept. After review, the approving authority approves it with conditions, refuses it or asks for changes. The conditions are then met: the developer signs an improvements agreement, builds the roads and utilities or posts a bond guaranteeing them, and the state's sanitation review is completed. Finally the surveyor prepares the final plat, which is approved by the governing body and filed with the county clerk and recorder, and the new lots legally exist.

The timeline is long. A neighborhood of a few hundred lots may take two to five years from concept to first sales, and longer if planning documents must be amended or a market downturn intervenes. Most of the developer's money is spent before any lot is sold, which is why the financial analysis in lesson 11 and lesson 12 matters so much.

Phasing

Large subdivisions are built in phases so that the developer does not have to finance all the roads and pipes at once. Each phase must work on its own: it needs a complete road connection, a sewer outlet, a water loop that meets fire flow, and drainage to a pond that is already built or temporary. The order of phases is usually set by the trunk services. At Coulee Ridge the sanitary sewer leaves the site at the west boundary, so phase 1 starts there and later phases march east toward the coulee.

Phasing affects the surveyor directly. Each phase gets its own final plat, its own construction staking and its own set of monuments. Remainder parcels between phases must be described clearly, and the overall boundary and control network must be designed so that later phases fit the earlier ones without gaps or overlaps.

The surveyor's work across the project

It helps to list the survey tasks in order, because they recur in almost every lesson. At the start come the title search and the boundary survey, which confirm what land the developer is actually buying and what rights of way and caveats or easements cross it. Next is the topographic survey, combining GNSS and total station work with an airborne lidar terrain model, on a control network that will serve the whole project. During design the surveyor checks the layout geometry, computes lot dimensions and areas and confirms that the plat will close. During construction the crew stakes the roads, pipes and lots, measures quantities for progress payments and records as-built locations. At the end the surveyor places the legal monuments and prepares and certifies the final plat. No other consultant touches the project so often.

Gross and net areas

Not all of the land becomes lots. A first estimate of yield starts from the gross area and subtracts land that cannot be built on, which gives the net developable area. Steep coulee slopes and drainage ways are typically kept as open space, and the park dedication is calculated on the area in lots. From the net area come the dedications for parks, the roads, the stormwater pond and walkways. What is left is divided into lots.

Road area depends on the street pattern and lot depth, but for a typical suburban layout local roads take about a fifth to a quarter of the net area. Lots are never perfectly regular, because of corners, curves and the edges of the site, so a layout loss of several percent is subtracted before dividing by the typical lot size. Theo's script below produces the first estimate that Dana will use to decide whether the land is worth buying.

# Coulee Ridge: first gross-to-net yield estimate (areas in acres)
gross = 60.8           # area being subdivided
slope = 7.2            # coulee slope and setback kept as open space
net = gross - slope    # net developable area
pond = 3.6             # stormwater detention pond
walk = 0.4             # trails and utility corridors
streets = 0.23 * net   # local streets at about 23 percent of net area
rest = net - pond - walk - streets
# park dedication: 11 % of the area in lots of half an acre or less,
# so park = 0.11 * lots and lots + park = rest
lots_area = rest / 1.11
park = 0.11 * lots_area
lot = 44 * 110 / 43560             # typical lot, 44 ft x 110 ft, in acres
layout_loss = 0.08                 # corner, curve and odd-shaped lots
n_lots = int(lots_area * (1 - layout_loss) / lot)
print(f"net developable area      {net:6.2f} ac")
print(f"park dedication (11 %)    {park:6.2f} ac")
print(f"streets                   {streets:6.2f} ac")
print(f"area left for lots        {lots_area:6.2f} ac ({lots_area / gross:.0%} of gross)")
print(f"typical lot               {lot * 43560:6.0f} ft2")
print(f"estimated lots            {n_lots:6d}")
print(f"density                   {n_lots / net:6.1f} units per net acre")
for target in (7, 9):
    print(f"lots needed for {target} u/ac     {round(target * net):6d}")

net developable area       53.60 ac
park dedication (11 %)      3.69 ac
streets                    12.33 ac
area left for lots         33.58 ac (55% of gross)
typical lot                 4840 ft2
estimated lots               278
density                      5.2 units per net acre
lots needed for 7 u/ac        375
lots needed for 9 u/ac        482

The estimate gives about 278 lots on 53.6 net acres, or 5.2 units per net acre. Roughly half of the gross area ends up in lots, which is normal for a suburban subdivision with a large natural area. Claire tells Ruth that the city's growth policy encourages a mix of housing types; the course uses 7 units per net acre as an illustrative target, which would need about 375 units. Meeting that would mean adding townhouses or narrower lots, a question the layout work in lesson 4 returns to.

Constraints and opportunities

Before any layout is drawn, the team lists what the land offers and what it forbids. At Coulee Ridge the opportunities are the view, the trail potential along the top of bank and a gentle slope toward the west that suits gravity drainage. The constraints are the coulee itself, where slopes exceed 15 percent and slope stability is a concern, an existing gas pipeline right of way crossing the north edge, a gravel road on the south boundary that will need upgrading, and the irrigation district's lateral, whose right of way and drainage rights must be respected. Lesson 3 turns this list into maps.

A good feasibility study also flags the unknowns. Ruth's list includes the depth to groundwater near the coulee, whether the city's trunk sewer has capacity, and whether the state archaeology database records any sites. Each unknown carries a risk to cost or schedule, and the developer needs to know about them before buying.

Coulee Geomatics: the feasibility memo

Ruth's memo to Dana sets out the yield estimate, the land budget, a first look at the approvals path and a list of studies needed: a topographic survey and lidar-based terrain model, a geotechnical report on the coulee setback, a biophysical assessment of the slopes, a servicing study by Brightwater and a traffic impact assessment. It estimates that the first lots could be sold about two and a half years after the land is bought. Dana takes the memo to her board, which approves the purchase, and the work of the following lessons begins.