HomeMy WebLinkAboutMINUTES - 06251996 - C12 TO: BOARD OF SUPERVISORS, AS THE GOVERNING BODY OF THE CONTRA COSTA
COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT
FROM: J. MICHAEL WALFORD, CHIEF ENGINEER
DATE: JUNE 25, 1996
SUBJECT: APPROVE JOINT EXERCISE OF POWERS AGREEMENT WITH THE CITY OF SAN
RAMON FOR SPECIAL PROJECT TO EVALUATE EFFECTIVENESS OF STORM-
WATER INTERCEPTOR FILTRATION SYSTEM
Project No. 0929-6X7049, SAN RAMON AREA
Specific Request(s)or Recommendation(s)&Background&Justification
1. Recommended Action:
APPROVE and AUTHORIZE a joint exercise of powers agreement with the City of San Ramon to
determine the effectiveness of stormwater interceptors in removing pollutants from commercial
parking lot runoff.
II. Financial Impact:
There will be no impact to General Fund. Joint exercise of powers agreement is funded with
stormwater utility fees collected by the Flood Control District on behalf of the nineteen (19)
municipalities in the Contra Costa Clean Water Program.
Continued on attachment: x SIGNATURE:
RECOMMENDATION OF COUNTY ADMINISTRATOR
RECOMMENDATION OF BOARD COMMITTEE
APPROVE OTHER
SIGNATURE(S):
ACTION OF BOARD ON: — 9 7 APPROVED AS RECOMMENDED +/ OTHER
VOTE OF SUPERVISORS
t/ UNANIMOUS (ABSENT )
AYES: NOES:
ABSENT: ABSTAIN:
ELG:sl
g:\F L DCTL\B O\sanram on.t5
Orig.Div.: Public Works (CCCWP)
Contact:Donald P. Freitas(510)313-2373
cc: County Administrator
Community Development
Building Inspection
County Counsel
County Assessor hwoyand oft b e bw and��copy o<
County Treasurer-Tax Collector an sown taken aid amend on ft nes o! q�
County Auditor-Collector 190W of411"76Chief Engineer ATTESTED
Accounting PHILBATCH o o<nnboom
Engineering Services 01S�Ieo�sAtoe
DeP�+h�
SUBJECT: JOINT EXERCISE OF POWERS AGREEMENT WITH THE CITY OF SAN RAMON FOR
SPECIAL PROJECT TO EVALUATE EFFECTIVENESS OF STORMWATER
INTERCEPTOR FILTRATION SYSTEM
Page -2-
111. Reasons for Recommendations and Background:
The San Francisco Bay Regional Water Quality Control Board requires the nineteen (19)
municipalities in the Contra Costa Clean Water Program conduct special studies to determine
the effectiveness of best management practices (BMPs) in removing pollutants from
stormwater runoff. Runoff from commercial parking lots has proven to be an important source
of pollutants. As part of their municipal stormwater permit, municipalities are constantly
seeking effective BMPs that remove these pollutants in a cost efficient manner.
The City of San Ramon will contract with a water quality technical services consultant to
conduct this study. The stormwater interceptors will be installed to collect the runoff from two
large commercial parking lots in the City of San Ramon. The consultant will determine the
amount of pollutants accumulated in the interceptor unit, develop unit maintenance
procedures and perform a cost benefit analysis. A written report will be available for the
municipalities in the Contra Costa Clean Water Program. All nineteen (19) municipalities in
the Contra Costa Clean Water Program will jointly fund this study through this agreement
between the City of San Ramon and the Flood Control District.
IV. Consequences of Negative Action:
The San Francisco Regional Water Quality Control Board may find the Contra Costa Clean
Water Program is not conducting special studies as required in its Municipal NPDES
Stormwater Permit. The Regional Board has the authority to fine municipalities in the Contra
Costa Clean Water Program up to $10,000 per day and $10 per gallon of discharge for non-
compliance with the permit.
By: CITY OF SAN RAMON
Chair, Board of Supervisors
ATTEST:
Phil Batchelor, Clerk of the Board
of Supervisors and County By:
Administrator Mayo f
RECOMMENDED FOR APPROVAL ATTEST: �G1 a "erk
J. Michael Walford, Chief Engineer
By:
By: RECOMMENDED FOR APPROVAL
Deputy Chief Engineer
By:
ity Manag
FORM APPROVED:
Victor J. Westman, County Counsel
By:
By: FORM APPR VED:
Deputy , City Attorney
By:
GWJ:js
(:lenglcantract�epacla.t6
April 22,1996
EXHIBIT A
SAN RAMON STORMWATER INTERCEPTOR STUDY
The Scope of Work for the Agreement includes the following from the San Ramon Stormwater
Interceptor Proposal prepared by Woodward-Clyde, dated May 12, 1995:
1. Section 2.3 Accumulation of Pollutants Inside the Interceptor Unit
Tasks 3.1, 3.2, 3.3 $32,000
2. Section 2.4 Maintenance
Tasks 4.1 and 4.2 $11,000
3. Section 2.5 Cost/Benefit Analysis
Tasks 5.1, 5.2, 5.3 $ 7,000
Total $50,000
SANRAMON
STORMWATER
INTERCEPTOR STUDY
Prepared for
Contra Costa
Clean Water Program
255 Glacier Drive
Martinez, CA 94553
May 12, 1995
Prepared by
Woodward-Clyde Consultants
500 12th St, Suite 100
Oakland, California 94607-4014
91C04130/2100
91\25153.1(91 C0413 D)\I M0524951201
TABLE OF CONTENTS
Section Page
1.0 INTRODUCTION 1-1
2.0 POTENTIAL STUDY COMPONENTS 2-1
2.1 Effectiveness of Pollutant Removal from Storm Water 2-1
2.2 Storm Event Performance: Percentage of Storm Captured 2-3
2.3 Accumulation of Pollutants Inside the Interceptor Unit
2.4 Maintenance Requirements 2-7
2.5 Cost/Benefit Analysis 2-8
3.0 SUMMARY OF BUDGETS 3-1
1:\91125171.1(91 C0413DAii 11 M05 1295 1 5 17
1.0
INTRODUCTION
Recently, Jensen stormwater interceptors have been installed to treat stormwater in two
parking lots in San Ramon, with storm drains that provides for a bypass when flows exceed
the design flows of the unit. Implementation of a new Best Management Practice (BMP)
requires a followup study to evaluate the performance and the cost-effectiveness of that
technology and to maintain the efficiency of the units. The questions associated with the
Jensen stormwater interceptor are related to several aspects of this BMP. Performance
questions may include: How does water quality improve, or what is the percentage of
reduction in concentrations, of pollutants found in parking lot runoff? What percentage of
the total load is the unit capturing?
