Soil Water and Groundwater Nitrate Data, North Ranch Bio-Recycling Facility Glenn Mutti-Driscoll, LHG April 9, 2018
Unsaturated Zone Transport Soil Nitrogen Pool ~4 year Unsaturated Zone Travel Time Regional Aquifer
Groundwater Flow Direction
Monitoring Locations and Recent Nitrate Concentrations
Soil Water and Groundwater Nitrate Concentrations
Groundwater Nitrate Concentrations Part II
Surface Water Nitrate Concentrations
Monitoring Locations and Recent Nitrate Concentrations
North Ranch Nitrate Summary Groundwater nitrate exceedances have historically occurred and continue to occur on property. Offsite groundwater nitrate concentrations are generally low and near background concentrations, suggesting that dilution is mitigating factor Offsite surface water concentrations are low, onsite concentrations can be elevated but generally infiltrate Groundwater nitrate concentrations expected to decrease in several years due to decreased surface loading and improved crop management Proposed storage impoundment should help improve groundwater nitrate concentrations since material is not being applied in winter when plants can’t take it up
Unsaturated Zone Transport Soil Nitrogen Pool ~4 year Clay Unsaturated Zone Travel Time Perched Water Tables Regional Aquifer
North Ranch Early Fall Soil Nitrate Data
In 2007 USGS sampled for 61 compounds common to domestic and industrial wastewater analyzed, including surfactants, food additives, fragrances, antioxidants, flame retardants, plastecizers, industrial solvents, disinfectants, fecal sterols, PAHs, and high-use domestic pesticides
2016 Soils Report No fields had greater than 30 mg/kg NO3-N, a level considered excessive. The reduced nitrogen application rate accomplished in 2015 and 2016 was clearly the correct response to excess soil nitrate evident in 2013 and 2014. Published guidance designates surface NO3-N above 30 mg/kg post fall harvest as excessive, between 20 and 30 as high, and between 10 and 20 mg/kg in the fall as medium. Soil nitrate levels below 20 mg/kg in 5 of 7 fields indicate treatment capacity higher than that application. Land Profile recommends an end-of-season goal of 20 mg/kg surface soil NO3-N. Soil nitrate peaked at excessive levels in 2013 (Field 3) and 2014 (Fields 1, 4, 10, 11), indicating excessive application and prompting reductions in application by Bio Recycling. On review of the agronomic rate calculation, Bio Recycling determined that higher than anticipated retention of ammonia from filtrate likely contributed to excessive soil nitrate levels.
2016 Soils Report In 2016, surface soil NO3-N trended lower for a second year, averaging 14.0 mg/kg compared to 24.5 mg/kg in 2015, 57.0 mg/kg in 2014, and 26.2 mg/kg in 2013. Surface soil NO3-N ranged from 4.5 to 25.0 mg/kg in 2016. Average subsoil NO3-N trended lower at 4.7 mg/kg and ranged from 2.0 to 8.8 mg/kg.
Outline Intro Licensed HG with PGG Presenting water quality monitoring data Soil to Regional Water table Surficial soil nitrogen pool After leaches goes through vadose zone, like conveyor belt generally Some clay perching layers present making flow occur both vertically and horizontally Takes ~4 yrs to hit Water Table (some uncertainty- USGS estimated 2-4 yrs from 3H/He samples, tried CFC, C14, and SF6 as well but inconclusive. Site loading review suggests 2-7 years, with a 4.1 yr avg) GW Flow Direction based on DTW measurements from 13 surveyed wells Travel time 5.5 to 9 yrs from MW-6 to Williams (some uncertainty in measured hydraulic parameters) 2016 Q4 Conc map- high at 1 and 4, also 5,6. Upgrad wells and offsite no exceedances 2 soil water lysimeters (tip at 24.5ft bgs). 2015 spike at L-1 likely reflects high mineralization rate in 2014 that did not spur plant uptake. 4 surface water monitoring locations, will be 2 additional under new permit
Outline 2 Sampling locations with elevated concentrations Monitor quarterly High variability. 1 & 4 typically exceed, 5 and 6 more variable and sometimes exceed. No other wells do. Some seasonality, with Q3 to Q4 GW peaks Most recent quarter has decrease in N at lysimeters, is consistent with decreases measured with soil sampling, presumably several years until the lower loading measurable at water table. Currently proposed approach should result in lower GW concentrations, mostly a matter of time until vadose zone flushed Low Concentration wells Upgradients and offsite domestics Plume appears be getting diluted prior to reaching nearby residential wells Surface water monitoring Never exceeded at wetlands on Webb Hill rd at SW-1(only 21% of site drains that way, also ¾ mile travel distance) SW-3 on property, no outlet SW-2A and SW-2B: seasonal ponds, generally just infiltrate down No SW contamination offsite As part of permit conditions, new locations SW-4 and SW-5 added
Proposed USGS Mason County Model Data Collection Wria 16 monitoring, maybe 14 as well
https://wa.water.usgs.gov/projects/masoncounty/maps.htm
Regional Model Applications Tool for understanding of groundwater flow paths and likely receptors at a regional scale Not typically focused on individual sites due to scale Focus on multiple aquifer systems and their interactions Generally have lower well densities than local models or compliance monitoring well networks (model cell sizes 500 feet to 3000 feet) Compiles and creates baseline data that act as a framework for local hydrogeologic evaluations Groundwater recharge Water balance and aquifer fluxes Regional groundwater flow directions in different aquifers Surface water-groundwater interactions Deep aquifer-shallow aquifer interactions
Soil Nitrogen Cycle
Global Nitrogen Cycle
Groundwater Flow Review From: https://water.usgs.gov/edu/watercyclegwdischarge.html
Remediation Nitrate is highly soluble and generally non-sorbing Generally impractical to implement wide-scale groundwater remediation techniques designed for point sources Best Management Practices (BMP) modification most common Cross Injection System (CIS) Enhanced denitrification is growing Generally requires large scale production wells
Remediation Remediation Best Management Practices Best Management Practices Modification of BMPs is the general approach, designed to limit loss of nutrients to the subsurface BMP modification problematic because: Bound N in soil Groundwater lags Difficulty of evaluating efficacy of BMPs Difficulty in enforcing implementation of BMPs Have been successful in the Malheur GWMA (Oregon) Based on local studies
Remediation Denitrification Substantial denitrification occurs in the unsaturated zone Denitrification converts nitrate (NO3-) to gaseous forms of N Requirements include oxygen-depleted conditions, a suitable electron donor, and microbes with the metabolic capacity for denitrification Suitable microbes are generally ubiquitous under agricultural land use. Oxygen-depleted conditions (< 2 mg/L dissolved oxygen) and the availability of electron donors. Electron donors include carbon, reduced inorganic iron, and reduced sulphur
Remediation Enhanced Denitrification Enhanced denitrification requires electron donors - acetate and hydrogen most effective Localized enhanced denitrification can be implemented around high flux zones around production wells (cross injection system)
Nitrogen Reduction Technologies Carbon Wall Anaerobic Digestors Septic Tank Retrofit Manure Export as Compost/fertilizer Drain Field Retrofit No-till Pump & Treat (aka irrigation) Lower fertilization after high N crops Slow release fertilizers Crop type Legumes in rotation Reduced N inputs/timed N Cover cropping in winter inputs (split applications) Manure lagoon liners Irrigation efficiency paired with nutrient application Manure application at efficiency agricultural rates
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