Evidence base for a 150 dwelling site

At 150 dwellings the evidence base stops being a list of reports and becomes a programme. Two thresholds do most of the work: Active Travel England becomes a statutory consultee on major applications at or above 150 dwellings, and the urban development project category in Schedule 2 to the Environmental Impact Assessment Regulations uses "more than 150 dwellings" as one of its indicative triggers. Land at the edge of a settlement usually crosses the area limb of that same category long before the unit count matters.

So the first decision is not which consultants to appoint. It is whether this is EIA development, because that answer changes the determination period, the scoping process and roughly a year of programme.

Where screening actually bites at this scale

Schedule 2 category 10(b) covers urban development projects, with indicative thresholds of a site area exceeding 5 hectares, more than 150 dwellings, or new building floorspace over 10,000 m2. A scheme of exactly 150 homes does not exceed the dwelling figure. On a greenfield parcel of 6 or 7 hectares, which is the usual density for that number of houses outside a city, the area limb is crossed regardless.

Crossing a Schedule 2 threshold does not make a project EIA development. It makes screening necessary. The authority applies the selection criteria in Schedule 3, looking at the characteristics of the development, its location and the types of effect, and issues a screening opinion within 21 days unless it asks for more information.

Two practical points. A negative screening opinion costs less but is more fragile, because a third party can challenge the authority's reasoning rather than the development itself. And where a scheme sits in or near a sensitive area as defined in regulation 2, the indicative thresholds carry much less weight, so the designation check comes before the arithmetic. Request the screening opinion with a proper report rather than a letter, and attach the constraint plan.

Transport evidence and who has to be consulted

A Transport Assessment is the baseline at this scale, not a Transport Statement. Expect trip generation drawn from a recognised trip rate database with the site classification agreed in advance, junction capacity modelling at the accesses and the nearest signalised or priority junctions, a road safety review of recorded collisions, and an access design that the highway authority will adopt or approve.

Active Travel England's consultation role is about walking, cycling and wheeling provision rather than vehicle capacity, and it assesses the layout against national design guidance for cycle infrastructure. That changes what the drawings need to show. Internal street hierarchy, cycle parking quantum and location, direct links to existing routes rather than a path that stops at the red line, and crossing points on the desire line.

If the site touches or affects the strategic road network, National Highways is the consultee and its own circular on the strategic road network sets the approach. For the rest, the county or unitary highway authority and, where a travel plan is needed, a framework or full plan secured by obligation. The detail of when a Transport Assessment replaces a statement is covered in the piece on what a transport assessment trigger pulls in.

Landscape and visual work on a settlement edge

A 150 home scheme on the edge of a market town is a landscape case whether or not any designation applies. Commission a Landscape and Visual Impact Assessment prepared to the third edition of the Guidelines for Landscape and Visual Impact Assessment, with viewpoints agreed with the authority before the photography happens. Agreeing viewpoints late is the single most common cause of rework.

Where the parcel sits inside or within the setting of a National Landscape or National Park, the policy test tightens and the assessment has to address the statutory purposes of the designation rather than visual amenity alone. Zone of theoretical visibility plans, seasonal photography and a winter set are all worth the money here.

Ecology, biodiversity net gain and the survey calendar

Mandatory biodiversity net gain has applied to major development since 12 February 2024 under the Environment Act 2021. The scheme has to deliver at least a 10 per cent gain measured by the statutory metric, secured for 30 years, with a biodiversity gain plan approved by the authority after permission under the biodiversity gain condition.

The metric is the programme driver. Baseline habitat condition has to be assessed by a competent person in the growing season, which in practice means a Preliminary Ecological Appraisal early enough that the botanical survey lands between April and September. Protected species work follows from it, and those windows are narrow: bat emergence surveys between May and September, great crested newt eDNA between 15 April and 30 June, reptiles across April to October with the best results in spring and early autumn.

Biodiversity net gain assessment and protected species licensing both require a licensed or competent professional by law, and an AI-assisted draft of a Biodiversity Net Gain Assessment is a starting point for that person rather than a substitute for them. Miss a season and the application waits a year.

Flood risk, drainage and foul capacity

Any site of one hectare or more needs a Flood Risk Assessment regardless of flood zone, and a site in Flood Zone 2 or 3 needs one plus, in Zone 3, the sequential and exception tests as the policy requires. At 6 hectares of greenfield the surface water case is a greenfield run-off calculation, attenuation sized for the critical duration event with the current climate change allowance applied, and an exceedance route drawn on a plan.

Foul capacity is the quiet programme risk. Ask the sewerage undertaker for a capacity assessment early, because an upgrade to a pumping station or a length of rising main can take longer than the planning application and may need a Grampian condition. Where the catchment is subject to nutrient neutrality, the mitigation route has to be identified before determination, not after.

Heritage and archaeology on greenfield land

Open fields are where archaeology is most likely to be undisturbed. Commission an Archaeological Desk-Based Assessment against the Historic Environment Record held by the county archaeologist, then expect a request for geophysical survey and trial trenching before determination if the desk study flags potential. Field evaluation in advance is slower but gives a developable layout, whereas a condition requiring evaluation after permission can strand part of the site.

Built heritage at this scale is usually about setting rather than direct harm. Listed farmsteads, a conservation area boundary along an old lane, a registered park on the far side of a ridge. The assessment has to identify the assets, explain their significance and reach a view on harm, because the statutory and policy balance depends on that finding.

Social infrastructure, open space and the obligations package

Education contributions, healthcare, open space, play space and sports provision are all in play at 150 homes, and the county or unitary authority will produce formulae from its own adopted documents. An Affordable Housing Statement is needed from ten units upwards and a Statement of Community Involvement from fifty, so both are a given here.

The obligations package is negotiated, which means the viability evidence has to exist before the heads of terms are agreed rather than after. The article on what changes at the ten unit major threshold sets out the lower end of this ladder.

Programming the pack and the validation list

Work backwards from the determination date. A major application has a 13 week statutory period, 16 weeks if it is EIA development, and in practice an extension of time agreement on anything of this size. The surveys with fixed seasons set the start date, not the planning programme.

A realistic order of events: constraints and designation check, screening request, ecology appraisal and botanical survey in season, archaeology desk study, transport scoping with the highway authority and Active Travel England, drainage and foul capacity enquiries, then the design iteration that responds to all of it, then the narrative documents last so they describe the scheme that actually got drawn. Download the authority's local validation list at the start and again before submission, because they change. This is general guidance, not legal advice, and the authority's own checklist and national policy thresholds take precedence over any rule of thumb.

Enter your postcode on PlanScope to see which of the 66 report types a site of this scale is likely to need, then draft the narrative documents and send the technical ones for professional review.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. For specialist technical reports, qualified professional input may be required.