Due to the immense variability in stormwater pollution features such as flows, concentrations,
and loads, in many situations it is hard to show that a BMP is actually removing pollutants
from the water, but it is still possible to show that the BMP is preventing a certain amount
of pollutants from reaching the Bay. The latter approach would focus on questions that are
related to the accumulation and fate of pollutants inside the interceptor chambers: How fast
do sediments accumulate? What quantities of pollutants can we remove from our drainage
area by dredging the sediments from the unit? When does the unit lose its capacity to collect
more sediments? How many storms, or how much time, does it take for the floating pads to
be saturated with hydrocarbons? Are the pads losing hydrocarbons to degradation by
microorganisms? Does the unit present an odor problem during hot days?
The information about sediment and pollutant accumulation is needed to devise adequate
maintenance practices, to answer questions such as: How often do the chambers need to be
dredged? At what frequency should the floating pads be replaced? And, once the
maintenance activities are defined, we need to address questions of cost, such as: How many
dollars will it take to intercept one pound of copper? One pound of petroleum hydrocarbons?
Is the unit more cost effective than other BMPs?
1A91\25170.1(91 C0413D)kl i-l MOS 12951512
This document divides the questions listed above into five study components that may be
approached separately, some of which are totally independent and others are interrelated. The
approach, requirements, assumptions, and costs are delineated for each component.
JA91\25170.1(91 CO413 D)\2 1-2 M05 1295 15 12
coprJOINT EXERCISE OF POWERS AGREEMENT
BETWEEN CONTRA COSTA COUNTY FLOOD CONTROL
AND WATER CONSERVATION DISTRICT
AND CITY OF SAN RAMON
Special Project to Remove Pollutants
from Commercial Parking Lot Stormwater Runoff
1, Parties:
Effective the CONTRA COSTA COUNTY FLOOD
CONTROL AND WATER CONSERVATION DISTRICT, a body, corporate and
politic, hereinafter referred as "DISTRICT," and the CITY OF SAN RAMON, a
municipal corporation, hereinafter referred as "CITY," pursuant to Government Code
Section 6500 and following, mutually agree and promise as follows:
2. Purpose and Scope of Work:
CITY is conducting a special study project, hereinafter referred as "PROJECT", to
measure the effectiveness of filtration systems in removing pollutants from
commercial parking lot stormwater runoff. The study was approved by the nineteen
municipalities of the Contra Costa Clean Water Program, which includes seventeen
cities, Contra Costa County and the DISTRICT, and will be funded by stormwater
utility assessments levied by the DISTRICT. The purpose of this Agreement is to
apportion PROJECT duties and costs between CITY and DISTRICT.
3. Methods:
CITY shall perform the following activities:
a. Act as lead agency and comply with all environmental requirements pursuant
to California Environmental Quality Act.
b. Obtain all necessary permits for PROJECT.
C. Retain a qualified consultant approved by DISTRICT to conduct PROJECT.
d. Perform all necessary supervision and contract administration to ensure that
the PROJECT work complies with this Agreement.
e. Maintain PROJECT records and document project expenses.
f. Bill DISTRICT for PROJECT tasks described in Exhibit "A" which is
incorporated here by this reference.
g. Prepare and deliver to DISTRICT a written report of all receipts and
disbursements.
DISTRICT shall perform the following activities:
a. Act as a responsible agency pursuant to California Environmental Quality
Act.
b. Consult with CITY, as necessary, to enable PROJECT work to be properly
completed.
C. Reimburse CITY for the PROJECT tasks described in Exhibit "A".
4. Changes in Project Work:
The PROJECT work shall comply with acceptable engineering practices and shall
include all of the tasks set forth in Exhibit"A". Any changes in the PROJECT work
shall require the prior, written approval of DISTRICT.
5. Financial Responsibilities:
DISTRICT shall reimburse CITY for all costs of the PROJECT work, including
reasonable compensation for necessary review and contract administration
performed by CITY, as well as all costs of any changes or extra work requested or
approved in writing by DISTRICT. PROJECT task breakdown and the maximum
costs that DISTRICT shall pay for the entire PROJECT are set forth in attached
Exhibit "A".
6. Insurance and Hold Harmless:
a. The contract documents for PROJECT shall include provisions requiring the
consultant to: (1) obtain and maintain in full force and effect during the
PROJECT work, workers'compensation, public liability and property damage
insurance, in forms and limits of liability satisfactory to CITY and DISTRICT,
naming CITY and DISTRICT, their governing bodies, officers and employees
as additional insureds; and (2) promise to defend, indemnify, save and hold
harmless DISTRICT, its governing body, officers and employees from liability
to the same extent as promised to CITY. The aforementioned policy shall
contain an endorsement that the insurance afforded thereby to the additional
insureds shall be primary insurance to the full limits of the policy, and that if
any of the additional insureds have other insurance or self insurance against
a loss covered by such policy, such insurance or self insurance shall be
excess insurance only. Before beginning the PROJECT work, the_co.nsultant
shall submit to CITY and DISTRICT a certificate of insurance evidencing the
required coverages and requiring the carrier to give at least 30 days written
notice to CITY and DISTRICT of any cancellation, non-renewal or material
modification of the policy. CITY shall be responsible for ensuring that this
requirement has been met before allowing the PROJECT work to proceed.
b. Neither DISTRICT, nor any officer or employee thereof, shall be responsible
for any damage or liability occurring by reason of anything done or omitted
to be done by CITY in connection with any work delegated to CITY under
this AGREEMENT, and CITY shall defend, indemnify, save and hold
harmless DISTRICT, its governing body, officers and employees from the
same.
C. Nothing in this AGREEMENT is intended or shall be construed to affect the
legal liability of either party to third parties by imposing any standard of care
greater than that imposed by law.
