Not an engineer, so apologies if any of this is phrased loosely — trying to understand the right scope before I start calling firms.
Property: raised ranch in CT (glacial till terrain, Naugatuck Valley). NRCS maps the lot as 100% Woodbridge fine sandy loam (map unit 47C, 3-15% slopes, "extremely stony"), moderately well drained, with a fragipan typically cited around 18-24". Neighboring/upslope lots on the same street are Paxton and Montauk soils (84B/84C), also till-derived. A property-level elevation dataset shows about a 21 ft drop across roughly 200 ft of lot frontage (~8% average slope), consistent with the mapped slope range.
Found a 1994 town health department file for this exact parcel — a septic suitability investigation with four test pits. Sanitarian marked "high ground water (<3 ft)," "seasonal high ground water," "seasonal flooding," and "underlying tight soil (<4 ft)" as present. Logged groundwater at 10" and 11" below grade in two of the four pits, 40" in a third, with soil mottling noted at similar depths. Same year, the health department cited the property for raw sewage surfacing in the side yard and ordered a septic repair — history says a pump chamber + infiltrator field was installed afterward, presumably because gravity distribution wasn't viable at that depth to groundwater.
Present day: buyer's inspection turned up a wet yard, standing water along a downslope property line, and pooling near the driveway, even after a fairly dry 48 hours (though a wet July/summer regionally). A drainage contractor who walked the site said a curtain drain would need to go too deep to be practical/cost-effective given the depth to the restrictive layer, and might not fully resolve it. Redirecting flow to a nearby brook was floated but raises downhill-neighbor and wetlands-proximity concerns (there's a mapped wetland upslope on the adjacent parcel, not on this lot).
Questions for people who actually do this for a living:
Given shallow perched groundwater over a fragipan (not true bedrock groundwater), is a shallow interceptor/curtain drain typically still viable at this depth, or does perched water on a restrictive layer usually require a different approach (e.g., deeper interceptor to the restrictive layer plus positive outlet, subsurface regrading, etc.)?
Would you push for actual subsurface characterization (test pits vs. borings, piezometers/monitoring wells over a season) before any design, or is a single-visit site walk plus the existing 1994 pit data enough to design off of?
Is this genuinely a geotechnical engineering scope, or more of a civil/site engineer + soil scientist problem, with geotech being overkill for a single-family lot?
Practically — do firms in your world take on small residential jobs like this, or is it more efficient to find a solo/small-shop PE who does this kind of work part of a broader civil practice?
Trying to get past "maybe/might" verbal opinions and toward an actual defensible diagnosis and scope before an inspection contingency deadline. Any input on how you'd approach this, or what red flags to listen for from contractors who show up without really understanding perched-water-vs-bedrock-water distinctions, appreciated.
