Twelve field flows, in the order the lot is worked.

01

Job / building

What sits on the lot, and which Table 1 setbacks apply.

Job name, site address, town, designer or inspector, date, bedrooms, single-family vs. multi-family, footing drains (10 ft vs. 25 ft building setback), and water-treatment wastewater. WTW turns on Table 1 Item Q. This is the header every later sheet inherits.

02

Benchmark

One site BM. Every later grade is relative to it.

Benchmark elevation in feet. System bottom, original grade, and fill are stored against this mark so a section drawing can be rebuilt without re-shooting the lot.

03

Three test pits

Deep-hole log: mottling, groundwater, ledge.

Two upslope pits and the downslope observation. The most restrictive depth from the upslope pair is the default RS depth. Mottling, groundwater, and ledge are recorded as observed — the app does not interpret soil language for you.

04

Perc / MLSS

MLSS = HF × FF × PF. Appendix A, not a model.

Design percolation rate (min/in), Table 6 perc class / PF, and hydraulic gradient. Hydraulic factor from Appendix A. Flow factor is design flow ÷ 300. Percolation factor from the Table 6 class, with the select-fill footnote when it applies. The product is minimum leaching system spread, in feet.

05

Table 5 tank + Table 6 ELA

Tank volume and effective leaching area from the published tables.

Residential design flow from bedrooms and building type. Table 5 picks tank volume. Table 6 picks effective leaching area from perc class and flow. No curve-fitting. If the row is not in the table, the sheet does not invent one.

06

97 TS-listed products

TS-listed products ranked by legal fit, not by manufacturer.

The strip is the current Technical Standards list — 97 products at this writing. Rows are ordered by legal fit against the job: required ELA, MLSS, maximum row length, and the original-grade receiving window (product height vs. the section). Manufacturer is not a ranking factor. Unlisted products are not offered.

07

Section drawing

Original grade, fill, system bottom, restrictive layer.

A working section, not a sealed plan. It places the leaching system bottom against the restrictive layer and the vertical-separation rule, including the 24-inch coastal mottling case when that box is checked.

08

Fill pad

Select fill, reduced PF footnote, receiving window.

When the installation qualifies for the select-fill footnote, PF may be reduced per the Technical Standards — not by rule of thumb. Fill thickness and the receiving window are checked against the product selected in the strip.

09

Gravity vs. pump

Distribution method and the >25 gal/cycle dosing flag.

Gravity, pump, and intermittent dosing are recorded because they change how the leaching system is credited and how the section is drawn. Intermittent dosing greater than 25 gallons per cycle is a separate checkbox, not an inference.

10

NCR / B100a

Nonconforming lot worksheet. Not a B100a approval.

When a code-complying area cannot be shown, the NCR path documents the nonconforming geometry and the B100a exception questions. It does not issue the exception. The Director of Health still decides, and a PE still stamps when the code requires it.

11

PDF packet

Field packet with the same disclaimer on every page.

Job header, soil log, MLSS arithmetic with HF / FF / PF sources, Table 5 and Table 6 rows, product strip, elevations, and the calculation-aid disclaimer. Suitable to hand a sanitarian. Not a permit.

12

Device jobs / PWA

Jobs live on the device. The lot does not need cell service.

The calculator is a progressive web app. Jobs stay on the device so a perc test can be finished when the carrier cannot. The Vite / TanStack engine is mounted at /app.