7. Restrictions:
Pursuant to Government Code Section 6509, the powers of the parties under this
AGREEMENT shall be subject to the restrictions on such powers applicable to
CITY.
8. Agreement Modification:
This AGREEMENT shall be subject to modification only with the prior, written
consent of CITY and DISTRICT. Neither party shall unreasonably withhold its
consent to the implementation and accomplishment of the overall purpose for which
this AGREEMENT is drawn.
9. Aqreement Expiration:
This AGREEMENT shall expire upon delivery of the report of receipts and
disbursements and payment of all funds specified herein, or on January 1, 1998
except for the provisions of Section 6 which shall survive expiration of this
AGREEMENT.
CONTRA COSTA COUNTY CONSERVATION DISTRICT
FLOOD CONTROL AND WATER
2.0
POTENTIAL STUDY COMPONENTS
2.1 Effectiveness of Pollutant Removal from Storm Water
uestion: What are the concentrations of metals (copper, lead, and zinc), total suspended
solids (TSS), total petroleum hydrocarbons (TPI), and-Oil & Grease (O&G); in the water
entering and exiting the interceptor during the initial part of a given storm event?
L2oach:
• (Task 1.1) Collect 10 grab samples at each end of the unit (intake and exit) during
the first 7 volume-replacements in the interceptor, starting immediately after runoff
is seen flowing in. Measure or estimate the flow rate to determine the time intervals
of sampling: The residence time, i.e. the time required for one volume replacement,
is based upon the flow rate and the total capacity of the unit. Assuming residence time
of 10 minutes, grabs should be taken at 8-9 minutes intervals for about 90 minutes of
runoff flow.
• (Task 1.2) Analyze for the above water quality parameters, using EPA methods with
detection limits that will allow detection of change in the concentrations of these
parameters. Implement a quality assurance and quality control (QA/QC) plan
throughout sampling and analysis activities.
Sampling of two events, preferably at the beginning of the rainy season or when the
interceptor is clean, will give a good indication if reduction in concentrations is
detectable.
• (Task 1.3) Compare the pollutographs generated for data obtained before and after the
interceptor unit. Statistical analyses of the data will be limited to simple comparisons
of concentrations or slopes for the two units and for two events; the data will not
allow detection of seasonal or spatial trends.
1:\91\25170.1(91C0413D)\1 2-1 M0512951512
Cost: (Based on two locations and two storm events):
Task Description Estimated Cost
1.1 Two persons (staff) will need to wait for the rain at each $6,400
station and spend several hours sampling and dispatching
samples to laboratories, for each storm. Additional time must
be added for "false starts".
1.1 Budget for other direct costs (e.g., vehicle, Water Quality kit, $800
sample shipment).
1.2 Analysis of 22 samples at about $300 per sample for each $26,400
station-event (Total of 80 samples plus 8 QA/QC samples
such as equipment blank).
1.2 One person with expertise in chemical analysis (e.g. Assistant $2,000
Project Scientist) will need to spend 20 hours communicating
with labs and reviewing QA/QC results.
1.3 Data interpretation and reporting will require about 40 hours, $4,400
depending on the requested format of the report.
TOTAL for Component # 1 $40,000
($10,000 per
station-event)
Requirements: Safe and rapid access to the intake pipe and the outflow pipe of each unit.
Assumptions: sampling equipment is available at no further cost. Weather forecast services
are available from the Flood Control District.
1:\91\25170.1(91C 0413 0)U 2-2 M0523951029
2.2 Storm Event Performance: Percentage of Storm Captured
Questions: What percentage of the total flow passes through the interceptor at a given storm
intensity (inches per unit time)? What portion of the total pollutant load is the unit
intercepting?
Approach:
• (Task 2.1) Throughout the runoff flow period, measure volumes (by means of flow
meters) going through the interceptor and volumes bypassing the unit.
• (Task 2.1) Record turbidity at intake and outflow throughout the event.
• (Task 2.1) Collect 10 grab samples spaced as evenly as possible throughout the event,
to generate a pollutograph of the entire event (Assumption: the concentrations of
pollutants will decrease with time and may increase slightly at the tail end of runoff).
• (Task 2.2) Analyze the samples for metals (copper, lead, and zinc), TSS, TPH, and
Oil & Grease
Information from a rain gage nearby (or a gage installed temporarily for the project
at the edge of the parking lot) will be valuable in correlating rainfall intensity to
percent capture. Review of historical rainfall records will help making general
conclusions about percent capture.
• (Task 2.3) Using this data in conjunction with pollutant data from Component # 1,
the proportion of pollutant load removed by the interceptor can be estimated.
I A91\25170.1(91 C0413 D)U 2-3 M05 1295 1 5 12
Cost: (Based on two stations and two storm events):
Task Description Estimated Cost
2.1 Two persons will need to wait for the storm at each station $8,000
and spend the storm duration (e.g., 6 hours) sampling and
measuring flows and turbidity. Expenses for other direct
costs and budget for "false start" should be added.
2.2 Analysis of 40 samples + 4 QA/QC samples at about $300 $13,200
per sample
2.3 QA/QC and interpretation of water quality data, analysis of $6,800
hydrological data, and reporting, will require about 60 hours.
TOTAL for Component # 2 $28,000
($7,000 per
station-event)
Requirements: Safe and rapid access to the intake pipe, the bypass pipe, and the outflow pipe
of each unit.
Assumptions: flow meter suitable for tracking flow in culverts is available at no further cost.
Rainfall intensity information is available at no further cost.
NOTE: In the absence of component # 1, this component cannot be completed without
water quality data at the outlet of the ineterceptor. Field activities for component # 2 could
be combined with the sampling activities of Component # 1, but one more person may be
needed during the first hour of runoff.
IA91\25170.1(91C0417D)\4 2-4 N105 1295 15 12
2.3 Accumulation of Pollutants Inside the Interceptor Unit
Questions: What sort of materials are trapped in the unit (Garbage, leaf litter, sand, silts)?
How does sediment thickness, or volume, increase with time? How can we tell if the floating
absorbent pads are accumulating hydrocarbons or are saturated with hydrocarbons? What is
the concentration of parking-lot pollutants in the sediment? What quantities or loads of
pollutants does this BMP prevent from reaching the Bay?
