🚀 go-pugleaf

Metal Loading Rates From Groundwater at Hunters Point Shipyard
to San Francisco Bay, San Francisco, California

Barney  P. Popkin (Tetra Tech EM, Inc., 135 Main Street, Suite 1800,
San Francisco, CA 94105; 415- 222-8351; email popkinb@ttemi.com);
William S. Ng (Tetra Tech EMI, Inc.); Luann Tetirick (Engineering
Filed Activity-West, Naval Facilities Engineering Command, Department
of the Navy, 900 Commodore Drive, San Bruno, CA 94066-2402)

The U.S. Navy's Hunters Point Shipyard (HPS) is a 493-acre federal
Superfund site comprised of a 70-acre bedrock upland (Parcel A) and a
423-acre artificial fill lowland (Parcels B-E) adjacent to San Francisco
Bay's South Bay. As part of the Superfund remedial investigation/
feasibility process under the Navy's Comprehensive Long-Term
Environmental Action Navy program, we estimated current and future
projected, annual groundwater flow and mass metal loading rates from
A-aquifer groundwater to the Bay to help set priorities and make
decisions for groundwater remediation.

This paper summarizes and discusses these estimates. To account for the
variability in flow and loading mechanisms, annual groundwater flow
rates and mass loading rates are given as low, average, and high
estimates for current and future conditions. Flow rates and metal loading
rates are estimated from: (1) indirect groundwater discharge from inland
groundwater to leaky storm drains located below the water table because
HPS storm drains discharge directly to the bay, and (2) direct
groundwater discharge from nearshore groundwater to the shoreline of
the bay.

Our estimated loading rates account for: (1) flow through storm drains
and artificial fill (as well as shoreline concrete walls at drydocks, wooden
and rock seawalls, and iron sheetpiles), and (2) shoreline hydraulic
gradients which are influenced by leaky sanitary sewer lines located
below the water table to act as groundwater sinks. We estimated potential
bay dilution factors (BDF) for a mean tide in the South Bay as suggested
by the National Oceanic and Atmospheric Administration. We compared
our estimated metal loading rates to loading rates from HPS groundwater
background or ambient levels (HGAL), U.S. EPA National Ambient
Water Quality Criteria (NAWQC) for chronic saltwater aquatic life,
publicly owned treatment plants (POTW) and other bay-area discharge
sources as suggested by the California Regional Water Quality Control
Board.

Current average groundwater flow rates from storm drain and shoreline
groundwater from HPS to the bay are about 105 and 42.6 acre-feet per
year (ac-ft/yr), respectively, for a total of about 148 ac-ft/yr. Under
future conditions, it is assumed that leaky sanitary sewers and storm
drains will be repaired or replaced, so that the future projected average
flow rate from shoreline groundwater is about 65.2 ac-ft/yr; there is no
future projected storm drain groundwater flow. Current and future
projected metal loading rates from HPS groundwater flow to the bay are:
(1) very small compared to potential BDFs which range from several
million to over a billion, (2) several orders of magnitude lower than bay
discharges from POTWs and other bay-area sources, and (3) well below
both NAWQC and HGAL loading rates on a facility-wide basis and on a
parcel basis, except for copper, mercury, nickel, and silver.

Copper, mercury, nickel, and silver loading rates are generally slightly
higher than NAWQC loading rates but lower than HGAL loading rates;
one exception is the nickel loading rate in both storm drains and shoreline
groundwater flows from Parcel B under current conditions. At Parcel B,
average nickel loading rates: (1) exceed the NAWQC loading rate by
about 19 times and the HGAL loading rate by about 1.6 times from
storm drain groundwater flow under current conditions, and (2) exceed
the NAWQC loading rate by about 29 times and the HGAL loading rate
by about 2.4 times from shoreline groundwater flow under both current
and future conditions. On a facility-wide basis, most of the current,
estimated metal loading rates for copper, mercury, nickel, and silver are
contributed by storm drain groundwater flow, where Parcel B contributes
most of the nickel, Parcel D contributes most of the mercury, and Parcel
E contributes most of the copper and silver.

On a facility-wide basis and on a parcel basis, future projected metal
loading rates are well below both NAWQC and HGAL loading rates,
except for copper, mercury and nickel. On a facility-wide basis, copper
and mercury loading rates are slightly higher than NAWQC loading rates
and lower than HGAL loading rates; nickel loading rates are higher than
NAWQC loading rates and slighter lower than HGAL loading rates. On a
parcel basis, Parcel E shoreline groundwater contributes most of the
copper, mercury, and nickel under future projected conditions.
_______________________________________________________________________________

Extended abstract submitted to the Hydrology Session, American
Geophysical Union, 1997 Fall Meeting, December 8-12, 1997, San
Francisco, California on <www.agu.org> at 8:30 a.m. PST, September
3, 1997 by Barney P. Popkin.

-------------------------------------------------------------------------------
Sent via the Guardian Online.  415.437.3600 N81 or bbs.sfbayguardian.com, 3004
===============================================================================