Approach:
• (Task 3.1) Measure the thickness of the organic "ooze" layer (if present) and the sand
layer at various locations within the three cells of the interceptor every month (or in
relation to storm events) over the rainy season and every two months during dry
weather for one year. Methodology for these measurements already exists. Record
visual observations and odors related to the unit.
• (Task 3.1) Evaluate sediment quantity at the point in time when sediments need to
be removed, and collect 2 sediment samples in each chamber of the interceptor at that
point.
• (Task 3.1) Develop methods to monitor saturation of pads with hydrocarbons and
monitor the pads at similar frequency. Collect 2 pad samples in each chamber.
• (Task 3.2) Analyze sediments for metals (copper, lead, and zinc), total petroleum
hydrocarbons (TPH), total organic carbon (TOC), and percent moisture. Analyze the
absorbent pads for TPH, Oil & Grease, and percent moisture.
• (Task 3.3) Evaluate disposal options based on sediment quality analytical results.
Estimate total weight of sediment to be removed, based on estimated volumes and
density.
• (Task 3.3) Calculate the amounts of pollutants removed by.this BMP, based on total
weight of sediments that can be dredged out of the interceptor chambers and the
I A9 R25170.1(91 C04 13 D)l5 2-5 M05 1295 15 12
specific concentrations of pollutants in these sediment. Conduct similar calculations
for the absorbent pads.
Cost: (Based on two locations)
Task Description Estimated Cost
3.1 At each location, two persons will spend 36 hours per year $19,400
each, performing observations and measurements. One
person will need to spend 60 hours to develop methods of
assessing the status of absorbent pads and obtaining samples
for TPH and 0&G analyses. Two persons will need 16 hours -
each, to collect sediment samples.
3.2 Analyze 16 sediment samples ($280 per sample) and 8 $7,200
absorbent pad samples ($200 per sample), using EPA
methods and allowing for determination of matrix effects
with 4 additional samples.
3.3 One person will need to spend 50 hours performing QA/QC, $5,400
data interpretation, evaluation of disposal options,
calculations of loads removed by the unit, and reporting
TOTAL for Component # 3 $32,000.
($16,000 per
location)
Requirements: Safe access to the various corners of each chambers, using a Tank Sampler
and other equipment mounted on long pole.
Assumptions: Equipment for assessment of absorbent pads will be available.
IA91\25170.1(91C0413D)\6 2-6 M05 L2951512
2.4 Maintenance Requirements
uestions: How can the unit be maintained so that "self-cleaning" is avoided? What
"markers" can be used to assess the need for prompt cleaning? What are the best methods to
clean the interceptor chambers? Where can the sediment be disposed of?
Approach:
• (Task 4.1) Based on information collected in component # 3, develop a list of criteria
to define what triggers cleaning operations, i.e. thickness of sediment and/or
hydrocarbon saturation of absorbent pads.
• (Task 4.1) Determine if sediment dredging operations requires emptying of unit, while
testing various methods to remove sediments.
• (Task 4.1) Determine sediment disposal practice.
• (Task 4.2) Develop guidance for maintenance personnel.
Cost:
Task Description Estimated Cost
4.1 One person will need to spend 60 hours in field and office to $7,000
develop criteria, select cleaning procedures, and determine
disposal practices. Field activities will require a second
person.
4.2 One person will need 40 hours for guidance development. $4,000
TOTAL for Component # 4 $11,000
Additional options: Conducting training sessions to City personnel. This will require more
time.
1.N91125170.1(91 00413 D)17 2-7 M0512951512
2.5 CostlBenefit Analysis
uestions: How many pounds of various pollutants are removed by the Jensen Intercepter
for a given investment in dollars? How does this estimate of cost-effectiveness compare with
other treatment-type BMPs, such as street sweeping, catch basin cleaning, or detention basins?
Approach:
• (Task 5.1) Compile Cost Information and Estimate Annual Amortized Costs: Compile
information on capital and maintenance costs including land purchase costs, site
preparation, equipment costs, installation costs, and maintenance costs, including
inspection, cleaning, and disposal of materials. Amortize capital and O&M costs on
annual basis for expected life of facility, for a range of discount rates.
• (Task 5.2) Estimate Annual Pollutant Removal Performance: If data from component
# 1 and # 2 are available, estimate average annual pollutants removed by Jensen
Interceptors based on flow and water quality data collected. Take into account, to
extent possible, rainfall statistics, effects of first flush, flow bypassing, and
performance as it may vary with storm event size. If data from component # 3 are
availabe, estimate the amount of pollutants associated with sediments and absorbent
pads that were removed and disposed of.
• (Task 5.3) Estimate Cost Effectiveness and Compare with other BMPs: Based on
Tasks 5.1 and 5.2, estimate cost effectiveness of units in terms of amount in pounds
of water quality constituents removed for a given annual investment (e.g. pounds
removed per $1000 dollar investment). Conduct brief literature search for cost
effectiveness information for other BMPs and compare with Jensen Interceptor.
IA91\25170.1(9I C0413D)\8 2-8 M0312951512
Cost:
Task Description Estimated Cost
5.1 14 hours to compile data and perform calculations. $1,200
5.2 30 hours to anayze rainfall, runoff, water quality data, $3,000
sediment quantity and quality data, and absorbent pad data.
5.3- 28 hours to conduct literature review, make comparisons, $2,800
and report.
TOTAL for Component # 5 $7,000
I191\25170.1(91C0417D)\9 2-9 M0512951512
3.0
SUMMARY OF BUDGETS
Comp- Subject Estimated Cost
Y Per event Total
or location
1 Evaluating the effect of interceptor in decreasing $10,000 per $40,000
pollutant concentrations during initial phase of station-event
storm
2 Measuring the percentage of storm water $7,000 per $28,000
captured by the interceptor throughout the storm station-event
event and assessing the quality of the water at
the inlet throughout the event
3 Monitoring the accumulation of pollutants inside $16,000 per $32,000
the interceptor unit throughout the seasons and location
estimating the quantities of pollutants that can be
removed by cleaning the unit
4 Developing maintenance criteria and $11,000
requirements
5 Cost/Benefit Analysis $7;000
General Assumptions: Budgets are estimated for labor performed by consultants, and may
decrease if field tasks are supported by in-kind participation of City or County personnel.
All sampling and analysis activites will be according to a comprehensive quality assurance
and quality control (QA/QC) plan.
IA91\25170.1(91C0413D)\1 3-1 M0512951512
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HIGH VELOCITY 5TORMWATER INTERCEPTOR
mwmrw MODEL JPHV-4000
PRECAST Since 1968
24'CAST IRON FRAME
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FRAME a GRATE RETAINER Note:
OPTIONAL CORD S RING
P1,P2,and P3 are
AS REQUIRED TMPJ supplied by others.
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SIZE T I NORMAL
2417 I I 4824• 60"
SIDE VIEW VAR. I I BAfRE P2
OPENINGS
CUTAWAY 1 I I St
NOTE: PIPE SIZES(Pt-P3)',BAFFLE OPENINGS(Std S2) PZ Note:
AND OUTLET BOX,SHALL BE SIZED ACCORDING TO FLOW. 30" � Recormtended mink
MIN. rnu rms.Uquld levei,8"
NOT TO SCALE Note: above P2 for water trap
1� Absorbent plilows to be equipped with retaining sac an equivalent Cross
ton1
OPTIONAL se
ring and cord, cured to or under risme end °c �l area of P3.
O
PILLOW cover for hand access by others-Consult
LOCATION Jensen Precast for Instaltarion details.
\ 16'-T l
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II �
I L-J I I I
OUTLET
I II II I
I f Box l
Pt ! i t I I I P2 ) P3
T-8' I I 48' I I 4-. -
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1 TOP VIEW H I l I T
I COVERS REMOVED I I I I
1-------- -----J L--------------- I----------------� 72'
CAPACITY RECOMENDED RECOMENDED TOTAL
WrrH 11' TOTAL APPROX. RECOMENDED RECOMENDED OUTLET BOX MIN.NO.OF ACCESS
MODEL NOMINAL TANK GAL.PER PIPE SIZE OUTLET BOX SIZE ABSORBENT COVERS
NUMBER AIR SPACE CAPACITY VERT.INCH "P' SIZE RANGE PILLOWS REQUIRED
JPHV-4000 4000 4761 69.976 B'TO 18' 60'Round 60'Round-4'x 4' 10 4
DESIGN LOAD: H-20 TRAFFIC FROM V TO 5'COVER. FOR OTHER DEPTHS,SPECIAL LOADINGS,
AND COMPLETE DESIGN INFORMATION,CONSULT JENSEN PRECAST.
WARNING: THIS INTERCEPTOR IS A CONFINED SPACE. ATMOSPHERE MAY BE HAZARDOUS.
DO NOT ENTER WITHOUT PROPER EQUIPMENT. FOLLOW O.S.H.A. CONFINED
SPACE ENTRY PROCEDURES BEFORE ENTERING.
Jensen Precast JPHV Stormwater Interceptors have no warranties,expressed or implied,for
merchantablity of fitness for any particular purpose or application.
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JOINT EXERCISE OF POWERS AGREEMENT
r
BETWEEN CONTRA COSTA COUNTY FLOOD CONTROL
AND WATER CONSERVATION DISTRICT
AND CITY OF SAN RAMON
Special Project to Remove Pollutants
from Commercial Parking Lot Stormwater Runoff
1. Parties:
Effective , the CONTRA COSTA COUNTY FLOOD
CONTROL AND WATER CONSERVATION DISTRICT, a body, corporate and
politic, hereinafter referred as "DISTRICT," and the CITY OF SAN RAMON, a
municipal corporation, hereinafter referred as"CITY,"pursuant to Government Code
Section 6500 and following, mutually agree and promise as follows:
2. Purpose and Scope of Work:
CITY is conducting a special study project, hereinafter referred as "PROJECT", to
measure the effectiveness of filtration systems in removing pollutants from
commercial parking lot stormwater runoff. The study was approved by the nineteen
municipalities of the Contra Costa Clean Water Program, which includes seventeen
cities, Contra Costa County and the DISTRICT, and will be funded by stormwater
utility assessments levied by the DISTRICT. The purpose of this Agreement is to
apportion PROJECT duties and costs between CITY and DISTRICT.
3. Methods:
CITY shall perform the following activities:
a. Act as lead agency and comply with all environmental requirements pursuant
to California Environmental Quality Act.
b. Obtain all necessary permits for PROJECT.
C. Retain a qualified consultant approved by DISTRICT to conduct PROJECT.
d. Perform all necessary supervision and contract administration to ensure that
the PROJECT work complies with this Agreement.
e. Maintain PROJECT records and document project expenses.
f. Bill DISTRICT for PROJECT tasks described in Exhibit "A" which is
incorporated here by this reference.
shall submit to CITY and DISTRICT a certificate of insurance evidencing the
required coverages and requiring the carrier to give at least 30 days written
notice to CITY and DISTRICT of any cancellation, non-renewal or material
modification of the policy. CITY shall be responsible for ensuring that this
requirement has been met before allowing the PROJECT work to proceed.
b. Neither DISTRICT, nor any officer or employee thereof, shall be responsible
for any damage or liability occurring by reason of anything done or omitted
to be done by CITY in connection with any work delegated to CITY under
this AGREEMENT, and CITY shall defend, indemnify, save and hold
harmless DISTRICT, its governing body, officers and employees from the
same.
C. Nothing in this AGREEMENT is intended or shall be construed to affect the
legal liability of either party to third parties by imposing any standard of care
greater than that imposed by law.
7. Restrictions:
Pursuant to Government Code Section 6509, the powers of the parties under this
AGREEMENT shall be subject to the restrictions on such powers applicable to
CITY.
8. Agreement Modification:
This AGREEMENT shall be subject to modification only with the prior, written
consent of CITY and DISTRICT. Neither party shall unreasonably withhold its
consent to the implementation and accomplishment of the overall purpose for which
this AGREEMENT is drawn.
9. Agreement Expiration:
This AGREEMENT shall expire upon delivery of the report of receipts and
disbursements and payment of all funds specified herein, or on January 1, 1998
except for the provisions of Section 6 which shall survive expiration of this
AGREEMENT.
CONTRA COSTA COUNTY CONSERVATION DISTRICT
FLOOD CONTROL AND WATER
By: _ CITY OF SAN RAMON
Chair, o r a upervisors
ATTEST:
Phil Batchelor, C16r7k of the Board `
of Supervisors and County By: Z'zjk'ema'01
Administrator Mayor
RECOMMENDED FOR APPROVAL ATTEST: ludq MACF,412LA.&LF-City Clerk
J. Michael Walford, Chief Engineer
By:
By: RE MMENDED FOR A PROVAL
Deputy Chief Engineer
By:
City Mana r
FORM APPROVED:
Victor J. Westman, County Counsel
f By:
By: ` ✓ �\/ FORM APP VED:
Deputy , City Attorney
By:
GWJ:js
Meng\contracl\j epacla.l6
April 22,1996
EXHIBIT A
SAN RAMON STORMWATER INTERCEPTOR STUDY
The Scope of Work for the Agreement includes the following from the San Ramon Stormwater
Interceptor Proposal prepared by Woodward-Clyde, dated May 12, 1995:
1. Section 2.3 Accumulation of Pollutants Inside the Interceptor Unit
Tasks 3.1, 3.2, 3.3 $32,000
2. Section 2.4 Maintenance
Tasks 4.1 and 4.2 $11,000
3. Section 2.5 Cost/Benefit Analysis
Tasks 5.1, 5.2, 5.3 $ 7,000
Total $50,000
■ ■ ■ ■ ■ ■ ■ SAN RAMON
STORMWATER
INTERCEPTOR STUDY
Prepared for
Contra Costa
Clean Water Program
255 Glacier Drive
Martinez, CA 94553
May 12, 1995 -
Prepared by
Woodward-Clyde
Woodward-Clyde Consultants
500 12th St, Suite 100
Oakland, California 94607-4014
91 C0413DI2100
IA91125153.1(9l C0413DA 1 M0524951201
TABLE OF CONTENTS
Section Page
1.0 INTRODUCTION 1-1
2.0 POTENTIAL STUDY COMPONENTS 2-1
2.1 Effectiveness of Pollutant Removal from Storm Water 2-1
2.2 Storm Event Performance: Percentage of Storm Captured 2-3
2.3 Accumulation of Pollutants Inside the Interceptor Unit 2-5
2.4 Maintenance Requirements 2-7
2.5 Cost/Benefit Analysis 2-8
3.0 SUMMARY OF BUDGETS 3-1
IA91\25171.1(91C0413D)\ii 11 M05 1295 15 17
1.0
INTRODUCTION
Recently, Jensen stormwater interceptors have been installed to treat stormwater in two
parking lots in San Ramon, with storm drains that provides for a bypass when flows exceed
the design flows of the unit. Implementation of a new Best Management Practice (BMP)
requires a foliowup study to evaluate the performance and the cost-effectiveness of that
technology and to maintain the efficiency of the units. The questions associated with the
Jensen stormwater interceptor are related to several aspects of this BMP. Performance
questions may include: How does water quality improve, or what is the percentage of
reduction in concentrations, of pollutants found in parking lot runoff? What percentage of
the total load is the unit capturing?
Due to the immense variability in stormwater pollution features such as flows, concentrations,
and loads, in many situations it is hard to show that a BMP is actually removing pollutants
from the water, but it is still possible to show that the BMP is preventing a certain amount
of pollutants from reaching the Bay. The latter approach would focus on questions that are
related to the accumulation and fate of pollutants inside the interceptor chambers: How fast
do sediments accumulate? What quantities of pollutants can we remove from our drainage
area by dredging the sediments from the unit? When does the unit lose its capacity to collect
more sediments? How many storms, or how much time, does it take for the floating pads to
be saturated with hydrocarbons? Are the pads losing hydrocarbons to degradation by
microorganisms? Does the unit present an odor problem during hot days?
The information about sediment and pollutant accumulation is needed to devise adequate
maintenance practices, to answer questions such as: How often do the chambers need to be
dredged? At what frequency should the floating pads be replaced? And, once the
maintenance activities are defined, we need to address questions of cost, such as: How many
dollars will it take to intercept one pound of copper? One pound of petroleum hydrocarbons?
Is the unit more cost effective than other BMPs?
1A91\25170.1(91C04131))\1 1-1 M0512951512
This document divides the questions listed above into five study components that may be
approached separately, some of which are totally independent and others are interrelated. The
approach, requirements, assumptions, and costs are delineated for each component.
IA91\25170.1(91C0413D)\2 1-2 M05 1 295 15 1 2
2.0
POTENTIAL STUDY COMPONENTS
2.1 Effectiveness of Pollutant Removal from Storm Water
Question: What are the concentrations of metals (copper, lead, and zinc), total suspended
solids (TSS), total petroleum hydrocarbons (TPH), and-Oil & Grease-(O&G), in the water
entering and exiting the interceptor during the initial part of a given storm event?
Approach:
• (Task 1.1) Collect 10 grab samples at each end of the unit (intake and exit) during
the first 7 volume-replacements in the interceptor, starting immediately after runoff
is seen flowing in. Measure or estimate the flow rate to determine the time intervals
of sampling. The residence time, i.e. the time required for one volume replacement,
is based upon the flow rate and the total capacity of the unit. Assuming residence time
of 10 minutes, grabs should be taken at 8-9 minutes intervals for about 90 minutes of
runoff flow.
• (Task 1.2) Analyze for the above water quality parameters, using EPA methods with
detection limits that will allow detection of change in the concentrations of these
parameters. Implement a quality assurance and quality control (QA/QC) plan
throughout sampling and analysis activities.
Sampling of two events, preferably at the beginning of the rainy season or when the
interceptor is clean, will give a good indication if reduction in concentrations is
detectable.
• (Task 1.3) Compare the pollutographs generated for data obtained before and after the
interceptor unit. Statistical analyses of the data will be limited to simple comparisons
of concentrations or slopes for the two units and for two events; the data will not
allow detection of seasonal or spatial trends.
IA91\25170.1(91C0413D)\1 2-1 M0512951512
Cost: (Based on two locations and two storm events):
Task Description Estimated Cost
1.1 Two persons (staff) will need to wait for the rain at each $6,400
station and spend several hours sampling and dispatching
samples to laboratories, for each storm. Additional time must
be added for "false starts".
1.1 Budget for other direct costs (e.g., vehicle, Water Quality kit, $800
sample shipment).
1.2 Analysis of 22 samples at about $300 per sample for each $26,400
station-event (Total of 80 samples plus 8 QA/QC samples
such as equipment blank).
1.2 One person with expertise in chemical analysis (e.g. Assistant $2,000
Project Scientist) will need to spend 20 hours communicating
with labs and reviewing QA/QC results.
1.3 Data interpretation and reporting will require about 40 hours, $4,400
depending on the requested format of the report.
TOTAL for Component # 1 $40,000
($10,000 per
station-event)
Requirements: Safe and rapid access to the intake pipe and the outflow pipe of each unit.
Assumptions: sampling equipment is available at no further cost. Weather forecast services
are available from the Flood Control District.
IA91\25170.1(91C0413D)12 2-2 M0523951029
2.2 Storm Event Performance: Percentage of Storm Captured
Questions: What percentage of the total flow passes through the interceptor at a given storm
intensity (inches per unit time)? What portion of the total pollutant load is the unit
intercepting?
Approach:
• (Task 2.1) Throughout the runoff flow period, measure volumes (by means of flow
meters) going through the interceptor and volumes bypassing the unit.
• (Task 2.1) Record turbidity at intake and outflow throughout the event.
• (Task 2.1) Collect 10 grab samples spaced as evenly as possible throughout the event,
to generate a pollutograph of the entire event (Assumption: the concentrations of
pollutants will decrease with time and may increase slightly at the tail end of runoff).
• (Task 2.2) Analyze the samples for metals (copper, lead, and zinc), TSS, TPH, and
Oil & Grease
Information from a rain gage nearby (or a gage installed temporarily for the project
at the edge of the parking lot) will be valuable in correlating rainfall intensity to
percent capture. Review of historical rainfall records will help making general
conclusions about percent capture.
• (Task 2.3) Using this data in conjunction with pollutant data from Component # 1,
the proportion of pollutant load removed by the interceptor can be estimated.
IA91\25170.1(91 C0413D)l3 2-3 M05 1295 15 12
Cost: (Based on two stations and two storm events):
Task Description Estimated Cost
2.1 Two persons will need to wait for the storm at each station $8,000
and spend the storm duration (e.g., 6 hours) sampling and
measuring flows and turbidity. Expenses for other direct
costs and budget for "false start" should be added.
2.2 Analysis of 40 samples + 4 QA/QC samples at about $300 $13,200
per sample
2.3 QA/QC and interpretation of water quality data, analysis of $6,800
hydrological data, and reporting, will require about 60 hours.
TOTAL for Component # 2 $28,000
($7,000 per
station-event)
Requirements: Safe and rapid access to the intake pipe, the bypass pipe, and the outflow pipe
of each unit.
Assumptions: flow meter suitable for tracking flow in culverts is available at no further cost.
Rainfall intensity information is available at no further cost.
NOTE: In the absence of component # 1, this component cannot be completed without
water quality data at the outlet of the ineterceptor. Field activities for component # 2 could
be combined with the sampling activities of Component # 1, but one more person may be
needed during the first hour of runoff.
1A91\25170.1(91C0413M4 2-4 M0512951512
2.3 Accumulation of Pollutants Inside the Interceptor Unit
Questions: What sort of materials are trapped in the unit (Garbage, leaf litter, sand, silts)?
How does sediment thickness, or volume, increase with time? How can we tell if the floating
absorbent pads are accumulating hydrocarbons or are saturated with hydrocarbons? What is
the concentration of parking-lot pollutants in the sediment? What quantities or loads of
pollutants does this BMP prevent from reaching the Bay?
Approach:
• (Task 3.1) Measure the thickness of the organic "ooze" layer (if present) and the sand
layer at various locations within the three cells of the interceptor every month (or in
relation to storm events) over the rainy season and every two months during dry
weather for one year. Methodology for these measurements already exists. Record
visual observations and odors related to the unit.
• (Task 3.1) Evaluate sediment quantity at the point in time when sediments need to
be removed, and collect 2 sediment samples in each chamber of the interceptor at that
point.
• (Task 3.1) Develop methods to monitor saturation of pads with hydrocarbons and
monitor the pads at similar frequency. Collect 2 pad samples in each chamber.
• (Task 3.2) Analyze sediments for metals (copper, lead, and zinc), total petroleum
hydrocarbons (TPH), total organic carbon (TOC), and percent moisture. Analyze the
absorbent pads for TPH, Oil & Grease, and percent moisture.
• (Task 3.3) Evaluate disposal options based on sediment quality analytical results.
Estimate total weight of sediment to be removed, based on estimated volumes and
density.
• (Task 3.3) Calculate the amounts of pollutants removed by this BMP, based on total
weight of sediments that can be dredged out of the interceptor chambers and the
1A91\.25170.1(91 C0413D)\5 2-5 M0512951512
specific concentrations of pollutants in these sediment. Conduct similar calculations
for the absorbent pads.
Cost: ,(Based on two locations)
Task Description Estimated Cost
3.1 At each location, two persons will spend 36 hours per year $19,400
each, performing observations and measurements. One
person will need to spend 60 hours to develop methods of
assessing the status of absorbent pads and obtaining samples
for TPH and O&G analyses. Two persons will need 16 hours
each, to collect sediment samples.
3.2 Analyze 16 sediment samples ($280 per sample) and 8 $7,200
absorbent pad samples ($200 per sample), using EPA
methods and allowing for determination of matrix effects
with 4 additional samples.
3.3 One person will need to spend 50 hours performing QA/QC, $5,400
data interpretation, evaluation of disposal options,
calculations of loads removed by the unit, and reporting
TOTAL for Component # 3 $32,000
($16,000 per
location)
Requirements: Safe access to the various corners of each chambers, using a Tank Sampler
and other equipment mounted on long pole.
Assumptions: Equipment for assessment of absorbent pads will be available.
IA91\25170.1(91C0413D)\6 2-6 M0512951512
2.4 Maintenance Requirements
Questions: How can the unit be maintained so that "self-cleaning" is avoided? What
"markers" can be used to assess the need for prompt cleaning? What are the best methods to
clean the interceptor chambers? Where can the sediment be disposed of?
Approach:
• (Task 4.1) Based on information collected in component# 3, develop a list of criteria
to define what triggers cleaning operations, i.e. thickness of sediment and/or
hydrocarbon saturation of absorbent pads.
• (Task 4.1)Determine if sediment dredging operations requires emptying of unit, while
testing various methods to remove sediments.
• (Task 4.1) Determine sediment disposal practice.
• (Task 4.2) Develop guidance for maintenance personnel.
Cost:
Task Description Estimated Cost
4.1 One person will need to spend 60 hours in field and office to $7,000
develop criteria, select cleaning procedures, and determine
disposal practices. Field activities will require a second
person.
4.2 One person willneed 40 hours for guidance development. $4,000
TOTAL for Component # 4 $11,000
Additional options: Conducting training sessions to City personnel. This will require more
time.
IA9 1\25170.1(9 1 C0413D)\7 2-7 M05 1295 15 12
2.5 Cost/Benefit Analysis
Questions: How many pounds of various pollutants are removed by the Jensen Intercepter
for a given investment in dollars? How does this estimate of cost-effectiveness compare with
other treatment-type BMPs, such as street sweeping,catch basin cleaning, or detention basins?
Approach:
• (Task 5.1) Compile Cost Information and Estimate Annual Amortized Costs: Compile
information on capital and maintenance costs including land purchase costs, site
preparation, equipment costs, installation costs, and maintenance costs, including
inspection, cleaning, and disposal of materials. Amortize capital and O&M costs on
annual basis for expected life of facility, for a range of discount rates.
• (Task 5.2) Estimate Annual Pollutant Removal Performance: If data from component
# 1 and # 2 are available, estimate average annual pollutants removed by Jensen
Interceptors based on flow and water quality data collected. Take into account, to
extent possible, rainfall statistics, effects of first flush, flow bypassing, and
performance as it may vary with storm event size. If data from component # 3 are
availabe, estimate the amount of pollutants associated with sediments and absorbent
pads that were removed and disposed of.
• (Task 5.3) Estimate Cost Effectiveness and Compare with other BMPs: Based on
Tasks 5.1 and 5.2, estimate cost effectiveness of units in terms of amount in pounds
of water quality constituents removed for a given annual investment (e.g. pounds
removed per $1000 dollar investment). Conduct brief literature search for-cost
effectiveness information for other BMPs and compare with Jensen Interceptor.'
IA91125170.1(91 C0413D)X8 2-8 M0512951512
Cost:
Task Description Estimated Cost
5.1 14 hours to compile data and perform calculations. $1,200
5.2 30 hours to anayze rainfall, runoff, water quality data, $3,000
sediment quantity and quality data, and absorbent pad data.
5.3- 28 hours to conduct literature review, make comparisons, $2,800
and report.
TOTAL for Component # 5 $7,000
IA91\25170.1(91 C0413D)l9 2-9 M05 1295 15 1 2
3.0
SUMMARY OF BUDGETS
Comp. Subject Estimated Cost
Per event Total
or location
1 Evaluating the effect of interceptor in decreasing $10,000 per $40,000
pollutant concentrations during initial phase of station-event
storm
2 Measuring the percentage of storm water $7,000 per $28,000
captured by the interceptor throughout the storm station-event
event and assessing the quality of the water at
the inlet throughout the event
3 Monitoring the accumulation of pollutants inside $16,000 per, $32,000
the interceptor unit throughout the seasons and location
estimating the quantities of pollutants that can be
removed by cleaning the unit
4 Developing maintenance criteria and $11,000
requirements
5 Cost/Benefit Analysis $7,000
General Assumptions: Budgets are estimated for labor performed by consultants, and may
decrease if field tasks are supported by in-kind participation of City or County personnel.
All sampling and analysis activites will be according to a comprehensive quality assurance
and quality control (QA/QC) plan.
IA9 1\25170.1(9 1 C0413D)\I 3-1 M0512951512
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! ` HIGH VELOCITY SeTORMMATER IWERCEPTOIT
MODEL JPHV-4000
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�- 24"CAST IRON FRAME
d COVER STANDARD
FRAME d GRATETl�- RETAINER
OPTIONAL Note:
CORD S RINGTYP P1 P2,and P3 are
AS REQUIRED
supplied by others.
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SIDE VIEW VAR. I I BAFFLE P2
OPENINGS
CUTAWAY S1
NOTE: PIPE SIZES(Pi-P3),BAFFLE OPENINGS(Std S2) P2 Note:
AND OUTLET BOX,SHALL BE SIZED ACCORDING TO FLOW. 30' Recommended min{-
MIN. mums.Liquid level,r
NOT TO SCALE above P2 for water trap
Note: wlth an equivalent cross
Absorbent pillows to be equipped with retaining sectional area of P3.
OPTIONAL ring and cord,secured to or under trame and
PILLOW cover for hand access by others.Consult
LOCATION —� Jensen Precast for Installation detalls.
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16'.7-
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COVERS REMOVED-----J L---------------I I----------------
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CAPACITY RECOMENDED RECOMENDED TOTAL
WITH 11' TOTAL APPROX. RECOMENDED RECOMENDED OUTLET BOX MIN.NO.OF ACCESS
MODEL NOMINAL TANK GAL.PER PIPE SIZE OUTLET BOX SIZE ABSORBENT COVERS
NUMBER AIR SPACE CAPACITY VERT.INCH 7' SIZE RANGE PILLOWS REOUIRED
JPHV-4000 4000 4761 69.976 8'TO 18' 60'Round 60'Round-4'x 4' 10 4
DESIGN LOAD: H-20 TRAFFIC FROM V TO 5'COVER. FOR OTHER DEPTHS,SPECIAL LOADINGS,
AND COMPLETE DESIGN INFORMATION,CONSULT JENSEN PRECAST.
WARNING: THIS INTERCEPTOR IS A CONFINED SPACE. ATMOSPHERE MAY BE HAZARDOUS.
DO NOT ENTER WITHOUT PROPER EQUIPMENT. FOLLOW O.S.H.A. CONFINED
SPACE ENTRY PROCEDURES BEFORE ENTERING.
Jensen Precast JPHV Stormwater Interceptors have no warranties,expressed or implied,for
merchantabiity of fitness for any particular purpose or application.
nn